The Brazilian Herbicide Journal is an Online Journal (ISSN 2236-1065), formerly Printed (from 2000 to 2005) ISSN 1517-9443, edited by the Brazilian Weed Science Society (SBCPD), and aimed at publishing technical-scientific articles and review articles in the field of weed science and related issues. Currently this journal is quarterly published and its Qualis concept is B4. The Brazilian Herbicide Journal is registered at CAPES and SEER and has its articles indexed at Sumários.org and Latindex database. AGRIS (International Information System for the Agricultural Sciences and Technology) and CAB Abstracts are in progress. Articles submitted to the Brazilian Herbicide Journal should be original and relevant to the field.
Sociedade Brasileira da Ciência das Plantas Daninhas
Ambrosia sp.: dose-response to glyphosate
Background: Farmers have reported difficulty in controlling Ambrosia sp., observing uncontrolled plants in soybean fields even after post-emergence glyphosate application Objective: The aim of this study was to evaluate the response of Ambrosia sp. to different rates of the herbicide glyphosate. Methods: The experiment was conducted in duplicate in a greenhouse at the Federal University of Santa Catarina, Curitibanos campus, between September and December 2022, using a completely randomized design with four replications. The treatments consisted of the application of nine increasing rates of the herbicide glyphosate (0; 93.75; 187.5; 375; 750; 1500; 3000; 6000; 12000 g ae ha-1) when the Ambrosia sp. plants had between 4 to 8 true leaves. The following parameters were evaluated: height; percentage of control; and final above-ground dry matter mass. Results: The results indicated growth inhibition, resulting in reduced height for rates starting from 1500 g ae ha-1 in Ambrosia sp. The evaluation of final above-ground dry matter mass showed a reduction between 73 and 95%, depending on the dose applied. Conclusions: Even the high rates used were not able to achieve excellent control (>90%) of the species.
Copyright (c) 2026 Brazilian Herbicide Journal
SELETIVIDADE E EFICÁCIA DE HERBICIDAS APLICADOS EM TRIGO COM TECNOLOGIA CLEARFIELD®
O controle de plantas daninhas em trigo é feito com uso herbicidas pela eficácia, praticidade e menor custo em comparação com outros métodos. Porém quando esses produtos não são seletivos, podem causar impactos diretos e indiretos no crescimento e desenvolvimento da cultura. Diante disso, objetivou-se com o trabalho avaliar a seletividade e eficácia de herbicidas inibidores de ALS aplicados na cultivar de trigo TBio Ello com tecnologia Clearfield®. O experimento foi conduzido a campo em delineamento de blocos casualizados, com quatro repetições. Os tratamentos foram constituídos por duas testemunhas, capinada e outra infestada, e pelos herbicidas: imazapic+imazapyr, imazethapyr+imazapic, imazethapyr, cloransulam-methyl, nicosulfuron, imazamox, ethoxysulfuron, bispyribac-Na e penoxsulam. As avaliações de fitotoxicidade e o controle das plantas daninhas foram efetuadas aos 7, 14, 21, 28 e 35 dias após a aplicação dos tratamentos (DAT). As características fisiológicas foram avaliadas aos 21 DAT. Na colheita determinou-se os componentes de rendimento de grãos. O nicosulfuron apresentou a maior fitotoxicidade ao trigo e consequentemente a menor produtividade de grãos. A testemunha capinada e os herbicidas imazethapyr + imazapic, imazethapyr, cloransulan-methyl, imazapic + imazapyr e o bispyribac-Na apresentam o melhor desempenho fisiológico. O imazethapyr+imazapic, imazethapyr, cloransulam-methyl, ethoxysulfuron e o penoxsulam demonstraram as menores fitotoxicidades ao trigo. Os herbicidas não apresentaram eficácia adequada ao azévem, porém o contrário ocorreu para o nabo, onde obteve-se 100% de controle. A produtividade de grãos foi diretamente influenciada pelo nível de controle das plantas daninhas, sendo a testemunha capinada o melhor tratamento e dentre os herbicidas o imazethapyr+imazapic se destacou
WEED CONTROL AND FITOSOCIOLOGY IN CASSAVA CULTIVATION DUE TO PRE-EMERGENT HERBICIDES AND THEIR INFLUENCE ON ROOT QUALITY
Background: Cassava (Manihot esculenta) is native to Brazil, widely cultivated across the country, and is the third largest source of food in the Brazilian tropical regions. Weeding is commonly used for weed control in cassava, which can be substituted by herbicides. Objective: To evaluate the weed control, phytosociology, yield, and sensory analysis of cassava treated with pre-emergent herbicides. Methods: Two field experiments were conducted, with a randomized block design and four replications. The treatments consisted of the herbicides s-metolachlor, metribuzin, and clomazone applied after the planting of cassava cuttings, with additional weeding and weed-infested controls. The evaluation included weed control and phytosociology, plant height, number of leaves, and cassava yield. The roots were peeled and subjected to sensory evaluation using a multiple comparison discriminative test. Results: The herbicides were effective in controlling most of the weeds, affecting at phytosociology during cassava growth. Richardia brasiliensis was the most important weed specie when using clomazone and metribuzin. A significant improve in cassava yield was obtained when pré-emergent was applied, likewise at sensory root quality. Conclusions: There is a difference in the control spectrum among herbicides, which leads to variations in the phytosociology of weed species. The importance value index for Richardia brasiliensis was higher for clomazone and metribuzin. The number of leaves per plant, plant height, cassava yield, and quality were greater in the herbicide-treated and weeding treatments compared to the untreated control.
Association of pre-emergent herbicides with plant cover in weed management
Background: The species Bidens pilosa, Euphorbia heterophylla, and Amaranthus hybridus have shown high interference in soybean cultivation, especially due to biotypes resistant to various herbicides. Objective: This study aimed to analyze the effectiveness of soil cover associated with pre-emergence herbicides in managing these species Methods: Separate experiments were conducted for each weed species in a completely randomized design with a 4 × 4 factorial scheme and three replications. The evaluated factors were chemical management (diclosulam, flumioxazin, sulfentrazone, and an untreated control) and cover crop species (Canavalia ensiformis, Pennisetum glaucum, Crotalaria juncea, and a control without cover). At 35 days after treatment application, weed control percentage and aerial dry biomass were assessed. Results: A. hybridus was satisfactorily controlled (>80%) by soil cover alone, regardless of herbicide use. The lowest control was observed with P. glaucum; however, when combined with herbicides, control reached approximately 100%. For B. pilosa, cover crop species alone provided nearly 90% control, with even greater efficacy in some herbicide associations. In contrast, for E. heterophylla, neither cover crops nor herbicides alone were effective. Flumioxazin provided only 26.7% control, whereas sulfentrazone reached 82.7%. Conclusions: Effective control of this species required the combination of herbicides and cover crops. The results indicate that, depending on the weed species, specific interactions between soil cover and herbicides enhance weed suppression.
PERFORMANCE OF HERBICIDE MIXTURES AND SEQUENTIAL TREATMENTS FOR BENGHAL DAYFLOWER MANAGEMENT
Background: Benghal dayflower is a widely distributed weed in Brazil, known for its tolerance to glyphosate, requiring the use of alternative herbicides and more complex control strategies. Objective: Evaluate different auxin-mimicking herbicides in combination with glyphosate for the control of Benghal dayflower, as well as the efficacy of glufosinate alone or in association with PPO inhibitors in sequential applications. Methods: Two experiments were conducted in Ponta Grossa (PR-Brazil), using a randomized block design. The first experiment evaluated different auxinic herbicides combined with glyphosate, including 2,4-D, triclopyr, halauxifen, fluroxypyr, and dicamba. Additionally, treatments with glyphosate alone and a non-treated control were assessed. The second experiment evaluated Benghal dayflower control with glyphosate + 2,4-D followed by sequential glufosinate applications alone or with PPO inhibitors saflufenacil, tiafenacil, carfentrazone, and flumioxazin. In both experiments, visual evaluations of weed control percentage relative to the untreated control were performed. Results: All treatments combining glyphosate with auxin-mimicking herbicides showed statistically significant improvements compared to glyphosate alone, with the 2,4-D + glyphosate mixture standing out. The addition of PPO inhibitors did not improve Benghal dayflower control compared to glufosinate alone. However, sequential applications enhanced control, achieving an average of approximately 93% compared to only 75% in the non-sequential treatment. Conclusions: The use of auxinic herbicides in mixture with glyphosate, mainly 2,4-D, in the burndown application and sequential treatment of glufosinate alone or combined with PPO inhibitors are strategies that enhance Benghal dayflower control.
PRE EMERGENT HERBICIDES FOR VOLUNTEER Acacia mangium CONTROL IN EUCALYPTUS PLANTATIONS IN INDONESIA
This study was a screening trial aimed at addressing the challenge of volunteer Acacia mangium weeds in Eucalyptus plantations. These weeds arise from a large A. mangium seedbank left behind in plantations, making pre-emergent herbicides with residual effects essential for effective control. The objective of this research was to identify effective pre-emergent herbicides, with residual effect, to control volunteer A. mangium weeds in Eucalyptus plantations. Completely randomized design (CRD) was used with 4 replications. Trays with size of 50 cm x 33 cm were filled with a loamy top layer soil from commercial plantations. Each tray was sown with 100 A. mangium seeds, after treatment for dormancy break. Fifteen herbicide active ingredients were tested, with a control treatment (no herbicide). Active ingredients tested were Imazapyr, Metsulfuron-methyl, Triclopyr, Isoxaflutole, Indaziflam, Flumioxazine, Sulfentrazone, Oxyfluorfen, Pendimethalin, Metribuzin, Ametryn, Diuron and Saflufenacil. Herbicides were applied 1 day after seeds sowing and emerged seedlings were counted weekly until day 35 (first period assessment). After the first period was finished, all A. mangium emerged seedlings and remaining seeds were removed and 100 new A. mangium seeds were sown to each tray to test the residual effect. No additional herbicide was applied for the second period, which was assessed weekly until 35 days after second sowing (63 days total). Indaziflam + iodosulfuron, metribuzin, saflufenacil, sulfentrazone and isoxaflutole were effective in controlling A. mangium in pre emergence, with less than 7.0% emerged plants at 35 DAS, against 92.3% in control treatment. The assessment of residual effect done 63 DAS showed that indaziflam + iodosulfuron and metribuzin gave the best results, with 0.0% and 11.3% emerged plants, against 100% in control treatment.
Tempo disponível para movimentação de diferentes glyphosates no controle de Brachiaria plantaginea (Link) Hitch
Introdução: A Brachiaria plantaginea (Link) Hitch, é uma daninha que apresenta rápido crescimento, deste modo, pode diminuir a capacidade fotossintética da cultura de interesse em estágios iniciais. Objetivo: O objetivo desse estudo foi avaliar o efeito temporal na translocação das caldas de herbicidas a base de glyphosate para as partes não aplicadas em plantas de B. plantaginea. Métodos: Utilizou-se o delineamento experimental inteiramente casualizado em esquema fatorial 6x5, com cinco repetições. O primeiro fator foi constituído pelas caldas de pulverização (Crucial®, Roundup Original® Mais, Roundup® Transorb r, Roundup® WG, Roundup Ultra® e Zapp Qi 620, e o segundo, pelo tempo de permanência das folhas de B. plantaginea que receberam aplicação (30, 60, 120, 240 e 480 minutos). Resultados: O Roundup Transorb® r foi o herbicida que proporcionou maior taxa de cobertura com 63,8%, enquanto as soluções que proporcionaram menores taxas de coberturas foram Roundup Original® Mais e Crucial®. O tempo mínimo de 120 minutos para a retirada da folha que recebeu a aplicação, foi suficiente para o herbicida Zapp QI 620 proporcionar 52% de fitointoxicação. Conclusões: Nas condições do estudo, o glyphosate Zapp QI 620 foi o mais eficiente com 52% de controle das plantas de B. plantaginea aos 28 DAA, portanto houve efeito do tempo na translocação dos herbicidas a base de glyphosate para as partes não aplicadas. Plantas de B. plantaginea com aproximadamente 30cm de altura não são controladas com aplicação de 540g de ingrediente ativo de glyphosate em apenas uma folha.
Associações herbicidas aplicadas em pós-emergência no controle de capim-capeta em pastagem cultivada
Introdução: Um dos maiores desafios para assegurar a alta produtividade das pastagens cultivadas é a ocorrência de plantas daninhas, em especial àquelas pertencentes a família Poaceae, visto que as alternativas herbicidas para o controle de forma seletiva são escassas. Entre as espécies que têm trazido maiores prejuízos para a atividade pecuária, está o capim-capeta (Sporobolus indicus), visto que a mesma apresenta elevada agressividade quando em convivência com as pastagens. Herbicidas inibidores do Fotossistema II (FSII), como atrazine e terbuthylazine, apresentam efeito sinérgico quando associados ao mesotrione. Objetivo: Avaliar a eficácia do mesotrione isolado e em associações à herbicidas inibidores do FSII no controle em pós-emergência de capim-capeta infestando pastagem cultivada com Brachiaria humidicola. Métodos: O experimento a campo foi instalado sob delineamento de blocos completos ao acaso, avaliando-se nove tratamentos, com quatro repetições. Os tratamentos foram compostos pela aplicação em pós-emergência do mesotrione isolado e em associações à inibidores do FSII, variando-se proporções de doses dos herbicidas, bem como misturas formuladas comercialmente ou em adição ao tanque. Além disso, foi acrescido uma testemunha sem aplicação de herbicidas (presença da planta daninha). Na ocasião da aplicação dos tratamentos, as plantas de capim-capeta estavam em estádio reprodutivo (florescidas) e a pastagem encontrava-se em pleno desenvolvimento vegetativo. Foram realizadas avaliações de porcentagem de controle de capim-capeta e intoxicação visual da pastagem. Resultados: Independentemente da dose, o uso de mesotrione de forma isolada não foi capaz de impor níveis de controle satisfatórios sob às plantas de capim-capeta. A associação de atrazine ao mesotrione, seja em mistura formulada comercialmente ou em adição em tanque, proporcionou melhorias no controle de capim-capeta. Os desempenhos de atrazine + mesotrione, em mistura formulada comercialmente, e terbuthylazine + mesotrione, em mistura em tanque, independentemente das doses, foram semelhantes no controle de capim-capeta, constituindo-se nas melhores alternativas para o manejo químico desta espécie. Todos os tratamentos herbicidas proporcionaram baixos percentuais de injúrias às plantas de B. humidicola. Conclusões: Associações entre mesotrione e inibidores do FSII apresentam potencial de controle de capim-capeta, sendo seletivas para pastagem cultivada com B. humidicola.
Control de Bidens subalternas con diferentes formulaciones de Clomazone en dos localidades del departamento de Canindeyú
Introducción: la resistencia de Bidens subalternans al glifosato y herbicidas inhibidores de ALS va en aumento en las regiones de producción de soja en Paraguay, por lo cual el uso de herbicidas pre-emergentes es cada vez más importante entre ellas el clomazone, cuyo principal inconveniente es la volatilización, algunas formulaciones como las microencapsuladas pueden reducir eso en comparación con otras formulaciones. Objetivos: el presente trabajo tuvo como objetivo evaluar la eficacia de diferentes formulaciones de clormazone en el control de Bidens subalternans en pre-siembra de la soja. Materiales y métodos: los experimentos fueron conducidos en las localidades de San Juan y Nueva Esperanza (Canindeyú, Paraguay). Los tratamientos fueron diferentes formulaciones de clomazone aplicados en pre-emergencia del Bidens subalternans, las evaluaciones de control fueron hasta los 42 días después de la aplicación (DDA). Resultados: los resultados obtenidos de control de Bidens subalternans en ambas localidades fueron similares, los controles de las formulaciones microencasuladas fueron consistentes hasta los 42 DDA, siendo superior a las formulaciones suspensión concentradas. Conclusión: las aplicaciones de clomazone fueron eficiente de forma general, siendo las formulaciones micoencapsuladas superiores hasta los 42 DDA.
Barnyardgrass control with pre-emergent herbicides in no-till irrigated rice
The adoption of no-till drilled rice by some producers, facilitated by increasing crop rotations and integration with cattle breading, has led to varying ryegrass residue volumes. Herbicide efficiency may vary accordingly to their physicochemical characteristics, interaction with pasture residue, moisture and rainfall availability. Our aim was to investigate the influence of ryegrass residue volume on barnyardgrass control in irrigated rice established in no-till drilling systems. The experiment was conducted during the 2018/19 and 2019/20 crop seasons using a factorial scheme within a randomized block design and four replicates. Factor A was determined by the ryegrass residue volumes, and Factor B was defined by the spraying of pre-emergent herbicides. Barnyardgrass control varied depending on residue volume and soil moisture post-herbicide spraying. Pendimethalin provided poor weed control under conditions of lower post-spraying moisture and higher ryegrass residue volume but resulted in higher panicle density at the end of the cycle. In contrast, the performance of clomazone, [imazapic + imazapyr] and penoxsulam was less affected by these factors. Herbicide efficacy indirectly influenced grain yield, as it was higher in rainy years with greater ryegrass residue volume. Due to its high lipophilicity, pendimethalin's performance was compromised with higher residue volume and low rainfall and should be avoided under these conditions. Clomazone, penoxsulam and [imazapyr + imazapic] were more consistent regardless of residue volume and rainfall.
Copyright (c) 2025 Brazilian Herbicide Journal
MANEJO DE Schizachyrium microstachyum EM FUNÇÃO DE HERBICIDAS PRÉ-EMERGENTES E COBERTURA VEGETAL DO SOLO
Contexto: Schizachyrium microstachyum, também denominada capim-rabo-de-burro, é uma planta daninha perene, de elevada rusticidade e alta prolificidade. As falhas no controle e aumento expressivo da sua migração de campos nativos para áreas cultivadas, indicam a necessidade de integração de novas estratégias de manejo. Objetivo: Avaliar a eficácia de controle e emergência de S. microstachyum em resposta a aplicação de herbicidas pré-emergentes, considerando a interação com e sem cobertura de palha. Métodos: O experimento foi conduzido em casa de vegetação, sendo repetido em duas épocas. Os tratamentos foram dispostos em delineamento inteiramente casualizado, arranjado em esquema fatorial 2 x 13, onde o fator A constou de ausência ou presença de palha de aveia preta distribuída sobre a superfície do solo e, o fator B doze herbicidas pré-emergentes, além da testemunha sem aplicação. Foram realizadas avaliações de controle, emergência total de plântulas e massa da matéria seca da parte aérea de S. microstachyum. Resultados: Observou-se controle eficiente pelos herbicidas s-metolacloro, piroxasulfona, piroxasulfona+flumioxazina, atrazina e clomazone, na condição com ou sem cobertura, assim como, pendimentalina e trifluralina, que foram mais eficientes nas últimas épocas avaliadas. Sulfentrazone e imazetapir+flumioxazina, sem a cobertura, reduzem as porcentagens de emergência. Diclosulam resultou em reduzida eficiência de controle e maior emergência de S. microstachyum. Conclusões: Os herbicidas s-metolachlor, piroxasulfona, piroxasulfona+flumioxazina, atrazina e clomazone foram eficientes no controle de S. microstachyum nas duas conduções do experimento, independentemente da presença de palha de aveia. Na ausência de cobertura vegetal, em relação a presença, houve menor emergência de S. microstachyum quando aplicados os herbicidas diclosulam, sulfentrazone, sulfentrazone+diuron, imazetapir, imazetapir+flumioxazina e trifluralina.
ADDITION OF AMMONIUM SULFATE TO GLYPHOSATE IN THE DESICCATION OF Urochloa Brizantha CV. BRS “PIATÃ”
Abstract: Background: Glyphosate is the most widely used herbicide in Brazilian agriculture, and management techniques that increase its efficacy are important tools for the production system. Objective: The aims of this study were to assess the effect of adding the nitrogen adjuvant ammonium sulphate [(NH4)2 SO4] to glyphosate on the control of Urochloa brizantha BRS Piatã and establish the best [(NH4)2 SO4] dose to mix with the herbicide. Methods: To that end, two greenhouse experiments were conducted. In the first, six glyphosate doses (0; 33.75; 67.5; 135; 270; 540 g. ae. ha-1) were used to determine C80 (glyphosate dose that achieved 80% control of BRS Piatã grass). This dose was used as a reference for the second experiment, in a mixture with four [(NH4)2 SO4] doses (0; 6.67; 13.33; and 20 g L-1 of solution) to determine the best nitrogen adjuvant dose. In both experiments, BRS Piatã grass control was assessed at 7, 14 and 21 days after treatment (DAT), and shoot length and dry weight at 21 DAT. Results: While the C80 of glyphosate was established at 270 g. ae ha-1. The visual scale indicated that adding [(NH4)2 SO4] accelerated the glyphosate-related symptoms but did not change plant fresh and dry weight and shoot length. Maximum glyphosate efficacy was obtained by adding ammonium sulphate at a concentration of 16.2 g L-1 of solution. Conclusions: Ammonium sulphate accelerates the glyphosate mode of action in the desiccation of Urochloa brizantha BRS Piatã.
Eficácia e seletividade de herbicidas residuais na cultura da soja na região do cerrado
O uso de herbicidas residuais, de grupos químicos e mecanismos de ação diferentes, é uma ótima opção técnica, tanto pelo aspecto de controle como de seletividade para a cultura da soja. Avaliar a eficácia e a seletividade de diferentes herbicidas residuais isolados ou em mistura comerciais, pulverizados em pré-emergência, na cultura da soja, na região originalmente sob Cerrado. Dois experimentos foram desenvolvidos em área de produção comercial de soja em Planaltina, DF, um de controle e outro de seletividade, no qual os escapes de plantas daninhas ao controle químico foram removidos. O delineamento experimental foi o de blocos ao acaso, com 10 tratamentos de herbicidas, duas testemunhas (capinada e infestada) no experimento de controle e apenas uma (a capinada) no experimento de seletividade, e quatro repetições. Os tratamentos de herbicidas foram pulverizados um dia após a semeadura da soja (cultivar Brasmax Desafio RR 8473 RSF). De forma geral, os tratamentos de herbicidas foram eficazes no controle das plantas daninhas da área experimental, sem a necessidade de complementação do manejo na pós-emergência; e, quando associados a uma cultivar com elevada capacidade competitiva e condições adequadas de cultivo, o potencial produtivo das plantas foi garantido. A aplicação de herbicidas residuais na pré-emergência foi suficiente para o controle das plantas daninhas, sem prejuízos à produtividade de grãos. O único tratamento de herbicida que prejudicou a produtividade de grãos da soja foi o diclosulam, na dosagem de 29,4 g ha-1.
Tolerância de Tifton 85 e Jiggs (Cynodon dactylon L.) à herbicidas pós-emergentes
Apesar do potencial de forrageiras do gênero Cynodon, o manejo de cultivares dessas plantas em condições de cultivo brasileiras são escassos. Objetivou-se avaliar a tolerância do Tifton 85 e Jiggs a diferentes herbicidas em pós-emergência das forrageiras. O experimento foi conduzido em vasos, em casa de vegetação. Foram conduzidos dois experimentos, com as forrageiras Tifton 85 e Jiggs, e doze tratamentos comuns, sendo onze herbicidas e uma testemunha sem aplicação. Foram avaliadas a fitotoxidez dos herbicidas aos 7, 14, 21, 28, 35 e 50 dias após a aplicação, os teores de clorofila a e b e a capacidade de rebrota das forrageiras 60 dias após o corte. A partir dos 14 DAA o herbicida glifosato, seguido pelo fluazifop-p-butil, apresentaram elevada fitotoxidez aos capins e com significativa redução nos teores de clorofila das plantas de Tifton 85. As forrageiras tratadas com glifosato não apresentaram rebrota aos 60 dias após o corte. A tembotriona não teve influência sobre a rebrota do Tifton 85 e 2,4-D, atrazina, cletodim e lactofem não tiveram nenhum efeito negativo sobre a rebrota do Jiggs aos 60 dias após o corte, sendo boas estratégias no manejo químico de plantas daninhas em pastagens de Tifton 85 e Jiggs, respectivamente.
Weed community dynamics in a cover crop / silage maize succession crop system
The objective of this study was to evaluate the weed community in an Urochloa ruziziensis / silage maize (Zea mays L.) succession system in which the cover crop received potassium (K) fertilizer. In the fall/winter growing season, treatments were U. ruziziensis and six doses of K (0, 30, 60, 90, 120 or 150 kg K2O ha-1) as muriate of potash (KCl) in addition to fallow. In the summer season, maize was cultivated with doses of K, complementary to the fall/winter season to total 150 kg K2O ha-1: (i.e., 120, 90, 60, 30, and 0) and 0 kg K2O ha-1 for fallow. The previous fallow treatment received the recommended K fertilization (60 and 90 kg ha-1 of K2O at planting and at maize sidedressing, respectively). A weed population survey was carried out using a 0.50 cm square. Their phytosociological indices, dry mass, number and total density of species was calculated. The weed community and its phytosociological indices are altered as a result of the growing season and crop. Weed dry mass is higher before cutting the U. ruziziensis. The number of species and plant density is higher at the V4 maize growth stage before applying the herbicide.
INTERFERÊNCIA E NÍVEL DE DANO ECÔNÔMICO DE AZEVÉM NA CULTURA DO CENTEIO
RESUMO Introdução: Na ecologia de plantas, ocorre competição quando uma ou mais espécies utilizam dos recursos limitados e essenciais para o seu crescimento e desenvolvimento. Para o centeio (Secale cereale) uma das plantas daninhas que mais causa perda de produtividade e da qualidade do produto colhido é o azevém (Lolium multiflorum). Objetivo: testar modelos matemáticos e identificar variáveis explicativas para determinar a habilidade competitiva e o nível de dano econômico (NDE) de azevém na cultura do centeio. Métodos: O experimento foi instalado a campo, em delineamento completamente casualizado, sendo os tratamentos compostos por genótipos de centeio (BRS Serrano, IPR 89, BRS Progresso e Crioulo) e 12 densidades de azevém em competição com a cultura, saindo de 0 até o máximo de 68 plantas m-2. Avaliou-se aos 30 dias após a emergência das plantas as variáveis, densidades de plantas, área foliar, cobertura de solo e massa seca da parte aérea do azevém. Resultados: O modelo da hipérbole retangular foi eficiente para estimar as perdas da produtividade de grãos pela infestação de azevém na cultura do centeio. Os genótipos de centeio BRS Serrano e IPR 89 foram os mais e o BRS Progresso e o Crioulo os menos competitivos na presença do azevém. Os genótipos BRS Serrano e IPR 89 apresentaram maior desempenho competitivo e NDE, com valores de 2,28 a 8,23 plantas m-2, respectivamente. Conclusões: A produtividade de grãos, o preço da saca, a eficiência do herbicida e o custo de controle, causam variação dos valores no NDE.
Seletividade de associações herbicidas aplicadas em pós-emergência do milho cultivado em segunda safra
Introdução: A interferência das plantas daninhas no milho consiste em um dos principais entraves para a obtenção de altas produtividades nesta cultura. Neste contexto, o uso de herbicidas se constitui no principal método de controle, podendo repercutir em grande êxito ao agricultor se empregado na época (estádio) e doses recomendadas. Objetivo: O objetivo deste trabalho foi avaliar a seletividade de associações herbicidas aplicadas em aplicação de pós-emergência do milho cultivado em condições de segunda safra. Métodos: Foi instalado um experimento a campo no delineamento de blocos completos ao acaso, avaliando-se onze tratamentos, sendo adotadas quatro repetições. Os tratamentos foram compostos pela aplicação em pós-emergência do milho de herbicidas isolados, em misturas comercialmente formuladas e/ou em misturas em tanque, havendo na composição destes os seguintes ingredientes ativos: nicosulfuron, mesotrione e atrazine. Na ocasião da aplicação dos tratamentos, as plantas de milho estavam no estádio V3/V4. Foram realizadas avaliações de fitointoxicação, estande de plantas, altura de inserção da espiga, componentes de rendimento e produtividade de grãos. Resultados: Os níveis de fitointoxicação foram baixos em função da aplicação dos tratamentos herbicidas em pós-emergência do milho. De maneira geral, a mistura formulada à base de atrazine + mesotrione proporciona menor fitotoxicidade em relação à mistura em tanque destes ingredientes ativos. Os componentes de rendimento relacionados às espigas do milho não foram afetados pela aplicação dos herbicidas em pós-emergência. Conclusões: Todos os herbicidas aplicados em pós-emergência das plantas de milho, independentemente se utilizados de forma isolada ou em associação, são seletivos para esta cultura.
Management of glyphosate-resistant smooth pigweed and horseweed in burndown, pre-emergence and post-harvest in soybean
Background: The advance of smooth pigweed in soybean fields is associated with the evolution of this weed resistance to herbicides. Its presence, together with that of other important weeds, such as horseweed, affect crop’s grain yield. Objective: Our aim was to evaluate the efficiency of different combinations of herbicides in burndown and pre-emergence for the control of smooth pigweed and horseweed in soybean, and the efficiency of herbicides in off-season management of smooth pigweed. Methods: The trials were carried out in a complete randomized block design. The visual control variables and plant population of smooth pigweed and horseweed were evaluated, in addition to soybean grain yield. As in off-season, control (%) and dry weight of smooth pigweed plants and phytotoxicity and dry weight of the cover crop ryegrass were evaluated. Results: Was observed effect of pre-emergent herbicides in the control of smooth pigweed, constituting an indispensable tool in the management of smooth pigweed. The PRE herbicides sulfentrazone+diuron and S-metolachlor+metribuzin combined with carfentrazone+saflufenacil at burndown can be spray. In relation to horseweed, the main effect of all burndown herbicides was observed. In the off-season management of smooth pigweed, the mixtures containing carfentrazone were efficient in the control, and not cause a significant phytotoxicity to the ryegrass. Conclusions: PRE herbicides are essential in the management of smooth pigweed and horseweed and those that promote better control are the combinations sulfentrazone+diuron and S-metolachlor+metribuzin. The tank mixture with carfentrazone demonstrate some phytotoxicity for the ryegrass crop but control Smooth pigweed.
SUSCEPTIBILITY OF NON-TOLERANT SOYBEAN TO LOW RATES OF DICAMBA
Abstract Background: The possibility of intoxicating non-tolerant soybean with dicamba is an important and currently problematic in agricultural fields. Objective: Six experiments were carried out to evaluate the correlation between toxicity of low dicamba rates and yield of non-tolerant soybean cultivars. Methods: Three areas were selected and two experiments were carried out in each area: one for soybean at V3 and another for R1/R2 stage. Five dicamba rates (five treatments) were applied in each experiment. Toxicity was evaluated at 7, 14, 21, and 28 days after application; the others variables evaluated were plant stand, pre-harvest plant height, production components, and crop yield. Additionally, the maximum toxicity was correlated to the relative yield for each plot. Results: The dicamba rate of 1 g ha-1 was a critical threshold to distinguish rates that caused only phytotoxicity from those that decreased crop yield. Visual toxicity symptoms that did not cause meristematic changes (up to 20% in plants at vegetative stage and 10% in plants at reproductive stage) did not decrease soybean yield. Conclusions: The correlation between dicamba toxicity and soybean crop yield is the most important factor to be considered under field conditions. Soybean plants sprayed at reproductive stage (R1/R2) had higher yield losses than at vegetative stage: each 10% increase in phytotoxicity in soybeans at R1/R2 would result, on average, in 12.2% yield loss.
Interference of adjuvants and nitrogen fertilizers on the efficiency of saflufenacil and ammonium glufosinate in Conyza spp. control.
The use of adjuvants and nitrogen fertilizers mixed with herbicides can positively or negatively interfere with weed control efficacy, such as in the case of Conyza spp. The present study aimed to investigate the interference of adjuvants and nitrogen fertilizers added to the spraying solution on the efficacy of the herbicides saflufenacil and ammonium glufosinate on Conyza spp control. The experiments were carried out in a greenhouse under a randomized block design, in a 5x3 factorial scheme with four replications. Factor A consisted of the herbicides saflufenacil (EI) (70 g a.i. ha-1) and ammonium glufosinate (500 g a.i. ha-1) (EII) applied individually and in combination with the adjuvants Aureo®, Assist®, Dash® and Agral®. Factor B included the nitrogen fertilizers ammonium sulfate and urea, in addition to an untreated check. The applications were carried out when plants were at the 13 - 15 cm growth stage. The data were subjected to analysis of variance (ANOVA) and Tukey’s test at a 5% significance level. Regardless of adjuvant or nitrogen fertilizer used in combination with saflufenacil, all treatments showed satisfactory control of Conyza spp, similar to the isolated herbicide. For improved Conyza spp. control with ammonium glufosinate, it is not recommended to mix urea or ammonium sulfate with the Dash® adjuvant in the spray solution. In contrast, the control efficacy of Conyza spp. with ammonium glufosinate was higher when Agral® was used in the mixture. The use of adjuvants and/or nitrogen fertilizer in spray tank mixtures with ammonium glufosinate herbicide is essential for effective control of Conyza spp plants. Keywords: Weed control, Herbicide interaction, Herbicide application, Tank mix.
SELETIVIDADE DE HERBICIDAS AO TREMOCEIRO EM PRÉ E PÓS-EMERGÊNCIA
O tremoceiro é uma leguminosa com diversas utilidades, desde o consumo humano e até efeitos no solo e no controle de planta daninhas. Contudo, essa planta carece de herbicidas registrados, os quais auxiliam no processo de seu cultivo. Assim, o objetivo deste trabalho foi avaliar a seletividade dos herbicidas pré e pós-emergentes na cultura do tremoço. Ambos os experimentos foram conduzidos em ambiente controlado, com temperatura entre 23ºC e 25ºC e fotoperíodo de 12 horas. Foram utilizados vasos plásticos de 500 mL preenchidos com uma mistura de solo e areia (2:1 v/v). A semeadura do tremoço foi feita depositando cinco sementes, seguida da irrigação. Para ambos, o delineamento experimental foi o inteiramente casualizado com os seis tratamentos e uma testemunha (sem aplicação) em cinco repetições, totalizando assim 35 parcelas experimentais. Aos 13, 23, 27 e 36 dias após aplicação (DAA) foram realizadas avaliações de fitotoxicidade, atribuindo-se notas de visuais, segundo a Escala da EWRC. Aos 36 DAA foram medidos os comprimentos das raízes e determinadas as respectivas massas secas por parcela, após secagem em estufa de ar a 60ºC. Os dados foram submetidos à análise de variância pelo teste F, seguido pelo teste de Tukey ao nível de 5% de probabilidade. Os resultados demostraram que os herbicidas pré-emergentes sulfentrazone e trifluralina apresentaram fitotoxicidade à cultura do tremoço e que herbicidas pós-emergentes o chlorimuron-ethyl e fomesafen também foram fitotóxicos. Assim, conclui-se que sulfentrazone, trifluralina, chlorimuron-ethyl e fomesafen não apresentam seletividade para cultura do tremoço.
ASSOCIAÇÃO ENTRE GLYPHOSATE E FERTILIZANTES FOLIARES A BASE DE ENXOFRE E SEUS EFEITOS NA CULTURA DA SOJA GM
Os efeitos decorrentes da aplicação de herbicidas em mistura com fertilizantes nas culturas agrícolas são de extrema importância para o sucesso na produção agrícola. O objetivo do trabalho foi avaliar o efeito de formulações de glyphosate aplicadas em mistura com fertilizantes à base de enxofre na soja resistente ao glyphosate. O experimento foi delineado em blocos ao acaso com quatro repetições, utilizando-se a soja cultivar BMX Potência RR. Os tratamentos obedeceram a um fatorial (4x3), entre três formulações de glyphosate (Roundup WG; Roundup Ultra; Glizmax e testemunha sem herbicida), e dois fertilizantes à base de enxofre (Nutrixofre; Tiossulfato de amônio e sem fertilizante), totalizando 12 tratamentos. A mistura de fertilizantes e herbicidas não afetou o controle de plantas daninhas para os tratamentos Roundup WG e Roundup Ultra. A mistura Glizmax + Nutrixofre resultou em menor controle de plantas daninhas. A massa de 100 grãos foi incrementada pela aplicação da formulação Roundup WG, e reduzida quando da aplicação de Glizmax, independentemente da mistura com enxofre. Os tratamentos compostos somente da aplicação de fertilizantes sulfatados e a testemunha absoluta, com plantas desenvolvidas com infestação, apresentaram os maiores teores de S no tecido foliar. As plantas tratadas com glyphosate apresentaram baixos teores de S (1,5 a 2,0 g ha-1). O uso de Glizmax resultou em menores produtividades quando da aplicação em mistura com os fertilizantes. A mistura que resultou em maior ganho produtivo para a soja, cv. BMX Potência RR foi o Roundup WG em mistura com Tiossulfato de amônio.
SELETIVIDADE DE HERBICIDAS PRÉ-EMERGENTES AO EUCALIPTO E PINUS APLICADOS ANTES OU APÓS O PLANTIO
Fatores como formulação, dose, tecnologia de aplicação, características do solo, espécie e temperatura, influenciam na seletividade de herbicidas, sendo que culturas como as do eucalipto e pinus são carentes de produtos registrados. Com o objetivo de avaliar a seletividade de herbicidas pré-emergentes aplicados antes ou depois do plantio de eucalipto e pinus, este trabalho testou as modalidades de aplicação “aplique-plante” (AP) e “plante-aplique” (PA) em Eucalyptus urograndis – Clone 1407 e Pinus caribaea var. hondurensis para cinco ingredientes ativos: flumioxazina 90 g i.a. ha-1, indaziflam 75 g i.a. ha-1, isoxaflutol 150 g i.a. ha-1, oxyfluorfen 960 g i.a. ha-1 e sulfentrazona 800 g i.a. ha-1. Dois experimentos foram conduzidos em vasos pelo período de 96 dias após a aplicação (DAA), em delineamento experimental de blocos casualizados, em cinco repetições. Os tratamentos consistiram de um fatorial 2x6. Foram feitas avaliações de fitointoxicação, altura, diâmetro e massa seca (MS) das plantas, além do calculo de taxa de crescimento absoluto. Para a MS, área foliar e altura do eucalipto, verificou-se que não houve diferença entre as modalidades de aplicação e os herbicidas testados. Para o diâmetro do pinus, não houve diferença entre os tratamentos na modalidade AP, e entre os herbicidas testados na modalidade PA. Indaziflam foi prejudicial ao pinus na modalidade AP, causando redução de 37,4% na MS aos 96 DAA, quando comparado com a modalidade PA.
HERBICIDE DOES NOT IMPACT DIAZOTROPHIC BACTERIA-PROMOTING GROWTH OF RED RICE PLANTS
Background Diazotrophs bacteria that promote plant growth have been studied as a strategy to increase the productivity of rice cultivation. Herbicides are used to prevent weed infestations. Objective The evaluation of herbicides effect on diazotrophic bacteria strain associated with the growth of Red Small rice. Methods Three experiments were conducted: I - in vitro growth of bacterias (Azospirillum brasilense strain 245 and Herbaspirillum seropedicae strains 26H, Z67, Z94, ZA25 and ZAL95); II - germination of red rice seeds; III - growth and production of red rice plants inoculated with diazotrophic bacteria and treated with quinclorac, penoxsulam and cyhalofop-butyl herbicides. Results I - All bacterial strain growth was inhibited under the highest herbicide doses, except strain 245. II – The number of roots reduced upon increasing herbicide concentration for strain 245. III - The dry mass increased in plants inoculated with strains 245 and ZA25. Besides, strains 245, 26H and ZAL95 provided better performance for dry root mass. At 60 days, the same behavior of the first evaluation was observed. At final cycle, increases in fresh and dry root mass and dry mass of grains were evidenced, especially on rice inoculated with strains 245 and ZA25. Conclusions The herbicides do not impact Azospirillum and Herbaspirillum bacterial strains. Besides, strains 245 and ZA25 show better performance in promoting plant growth of rice.
RESPOSTAS MORFOFISIOLÓGICAS DE CULTIVARES DE TRIGO À APLICAÇÃO DE SAIS DE 2,4-D AMINA E COLINA
O herbicida 2,4-D é produzido em algumas formulações que podem apresentar diferenças de seletividade às culturas. Objetivou-se com o trabalho avaliar os efeitos da aplicação dos sais de 2,4-D amina e colina na morfofisiologia de cultivares de trigo. Os tratamentos testados foram testemunha sem herbicida, 2,4-D amina e 2,4-D colina) e cultivares de trigo (ORS 1403, ORS Citrino, ORS Madre Pérola, TBIO Toruk, TBIO Energia, TBIO Audaz, TBIO Sonic e TBIO Sossego). Aos 7, 14 e 21 dias após a aplicação dos tratamentos (DAT) foi avaliado a fitotoxicidade dos herbicidas. A concentração interna de CO2 (Ci), condutância estomática (gSGS), taxa de transpiração (E), taxa fotossintética (A), eficiência no uso da água (EUA) e eficiência da carboxilação (EC) foram aferidas aos 26 DAT. Aos 30 DAT foram aferidas a área foliar (AF) e a massa seca da parte aérea (MS) das plantas de trigo. A fitotoxicidade ocasionada pelos sais de 2,4-D sobre as cultivares de trigo foram baixas, sendo o sal colina o que apresentou os menores efeitos. A cultivar TBio Toruk apresentou melhor desempenho fisiológico (Ci, gS, A e EC) após a aplicação do sal 2,4-D amina. A cultivar TBIO Sonic não demonstrou redução de acúmulo de MS e de AF ao se usar os sais de 2,4-D. O uso do 2,4-D amina e colina nas cultivares ORS 1403 e ORS Madre Pérola apresentou maior acúmulo de MS. Os sais de 2,4-D amina e de 2.4-D colina foram seletivos para a maioria das cultivares de trigo em que foram aplicados.
Copyright (c) 2023 Brazilian Herbicide Journal
MANEJO QUÍMICO DE CARURU-ROXO (Amaranthus hybridus) COM HERBICIDAS APLICADOS EM PRÉ E PÓS-EMERGÊNCIA
Histórico: Para se ter êxito no controle de A. hybridus torna-se necessário a adoção de programas de manejo integrados como, o uso de dessecantes em conjunto com práticas culturais, com herbicidas pré e/ou pós-emergentes, com rotação de mecanismos de ação em virtude dessa espécie apresentar resistência aos inibidores de ALS e EPSPs. Objetivo: Avaliar a eficácia de herbicidas aplicados em pré e/ou pós-emergência para o manejo químico de A. hybridus. Métodos: Foram conduzidos experimentos em casa de vegetação, sendo no primeiro aplicado os herbicidas pré-emergentes; diclosulam, imazethapyr, [imazethapyr+flumioxazin], S-metolachlor, atrazina, [atrazina+simazina], metribuzin, flumioxazin, sulfentrazone, [sulfentrazone+diuron], mais uma testemunha infestada. No segundo experimento usou-se os herbicidas; chlorimurom-ethyl, imazethapyr, mesotrione, glyphosate, diquat, metribuzin, atrazina, [mesotrione+atrazina], [atrazina+simazina], glufosinato de amônio, saflufenacil, carfentrazone, flumioxazin, fomesafen, 2,4-D colina, 2,4-D amina, dicamba, em pós-emergência, mais uma testemunha sem aplicação. Resultados: Os herbicidas inibidores da ALS não apresentram bom desempenho de controle. Os herbicidas atrazina e [atrazina+ simazina] demontraram boa eficácia em ambos os experimentos. Destaca-se que os herbicidas pertencentes aos mecanismos de ação inibidores de Protox para os pré-emergentes e pós-emergentes, Inibidores do Fotossistema II e de ação total, como glyphosate, diquat e glufosinato de amônio pelo bom controle do A. hybridus. Conclusões: Os herbicidas [imazethapyr+flumioxazin], flumioxazin, sulfentrazone e [sulfentrazone+diuron] apresentaram os melhores controles de A. hybridus em pré-emergência. O diclosulam, imazethapyr e o metribuzin não demonstraram eficiência em pré-emergência. A aplicação de chlorimiuron ethyl e imazethapyr não apresentou eficácia em pós-emergência. Os herbicidas diquat, glufosinato de amônio e saflufenacil demonstraram bom controle de A. hybridus.
Copyright (c) 2024 Brazilian Herbicide Journal
PERFORMANCE DE HERBICIDAS NA DESSECAÇÃO PRÉ-COLHEITA DE CULTIVARES DE SOJA
A dessecação de pré-colheita tornou-se comum no cultivo de soja, principalmente pela necessidade de antecipação da colheita para grãos ou sementes. Contudo, existem poucos herbicidas registrados para esta prática, podendo ainda apresentar efeitos distintos conforme a região de cultivo da cultura. Diante disto, este trabalho teve o objetivo de avaliar os efeitos de herbicidas nas características agronômicas e na qualidade fisiológica das sementes de soja em duas importantes regiões produtoras do Brasil. Os experimentos foram conduzidos em Rio Verde, Goiás e Maringá, Paraná. Os tratamentos foram constituídos pela aplicação dos herbicidas 2,4-D, atrazine, glufosinate e paraquat, acrescido da testemunha, aplicados na maturidade fisiológica das cultivares de soja BRS 7560®, M-Soy 6101®, NK 9070 RR®, BMX Potência RR®. Os resultados obtidos permitiram concluir que os herbicidas não influenciaram a produtividade de grãos e os componentes de produtividade, além dos mesmos serem eficazes em antecipar a desfolha das plantas em ambas as localidades. Houve efeito diferenciado dos herbicidas nas características de germinação e vigor para ambas as localidades, demonstrando a necessidade de um posicionamento específico para cada cultivar para produção de sementes em função da região de cultivo.
CONTROL SPECTRUM OF THE NEW HERBICIDE PYROXASULFONE
There is not sufficient information about the efficiency of pyroxasulfone to the control of the main weeds that infest Brazilian agricultural areas. Thus, the objective of this study was to evaluate the efficiency of the pyroxasulfone treatments to control some of the main weeds present in Brazil, comparing it to S-metolachlor and trifluralin. The treatments consisted of five increasing doses of pyroxasulfone (50, 100, 150, 200 and 250 g ha-1), two doses of S-metolachlor (960 and 1920 g ha-1), two doses of trifluralin (562.5 and 1125 g ha-1) and a untreated check. The control (scale from 0 to 100%) was evaluated at 14, 28 and 42 days after application and the shoots were collected at 42 DAT for biomass quantification. Each weed species constituted an independent experiment, namely: Amaranthus viridis, Chloris elata, Conyza spp., Echinochloa crus-galli, Urochloa decumbens, Digitaria horizontalis, Digitaria insularis, Eleusine indica, Lolium perenne ssp. multiflorum, Panicum maximum, Raphanus raphanistrum, Spermacoce latifolia, Spermacoce verticillata. The results observed in this study suggest that the application of 100 g ha-1 of pyroxasulfone in pre-emergence was an effective treatment to control all weeds evaluated. The application of 100 g ha-1 of pyroxasulfone was like or higher than the highest doses of S-metolachlor and trifluralin. These results confirm that pyroxasulfone, a new herbicide registered in Brazil, could become an important tool for weed management in many crops as well as it might help to mitigate herbicide resistance, especially for grasses.
Use of herbicides to control regrowth plants of Euphorbia heterophylla
The control of mature weeds in agriculture demands higher costs and more complex management strategies than the treatment of younger plants. This control is more difficult on regrowth weeds that present morphologic, physiologic, and biochemical characteristics that provide higher tolerance. This study aims to evaluate the control efficiency of different herbicides and associations, in different doses, on regrowth plants of Euphorbia heterophylla in the fall period, after the cultivation of common beans in a second harvest. The experiment was conducted in field conditions in a randomized block design with four repetitions of thirteen treatments: control (without herbicide); glyphosate (868 and 1736 g ha-1); metsulfuron (1.2 and 2.4 g ha-1); 2.4-D (335 and 670 g ha-1); metsulfuron + 2.4-D (1.2 + 335 g ha-1 and 2.4 + 670 g ha-1); iodosulfuron (1.75 and 3.5 g ha-1); triclopyr (48 and 96 g ha-1). Thirty-five days after the herbicide application, the following characteristics were evaluated: phytotoxicity, plant height, number of seeds per plant, and dry mass. The results demonstrate that the use of glyphosate in both doses tested (868 and 1736 g ha-1) provides adequate control of regrowth plants of E. heterophylla. The use of metsulfuron + 2.4-D (2.4+670 g ha-1) stands out as an efficient alternative when is not possible the use of full action herbicides, demonstrating high phytotoxicity (94%) and reduction of dry mass (89%).
EFICÁCIA E SELETIVIDADE DE HERBICIDAS RESIDUAIS ASSOCIADOS A COBERTURAS VEGETAIS NA CULTURA DA SOJA
O objetivo na pesquisa foi avaliar a eficácia e seletividade de dois herbicidas residuais (imazethapyr + flumioxazin e imazethapyr + saflufenacil) em diferentes coberturas vegetais na cultura da soja cultivada no sistema Plante-Aplique. O delineamento experimental utilizado foi o inteiramente casualizado com nove tratamentos e quatro repetições. Os tratamentos utilizados se basearam na aplicação de imazethapyr + flumioxazin e imazethapyr + saflufenacil após a semeadura de soja em cobertura vegetal de milheto (Pennisetum glaucum), braquiária (Urochloa ruziziensis) e pousio (vegetação espontânea) previamente dessecados com glyphosate a 1,44 kg ha-1 de equivalente ácido + clethodim a 192 g ha⁻¹ de ingrediente ativo. Foram avaliadas a densidade populacional de plantas daninhas, a fitotoxicidade com a distância entre dosséis da massa vegetal na entrelinha, as características biométricas e as produtivas ao final do ciclo da cultura de soja. Os resultados demonstraram que o uso de plantas de coberturas reduziu a infestação de plantas daninhas, embora não dispensou o uso de herbicidas residuais no manejo. A planta de cobertura Urochloa ruziziensis teve maior efeito na supressão das plantas daninhas. Os tratamentos de imazethapyr associado a saflufencil ou flumioxazin foram seletivos para a soja cultivar Syn 1163 RR, para as condições em que este estudo foi realizado. Além disso, foi observado que a competição provocada pela comunidade infestante de plantas daninhas resultou na redução da produtividade de grãos da soja ao redor de 25%.
Copyright (c) 2022 Brazilian Herbicide Journal
Eficácia de herbicidas no controle Spermacoce verticillata e seletividade para as plantas de milho
Antecedentes: A planta daninha S. verticillata pode ser problemática para o milho, sobretudo quando este for cultivado em primeira safra. Neste contexto é importante se investigar a seletividade de herbicidas, bem como sua eficácia. Objetivo: Objetivou-se avaliar a eficácia de atrazine, saflufenacil, flumioxazin, carfentrazone e bentazon no controle de S. verticillata e o potencial de injúria nas plantas de milho. Métodos: O experimento foi conduzido em casa-de-vegetação, foi utilizado delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram compostos pela aplicação, em duas doses, de atrazine, saflufenacil, flumioxazin, carfentrazone e bentazon, além da testemunha sem aplicação. Foi avaliado o controle e os sintomas de injúria nas plantas de milho. Resultados: Maior injúria foi observada para a aplicação dos herbicidas flumioxazin e saflufenacil nas plantas de milho. De maneira geral com maiores sintomas para as maiores doses. Os herbicidas saflufenacil e flumioxazin estiveram entre os mais eficazes ao longo de todas as avaliações. A aplicação de atrazine também proporcionou controle final no mesmo patamar dos mais eficazes. Conclusões: Atrazine e carfentrazone foram eficazes no controle de S. verticillata e potencialmente seletivos paras as plantas de milho. Com possibilidade de uso no controle desta planta daninha e outras, em pós-emergência do cultivo. Saflufenacil e flumioxazin foram eficazes no controle de S. verticillata, contudo foram observadas injúrias no cultivo. Estes herbicidas podem ser considerados no controle, em outros cultivos ou em entressafra. O herbicida bentazon apresentou-se seletivo, contudo, não foi eficaz no controle de S. verticillata.
Controle de buva (Conyza spp.) em pré-semeadura da cultura da soja
A soja (Glycine max) é uma das mais importantes culturas plantadas no Brasil, sendo responsável por grande parte das exportações do país. O manejo e controle de plantas daninhas são necessários, dentre elas a buva (Conyza spp.) responsável por um percentual significativo de perda caso não seja controlada. O plantio direto na palha é a prática mais utilizada nas lavouras gaúchas e, com a proibição do herbicida paraquat, muito utilizado no manejo sequencial pré-plantio da soja no Rio Grande do Sul, torna-se necessário identificar alternativas eficientes a este manejo. Com este objetivo, estabeleceu-se o experimento onde foi dessecada a área com glifosato + 2,4-D e, realizou-se aplicações sequenciais de Paraquat, Glufosinato de amônio isolado e misturado com chlorimuron ethyl, flumioxazina e diclosulan, diquat isolado e misturado com chlorimuron ethyl, flumioxazina e diclosulan. A partir disso, avaliou-se que as misturas dos produtos glufosinato de amônio com clorimuron ethyl, flumioxazina e diclosulan e, diquat com chlorimuron ethyl, flumioxazina e diclosulan, apresentaram controle satisfatório e compatível com a eficiência do paraquat, demonstrando serem boas ferramentas no controle de daninhas no manejo dessecação pré-plantio.
AUXINIC HERBICIDES AND TEMBOTRIONE SPRAYED ON SEED-PROPAGATED ELEPHANT GRASS
Elephant grass plants propagated by seeds are more likely to have injuries to herbicides, in their initial cultivation phase, when compared to those from cuttings. This work evaluated the tolerance of elephant grass implanted by seeds to auxinic herbicides and tembotrione. Two experiments were conducted in the municipalities of Valença, Rio de Janeiro State, Brazil, and Coronel Pacheco, Minas Gerais State, Brazil. The experimental design was in randomized complete blocks, with four replications. The experimental treatments were: Auxinic herbicides [fluroxypyr + picloram (0.16 + 0.16 kg ae ha-1); fluroxypyr + aminopyralide (0.16 + 0.08 kg ae ha-1); fluroxypyr + triclopyr (0.16 + 0.48 kg ae ha-1); 2,4-D (1.34 kg ae ha-1); 2,4-D + picloram (0.72 + 0.045 kg ae ha-1)] and tembotrione (0.084 kg ai ha-1), in addition to the control without herbicides. Tembotrione was the most phytotoxic treatment to elephant grass propagated by seed, causing leaf bleaching and, consequently, reduced forage dry matter yield. The treatments with fluroxypyr + picloram, fluroxypyr + aminopyralide, fluroxypyr + triclopyr, 2,4-D and 2,4-D + picloram did not cause symptoms of phototoxicity capable of providing reduction in forage productivity, being potential herbicides for spraying in seed-propagated elephant grass fields.
SOURGRASS PHENOLOGICAL STAGE AND EFFICACY OF GLUFOSINATE-AMMONIUM
Recently, biotypes of sourgrass (Digitaria insularis) were identified in Brazil with multiple resistance to EPSPs-ACCase inhibiting herbicides, what demands the recommendation of herbicides with alternative mode of action, such as glufosinate-ammonium. Glufosinate-ammonium acts inhibiting glutamine synthetase, which is a key enzyme on nitrogen assimilation metabolism. This herbicide may be applied on mono or dicots; however, its efficacy may be influenced by plants’ phenology at the moment of application. Therefore, this work was developed with the objective of modelling the efficacy of glufosinate-ammonium on sourgrass regarding to five different phenological stages. Treatments consisted of eight herbicide rates (1,600, 800, 400, 200, 100, 50 and 25 g ha-1, and check plots without herbicide application) and five phenological stages of sourgrass. Percentage control was evaluated at 14, 21 and 28 days after application (DAA), as well as shoot dry weight at 28 DAA. The more developed sourgrass plants were, the higher doses of glufosinate-ammonium were needed to achieve satisfactory control. Glufosinate-ammonium is an excellent alternative for controlling sourgrass, however a second herbicide may be necessary for applications after tillering. Strong relation between sourgrass phenological development and increasing necessary rates of glufosinate-ammonium was identified.
SELETIVIDADE DE HÍBRIDOS DE MILHO AO HERBICIDA GLUFOSINATO DE AMÔNIO
A cultura do milho (Zea mays L.) desempenha papel fundamental nas diversas cadeias produtivas dentro do agronegócio, além de ser uma ferramenta importante na rotação de culturas. Entre os fatores que interferem significativamente no rendimento de grãos de milho as plantas daninhas merecem destaque, pois podem causar a redução de 80% no rendimento. É fundamental encontrar alternativas de controle em pós-emergência na cultura do milho, sobretudo com o aumento de plantas daninhas resistentes ao glifosato. Assim, o herbicida glufosinato de amônio pode ser uma alternativa de controle de plantas daninhas em pós-emergência no milho. Desta forma, o presente estudo tem por objetivo avaliar a resposta de híbridos de milho à diferentes doses de glufosinato de amônio aplicado em pós-emergência. O experimento foi conduzido na safra 2018/2019, em parcelas sub divididas, onde a parcela principal corresponde aos híbridos e as subparcelas as doses de glufosinato de amônio. O herbicida foi aplicado quando as plantas apresentavam de 4 a 6 folhas. As avaliações de fitotoxicidade foram realizadas aos 7, 14, 21 dias após a aplicação dos herbicidas, e o rendimento de grãos no final do ciclo da cultura. As avaliações de fitotoxicidade demonstram que os híbridos apresentam rápida recuperação da injúria causada pelo herbicida, pois aos 21 dias a maioria deles não apresentava mais sintomas visuais. A fitotoxicidade não afetou o rendimento de grãos. O glufosinato de amônio é um herbicida com potencial no controle de plantas daninhas em pós-emergência na cultura do milho.
DINÂMICA DO BANCO DE SEMENTES DE PLANTAS DANINHAS NO SOLO CONDUZIDO SOB SISTEMA DE PLANTIO DIRETO
O conhecimento do banco de sementes do solo presente nas áreas agrícolas é fundamental para a escolha das estratégias de manejo mais adequadas para o controle das plantas daninhas. O objetivo foi avaliar a viabilidade imediata de germinação das sementes de plantas daninhas do solo conduzido em sistema de plantio direto consolidado. O solo foi coletado na profundidade de 0 a 40 cm, estratificado: 0-10 cm, 10-20 cm e 20-40 cm. A viabilidade das sementes de plantas daninhas foi avaliada através da emergência de sementes viáveis em solo incubado em delineamento inteiramente casualizado com cinco repetições a 25ºC com fotoperíodo de 12 horas diário por 56 dias. Foram contabilizadas 11,2, 4,0 e 1,6 plantas daninhas nas profundidades de 0-10, 10-20 e 20-40 cm, respectivamente. Quatro espécies foram identificadas: Caruru (Amaranthus spp.) com 54%, buva (Conyza bonariensis) com 36%, picão preto (Bidens pilosa) com 8,8% e serralha (Sonchus oleraceus) com 1,2%. A profundidade de 0-10 cm apresenta maior quantidade de sementes com viabilidade imediata de germinação de plantas daninhas de caruru e buva no solo estudado. A serralha e picão preto apresentam menor quantidade de sementes com viabilidade imediata, contudo com distribuição uniforme em profundidade no solo.
A espécie Maranta sobolifera (Caetê) apresenta tolerância ao manejo químico e sua disseminação nas áreas agrícolas do oeste paranaense vem aumentado a cada ano. Porém, existem poucas informações sobre opções de manejo químico. Objetivou avaliar o controle da M. sobolifera utilizando diferentes doses de herbicidas aplicados isolados e em mistura em tanque em condições controladas e a campo. No experimento em vaso, as aplicações isoladas de glifosato (2160 g ha-1), carfentrazone (60 g ha-1), e 2,4-D (670 e 1340 g ha-1), além das misturas de [fluroxipir + triclopir] (320 + 960 e 480 + 1440 g ha-1), glifosato + carfentrazone (720 + 40 e 1080 + 60 g ha-1), glifosato + 2,4-D (1080 + 1340 g ha-1), e glifosato + [fluroxipir + triclopir] (720 + [320 + 960] e 1080 + [480 + 1440] g ha-1), foram as mais eficientes (>80%) aos 42 dias após a aplicação (DAA). Enquanto que a campo, as aplicações de glifosato (>3000 g ha-1), glufosinato (≥200 g ha-1), carfentrazone (≥ 60 g ha-1), saflufenacil (≥ 105 g ha-1), 2,4-D (≥ 1340 g ha-1) e a mistura comercial fluroxipir + triclopir (≥ 160 + 480 g ha-1) foram mais eficientes (>80%) a partir de 21 DAA. De modo geral, a M. sobolifera demonstrou tolerância ao glifosato e elevada sensibilidade ao glufosinato e a mistura fluroxipir + triclopir. O carfentrazone e o saflufenacil apresentaram-se mais eficientes em doses mais elevadas, além de que, apenas a mistura glifosato + carfentrazone (720 + 40 g ha-1) apresentou efeito sinérgico.
INFLUÊNCIA DO TIPO E DA QUANTIDADE DE PALHA SOBRE A SELETIVIDADE DO HERBICIDA FOMESAFEN APLICADO EM PRÉ-EMERGÊNCIA DO ALGODOEIRO
Resumo: O presente trabalho teve como objetivo avaliar a influência da quantidade de palha de feijão ou de aveia sobre a seletividade do herbicida fomesafen aplicado em pré-emergência do algodoeiro. Dois experimentos foram conduzidos simultaneamente em casa de vegetação em delineamento inteiramente casualizado, com quatro repetições. As unidades experimentais foram preenchidas com solo de classe textural franco argilo arenosa, pH de 5,9; 2,94% de MO e 320 g kg-1 de argila, a cultivar utilizada foi a FMT 705. Os tratamentos avaliados resultaram do arranjo fatorial 2 x 4, sendo que o primeiro fator representado por duas doses de fomesafen (0 e 500 g i.a. ha-1) e o segundo fator por quatro níveis de palha (0, 2, 4 e 6 t ha-1). No primeiro experimento, foi utilizada a palha de feijoeiro comum e no segundo experimento utilizou-se palha de aveia. Aos 30 dias após a emergência, realizou-se a coleta da parte aérea e das raízes das plantas de algodoeiro para determinação da massa seca. De maneira geral, notou-se que onde foi utilizada a palha de aveia foram observados os melhores resultados de crescimento do algodoeiro e menor injúria ao sistema radicular da planta. A palha de feijoeiro comum ao solo reduziu a massa seca da parte aérea e do sistema radicular das plantas de algodão. Este resultado mostrou que não se deve considerar apenas a quantidade de palha sobre solo, já que a cobertura proporcionada pelo material vegetal também influenciou na seletividade do herbicida fomesafen.
CONTROLE DE CAPIM-AMARGOSO EM RESPOSTA À APLICAÇÃO DE INIBIDORES DA ACCASE APÓS DIFERENTES PERÍODOS DE RESTRIÇÃO HÍDRICA
O estresse hídrico pode influenciar nos processos fisiológicos e na eficiência dos herbicidas nas plantas daninhas. Objetivou-se com este trabalho avaliar a eficiência de inibidores da enzima Acetil-CoA carboxilase (ACCase) no controle de capim-amargoso (Digitaria insularis) após diferentes períodos de restrição hídrica. Os tratamentos foram organizados em esquema fatorial (8x4). O fator A foi composto por períodos de restrição hídrica antes da aplicação dos herbicidas, sendo: zero; 2; 4; 6; 8; 10; 12 e 14 dias. O fator B foi composto pelos herbicidas cletodim (144 g i.a. ha-1), quizalofop-P-tefuril (72 g i.a. ha-1) e cletodim + quizalofop-P-ethyl (144 + 72 g i.a. ha-1), além das testemunhas não tratadas. As variáveis avaliadas foram o controle de capim-amargoso aos 14, 28 e 42 dias após a aplicação dos tratamentos (DAT) e a massa seca da parte aérea (MSPA) aos 42 DAT. Os dados foram submetidos à ANOVA e a análise complementar realizada por ajuste de regressões. O controle de capim-amargoso foi reduzido consideravelmente para ambos herbicidas conforme se aumentou do período de restrição hídrica antecedendo a aplicação. Quando realizada a aplicação sem restrição hídrica, o controle foi de aproximadamente 90% para todos herbicidas. Contudo, com 14 dias de restrição hídrica, o controle caiu para 15% para o herbicida quizalofop-P-tefuril e para 29% para o herbicida clethodim + quizalofop-P-ethyl. O herbicida clethodim apresentou maior tolerância à restrição hídrica, com 56,6% de controle quando aplicado após 14 dias de restrição hídrica.
SENSIBILIDADE DE ARROZ-DANINHO ORIUNDO DE REBROTE A IMAZAPYR + IMAZAPIC
O cultivo da soca do arroz é uma técnica na qual a rebrota é cultivada após a colheita, com objetivo de realizar duas safras sucessivas na mesma área. Essa prática tem o intuito de melhorar a produtividade e a rentabilidade do cultivo do arroz. Entretanto, este modelo agrava os problemas fitossanitários, tornando o controle de plantas daninhas mais complexo. O objetivo deste trabalho foi de avaliar a eficiência da mistura formulada de imazapyr + imazapic no controle de arroz-daninho oriundo de rebrote, simulando às condições de cultivo da soca de arroz. O experimento foi conduzido em casa de vegetação, em delineamento inteiramente casualizado com tratamentos dispostos em esquema fatorial 4 x 3. O primeiro fator correspondeu aos genótipos simuladores de arroz-daninho (SCSBRS Tio Taka; SCS116 Satoru, SCS121 CL, SCS122 Miura) e o segundo fator as doses de imazapyr + imazapic (0,0; 73,5 + 24,5 e 147 + 49 g ha-1 de i.a.). Avaliou-se a eficiência de controle aos 7, 14 e 28 dias após a aplicação, além da altura de plantas, número médio de folhas por perfilho e massa seca da parte aérea. O controle do rebrote de arroz-daninho com imazapyr + imazapic não foi satisfatório em nenhum período de avaliação. Contudo, a mistura formulada de imazapyr + imazapic suprimiu o crescimento dos genótipos SCSBRS Tio Taka, SCS116 Satoru e SCS122 Miura, independentemente da dose. Conclui-se que a aplicação de imazapyr + imazapic não foi eficiente no controle de rebrote de arroz-daninho.
BIOLOGICAL AND ECONOMIC EFFICIENCY OF GLYPHOSATE-CONTAINING HERBICIDE MIXTURES FOR PRE-PLANT BURNDOWN CONTROL OF CONYZA SPP. AND OTHER TROUBLESOME WEED SPECIES
Pre-plant burndown using herbicides is a key practice in no-till cropping systems, ensuring optimal crop sowing and early-growth conditions. Glyphosate (N-phosphonomethyl glycine) is a broad-spectrum, systemic herbicide commonly employed in pre-plant burndown treatments, as it allows for cheap, effective weed management. Since glyphosate-resistant weed populations are currently widespread in Brazil, at the present work glyphosate-containing tank-mixtures with either 2,4-D, flumioxazin, saflufenacil, or ammonium-glufosinate were sprayed in the field onto nutsedge (Cyperus spp.), arrowleaf sida (Sida rhombifolia L.), and glyphosate-resistant horseweed (Conyza spp.) populations, such that novel, cost-effective control options can be determined. Trials were conducted in the 2016/2017 growing season and employed a total of 10 herbicidal treatments plus an untreated check; herbicide rates followed label recommendations. Experimental units consisted of 15 m2 plots replicated four times, arranged as complete blocks. Weed control efficacy was determined from 7 to 42 days after spraying using a 0-100% grading scale, and was later combined with actual treatment costs to evaluate economic feasibility of these treatments in an agricultural setting. Glyphosate sprayed alone effectively eliminated nutsedge and arrowleaf sida populations, scoring the lowest cost per unit of control. Nonetheless, two- or even three-way tank-mixtures were required for satisfactory (>80%) glyphosate-resistant Conyza spp. control, allowing for a weed-free environment for summer crop seeding. Despite an increase in overall costs, tank-mixing herbicides with different modes of action should not be completely disregarded, especially in a scenario where resistance is likely to develop due to the repeated use of herbicides within the same mode of action combined with the lack of new herbicidal mode of action released into the market.
ALTERNATIVAS DE MANEJO QUÍMICO DE CAPIM RABO DE BURRO (Andropogon bicornis)
A interferência das plantas daninhas nas culturas vem causando problemas que refletem em diversas perdas. Vários métodos de controle são disponíveis, dentre eles, o químico é comumente utilizado pelos agricultores. O objetivo do trabalho foi avaliar a eficiência de diferentes herbicidas químicos, utilizados isolados e em associações, no controle de Capim Rabo de Burro (Andropogon bicornis) em dife­rentes estádios fenológicos. O experimento foi realizado em área própria, com infestação natural de Andropogon bicornis no município de São Miguel das Missões, estado do Rio Grande do Sul, durante os meses de setembro a novembro de 2019. O mesmo foi conduzido em delineamento blocos ao acaso, arranjado em esquema fatorial 2 x 10, com parcelas subdivididas e 3 repetições, totalizando 60 unidades experimentais. O fator A foi composto pela planta daninha Andropogon bicornis na fase de planta adulta e na fase de rebrote (intenso desenvolvimento vegetativo); e o fator B foi composto por 9 tratamentos herbicidas mais uma testemunha sem aplicação. Dentre os tratamentos utilizados a mistura de glifosato na dose de 1.440 g e.a. ha-1 em associação a herbicidas inibidores da ACCase (cletodim e/ou haloxifope-P-metílico), nas doses de 192 e 60 g e.a. ha-1, respectivamente, demonstraram ser uma ferramenta de alta performance no manejo de Andropogon bicornis, independente da fase desta planta daninha, desde que seja pulverizada a sequencial com herbicidas de ingrediente ativo paraquat em dose de 400 g e.a. ha-1 e S-metolacloro 1.920 g i.a. ha-1 nas doses de condições semelhantes de onde foi conduzido o experimento.
DESSECAÇÃO ACELERADA DE CAPIM-MARANDU COM A APLICAÇÃO SEQUENCIAL DE GLYPHOSATE E GLUFOSINATE
O capim-marandu pode ser uma alternativa no sistema integração lavoura-pecuária (ILP) considerando-se sua elevada produção de massa seca e maior tolerância a duas espécies de cigarrinha-das-pastagens. No entanto, a sua dessecação é mais lenta que a do capim-ruziziensis para uma mesma dose, sendo necessário acelerá-la para que a semeadura de cultivares precoces de soja ocorra na época recomendada. Assim, objetivou-se estimar as épocas de aplicação e as doses de glyphosate e glufosinate em dessecação sequencial de capim-marandu com e sem pastejo simulado para menor tempo de dessecação. Quatro ensaios foram instalados em casa-de-vegetação com delineamento em blocos casualizados com três blocos. Os tratamentos combinaram duas épocas de primeira dessecação (20 e 10 dias antes da data estabelecida como sendo de semeadura da soja – DAS) e quatro épocas de segunda dessecação (7, 5, 3 e 0 DAS) e uma testemunha sem herbicidas. Cada ensaio combinou aplicações sequenciais dos herbicidas glyphosate (g ha-1 de e.a.) e glufosinate (g ha-1 de i.a.) (1.625/600 e 975/400) e duas condições de pastejo simulado (com e sem corte). Conclui-se que a dessecação pode ser acelerada para 10 DAS apenas quando aplicadas as maiores doses de glyphosate (1.625 g e.a. ha-1) e de glufosinate (600 g ha-1) em capim-marandu sem pastejo simulado, podendo ser a segunda dessecação realizada de 7 a 0 DAS. No pastejo simulado, os resultados são semelhantes, embora a aplicação de glufosinate possa ser realizada também aos 7 DAS com as menores doses dos herbicidas.
ASSOCIATION OF HERBICIDES FOR THE MANAGEMENT OF WEEDS IN CORN
Corn is an important crop for agriculture, playing a fundamental role in animal and human feed and energy production. Therefore, the purpose of this study was evaluate the effectiveness, selectivity and effects on corn physiological and productive characteristics after herbicide application either isolated or in tank mix. The procedure adopted was randomized blocks design, with four replications each. The treatments, glyphosate, [atrazine + simazine], nicosulfuron, mesotrione, tembotrione, plus a weeded control were used alone or in a tank mixture. It was evaluated the herbicide phytotoxicity in AG 9025 PRO3 hybrid corn, as well as the weed control of alexander grass and crabgrass at 7, 14, 21 and 28 days after treatment (DAT). At 50 DAT, variables related to the grain physiological characteristics were also measured. Finally, during harvest, grain yield was determined. All evaluations showed that phytotoxicity caused by herbicides was not visually perceptible in AG 9025 PRO3 corn hybrid. The control was effective in treatments that presented in tank mix treatments glyphosate with nicosulfuron and tembotrione. The physiological characteristic affected after herbicide application was photosynthesis, which, when compared to other treatments, showed better results with nicosulfuron and mesotrione. Herbicides did not interfere in corn grain yield. Glyphosate associated with other herbicides used in corn crops shows to be a valuable practice to improve and accelerate the weed control studied with selectivity to the crop.
Copyright (c) 2021 Brazilian Herbicide Journal
CONTROLE DE PLANTAS DANINHAS NA CULTURA DA CANOLA COM DIFERENTES HERBICIDAS
A interferência das plantas daninhas na cultura da canola ocasiona prejuízos, como a redução da produção de grãos ou mesmo a qualidade desses. Objetivou-se com este trabalho avaliar a eficácia de herbicidas aplicados para o controle de plantas daninhas em canola e o efeito sobre o rendimento de grãos da cultura. Foram instalados dois ensaios a campo, um (I) na safra 2018 e outro (II) 2019, em delineamento experimental de blocos ao acaso, com 17 tratamentos e quatro repetições. Os híbridos estudados foram: canola Hyola 571 CL e a Hyola 575 CL (Clearfield®). Nos dois ensaios foram testados os herbicidas: iodosulfuron, imazethapyr+imazapic, imazapic+imazapyr, imazethapyr, pyroxsulam, nicosulfuron, imazamox, diclosulam, imazaquin, chlorimuron-ethyl, sulfentrazone, sulfentrazone+diuron, pendimethalin, metsulfuron-methyl e flumioxazin, mais duas testemunhas, uma capinada e outra infestada. As plantas daninhas presentes na área experimental foram azevém e nabo nas densidades médias de 14 e 27 plantas m-2, respectivamente. Aos 7, 14, 21, 28 e 35 dias após aplicação dos tratamentos (DAT) foi avaliado o controle das plantas daninhas. Após a colheita determinou-se o peso de mil grãos (g) e a produtividade de grãos (kg ha-1). O imazapic+imazapyr e o nicosulfuron apresentam o melhor controle do azevém nos dois ensaios. O iodosulfuron, imazethapyr+imazapic, imazapic+imazapyr, nicosulfuron, diclosulam, chlorimuron-ethyl e metsulfuron-methyl foram os tratamentos que melhor controlaram o nabo nos ensaios I e II. As maiores produtividades de grãos de canola foram obtidas com a aplicação de nicosulfuron e imazaquin para a Hyola 571 CL e de imazethapyr para o híbrido Hyola 575 CL.
SELETIVIDADE DE HERBICIDAS PARA BATATA-DOCE
Nas áreas maiores e de maior tecnificação do sistema de produção da batata-doce, as plantas daninhas são controladas com herbicidas. Contudo, existem apenas dois herbicidas registrados para a cultura no Brasil. Objetivou-se estudar a seletividade de diferentes herbicidas para a cultura da batata-doce, em função do genótipo e da dosagem de cada produto. Dois experimentos foram desenvolvidos em condições de campo, com as cultivares Canadense e Brazlândia Roxa, um para cada cultivar. O delineamento experimental foi o de blocos ao acaso, com 13 tratamentos e três repetições. Os tratamentos consistiram de seis herbicidas pulverizados em duas dosagens (clomazone 0,54 e 1,08 kg ha-1, flumioxazin 0,02 e 0,03 kg ha-1, linuron 0,72 e 0,99 kg ha-1, metribuzin 0,36 e 0,48 kg ha-1, oxadiazon 0,25 e 0,50 kg ha-1 e sulfentrazone 0,250 e 0,50 kg ha-1) e uma testemunha sem aplicação. Avaliações de fitointoxicação, população de plantas, comprimento da haste principal, produtividade de raízes tuberosas (descarte, comercial e total) e controle de plantas daninhas foram realizadas. A interação cultivares e tratamentos de herbicidas não foi significativa para nenhuma característica avaliada. Entre os herbicidas, sulfentrazone na maior dosagem foi o mais fitotóxico para batata-doce com notas de 40% a 44%. Todavia, nenhum dos tratamentos de herbicida afetou negativamente a produtividade de raízes tuberosas. Concluiu-se que, as cultivares Canadense e Brazlândia Roxa possuem resposta semelhante aos herbicidas testados; e os herbicidas clomazone, flumioxazin, linuron, metribuzin e oxadiazon são promissores para uso na cultura da batata-doce.
SELETIVIDADE DE HERBICIDAS COM ATIVIDADE RESIDUAL EM CEBOLA CULTIVADA EM SEMEADURA DIRETA
O sistema de semeadura direta pode ser uma alternativa para reduzir custos e mão-de-obra na produção de cebola, pois não requer as etapas de produção e transplante das mudas. No entanto, esse sistema resulta em uma interferência precoce das plantas daninhas, alongando o período crítico de prevenção à interferência. Assim, o objetivo desta pesquisa foi avaliar a seletividade de aplicações de herbicidas com atividade residual em cebola. Três estudos foram realizados em casa de vegetação. O primeiro conduzido em esquema fatorial 5 x 4, avaliando os herbicidas flumioxazin, oxadiazon, oxyfluorfen, pendimethalin e diuron em 0, 30, 60 e 100% da dose de referência do herbicida. No segundo estudo, dois herbicidas, pendimethalin e diuron, foram aplicados em três estádios de desenvolvimento da cebola: pré-emergência total com aplicação após a semeadura, aplicação no final da germinação, 15 dias após a semeadura e aplicação no estabelecimento da cebola, aos 21 dias após a semeadura. Um terceiro experimento foi realizado comparando a seletividade do S-metolachlor à cebola. A aplicação de herbicida na fase de estabelecimento da cebola foi mais seletiva. Os herbicidas oxadiazon, oxyfluorfen e flumioxazin não apresentaram uso potencial na aplicação inicial devido à alta fitotoxicidade. A aplicação de pendimethalin e S-metolachlor no final do estabelecimento da cebola foi seletiva e mais uma alternativa ao controle de plantas daninhas no sistema de produção de cebola por semeadura direta.
HERBICIDES TO CONGO SIGNAL GRASS SUPPRESSION IN INTERCROPPING WITH CORN
The corn intercropping with Congo signal grass (Brachiaria ruziziensis) has rapidly raised in South and Center-West of Brazil. However, the uncertainty about forage interference on corn yield has led growers to use herbicides to suppress Congo signal grass. Our objective was to evaluate herbicide treatments in sub-doses in suppression of Congo signal grass growth in a corn/Congo signal grass system intercropping. A greenhouse experiment was conducted to evaluate forage intoxication by herbicides to select the best treatments. Subsequently, a field experiment was conducted to investigate the suppression of some sub-dose herbicide treatments based on corn yield and Congo signal grass growing in two stages of application. The experimental arrangement was a 9x2+3 factorial in a randomized block design, with eight replications. Treatments applied in more than 3 tillers of Congo signal grass demonstrated less injury levels than 1 tiller stage. In the field, forage intoxication was not higher than 56% and nicosulfuron treatments provided higher suppression levels than mesotrione treatments. Based on avoiding corn yield losses of 25% and on greater Congo signal grass biomass on off-season, we could conclude that mesotrione (48 or 60 g ha-1) and atrazine (1200 g ha-1) applied on 1-3 tiller stage; and mesotrione (60 g ha-1), mesotrione+atrazine (60+1200 g ha-1) and atrazine (1200 g ha-1) applied on more than 3 tillers are efficient treatments.
Amaranthus hybridus MANAGEMENT IN CROP-LIVESTOCK SYSTEMS IN SOUTHERN RIO GRANDE DO SUL
Recently, soybean cultivated area has risen in Brazil and so had total production. In the Rio Grande do Sul state (RS), soybean production is also increasing and its grown after beef production during the cold season, a production model that contributes to improve land usage during the twelve months of the year, increasing farmers’ income and, when well handled, it can also contribute to integrated weed management. Despite that, the presence of hard-to-control broadleaved weeds like Amaranthus hybridus in RS soybean fields its on the rise. Therefore, this study objective was to evaluate the efficiency of pre- and post-emergency herbicides, and different management programs on Amaranthus hybridus populations. The study was composed by four experiments, two under controlled conditions in a greenhouse and two on a farm in Cerrito, RS, that integrates soybean production with cattle livestock. The experiments show that some biotypes are tolerant to glyphosate and ALS inhibitors (imazethapyr and chlorimuron-ethyl), and that the use of the pre-emergence herbicides imazethapyr + flumioxazin, metribuzin, s-metolachlor e sulfentrazone + diuron contributes to the biotypes management. It was also verified that the ryegrass burndown and its complementation with contact and pre-emergence herbicides are determinant factors to control A. hybridus. Yet, the results point that under water deficit situations, straw presence can reduce the efficiency of some pre-emergence herbicides.
INTERFERENCE OF HERBICIDES IN THE MILLET DEVELOPMENT
Millet is an annual hot season grass that has an upright and tall size, used as a food source in livestock and as a soil cover in the no-tillage system. As it is a culture of low economic value, information about it is rare. The objective of the work was to verify the selectivity of the herbicides atrazine and 2,4-D applied alone or in association at different times in the millet culture. The experiment was carried out in the field in 12 m2 plots and randomized block design, with 10 treatments and four replications. The treatments were: 1- control without weeding; 2- weed control; 3- atrazine in pre-sowing; 4- post-sowing atrazine; 5- atrazine in V4; 6- 2,4-D in V4; 7- 2,4-D (150% of the dose) in V4; 8- atrazine in pre-sowing + 2,4-D in V4; 9- atrazine in post-sowing + 2,4-D in V4, 10-atrazine + 2,4-D in V4. The number of plants per linear meter, phytotoxicity at 7, 14, 21 and 28 days after application, plant height and shoot dry weight were evaluated. There was a reduction in the plant stand with application of atrazine in pre and post-sowing. The herbicide 2,4-D showed higher levels of phytotoxicity, lower plant height and lower dry mass production in all evaluations. The herbicide atrazine presents itself as a good alternative for weed control in the millet culture when applied in V4.
Controle de Digitaria insularis em função da aplicação de pyroxasulfone sobre diferentes níveis de palha de soja e de milho
A palha sobre o solo, comum em áreas onde o plantio direto foi adotado, pode se tornar uma barreira para que os herbicidas aplicados atinjam seu destino, o solo. Não há informações sobre a capacidade do novo herbicida pyroxasulfone, quando aplicado sobre a palha, de superar essa barreira e promover controle eficaz das plantas daninhas em pré-emergência. Assim, objetivou-se avaliar a eficácia do pyroxasulfone no controle das plantas daninhas quando aplicado em diferentes níveis de palha comparando-o com herbicidas disponíveis no mercado brasileiro. Dois experimentos distintos foram conduzidos em casa de vegetação, um com palha de soja e outro com palha de milho. Os tratamentos foram compostos pela aplicação de pyroxasulfone (100 g ha-1), S-metolachlor (1960 g ha-1) e trifluralin (1125 g ha-1) sobre diferentes níveis de palha de soja e de milho (0, 1, 3 e 5 t ha-1). A planta daninha utilizada foi o capim-amargoso (Digitaria insularis). Os herbicidas foram aplicados após a semeadura e posicionamento dos níveis de palha sobre o solo. Os vasos foram irrigados por aspersão, recebendo uma lâmina de 30 mm de água. A eficácia de controle dos tratamentos foi verificada aos 7, 14, e 28 dias após a aplicação. Observou-se que o pyroxasulfone apresentou a capacidade de transpor a palha sobre o solo após uma precipitação de 30 mm, mantendo controle das plantas de capim-amargoso semelhante à aplicação no solo sem palha. Sob as mesmas condições, o S-metolachlor e a trifluralin reduziram sua eficácia no controle de capim-amargoso quando aplicados sobre maiores níveis de palha.
CHEMICAL CONTROL OF DONKEY-TAILED GRASS IN DIFFERENT DEVELOPMENT STAGES
Donkey-tailed grass is a poaceae, considered a recent weed in soybean crops and its increasing the infestation’s levels and the difficulty of control. Thus, this study aimed to evaluate the effectiveness of different doses of herbicides applied alone or mixed, to control dunk-grass at different stages of development. Three experiments were conducted, first one in greenhouse with new plants and two experiments in the field with clumps. The treatments were glyphosate; fluazifop; sethoxydim; fenoxaprop; clethodim; quizalofop; haloxyfop; pinoxaden, nicosulfuron; glufosinate and mixtures of glyphosate with clethodim, quizalofop, haloxyfop or sethoxydim. Treatments with glyphosate, alone or mixed, showed higher levels of control in all experiments. Glyphosate, glufosinate, clethodim, haloxyfop and sethoxydim were effective in the control of new plants. For the clumps’ management, glyphosate and haloxyfop alone demonstrated efficiency greater than 90% independent of the dose and clethodim and sethoxydim in the highest dose. The herbicides pinoxaden and nicosulfuron are not alternatives to donkey-tailed grass control.
WEED PHYTOSOCIOLOGY SURVEY IN FLOODED RICE CULTIVATED ON CLEARFIELD® SYSTEM
Weed management is essential for obtaining high grain yields in irrigated rice. In this study, the objectives were to map, quantify and to evaluate resistance occurrence of weeds in irrigated rice production areas using the Clearfield® (CL) system in the state of Rio Grande do Sul (RS). For this, a phytosociological survey was carried out by means of georeferenced collections of soils in 36 farms with the cultivation of irrigated rice in 16 cities in RS. The soil samples were placed in polyethylene trays with an area of 792 cm2 and arranged in a greenhouse, in order to allow the emergence of weeds during the period from October 2018 to June 2019. The weeds present were quantified and identified at the genus level, with the help of specialized bibliography. The variables analyzed were frequency, relative frequency, density, relative density, abundance, relative abundance and importance value index. A total of 38 genus were identified, distributed in 20 botanical families, and the most representative were Poaceae, Cyperaceae and Asteraceae. The genus Cyperus, Echinochloa, Oryza and Lolium had the highest indexes of importance value. The first three showed high frequency and wide distribution in the irrigated rice producing regions. The areas with the cultivation of irrigated rice, in the CL system, presented a high diversity and distribution of weeds. Weeds of the genus Cyperus have higher values of relative frequency, density and abundance, as well as a high importance value index.
Copyright (c) 2020 Brazilian Herbicide Journal
DETECÇÃO DE RESÍDUO BIODISPONÍVEL DE S-METOLACHLOR NO SOLO PELO MÉTODO DE BIOENSAIO
O uso de herbicidas aplicados no solo em pré-emergência, como o S-metolachlor, pode causar efeitos negativos em culturas sensíveis posteriormente instaladas na área, devido ao seu efeito residual. No entanto, a seleção de plantas bioindicadoras viabiliza o estudo do comportamento deste herbicida no solo pela técnica de bioensaio. Diante desse cenário, o objetivo desse estudo foi analisar os níveis de injúrias e redução de biomassa em plantas bioindicadoras na presença de resíduo biodisponível de S-metolachlor em solo argiloso. Utilizou-se quatro potenciais espécies bioindicadoras: pepino (Cucumis sativus), rabanete (Raphanus sativus), sorgo (Sorghum bicolor) e abobrinha (Cucurbita pepo), e seis doses do S-metolachlor (0; 180,5; 360; 720; 1440 e 2880 g ha-1). As plantas foram avaliadas 21 dias após a semeadura (DAE) quanto aos níveis de injúria e porcentagem de biomassa da matéria seca da parte aérea com relação ao tratamento controle, sem aplicação do herbicida. O C. sativus se comportou como uma espécie extremamente sensível, com redução de 100% em matéria seca a partir da metade da dose recomendada (1440 g ha-1) do herbicida e sendo a única espécie a apresentar mais do que 80% de controle. O S. bicolor também apresentou alta sensibilidade, sendo a espécie que apresentou o menor valor de dose para redução de seu crescimento, precisando de apenas 5% (157,95 g ha-1) da dose recomendada para reduzir em 80% seu crescimento e atingindo 50% de controle com uma dose aproximada de 14% (400 g ha-1) da dose recomendada. As espécies R. sativus e C. pepo, não apresentam potencial como plantas bioindicadoras devido à alta tolerância ao herbicida. Entre as espécies avaliadas, C. sativus e S. bicolor apresentaram maior potencial para uso como plantas bioindicadoras em estudos comportamentais em solo contaminado com resíduo biodisponível de S-metolachlor e/ou para produtores realizarem testes rápidos com bioensaios analisando o carryover deste herbicida no solo.
INTERACTION AND EFFICACY OF SAFLUFENACIL AND GLYPHOSATE TANK MIXTURES
Repetitive adoption of glyphosate and in high rates have selected resistant biotypes of weeds, as well as it has contributed to selecting glyphosate-tolerant species. The most common solution for that is the inclusion of alternative herbicides in the system of production, applied isolated or in the tank mixtures. Therefore, this work was developed with the objective of evaluating the efficacy and interaction of glyphosate-saflufenacil tank mixtures for controlling two weed species. Two independent experiments were developed, evaluating one monocotyledonous weed species (sourgrass – Digitaria insularis) and one dicotyledonous (morning glory – Ipomoea triloba). Treatments were consequence of a factorial combination 4x4, i.e., four rates of glyphosate (0, 360, 720 and 1,080 g ha-1) and four rates of saflufenacil (0, 21, 42 and 63 g ha-1). In all the trials, experimental design adopted was randomized blocks with five replications. Among the combinations, mixture was considered additive for sourgrass and morning glory. These mixtures may be considered as important tools to control resistant and tolerant weeds in management systems, being saflufenacil an excelent molecule to be applied with glyphosate.
INTERACTION OF METRIBUZIN AND NITROGEN IN CARROT CROP
Nitrogen is the most extracted nutrient in carrot fields. However, high N doses can favor thegrowth of aerial part in relation to the root of the plant. The application of metribuzin canalter the biomass partition in favor of the roots. Thus, the objective of this research was toevaluate the effect of post-emergence metribuzin application and its interaction withnitrogen on the axial and radial growth and yield of carrot roots. Three field experimentswere carried out in different growing sites. Experimental design was a randomized completeblock design with four repetitions, in a 2x3 factorial scheme, with two doses of metribuzin(0 and 432 g ha-1) and three N doses (0,30 and 90 kg ha-1). Root length and diameter, drymatter mass of shoot (MSPA) and root of plants and root productivity were evaluated.There was no interaction between metribuzin and nitrogen in the studied variables. Ingeneral, there was no influence of metribuzin and N on MSPA and root length. Metribuzinreduced the dry matter mass of the carrot root as a consequence of the reduction in carrotroot diameter. However, it did not influence the commercial and total yield of the carrot.The application of metribuzin associated with N fertilization does not influence the axial orradial growth of the carrot root and consequently does not alter the yield of the carrot.
PRE-EMERGENT HERBICIDE APPLICATION PERFORMED AFTER CROP SOWING FAVORS PIGWEED (AMARANTHUS SPP.) AND WHITE-EYE (RICHARDIA BRASILIENSIS) CONTROL IN SOYBEANS
The use of pre-emergent herbicides offers a promising alternative for proper management of difficult-to-control weed species in soybeans, such as white-eye (Richardia brasiliensis Gomes), a glyphosate-tolerant species, and weeds in the Amaranthus genus (commonly referred to as pigweeds). Here, we aimed at determining whether weed control efficacy and crop selectivity are altered when pre-emergent herbicide applications take place either prior to, or right after crop sowing. To this end, field trials were conducted employing 10 preemergent herbicide treatments (plus an untreated control as well as an untreated, weed-free treatment), replicated four times and sprayed either before, or right after soybean sowing. Results indicate that the actual timing of pre-emergent herbicide spraying relative to soybean sowing significantly changed the weed control efficiency set forth by most herbicide active ingredients tested, with no change to their selectivity to crop plants whatsoever. Some herbicides (e.g. diclosulam, mesotrione, flumioxazin, and a flumioxazin + imazethapyr mixture), however, were equally effective for controlling white-eye and pigweeds regardless of application timing. Moreover, the only herbicide treatments allowing for satisfactory (>70%) control of all target weed species (white-eye, pigweeds, and black oats, Avena strigosa Schreb.) were flumioxazin and a flumioxazin + imazethapyr mixture. Spraying performed after sowing resulted in average yield gains of over 600 kg ha-1 relative to pre-sowing applications, possibly owing to better control of broadleaves. Altogether, this information is useful to soybean producers, as it does not lead to an increase in overall costs; instead, it only affects the timing of entry into the area for pre-emergent herbicide application.
BIOCHAR AS AN ATTENUANT TO THE HERBICIDES PHYTOTOXICITY IN PRE-SPROUTED SEEDLINGS OF SUGARCANE
The objective of this work was to evaluate the effect of biochar on the sensitivity of presprouted seedlings (MPB) of sugarcane to the clomazone, imazapic and indaziflam appliedin pre-planting alone or in combination. Two varieties of sugarcane (RB 975952 and RB985476) were evaluated. The experimental design was completely randomized with 4replications, using a 9 x 2 factorial scheme, with nine treatments (imazapic 52.5 and 200 gia ha-1, clomazone 1000 g ia ha-1, indaziflam 100 g i.a. ha-1, associations of imazapic +clomazone (52.5 + 600; 52.5 + 1000; 200 + 600 and 200 + 1000 g ia ha-1 and control) andthe presence or absence of biochar in the planting furrow pre-sprouted. The variety RB985476 showed sensitivity to the herbicides clomazone and imazapic in pre-planting. Thetoxicity caused by the herbicides imazapic + clomazone decreased due to the effect ofbiochar. Regarding the RB 975952 variety, sensitivity to clomazone alone and in themixture with imazapic was verified, being the biochar effective in reducing phytotoxicity.Indaziflan was selective for the two varieties of MPB’s. The biochar acted more effectivelyfor the clomazone alone or in a mixture with imazapic, being ineffective for the herbicideimazapic alone.
EFFECT OF THE APPLICATION OF SUPPOSEDLY ANTAGONISTIC HERBICIDES ON RICE PLANTS SUSCEPTIBLE TO ACCASE INHIBITORS
The control of weedy rice has been widely studied in weed science. However, gene flow from Clearfield rice (CL) to weedy rice has damaged the efficiency of the CL production system. A new rice crop that is resistant to ACCase inhibitor herbicides will be launched in the next year on the market, representing another tool for managing weedy rice in irrigated rice crops. In addition to using this tool, there is a need to increase the spectrum of herbicide treatments to control the diversity of weed species in irrigated rice crops. This study aimed to elucidate the effect of latifolicidal herbicides on the graminicide action of quizalofop on cultivated rice as an indicator plant in the simulation of weedy rice. An experiment was carried out in a greenhouse at the Epagri – Experimental Station of Itajaí, Santa Catarina, Brazil. There was a reduction in the efficiency of rice control for all evaluated doses of quizalofop associated with 2,4-D.
PHYSICAL-CHEMICAL COMPATIBILITY OF DIFFERENT DOSES AND MIXTURES OF HERBICIDES
The maintenance of the productivity of commercial crops is dependent on the use of phytosanitary products, but information about the interaction between them when used in mixture is restricted. The objective was to evaluate the physical properties, droplet spectrum and the physicochemical compatibility of mixtures with different doses and mixtures of herbicides. The treatments consisted of combining a formulation of the herbicide glyphosate with two commercial products formulated with the herbicide atrazine. The syrups were evaluated by the static method of physicochemical compatibility, obtaining descriptive tables regarding the aspects of homogeneity/heterogeneity. The measurements of the surface tension and contact angle were performed for one minute using the droplet method to determine the surface tension kinetics and the sessile droplet method to determine the contact angle. The evaluated parameters of the droplet spectrum produced by each treatment were the median volumetric diameter, the uniformity coefficient and the percentage of volume in droplets with diameters less than 100 μm. Constant agitation of the phytosanitary syrup before and during application is essential to reduce problems of incompatibility between products. The spectrum of droplets can vary according to the composition of the spray solution and the dose of the product used.
EFFECT OF SELENIUM AS A CHEMICAL PROTECTOR ON THE SELECTIVITY OF HERBICIDES APPLIED IN POST EMERGENCY FROM Urochloa decumbens
Some substances can be used as chemical protectors to increase the tolerance of crops to herbicides, including some micronutrients such as selenium. The use of herbicides in pastures has been increasingly used for weed management, this work aimed to evaluate selenium as a chemical protector in the selectivity of herbicides applied in post-emergence in U. decumbens. Three experiments were carried out in a greenhouse, in a 5x2 factorial scheme, five doses of herbicides and in the presence or not of selenium (Se) (25 g ha-1) applied via soil, in a completely randomized design, with five replications. The treatments are composed using the herbicides ametryn (0, 500, 1000, 1500 and 3000 g a.i. ha-1), ammonium-glufosinate (0, 75, 150, 300 and 600 g i.a. ha-1) and carfentrazone-ethyl (0, 5, 10, 20 and 40 g a.i. ha-1) and a treatment without herbicide application. They were evaluated at 3, 7, 14, 21 and 28 days after the application of treatments (DAA), phytointoxication and electron transport flow (ETR) and at 28 DAA plant height and shoot dry biomass. In general, there was an increase in plant phytoxication due to the doses of all herbicides studied. The application of Se, in turn, provided lower levels of phytointoxication, and consequently lower reductions in ETR, height and dry biomass when compared to plants not treated with Se. Thus, it is concluded that Se has potential use as a protector for these applied in post-emergence in U. decumbens.
EFFECT OF EXPOSURE TIME TO DIQUAT FOR CONTROL OF SUBMERSED AQUATIC PLANTS AND DEVELOPMENT OF A NEW EFFECTIVE EVALUATION TABLE
The objective of this study was to evaluate the time of exposure to diquat in the control of Egeria najas, E. densa (Planchon) and Hydrilla verticillate (L.F.) Royle, and use of a new evaluation table to analyze the effectiveness of submerged aquatic plants. For this, concentrations were used 0.2; 0.8 and 1.6 mg L-1 of diquat and a control (without herbicide application). The 10 cm plants remained exposed for 5, 15, 30, 60, 240, 480, 720 e 1440 minutos. They were then transferred to plastic containers with 1,0 L of water and 200g of sand for 56 days. Efficacy was assessed by signs of toxicity at 7, 15, 21, 28, 35, 42, 49, and 56 days post application (AAD) in new assessment table for submerged aquatic plants. The E. densa showed greater sensitivity to diquat with 100% control in the three concentrations, being in 0.2 mg L-1 from 240 minutes and in 0.8 and 1.6 mg L-1 at all times exposure. For H. verticillata 100% control occurred at the three concentrations, at 0.2 mg L-1 at 720 and 1440 minutes at 49 and 56 AAD respectively. In 0.8 mg L-1, 100% control occurred after 240 minutes and in 1.6 mg L-1 after 30 minutes. For E. najas, 100% control was achieved in 0.8 mg L-1 and 240 minutes and in 1.6 mg L-1 in 15 minutes, 8 and 24 hours in 56 AAD. The exposure time of 240 minutes and the concentration of 0.8 mg L-1 of diquat showed excellent control of the three submerged aquatic plants. The table of signs of toxicity developed for control evaluation was essential for the standardization of the results obtained.
FLUAZIFOP-P-BUTYLIC AS GROWTH REGULATOR FOR THREE TURFGRASSES SPECIES
The application of plant regulators reduces plant height without affecting the high quality of the treated area, without causing damage to the density of plants and without causing visible damage to the lawn. Thus, the objective was to evaluate the use of the herbicide fluazifop-p-butyl as a growth regulator for three species of grasses (bahia grass - Paspalum notatum; emerald - Zoysia japonica and blanket grass - Axonopus compressus) depending on the luminosity. The work was carried out in a completely randomized experimental design, with the treatments arranged for each grass species in a sub-plot scheme, in which the plots constituted the two conditions of light (100 and 70%) and the sub-plot the application of the herbicide (125 g ai ha-1), in four replications. After 15 days after application (DAA), evaluations were carried out by measuring the height of the plants, and their lateral growth inside the box. These assessments were repeated every 15 days, up to 45 DAA. On that occasion, the dry masses of the aerial part and roots of the plants were determined, after drying the materials in an oven with forced air circulation at 70oC for at least 96 hours. The herbicide fluazifop-p-butyl at a dose of 125 g a.i. Under 70% of light, fluazifop-p-butyl was more effective in regulating the growth of emerald grass, followed by blanket grass and bahia grass, up to 45 days after application.
CONTROL OF VOLUNTARY SOYBEAN PLANTS WITH HERBICIDES RECOMMENDED FOR COTTON
In part of the Midwest region of Brazil, cotton has been grown in second crop, sown after soybean harvest. In these areas, the occurrence of voluntary soybean plants has been common, interfering in the development of cotton crop. In this sense, the objective of this work was to evaluate the effectiveness of herbicides applied post-emergence in cotton for the control of voluntary soybeans containing different transgenics. Two experiments were carried out in a greenhouse, using a soybean cultivar with Liberty Link® technology (LL®), which confers tolerance to glufosinate, and the other Roundup Ready® (RR®) cultivar, which has tolerance to glyphosate. In both experiments, a randomized completely block design was used, in a 7 x 2 factorial arrangement, with 4 replications. The first factor consisted of herbicides registered for cotton: 2,4-D, dicamba, glyphosate, pyrithiobac, trifloxysulfuron, S-metolachlor, in addition to a control without application; while the second factor consisted of the association or not with glufosinate. To assess the performance of herbicide treatments, evaluations were made of the percentage of control, height and shoot dry mass of soybean plants. For LL® voluntary soybeans, dicamba and glyphosate alone, in addition to the association of glufosinate with dicamba, 2,4-D or glyphosate, they consisted of the most effective treatments, providing control levels above 80.0%. For RR® soybeans, dicamba, trifloxysulfuron and 2,4-D isolated showed efficacy in the control of voluntary plants, with increases in control levels being seen when the addition of glufosinate was applied to the spray solution of these herbicides.
VIABILITY OF WEED SEEDS IN VARZEA SOIL WITH IRRIGATED RICE
The soil weed seed bank is very dynamic and affected by several soil, plant management factors and environmental conditions. In this study, the immediate viability of weed seed germination in floodplain cultivated with flooded rice. Three depths of soil were used: 0-10 cm, 10-20 cm and 20-40 cm. In laboratory conditions, 800g of soil from each depth in five replications were placed in 20 cm high cut pet bottles, and subsequently placed in an incubator at 25ºC with 12 hours of photoperiod. The moisture content of the soil was monitored for weight loss, and when necessary, water was added. The experiment lasted 63 days with weekly counting and identification of emerged weeds. Four weed species were observed: ryegrass (Lolium multiflorum Lam.), malta cross (Ludwigia longifolia DC.), green carpet (Callitriche deflexa Engelm) and red rice (Oriza sativa L.). The emergence of plants was greater in the 0-10 cm depth until 42 days. There was dominance in the emergence of Callitriche deflexa Engelm plants over other species at a depth of 10-20 cm (average 121.6 plants). The 0-10 cm depth of soil has the greatest diversity of viable weed seeds. The 10-20 cm depth of soil provides greater accumulation of viable Callitriche deflexa Engelm seeds. The viability of weed seeds is disadvantaged in the 20-40 cm depth of soil.
HERBICIDES ASSOCIATIONS FOR BURNDOWN PRIOR SOYBEAN SOWING
In the soybean crop, weed resistant to glyphosate, such as horseweed and ryegrass, are difficult to control, making it necessary to associate other herbicides with different mechanisms of action. The objective of the study was to evaluate the influence of the association of herbicides to control glyphosate resistant weed in the soybean pre-planting desiccation and crop development and yield. The experiment was carried out in the 2018/2019 crop year, in an agricultural area that spent the winter fallow. The experiment used a randomized block design with eight replications. The experimental treatments consisted of three different combinations of herbicides applied in pre-planting of the soybean crop, 40 days before sowing the cultivar TMG 7062 IPRO: glyphosate + sethoxydim, glyphosate + 2,4-D + sethoxydim and glyphosate + 2,4-D. The associations of glyphosate with the herbicides 2,4-D and setoxidim in the pre-sowing desiccation of soybean provided greater control of broad and narrow leaf weeds, respectively. No synergism or antagonism effects were found in the herbicide associations, only addition effect improving the control. The different pre-planting desiccation treatments provided no effect on the Falker chlorophyll index, nor on the grain yield and its components.
MANAGEMENT OF VOLUNTARY SOYBEAN INFESTING WITH BEAN THE HERBICIDE ETHOXYSULFURON
he sowing of beans after soybean harvest can be a problem since the voluntary plants ofthe crop emerge after harvesting and compete with beans. The herbicide ethoxysulfuron hasbeen used for the management of different species of weeds, among them the voluntaryweed soybean in the cultivation of beans. Therefore, this study was developed with theobjective of evaluating the selectivity and effectiveness of different doses of ethoxysulfuronapplied to common bean for the control of voluntary soybeans. The experiment wasinstalled in a randomized block design, with four replications. The tested treatments were:0, 12, 24, 36 and 48 g ha-1 of active ingredient of ethoxysulfuron. At 10, 20 and 30 daysafter application of the treatments (DAT), the control of voluntary soybean andphytotoxicity to the IPR Tuiuiú bean cultivar were visually evaluated. In the bean harvest,the mass of a thousand grains (g) and grain yield (kg ha-1) were determined. The increase inethoxysulfuron doses contributed to the increase in the control efficiency of voluntarysoybean infesting beans. The highest phytotoxicities to common bean cultivar IPR Tuiuiúwere caused by the use of the highest doses of ethoxysulfuron. The dose of 25.8 g ha-1 ofethoxysulfuron caused the highest grain yield of the bean cultivar IPR Tuiuiú, with controlof 98.9% of the voluntary soybean and phytotoxicity around 21%.
CULTURAL AND CHEMICAL CONTROL OF Conyza spp. IN CORN INTERCROPPED WITH Urochloa ruziziensis
Integrated weed management practices to control fleabane (Conyza spp.) have been essential in integrated crop production systems, such as corn (Zea mays) associated with Congo signal grass (Uruchloa ruziziensis). The objectives of these studies were to evaluate the efficacy of Congo signal grass covering on fleabane suppression and to evaluate different chemical control options to control fleabane during the production of Congo signal grass. The first experiment was conducted after the corn harvest integrated with Congo signal grass by evaluating fleabane infestation and its correlation with the biomass of the grass. The second experiment consisted in herbicides applied in mixture, in a factorial arrangement 3x7: 2,4-D (1,209 g ha-1 a.e.), [halauxifen-methyl + 2,4-D] (5.76 + 780 g ha-1 a.i.), and dicamba (960 g ha-1 a.i.) composing the first factor; and metsulfuron-methyl (2.4 g ha-1 a.i.), chlorimuron-ehtyl (20 g ha-1 a.i.), diclosulam (25.2 g ha-1 a.i.), saflufenacil (35 g ha-1 a.i.), bentazon (576 g ha-1 a.i.), atrazine (1,000 g ha-1 a.i.), and untreated control composing the second factor. Corn cultivated in the second season integrated with Congo sinal grass reduced 80, 60, and 96% of fleabane emergence, growth, and biomass, respectively, during the off-season period. All chemical treatments provided >80% control on fleabane up to 8 cm tall, except for 2,4-D isolated. For plants with 8-16 cm tall, all mixtures were efficient (>85% control), while in plants taller than 16 cm, 100% control was observed for treatments composed by saflufenacil in mixture with all auxins herbicides. The selective treatments for Congo signal grass were 2,4-D and dicamba isolated and the associations with bentazon.
EFFICACY OF AMICARBAZONE AND FLUMIOXAZIM IN THE CONTROL OF MERRYMIA AEGYPITIA, MUCUNA TERRIMA AND RICINUS COMMUNIS IN THE RAW CANE SYSTEM
The presence of weeds can considerably affect the culture of sugarcane, especially in the beginning of its development. Thus, the aim of this study was to evaluate the efficacy of pre-emergence herbicides amicarbazone and flumioxazim in the control of the species Merremia aegypitia, Mucuna aterrima and Ricinus communis in the raw cane system. The survey was conducted under field conditions with sandy soil covered by 10 t. ha-1 sugarcane straw. The experiment was performed in quadruplicate outlined in randomized blocks. Certified weed seeds at a density of 10 plants / m2 were used, the herbicides amicarbazone (1400 g. ha-1 a.i.) and flumioxazim (250 g.ha-1 a.i.) were applied to a 6-nozzle pressurized costal sprayer model. The % of Control and phytotoxicity damage were evaluated at 7, 14, 23, 28 and 35 DAA, and the biomass of plant shoot at 35 DAA. Under the conditions studied, the herbicide amicarbazone had superior results in relation to the other treatments, with a high percentage of control for the three species studied (above 84.28% of control); for the species R. communis and M. aegypitia there was no difference explained in the treatments with and without straw, for M. terririma the treatment with amicarbazone proved to be more effective without the straw (97.14% of control) compared to the treatment with straw (84.28% of control). The herbicide flumioxazim, applied under similar conditions, showing a high percentage of control only for M. aegyptia (100% control), for which the presence of straw did not alter its action.
RESIDUAL EFFECT OF AUXINIC HERBICIDES ON SOY
The control of weeds in pastures is essential to improve the productivity indexes of agricultural activity and the correct and conscious use of herbicides is very important to reduce the problems caused by the residual effect in subsequent culture. Thus, this study evaluated the residual effect of the auxinic herbicides 2,4-D, picloram and 2,4-D + picloram on the initial development of soybean seedlings. The work was carried out in a greenhouse in a completely randomized design, in a 7 x 3 factorial scheme, with four replications. The first factor was composed of the percentages of the recommended doses of herbicides (100%, 50%, 25%, 12.50%, 6.25%, 3.12% and 0.00%) in which the highest dose (100% ) was equivalent to 2 L ha-1. The second factor was composed of the herbicides: 2,4-D, Picloram + 2,4-D and Picloram. The number of plants emerged for each treatment at 10 DAS, plant height and accumulation of fresh and dry mass at 40 DAS were evaluated. The herbicide picloram negatively affects the variables number and height of plants from the dose 3.12% and fresh and dry mass from the dose 6.25% and the herbicide picloram + 2,4-D negatively affects the variables number of plants from 3.12% dose, height plant from 6.25% dose and fresh and dry mass from 12.5% dose. Soy showed high sensitivity to picloram residues in the soil. The 25% and 50% doses, respectively, of the herbicides picloram + 2,4-D and picloram, limited the seedling emergence and the 100% dose prevented the germination of soybean seeds. No residual effect was observed for the herbicide 2,4-D in soybean seedlings in any of the studied doses.
CONTROL OF Cyperus difformis BY ALS HERBICIDES AND AUXIN MIMICS
The occurrence of Cyperus difformis L. biotypes with characteristics of resistance to herbicide application in the rice sector is a worldwide concern. In this sense, the objective was to evaluate the efficiency of the control of C. difformis by acetolactate synthase (ALS) inhibitors and auxin mimic. The experimental design was completely randomized, with four replications, totaling 252 experimental units composed of pots with 12 kilograms of soil and the treatments arranged in a 3x7x2x2 factorial scheme: three herbicides (two ALS inhibitors pyrazosulfuromethyl and bispiribaque-sodium and a mimetic of triclopyr-butotyl auxin); seven doses of the herbicides (0.0x, 0.5x, 1x, 2x, 4x, 8x and 16x the registration dose); two biotypes of C. difformis (Santa Rosa do Sul and Meleiro, Santa Catarina (SC)); and two soil moisture (100% saturated and 5,0 cm water depth). The C. difformis biotype of Meleiro-SC is 8x (320 g. i.a. ha-1) more resistant to the registration dose of bispiribaque-sodium, whereas the biotype of Santa Rosa do Sul-SC is more susceptible, reducing 50% of the dry mass of the aerial part with 0.5x of the registration dose (20 g. i.a. ha-1). Pyrazosulfuromethyl proved to be inefficient in reducing the dry mass of the aerial part in both biotypes. The biotypes C. difformis of Santa Rosa do Sul-SC and Meleiro-SC, in both soil moisture conditions, are susceptible to triclopyr-butotyl, reducing 50% of the dry mass of the aerial part with 0.5x (166 g. i.a. ha-1) the registration dose.
SOURGRASS COEXISTENCE INFLUENCES ON SOYBEAN SEED QUALITY
Sourgrass (Digitaria insularis) infestation is one of the great responsible for soybean(Glycine max) yield losses. However, a few studies are demonstrating its interference insoybean seed production fields. The aim of this study was to evaluate the sourgrassinterference on soybean seed quality. An experiment was conducted to analyze fivesourgrass density (0, 2, 4, 6 and 8 plants m-2) in two commercial soybean cultivars (GarraIPRO® and ST797 IPRO®). The damage in the highest sourgrass density (8 plants m-2)resulted in losses of 16% in the normal seeds number, increasing in 32% of dead seeds, and16% of germination losses for ST797 IPRO®. Garra IPRO® cultivar has not showndifferences in those variables, suggesting better competitiveness than ST797 IPRO®cultivar. The higher interference of sourgrass in soybean, the higher is the probability oflosses in seed quality. The magnitude of damage to seeds depends on competitiveness ofeach variety.
CHEMICAL CONTROL OF SOYBEAN AND COTTON VOLUNTEER PLANTS RESISTANT TO DICAMBA
This work was conducted with the objective of evaluating alternatives for chemical control of soybean and cotton volunteer plants, comparing glyphosate-resistant commercial cultivars to new transgenic cultivars resistant to dicamba, in two growth stages. Four independent trials were designed in the greenhouse, repeated for two consecutive years. Infestation of cotton and soybean volunteer plants was simulated in plastic pots with two distinct genetic materials. For cotton, a glyphosate-resistant (Roundup Ready Flex®) and a dicamba and glufosinate-ammonium tolerant (DGT) cultivars were used. The same experiment was repeated on plants with two or four leaves. For soybean, a glyphosate-resistant cultivar (Intacta®) and a glyphosate and dicamba-resistant cultivar (Xtend®) were evaluated. The same experiment was repeated on plants with two or four completely expanded trifoliate leaves. In conclusion, the timing of application and herbicide rate are most important factors for consistent control of volunteer plants with different technologies, especially for contact herbicides. When herbicides were applied in early growth stage and using the recommended rate, no differences were observed across technologies present in the cultivars. Therefore, independently of the technology present in cultivars, cotton plants can be controlled by 2,4-D, paraquat and flumiclorac, while soybean plants can be controlled with 2,4-D, paraquat and atrazine.
WEED CONTROL AND SELECTIVITY OF SULFENTRAZONE + DIURON ON SUGAR CANE (CULTIVAR RB 966928)
Selectivity and efficiency are key characteristics for herbicide recommendation. The objective of this work was to evaluate weed control and sugarcane selectivity of the commercial sulfentrazone + diuron mixture (Stone, 700 g a.i. ha-1 of sulfentrazone + 1400 g a.i. ha-1 of diuron, SC, FMC) in five doses: D1: zero g a.i. ha-1; D2: 350 g a.i. ha-1 + 700 g a.i. ha-1; D3: 700 g a.i. ha-1 + 1400 g a.i. ha-1; D4: 1050 g a.i. ha-1 + 2100 g a.i. ha-1; D5: 1400 g a.i. ha-1 + 2800 g a.i. ha-1; in two application modalities: pre- and initial post-emergence. Two experiments were conducted, one for each application mode, with four replications in completely randomized design. Weed control, maximum photochemical efficiency of photosystem II (Fv/Fm), height, fresh mass and dry mass of shoot and root volume and dry mass of sugarcane were evaluated. Post-emergence application of the commercial sulfentrazone + diuron mixture affected Fv/Fm at all doses evaluated. However, the lower herbicide doses (D2 and D3) did not negatively influence the phytometric variables. Even at the lowest dose (D2) weed control was total during the evaluation period. Sulfentrazone + diuron doses, between 350 g a.i. ha-1 + 700 g a.i. ha-1 and 700 g a.i. ha-1 + 1400 g a.i. ha-1, in pre- and initial post-emergence, are efficient in weed control and selective for sugarcane cultivar RB 966928.
BIOSTIMULANT AND FOLIAR FERTILIZER IN THE REDUCTION OF PHYTOINTOXICATION IN SOYBEAN CAUSED BY 2,4-D
The use of plant regulators and foliar fertilizers in crops has increased due to the benefits provided in plant nutrition and in tolerance to environmental stresses. The objective of this research was to evaluate the effects of plant regulator and foliar fertilizer in reducing injuries caused by the herbicide 2,4-D in two soybean varieties (M7110 IPRO and M7739 IPRO). Four experiments were conducted in randomized block design with four replications. In each experiment, ten treatments were used: single application of the plant regulator or foliar fertilizer at 0, 1, 3 and 5 days after application (DAA) of the herbicide 2,4 -D; application of half the dose of the plant regulator or leaf fertilizer at 0, 1, 3 and 5 DAA of the herbicide 2,4-D and the other half at seven days after the first application of the plant regulator or leaf fertilizer; only the application of 2,4-D; and not application of 2,4-D, plant regulator or foliar fertilizer. 2,4-D caused mild phytotoxicity (<10%) in soybean plants, regardless of the use of plant regulator or foliar fertilizer, which did not mitigate the injuries caused by the herbicide. The heights of plants and insertion of the first pod, the number of branches, pods per plant, grains per plant and the weight of a thousand grains in soybean plants were not affected by the treatments. For the variety M7739 IPRO, there was a reduction in grain yield in the control treated only with 2,4-D and when the plant regulator was applied up to 1 (one) day after the herbicide application. Both the plant regulator and the foliar fertilizer did not attenuate the herbicidal effects of 2,4-D, in the tested dose, for M7110 IPRO and M7739 IPRO soybean varieties.
MIXTURE OF HERBICIDES AND MOLIBDENIUM APPLIED IN POST-EMERGENCY IN COWPEA CROP
Tank mixing between herbicides and foliar fertilizers can promote adverse effects on crops due to antagonism between products. Thus, the objective of this study was to evaluate the effects of the application of molybdenum (Mo) in a tank mixture with herbicides on cowpea crop yield and weed control. The randomized block design was adoted, with four replications in a 6x2 factorial scheme. The first factor consisted of the control with weeding and control without weeding and the application of the herbicides bentazon, imazethapyr and the mixtures bentazon + imazamox and bentazon + imazethapyr. The second factor by the absence and application of 80 g ha-1 Mo. Weed density and dry mass, phytointoxication, main stem length, stem diameter, chlorophyll a and b contents and cowpea yield components were evaluated. Mo application associated with bentazon, imazethapyr, bentazon + imazamox, bentazon + imazethapyr herbicides did not affect weed control efficiency and selectivity for BRS Guariba cowpea. Herbicide-induced phytointoxication was mild (<5%) at 7 days after treatment application (DAT), with symptoms disappearing at 14 DAT. Mo application increases chlorophyll a and b content at flowering, the length of the main stem and the number of pods per plant at harvest time. Weeds reduce cowpea grain yield, regardless of Mo application.
STUDY OF SELECTION OF WEEDS COMMUNITY BY HERBICIDES USING MULTIVARIATE ANALYSIS TECHNIQUES
For decision making on which strategy is improve for weed management, statistical tools such as multivariate analysis. Especially with a large amount of data, can be used. The objective of this study was to evaluate the feasibility of the use of multivariate analysis for studies on the selection of weed flora as a result of the application of different herbicides. The experiment was in field, in randomized blocks, with four repetition, the area was divided into 32 plots with 3 x 5 meters in length with 8 plots per block. The experimental treatments were: 1-glyphosate, 2- 2,4D; 3-glyphosate + 2,4D; 4- carfentrazone-ethyl; 5-glyphosate + carfentrazone-ethyl; 6-haloxyfop-methyl; 7-clethodim; 8-ammonium glufosinate. The weed community was surveyed in each plot, before application and at 30 days after application of the treatments. The data were submitted to cluster analysis and main components. The most discriminating weed species were Alternanthera tenella and Commelina benghalensis, followed by the grasses Panicum maximum, Cenchrus echinatus and Eleusine indica. The results of cluster analysis were very similar to those obtained by principal component analysis. Multivariate statistical techniques were able to group chemical treatments according to specific composition regardless of the phytosociological index considered.
INTERFERENCE OF SOIL COMPACTION ON DICLOSULAM RESIDUAL
The residual herbicides in the soil can be influenced by several factors, including soil compaction. The objective of this study was to evaluate the influence of soil compaction on selectivity of diclosulam to soybean, as well as the carryover effect on the corn in succession. The experiment was carried out in clay and sandy soil. The experimental design was in a randomized block with four replicates. The treatments were arranged in a 3x3 factorial scheme, where A factor was level of compaction (0 - no compaction, 10 and 20%) and the B factor doses of diclosulam (0, 25.2 and 50.4 g ai ha-1) applied in pre-emergence of soybean. After soybean harvested, the columns were opened and corn and cucumber were seeding. The analyzes carried out on soybean were chlorophyll a fluorescence, shoot dry matter (SDM) and NPK content at 90 days after germination (DAG). For corn: chlorophyll a fluorescence transient was performed at 15, 30 and 45 DAG. For corn and cucumber: plant height, root length, SDM and root dry mass at 45 DAG. The herbicide residue quantification was performed by LC-MS/MS at 94 days after application. Data were submitted to ANOVA (p ≤ 0.05) and the means were compared by Tukey at 5%. Soybeans plants in both soils showed no difference in growth parameters and NPK content but photosynthesis parameters was impaired. There was no corn crop carryover regardless of soil compaction. There was a reduction of cucumber plants being aggravated in soils with compaction. No diclosulam residue was detected in solutions evaluated by LC-MS/MS.
PHENOLOGICAL STAGES ASSOCIATED WITH CHEMICAL CONTROL IN THE MANAGEMENT OF SPERMACOCEA DENSIFLORA ORIGINATED FROM SEEDS AND SPROUTS
The selection of Spermacoceae densiflora specie has been verified in areas with the continuous use of glyphosate herbicide. The objective of this work was to evaluate the effect of glyphosate-isolated or associated with herbicides applied in post-emergence of S. densiflora in seed and sprouting plants at different phenological stages. In both cases, a completely randomized design with 5 replications in a 2 x 17 + 1 factorial scheme was used, being two weed phenological stages (4 and 8 fully expanded leaves) and 16 types of chemical control plus witness without herbicide. The chemical treatments were: glyphosate (1,440 g ai ha-1), ammonium glufosinate (500 g ai ha-1), 2,4-D (1,000 g ai ha-1), chlorimuron -ethyl (20 g ia ha-1), carfentrazone-ethyl (920 g ai ha-1), flumioxazin (50 g ai ha-1), smetolachlor (960 g ai ha-1), imazethapyr (100 g ai ha-1), saflufenacil (50 gia ha-1) and the association of glyphosate with these herbicides, except with glufosinate. In the second test, plants of S. densiflora were cut close to the ground and plants from regrowth with different phenological stages (4 and 8 leaves) were submitted to the respective chemical treatments of test 1. In the initial stage of application the best treatments were the use of ammonium glufosinate, flumioxazin, glyphosate + chlorimuron, glyphosate + flumioxazin and glyphosate + saflufenacil, with control above 96.00%. For later applications, the respective treatments maintained high control (above 88.00%), except for glyphosate + chlorimuron, with 48.00% control. For regrowth plants all treatments evaluated were not effective in controlling the species.
TOLERANCE OF YOUNG COFFEE PLANTS TO HERBICIDE APPLIED ALONE OR IN COMBINATION WITH FERTIACTYL
The control of weeds in the coffee crop is hampered by the scarcity of selective herbicides for the growing crop. An alternative to circumvent the damage caused by herbicides is the use of chemical protectors with the ability to minimize herbicide intoxication. The objective was to evaluate the selectivity of herbicides applied alone or in a mixture in the tank with Fertiactyl Sweet® for recently transplanted coffee plants. The experiment was carried out in pots in a completely randomized design, in a 10x2 factorial scheme, with four replications. The first factor corresponded to nine herbicides: (oxyfluorfen; sulfentrazone; flumioxazin; [isoxaflutole + indaziflam]; isoxaflutole; indaziflam; [metribuzin + indaziflam]; chlorimuron-ethyl; and metsulfuron-methyl) and control without herbicide application; the second factor was the presence or absence of Fertiactyl Sweet. The treatments were applied “over the top” at 30 days after transplanting. From 7 to 172 days after application (DAA), the percentage of intoxication was evaluated. And at 172 DAA, the morphological variables of the plants were measured. The addition of Fertiactyl Sweet next to the herbicide syrup did not change the tolerance of coffee plants to herbicides. The most tolerant herbicides for coffee were oxyfluorfen and sulfentrazone. The commercial mixture indaziflam + metribuzin caused the death of the coffee seedlings. Fertiactyl Sweet® did not reduce the poisoning of Arabica coffee seedlings (Catuaí Vermelho - lineage 44) caused by the studied herbicides. The herbicides metsulfuron-methyl and oxyfluorfen were the most tolerated by recently transplanted coffee plants.
CROP ROTATION AND TILLAGE EFFECT ON THE WEED SEED BANK IN LOWLANDS
On the rice crop, weed species more adapted to the production system appear in greater incidence in the area, thus, crop rotation can be an alternative to help reduce the weed seed bank. In this sense, the objective of this work was to evaluate the dynamics of the barnyardgrass (Echinochloa spp.) and alexandergrass (Urochloa plantaginea) seed banks in lowlands, in response to crop rotation and soil management. Rice, soybean and sorghum crops were used under conventional tillage and no-till system, cultivated in strips. Barnyardgrass and alexandergrass seed banks were evaluated after two years of cultivation, in the top 0-5 and 5-10 cm layers of soil. Barnyardgrass and alexandergrass seed bank densities were higher in continuous sorghum cultivation compared to rice cultivation. There was no difference of the seed bank between different soil layers, except for alexandergrassin continuous sorghum cultivation. The continuous sorghum cultivation in lowlands, without the use of a post-emergence herbicide, increases barnyardgrass and alexandergrassseed bank.
TECHNICAL AND ECONOMIC VIABILITY OF ADDING ACCASE AND ALS INHIBITORS TO GLYPHOSATE IN THE CONTROL OF WEEDS AND SOYBEAN GRAIN YIELD
The continuous use of glyphosate in soybean has led to the appearance of resistant weeds. Thus, alternatives to manage resistant plants are needed, such as the use of products with different mechanisms of action. In this study, the efficacy of the post-emergence application of herbicides with different mechanisms of action in the control of weeds in soybean crop was tested. The experiment was conducted in the 2016/2017 season, in Cambé-PR, using randomized blocks, with four replications. We evaluated the following treatments: glyphosate; glyphosate + haloxyfop with chlorimuron-ethyl in sequential application; glyphosate + clethodim with chloransulam in sequential application; hand-hoe weeding; infested control. The exclusive use of glyphosate did not present efficient control of the weeds found. The species Digitaria insularis (sourgrass), Commelina virginica (Virginia dayflower) and Digitaria horizontalis (Jamaican crabgrass) were efficiently controlled by treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application. However, the species Conyza bonariensis (hairy fleabane) and Ipomoea purpurea (common morning glory) were efficiently controlled only by hand-hoe weeding. The grain yield of soybean was higher in the treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application, which yielded an average of 4,600 kg ha-1. Treatments glyphosate and infested control had a lower mass of 1000 grains and lower grain yield. The highest net revenue was obtained by treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application. Therefore, the application of herbicides with different mechanisms of action (EPSP inhibitor, ACCase inhibitor and ALS inhibitor) improved weed control, soybean grain yield and profitability compared to the isolated application of glyphosate and the manual weeding.
EFFECTIVENESS OF THE MIXTURE OF ALGICIDE WITH HERBICIDES IN MACROPHYTES AND SECONDARY ALGAE CONTROL
The objectives of this study were to determine the effectiveness of the control of imazamox and saflufenacil herbicides isolated and in combination with copper hydroxide (copper ion source) in the control of macrophytes (Ceratophyllum demersum) and to determine the efficacy of control of unicelular (Ankistrodesmus gracilis) and filamentous (Pitophora kewensis) algae mixtures imazamox + 0.1% copper and saflufenacil + 0.1% copper, in laboratory condition. For the control of C. demersum, the experiments were installed with concentrations of 0.01; 0.1; 1.0; 2.5; 5.0; and 10.0 mg L-1 imazamox and saflufenacil isolated or added 0.1% copper source. For experiments with unicellular algae (70 mL of collected water) and filamentous algae (1.0 g) was used at concentrations of 0.01; 0.1; 1.0; 2.5; 5.0; and 10.0 mg L-1 imazamox and saflufenac plus 0.1% copper. After the end of the experiment the concentration of chlorophyll a and pheophytin was determined in the samples. With the use of imazamox + 0.1% copper there was a reduction of 100% of the weight and the length of the macrophyte from 2.5 mg L-1. With saflufenacil + 0.1% copper occurred 100% plant mortality in 1.0 mg L-1. The tested mixtures were also effective in reducing the photosynthetic activity of unicellular and filamentous algae. The application of the imazamox and saflufenacil herbicides added with 0.1% of copper hydroxide shows synergism in the control of submerged macrophytes and may present algicide side effect.
EFFECT OF ADJUVANT ASSOCIATED WITH HERBICIDES IN THE CONTROL OF Digitaria insularis L.
The application of herbicides with adjuvants can improve the efficiency of weed control such as Digitaria insularis L., which causes losses in several agricultural crops due to its high competitiveness and difficulty in control. This study aimed to evaluate the synergism of the adjuvant SinerMax® associated with the herbicides clethodim, glyphosate and haloxyfop-methyl in the control of bitter grass (Digitaria insularis L). The experiment was conducted between September and October 2018. The experimental design used was the randomized blocks in a 3x2 + 1 factorial scheme with 5 replications, with treatments with clethodim 240 g L-1 of ia, (0.45 L ha-1), glyphosate 480 g L-1 ia (4 L ha-1) and haloxyfop-methyl124.7 g L-1 ia (0.5 L ha-1) associated or not with the adjuvant SinerMax® (0,5 L ha-1) and the control treatment without use of herbicide, being evaluated the absence of apparent damage, the complete death of the plant and dry matter of the plants. The data obtained were subjected to analysis of variance and the means compared by the Scott-Knott test at 5% probability. The haloxyfop- P- methyl and glyfosate herbicides have the best levels of control of Digitaria insularis L., with higher phytotoxicity (between 60 and 90%) and less dry matter accumulation compared to the control treatment. The adjuvant SinerMax® associated with the herbicides glyphosate, haloxyfop-methyl and clethodim did not result in greater control efficiency of D. insularis L.
INTERFERENCE OF SOURGRASS PHENOLOGICAL STAGE ON THE EFFECTIVENESS OF GLYPHOSATE HERBICIDE
Efficient weed chemical control with post-emergence herbicides depends upon the phenological stage of the target plants in the moment of application. In this sense, plants’ phenological stage is an important variable to be considered in the production environment, once it interferes on product’s efficacy and demands reallocation of the recommended rates. Thus, this work was developed with the objective of evaluating glyphosate-susceptibility of sourgrass influenced by the phenological stage at the moment of application. Two similar experiments were carried out, in which treatments were organized according to a 8x5 factorial scheme, where eight were the rates of glyphosate herbicide (0, 45, 90, 180, 360, 720, 1440, 2880 g ha-1) and five were the phenological stages of sourgrass. Compared to the dry mass variable, it was observed that the variable percent control promoted better estimative of sourgrass susceptibility to glyphosate considering different phenological stages; for that variable, calculating DL80 reached excellent estimative of species herbicide susceptibility, providing the equation y = 26.276x – 112.42, i.e., increasing glyphosate rate by 150 g ha-1 was necessary to reach DL80 for each 10 units of plants’ development in BBCH scale.
Watermelon sensitivity to residual of pre-emergent herbicide applied in soybean crop
The long-lasting residual effect of herbicides depends on the soil and molecule characteristics; however, the bioactivity of the herbicide can cause damage to the crop in rotation/succession. The most common way to identify the presence of herbicides in the soil is by the implantation of bioassays that uses a susceptible species to herbicidal molecules as an indicator of residues. The aim was to identify the sensitivity of watermelon as bioindicator to the pre-emergence herbicide residue used in soybean cultivation. The assay was carried out in a greenhouse, in 3 L pots, in a randomized block design, with four replicates, in a factorial scheme of 3x4+1, where factor A was the herbicides diclosulam, [imazapyr + imazapic], and metribuzin, and factor B the doses of commercial products [1/8D, 1/4D, 1/2D and D (recommended label dose)] plus control treatment. Four watermelon seeds were sown in soil per pot after herbicide application. The variables were analyzed 30 days after the emergence of the plants: shoot length (cm), length (cm), root volume (mL), shoot dry mass (g) and root dry mass (g). Watermelon seeds did not germinate in the treatments with sub-doses of the herbicides diclosulam and metribuzin, and the growth was reduced in the sub-doses of the herbicide [imazapyr + imazapic], showing the sensitivity of this species. The herbicides studied adequately exerted control in watermelon bioindicator plants. Watermelon has sensitivity to the herbicides diclosulam, metribuzin and the commercial mixture of the herbicides [imazapyr + imazapic], with the potential to indicate the residue of these herbicides in clayey soil.
Copyright (c) 2019 Brazilian Herbicide Journal
ALTERNATIVES OF CHEMICAL MANAGEMENT OF SOURGRASS IN SOYBEAN CROP
The resistance of weeds to herbicides demands new strategies of chemical management of the intraspecific community, considering their capacity of interference in cropping systems. The objective of this study was to evaluate the efficacy of ACCase inhibitors applied in a mixture or sequential with the herbicide 2,4-D, as alternatives for control of sourgrass. The experimental design was in randomized blocks, with eleven treatments and four replications, between 2015 and 2016. The compounds were determined by the herbicides cletodim, haloxyfop-p-methyl, fenoxaprop-p-ethyl, quizalofop-p-ethyl and fluazifop-p-butyl in mixture or sequential with 2,4-D, in addition to glyphosate-associated applications of graminicide and paraquat in all treatments, Visual evaluations were carried out at 5 days before sowing (DBS) and with 0; 10; 20; 40; 50 and 65 days after sowing (DAS) to determine the sourgrass control. The application of the herbicides cletodim and haloxyfop-p -methyl in mixture or sequential with 2,4-D do not differ in the control of the sourgrass plants. The application of the herbicides fenoxaprop-p-ethyl, quizalofop-p-ethyl and fluazifop-p-butyl in sequential with the herbicide 2,4-D at higher control compared to the use thereof in a mixture with 2,4-D. The herbicide fluazifop-p-butyl in mixture with 2,4-D is not indicated for the control of sourgrass.
WEED CONTROL IN SOYBEAN CROP WITH GLYPHOSATE APPLICATION BY CONTACT WITH POLYESTER ROLLER
In recent years, a new form of weed control has emerged, contact control. The aim of this study was to compare different modes of application and doses of the herbicide glyphosate in soy. The experiment was carried out in a commercial soybean area in Sinop MT. The experimental design was a randomized block, with five replications and eight treatments. The 8 treatments were: Physical control, manual weeding with a hoe; Application with costal sprayer in doses of 0.7 and 1.4 kg ha-1 of glyphosate; Bush, without weed control; Application with polyester roller in doses 0.7 and 1.4 kg ha-1 of glyphosate in contact with the soil; Application with polyester roller in doses 0.7 and 1.4 kg ha-1 of glyphosate at 2 cm from the ground. Weed population control and density, vegetative growth and soybean productivity were evaluated. The application via roller, both in contact with the soil, when only weed is shown to be as efficient as spraying in weed control. The species of Eleusine indica and Spermacoce latifolia were the species that maintained or even increased the density in the cultivation area. Regardless of the form of application, the use of glyphosate did not affect the vegetative growth and productivity of cultivar NS 7901 RR. Although no statistical differences were detected, productivity in general increased when glyphosate was applied, with no differences in the form of application, by contact or spray.
EFFICACY OF HERBICIDES IN THE CONTROL OF MORNING GLORY
The good establishment of agricultural crops depends on several factors related to the way weeds are managed. Morning glory (Ipomoea sp.) Is one of the most problematic weeds in agricultural crops in Brazil, causing a reduction in production and making harvesting operations more difficult. In this sense, the objective was to evaluate the effectiveness of different herbicides applied in post-emergence of viola string. The experiment was conducted from July to September 2018 in a greenhouse. The experimental design used was a randomized block (DBC), with six treatments (T1 - glyphosate, T2 - chlorimuron-ethyl, T3 - metsulfuron-methyl, T4 - carfentrazone-ethyl, T5 - saflufenacil, T6 - control without herbicide application), with four repetitions. To determine the effectiveness of control, phytointoxication assessments were made based on a visual scale at 7, 14 and 21 days after application. In the same period, root length, shoot and total length, stem diameter and total dry matter of the plant were measured. Carfentrazone-ethyl (30 g a.i. ha-1) and saflufenacil (35 a.i. Glyphosate 1920 g e.a. ha-1), chlorimuron-ethyl (12.5 g a.i. ha-1) and metsulfuron-methyl (3.6 g a.i ha-1) are not recommended for the control of morning glory (Ipomoea sp.) due to the low percentage of control.
Gabriella Daier Oliveira Pessoa Carneiro
SELECTIVITY OF HERBICIDES APPLYED IN PRE- AND POST-TRANSPLANT IN JAPANESE PUMPKIN CROP
The slow initial growth and the small size of the pumpkin favor the establishment of weeds in the cultivated areas, requiring adequate management so that there is no reduction in productivity. However, there are currently no herbicides registered for pumpkin cultivation. Thus, the objective was to verify the selectivity of herbicides in pre and post-planting Japanese pumpkin seedlings. The experiments were conducted in a randomized block design with four replications. For pre-planting and post-planting applications, treatments were composed of herbicides; flumioxazin (30 g a.i. ha-1), oxyfluorfen (240 g a.i. ha-1), clomazone (600 g a.i. ha-1), fomesafen (250 g a.i. ha-1), fluzifop-p-butyl (125 g a.i. ha-1) and the control. In addition, a pre-planting treatment with paraquat (400 g a.i. ha-1) was tested. Visual intoxication was evaluated 7, 14 and 21 days after herbicide application (DAA). At 21 DAA, plant height, stem diameter, number of leaves and dry matter of aerial part, root and total were evaluated. The herbicides oxyfluorfen (240 g a.i. ha-1), fomesafen (250 g a.i. ha-1), fluzifop-p-butyl (125 g a.i. ha-1) and paraquat (400 g a.i. ha-1) showed high selectivity in pre -planting japanese pumpkin seedlings, with low intoxication (between 0 and 4%), less dry matter loss and less variation in plant growth parameters. In post-planting, flumioxazin (30 g a.i. ha-1) did not show a significant reduction in dry matter and growth variables, but it caused poisoning greater than (24%). Fluzifop-p-butyl (125 g ia ha-1) and fomesafen (250 g ia ha-1) showed greater selectivity (intoxication between 0 and 4%) in post-planting when compared to the control and other herbicide treatments evaluated.
WEED MANAGEMENT IN TROPICAL FRUIT CROPS: PINAPPLE, BANANA, COCONUT, PAPAYA AND PASSION FRUIT
O Brasil é o terceiro maior produtor de frutas do mundo, sendo que as plantas daninhasconstituem um dos principais problemas para a exploração da capacidade de produção defrutíferas tropicais. Ainda há muitas lacunas no conhecimento do manejo adequado deplantas das plantas daninhas em cultivos de frutíferas. O objetivo desta revisão foi sumarizardados sobre a interferência, métodos de controle e manejo de plantas daninhas nas culturasdo abacaxizeiro, bananeira, coqueiro, mamoeiro e maracujazeiro. Métodos mecânicosassociados à aplicação de herbicidas nas entrelinhas de cultivo são as principais práticas decontrole, enquanto o consórcio com culturas intercalares, controle físico, controle cultural ea integração frutíferas-pecuária ainda são práticas pouco utilizadas. Os principais problemasrelacionados ao manejo de plantas daninhas em frutíferas tropicais estão relacionados,muitas vezes, a utilização do método inadequado, falta de informação sobre os períodoscríticos de interferência de plantas daninhas (período de controle) e ao baixo número demoléculas herbicidas registrados para estas culturas.
Control of soybean RR voluntary in culture of corn with different doses and mixtures of herbicides
Biotech soybeans called Roundup Ready (RR) are tolerant to the lethal effects of glyphosate herbicides, so traditional desiccation options are not sufficient to manage these plants. The objective of this study was to evaluate the efficacy of herbicide interaction in the control of RR soybean plants and the selectivity in the maize crop. The experiment was conducted in a completely randomized design, in a greenhouse with soybean (RR) and corn plants. The treatments consisted of the combination of the herbicides glyphosate and two atrazine in different doses. The herbicides were applied to soybean seedlings at the phenological stage V1, V2 and V3 and in corn seedlings at the V3 stage. The mixture of glyphosate and atrazine provided control of voluntary soybean RR in the three evaluated stages and development of corn compatible with the control. When the objective is just control of the voluntary soy RR it is necessary the addition of glyphosate to atrazine. The use of the lowest recommended dose of the Proof® and Primóleo® products efficiently control RR volunteer soybean plants in maize.
Fomesafen selectivity sprayed in preemergence of different cultivars of cotton
There is an outstanding difference among cotton cultivar related to injury caused by herbicides applied in preemergence. This way, the present work was conduct in greenhouse with the objective to evaluate the effect of crescent doses to fomesafen about the initial growth to eight cotton cultivars. The experimental design utilized was the completely randomized, arranged in factorial design 8 x 6, with five replications. Evaluate the response of eight cotton cultivars (DP 555 BG RR, FMT 705, FMT 701, FM 910, FM 966 LL, FM 993, IMA CD 6001 LL e IMA 8221) to six doses to fomesafen herbicide (0, 125, 250, 375, 500 e 625 g ha-1 a.i.), applied in preemergence, after the sowing, that was realized in three centimeters of deep. The soil utilized was red Oxisol, pH of 5.9, 2.94% of M.O., 320 g kg-1 of clay and 600 g kg-1 of sand. The variables evaluated was phytointoxication percentage at 5, 10 and 20 days after application, besides to dry weight of shoot 30 days after application. Conclude that cotton cultivars response of the different way to fomesafen applied in preemergence. The cultivar most tolerant was FMT 705. The most sensible cultivars were IMA CD 6001 LL, FMT 701 and FM 993.
Indicators species of saflufenacil residue in soils
One of the methods, efficient and low cost, to estimate the presence of herbicides in the soil is the biological. However, before using this method it is necessary to identify species that have high sensitivity to the herbicide under controlled conditions. This research aimed to select species that show high sensitivity to saflufenacil for later studies of the dynamics of this herbicide in soil. The sensitivity of seven plants species to saflufenacil (Curcubita pepo, Beta vulgaris, Daucus carota, Citrullus lanatus, Cucumis sativus, Sorghum bicolor and Solanum lycopersicum) were evaluated. For this, these species were cultivated on an inert substrate (washed sand) treated with increasing doses of saflufenacil (0.0, 0.625, 1.25, 2.50, 5.0, 10.0 and 20.0 g ha-1). The species B. vulgaris, S. lycopersicum and S. bicolor were the most sensitive to saflufenacil. Among these species, B. vulgaris is easy to grow, fast growing and allows rapid visualization of the symptoms of intoxication. It was concluded that B. vulgaris can be considered as an indicator of the presence of saflufenacil in the soil solution to study the dynamics of this herbicide in soils.
Alternatives for chemical control of rice flatsedge resistant to ALS-inhibiting herbicides
Cyperus iria L. (CYPIR) is one of the main cyperaceae occurring in irrigated rice crop. For many years, acetolactate synthase inhibitor herbicides (ALS) were the main tool to control CYPIR, favoring the selection of cross-resistance biotypes. Based on the level of resistance, it is necessary to adopt alternative chemical control measures in order to avoid the evolution of the resistance and to reduce the interference on the crop. The aim of this work was to evaluate alternatives of chemical control of CYPIR to ALS-inhibiting herbicides, occurring in irrigated rice crops in southern Brazil. There were conducted two experiments in greenhouse, arranged in completely randomized design with four replicates. The herbicides used were: imazethapyr; imazapyr+imazapic formulation; bentazon; propanil; formulation of bentazon+imazamox; mixture of (bentazone + imazamox) + (imazapyr + imazapic); association of bentazone + (imazapyr + imazapic); glyphosate; and control without herbicide. The control evaluation was performed in a resistant (CYPIR-S) and susceptible (CYPIR-S) biotype, and the phytotoxicity evaluated in the Guri Inta CL, IRGA 424 RI and IRGA 409 cultivars. At 28 days after application (DAA) the control / phytotoxicity and shoot dry matter (SDM) were evaluated. All treatments tested, except for imazethapyr and imazapyr+imazapic applied in isolation, were efficient. There are alternatives to the chemical control of Cyperus iria resistant to ALS-inhibiting herbicides and these, when associated with products that have different mechanisms of action, do not impair the use of ClearField® technology.
Selection of bioindicator species for the herbicide indaziflam
The indaziflam herbicide presents residual activity in the soil and may become a problem for agricultural crops, due to the possibility of carryover in successor crops. Thus, the objective was to select potential bioindicator species for the presence of indaziflam residues in the soil. Two experiments were carried out in a greenhouse using 0.000250 m3, both distributed in a randomized complete block design with four replicates. In the first experiment, eleven species with potential use as bioindicators were used: rice, oats, beet, brachiaria grass, beans, sunflower, corn, cucumber, soybean, tomato and wheat submitted to seven doses of indaziflam (0; 6.25; 12.5; 25; 50; 75 and 100 g a.i. ha-1) in pre-emergence of crops. In the second experiment, five sub-doses (0, 0.3906, 0.7812, 1.5625 and 3.125 g a.i. ha-1) of indaziflam were applied to the species that did not emerge at the lowest dose or concentration of the herbicide in the first experiment. The phytotoxicity and plant height (ALT) were evaluated at 3, 7, 14 and 21 days after emergence (DAE). Dry matter of aerial part (MSPA), root (MSR) and total (MST) was evaluated at 21 DAE. Different levels of tolerance of the species to indaziflam were observed. Increased indaziflam doses caused increased phytotoxicity symptoms and reductions in ALT, MSPA, MSR and MST. Among the evaluated species, in monocotyledons in the order: signal grass, rice, corn, wheat and oats in eudicots: tomato, cucumber, sunflower, beans e soybean present potential for use as a bioindicator in indaziflam studies. The beet was extremely sensitive to the herbicide and did not emerge at any of the doses studied.
Herbicides to weed control and in pre-budded seedlings (MBPs) of different varieties of sugarcane
Pre-sprouting seedlings (MPB) of sugarcane arrive in the field with the aerial part and roots developed, being able to present sensitivity to herbicides and to change weed control management. Therefore, the objectives of this work were: determine the chemical control of Cynodon dactylon, Chloris polydactyla and Merremia aegyptia; and to determine the effect of the herbicides on pre-budded seedlings of different varieties of sugarcane. The experimental design was completely randomized with eleven treatments and four replicates. The herbicides saflufenacil, clomazone, metribuzim, tebuthiuron, indaziflam, saflufenacil + clomazone, saflufenacil + metribuzim, saflufenacil + tebuthiuron, indaziflam + metribuzin, indaziflam + tebuthiuron, and control were applied for the control of Cynodon dactylon, Chloris polydactyla and Merremia aegyptia and on MPBs varieties - RB 867515, RB 966928 and CTC 9001. Control evaluations were performed at 15, 30 and 45 days after application (DAA) and phytotoxicity in the culture at 15, 30, 45 and 60 DAA, in addition to biomass of the aerial part. For C. polydactyla all treatments were effective, for M. aegyptia the best treatments were saflufenacil, metribuzin and saflufenacil + tebuthiuron e saflufenacil + tebuthiuron. In the control of C. dactylon we could highlight clomazone, metribuzin, saflufenacil + clomazone e tebuthiuron. The indaziflam and indaziflam + metribuzin treatments impaired the initial growth of the MPBs of the three studied sugarcane varieties; therefore, they present limitations in the use of MPBs.
Glyphosate drift modify flooded rice’s development and yield
The objective of this research was to evaluate the injury to the development and yield of early cycle flooded rice cultivar (IRGA 430), caused by simulated glyphosate drift. The experiment was carried out in the field at the Experimental Station of the Rice - IRGA, in the 2016/17 season, and treatments were arranged in factorial scheme 3x2+1 whose factor A consisted of the glyphosate drift simulation with rates of 135; 270 and 540g ha-1 a.e.; the factor B of two nitrogen (N) rates, being 90 and 121.5 kg ha-1 N; more control without application of glyphosate and with the application of 90 kg ha-1 N. There increase in glyphosate rate results in higher injuries to the crop, with phytotoxicity symptoms, less panicles per area, and about 60% yield loss. The period of emergency until the anthesis (R4) was prolonged. The glyphosate simulated drift shows higher phytotoxicity, lesser plant height and increase development cycle, promoting negative interference on flooded rice yield.
Safflower (Carthamus tinctorius L.) is an annual oleaginous plant that presents high potential in Brazilian agriculture. The chemical control of weeds in the crop is essential to avoid damage and protect productive potential. The objective of this study was to evaluate the selectivity of herbicides applied in pre-planting incorporated (PPI), pre-planting (PRE) and post-emergence (POST) of the safflower crop. For all, three experiments were installed in greenhouse with a completely randomized design with five replications. The herbicides evaluated for application in PPI (Experiment I) were: diclosulam, metribuzin, pendimethalin and trifluralin; for the application in PRE (Experiment II) the herbicides were: 2,4-D, ametryn + clomazone, atrazine, carfentrazone, carfentrazone + sulfrentrazone, clomazone, diclosulam, flumioxazin, imazethapyr, isoxaflutole, lactofen, mesotrione, metribuzin, metsulfuron - ametryn + clomazone, atrazine, bentazon, bentazon + imazamox, carfentrazone, chlorimuron, clethodim + fenoxaprop, clethodim, clodinafop, were used for the application in POST (Experiment III) , floroxypyr, fluazifop + fomesafen, fluazifop-P, flumiclorac-pentyl, flumioxazin, fluroxypyr, fomesafen, foramsulfuron + iodosulfuron, haloxyfop, imazethapyr, iodosulfuron, lactofen, mesotrione, nicosulfuron, tembotrione and tepraloxydim), compared to the control without herbicide application . The crop phytotoxicity was evaluated at 7, 14, 21 and 28 days after application (DAA), using the percentage scale from 0 to 100, with fresh and dry mass obtained at 35 DAA. The data was submitted to analysis of variance and the means were compared by the Tukey test (p≤0.05). Trifluralin herbicide is selective to the safflower crop in PPI and PRE aplications, while cletodim, fluazifop-p-butyl and haloxyfop-p-methyl are selective for application in POST.
Residual effect of clethodim applied in corn pre-seeding
Brazil is one of the few countries where it is possible to produce more than one crop in the same agricultural year, and the soybean-corn succession is practiced by most of the producers. This cultural system provided the selection of weeds resistant to herbicides, mainly by the use of herbicides with the same mechanism of action in successive crops. In this scenario, new management strategies should be adopted, such as herbicide applications in corn pre-sowing. The objective of this search was to evaluate the influence of periods of application of clethodim on pre-sowing, on emergence and initial development of maize hybrids. For this, the residual effect of clethodim on hybrid 2B810 Power Core, Status Viptera 3, Dekalb 340 VT PRO2 with application of clethodim 196.80 g L-1 a.i. at 15, 10, 5, 3 and 1 day before sowing (DBS) of corn and a control without application. The variables analyzed were: emergence, plant height, falker chlorophyll index, stalk diameter, fresh and dry matter accumulation. The application of clethodim 1 day before sowing adversely affected the emergence and initial development of evaluated corn hybrids. The hybrids presented differential susceptibility to the residual of clethodim for emergence variables, accumulation of fresh matter and dry matter accumulation.
Determination of control dose of Urochloa decumbens by the glyphosate application
The species Urochloa decumbens is an important weed of agricultural crops due to the high adaptive capacity and difficulty of management. The presence of these plants into agricultural production areas can cause serious problems when it competes for water, light and nutrients, besides acting as host of pests and common pathogens to the crop and interfering in harvesting. The study aimed to evaluate doses of control of U. decumbens plants by glyphosate application. Three experiments were conducted, in greenhouse in completely randomized design with six replications, containing between 50 and 80 plants per replication, and eight doses of glyphosate (0, 22.5, 45, 90, 180, 360, 720 and 1440 g ha-1 a.e.). Visual evaluations of injury were performed at 0, 7, 14 and 21 days after application, and collecting eight plants per pot and per treatment to determine dry mass in each evaluated time. For the response curves, the total dry mass was considered, adding all the collected times and the remaining plants from the pots at the end of the experiments. U. decumbens plants treated with 180 g ha-1 a.e. of glyphosate reduced the dry mass in relation to the control, demonstrating greater sensitivity in the application of doses below those recommended and used in the field. In conclusion, the dose 80 g ha-1 a.e. of glyphosate controlled U. decumbens plants causing injury close to 100% and the estimated doses between 30 and 62 g ha-1 a.e. of glyphosate were able to reduce 50 % of plant growth
DETERMINATION OF RESIDUAL EFFECT OF INDAZIFLAM AND AMICARBAZONE IN TWO SOILS THROUGH BIOASSAY
The herbicides indaziflam and amicarbazone effectively control weeds, as they persist for long extensions in the soil. The objective of this work was to evaluate the residual effect of indaziflam and amicarbazone in contrasting textures. Two experiments were conducted, one experiment for each herbicide using a the randomized block design, with four replications, in a 2x6+1 factorial scheme, that is, two types of soils, six application times (0, 20, 40, 60, 80 and 100 days after application - DAA) and a control. Used as doses of 100 and 1.400 g ha-1, for indaziflam and amicarbazone, respectively. At each evaluation period, the cucumber (Cucumis sativus L.) was sown and the visual intoxication of the species was measured at 21 days after sowing. At 0, 20 and 40 DAA of amicarbazone, phytointoxication was 100% for both soils. It was observed at 100 DAA, ditostically reducing phytointoxication, close to 0%, in sandy soil (DT50 @ 56 days) and 30% in clayey soil (DT50 @ 59 days). Indaziflam provided 100% phytointoxication at all times. It was concluded that the indaziflam had greater residual activity than amicarbazone, regardless of the soil. Already, for the amicarbazone, the effect was higher on the clay texture.
Herbicides used in corn in control of voluntary soybeans
Volunteer soy is a problem in maize cultivation, interfering with its development and growth. The objective of this work was to evaluate the efficiency of herbicides used in maize for the control of volunteer soybean plants in two phenological stages. The experiment was conducted in a greenhouse, in a completely randomized experimental design in factorial 2 x 11, having as factors two phenological stages and eleven herbicides spray, with four replications. The herbicides spray were composed by: nicosulfuron (40 g ha-1 i.a.); tembotrione (75 g ha-1 i.a.); mesotrione (480 g ha-1 a.i.); atrazine (500 g ha-1 a.i.); 2.4-D (806 g ha-1 a.i.); dicamba (480 g ha-1 a.e.); glufosinate-ammonium (200 g ha-1 a.i.); atrazine + Tembotrione (500 + 75 g ha-1 i.a.); atrazine + mesotrione (500 + 480 g ha-1 a.i.); atrazine + nicosulfuron (500 + 40 g ha-1 i.a.), in addition to a control without application. Visual evaluations were realized at 07, 14, 21, 28 and 35 (DAA) days after application, to determine the control of the voluntary soybean. The results indicate that in both phenological stages, the herbicides mesotrione, nicosulfuron, tembotrione and 2,4-D did not present total control of the soybean. Glufosinate ammonium, atrazine isolated or associated with mesotrione, nicosulfuron and tembotrione 100% controlled the soybean plants from 7 DAA. Dicamba presented total control, in the phenological stage V1 and V3, from 7 DAA and 14 DAA, respectively.
Efficacy and selectivity of metribuzin and diuron in pre-transplanting of tomato crop under with different cover crops species
The tomato plant is an oleraceous that has low tolerance to most of the herbicides used, which limits the use of chemical products in integrated weed management. By this fact, this study was conducted for evaluating the efficacy and selectivity of the metribuzin and diuron, both applied before transplanting the tomato crop, upon different cover crops. Seeds of tomato cv. IPA 6 were planted in trays and transplanted to pots at the stage of two leaves. The species used were: exposed soil (control), Urochloa ruziziensis (0.30 t ha-1), Pennisetum glaucum (0.42 t ha-1) and weed community (0.39 t ha-1), being of herbicide application. The phytotoxicity, efficacy and plant height were evaluated at 7, 14, 21, 28 and 35 days after application (DAA), and in the last evaluation day it was also measured the dry mass of leaves, stem and roots. Regarding the selectivity, the metribuzin provided low phytointoxication in the seedlings, with no effects in the biomass. Despite the efficacy, diuron was not selective to tomato, causing high phytotoxification rates (65 to 100%). It was concluded that the treatment covered with U. ruziziensis, P. glaucum and weed community supplemented the both herbicides action, but only metribuzin was selective when applied in tomato pre-transplanting.
Comparison of horseweed chemical control methods with burndown starting in dry or moist period
Several environmental conditions may directly interferes with the effectiveness of herbicides weed control, therefore, the aim of this research was to evaluate the best climate moment to initiate chemical horseweed (Conyza spp.) control; as well as to evaluate the level of glyphosate tolerance on horseweed population. These trials were conducted in Indianópolis region, Minas Gerais State. The experiment 1 was designed as factorial (2x5) with first factor being the weather period conditions, dry or wet, comparison at first application time of glyphosate + 2,4-D (1,200 + 670 g a.e. ha-1) herbicide. The second factor was the sequential herbicide (g a.e. or a.i. ha-1) application with glyphosate + 2,4-D (1,200 + 670) or paraquat (500), alone or tank mixed with diclosulam (29.4); fluroxypyr (200) alone and an untreated without herbicide application. The experiment 2 aimed to assess the Conyza spp. difficulty level of control to glyphosate herbicide in both trials area by applying sequential applications, 35 days apart, of glyphosate rates (g a.e. ha-1) at 0, 480, 960, 1,920 and 3,840 as well as 2,4-D (670) and glyphosate + 2,4-D (960 + 670). In general, to obtain effective control, either in dry or wet conditions at first application, it was necessary to perform sequential application using glyphosate + 2,4-D at first application followed by a second one, independent of tested herbicides. The horseweed population present in the area showed not to be controlled only by glyphosate herbicide applications.
Copyright (c) 2018 Brazilian Herbicide Journal
Action of pre-emergence herbicides in the initial establishment of seedlings of Savana’s native species
The weed control difficulties has been considered one of the most obstacles to success of forest recovery projects at degraded areas. This experiment aimed to evaluate the different pre‑emergent herbicides effect on seed emergence, seedling survival and initial development of Brazilian native tree species Platypodium elegans, Guazuma ulmifolia, Anadenanthera colubrine and Jacaranda micrantha. The experiment was conducted under greenhouse conditions in a completely randomized design with five replications. The treatments were constituted by the pre-emergence application of the following herbicides and doses: isoxaflutole (75, 150 and 300 g a.i. ha-1), pendimenthalin (500, 1000 and 2000 g a.i. ha-1), trifluralin (600, 1200 and 2400 g a.i. ha-1) and untreated herbicide as a check control. The effect of the herbicides was evaluated for the number of seedlings emerged, number of leaves per seedlings, height of seedlings, diameter of stem and dry matter of root and leaves at 35 days after germination. With the results obtained it was possible to affirm that all herbicides and their respective rates were safe to P. elegans and G. ulmifolia trees. Isoxaflutol at 150 and 300 g a.i. ha-1 was not selective to G. ulmifolia specie. Only trifluralin at 600 and 1200 g a.i. ha-1 sowed selectivity to A. colubrina specie.
Initial growth of melon after the application of post-emergency herbicides
The control of weeds in melon crops is hampered by the lack of selective herbicide information for the crop. The objective of this work was to evaluate the effect of post-emergence herbicide application on yellow melon and toad skin culture. Two experiments (one for each cultivar) were carried out in a completely randomized design with four replications. The treatments were composed by the application of the herbicides in post-emergence: fomesafen (250 g a.i. ha-1); flumioxazin (2000 g a.i. ha-1); fenoxaprop (110 g a.i. ha-1); ioxynil (1005 g a.i. ha-1); carfentrazone (20 g a.i. ha-1); oxyfluorfen (960 g a.i. ha-1); oxadiazon (1200 g a.i. ha-1); and control without application. Phytotoxicity evaluations were performed at 7, 14, 21 and 28 days after application (DAA). The leaf number, stem length, leaf area, stem diameter and total dry matter evaluations were performed at 28 DAA. Oxadiazon and oxyfluorfen herbicides negatively influenced the initial growth of yellow melon. Oxadiazon and ioxynil herbicides negatively influenced the initial growth of toad skin melon. The herbicides flumioxazin and fomesafen did not alter the initial growth of yellow melon and frog skin melon presenting great potential for selectivity tests.
Interaction and efficacy of metusulfuron-methyl and glyphosate tank mixtures
The most common solution for problems on weed control in agricultural system of production is the inclusion of alternative herbicides, applied isolated or in tank mixtures. Thus, this work was carried out with the objective of evaluating the efficacy and interaction of metsulfuron‑methyl and glyphosate tank mixtures for weed control. For that, two independent trials were performed, evaluating different bioindicators, being one monocotyledonous (sourgrass – Digitaria insularis) and one dicotyledonous (morning glory – Ipomoea triloba). Treatments were consequence of a factorial combination 5x5, corresponding the first factor to five rates of glyphosate (0, 180, 360, 540 and 720 g a.e. ha-1) and the second factor to five rates of metsulfuron‑methyl (0; 1.2; 2.4; 3.6 and 4.8 g a.i. ha-1). In both experiments, randomized blocks were adopted as experimental design, with six replicates. The mixture of glyphosate and metsulfuron-methyl was considered additive on sourgrass for all the rates considered; for morning glory, including metsulturon-methyl on tank mixture increased total control, however with magnitude lower than expected, what denotes antagonist behavior of mixture.
Carta dos editores-chefes da RBH Nos últimos anos, a Revista Brasileira de Herbicidas - RBH tem sido uma das referências na divulgação de conhecimento científico em controle químico de plantas daninhas e áreas afins, por meio de publicações de artigos originais e inéditos. Isso só tem sido possível devido ao grande esforço de toda comunidade científica por meio de submissão de bons resultados de pesquisa, auxílio com os pareceres ad hoc e contribuições no conselho editorial do periódico. Para o ano de 2018, a comissão editorial entende que é necessário a modernização da RBH visando atender as novas expectativas de profissionais e produtores quanto ao manejo de plantas daninhas. O uso de herbicidas não pode mais ser visto como única solução de controle, mas como ferramenta importante e a revista pretende expandir seu escopo para diferentes métodos de controle. Desta maneira, a comissão editorial irá propor durante todo o ano uma profunda discussão sobre os objetivos do periódico, a ampliação do escopo da revista, bem como a definição do novo título para o periódico, considerando as decisões que serão tomadas. No primeiro número de 2018 são publicadas 9 revisões de literatura sobre relevantes temas para toda a comunidade científica e escrita por renomados pesquisadores brasileiros. Destacamos as revisões sobre métodos de controle de planta daninhas em sistemas orgânicos, assunto até então pouco abordado pela revista e que representa parte das mudanças que propomos para o periódico que procurará ser referência brasileira no Controle de Plantas Daninhas. Carta da Presidente do XXXI CBCPD Em 2018 a cidade do Rio de Janeiro, após 56 anos, terá o privilégio de sediar novamente o Congresso Brasileiro da Ciência das Plantas Daninhas (CBCPD), desta vez em sua 31º edição. Durante cinco dias, o XXXI CBCPD será o cenário para aprimoramento dos principais caminhos a serem seguidos por produtores, empresários e cientistas da área da Ciência das Plantas Daninhas. O evento acontecerá entre os dias 27 e 31 de agosto de 2018, no Centro de Convenções Riocentro. Nossa expectativa de público é de aproximadamente 1000 congressistas, entre estudantes, técnicos, empresários, professores e pesquisadores envolvidos com a Ciência das Plantas Daninhas, além de engenheiros agrônomos, consultores e produtores rurais. O XXXI CBCPD, cujo tema central será os DESAFIOS E SUSTENTABILIDADE NO MANEJO DE PLANTAS DANINHAS, contará com uma programação distribuída em palestras, talk shows e painéis ministrados por renomados palestrantes de diversas instituições de pesquisa do Brasil e do mundo, além de sessões orais e pôsteres, para apresentação e discussão dos principais trabalhos de pesquisa desenvolvidos na área da Ciência das Plantas Daninhas. Nos tempos atuais, se torna indissociável a discussão de um manejo adequado de plantas daninhas aliado com a sustentabilidade do sistema produtivo. O aprofundamento nos estudos das diversas áreas da Ciência das Plantas Daninhas tem permitido significativos avanços nos últimos anos, mas também trazem grandes desafios. Desta forma, o XXXI CBCPD será uma oportunidade ímpar para se discutir com colegas, de todo o mundo, que irão partilhar inovações e soluções em suas respectivas áreas de atuação. Você está convidado a participar e contribuir para o sucesso deste evento! O Rio de Janeiro espera por você! Carta da Presidente da SBCPD A Sociedade Brasileira de Ciência das Plantas Daninhas (SBCPD) aproveita a oportunidade para agradecer a todos os envolvidos tanto na organização do XXXI CBCPD, como nos Simpósios que ocorreram em 2017, no III Campeonato Brasileiro de Herbologia, nas publicações vinculadas a SBCPD – Revistas e Boletins e a todos que contribuem nos nossos comitês técnicos. Sentimos que com estas ações estamos cumprindo com uma das nossas mais importantes missões que é congregar professores, cientistas, técnicos, estudantes e pessoas físicas e jurídicas que se interessam em promover e incentivar a pesquisa, o ensino e a extensão na área da Ciência das Plantas Daninhas e sua aplicação em benefício da humanidade.
Seed treatment with salicylic acid in the tolerance of wheat to flumioxazin
The seed treatment with safeners may increase the tolerance of crops to herbicides. An experiment was conducted to evaluate the effect of seed treatment with salicylic acid on the tolerance of wheat to flumioxazin. The design was completely randomized, with four replications. The treatments were arranged in a 2 x 6 factorial, where the first factor corresponded to the absence or presence of seed treatment with salicylic acid and the second factor to the doses of flumioxazin (0; 10; 20; 30; 40 and 50 g ha-1 a.i.) in pre-emergence application. The seed treatment with salicylic acid reduced the toxicity of wheat plants to 7, 14 and 35 days after emergence. The number of fertile tillers was not affected by the treatments. Increasing the dose of flumioxazin negatively affected the growth variables evaluated (dry matter of the aerial part, height of fertile tillers and dry matter of spikelets), and the salicylic acid positively influenced the dry matter of the spikelets. The flumioxazin causes intoxication and reduces the growth of wheat. Salicylic acid is an alternative to alleviate the stress caused by the herbicide, increasing the tolerance of the crop.
Sourgrass response to mixtures of haloxyfop and glyphosate with synthetic auxinic herbicides
In Brazil, weed resistance to glyphosate is increasing for both broadleaf and grass species in the same area, making necessary to develop effective management strategies. The objective of this study was to determine the efficacy of the herbicide haloxyfop-p-methyl plus glyphosate in Digitaria insularis (sourgrass) when mixed with auxin mimics herbicides. The experiments were carried out in two locations, Mogi Mirim/SP and Indianópolis/MG, in a randomized complete block design, with four replications. The herbicide treatments were: haloxyfop-p-methyl (124 g ai ha-1); haloxyfop‑p‑methyl + halauxifen-methyl + diclosulam (124 + 30.6 g ai ha-1); haloxyfop-p-methyl + dicamba (124 + 560 g ai ha-1); haloxyfop-p-methyl + 2,4-D (124 + 1000 g ai ha-1); haloxyfop-p-methyl + halauxifen-methyl (124 + 5 g ai ha-1) and haloxyfop-p-methyl + diclosulam (124 + 25 g ai ha-1) and untreated without application. All herbicide treatments were applied with glyphosate at 1440 g ai ha-1. The applications were performed when sourgrass plants were in 4 to 6 tillers. Halauxifen-methyl did not adversely affect the control of sourgrass when applied with haloxyfop-p-methyl and glyphosate, resulting in a control of 82 and 100% for Mogi Mirim and Indianópolis, respectively. However, the control of sourgrass with haloxyfop-p-methyl plus glyphosate was not acceptable when mixed with dicamba or 2,4-D, with controls inferior than 70%. In mix populations of broad-leaves and grass areas, halauxifen-methyl may be a good option to be applied associated with haloxypop-p-methyl and glyphosate to control these weeds without diminishing performance.
Efficiency and deposition of herbicides in onion in function of adjuvant and carrier volume
The objective, of this work, was evaluated the effect of carrier volume and use of activator adjuvant on the weed control and deposition of herbicide treatment with ioxynil + clethodim in onion plants. The experiment consisted by six treatments and five replications, organized in factorial scheme 2 x 3, that is a combination of two levels of adjuvant (with an without) with three application rates (100, 150 e 200 L ha-1). The treatments were applicate in post-emergence, after the onion rooted in and the weeds were four to six leaves stage. The treatments not promote intoxication in onion crop. There are the tendency to improve Cyclospermum leptophyllum and Polygonum persicaria control with adjuvant use, however without significate effect. The control level and deposition were not affect for application rate evaluated. Concluded that reduced application rate no compromised the efficiency and deposition of ioxynil + clethodim herbicides.
Initial tolerance of cowpea to herbicides applied in pre-emergence
Weeds that are not well managed can cause losses of more than 90% in the final production of the crops, and for cowpea there is a certain difficulty to control them, since there are no herbicides registered for the crop. The objective of this study was to evaluate the initial tolerance of cowpea to herbicide application in pre-emergence of the crop. The experiment was conducted in a greenhouse, in a completely randomized design, with three replications. The treatments evaluated were sulfentrazone (200 g ha-1), S-metolachlor (768 g ha-1), [clomazone + carfentrazone] ([480 + 12] g ha-1), imazethapyr (50 g ha-1), flumioxazin (50 g ha-1), sulfentrazone + S-metolachlor (200 + 768 g ha-1) and one control. All herbicides were applied after sowing cowpea. Plant phytotoxication, plant count, plant height, dry shoot and root mass were evaluated. The mixture of sulfentrazone + S-metolachlor herbicides promoted irreversible crop damage. Cowpea does not tolerate flumioxazin or mixtures involving the use of this herbicide. It can be observed that the cowpea presented intermediate tolerance to the herbicides sulfentrazone and diclosulam. The herbicides S-metolachlor, imazethapyr and cloransulam presented potential use in pre-emergence applications of cowpea.
Effectiveness of herbicides isolated or in mixture in control of the exotic plant invasive Urochloa subquadripara
The objective of this study was to evaluate the efficacy of glyphosate, saflufenacil, imazamox, imazapyr and penoxsulam alone or in combination in the control of Urochloa subquadripara. To do so, in greenhouse, five plant pointers were transplanted into 2.5 liter boxes containing 5.0 cm of soil, washed coarse sand and organic compound (1:1:1; ratio). After 30 days, the herbicides with costal sprayer were applied at a constant pressure of 25 p.s.i. maintained by CO2, with consumption of syrup equivalent to 200 L ha-1. The evaluations were performed through efficacy notes at 3, 7, 15, 21, 30, 45 and 60 days after application (DAA). The herbicides glyphosate and imazamox, isolated, showed excellent control (100%) of U. subquadripara, whereas imazapyr and penoxsulam (48.0 g ha-1) presented satisfactory control with 80 to 85% control efficacy. The herbicides glyphosate, imazamox and imazapyr (isolated and mixed), saflufenacil + glyphosate (mixture) and penoxsulam + glyphosate (mixture) can be used in management programs of this invasive aquatic plant.
Ricardo Henrique da Cruz Poliseli Scannavino
Effectiveness of atrazine on populations of capim navalha and selectivity of two varieties of pastagem
Paspalum virgatum L. is a grass weed common in pasture and has difficult control, mainly due to its similarity to forage. Conventional techniques such as grazing and replanting of pasture have been unsatisfactory in the control of this weed. The objective of this work was to evaluate the control of the razor-blade grass (P. virgatum L.) at the pre-emergence atrazine, by means of a dose‑response curve and the selectivity of this herbicide in the pastures of Brachiaria brizantha cv. Marandu and Panicum maximum cv. Mombasa. Three independent experiments were carried out with each species on two types of soils (Dystrophic Yellow Red Latosol - LVAd with loamy clay texture and Dystrophic Yellow Red Argisol - loamy texture PVAd), using the percentage grading scale to verify the control of the and herbage phytotoxicity and dry mass at the end of the experiments. Atrazine controlled the razor blade from 15 days after application (DAA) at doses below the manufacturer’s recommendation (250 and 500 g ha-1 i.a.). However, despite the phytotoxicity symptoms caused by atrazine, there was a resumption of growth at 60 DAA for both B. brizantha cv. Marandu and P. maximum cv. Mombasa. There was less phytotoxicity to pastures in the soil of loamy clay texture than the loamy texture soil. The atrazine provided efficient control of P. virgatum L. (500 g ha-1 i.a.) when applied in pre-emergence and selectivity to B. brizantha cv. Marandu (<2,000 g ha-1 i.a.) and P. maximum cv. Mombasa (<500 g ha-1 i.a.).
Use of biostimulant in the reversion of injury caused by glyphosate on conventional corn plants
Conventional corn cultivation has been taking up space in the national agricultural panorama due to the difficulty of controlling the corn in subsequent crops. However, glyphosate drift in adjacent crops has become a concern among producers and technicians. Thus the experiment was installed to evaluate the effect of low doses of glyphosate on the crop and the ability of a plant hormone-based biostimulant to reverse the injuries caused by the herbicide, evaluating the morphological characteristics and photosynthetic rate of corn plants. It was used a completely randomized design with four replicates in factorial arrangement 5 X 2, with the first factor corresponding to five doses of glyphosate (0, 10, 20, 30 and 40 g e.a ha-1), and the second, the absence and presence of the biostimulant. The evaluated characteristics were phytotoxification, stalk diameter, plant height and fresh root and shoot mass, SPAD index and photosynthetic rate. The higher dose of glyphosate resulted in higher phytointoxication, plants with lower height and lower SPAD index. Biostimulant provided increases in stalk diameter, SPAD index and photosynthetic rate. The presence of biostimulant did not provide a repairing effect on the deleterious effects caused by glyphosate in conventional corn plants.
Biostimulants derived from Ascophyllum nodosum associated of glyphosate in agronomic characteristics of soybean RR
Glyphosate is the main herbicide in weed control in soybean. However, phytotoxicity symptoms after application of this herbicide are reported in RR soybean. In this context, biostimulants can potentiate the metabolic activities of the plant in function of the bioregulators, amino acids and nutrients present in its formulation, becoming an alternative to minimize the phytotoxic effects of glyphosate. Thus, the objective of this work was to identify the use of biostimulants, derived from Ascophyllum nodosum, associated to the herbicide glyphosate in the increments of the agronomic characteristics of the soybean crop. For this, an experiment was conducted in the 2014/15 harvest in Montividiu-GO with thirteen treatments, resulting from the combination of biostimulants MC Extra, MC Cream and Megafol with the herbicide glyphosate (Roundup Transorb). The results allowed us to conclude that the five-year combined application of the herbicide with MC Extra and Megafol provided greater increases in grain yield of soybean. MC Cream provided higher grain yield at 15 days after application of glyphosate. Thus, the biostimulants proved the potential of use in the soybean crop.
Phytosociology of weeds in function of different managements of winter cover
In order to increase the efficiency of the use of cover crops, it is important to know which species present the greatest suppression of weeds and if the cover crop management method affects the suppression effect. The goal, with this work, was to evaluate the suppressive effect of different winter cover crops and their different managements through the use of phytosociological indices. The experimental design used was of randomized blocks conducted in a 4 × 3 factorial scheme with four replicates. The first factor was constituted by different cover crop species: white oats (Avena sativa), wild radish (Raphanus raphanistrum), vetch (Vicia sativa) and fallow; the second factor was constituted by the cover crop management: chemical control, lodging and no management. The dry matter of the cover crops was quantified at the moment of cover crop management. The weed community was evaluated 75 days after the cover crop management took place, with the assessment of the number of weeds, weed dry matter, relative frequency, relative density, relative dominance, and importance value index (IVI). Oats produces the greatest amount of dry matter. The weed community is compos of 31 species. In the chemical management, oat and vetch cover crops are the ones that suppress the greatest number of weeds. In general, the desiccation allow to a greater number of weeds, but with decrease dry matter. The species Spermacoce latifolia, Conyza bonariensis and Sida rhombifolia present high IVI values. The desiccation of the cover crops may favor herbicide-tolerant species which excel in the environment.
Initial growth of sugarcane pre-sprouted seedlings in two types of application of herbicides
The specie Cyperus rotundus is among the weeds most difficult to control and can cause high losses in the sugarcane crop. The practices adopted in the culture guarantee the values of yield, among them, is the weed management. The objective of this work was to evaluate the initial growth of sugarcane pre-sprouted seedlings submitted to herbicide application before or after planting. Two experiments (pre and post-planting) were conducted in greenhouse, in a completely randomized design, with four replications. The treatments corresponded to the herbicides applied in three pre-planting doses: sulfentrazone (400, 800 and 1,600 g a.i. ha-1), diclosulam (96.6, 193.17 and 386.34 g a.i. ha-1), imazapic (66.5, 133 and 266 g a.i. ha-1) and imazapyr (250, 500 and 1,000 g e.a. ha-1) and post-planting: halosulfuron (56.25, 112.5 and 225 g a.i. ha-1), ethoxysulfuron (67.5, 135 and 270 g a.i. ha-1), 2,4-D (670, 1,340 and 2,680 g a.e. ha-1) and MSMA (987.5, 1,975 and 3,950 g a.i. ha-1). In addition to two controls without herbicide application. The crop injury, height, diameter, number of leaves, number of tillers, chlorophyll content, leaf area, dry mass of shoot and root were evaluated. Post-planting treatments were considered selective, since the crop injury were low, and the other parameters evaluated were not different from the control. For pre-planting applications, crop injury were observed up to 60 days after application (DAA) for sulfentrazone.
Efficacy of [atrazine + mesotrione] in control of weed in corn
To increase the weed control spectrum in corn, the herbicides formulation with active principles of different mechanisms of action is an important alternative. With the objective of evaluating the control promoted by the new herbicide Calaris®, composed by the mixture of [atrazine + mesotrione] applied in postemergence of weeds, alone or in combination with other herbicides, experiments were conducted in a greenhouse, one for each weed evaluated, in a completely randomized design with 16 treatments and four replications. Weed seeds of Conyza bonariensis, Urochloa decumbens, Cenchrus echinatus, Digitaria horizontalis, Urochloa plantaginea, Ipomoea grandifolia, Euphorbia heterophylla, Bidens pilosa, Glycine max e Commelina benghalensis were sown in pots with a volume of 5 dm3 at density of 20 seeds per pot. The herbicide treatments were composed by [atrazine + mesotrione] applied in post-emergence in mixture or not with glyphosate, tembotrione and nicosulfuron; atrazine alone or in combination with glyphosate, mesotrione, tembotrione and nicusulfuron; glyphosate isolated and control without application. The application of the treatments of each experiment was carried out at different dates, considering the stage of development of weeds. Control percentage was evaluated in relation to weeds at 7, 14 and 28 days after application of the herbicides. The new herbicide formulation [atrazine + mesotrione] showed effective control in most of the weeds evaluated, except Cenchrus echinatus e Urochloa decumbens, however, the control was effective when combined with other herbicides, especially with glyphosate.
Phytoremediation of soil contaminated with ALS and PS II inhibitors herbicides
Alternative to decontaminate the soil is the phytoremediation practice. In this way, this study aimed to evaluate the phytoremediation potential of the following species: vetch, radish, cereal rye, black soybean and colonião grass, grown in a soil contaminated with atrazine and chlorimuron ethyl + sulfometuron-methyl. The herbicides were applied in pre-emergence of the species. Two experiments were installed, the first one tested the phytoremediation potential of the species and the second one used the cucumber as bioindicator culture to prove if the soil had been depolluted. The variables evaluated at 40 days after emergence (DAE) were: phytotoxicity (%), height (cm) and dry mass of the aerial part of the plants (g). There is a great variation in the selectivity of the cultures to the two herbicides, and the chlorimuron-ethyl + sulfometuron-methyl mixture presented the highest phytotoxicity symptoms, both for the phytoremediation species and for the bioindicator culture. The results allowed to conclude that the management the black soybean presented a greater potential of phytoremediation of soil contaminated with chlorimuron-ethyl + sulfometuron-methyl and that the colonium grass was the species that demonstrated satisfactory potential as phytoremediation plant of contaminated soil with atrazine.
Tolerance of onion implanted by direct sowing to flumioxazin applied in initial post-emergency
Weed management in onion culture is a fundamental practice to reduce or eliminate interference from weeds community, since the crop, especially in direct sowing system, presents slow initial growth and low competitive capacity. In this sense, for the correct use of the herbicides it is necessary to know the effects provided by the doses in the onion crop as well as to quantify this effect for the different phenological stages. In view of the above, the purpose of this study was to evaluate the tolerance of the onion in a system of direct sowing to flumioxazin applied in the initial post-emergence in different phonological stages. The experiment was carried out in a completely randomized design, with four replications in factorial arrangement 4 × 5 + 1, the first factor being the flumioxazin (2.5, 5.0, 7.5 and 10 g ha-1) doses (whip, 1st leaf, 2nd leaf, 3rd leaf and 4th leaf), as well as additional treatment (control without application). Leaf height, shoot dry matter, diameter and weight of bulb’s were evaluated. Application of flumioxazin in post-emergence of onion reduced all the variables assessed when held up until the stage of two true leaves. Negative effects were greater with increase of the dose of the herbicide in the initial stages of growth of the onio. On the other hand, flumioxazin applied from the third dose-independent true leaf did not affect any of the analyzed parameters. After the emission of the third leaf the onion presented tolerance to flumioxazin.
Weed managemet systems using the new herbicide pyroxasulfone aiming at grass control in soybeans
Due to the increasing number of grasses selected for resistance to the EPSPS and ACCase inhibitors, new alternatives with effective and selective herbicides from different mechanisms of action must be developed. This work was carried out to evaluate weed management systems containing the new herbicide pyroxasulfone aiming at controlling goosegrass (Eleusine indica) and sourgrass (Digitaria insularis) in applications immediately prior to soybean sowing. The design used for the randomized blocks, with eleven treatments and four replicates. All residual herbicides were applied at the second burndown application, seven days prior to soybean sowing. In each system, two sequential burndown applications followed by one post-emergence application were sprayed in each treatment. The best level of initial (up 28 days after crop sowing) control of goosegrass was observed with treatments with pyroxasulfone, although after the third herbicide application all systems provided excellent control of this weed. Concerning to sourgrass, the third post-emergence application did not provide any weed control improvement and the best results were found where residual herbicides were applied at the second burndown application, except with chlorimuron-ethyl. Associations with pyroxasulfone with other residual herbicides is an excellent option to provide simultaneous control of goosegrass and sourgrass, and those treatments are selective for soybeans.
Persistence of imazethapyr in the soil and phytotoxicity to corn seeded as succeeding crop
This work was carried out to evaluate imazethapyr persistence in the soil, as well as the phytotoxicity of this herbicide to the corn crop seeded in succession. Treatments were organized according to a factorial scheme with two types of soil (S; clay and sandy), three regimes of irrigation (I; daily, weekly and no irrigation) and four timing (T) of herbicide application (90, 60 and 30 days prior to corn seeding, besides check plots without application). For that, imazethapyr was applied at the unique rate of 100 g ha-1. Experimental design of completely randomized blocks was adopted, with four replicates and 96 plots. Each plot consisted of a 8,5L plastic pot, fulfilled with sieved soil. In synthesis, adequate water availability between herbicide application and corn seeding granted the lowest levels of crop phytotoxicity and the highest yield of dry matter. In clay soil, the lowest levels of crop phytotoxicity were observed. Thus, it was possible to infer that imazethapyr persistence in the soil is reduced whenever there are higher microbial activity, which is enhanced by higher temperature, water availability and, in lower degree, by the time of herbicide persistence in the soil.
Manejo químico de Urochloa ruziziensis consorciado com soja na savana de Roraima
The objective of the study was to evaluate the chemical management of Urochloa ruziziensis intercropped with soybean under no tillage system in the Roraima savanna. The experiment was conducted in an experimental area located in the municipality of Boa Vista - RR, in the year 2015. The treatments consisted of the combination of four doses of the herbicide glyphosate (720; 1.200; 1.680 and 2.160 g ha-1 of i.a) sprayed prior to sowing the soybean as a desiccant and five doses of the herbicide fenoxaprop-p-ethyl (0; 38.5; 77; 115.5 and 154 g ha-1 of i.a) sprayed 32 days after emergence of the post-emergence crop. The experimental design was a randomized complete block in the subdivided plots scheme, with four replications. For the soybean crop were evaluated the height of plants, height of insertion of the first pod, number of pods per plant, number of grains per pod, mass of 100 grains and grain yield in kg ha-1. The fresh and dry forage mass was evaluated for U. ruziziensis at 70 days after soybean harvest and expressed in kg ha-1. It was concluded that only the application of glyphosate at a dose of 1387,64 g ha-1, applied in post-emergence in the soybean crop, guarantees maximum grain yield (3660,07 kg ha-1) and of fresh mass (10136,22 kg ha-1) and dry matter (2404,63 kg ha-1) of U. ruziziensis for soil cover for the next planting, necessary to guarantee the sustainability of the productive system.
Effect of light reduction on herbicides selectivity and yield of wheat
The solar radiation reduction incident on the terrestrial surface can changes the vegetal behavior and the herbicide selectivity. The aim of this work was to evaluate the herbicide selectivity bentazon, iodosulfuron-methyl-sodium and grain yield of wheat under conditions of reduction of luminosity in different phenological stages of the crop. Two experiments were conducted, the first (I) under controlled conditions and the second (II) in field. In both experiments, wheat was evaluated according to the herbicide application (bentazone, 900 g ha-1 a.i., iodosulfuron-methyl sodium, 5 g ha-1 a.i., and control, without herbicide application) and the variation of the light rate (control; light reduction during the entire cycle; reduction in the initial stage, from emergence to three expanded leaves; reduction in the vegetative stage, three expanded leaves to complete emergence of the inflorescence; and reduction in the reproductive phase, from inflorescence to harvest. The results show that light reduction alters morphophysiological characteristics of wheat, increases plant height, reduces transpiration and stomatal conductance rate, but does not interfere with cereal photosynthesis. However, grain yield is negatively affected by the reduction of light during the vegetative stage, ontogenetic period that coincides with the formation of the main composites of crop yield. The evaluated herbicides are selective to wheat, with or without reduction of luminosity.
Effectiveness of herbicides isolated and in associations in the control at post-emergence of weeds
It is essential the rotation of mechanisms of action in the management of glyphosate resistant weeds, in this context the use of ALS inhibitor herbicides in association can aid in the control. The aim of this work was to evaluate the efficacy of sulfometuron, chlorimuron and other sulfonylureas, isolated and in associations in the control of Wild Poinsettia, Morning Glory and Greater Beggarticks. Three greenhouse experiments were carried out in a completely randomized design with four replications. The treatments corresponded to the herbicides applied in post-emergence of the weed plus the control (without application), when these were with two completely developed leaves. The results showed that sulfometuron (15 g ha-1 a.i.) + chlorimuron (20 g ha-1 a.i.) + glyphosate (960 g ha-1 a.e.) was effective in the control of Wild Poinsettia, and halosulfuron treatment (80 g ha-1 a.i.) + glyphosate (960 g ha-1 a.e.) provided a control of 76.25%. The application of sulfometuron (15 g ha-1 a.i.) + chlorimuron (20 g ha-1 a.i.) + glyphosate (960 g ha-1 a.e.) was effective in the control of Morning Glory. All herbicides treatments were effective in the post-emergence control of Greater Beggarticks.
Selectivity of associations and rates of the herbicides in wheat post emergence
The main weeds in wheat are wild radish and ryegrass, and its post-emergence control is based on herbicides inhibiting the enzyme acetolactate synthase (ALS) and acetyl coenzyme A carboxase (ACCase), which as a function of resistance limits the control options. Herbicide combinations have been used for post-emergence of wheat; however, the effects of herbicidal combinations are poorly understood. The objective of this work was to evaluate the selectivity of wheat to herbicide associations and rates applied in post-emergence. Three field experiments were carried out in a no tillage system, in a randomized complete block design with three replicates. The experiments were conducted in Santa Bárbara do Sul-RS, Cruz Alta-RS and Tupanciretã-RS. Rates and associations between the 2,4-D herbicides, metsulfuron-methyl, iodosulfuron, pyroxsulam and saflufenacil applied in wheat tillering were studied. The evaluated variables were phytotoxicity at seven, 14, 21 and 35 days after application (DAA), yield (kg ha-1) and hectoliter weigh (HW). The data were analyzed together. At 35 DAA, the highest phytotoxicities were observed for metsulfuron methyl at the dose of 9 g a.i. ha-1 and for saflufenacil associated with metsulfuron methyl. The results of yield demonstrate that the association between 2,4-D and metsulfuron-methyl, saflufenacil isolated or associated with metsulfuron-methyl, and iodosulfuron are selective for wheat. Metsulfuron methyl at rates of 6 and 9 g a.i. ha-1 and pyroxsulam caused a significant reduction in wheat yield and were not considered selective. However, the hectoliter weight of the grains was not influenced by herbicides used of this study.
Herbicide association applied to control weeds in bean of black type
Black bean is one of the main grains grown in Brazil, with economic, social and cultural importance. Grain productivity losses due to competition with weeds, in particular Digitaria ciliaris (summergrass) and Urochloa plantaginea (signalgrass) can reach levels of up to 80% if neither Control is adopted. The objective of this study was to evaluate the efficacy and selectivity of herbicides applied in pre and post emergence of black beans. The experimental design was a randomized block design, with four replications. The herbicides used were fomesafen (250 g ha-1 a.i), s-metolachlor (1200 g ha-1), oxyfluorfen (480 g ha-1 of a.i), clomazone (1000 g ha-1 of a.i), pendimentalin (250 g ha-1 of a.i), imazamox (42 g ha-1 of a.i), bentazon (720 g ha-1 of a.i), bentazon + imazamox (600 + 28 g ha-1 of a.i), flumioxazin (25 g ha-1 of a.i), fluazifop-p-buthyl + fomesafen (250 +250 g ha-1 of a.i), followed by two additional controls, one weed and one infested. O oxyfluorfen presented the highest levels of phytotoxicity to BRS Campeiro bean, which resulted in a negative effect on components of grain yield, together with the infested control, s-metolachlor, pendimentalin, flumioxazin, fomesafen and bentazon. The commercial mixture of bentazon + imazamox presented low phytotoxicity, the best results of the components of grain yield, together with a good control of the summergrass and the signalgrass.
Chemical control alternatives for glyphosate-resistant sourgrass using hebicides indicated for corn and cotton crop
In Brazil cropping systems is common a rotation between soybean, corn and / or cotton, all resistant to glyphosate, which favor the selection of glyphosate resistant sourgrass populations (Digitaria insularis). Little is known about alternative chemical control of D. insularis registered for the corn and cotton crops. Thus, it is relevant to investigate herbicides with alternative mode of action, applied in pre and post-emergence conditions, to be used for efficient control of the glyphosate resistant sourgrass biotype (D. insularis). The experiment was conducted in greenhouse, from September to December of 2014, using a glyphosate resistant D. Insularis biotype. The statistical design was randomized blocks with four replications. The application occurred when sourgrass plants were at the 1 to 2 tillers stage for post-emergent and at pre-emergence for the pre-emergent herbicides. The treatments which showed the best results in post-emergence conditions were the nicosulfuron, imazapic + imazapyr, atrazine, haloxyfop-methyl and tepraloxydim herbicides. Atrazine, isoxaflutole, S-metolachlor, clomazone, diuron and flumioxazin presented themselves as effective pre-emergents for controlling this species.
Copyright (c) 2017 Brazilian Herbicide Journal
Effect of paraquat and glyphosate for the control of poaceae and convolvulaceae specimens on hydric deficit
The use of herbicides is very used by growers for the control of weeds. However, their effectiveness can be compromised by the reduction of water in the atmosphere, influencing its uptake, translocation and metabolism in plants. The objective of this study was to evaluate the efficacy of herbicides paraquat (Gramoxone) and glyphosate (Roundup Original) for the control of Urochloa decumbens (Stapf) R. D. Webster (Poaceae) and Merremia cissoides (Lam.) Hallier f. (Convolvulaceae) when submitted to hydric deficit. The experiment was conducted in greenhouse conditions with completely randomized design in factorial 5×3, considering three replicates. It was considered five induction conditions of hydric deficit (0, 1, 3, 5 and 7 days) and three treatments (paraquat, glyphosate and untreated check, only water). The evaluations were performed at 2, 5, 7, 10, 14 and 21 days after treatment application. At 21 days, it was also determined the dry weight of weeds. From the results obtained, it was observed that from 5 days without irrigation the herbicides reduced their effectiveness for the control of weeds.
Biochar impact on herbicides behavior in the soils: an approach in Brazil
The application of biochar to soils because of beneficial effects is proven by many international researchers and this can increase herbicides sorption and reduce effectiveness on weed management. Positive impacts are reported in relation to the environmental behavior of herbicides, since the increase of the sorption reduces the leaching of these products to groundwater. Negative impacts are reported in relation to agronomic management of herbicides, since the sorption increase reduces the availability of these products in the soil, reducing the residual effect for weed control. In Brazil, biochar is produced by several private companies and pyrolysis units, but the cost for production is still very high, probably due to lack of government incentive, low use of producers, and awareness of the benefits. Although biochar has been used for several decades in other countries, in Brazil there are still few studies developed by soil researchers, and biochar efficiency on the bioavailability of herbicide in the soil is still unknown by many weed science Brazilian researchers. Against the above, the objective of this review was to evaluate the bioavailability of herbicides in biochar-amended soils and highlight the research with biochar in Brazilian conditions, besides presenting the benefits to soil with biochar addition. Little is known about the herbicides behavior in Brazilian soils amended with biochar, which can be used with greater intensity in modern agriculture. So more research is needed under our conditions to really we understand the dynamics of this product in the soil.
Ethoxysulfuron on weed control in common bean crop
It is necessary to identify new herbicides with a wide spectrum of weed control for bean crops, and have an adequate security margin for this crop. The main objectives of this work were to evaluate the potential use of ethoxysulfuron herbicide on controlling weeds and three soybean cultivars between bean crop, as the tolerance of IAC Imperador bean cultivar to this herbicide. An experiment was conducted on field with a split-plot design. At the whole plot were allocated the doses of ethoxysulfuron (0; 10.4; 20.8; 41.6; 62.5; and 83.3 g ha-1) and, at the subplots, the three soybean cultivars (AMS Tibagi, Dow 5D634 e Nidera 5909) were allocated with weeds (Bidens spp., Ipomoea spp.). Additionally, it was included an extra treatment without weeds and herbicide application. The Ethoxysulfuron controlled Ipomoea spp. and soybean plants, but didn’t control Bidens spp. It was found a differential tolerance between the soybean cultivars, and the AMS Tibagi cultivar showed to be slightly tolerant. Doses up to 20.8 g ha-1 are sufficient to satisfactorily control Ipomoea spp. and soybean plants, but not for Bidens spp. The herbicide provided an increment of bean yield, however, it wasn’t enough to achieve the extra treatment yield. The IAC Imperador bean cultivar showed moderate tolerance to ethoxysulfuron, and its plants can recover quickly after any injurie.
Leaching sulfentrazone in North soils of Minas Gerais cultivated with sugar cane
In view of the intense use of herbicides, coupled with the scarcity of information regarding the residual effect of these compounds in some Brazilian soils, the objective of this study was to evaluate the leaching potential by means of biological assays of the sulfentrazone herbicide in the 0- 20 and 20-40 cm of soils of the North of Minas Gerais cultivated with sugarcane. The experiment was conducted in the split - plot scheme, in a completely randomized design. The plots were composed of PVC columns, filled with soils of Salinas (MG) and Pirapora (MG), and the subplots, for 10 depths with intervals of 5 cm (0-5, 5-10, 10-15, 15- 20, 20-25, 25-30, 30-35, 35-40, 40-45 and 45-50 cm). At the top of the columns the dose of 600 g a.i. ha-1 of sulfentrazone was applied and 12 hours later, 60 mm of rainfall was simulated. After 72 hours, the columns were placed horizontally and opened longitudinally, divided into subsections of 5.0 cm. The evaluation of intoxication of the test plants was performed visually at 21 days after sowing, after which the aerial part of the bioindicator plants was cut. Symptoms of sulfentrazone intoxication were observed in the bioindicator plants up to 10 cm deep in the superficial layer (0-20 cm) and up to 15 cm in the deepest layer (20-40 cm) of both soils. In the two soil layers the sulfentrazone was detected in a higher concentration in the first five centimeters. Greater mobility of the herbicide was verified in the deeper layer of the soil (20-40 cm) indicating a greater leaching potential of the herbicide under these conditions.
Efficacy of halauxifen-methyl formulations to control volunteer soybean DAS-444Ø6-6 (Enlist E3TM)
Volunteer soybean control is a fundamental requirement, mainly because of the rust inoculum disease present in these plants. Several herbicides are available that will control volunteer soybean in the vegetative growth stage, however farmers may delay application of control measures until the flowering growth stage, where the control can be more difficult With the introduction of 2,4-D tolerant soybean (DAS-444Ø6-6 - Enlist E3TM), other methods of chemical control need to be identified. The objective of this research was to determine the efficacy to control volunteer DAS-444Ø6-6 soybean using alternative herbicides. A field experiment was conducted in Cascavel-PR, using a randomized complete block design, with three replications. Herbicides treatments applied were halauxifen-methyl + pyroxsulam at 5 g a.i. ha-1 + 18 g ai ha-1, halauxifen-methyl + diclosulam at 5 g a.i. ha-1 + 25 g ai ha-1 and halauxifen-methyl + 2,4-D at 5 g a.i. ha-1 + 783 g ai ha-1, and the standard paraquat 400 g ai ha-1. The treatments were applied post emergence to soybean at the R2 growth stage. Paraquat and the treatment formulations containing halauxifen-methyl provided effective control of volunteer DAS-444Ø6-6 soybean sprayed at advanced growth stage (R2).
Potential use of the new herbicide indaziflam in banana orchards
Weed control is one of the capital requirements to provide suitable growth and establishment of banana orchards. However, very few options of herbicides are available for this crop. From this context, the objective of this work is to evaluate weed control and selectivity of the new herbicide indaziflam apllied pre-emergence in a directed spray to the inter rows area of banana orchards, targeting the weeds hairy flebane (Conyza bonariensis), Jamaican crabgrass (Digitaria horizontalis) and spiny sandbur (Cenchrus echinatus). A field experiment was carried out in a randomized blocks desingn, with four replicates. Treatments were composed by indaziflam applied pre-emergence of weeds at doses of 50, 75, 100 and 125 g ha-1; glyphosate applied post-emergence at 1920 g a.e. ha-1, and two controls: weedy and absolute (weed-free, with no herbicide application). Indaziflam at 75, 100 and 125 g ha-1 provided excellent control of all main weeds in the experimental area for a period of 120 days. All rates of indaziflam applied pre-emergence of weeds were considered as selectives for banana trees, since no visual injury or crop yield effect was observed. Indaziflam presents potential as a new herbicide alternative in banana orchards.
Control in soybean pre plant of volunteer glyphosate and ammonium glufosinate tolerant cotton and Eleusine indica
The objective of the research was to determine the efficacy of pre-emergence-applied herbicides sprayed at different rates and times before soybean planting under water deficit conditions, to control volunteer cotton plants tolerant to glyphosate and ammonium glufosinate and Eleusine indica. The trial was conducted on Formosa do Rio Preto/BA, during the 2015/16 growing season, in a randomized complete block design, with four replications and ten treatments, which included: glyphosate + diclosulam 960 + 25,2 g ha-1 a.i., glyphosate + diclosulam 960 + 35 g ha-1 a.i. sprayed 50, 20 and 0 days before soybean planting (DBP), glyphosate + flumioxazin 960 + 50 g ha-1 a.i., glyphosate + sulfentrazone 960 + 150 g ha-1 a.i., glyphosate + sulfentrazone 960 + 200 g ha-1 a.i. sprayed 0 DBP and an untreated treatment. Assessments of percentage visual control were performed 7 and 0 DBP and 14 and 45 days after soybean planting (DAP) and soybean grain yield was measured. Diclosulam at 25,2 and 35 g ha-1 a.i. controlled volunteer cotton plants when sprayed 50, 20 and 0 DBP. Sulfentrazone sprayed 0 DBP at 150 and 200 g ha-1 a.i. controlled volunteer cotton while flumioxazin did not provide adequate control. Diclosulam at 25,2 to 35 g ha-1 a.i. was the best treatment to control Eleusine indica when sprayed 0 DBP. Soybean yield was considered equal between treatments.
Experimental methods to evaluate herbicides behavior in soil
Pesticides are an essential tool for agriculture, however, studies have been shown that only 45% of the sprayed products reach the target-crop, whereas 30% is drifted, 10% is lost due to transport processes (leaching, volatilization and runoff), and 15% reaches the soil. Moreover, only 1% of the applied product reaches the target, in other words, the pathogens, weeds and insects. Even though, risk assessments for environmental contamination due to off-target movement of a pesticide are mandatory and performed prior to its registration, these products are often detected contaminating non-target sites, and freshwater ecosystems are the main impaired. Various biological, physical and chemical processes determine the environment fate and the efficacy of these compounds. Thus, there are several experimental techniques used to evaluate the behavior of herbicides in soil. This review aims to summarize the most commonly used methods to describe and evaluate each process to which a herbicide is subjected in soil and, their advantages and disadvantages. In general, when studying the fate of pesticides in the environment, laboratory experiments provide more precise information because it is possible to control the environmental conditions and isolate the factors that interest the researcher. However, it is important to mention that there is not a more efficient method but there are methods that can provide a better result in a given situation. Thus, the method choice depends in the study aim and the available infrastructure.
Mathematical modeling of the drought emergency flow: crop management decision tool
The appearance of weed biotypes resistant to herbicides and the increase in social pressure to reduce its use, created the need to develop tools to refine herbicides application and improve weed control. In this way, the development of weed emergence models has become crucial for the development of management strategies in agricultural areas. The objective of this review is to show the factors that influence the emergence flow and the main models used to predict weed emergence, the procedures of modeling and the practical impacts of their use for weed management. The emergence flow of weeds correlates directly with seed response patterns to the interference of environmental factors and cultural practices. The developed empirical and mechanistic emergence models allow predict weeds emergence in different years and geographic regions, based on climatic and ecophysiological conditions. However, mechanistic models are more complex and allow better comprehension of weed emergence, but empirical models provide the simplicity and the flexibility necessary for decision making. The knowledge of weed emergence flows allow the development of management strategies that provide a greater competitive ability to the crop and reduce productivity losses, as well as the selection of control measures that reduce the use of herbicides, environmental contamination and improve technologies used in agriculture.
Statistical approaches in weed research: choosing wisely
Statistical concepts and methods play an important role in the society, and statistical data analysis require considerable human labor and knowledge. From one side, computers and statistical softwares allow almost anyone to run free on statistical methods, but on the other side any researcher, professor, student or professional, even lacking on basic statistical knowledge to test their data, may use these softwares, often producing biased statistical analyses. The objective of this review is to demonstrate how the choice for statistical methods in weed science may create a bias in the interpretation of herbicide efficiency, and impact herbicide recommendations. We propose minor changes to the ordinary approach to help avoiding data misinterpretation and unintentional erroneous herbicide recommendations. The problems discussed throughout the review are illustrated with real field experimental data. Great part of the results of studies involving herbicide efficacy seems to be based on underpowered experiments and prone to output distorted information. Flawed choices of statistical methods, specially the p-value based statistics (ANOVA and post-hoc tests), can pave the way for mistaken conclusions even in properly conducted experiments in weed research. It is proposed the use of confidence intervals for both qualitative and quantitative data analysis, coupled to an appropriate number of samplings (“n”).
Residual effect of pre-emergent herbicides on the initial development and biochemical composition of snap bean seedlings
The use of herbicides must be made in a rational way, giving priority to reduce possible adverse effects on subsequent crops. The objective was to evaluate the residual effect of pre-emergent herbicides on growth and initial development as well as the biochemical composition of snap bean seedlings. The experimental design used was the completely randomized, with four replications in factorial scheme 3x4, three snap bean cultivars (Macarrão Favorito, Macarrão Preferido e Macarrão Trepador) and three pre-emergent herbicides, plus a control (without herbicide). Was use the residual doses of pre-emergent herbicides sulfentrazone in 0.3 g ha-1, diclosulam in the concentrations of 0.126 g ha-1 and imazethapyr in 0.05 g ha-1. The work was developed in a seeds analyze laboratory with the purpose of minimizing possible adverse effects of the environment. The seeds were sowing on germitest paper moistened with solutions containing the herbicides, with each respective treatment. The following characteristics were evaluated: germination (GER), germination speed index (GSI), seedling length (SL) and seedling dry mass (SDM) and soluble protein content (PROT) in addition to the enzymatic activity of catalase (CAT), peroxidase (PER) and phenylalanine ammonia-lyase (PAL). The phytometric variables SL, SDM, GER and GSI reduced in the presence of herbicides, and for the levels of PROT and enzymatic activity of CAT, PER and PAL there was observed a variation according to the genotype. The sulfentrazone showed up as the product of higher toxicity, as well as the Macarrão Trepador as the genotype with lower tolerance.
Herbicides cause impacts on survival and development of bees?
Pollination is a key ecosystem service in maintaining biodiversity, which is essential in the reproductive process of higher plants in almost all terrestrial production systems. In order to maintain the vast global biodiversity, including cultivated species, there is a need for diversity of pollinators. However, bees suffer from anthropic actions. These insects have been disappearing from agricultural areas due to the introduction of exotic species, large areas of monoculture, deforestation for agriculture and pasture and, mainly, the fragmentation of habitats and the excessive or incorrect use of pesticides. These pesticides can affect not only the longevity of the bees, but also their vitality which may, over time, influence the maintenance of the colonies. In the case of pesticide use, most studies aim to evaluate the effects of insecticides on bees, and studies on other product classes, such as herbicides, are scarce. This review sought to focus on the possible effects, especially, of herbicide use on bee survival and development. The use of herbicides that show toxicity to beneficial insects, such glyphosate, 2,4-D, MSMA and paraquat must be monitored continuously. The sublethal doses of herbicides, that is, lower dose than the one that causes the death, can trigger behaviors in individuals, causing in serious damages to the colonies maintenance.
Effect of method of weed control and insecticide (Lambda cyhalothrin) rates on the productivity of cowpea (Vigna unguiculata (L.) walp) in a southern Guinea savanna of Nigeria
Field trials were conducted in two locations, at the Teaching and Research (T&R) Farm of the College of Agriculture, Kwara State University and Ga-Alanu Village, Malete, in the 2015 cropping season. The objective this work was to evaluate the effect of herbicide application associated to the insecticide Lambda cyhalothrin on weed control, and yield of cowpea. The experiment consisted of 18 treatments arranged in a factorial scheme. The first factor was three insecticide rates (0 ml ha-1, 8.75ga.i.ha-1 and 17.5ga.i. ha-1). The second factor was the six methods of weed control (pendimethalin at 1.5kg a.i ha-1, pendimethalin at 2.0kg a.i ha-1, pendimethalin at 1.5 kg a.i. ha-1 plus one supplementary hoe weeding (SHW), metholachlor + diuron at 1.5 + 0.6 kg a.i ha-1, hoe weeding at 3 and 6 weeks after sowing (WAS) and a weedy check). The treatments were laid out in randomized complete block design arranged factorially with 3 repetitions . Variables measured were weed density, weed dry matter, relative importance value of weed species, plant height, crop vigour, number of pods/plot and grain yield. Data collected was subjected to analysis of variance and means were separated using Least Significant Difference (LSD) at 5% level of probability. Results showed that insecticide rates at 8.75ga.i.ha-1 and 17.5ga.i.ha-1, and pendimethalin at 2.0kg a.i.ha-1 or pendimethialin at 1.5kg a.iha-1 plus one SHW promoted good growth and higher yield of cowpea.
Herbicide association applied to control weeds in glyphosate-resistant soybean
In order to bypass cases of glyphosate-resistant weeds, it becomes necessary to use herbicides with other action mechanisms. The goal of this work was to evaluate the effectiveness and selectivity of herbicides with isolated or tank mix application for the management of soybean-infesting glyphosate-resistant weeds. Treatments were applied sequentially, during pre-emergence: clomazone (900 g ha-1 a.i.); flumioxazin (50 g ha-1 a.i.); diclosulam (35.02 g ha-1 a.i.); s-metolachlor (1152 g ha-1 a.i.); sulfometuron + chlorimuron-ethyl (18.75 + 18.75 g ha-1 a.i.); pendimethalin (1250 g ha-1 a.i.); sulfentrazone (250 g ha-1 a.i.); sulfentrazone + chlorimuron-ethyl (250 + 20 g ha-1 a.i.); imazethapyr + sulfentrazone (100+250 g ha-1 a.i.) and imazaquin (150 g ha-1 a.i.) and, during post-emergence, glyphosate was used over these treatments (1080 g ha-1 a.e.). During post-emergence, glyphosate was applied in an isolated manner (1080 g ha-1 a.e.) and, mixed in the sprayer tank with glyphosate (1080 g ha-1 a.e.), imazethapyr (100 g ha-1 a.i.), clethodim (96 g ha-1 a.i.) and chlorimuron-ethyl (20 g ha-1 a.i.), plus the infested and weeded control samples. The experimental area was infested with 75% of creeping signalgrass plants (Urochloa plantaginea) and 25% of summergrass (Digitaria ciliaris), at the average densities of 133 and 45 plants m-2, respectively. At 14 and 21 DAT, the application of glyphosate + [sulfometuron + chlorimuron-ethyl] caused a 67 and 62% phytotoxicity to soybean, respectively. In order to control summergrass and creeping signalgrass, this very mixture presented an 88% index at 21 DAT, whereas control for the other treatments exceeded 91% during all evaluated periods. All the evaluated treatments caused over 91% control of both weeds, except for glyphosate + [sulfometuron + chlorimuron-ethyl]. The associations of herbicides to glyphosate caused weed control and were selective to soybean, except for sulfometuron + chlorimuron-ethyl, which presented lower control and high phytotoxicity. Some herbicides damaged the yield components of soybean, but only the sulfometuron + chlorimuron-ethyl mixture caused a reduction in grain productivity.
Photosystem II inhibitors herbicides in pre-emergence control for crabgrass species
Many species of the genus Digitaria are known as crabgrass and occurs in the main agricultural crops, especially in sugarcane production, which uses mostly photosystem II inhibitor herbicides for weed management. Due to the complexity of the cultivation system and the problems attributed to the substitution of susceptible species weeds by tolerant species of crabgrass populations, the objective of this work was to verify the control of crabgrass species using photosystem II inhibitor herbicides (PSII) in pre-emergence. The experiment was conducted in greenhouse in a completely randomized in factorial scheme 3x7, with four replications, with the first factor composed of three crabgrass species (D. ciliaris, D. horizontalis and D. nuda) and the second factor composed of following herbicides (ametryn; hexazinone; amicarbazone; diuron + hexazinone; diuron and tebuthiuron), further of the treatment without application. . The efficacy of the treatments was verified through of control by visual evaluation at 15 and 30 days after application (DAA), PSII electron transport rate analysis and total dry biomass of aerial part of the plants. For D. nuda it was observed low control with the herbicides diuron and tebuthiuron. The herbicides ametryn, hexazinone, amicarbazone and diuron + hexazinone mixture were effective in the control with levels higher than 95%, being good alternatives in the crabgrass control.
Interference between weeds and crop: changes in secondary metabolism
Secondary metabolites ensure the survival of plants in adverse situations. Plants change their biochemical constitution from the primary metabolism in response to changes in the environment. The production of secondary metabolites mitigates the effects of stress, allowing the plant development in non-ideal situations. Allelochemical compounds are examples of secondary metabolites produced by plants in situations of interspecific interference. When in competition stress, plants have the ability to release compounds into the environment in order to signal the presence or inhibit the growth of neighboring plants. Secondary metabolism responses of crops resulting from competition with weeds alter the chemical composition of the species, resulting in changes in development and yield. The application of herbicides is also an alteration source in the secondary metabolism by the interruption of routes, either by the accumulation of constituent acids or the formation of unwanted compounds. The current review aims to show the art state of interference relationships between weeds and crops on changes in secondary metabolism.
Weed management in pre-sprouted seedlings system of sugarcane
The use of pre-sprouted seedlings (MPB) of sugarcane is a technology that provides sanity, vigor and uniformity of planting with a focus on quality and yield, for the formation of nurseries and replanting of commercial areas, as well as in areas of MEIOSI. However, the presence of weeds can affect the yield by competing for water, light, nutrients and space with sugarcane seedlings. The integration of the cultural, mechanical and chemical methods provides control of the weeds, so that they do not affect the yield and longevity of the sugarcane field. The mechanical control through the break-back operation associated with chemical control is one of the tools used. As well as the chemical control that through the residual herbicides guarantees a greater control of weeds during the establishment of the crop in the field. However, sugarcane seedlings have roots that are in contact with the herbicide in the treated soil layer, affecting the selectivity. Thus, weed management in the MPB planting system provides a field of new studies and discussions.
Behavior of 2,4-D + picloram Latosol Red-Yellow
2,4-D and picloram are molecules much used in the control of weeds in pastures. Study the fate of these molecules in Amazonian soil is of extreme importance in assessing the potential for contamination of groundwater. The objective of the present work was to determine the leaching of increasing doses of 2,4-D + picloram herbicide in Dystrophic Yellow Red Latosol. For this, samples of this soil were used as substrate to fill PVC pipes with 10 cm in diameter and 50 cm in length. The treatments consisted of a combination of five doses 0.125; 0.25; 0.5 and 1.0% of one liter of the Tordon commercial product plus one control without application and six sampling depths in the columns (0; 8; 16; 24; 32 and 40 cm).The cucumber was used as bioindicator species where the following variables were analyzed: phytotoxification, plant height, root length and leaf area. The experiment was carried out in a completely randomized design with four replications. It was verified that leaching of the herbicide 2,4-D + picloram in Dystrophic Red-Yellow Latosol and that this one was more intense with the increase of the doses of the herbicides, arriving to be leached throughout the studied column.
Sayonara Andrade do Couto Moreno Arantes
Molecular biology applied to weed science
The weeds have high genetic variability, mainly for this, they are adapted to environments disturbed by humans. Although weed control has evolved positively in recent years, they continue to interfere with agricultural production. The objective of this bibliographic review is to present the contribution of molecular biology in the studies applied to herbology. There area gap in what we learn about weed genomics, which could help us manage and improve the competitiveness of weed crops. Many studies in the field of weed science can be carried out using molecular biology techniques. The characterization of the genome of weed species, aiming to identify species with higher accuracy, identification of herbicide resistant species and its mechanism of resistance, genetic variability and similarity among weed populations, identification of genes involved in the interaction processes between plants, among other.
Methods of weed control in organic systems: a short review
Weed management in organic systems of agricultural production is a major challenge to agricultural farmers. To solve this challenge, it is necessary to explore sustainable management practices and the development of new technologies. It should be emphasized that there are technological or biological alternatives that can be used in weed management in organic systems, and are used in large areas. Cultural, biological, mechanical and physical management strategies can be effective in controlling weeds, as well as reducing the use of chemical control in conventional agriculture. Thus, this literature review aimed to present some alternative methods of weed control and potential use in organic areas of agricultural production. Weed control methods in organic areas should always use integrated and sustainable strategies.
Phytometric performance of corn on the effect of doses of trinexapac-ethyl and clomazone
The productive increase of the maize crop can be maximized by crop densification and, for this, the use of herbicides and growth regulators, because it favors the reduction of plant size, becomes an important tool. Thus, the objective of this study was to evaluate the rates of growth reducers on the phytometric performance of maize simple hybrids. The design was completely randomized, in a 2 x 5 factorial scheme, with four replications. Growth factors (trinexapac-ethyl and clomazone) were considered as the first factor and in the second, the five doses of each reducer (0, 50, 100, 200 and 400 g i.a. ha-1) were considered. The trinexapac-ethyl and clomazone growth modifiers modify the phytometric performance of maize plants. About 113 g i.a. ha-1 of clomazone provides an increase in stem diameter and fresh mass. The herbicide clomazone can also be used as a growth-reducing agent.
Paspalum notatum growth and pigment content in response to the application of herbicides
Bahiagrass (Paspalum notatum) is a poacea resistant to trampling, water restriction and low soil fertility; however, it requires frequent cutting to eliminate the biomass excess it produces. To inhibit the growth of turfs and to avoid or delay cutting, growth regulators and herbicides have been tested. The goal of this work was to evaluate the potential of three herbicides as growth regulators on bahiagrass, and their influence on growth and chloroplast pigment content. The experimental design was in randomized blocks, in split-plot scheme, with three herbicides (glyphosate, isoxaflutole and tembotrione) and five doses (0, 68, 136, 272, 544 g a.e. ha-1; 0, 24, 48, 96, 192 g a.i. ha-1 and 0, 13, 26, 52, 104 g a.i. ha-1), respectively, with four replications. The following characteristics were evaluated: phytointoxication, dry mass, grass height and chloroplast pigment content. Data were submitted to analysis of variance and, when significance was observed, the regression test was performed, up to the second degree, separately for each herbicide. Herbicides demonstrated effectiveness in controlling turf size; however, the phytotoxic effect was observed with the increase of the doses and a damage in the aesthetic aspect of the grass. Isoxaflutole has greater potential to be used as a growth reducer on bahiagrass, due to the low necessary dose to reduce height and to low phytointoxication. The content of chloroplast pigments is changed singularly for each used herbicide, and it has a direct relation with the dry mass of leaves.
Ethylene synthesis and photosynthetic responses in bean and maize plants exposed to auxins
Auxins IAA (indole-3-acetic acid), 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) were applied on maize (Zea mays, monocot) and bean (Phaseolus vulgaris, dicot) plants, with the goal to understand the mechanisms that lead to different responses in relation to the metabolism of ethylene. Maize plants treated with auxins did not produce ethylene, whereas beans produced a lot of it after the treatment. After being sprayed with auxins, maize did not produced any 1-Aminocyclopropane-1-carboxylic acid (ACC), which was observed on beans. The maximum quantum yield of the photosystem II (Fv/Fm ratio) and the levels of photosynthetic pigments were not altered in maize plants treated with auxins. Bean plants showed significant decreases in both variables after the treatment with 2,4-D and 2,4,5-T, but not with IAA. The reduction of chlorophyll levels in bean plants treated with 2,4-D and 2,4,5-T was related to the observed chlorosis, since there was a more accentuated degradation of chlorophylls than carotenoids. Xantophylls also had a more accentuated degradation than alpha and beta carotene in bean plants treated with 2,4-D and 2,4,5-T. When aminoethoxyvinylglycine (AVG) and Co2+ were provided to bean plants together with auxins, there was no fall in the Fv/Fm ratio and in the pigment levels, except for the alpha carotene.
Selectivity of herbicides applied in pre and post emergence of safflower culture
The cultivation of safflower has increased in recent years, mainly for the production of biodiesel. However, it is necessary to weed control in order to avoid losses in productivity. In this way, an alternative that comes up is the use of selective herbicides for culture. This study aimed to verify the selectivity of different herbicides in pre and post-emergence to the safflower crop. Two experiments were conducted adopting a randomized block design with four replicates. For the first experiment with pre-emergence applications the treatments were arranged in a 6 x 2 + 1 factorial scheme, whereas for the second experiment with the post-emergence applications the treatments were arranged in a factorial scheme 7 x 2 + 1. For both experiments, the factor A corresponded to the different herbicides and factor B at the doses used and the additional treatment consisted of control without application of herbicides. Visual evaluations of intoxication were carried out in the plants at 7, 14 and 21 days after application (DAA), plant height, stand and productivity. The application of chlorimuron-ethyl (20 e 40 g i.a. ha-1), flumioxazin (50 e 100 g i.a. ha-1), imazaquin (161 e 322 g i.a. ha-1), s-metolachlor (1440 e 24000 g i.a. ha-1) and sulfentrazone (300 g i.a. ha-1) in pre-emergence, and sethoxydim (184 g i.a. ha-1), fluazifop-p-butyl (375 e 750 g i.a. ha-1) haloxyfop-methyl (60 e 120 g i.a. ha-1) e clethodim (108 g i.a. ha-1) in post-emergence were selective for safflower.
Initial selectivity of herbicides applied in post-emergence of showy crotalaria
Among the practices that aim to confer sustainability of the agricultural soil, the use of green manure and/or cover crops such as crotalaria are advocated. The management of weeds is one of the practices for the success of crotalaria. However, the information about the selectivity of herbicide are scarce and these are of paramount importance. The objective of this study was to evaluate the selectivity of different herbicides applied in post-emergence of showy crotalaria (Crotalaria spectabilis). Two experiments were conducted in a greenhouse in a randomized completely randomized design with four replications. In the first one the following herbicides were tested. The first experiment involved the following herbicides (g. i.a.ha-1): atrazine (500 and 1000), bentazon (720), carfentrazone-ethyl (3.75), clomazone (400), diclosulam (20), diuron (800), ethoxysulfuron (18), flumioxazin (10), mesotrione (60), oxadiazon (500), tembotrione (40), atrazine + flumioxazin + carfentrazone-ethyl (300 + 5 + 2), and a control without application. In the second were used, bentazon (400), clomazone (400), diclosulam (10 and 15), diuron (400), ethoxysulfuron (15), bentazon + diclosulam (200 + 7.5), diclosulam + diuron (7.5 + 200), bentazon + diuron (200 + 200) and a control without application. Phytotoxicity was evaluated at 7, 14, 21 and 28 days after application (DAA) and aerial dry matter (ADM) at 28 DAA. In both experiments the herbicides bentazon, clomazone, diclosulam and ethoxysulfuron caused low injuries to the crop and low reduction in ADM. The herbicides atrazine, mesotrione, oxadiazon and atrazine + flumioxazin + carfentrazone-ethyl provided high levels of injuries and high reduction in ADM. The herbicides bentazon, clomazone, diclosulam and ethoxysulfuron were selectivity for post-emergence application of the crop.
The chemical control of weeds is an important management to keep high productivity in the wheat crop. Due to the scarceness of registered products for the crop, the goal of this work was to evaluate the selectivity of the flumioxazin herbicide to wheat, applied in post-emergence. The experiment was conducted on the field and the used experimental design was the randomized block one, with four replications. The treatments were applied on stage V3 of the wheat crop and consisted in six flumioxazin doses: 0, 10, 20, 30, 40, 50 g ha-1. Evaluations were performed on SPAD index, intoxication and weed control on day 15, 21, 28 and 35 after application. At the end of the experiment, 109 days after seeding, plants were tracked to determine the one thousand grain weight, hectoliter weight and grain productivity. The obtained results showed that in spite of causing an up to 20% SPAD index and up to 34% intoxication reduction in the highest applied dose, flumioxazin provided selectivity to the wheat crop, since it did not interfere in the other evaluated variables, mainly in grain productivity.
Spray volumes, adjuvant and rainless intervals in weed control with sulfentrazone
The herbicide sulfentrazone, used in sugarcane cultivation, is recommended for the control of eudicots and monocotyledons in pre-emergence and is also indicated for the control of Panicum maximum and Ipomea hederifolia. The research was carried out with the objective of verify the influence of the sulfrentazone herbicide with and without adjuvant on soil without straw cover under different periods without rainfall, associated to different application volumes, for the control of P. maximum and I. Hederifolia. The experimental design was a completely randomized, with four replications, in the 2x2x6+1 factorial arrangement, that is, two treatments of herbicide, two volumes of spray liquid (60 and 120 L ha-1), six periods without rain before application another witness, who received no application. Weed counts were evaluated at 15 and 33 days after rainfall. The dry matter of the aerial part of the plants was also evaluated. The results indicated that the application of sulfentrazone with all treatments was effective in the control I. hedrifolia, independent of the volume of syrup, period without rainfall or presence of adjuvant. Even if P. maximum plants escape (emergence of plants) in all periods without rainfall, the treatments are effective for the control of the species. The presence of the mineral oil in the syrup with the herbicide sulfentrazone does not increase the control of P. maximum and I. hederifolia.
Technical effectiveness and economic return of the glyphosate-resistant hairy fleabane management in soybean pre-emergence
The commercial release of the Roundup Ready® soybean helped the management of weeds and allowed the application of glyphosate during the post-emergence of the culture. However, the intensive use of this herbicide selected resistant hairy fleabane biotypes and hindered control. Many works evaluate the technical effectiveness of herbicides, however, most of the times; the economic return is not analyzed when making decisions about the choice of which herbicide to apply. The aim of this work was to evaluate the technical effectiveness and the economic return of applying herbicide associations and rates in the management of glyphosate-resistant hairy fleabane, in soybean pre-emergence. The experiment was carried out in randomized block design with four replicates. Treatments consisted in associations among glyphosate, 2.4-D, saflufenacil, diclosulam, chlorimuron-ethyl and flumioxazin. The analyzed variables were hairy fleabane control and phytotoxicity on soybean on 7, 14, 21 and 35 days after the application and yield of soybean. The economic return of treatments was calculated according to the cost of the herbicides and the soybean yield. Results about control and yield shows that the association of glyphosate, chlorimuron-ethyl, flumioxazin and 2.4-D and of glyphosate, chlorimuron-ethyl, 2.4-D and saflufenacil presented the best technical effectiveness response and the use of glyphosate, chlorimuron-ethyl and 2.4-D presented the best economic return. However, the increase in chlorimuron-ethyl rates and its association with flumioxazin did not improve the control of hairy fleabane.
Selectivity of herbicide isolated and in associations for RR2/LLTM maize
Maize with tolerance to the herbicide glyphosate (Roundup ReadyTM) (RR2TM maize) has been increasingly used, since it favors the use of this herbicide to control weeds. Thus the objective of this study was to evaluate the tolerance of the hybrid 2B810PW (RR2/LL), submitted to the application of isolated and associated of glyphosate, glufosinate and atrazine at post-emergency (V4). The assay was carried out in the field, in the harvest 2013/14, and the design adopted was a randomized block with four replications. The treatments consisted of the application of glyphosate (1080 g ha-¹ of acid equivalent - a.e.), glufosinate (500 g ha-¹ of active ingredient - a.i.), atrazine (2000 g ha-¹ a.i.), glyphosate + glufosinate, glyphosate + atrazine, glufosinate + atrazine, glyphosate + glufosinate + atrazine, plus the control without application. Crop injury was evaluated at 7, 14, 21 and 28 days after application (DAA) and SPAD index, at 21 and 28 DAA. Were also evaluated variables related to agronomic performance: height, ear height, stem diameter, thousand grain weight and yield. In general, the variables were not affected by treatments. The maize hybrid 2B810 PW presented is tolerant to the application post-emergence (V4) of the herbicides used.
Spray deposition and control effectiveness of glyphosate and saflufenacil associated with adjuvants
The extensive use of glyphosate has selected weeds of difficult control and one of the alternatives to overcome this problem is the association of different herbicides and adjuvants with glyphosate. The objective of the experiment was evaluate the effects on deposition and effectiveness of saflufenacil and glyphosate isolated or in mixture with addition of adjuvants applied in post-emergence of dayflower and morning glory plants. The experiments were conducted in a greenhouse. On the first experiment was adopted the factorial 3x5 for each species, in which factor A corresponded to the combination between the herbicides glyphosate, saflufenacil and glyphosate + saflufenacil, and the factor B the addition of the adjuvants Natur’al óleo®, Assist®, Aterbane‑ and Silwet L–77®. On the second experiment the adjuvant Dash® was added, therefore factorial 3x6. The herbicides showed similar deposition even with the addition of adjuvants. The isolate use of glyphsate even in mixture with adjuvants did not resulted in satisfactory control of dayflowers plants. The spray deposition did not influenced the control of dayflower and morning glory weeds. However, the application of saflufenacil isolated or in mixture with glyphosate provided better control for both weed studied.
Effectiveness and selectivity of herbicides in cowpea cultivars
Despite the extensive cultivated area in Brazil and the growing demand for information about weed control, few studies are found in literature reporting the efficacy and selectivity of herbicides for cowpea (Vigna unguiculata). View of this, this work was developed in order to evaluate the selectivity and efficacy of herbicides for cultivars of cowpea. The experiment was conducted in a randomized block design in factorial scheme 2 x 13, with two cowpea cultivars (BRS Xiquexique and BRS Guariba) and 13 strategies for weed management (1: S-metolachlor, 2: metribuzin + fluazifop, 3: imazamox + fluazifop, 4: bentazon + fluazifop, 5: imazamox + bentazon + fluazifop, 6: imazetapyr + fluazifop, 7: fomesafen + fluazifop, 8: lactofen + fluazifop, 9: chlorimuron + fluazifop, 10: chlorimuron + lactofen + fluazifop, 11: fluazifop + capina, 12: weeded control and 13: control without weeding). It was verified that there is no difference in the selectivity of the evaluated herbicides for the cultivars BRS Guariba and BRS Xiquexique. The herbicides 1; 3; 4; 5 and 6 are selective for the cultivation of cowpea; The mixtures of herbicides 7 and 8 caused severe intoxication, prolonging the cycle and reduce the productivity of cowpea; Herbicides 2; 9; 10 are not selective for the cowpea; The mixtures of herbicides 5 and 6 were effective in the control of weed species present in the area with yield equivalent to the hand weeded; The effectiveness of herbicides or mixtures of herbicides for weed control depends on the weed community.
Alternatives for the chemical control of voluntary plants of showy crotalaria in different application modalities
With the insertion of showy crotalaria as an antagonistic plant in areas with nematodes infestation history, the occurrence of volunteer plants from this species became common, making it necessary to adopt measures for their management. Thus, this work had the goal to evaluate the effectiveness of herbicides used on different species that where grown in rotation with showy crotalaria (C. spectabilis), aiming at its use in controlling volunteer plants from this species. Two experiments (herbicides applied in pre and post-emergence) were conducted on the field using the randomized block design, in (8x2)+1 factor scheme, with four replications. The variable evaluated in the experiments was the control percentage in different periods after treatment application; a plant stand was performed in the experiment with herbicides applied in pre-emergence. Atrazine and diuron, applied in pre-emergence, were the best treatments to control showy crotalaria volunteer plants; they did not suffer any influence from the applied dose. In addition to these, flumioxazin and fomesafen (60 and 375 g ha-1, respectively) were also good alternatives to control showy crotalaria in this application modality. For pre-emergent herbicides, with the exception of diuron (1500 g ha-1), all the other treatments were effective in controlling showy crotalaria in applications performed on plants with 2 to 4 leaves. As for the second application stage, 6 to 8 leaves, in addition to diuron (both doses), fomesafen applied in a lower dose (187.5 g ha-1), was not effective in controlling showy crotalaria, either.
Initial growth of cowpea-beans after application of post-emergence herbicides
The objective of this work was to evaluate the tolerance of cowpea, BSR Aracê, to different herbicides applied in the post-emergence period, in the initial phase of plant growth. The experiment was conducted in a greenhouse, in a completely randomized design, with four replications. The treatments evaluated were: haloxyfop (60 g ha-1), lactofen (180 g ha-1), chlorimuron-ethyl (17,5 g ha-1), bentazon (576 g ha-1), bentazon + imazamox (600 + 28 g ha-1), imazethapyr (100 g ha-1), fomesafen (250 g ha-1), quizalofop-P-ethyl (62,5 g ha-1), lactofen + quizalofop-P-ethyl (180 + 62,5 g ha-1), fomesafen + quizalofop-P-ethyl (250 + 62,5 g ha-1) and a control. Were realized visual evaluations of intoxication, plant height, dry leaf mass, stem, root, total dry mass and leaf area. The herbicides haloxyfop and quizalofop-P-ethyl they caused minor damage to the development of cowpea plants. The chlorimuron-ethyl caused severe damage to the crop, interrupting their growth. The lactofen + quizalofop-P-ethyl and fomesafen + quizalofop-P-ethyl mixtures caused high damage to the culture, with lactofen + quizalofop-P-ethyl causing the plants to die at 21 DAAH. It was concluded that cowpea, cv. BRS Aracê, have tolerance to haloxyfop and quizalofop-P-ethyl herbicides, and moderate tolerance to imazethapyr and bentazon + imazamox. The lactofen + quizalofop-P-ethyl and fomesafen + quizalofop-P-ethyl mixtures showed a synergistic effect on bean cowpea. The lactofen + quizalofop-P-ethyl mixture and the chlorimuron-ethyl herbicide cause irreversible damage to the bean cowpea crop.
Control efficiency of black bindweed by glyphosate and glyphosate + 2,4-D on different application times
Herbicides applications are usually held with specific environmental conditions that may influence the efficacy of these products. This research was conducted to evaluate the influence of application times of glyphosate and glyphosate + 2.4-D herbicides in Polygonum convolvulus weed control. The experiment was developed with vases arranged in field conditions. The treatments were constituted by glyphosate (960 g ha-1) and glyphosate + 2.4-D (960 + 335 g ha-1) herbicides, both applied in 25 and 9/26/2015, in 10:00 PM hour, 03:00 AM hour, 7:00 AM hour; mid day hour and 5:00 PM hour and a check without application, for controlling P. convolvulus weed. Experimental units were constituted by plastic vases with four plants in three to five leaves stage, kept in natural conditions of application until 28 DAA (days after application). Applications were conducted with a costal spray with four spray nozzles AVI 110.02, 210 kPa pressure, displacement speed of 3.6 km h-1 and an application applying rate of 200 L ha-1. Results indicated that glyphosate and glyphosate + 2.4-D controlled efficiently the weed from 14 DAA, regardless of application hour. However, significant reductions were observed in control efficiency and dry matter production of weed at noon, as well as lower spray deposition of glyphosate + 2.4-D, at all times.
Does pre-emergence herbicides control individual plants and clumps of volunteer corn RR® F2 in soybean?
The grown of RR® soybean preceded by corn RR® increased the occurrence of volunteer corn plants interfering with soybeans. The volunteers originate from the grain lost during harvest corn. Losses occur as individual grains, which give rise to individual plants, and in the form of ear corn or pieces containing various grains, which give rise to the clumps. The volunteer corn if not controlled interfere with soybean and reduces significantly the yield, even in a population less than a plant m-2. Pre-emergency herbicides used for weed control in soybean have control effect on volunteer corn RR® F2, however, few studies have demonstrated its efficiency. The objective was to evaluate the control of clumps and individual plants of volunteer corn RR® F2, provided by spraying herbicides chlorimuron (25 g ha-1), diclosulam (25.2 g ha-1), chlorimuron + sulfometuron (18.7 + 18.7 g ha-1), imazapic + imazapyr (78.7 + 26.2 g ha-1), clomazone (360 g ha-1) and pyroxasulfone (119 g ha-1) applied in soybean pre-emergence. Two experiments were carried on field in the design of a randomized block with four replications. The herbicide imazapic + imazapyr was efficient to control clumps while diclosulam, chlorimuron + sulfometuron and imazapic + imazapyr controlled individual plants showing superior control to 80%. Although the results show control of corn, the yield of soybeans decreased in all treatments when compared to control without corn, suggesting that is necessary additional herbicidal post-emergence applications, especially in high infestation of corn.
Technological parameters of sugarcane submitted to chemical ripening agents in the early harvest
The use of chemical ripeners is a reality in the sugarcane sector. The objective of this work was to evaluate the technological and productive parameters of sugarcane when submitted to the application of chemical ripeners in the beginning of the harvest. The experimental design used was in randomized blocks arranged in split plots with four repetitions. The main plots consisted of the application of the following products with their respective dosages: control - without application; sulfometuron-methyl 0.02 kg ha-1 + glyphosate 0.15 L ha-1; ethephon 0.34 L ha-1 + glyphosate 0.15 L ha-1; glyphosate 0.35 L ha-1; compounds of organic carboxylic radicals – CC 1.0 L ha-1 + glyphosate 0.15 L ha-1. The subplots were composed of many different evaluation times: 0; 15 and 30 days after the application of products. The samples were collected manually and sent to the laboratory to determination of the brix, pol; reducing sugars; total reducing sugars; fiber; purity; humidity; theoretical recoverable sugar. Moreover, the productive parameters were determined: tons of culms per hectare and tons of sugar per hectare. Lastly, it was made the analysis of contents of shikimic acid and salicylic acid. The application of the mixture of chemical ripening compounds of organic carboxylic radicals + glyphosate showed an increase for the technological parameters of sugarcane15 days after application (DAA), followed by the treatment with application of glyphosate at 30 DAA.
Influence of organic matter on the phytoremediation of sulfentrazone in contaminated soil
Organic matter exerts an influence on the chemical, physical, and biological properties of soil. It can also influence the rates of herbicide degradation and sorption into it. This study aimed at evaluating the effect of adding organic compounds to soil over the remediation ability of the plant species Canavalia ensiformis (L.) (jack bean) in sulfentrazone-contaminated soil. The study was conducted in two phases. In the first phase, treatments consisted in a combination of four concentrations of organic compounds and in the application or not of sulfentrazone herbicide. After soil preparation, the herbicide was applied on the surface. Subsequently, seeds of the remediating plant species C. ensiformis were sown. At 75 days after emergence (DAE), samples of the aerial portions and roots of plants and soil were collected. All the collected material was frozen at approximately -20°C and then the accumulation of the herbicide on plants and soil was determined by chromatography. In the second phase, Pennisetum glaucum (L.) (pearl millet) was sown. This species is used as an indicator of sulfentrazone residue in the soil; biometric assessments were performed at 30 and 60 DAE. No sulfentrazone residue was found in the aerial portions or roots of the evaluated remediating plant species; however, it was detected in the soil. The increase in organic compound levels contributed to the growth and accumulation of biomass in pearl millet, when grown after the remediating plant species C. ensiformis, although it did not help phytoremediation.
Murdannia nudiflora control in soybean postharvest
The species of Murdannia nudiflora belongs to the family Commelinaceae is known as doveweed. Because of competitive capacity and tolerance to glyphosate this species growing during the soybean crop cycle, presenting rapid growth when the leaf senescence of soybean occurs difficulting weed management in others cultures. The objective of this study was to evaluate the efficiency of different active ingredients of herbicides in combination or separately, and verify the best dosage of the active ingredient, which provided the best control of M. nudiflora. Two field experiments were arranged in randomized block design. The first experiment consisted of eight herbicide treatments being glyphosate 972 g a.e. ha-1, atrazine 1500 a.i. g ha-1, carfentrazone 12 g a.i. ha-1, imazethapyr 100 g a.i. ha-1, glyphosate + imazethapyr 972 + 30 g ha-1, imazethapyr + atrazine 30 + 1500 g ha-1, carfentrazone + atrazine 8 + 1500 g ha-1 and check. The second experiment used the herbicide atrazine in different dosages 0, 880, 1100, 1320 e 1540 g a.i. ha-1. In the experiments all herbicide was applied in post emergence. In the results of the first experiment, only treatments with atrazine presented efficient control (> 80%). Glyphosate at the dose of 972 g a.e. ha-1 showed low control (< 20%) even when mixed with imazethapyr. In the second experiment, doses starting 880 g a.i. ha-1 of atrazine were sufficient for control in post-emergence of M. nudiflora.
Control of three Euphorbia species through herbicides applied during pre-emergence on sugarcane straw
The permanence of straw on the ground changes the phytosociology of weeds and affects control by the difficulty of transposing from straw to soil; thus, it is extremely important to transport it as quickly as possible. This research had the goal to know the effectiveness of two herbicides, applied on straw in different periods without rain, in controlling three weed species from the Euphorbia genus. The experiments were conducted in a greenhouse using a completely randomized design, arranged in split-plot in time (rainless periods: 0, 15, 30 and 45 days), with three replications. Seeds were distributed over the soil and covered by a 10 t ha-1 straw layer. The application of diuron + hexazinone + sulfometuron-methyl and tebuthiuron herbicides was performed during pre-emergence on the straw. Then, respecting the rainless period, planters received an irrigation of 20 mm water. On day 43, the visual control and dry mass of the aerial parts were evaluated. Data were submitted to analysis of variance and adjusted to the linear or quadratic equation model. E. hirta was 100% controlled by the two herbicides in all periods without rain. Tebuthiuron was not effective in controlling E. heterophylla and E. hyssopifolia after 45 days without rain. Diuron + hexazinone + sulfometuron-methyl herbicide is effective in controllling the three Euphorbia species, even whenapplied on the straw and after the 45-day period to be leached. Diuron + hexazinone + sulfometuron applied over sugarcane straw was effective in controlling all Euphorbia species studied.
Pre-emergent herbicides to the management of volunteer RR® corn in soybean crop
Alternatives for volunteer corn RR® management need further knowledge in the product scope with residual effect, mainly for use in pre-emergence of the soybean RR®. This paper evaluated the performance of residual herbicides to control this species, when applied in soybean using the method "plant-apply". The experiment was carried in the municipality of Santa Maria/RS, crop season 2015/16; evaluating herbicides applied in pre-emergence of soybean crop and corn RR®. The experimental design was randomized blocks with eight treatments and four replications were evaluated inhibition of emergence of corn plants and injury on emerged plants. Sequential application responses were also addressed. Herbicides tested: flumioxazin, chlorimuron-ethyl, imazaquin, and sulfentrazone; as associations these herbicides with flumioxazin, in sequential applications, reporting if there were synergistic effects. The best control of RR® volunteer corn was obtained with the imazaquin herbicide, which reduced the emergence of RR® corn plants by 90% and injured 97.5% of those that emerged. However, imazaquin caused symptoms of phytotoxicity in the soybean crop, which did not measure yield losses in this work. The association in sequential applications of imazaquin and flumioxazin, showed additive control effect on maize.
Glyphosate effectiveness in the burndown of signalgrass at two levels of biomass
The objective of this research was to evaluate the efficacy of glyphosate in desiccating Urochloa ruziziensis, U. decumbens, and U. brizantha cv. Piatã at two levels of biomass for no-till establishment in Cerrado areas. The experimental design was a randomized complete block design with four replications, in a split-plot system. Plots consisted of two levels of biomass and sub-plots consisted of four doses of Roundup Ultra® - glyphosate at 0.65; 1.30, 1.95 and 2.60 kg ha-1 acid equivalent. The application was performed using custom pressurized CO2 sprayer at the constant pressure of 210 kPa bar equipped with eight nozzles with TT110015, spaced at 0.5 m, and spray solution volume equivalent to 100 liters h-1. The assessments were based on the percentage of control of plant mass, performed on day 10, 15 and 20 after application. It is possible to conclude that U. ruziziensis is more sensitive to glyphosate than the other studied species and biomass levels influence doses to be given only for U. decumbens and U. brizantha cv. Piatã.
Patrícia Aparecida de Carvalho Felisberto
Yellow bells (Tecoma stans) control in pasture with localized applications of herbicides
The presence of yellow bells (Tecoma stans) in pastures can compromise the implantation and the development of forage, damaging animal production and hindering mechanized operations with trailing implements. The objective of this paper was to evaluate the yellow bells control after localized herbicides applications and the fitointoxication of pasture composed of Urochloa maxima (syn Panicum maximum). The treatments were triclopyr (4%) and triclopyr (3%) applied to the stump base (SB); picloram (2%) applied on stump after plants (SA); triclopyr + picloram (1% + 1%) and triclopyr + picloram (2% + 2%) SB; plus a check without herbicide application and a check where plants were mowed. All herbicides treatments resulted over 95% control 270 days after application and were more efficient than stump cut treatment, which showed capacity of regrowth. The herbicides promoted injures on pasture, however the symptoms were observed only in the area located around the T. stans plants.
glyphosate application in burndown of biomass sorghum
The sorghum biomass is an alternative to a renewable energy generation by burning it in boilers, it stands out for its high productivity that occurs fully mechanized way. A common alternative to reduce the crop moisture is the application of herbicides. However, there is no researches showing the moisture reduction with burndown applications. Thus, this work aimed to evaluate the glyphosate application in drying of sorghum biomass. The experimental design was completely randomized in a factorial 2x5x4 consisting of: two cultivars of sorghum biomass (BRS 716 and CR 1342); five glyphosate doses (0, 720, 1,440, 2,160 and 2,880 g of the active ingredient ha-1) and four samplings of plants (7, 14, 21 and 28 days after application), with four repetitions. During the different samplings of plants were carried out evaluations of fresh and dry stem and dry matter percentage of culms. The application of glyphosate doses were not effective in the burndown process of biomass sorghum cultivars BRS 716 and CR1342.
Evandro Henrique Figueiredo Moura da Silva
Copyright (c) 2016 Brazilian Herbicide Journal
Diclosulam effects on soybean grown in soils of different textural classes
The use of herbicides in pre-emergence of the soybean crop is a great tool for weed management. However, it is important to know the effects of herbicides in order to avoid a decrease in productivity. The objective of this study was to evaluate the sensitivity of three soybean cultivars submitted to pre-emergence application of diclosulam in clayey soils and average. The experiments were conducted in a greenhouse in randomized complete block design with four replications in a 6x2 factorial, where factor A corresponded to the treatments and the B factor was the soil textures. The treatments were different herbicide spraying times diclosulam, all pre emergency, being: without application, 28, 21, 14, 7 and 0 days before sowing (DAS) soybeans. The cultivars M IPRO 6410 NS 6906 NS 7000 and IPRO IPRO. Sowing took place at the end of the spray treatments at day 0 DAS. We evaluated the emergence speed index (EVI), percentage of phytotoxicity, plant height, dry weight of shoot and dry root weight. According to the methodologies used in this experiment, the herbicide diclosulam applied in pre emergence in clayey soils and average is safe for soybean cultivars analyzed, it did not cause negative effects on plant development.
Glyphosate sub lethal rates do not reduce corn yield
In herbicides spraying, used as ripeners, should be considered the presence of crops growing in adjacent areas, due to the risk of drift of these products. In this context, assuming the sensitivity of corn to this ripener, the aim of this research was to evaluate the effect of glyphosate sublethal rates in corn when applied to V4 and V8 stages of development. The experiment was conducted in Jataí, GO, consisted of 10 treatments established in randomized blocks design where the treatments were arranged in factorial 2 x 5, with four replications. First factor corresponded to spraying at the V4 and V8 stages of development of the corn and the second factor to sublethal rates (0; 3; 6; 9 and 12% of 216.0 g ha-1 a.e.) of glyphosate. Each plot contained 10 rows of hybrid SYN 7G17 with 9 meters length. Visual phytotoxicity effects on plants were not noticeable in both stages of application at 7, 14, 21, 28 and 42 days after application. Growth and production components were not affected by sublethal rates up to 12% (25.92 g ha-1 a.e.) of glyphosate.
Initial growth of sugarcane seedlings submitted to herbicides application
The chemical weed control is the most used in sugarcane culture, and studies covering the effects of these herbicides on the development of pre-sprouted seedlings of sugarcane. The objective of this work was to evaluate the effect of the herbicides ametryn, clomazone, hexazinone + diuron, metribuzin, sulfentrazone and tebuthiuron isolated and in association with saflufenacil in the initial growth of pre-sprouted seedlings of sugarcane varieties at different times of application. The experiment was conducted in a greenhouse in a completely randomized design, in a 14 x 2 factorial scheme, 14 herbicide treatments and 2 application times after planting (3 and 10 DAP), with four replications. The herbicides, at their recommended doses, were applied 3 or 10 days after seedling transplant of the varieties: RB 86 7515, RB 85 5156, RB 96 6928 and RB 97 5201. The percentage of phytotoxicity was evaluated at 7, 15, 30 and 60 days after application of the treatments (DAT). The height of the plants, leaf area and dry shoot biomass were evaluated at 60 DAT. The herbicides caused a differential impact according to the varieties and the time of application, however, in the last evaluation, there was low phytotoxicity in most evaluations. For RB 867515 herbicide application at both 3 and 10 DAP was safe, for RB 966928 and RB 975201 the application at 3 DAP caused less phytotoxicity, whereas for RB 855156 it was at 10 DAP. It is concluded that the varieties differ in phytotoxicity to the evaluated herbicides, being RB 867515 the most tolerant and the association saflufenacil + clomazone and clomazone caused greater initial phytotoxicity in the varieties and in the time studied.
Period of rain after saflufenacil application in controlling floating aquatic macrophytes
Saflufenacil herbicide can be one more alternative to control aquatic environment weeds, but at the time of or after the application of the herbicide bad weather such as rain, may invalidate the chemical control of problematic species occurring in this environment. Thus, the goal of this study was to evaluate the occurrence of different rain periods after applying saflufenacil herbicide to control water hyacinth and water lettuce plants. The study was conducted in plastic pots with 2.5 water liter capacity and kept in greenhouse conditions. The experimental design was completely randomized with nine treatments and four replications. Treatments consisted of rainfall simulation performed through a stationary sprayer in periods after the application of the herbicide: 0; 0.25; 0.5; 1; 2; 4; 6; and 12 hours, as well as a period without rain. Saflufenacil was applied at a 33.6 g ha-1 dose and evaluations were performed 7, 14, 21, 28 and 35 days after herbicide application. The occurrence of rain at intervals of more than two hours after the application of saflufenacil did not change the effectiveness on water hyacinth. As for water lettuce plants, there was an effective control with a minimum of four hours for the occurrence of rain after application of the herbicide. Finally, for all plants, periods equal to or higher than six hours after the application of saflufenacil provided total control over water hyacinth and water lettuce plants.
Phytosociology of weeds in bean crops with different herbicides control
Knowledge on changes in weeds communities caused by weeds management practices is important when effective strategies for the control of these species are set. A field experiment was conducted to assess the effects of herbicides applications with different sprayer boom heights on the weeds dynamics and beans yield. A 3x4+1 factorial arrangement was adopted, comprised of the combination of three herbicides (fomesafen. fluazifop-p-butyl and a mixture of both) and four different boom heights (0.20; 0.30; 0.40 and 0.50 m above target) and one control (non-weeded check). Thirty days after application (DAA), the following phytosociological indices were determined: relative frequency, relative density, relative dominance, and importance value. Sixty days DAA, yield rates were determined. Prior to the experiment installation, 22 species were identified in the entire experimental area. The species Alternanthera tenella, Chelidonium majus, Digitaria horizontalis and Bidens pilosa dominated the area where there was no weed control. Reduced boom heights for application of fomesafen diminished the importance of dicot species. In the plots with fomesafen + fluazifop-p-butyl applications, the number of dicot weeds was greater than the other species, with predominance of A. tenella e B. pilosa. In general, the similarity index between the different herbicides and different boom heights was low, which indicates that the treatments used result in different weeds populations. Bean crops reduces the weeds diversity, and the application of herbicides has a positive effect on weeds infestation, with consequent gains in productivity.
Tolerance cassava to different herbicides applied in post-emergence
Cassava has a long cycle and slow initial growth, which facilitates development of weeds that will compete with the culture. It was aimed to evaluate the tolerance of cassava cultivar Aciolina, the different herbicides in the early stages of crop development. The experiment was conducted in a greenhouse, in a completely randomized design with four replications. The evaluated treatments were: haloxyfop (60 g ha-1 a.i.), lactofen (180 g ha-1 a.i.), chorimuron-ethyl (17.5 g ha-1 a.i.), bentazon (576 g ha-1 a.i.), bentazon + imazamox (600 + 28 g ha-1 a.i.), imazethapyr (100 g ha-1 a.i.), fomesafen (250 g ha-1 a.i.), quizalofop-P-ethyl (62.5 g ha-1 a.i.), lactofen + quizalofop-P-ethyl (180 + 62.5 g ha-1 a.i.), fomesafen + quizalofop-P-ethyl (250 + 62.5 g ha-1 a.i.), and a control. Were performed visual assessments of intoxication, plant height and number of leaves, dry mass of the leaves, stem, root dry mass total and leaf area. The herbicides bentazon, fomesafen and fomesafen + quizalofop-P-ethyl caused high injury but not affect the development of plants. The imazethapyr herbicide interfered in development of culture by reducing in 58.03% the height and 35.87% dry weight of plants. Deformations were observed in young leaves with treatment bentazon + imazamox. The use of lactofen + quizalofop-P-ethyl resulted in plant death, the use of lactofen significantly reduced all variables. Cassava, cv. Aciolina, showed tolerance to herbicides haloxyfop and quizalofop and chlorimuron-ethyl. The lactofen, imazethapyr, bentazon + imazamox and quizalofop + lactofen cause severe damage to the cassava crop.
Performance of herbicides for weed control in sorghum
Chemical weed control in sorghum crop is limited by the low quantity of herbicides registered for the crop. Studies on the effects and effectiveness of herbicides in sorghum crop are essential to increase alternatives for the control of weeds. In this context, the present study was to evaluate the effect of intoxication caused by herbicides in sorghum, as well as the effectiveness of these for weed control. The experiment was conducted the field in a randomized block design, evaluating eight treatments with four replications. The treatments consisted of three herbicides applied preemergence (g ha-1): trifluralin (1200), S-metolachlor (768) and clomazone (1000); four treatments with postemergence herbicides applied: bentazon (720), bentazon + atrazine (480 + 880), atrazine (2200) and bentazon + pendimethalin (720 + 1000); and a check without herbicide (control in weed). Herbicides applied preemergence (clomazone, trifluralin and S-metolachlor), caused high toxicity in the sorghum plants. No injuries were observed in sorghum plants by the use of herbicides in postemergence. The clomazone and trifluralin herbicides had control for all evaluated monocotyledonous weeds, though the S-metolachlor only did not get to control C. echinatus. The use of atrazine or mixture with bentazon showed promising to control dicotyledonous weeds.
Volatility of clomazone formulations under field conditions
Volatilization plays an important role in the process of herbicide dispersion in the environment. The physicochemical characteristics of the clomazone molecule indicate its volatility potential. The present study aimed to evaluate the volatilization rate of three clomazone formulations under field conditions using indicator plants and wind tunnels. Transparent polyethylene tunnels were placed on a sorghum (Sorghum bicolor) field parallel to the prevalent wind direction, and the herbicide formulations were applied in plastic trays containing 10 kg of sieved soil and placed at the center of the tunnel. The experiment was arranged in a slip-plot design with four replications. The main plots were represented by different formulations of the herbicides: Gamit 360 CS®, Gamit 500 EC® and Gamit Star®, and control plots without herbicide application. The sub-plots represented the distances from the application site: 1, 2, 3, 4, 5, 6 meters. Herbicide injury in sorghum was then assessed at different days after application. The symptoms of all formulations were more intense in the plants that were closer to the application site, and were even more severe in the prevailing wind direction. In general, regardless of the application distance, Gamit 360 CS® caused less injury to the sorghum. It is concluded that among the formulations assessed, Gamit 360 CS® has a lower volatilization rate and, consequently, lower contamination risk of neighboring crops and the environment. The other two formulations have higher volatility potential.
Perennial sourgrass control in full flowering growth stage
The sourgrass is a difficult plant to control, because the vegetative survival characteristics and mainly because the glyphosate resistance. The aim of this study was to evaluate the efficacy of grass herbicides to control the perennial sourgrass in full flowering growth stage. It were installed two field experiments, in the first experiment, it was tested 4 graminicides in a single application and rate the percentage of control at 14 and 28 DAA. In the second experiment, it was applied 17 treatments (application A) and after 35 days it was sprayed the sequential application using clethodim + glyphosate (Application B), in this experiment it was evaluated the percentage of control at 14, 28 and 35 days of the first (A) and the second application (B), as well the dry biomass. In the first experiment, none treatment provided acceptable control using the single application. In the second experiment, the results showed that the first application also were not effective to control the sourgrass, however 35 days after the sequential application (B), the treatment using haloxyfop-methyl at 100 g a.i ha-1 associated with herbicide clethodim were efficient to control perennial sourgrass and consequently decreased their dry weight. The results showed that only one application of graminicides was not effective to control perennial sourgrass at full flowering, being necessary a sequential application (A + B) to efficiently provide the complete control at this growth stage.
Physiological changes in pequi (Caryocar brasiliense) leaves caused by glyphosate application
The use of herbicides is essential for the control of weeds and increase crop productivity, but these products can affect the physiology and growth of non-target organisms, including native plants. The objective of this research was to evaluate in the heated greenhouse the gas exchange, fluorescence of chlorophyll a and chloroplastid pigment content of pequi plants (Caryocar brasiliense) submitted to simulated drift of glyphosate. The treatments were arranged in a randomized block. Seven doses of glyphosate were tested: 0 (control), 50, 100, 250, 500, 1,000 and 1,500 g ha-1 of the acid equivalent. The herbicide was applied at 120 days after transplanting the seedlings. Evaluations of gas exchange and chlorophyll fluorescence were taken 24, 48 and 240 hours after application (HAA) of the herbicide. The chloroplastid pigments was evaluated the 240 HAA. There were reductions in photosynthetic and transpiration rates, stomatal conductance, the effective quantum yield of photosystem II, in the potential quantum yield of photosystem II and apparent electron transport rate, except for the relationship between internal and external CO2 concentration and extinction coefficient photochemistry not that there was an increase, due to the increase of the glyphosate doses. Similarly, the 240 HAA were observed reductions linear in the values of the variables chlorophyll a, b, carotenoids and relation chlorophyll a/b. Glyphosate causes changes in photosynthetic variables with reductions in the characteristics of gas exchange, photochemical efficiency and chloroplastid pigment content, especially as exposed to higher doses of the herbicide.
Action of PROTOX inhibitors herbicide on the development, lodging and yield of soybean
Soybean is the most important leguminous species worldwide and therefore investments in technologies are needed to increase productivity and reduce adverse factors to the crop. In Southern Brazil, there are often problems caused by lodging of plants from some soybean cultivars. This study aimed to evaluate the effects of application of Protoporfirinogênio Oxidase (PROTOX) inhibitors herbicides on development, yield and components and plant lodging on the cultivar CD 214 RR. The experiment was conducted under field, in randomized block design with four replications in a factorial model. Factor A included five herbicides treatments: carfentrazone at doses 6, 10 and 22 g ha-1 of a.i., lactofen 144 g ha-1 of a.i. and control without application. The factor B consisted of six assessment times of injury and seven times for plant height and lodging. Soybean plant injury, height, lodging, yield, yield components and biological yield are assessed. The lactofen and carfentrazone herbicides were able to reduce the height and consequently the soybean lodging. Carfentrazone was more phytotoxic and more effective in reducing the soybean plants height than lactofen. Lactofen resulted in soybeans grain yield higher than different concentrations of carfentrazone, although both did not differ in yield grain of the control without herbicides.
Residues of glyphosate and aminomethyl phosphonic (ampa) in genetically modified soybean
Successive and arbitrary application of glyphosate may cause cases of intoxication in humans by indirect ingestion, since transgenic soybeans present levels above the permitted for this herbicide. The objective of this study was to evaluate the glyphosate and aminomethyl phosphonic acid (AMPA) levels in genetically modified soybeans tolerant to glyphosate. The chosen experimental design was composed by random blocks of eight treatments and four replications. Treatments consisted in glyphosate, applied only once and singly in doses of 720 and 960 g a.i. ha-1, glyphosate at 720 and 960 g a.i. ha-1 in mixtures, respectively, with com chlorimuron-ethil at 10 g a.i. ha-1, sequential applications of glyphosate in doses of 720/720; 960/720; 960/720/720 g a.i. ha-1 and a control group weeded throughout the entire cycle. The samples were analyzed by high efficiency liquid chromatography (HELC). Evaluated characteristics were: residue levels (mg kg-1) of glyphosate and its metabolite AMPA. The highest glyphosate residue level found in the soybeans was 0.92 mg kg-1, less than the highest permitted, which is 10.00 mg kg-1. Residues of AMPA were also found, with the highest level being 1.53 mg kg-1, indicating glyphosate metabolization.
Glyphosate application associated to non-purified residue of biodiesel production: analysis of different prototypes
Glyphosate is an agricultural pesticide of great importance in the world. In this sense, several studies have been developed in order to select adjuvants which elevate the efficacy of the product. Two experiments were performed with the goal to evaluate the efficacy of the glyphosate herbicide when associated to different experimental prototypes of agricultural adjuvants, elaborated from non-purified residue ofbiodiesel production. Gross residue from the biodiesel production was used, as well as its dilution in water, and addition of ammonium sulfate, KOH and/or soybean oil. Control of morning glory (Ipomoea triloba L.) was evaluated in experimental plant nursery, as well as the infestation of weeds in the field condition. In general, the presence of adjuvant prototypes in glyphosate herbicide spray did not result in an increase of the control in any experimental condition, as well as, it did not reduce the efficiency of the product.
Editors of the Revista Brasileira de Herbicidas acknowledge the important contribution of the reviewers during the year 2015.
The Editorial Board of the Revista Brasileira de Herbicidas - RBH has the honor to present the first issue of the year 2016. The work consists of twelve review papers with relevant topics that impact on chemical weed control. The authors are renowned Brazilian researchers, working in various institutions of teaching and research. The year 2016 has special significance for RBH, since it is the consolidation as one of the main sources of information on the Integrated Management of Weed, with emphasis on chemical control. A major reform was proposed by the new team of editors, significantly changed since the submission system to paper display in the final version. The result can already be found by reducing the time between submission and publication of accepted articles. This special edition is also celebrating a unique moment for the Brazilian Weed Science Society – SBCPD, since celebrates the 30th edition of the Brazilian Congress of Science of Weed, confirmed for the city of Curitiba, from 22 to 26 of August of 2016. The event expects to gather more than 1000 congressees, including undergraduate and graduate students, technicians, growers, professors, researchers among others from Brazil and several other countries. Following the impressive success of the 29th Congress in Gramado (RS), Curitiba is believed to be an excellent setting to discuss the current progress of weed science, the development of novel herbicides based upon new concepts, and the advances in weed resistance to herbicides that will change our approach in crop management in the forthcoming years. Today, it is easy to envision a future where weed science will be based on a deeper understanding of fundamental concepts of weed biology, application technology, environmental fate of herbicides, new traits, and the challenge of weed resistance to herbicides. Weed scientists are now well positioned to take advantage of the major advances achieved in the last few years in herbicide physiology and crop biotechnology. The upcoming 30th CBCPD will be a unique opportunity to listen to worldwide opinion leaders who will share with us the recent innovations in their respective fields. Young scientists and students are especially encouraged to present their recent findings through the poster session. A good number of activities are under preparation to attend the next generation of Brazilian weed scientists. In addition, a major effort is underway to bring a significant number of consultants and extensionists, what will bring a refreshing new approach to research and academia fellows. We are looking forward welcoming you in Curitiba, one of the most charming cities in Brazil. With our best personal regards.
Herbicide and nematicide interaction in sugarcane crops
Sugarcane has great economic importance in Brazil. In order to maintain its yield, several biotic and abiotic factors can have a positive or negative influence. Among them, it is possible to mention weeds, nematodes and the synergistic action among pesticides in order to control both. Thus, the present work had the objective to study the interaction between herbicides and nematicides used in sugarcane crop. The experimental design was completely randomized, in a 5 x 3 factor scheme, with four replications. The first factor corresponds to sulfentrazone (800 g ha-1 a.i.), saflufenacil (98 g ha-1 a.i.), diuron + hexazinone (1170 g ha-1 a.i. + 330 g ha-1 a.i.), amicarbazone (1050 g ha-1 a.i.) plus the control sample; the second factor corresponds to the nematicides benfuracarb (2000 g ha-1 a.i.) and carbofuran (1750 g ha-1 a.i.) plus the control sample. Nematicides were applied in contact with billets and herbicides applied during the pre-emergence of the crop; this was perfomed on the RB867515, RB975201 and RB975952 sugarcane varieties. Evaluations of phytotoxicity were performed at 7, 15, 30, 45 and 60 after emergence (DAE) of the crop. During the last evaluation, the biometric parameters of height, leaf area and dry biomass of the aerial part were determined. All plants recovered after 60 DAE, and in treatments with the use of sulfentrazone higher intoxication symptoms were observed. As for the biometric parameters evaluated at 60 DAE, there was no significant interaction for herbicide and nematicide factors, but there was a difference between treatments in each variety.
Association of the herbicides diclosulam and glyphosate on soybeans burndown aiming residual control of weeds
The association of glyphosate and diclosulam in burndown can reduce the presence of weeds for a longer period, thus promoting the development and productivity of soybean plants. The objective was verify if the efficiency of the herbicide diclosulam associated with glyphosate, in burndown for direct seeding, in the seed bank of weeds in soybean grown in the plant system and apply. The straw present was Urochloa ruziziensis at 4.4 t ha-1 of dry mass, uniformly distributed over the experimental area. The experimental design was randomized blocks design with three treatments and four replications. The treatments consisted in the application of glyphosate at 1.2 kg ha-1 acid equivalent (a.e.) + diclosulam 25.2 g ha-1 active ingredient (a.i.) in pre-sowing without the complementary application, glyphosate at 1.2 kg ha-1 + diclosulam 25,2 ha-1 in pre-sowing of the culture + 1,2 kg ha-1 of glyphosate in complementation and glyphosate at 1.2 kg ha-1 in pre-sowing + glyphosate at 1.2 kg ha-1 in complementation. It were evaluated the initial reinfestation and relative density of weeds at 31 days after burndown, reinfestation of weeds at harvest time, difficulty of mechanized harvesting, number of pods per plant, 1000 grain weight and productivity. The association of the herbicides glyphosate and diclosulam assists in the initial management of weeds in soybean, without, however, dispense the complementary application of glyphosate.
Morpho-anatomical aspects and technological quality of saccharine sorghum submitted to plant regulators
With the increase in the demand for renewable fuels, the sugarcane industry must seek a way of increasing agro-industrial productivity while reducing production costs. Currently, there are few reports on the use of plant growth regulators in saccharine sorghum crops. The objective of this study was to evaluate the effects of the application of chemical ripening agents on the technological quality and the morphological and anatomical aspects of saccharine sorghum. The experiment was conducted at the Cerradinho Mill in Catanduva, São Paulo state. Plant growth regulators applied were etephon at 1.32, 0.66 and 0.33 L ha-1, sulfometuron-methyl at 20.0, 10.0 and 5.0 g ha-1, thiadizuron at 0.150, 0.100 and 0.50 L ha-1, ethyl-trinexapac at 0.80, 0.40 and 0.20 L ha-1 and a control treatment. The experiment was conducted in randomized blocks with a subplot design with four replications. The following technological parameters were evaluated: juice purity, reduced sugars, total recoverable sugars, juice brix, juice pol, theoretical recoverable sugars and fiber (%). The thickness of the upper face or adaxial epidermis (AdE), the thickness of the lower face or abaxial epidermis (AbE), sclerenchyma diameter (SD), mesophyll thickness (MT), diameter of xilematic vessels (DX) and diameter of phloematic vessels (DP) were evaluated. It is concluded that saccharine sorghum showed a significant increase in technological quality when etephon was used at dose of 0.33 L ha-1, and at 0.66 L ha-1 between 37 and 44 days after the application of chemical ripening agents. For the technical characteristics, the chemical ripening agent sulfometuron-methyl and etephon in doses of 5 g. ha-1 and 0.33 L ha-1, respectively, promoted the best results from the 37 days after application. For anatomic characteristics of saccharide sorghum plants, the chemical ripener agent thiadizuron in dose of 0.100 L ha-1 showed the best results at 44 days after application.
Phytotoxicity clomazone associated with dietholate the crop wheat
Nowadays it has become important to test new alternatives herbicide molecules, even if they are not registered for the control of weeds that infest wheat, to evaluate the phytotoxicity to culture and the ability to manage resistant weeds to the products used for this purpose. Thus, an experiment was conducted to evaluate the Phytotoxicity of clomazone associated or not to the dietholate safener applied on wheat. The experiment was conducted in a completely randomized design, arranged in a factorial scheme (5 x 4) + 2 + 2, with four replications. In the factor allocated to dietholate doses (0, 120, 240, 360 and 480 g per 100 kg of seed) and the B clomazone doses (0, 198, 396 and 594 g ha-1). Additional Treatments were the control treatments infested and without the application of herbicide, and the application in post-emergence of iodosulfuron-methyl (5 g ha-1) and pyroxsulam (18 g ha-1). The increase in clomazone doses caused increased phytotoxicity to wheat, with or without the safener. The dietholate showed no ability to protect the wheat from the phytotoxic effects of the herbicide clomazone. The use of clomazone associated with dietholate for weed control on wheat is not recommended. The pyroxsulam was the herbicide that caused minor injuries to wheat.
Photosynthetic activity of cultivated plants in soil contaminated with sulfentrazone
The goal of this work was to evaluate the sulfentrazone effects on the characteristics associated with photosynthetic activity of Helianthus annus, Canavalia ensiformis, Dolichos lab lab and Arachis hypogaea regarded species with potential of remediation of contaminated soil with this herbicide. The experiment was conducted in factorial 4 x 3, completely randomized design, with four replications. The first factor consisted by cultivation of species H. annus, C. ensiformis, D. lab lab and A. hypogaea; the second factor by three sulfentrazone doses (0, 250 and 500 g ha-1) applied in pre-emergence. After filling the pots with 6.0 kg of soil, classified with red-yellow Hapludalf, it was done the irrigation and it was done the herbicide application herbicide in soil surface. One day after this application, proceeded the sowing of vegetal species. At 40 days after the emergency of the vegetal species, were evaluated the stomatal conductance (gs - mol m-1 s-1), transpiration rate (E - mol H2O m-2 s-1), sub-stomatal CO2 concentration (Ci - µmol mol-1), CO2 gradient (ΔC - µmol mol-1) and the photosynthetic rate (A - µmol m-2 s-1). These evaluations were performed using an infrared gas analyzer (IRGA). At 100 days after the plants emergency was collected the shoot for determination of shoot dry matter. Sulfentrazone residues in soil can affect the physiological variables studied, however, the shoot dry matter wasn’t influenced by the herbicide action, independently of the doses applied, indicating tolerance of the species to the sulfentrazone.
Herbicide selectivity applied in post-emergence in pearl millet
The knowledge of differential tolerance of pearl millet to different herbicides is critical to the success of chemical weed management in culture. The objective of this study was to evaluate the selectivity of different herbicides applied post-emergence on growing pearl millet. Two experiments were conducted in a greenhouse in a randomized complete block design with four replications. The first experiment involved the following herbicides (g. i.a.ha-1): atrazine (500 and 1000), bentazon (720), carfentrazone-ethyl (3.75), clomazone (400), diclosulam (20), diuron (800), ethoxysulfuron (18), flumioxazin (10), mesotrione (60), oxadiazon (500), tembotrione (40), atrazine + flumioxazin + carfentrazone-ethyl (300 + 5 + 2), and a control without application. In the second were used: bentazon (400), clomazone (400), diclosulam (10 and 15), diuron (400), ethoxysulfuron (15), bentazon + diclosulam (200 + 7.5), diclosulam + diuron (7.5 + 200), bentazon + diuron (200 + 200) and a control without application. In the first experiment, applications of herbicides clomazone, oxadiazon, atrazine + flumioxazin + carfentrazone-ethyl, flumioxazin, tembotrione and carfentrazone-ethyl showed phytotoxicity, unlike atrazine that did not cause visual symptoms in pearl millet, but reduced dry matter yield. Mesotrione herbicide in post-emergence application did not affect the pearl millet growth. In the second experiment the greatest injuries were caused by diclosulam and clomazone. However, all herbicides reduced dry matter accumulation of culture. It is concluded that the selectivity of herbicides depends on the product applied millet, and has the potential to mesotrione applied post-emergence of the crop.
Physiological characteristics of bean grown in soils after phytoremediation of picloram
Plant remediation has been reported as a promising technique for decontaminating soil herbicide residues. For hormonal herbicides there is difficulty in determining waste by bioassay technique due to the variation in growth in response presented by the indicator plant. The objective of this study was to evaluate the effect of doses of picloram through physiological characteristics of the bean in phytoremdiation soils with braquiaria. The experiment was arranged in greenhouse in the design of randomized blocks. Applied increasing doses of picloram (0; 2; 4; 8; 16 e 32 g ha-1), subsequently cultivated with Brachiaria for 120 days. In this date the brachiaria was harvested and sowed beans as bioindicator, 30 days after the emergence of the culture was evaluated the physiological characteristics and bean biomass accumulation. Even after remediation by plants Brachiaria, the doses of picloram affected the physiological characteristics of the bean, especially the water use efficiency, these variables are the most appropriate to evaluate the herbicide residues in the soil. The reduction of these variables promoted less accumulation of total biomass of bean plants in soils that was made remediation. The second higher dose of the herbicide also caused reduction of Fv / Fm ratio below 0.75, indicating some kind of stress photosynthetic apparatus of bean leaves.
Management of morning glory (Ipomea hederifolia, Ipomea nil, and Merremia aegyptia) with herbicides in raw sugarcane during dry seasons
The present research was carried out in a raw ratoon cane area located in Bocaina, SP, with cultivar RB85-5156, planted with a space of 1.4 m between the rows, on a sandy soil, with the objective of studying management alternatives with herbicides applied in the pre-emergence period during the dry season, adopting the randomized blocs design with four replications. In order to apply the herbicides, a CO2 pressurized backpack sprayer was used, with a constant pressure of 200 kgf.-2 and a reservoir with capacity for 2 L of solution, connected to a bar equipped with 6 spray nozzles model DG110.02, with a space of 0.5 m among each, providing an application rate of 200 L ha-1. The evaluations of weed control and phytotoxicity of the herbicides in the crops of sugarcane were done at 30, 60, 90 and 120 DAA. The data went through a variance analysis by the F test and the means were compared by the Tukey test at a 5% probability level. Herbicides diuron + hexazinone + sulfometuron-methyl, amicarbazone, amicarbazone + isoxaflutole, sulfentrazone, imazapic, and tebuthiuron + isoxaflutole can be considered alternatives to the efficient control of different species of morning glory (Ipomoea hederifolia, Ipomoea quamoclit and Merremia aegyptia) when applied to raw sugarcane during the dry season on sandy clay soils (medium texture). Regarding selectivity of the sugarcane crop, there were no significant phytotoxicity symptoms observed on the herbicides when applied in total pre-emergence until 120 DAA.
Biological weed management – A short review
At present, reducing the use of pesticides is sought out, for besides the environmental damage caused by them, there is concern about the consumption of food contaminated with possible residues. This literature review aims to address the use of bioherbicides, besides evaluating their prospects and potential to manage weeds infesting agricultural and nonagricultural environments. There is a growing need to find new molecules or methods able to control weeds found in agricultural and nonagricultural areas. Thus, bioherbicides have aroused the interest from researchers, technicians and producers. These can be formulated from substances produced by the secondary metabolism of plants and/or microorganisms. Research conducted points to efficient control with the use of bioherbicides, mainly related to the germination processes and development of weeds, and in some cases have a phytotoxic potential even when these are in advanced stages. Herbicides, in addition to being effective in weed control, reduce environmental damage caused by continuous use of synthetic herbicides. Brazil has the potential to use bioherbicides aiming to have plant diversity and the various agricultural crops systems practiced in the country.
Management of Sagittaria montevidensis resistant to ALS and PSII mechanisms of action with saflufenacil associated with different adjuvants
This study aimed at evaluating the effective rates of saflufenacil and adjuvants for controlling Sagittaria montevidensis (sagitaria) populations resistant to ALS and photosystem II (PS II) inhibitor herbicides, and phytotoxicity to the Epagri 108 rice cultivar. Two biotypes of sagitaria (SAGMO) were tested: SAGMO 10 – with cross resistance to ALS inhibitor herbicides, and SAGMO 32 - with multiple resistance to ALS and PSII inhibitor herbicides. Treatments consisted of three different saflufenacil rates: 75; 112.5 and 150 g a.i. ha-1 with the addition of adjuvants Dash HC® (0.5% v/v); Assist® (1% v/v); Iharaguen-S® (0.5% v/v) or Veget’Oil® (1 L ha-1). Evaluation focused on arrowhead control, phytotoxicity and shoot dry weight (DMAP) of the Epagri 108 rice cultivar. The saflufenacil rates of 75 to 150 g a.i. ha-1 did not provide efficient control for both sagitaria biotypes. Addition of the adjuvants Veget’Oil®, Assist® or Iharaguen-S® to saflufenacil did not alter the control efficiency of herbicide resistant sagitaria populations. The Epagri 108 cultivar presented selectivity to saflufenacil until 150 g a.i. ha-1, without reducing DMAP. The phytotoxicity caused by saflufenacil, to the rice plants was minimal with the addition of Veget’Oil®. Rice plants shoot dry matter was not affected, regardless of the adjuvant used. Saflufenacil can be used until the rate of 150 g a.i. ha-1 associated with adjuvant Veget’Oil® for the management of sagitaria in rice fields, but it does not provide adequate control of biotypes SAGMO 10 and SAGMO 32.
Imazapic effectiveness in itchgrass control applied in different soil textures
Itchgrass (Rottboelia exaltata L.f.) is a weed that presented fast dissemination in sugarcane fields in Brazil, causing significant yield losses to the crop. Therefore, this research had the objective of evaluating the susceptibility of the weed itchgrass to imazapic when applied in pre-emergence using dose-response curves. The experiments were carried out in randomized blocks experimental design with four replications in a factorial arrangement between two soil (clayey-sandy and sandy) and nine rates of imazapic. The herbicide rates were: 0; 9.19; 18.38; 36.75; 50; 73; 147; 294; 588 and 1176 g a.i. ha-1 and check without application. The sandy soil scored by visual control upper and lower levels of residual dry matter compared to the clayey-sandy soil. Soil texture has a direct influence on the effectiveness of control. Soil texture has a direct influence on control efficiency, so that the dose of 18.38 g a.i. ha-1 showed more control of itchgrass in sandy soil, while for clay and sandy soil was 294 g a.i. ha-1. Control levels indicate that application of imazapic in pre-emergence is viable to control the weed itchgrass.
Identification and management of Chloris polydactyla biotypes with resistance or differential susceptibility to glyphosate in the state of Paraná
The emergence of resistant weeds has increased costs and affected the production of crops for weed interference with cultivation and loss of effectiveness of herbicides widely used with large spectrums control and low cost, such as glyphosate. Thus, the study aimed to identify populations of C. polydactyla resistant or differential susceptibility to the herbicide glyphosate, at the State of Paraná, and establish its alternative control. It was collected biotypes suspected resistance in municipalities located in the West, Midwest and Northwest regions of state. Installed a test of resistant populations screening, in a completely randomized design with treatments 0, 450, 650 and 900 g a.e. ha-1 glyphosate herbicide, with 4 repetitions, assessing visual control with 7, 14 and 21 days after application − DAA and accumulation of fresh matter. Determined the alternative control by plants from different populations subjected to treatments: witness; glyphosate; quizalofop; haloxyfop; tepraloxydim, clethodim and the combination of these graminicides to glyphosate, by evaluating visual control at 14, 21 and 28 DAA and reduction of fresh matter. The state of Paraná has populations of C. polydactyla that require high doses of glyphosate to decrease its fresh weight or achieve adequate levels of control, and an alert to the emergence of resistant populations. The study populations of this species were easily controlled with the association of glyphosate and clethodim, in a commercial dose. It is extremely important to rotate active ingredients and mechanisms of action on the rural property due to specific characteristics of the target population.
Phytotoxicity of herbicides applied in post transplanting of seedlings of yellow passion fruit
Brazil is the world’s leading producer of passion fruit. However, for this crop, there are no records of herbicides for weed control. Thus, the aim of this study was to evaluate the effects of herbicide application after transplanting of yellow passion fruit seedlings during growth and phytotoxicity of the crop. Twenty-one herbicides with different mechanisms of action were tested by application at 35 days after transplanting (DAT). Phytotoxicity of the crop by the herbicides was evaluated at 63 DAT, and assessments of damage to seedlings were held at 70 days DAT. No herbicide caused damage to the root system of the passion fruit plants. The herbicides glyphosate, imazapic, metsulfuron-methyl and glufosinate-ammonium reduced plant height gain. The herbicides atrazine, linuron, metribuzin, diuron, tebuthiuron and bentazon reduced leaf dry matter, stem dry matter and total dry matter of the plants. Fluazifop-p-butyl reduced height gain and leaf dry matter. Herbicides that caused the greatest damage to seedling growth also caused the greatest phytotoxicity. The herbicides oxadiazon, fenoxaprop-ethyl, tembotrione, chlorimuron-ethyl and isoxaflutole did not hinder growth and did not intoxicate the seedlings; they were the most promising for use in the total area.
Residues of atrazine and tembotrione in the soil affect the initial growth of beets
The cultivation of beets is frequently done in a crop rotation system with cereals such as corn. In this case, herbicides with residual effect applied during corn growth can harm the establishment and growth of beets grown in succession. Therefore, three experiments were carried out in a greenhouse to evaluate the residual effect of atrazine and tembotrione, in isolation or in a mixture, on the initial growth of beets. The treatments consisted of six dosages corresponding to 0, 10, 20, 30, 40 and 50% of the recommended dosage. The evaluations were on: plant intoxication, shoot dry matter and SPAD index. Atrazine and tembotrione had a negative effect on the initial growth of beets, presenting reduction in the values of shoot dry matter and SPAD index, as well as increase in the intoxication as the dosage also increased. When the herbicides were applied in a mixture, the effect was enhanced, causing the death of plants in the highest dosages (40 and 50%). Due to these results, the cultivation of beets after the application of atrazine and/or tembotrione in corn crops may become impracticable due to the carryover potential in these situations.
Susceptibility of Merremia cissoides, Neonotonia wightii and Stizolobium aterrimum to the amicarbazone, imazapic and sulfentrazone herbicides
Three experiments were developed with the goal to evaluate the susceptibility of Merremia cissoides, Neonotonia wightii and Stizolobium aterrimum to the amicarbazone, imazapic and sulfentrazone herbicides, by means of rate-response curves. The experiments were installed in clay soil, where eight doses of each herbicide were applied, in pre-emergency. The used doses were: 8D, 4D, 2D, D, 1/2D, 1/4D, 1/8D, and check plots without application; whereas D is the recommended dose of amicarbazone (1200 g ha-1), imazapic (147 g ha-1) or sulfentrazone (800 g ha-1). For M. cissoides and N. wightii species, the three tested herbicides demonstrated effective control up to the 60 days, in the recommended doses. For the S. aterrimum species, only amicarbazone herbicide was effective, in the recommended dose. Control levels ensure these three herbicides as control options in pre-emergence for the M. cissoides and N. wightii species and only the amicarbazone herbicide, as control option for S. aterrimum.
Genetic heritage of the resistance of sourgrass to glyphosate
The gene flux through pollen and glyphosate resistance genetic inheritance in sourgrass (Digitaria insularis) is important to understand this species spread, but it was not previously characterized. This information is essential for the understanding of herbicide resistance evolution rate in agriculture and the gene flux between resistant and susceptible biotypes in the field. Therefore, the objective of this research was to quantify resistance gene inheritance among glyphosate resistant and susceptible biotypes, through the determination of the level of susceptibility to the herbicide in the F1 progeny. it was compared to the F1 generation susceptibility of resistant biotypes (MG) and susceptible (S), which remained isolated or induced to cross-pollination through pollination bags. The sensitivity to glyphosate was measured in the F1 progeny using dose-response curves. The F1 generation plants originating from a possible crossing between biotypes showed the same pattern of glyphosate susceptibility than the parent plant. Comparing the average of glyphosate resistant with susceptible biotypes a resistance factor of 4.01 was calculated. We conclude that there is no transfer of resistance genes after cross-pollination induction between susceptible and resistant biotypes. Further research is needed to determine if this occurred due to D. insularis species be exclusively autogamous or if the resistance is determined by more alleles, and thus does not follow the model of monogenic inheritance. Therefore, the dispersibility of sourgrass resistance genes can be attributed to seed dispersal and not for gene transfer between biotypes through cross pollination among plants, since this study shows imperceptible cross-pollination rates.
Dynamics of preemergent herbicides in production systems with straw
The use of production management systems with the implementation of cultures in the straw provides many benefits, including protection against soil erosion, increase in organic carbon content, increasing the microbial population, soil moisture conservation and emergence inhibition of some weeds. Given these changes, the preemergent herbicides used in the systems with straw are intercepted before reaching the ground and when leached from the straw they may present differences in their dynamics in the soil. It is important to consider the dynamics of herbicides both in the straw and in the soil, taking into consideration the straw origin, quantity and distribution, as well as the herbicides physicochemical characteristics and the intensity and the period without rain after application of the herbicide. All these factors determine the amount of the herbicide intercepted by straw and its behavior in the soil. Thus, the aim of this review is to understand the dynamic of preemergent herbicides applied in straw and soil in no-till systems, raw sugarcane and minimum tillage. The maintenance of straw on the ground can both intercept and retain the preemergent herbicides applied, reducing their ability to reach the straw layer and causing a reduction in weed control. The longer the time interval between the application and the occurrence of rain or irrigation, the lower the amount of herbicide leached to the soil. Therefore, in crops with soil covered with straw, herbicides that are less vulnerable to losses by volatilization and photodecomposition should preferably be used, in other words, herbicides with higher solubility, low vapor pressure and octanol-water partition coefficient.
Herbicide action in the severity of diseases in cultivated plants
The severity of diseases in plants can be affected by practices such as the application of herbicides for the control of weeds. Therefore, we aimed to present and discuss the relationship between the use of herbicides and the severity of diseases of cultivated plants. After contact, the pathogens try to infect and colonize the hosts, which, in turn, use mechanisms to defend themselves from infection. The trichomes, the cuticles and the epicuticular wax are barriers against penetration. Phenolic compounds, enzymes and phytoalexins are substances synthesized by plants and toxic to the pathogens. The herbicide action influences the severity of diseases indirectly on the defense mechanisms of plants or directly when it presents toxic effects to the pathogens. The effect of adjuvants in the commercial formula of herbicides causes degradation of trichomes, epicuticular waxes and cuticles, favoring penetration of pathogens. Harmful effects on the physiology and secondary metabolism of plants, caused by herbicides, affects the synthesis of the above mentioned defense compounds. However, the herbicide molecules may inhibit the germination of spores and the growth of fungal hyphae, which results on the reduction of the infection and colonization. Necrotic points resulting from herbicide action may make plants less prone to the occurrence of rust, mildews and powdery mildews, caused by biotrophic fungi. Herbicides also have secondary effects such as population reduction of alternative host plants and vector insects. The relationship between herbicides and the severity of diseases in crops is an important tool for the phytosanitary management in an integrated way.
Morphoanatomic characteristics of the sugarcane’s leaves under residual effect after ripeners application
The aim of this study was to evaluate the residual effects regarding the maturing on morphoanatomic characteristics relating the sugarcane’s leaves. The experimental design was a randomized block in a split plot. The plots were constituted by the following varieties of sugarcane (SP80-3280 and SP80-1842) and the subplots of different maturings: Curavial 20 g bw ha-1 (sulfomethuron-methyl); Curavial 20g bw ha-1 + Roundup 0.15 L ha-1 (sulfomethuron-methyl + glyphosate); Ethrel 0.67 L ha-1 (etephon); Ethrel 0.67 L ha-1 + Roundup 0.15 L ha-1 (etephon glyphosate +); Moddus 0.80 L ha-1 (ethyl-trinexapac); MTD 1,0 L ha-1 (Compounds of organic carboxylic radicals); MTD 1.0 L ha-1 + Roundup 0.15 L ha-1 (Compounds of organic carboxylic radicals + glyphosate); Roundup 0.15 L ha-1 (glyphosate); and check without application. The following quantitative parameters of the tissues were measured: thickness of the epidermis of the adaxial face; thickness of the epidermis of the abaxial surface; thickness of the mesophyll; blade thickness; diameter of the xylem; diameter and phloem. In general, the foliar morphoanatomic characteristics of the sugarcane showed higher average values for the residual effect of Ethrel maturing (etephon). The SP80-1842 variety demonstrated the highest values for most characteristics under study.
Biology and management of Rottboellia cochinchinensis
Rottboellia cochinchinensis (Lour.) Clayton, popularly known as itchgrass is the main weed of at least 18 crops grown in many countries. Therefore, it is proposed, in this review, to present biological and management aspects of this important weed species. It is an annual or perennial plant reproduced by seeds or from pieces of stems, reaching up to 4.0 m high. The seeds can remain dormant in the soil for up to four years and the light is not a limiting factor for germination. Although with the system clear/dark there is stimulating seed germination. The rapid development of the root system, with subsequent formation of the aerial part, favors the space occupation by plants. Furthermore, the decomposing plant waste of that species release to soil phytotoxic compounds which can inhibit germination and growth of adjacent or species, whether harmful or cultured. In rural workers, it cause skin irritation by contact, with rigid trichomes of leaf sheaths. There is little information in the literature on the chemical control of this species, especially for pre-emergence herbicides applied. This can be attributed to the difficulty of the product crossing the structure surrounding the seeds and thus reaching the embryo. In sugarcane, clomazone + imazapyr, clomazone + isoxaflutole and sulfomethuron + diuron + hexazinone, sprayed pre-emergence resulted in satisfactory controlling R. cochinchinensis.
Drift from herbicides application on cultivated and native plants: a review
Although the application of herbicides is essential for weed control and increased productivity of several crops, it is widely known that these products may affect non-target organisms. This impact may occur both in parallel to other cultivated crops, and in remaining vegetation next to farmland. Little is known about the effect that herbicides can present in these non-target species, and they are of considerable importance both in food production and in the conservation of natural landscapes. This study aims to address the different impacts that herbicides can cause in several cultivated species typically known and in native species that are important in environmental conservation.
Application rates and herbicide in weed control in pasture
Pastures formed with Cynodonn lemfuensis Vanderyst are excellent alternatives for feeding livestock. The competition from weeds can cause damage to pasture, and Vernonia polyanthes and Desmodium incanum are among the main competing species. The objective of this study was to evaluate the efficacy of different herbicides to control Vernonia polyanthes and Desmodium incanum, applied in high and low spray mix volumes. The experiment was established in an area formed for over 10 years by African stargrass (Cynodonn lemfuensis). The experimental design was a randomized block in a 2x7 factorial arrangement with two spray mix volumes of 50 and 200 L ha-1 and seven herbicides. Variables phytotoxicity on grass Cynodonn lemfuensis at 3, 7, 14, 21 and 28 days after application (DAA) and control of weed plants Vernonia polyanthes and Desmodium incanum at 7, 14, 21 and 28 DAA were evaluated. There were no high levels of phytotoxicity in the pasture. The treatments that provided the best controls of Vernonia polyanthes and Desmodium incanum were fluroxypyr-meptyl + triclopyr, 2,4 D + aminopyralid and 2,4 D + picloram. Spray mix volumes provided no significant differences in the evaluation of control after 28 DAA for herbicides, but were higher for some treatments at 7, 14 and 21 DAA. Thus, the lowest volume of spray mix (50 L ha-1) becomes a viable alternative in the control of these species in the pasture.
Herbicides carryover in systems cultivated with vegetable crops
The residual effect of herbicides in the soil on sensitive succeeding crops is known as carryover. Most studies on carryover in vegetable crops have been developed in other countries; however, the problems arising from this phenomenon are also a reality in Brazil. The limited information in the literature, together with the absence of alerts and periods of restriction in the instructions for use of herbicides sold in the country for sensitive vegetables grown in succession contribute to the occurrence of major damage to horticulturists. Herbicides carryover can cause injury, visibly or not, in vegetable crops, it can reduce growth and productivity, as well as compromise the quality of the product and even derail the area for cultivation for years. This review describes the dynamics of herbicides in soil and brings together several works about the residual effect of herbicides in vegetable crops. Further, it discusses the possible ways of monitoring cultivated areas through the analysis in laboratories or bioassays, and strategies to minimize the harmful effects in these cultures, which are highly sensitive. In this context, the integrated weed management is essential to reduce the need for herbicide use and accumulation these on the soil, reducing the risk of carryover, as well as legislative action for the inclusion of restriction periods of sensitive vegetables grown in the instructions for use of herbicides.
Nozzles hydraulic, adjunctive and fomesafen application time in controlling beggar's tick
The application of pesticides is affected by several factors. Among them, the time of application stands out, which can vary according to the target, the applied product and equipment used. This study aimed to evaluate hydraulic nozzles, adjuvant and fomesafen application time in controlling beggar's tick. The treatments were arranged in a factorial 4x2x2, with the first factor consisting in four nozzles (API-11002; even (E) flat-fan, AD/D-11002; twin flat spray, AVI TWIN-11002; air induction (AI) twin flat spray-TQ, and APM-09502; Flood jet spray). The second with two application times (3 and 16 hours) and the third in two tank mixtures (with and without the addition of nonionic adhesive spreader adjuvant). The treatments were evaluated at 7, 14 and 21 days after the application, through the number of live plants, plant height, visual analysis and at 21 days the dry matter of the aerial part was made. The application at 16 hours provided better control of all traits, the JLSIP nozzle stood out causing further reduction of dry matter and of living plants, and the addition of adjuvant potentiated the application control at 16 hours. The application time influences the action of fomesafen, and that its application at 16 hours provides greater control of B. pilosa compared to that performed at 3. The JLSIP nozzle increases fomesafen action, also the addition of adjuvant potentiates the effect of this nozzle and the application held at 16 hours.
Use of cover crops as a tool in the management strategy of sourgrass
The use of cover crops with potential to reduce the development of weeds in crops may represent an important tool in an integrated weed management. To do so, work to evaluate initial development of Digitaria insularis under cover crops residues on the soil surface was conducted in the 2014/2015 crop in a greenhouse. The experimental design was in randomized blocks in a (7x4) + 1 factorial arrangement, and the factors consisted in seven species of cover crops (Pennisetum glaucum, Crotalaria spectabilis, Fagopyrum tataricum, Urochloa brizantha cv. Piatã, Cajanus cajan, Eleusine coracana and Mucuna pruriens) and four levels of dry phytomass (4, 8, 12 and 16 Mg ha-1) plus the control treatment without cover crops, with four repetitions. M. pruriens, C. cajan e U. brizantha stood out in the suppression of D. insularis, and 4 Mg ha-1 of dry phytomass of these species were sufficient to promote an expressive reduction in the total number of plants emerged, germination speed index, dry phytomass of the shoots, leaf area, dry phytomass and root volume. For these species, from 8 Mg ha-1 of phytomass development of D. insularis was no longer detected. As for the other species, the control of D. insularis was efficient only with high amounts of phytomass (16 Mg ha-1). D. insularis was highly sensitive to the presence of residues on the soil surface, making cover crops cultivation an important tool for the integrated management of this species.
Management of volunteer plants in cultivation systems of soybeans, corn and cotton resistant to glyphosate
The introduction of new cultivation technologies for soybean, corn and cotton contributed to a significant increase in the productivity of these crops. A highlight among these technological advances is the resistance of these crops to glyphosate, which initially provided for better weed control, especially in areas with a great diversity of species. Additionally, from a practical point of view it can also be highlighted that the increased time span for weed control, looking at the possibility of applying glyphosate at various growth stages of RR® crops. However, the "convenience" provided by the possibility to apply glyphosate post-emergence for crops such as soybeans, corn and cotton, increased consumption of this molecule, resulting in continuous use by producers. The effect resulting from the use was an increased pressure for selection and consequently for the selection of biotypes resistant to this molecule. In addition to this, the presence of volunteer plants of soybean, corn and cotton resistant to glyphosate has been established in management systems, mainly in the succession of soybean-corn and soybean-cotton. This fact brings high control costs and demanded the use of alternatives for the management of these volunteer plants. In this context, the aim of this work to address and present some management strategies to control voluntary RR® soybean, corn and cotton in cultivation systems in succession of soybean-corn and soy-cotton.
Biological characteristics, resistance to herbicides and management of Amaranthus palmeri in agroecosystems
Herbicide-resistant populations of the species A. palmeri were detected in Brazilian crops in 2014. Plants from this species were never identified in Brazil before. In other places of the world, A. palmeri causes many crop losses due to its biological characteristics and its competitivity in agricultural systems. Furthermore, herbicide-resistant populations become an important management issue, especially in the case of multiple herbicide resistance. This literature review describes the biological characteristics of this species in order to understand its adaptation and potential for crop losses and, also, to help to identify weakness which might aid the plant eradication. The cases described are those of resistance of A. palmeri around the world, as well as the mechanisms responsible for this resistance. It is presented possible actions that allow the management and control of plants from this species in cotton, soybean and corn crops.
Association of glyphosate with other agrochemicals: the knowledge synthesis
The association of agricultural chemicals complies with many objectives, such as the simultaneous control of organisms, dosage reduction, increase in the efficacy and prevention of cases of resilience to pesticides. The current paper aims to summarize information on the association of glyphosate with nutrients, herbicides and other pesticides. The association of glyphosate with polyvalent cations (e.g.: Ca and Mn), in general, reduces the efficacy of the herbicide, which can be overcome with the addition of ammonium sulfate to the application spray. The association of glyphosate with other herbicides depends on the used dosages, on the vegetable species, on the evaluation period, on the plant's development stage and on the biochemical compatibility between the action mechanisms of the herbicides. The association of glyphosate with systemic herbicides, in general, presents higher compatibility and benefits in contrast to the mixture with contact herbicides. The association of the glyphosate with auxin mimicking agents, in general, results in a synergetic effect. The mixture of glyphosate with ALS inhibitors may generate synergetic, additive, or antagonistic effects, presenting higher dependence on the doses of glyphosate on the mixture. There are many examples of antagonism among glyphosate and contact herbicides, such as inhibitors of GS, FSII, FSI and PROTOX. There is a lack of publications on glyphosate associated with fungicides or insecticides, and they do not prove synergetic or antagonistic effects of this mixture. However, papers that document the metabolization of glyphosate by plants suggest the need to investigate the impact of insecticides and fungicides in the action of the herbicide.
Occurrence and importance of herbicide resistance caused by degradation enhancement for weed management
Non-target-site resistance (NTSR) to herbicides mainly caused by enhanced degradation is highly problematic due to the occurrence of biotypes with multiple resistance and is a new challenge for weed management and herbicide use. Recently, enzymes associated with xenobiotic degradation especially cytochrome P450, GSTs and ABC transporters have been associated with the herbicide resistance in several weeds. This knowledge opens a new window to understand the evolution of NTSR. The aims of this review are to discuss the current knowledge of the gene regulation associated with the herbicide resistance caused by enhanced herbicide degradation and to analyze the main consequences of this problem for the adequate herbicide use and weed management. Multiple herbicide resistance caused by degradation enhancement occurs in Lolium rigidum, Alopecurus myosuroides, Echinochloa phyllopogon and in several other species. The level of herbicide resistance caused by degradation enhancement is affected by environmental factors in several cases, which difficult the resistance diagnostic and facilitate its distribution. The modern weed management should consider the characteristics of the herbicide degradation, since the simple rotation of herbicides mechanism of action might not be enough to prevent the herbicide resistance. The use of synergistic mixtures of herbicides and other enzyme inhibitors may contribute to prevent the evolution and spreading of NTSR weed herbicide resistance.
To ensure the maximum forestry productivity the adoption of efficient managements is essential. Weed control is very important, since presence of weeds can lead to competition for key factors to plant development. Weed interference can cause losses of up to 50 % in productivity and over 90 % of reduction in the profitability of forestry areas. Chemical control is widely used in weed management and about 30 % of the total costs of production and up to 50 % of the work force used in eucalypt crop cycle are intended for this purpose. Brazilian forestry sector has great economic expressiveness, but there are few herbicides registered. Chemical weed control should still fit the standards required by eucalypt certifications. The expansion of sector and the economic importance of this crop in Brazil make necessary the development of new herbicides and new spraying techniques to increase herbicides efficiency, new research, as well as encouraging adoption of an integrated weed management plan in eucalypt.
Alternative control of ryegrass biotypes resistants to clethodim
Ryegrass is an annual cycle weed, present in winter crops, orchards and vineyards of southern Brazil. The species is typically controlled by the herbicide clethodim. However, continued use of this product selected resistant biotypes. Thus, the objective of this research was to evaluate the response of ryegrass populations resistant to clethodim to the application of herbicides of different mechanisms of action, and propose chemical control alternatives. An experiment was carried out in the Brazilian city of Coqueirosdo Sul, in a randomized block design with three replications. The treatments assessed were: nicosulfuron (60 and 120 ga.i. ha-1), iodosulfuron-methyl (6 and 12 g a.i. ha-1), paraquat (400 and 800 g a.i. ha-1), ammonium-glufosinate (600 and 1200 g a.i. ha-1), clomazone (750 and 1500 g a.i. ha-1), tembotrione (100 and 200 g a.i. ha-1), clethodim (144 and 288 g a.i. ha-1), haloxyfop-methyl (60 and 120 g a.i. ha-1) and a control without the application of a herbicide. Herbicides tembotrione, nicosulfuron, iodosulfuron-methyl, clomazone, clethodim and haloxyfop-methyl were not efficient to control ryegrass. However, only herbicides paraquat and ammonium-glufosinate caused weed control and may be used to control populations of ryegrass resistant to herbicide clethodim.
Bioassays of 2,4-D with earthworms in different soil classes
2,4-D is a highly toxic herbicide, neurotoxic, teratogenic, possibly carcinogenic and well-known by its capacity of causing damages on human health and biota. This work proposes the assessment of 2,4-D toxicity levels in four Brazilian soil classes, using bioassays with earthworms (Eisenia andrei). Acute toxicity tests were performed with one sedimentary, two colluvial and one residual soils previously infected with solutions of agronomical concentration. No significant levels of mortality were observed, suggesting low acute toxicity to soil earthworms. However, the results revealed that lower levels of toxicity were linked to the textural appearance and high microporosity. The largest toxic potential was attributed to the quartz sandy soil. Such results may support the future establishment of toxic reference values able to reflect Brazilian pedological occurrences, subsiding future ecological risk assessments and decision-making in actions of environmental health.
Bianca Carolina Resende Carneiro da Rocha
Evolution, epigenetics and resistance – troublesome weeds
The aim of the present text is to recall basic concepts about evolution, neo‑darwinism and mechanisms of plant selection, pooling this knowledge into the weed science as a background which paves the way for the appearance of weed biotypes resistant to herbicides. Some questions which need to be answered regarding current concepts in weed resistance are risen. Epigenetics, secondary metabolism and environment related studies may change our view into plant resistance to herbicides.
Flumioxazin and S-metolachlor efficiency and selectivity in preemergence application of cassava ‘Baianinha’
This study has aimed to evaluate selectivity and efficiency in weed control of flumioxazin and S-metolachlor in ‘Baianinha’ cassava crops. The experimental design was randomized blocks with four replications. Treatments consisted in doses of flumioxazin of 50, 75, 100 and 125 g ha-1 a.i. and doses of S-metolachlor of 960, 1920, 2880 and 3840 g ha-1 a.i., besides weeded and unweeded controls. Treatments application was carried on 10/11/2013, 13 days after planting (DAP) and cassava cuttings presented underground sprouts measuring 3.0 to 4.5 cm. Flumioxazin at the highest dose provided 61.5% reduction of weeds biomass while S-metolachlor at the highest dose reduced 63.7% in the weeds biomass. Both herbicides have not promoted phytointoxication and have not altered roots yield and starch content of cassava plants. In conclusion, the herbicides were selective for ‘Baianinha’ cassava and efficient in weed control. However, control level increased with increments of doses assessed.
Benghal dayflower control with different glyphosate formulations
Benghal dayflower (Commelina benghalensis L.) is a weed plant that easily infests agricultural areas due to its aggressive characteristics associated with reproductive aspects of the species. One important aspect of this plant is presenting its tolerance to the glyphosate. An experiment in greenhouse was conducted to verify the effects of different formulations and commercial products of glyphosate in controlling benghal dayflower. The experimental design was completely randomized, with four replications. The plants were grown in pots filled with eight liters of substrate each, consisting of soil, sand and tanned cattle manure until they have reached the stage of development of the second growth sector, when the following products and their commercial formulations were applied: Roundup Original® – isopropylamine salt; Trop® – isopropylamine salt; Roundup WG® – ammonium salt; Zapp QI® – potassium salt; Roundup Transorb R® = potassium salt and Crucial® – isopropylamine salt + potassium salt. The intoxication of benghal dayflower plants was visually assessed at 7, 14 and 21 days after application of the products, and leaf area, dry matter of leaves, dry matter of the stem, dry matter of root and total dry matter at 21 days after application. The treatments show significant differences in the toxicity of the plants after 14 days of application, and at 21 days it was found that the products Roundup WG® and Crucial® were more toxic to plants. The products Roundup WG® and Crucial® were highlighted with greater reductions in dry matter of the leaves, stem and total plant. In general, the benghal dayflower has not been effectively controlled by the products at the doses tested and/or by the application after the emission of the second branch of weed. Among the commercial formulations or products, the ammonium salt is highlighted – Roundup WG® and the mixture of isopropylamine salt with potassium salt – Crucial® presents higher efficiency in weed control.
Herbicides applied in pre-emergence to control Ipomoea spp. in sugarcane in dry season
The weed control through the application of long residual activity of herbicides is important strategy for the removal of these at different times of the year. The objective of this study was to evaluate the residual activity of herbicides applied pre-emergence of sugarcane on the morning glory of control in the dry season, and the selectivity of the herbicides sugarcane crop. The experiment was conducted in a randomized block design with four replications. The treatments were (g a.i. ha-1): hexazinone + diuron + sulfometuron (1,025.1 + 289 + 24.65); Amicarbazone (1,050); amicarbazone and sequential application of isoxaflutole (700 and 60); sulfentrazone (800); imazapic (133); tebuthiuron and sequential application of isoxaflutole (750 and 60), and a control without herbicide application. The hexazinone + diuron + hexazinone and amicarbazone caused Ipomoea hederifolia control levels of 96% and 92.5%, respectively. As for the Ipomoea quamoclit, all herbicides studied provided excellent levels of control. For Ipomoea nil, the herbicides hexazinone + diuron + sulfometuron, amicarbazone, amicarbazone and isoxaflutole and sulfentrazone control showed very good to excellent, while tebuthiuron and isoxaflutole herbicides only good level of control (88.8%) and imazapic with unsatisfactory level of control (45%). Therefore, it can be concluded that hexazinone + diuron + sulfometuron (1,025 + 289 + 24.65 g a.i. ha-1), amicarbazone (1050 g a.i. ha-1), sulfentrazone (800 g a.i. ha-1), and the sequential applications amicarbazone (700 g a.i. ha-1) and isoxaflutole (60 g a.i. ha-1), they can be considered as excellent alternatives for the control of different morning glory species (I. hederifolia, I. quamoclit and I. nil), while the imazapic (133 g a.i. ha-1) and the sequential application of tebuthiuron (750 g a.i. ha-1) and isoxaflutole (60g a.i. ha-1) can be considered as alternatives to control only Ipomoea quamoclit when applied in pre emergence of sugarcane crop in the dry season.
Ryegrass seed viability in function of phenological stage of herbicides application
Ryegrass is an important weed in maize crops and winter cereals. The emergence of glyphosate-resistant biotypes, the main herbicide used in the Brazilian agricultural system, and the ability of natural reseeding, have raised the need to seek alternatives to minimize seed bank replenishment of this species. The objective of this study was to evaluate the effect of herbicide application at different growth stages of glyphosate-sensitive ryegrass plants on the viability of seeds from these plants. To this end, ryegrass plants were submitted to the application of glyphosate and clethodim association (750 g a.e. ha-1 + 120 g a.i. ha-1, respectively) in 10 in different development stages. The seeds produced were evaluated for their viability in tetrazolium test and germination in a B.O.D (Biochemical Oxygen Demand)-type growth chamber, with subsequent tetrazolium test and plants emergence in peat substrate. The results indicate that desiccation time limit for ryegrass to not produce viable seeds is the stage prior to complete anthesis, and at this stage there was complete reduction of viability, germination and emergence of ryegrass seeds exposed to the application of glyphosate + clethodim association.
Copyright (c) 2015 Brazilian Herbicide Journal
Selectivity and herbicides efficiency pre-emergence applied in papaya crop
In papaya culture, there is little information on selective herbicides when pre-emergence applied. A field experiment was conducted to evaluate the selectivity and efficacy of herbicides pre-emergence applied to control weeds in papaya cultivation. The experiment was conducted in a randomized blocks design with four replications. The treatments were: ametryn (1500 g ha-1 i.a.), diuron (1500 g ha-1 i.a), ametryn + diuron (1500 + 1500 g ha-1 i.a.), flumioxazin (50 g ha-1 i.a.) and isoxaflutole (150 g ha-1 i.a.), applied pre-emergence of weeds and before transplanting the papaya seedlings, as well as two controls, one kept in clean through hoeing and another without weed control. At 7, 14, 21 and 28 days after application (DAA) of the herbicides visual assessments of intoxication in papaya plants were made at 0, 28, 42, 56 and 72 DAA, plant height and stem diameter were evaluated, and at 21, 42 and 63 DAA the dry matter weight of the weed plants were evaluated. The herbicides ametryne, diuron, flumioxazin and the mixture ametryn + diuron caused the death of papaya seedlings, and isoxaflutole caused poisoning in seedlings with subsequent recovery. The weed interference resulted in papaya plants with smaller stem diameter, although the plant height was not influenced.
Paula Gracielly Morais Lima do Nascimento
Glyphosate application associated to different concentrations of non-purified residue of biodiesel production
Searching for renewable energy sources has motivated the development of biodiesel production units in Brazil. However, for biodiesel being considered fully sustainable, suitable destinations for its production waste should be found, especially for crude glycerin. Therefore, this work was developed to evaluate glyphosate herbicide efficacy on weed control when combined to different concentrations of non-purified residue of biodiesel production. Two experiments were carried out, one in an experimental plant nursery, using sourgrass (Digitaria insularis) as bioindicator, and another one in field condition, assessing the natural weed community. Adding biodiesel production waste to the spray mix solution has not increased glyphosate efficacy in controlling sourgrass. Furthermore, there was a reduction in glyphosate effectiveness after addition of waste to the spray mix solution at doses equal to or higher than 0.6% v/v. No results were found justifying the adoption of biodiesel production residue as an agricultural adjuvant. Positive points observed were minimal, with no consistency between species or application times, and glyphosate remains as the best application and recommendation option.
Non-proteinogenic amino acids potential use as allelochemicals
From existing amino acids, twenty are directly involved in the formation of proteins. The others are known as non- proteinogenic amino acids (NPAA). The NPAA have different functions, including anti-herbivory activity, antimicrobial, protection from stress, cell signaling, nitrogen storage, as toxins against invertebrates and vertebrates and as allelochemicals. Plants are able to release these metabolites in the soil, which may influence the growth and development of neighboring plants, both positively and negatively. The objective of this review is to describe the chemical characteristics, the allelopathic potential and selectivity for crops of non-proteinogenic amino acids m-tyrosine, L-DOPA, methionine sulfoximine and azetidine.
Chemical control of glyphosate-resistant volunteer maize
With the introduction in national agriculture of corn hybrids resistant to glyphosate herbicide, weed management, especially grasses, it was favored. However, volunteer maize plants coming from grains lost in mechanized harvesting can cause significant losses in crops subsequently sown, which has often been soybeans. Thus, the aim of this study was to evaluate the effect of different herbicides in controlling volunteer maize plants resistant to glyphosate herbicide. The experiment was conducted in the Brazilian municipality of Nova Xavantina, MT, between July and September 2014, in an area with a center pivot-type irrigation system. Grains of the F2 generation of AG 8061 VT PRO2® hybrid were used for assessments. The experimental design was randomized blocks with four replications. The treatments consisted in the application of thirteen different herbicides: haloxyfop-p-methyl 54 g a.i. ha-1; tepraloxydim 87.5 g a.i. ha-1; cyhalofop-butyl 247.5 g a.i. ha-1; fluazifop-p-butyl 156.25 g a.i. ha-1; sethoxydim 207 g a.i. ha-1; fenoxaprop-p-ethyl 96.25 g a.i. ha-1; chlorimuron-ethyl 15 g a.i. ha-1; imazethapyr 100 g a.i. ha-1; carfentrazone-ethyl 45 g a.i. ha-1; fomesafen 237.5 g a.i. ha-1; saflufenacil 35 g a.i. ha-1; flumioxazin 60 g a.i. ha-1 a and paraquat 450 g a.i. ha-1, in the V3 growth stage of maize and a control without application. Herbicides paraquat, haloxyfop-p-methyl, tepraloxydim, cyhalofop-butyl, fluazifop-p-butyl, sethoxydim, fenoxaprop-p-ethyl and imazethapyr were efficient in controlling maize plants resistant to glyphosate herbicide. These herbicides did not show satisfactory efficiency: chlorimuron-ethyl, carfentrazone-ethyl, fomesafen, saflufenacil and flumioxazin.
Impacts of the control of weeds and herbicides applied to natural enemies
Weeds compete for different resources with crops and the management of these plants is necessary so that production losses can be minimized. On the other hand, the diversity of plant species which behave as weeds can positively contribute to the survival of many arthropods and natural enemies. The objective of this review was to systematize the scientific evidence on the impacts of control of weeds and herbicides applied to non-target insects such as predators and parasitoids of pests, which are beneficial for agriculture and present in different agricultural crops. In this sense, consequences of control of weeds on insects present in agroecosystems were reported, as well as the potential risks of widespread use of herbicides on crops. Finally, this review compiles the current state of knowledge on ecological relationships in agricultural systems, focusing sustainable weed management, coupled with an integrated pest management.
Efficacy and phytotoxicity of herbicides applied for the handling of weeds that infest wheat
The objective of this paper was to identify alternatives for the chemical handling of weeds that infect wheat, as well as verifying the phytotoxicity of herbicides on the crop. The experiment was carried out in randomized blocks, organized in a factorial design of 2x 13, with four repetitions. The wheat crops were allocated to factor A (Quartzo and Pioneiro) and the herbicides to factor B (iodosulfuron – 0,100 kg ha-1; imazapic + imazapyr – 0,140 kg ha-1; clomazone 0,800 L ha-1; imazethapyr + imazapic – 1,250 L ha-1; propanil – 6,000 kg ha-1; oxyfluorfen – 1,000 L ha-1; penoxsulam – 0,175 L ha-1; metsulfuron-methyl – 0,0033 kg ha-1; 2,4-D – 1,250 L ha-1; cyhalofop-p-buthyl – 1,380 L ha-1; pyroxsulam – 0,400 L ha-1), plus two controls, one weeded and another one infested. Iodosulfuron, propanil, oxyfluorfen, metsulfuron-methyl, 2,4-D, cyhalofop-p-buthyl, penoxsulam and pyroxsulam cause values inferior to 5.5% of phytotoxicity to wheat crops and, in general, they did not differ from the weeded and infested controls. The greatest phytotoxic effects were caused by imazethapyr + imazapic, clomazone and imazapic + imazapyr on the wheat crops. The application of iodosulfuron, imazethapyr + imazapic, imazapic + imazapyr and pyroxsulam presented elevated control percentage of ryegrass, with rates above 95.5%. Imazethapyr + imazapic, clomazone and imazapic + imazapyr presented the greatest phytotoxicity on the wheat crops. Iodosulfuron, imazethapyr + imazapic, clomazone and imazapic + imazapyr and pyroxsulam showed the best controls for ryegrass. Iodosulfuron presented lower influence on the components of wheat grains yield when compared to the other herbicides.
Selectivity of fomesafen and clomazone associated with other herbicides applied in preemergence of cotton plant
A field experiment was conducted in Santa Helena de Goiás to evaluate the selectivity of herbicides fomesafen and clomazone and other combinations to cotton plants when applied in preemergence. The experiment was conducted in a randomized block design in a split plot design with four replications. The assessed herbicide treatments were: clomazone, clomazone + fomesafen (0.45 kg ha-1 of a.i.), clomazone + fomesafen (0.625 kg ha-1 of a.i.), clomazone + fomesafen + diuron, clomazone + fomesafen + prometryn, clomazone + fomesafen + trifluralin and clomazone + fomesafen + s-metolachlor. The visual symptoms of phytotoxicity were seen up to the evaluation of 19 days after emergence, and generally the injuries were higher where it was associated with three herbicides in the application. The treatments with clomazone alone and the associations clomazone + fomesafen (1.0 + 0.45 kg ha-1 of a.i.), clomazone + fomesafen + diuron, clomazone + fomesafen + prometryn, clomazone + fomesafen + trifluralin and clomazone + fomesafen + s-metolachlor were selective to cotton plant. The highest dose of fomesafen (0.625 kg ha-1 of a.i.) in associations with clomazone (1.0 kg ha-1 of a.i.) was not selective to cotton plant (cultivar DP 555 BG RR and in a clayey textured soil, with 3.1% of OM and pH of 6.0).
Copyright (c) 2016 Revista Brasileira de Herbicidas
Dry season and soil texture affect the chemical control of Senna obtusifolia in sugarcane
Because of its intrinsic characteristics, sicklepod (Senna obtusifolia) has gained importance in sugarcane, especially where there is a predominance of straw after mechanical harvest. The objective of this study was to evaluate the efficacy of preemergence herbicides used in sugarcane to control sicklepod in different soil textures and application timings. Two experiments were carried out for each application season (dry and wet), and one experiment for each soil textural class (clay and sandy clay loam), totaling four experiments. The treatments consisted in 17 herbicides in the wet season and 11 herbicides in the dry season (all herbicides were applied at 50 and 100% of the recommended dose) and a check without application for each season and soil, and the design was completely randomized. Soil texture and application timing have altered the herbicide efficacy. For the wet season, initially, all herbicides, except trifluralin and s-metolachlor, resulted in satisfactory control of sicklepod. Tebuthiuron was the herbicide that provided the longest period of residual control. For the dry season, amicarbazone, flumioxazin, hexazinone, imazapic, [diuron + hexazinone] F1 and isoxaflutole were efficient in both soils, but only in initial evaluations; [diuron + hexazinone] F1 and amicarbazone were the herbicides that provided the longest period of residual control.
Control of RR® volunteer corn with glyphosate + quizalofop-p-tefuril in tank mixture with multifunctional adjuvants or oils
The objective of this study was to evaluate the effectiveness of the glyphosate + quizalofop-p-tefuril in tank mixture with multifunctional adjuvants or oils for the control of RR® corn. The experiment was conducted over greenhouse conditions. The treatments were arranged in a factorial design 11 x 2, with six replications. The treatments consisted of factor A, applying glyphosate + quizalofop-p-tefuril (1080 g a.e. + 36 g a.i. ha-1 - T1) and associations of this with adjuvants, at doses of: 150 mL ha-1 TA-35® (T2); 150 mL ha-1 Orobor N1® (T3); 300 mL ha-1 LI 700® (T4); 100 mL ha-1 Triumph Flex® (T5); 100 mL ha-1 AllerBiw® (T6); 1000 mL ha-1 Fulltec® (T7); 1000 mL ha-1 Joint Oil® (T8); 1000 mL ha-1 Aureo® (T9); 1000 mL ha-1 Assist® (T10); plus a check without application (T11), and the factor B, corn hybrids DKB 240 RR PRO2® and DKB 245 RR®. The hybrids showed distinct symptoms at 7 days after application, regardless of the adjuvant used. DKB 240 RR PRO2® presented chlorosis, onset of necrosis of the edges of the leaves and only a few plants with reddish pigmentation, different from DKB 245 RR®, where there was more widespread reddening and necrosis of tips and edges of the leaves. No significant differences were observed in control of the hybrids using glyphosate + quizalofop-p-tefuril, associated with multifunctional adjuvants, mineral and/or vegetable oils.
Monitoring the occurrence of glyphosate-resistant sourgrass biotypes in the south region of Minas Gerais, Brazil
This work was developed with the objective of monitoring the occurrence of glyphosate-resistant biotypes of sourgrass (D. insularis) in Machado, Alpinópolis, Serrania and Divisa Nova, in the south region of Minas Gerais, Brazil. In each area, seeds of at least 20 plants were collected in full physiological maturity stage. For operational reasons, the analysis of different biotypes was divided into two timings, the first held in the second half of 2013 and the second in the first half of 2014. Plants were treated in the 4-5 leaves stage / tillering (First timing) and pre-flowering (Second timing); with the following treatments (D = 720 g ha-1 a.e.): 4D, D, 1/4D, 1/16D, 1/64D and herbicide absence. The percentage of control was evaluated at 14 and 28 days after application (DAA) as well as the residual dry mass at 28 DAA. Twelve sourgrass biotypes were considered susceptible to glyphosate; glyphosate differential susceptibility was detected between sourgrass biotypes; different management measures must be adopted to reduce the pressure of selection and the worsening of the situation.
Carryover of herbicides applied in the pre-emergence of cotton on the corn grown in succession
Herbicides that present long persistence in the soil can cause problems in crops sown in succession due to the soil's residual effect. That way, the objective of this paper was to evaluate the effects of herbicides applied in the pre-emergence of the cotton to the productivity of corn grown in succession. The experiment was installed in the municipality of Santa Helena de Goiás - GO. The application of herbicides treatments were carried out in a pre-emergence state of the cotton by using isolated clomazone or in mixtures of fomesafen, fomesafen + trifluralin, fomesafen + s-metolachlor, fomesafen + diuron and fomesafen + prometryn. In the condition in which the experiment was carried out, the results observed allowed us to see that the application of herbicides in the pre-emergence state of cotton crops did not have any significant effects in the insertion height of the cob, insertion height of the tassel, stem diameter and corn productivity, resulting in the absence of carryover on the hybrid corn RR® AG 7098 PRO 2, considering safe the sowing of corn 264 days after the application of herbicides.
Herbicides efficacy applied in pre-emergency to control Digitaria insularis in bean
Aimed to evaluate the herbicide efficiency applied pre-emergence for Digitaria insularis when glyphosate resistant control in bean crop. The experimental design was a randomized complete block design with four replications. Treatments consisted of seven different managements of D. insularis: weeded witness, witness without weeding, s-metolachlor (1.440 g ha-1 a.i.), clomazone (648 g ha-1 a.i.), imazethapyr (106 g ha-1 a.i.), flumioxazin (50 g ha -1 a.i.), imazethapyr + flumioxazin (106 + 50 g ha -1 a.i.). D. insularis were seeds sown a haul in the entire area at the rate of 300 seeds m-2. Two days after the sowing of D. insularis there was an application of herbicides. An hour before the application of pre-emergency herbicides there was an application of 1,440 g ha-1 of glyphosate, except as witnesses due to reinfestation of weeds. The cultivar BRS-Style beans were sown four days after the installation of the experiment. It evaluated Percentage of control and phytotoxicity and productivity of bean culture. The s-metolachlor and imazethapyr + flumioxazin herbicides were efficient control D. insularis and selective of the bean crop. The bean crop was increased productivity and similar to witness weeded with treatments s-metolachlor, imazethapyr and imazethapyr + flumioxazin.
Identification and control of Digitaria insularis biotypes resistant to the glyphosate
Some invasive species has shown potential to develop resistance to glyphosate herbicide in no-till areas. Herbicides inhibitors of ACCase enzyme may be an alternative control to Digitaria insularis (L.) Fedde. The objectives of this study were to identify the occurrence of resistance in D. insularis (L.) Fedde to glyphosate in tillage areas of the State of Paraná, and find the appropriate clethodim doses for its control. Were conducted two experiments in a greenhouse in Bandeirantes-PR, where the first was the experiment conducted with the glyphosate herbicide and the second with clethodim herbicide. Seeds of D. insularis (L.) Fedde plants were collected from five different places, and dose response curves were obtained for resistance verification. The tested doses were equivalent to 0; 0.5; 1; 2; 3 and 4 times the recommended dose of herbicide. The plants had 15 to 20 cm high when the herbicides were sprayed. The results showed that D. insularis (L.) Fedde biotypes from Paraná cities are resistant to glyphosate herbicide. Furthermore, it was found differentiated tolerance to the clethodim herbicide in the biotypes.
Organosilicone surfactant together with glyphosate in the control of Brachiaria decumbens
The research goal was to evaluate the effects of silicone surfactant and simulated rainfall in glyphosate efficiency in controlling Brachiaria decumbens. The experiments were carried out at (a unit of the University of São Paulo) Escola Superior de Agricultura Luiz de Queiroz (ESALQ – Luiz de Queiroz College of Agriculture) in greenhouse conditions, in a randomized block design with four replications. In one experiment, a simulated rainfall of 10 mm was carried out, 30 minutes after treatments application, and in the other there was no simulation. The treatments were arranged in a 5x3 factorial arrangement, with the first factor corresponding to the doses of glyphosate (0, 135, 270, 540 and 1080 g ha-1 a.e.), and the second one to the doses of silicone surfactant (0, 50 and 100 mL ha-1). The applications were performed at 30 days after sowing. In the presence of a simulated rainfall, the percentage of control was increased and chlorophyll content was reduced in the dose of 135 g ha-1 a.e. of glyphosate, together with 100 mL ha-1 of silicone surfactant. Increase in lipid peroxidation was also observed with the addition of 100 mL ha-1. In the experiment without a simulated rain, at seven days after treatments application, a higher percentage of control was observed at doses of 540 and 1080 g ha-1 a.e. with 100 mL ha-1 of silicone surfactant. Therefore, the use of silicone surfactant at a dose of 100 mL ha‑1 increases the efficiency of glyphosate in the control of Brachiaria decumbens in the absence of simulated rain and rain conditions held for half an hour after application.
Prohexadione-calcium isolated or in association with herbicides and other products in the handling of cotton pre-harvest
To maintain the quality of the cotton fiber, as well as to provide great yields on the harvest, some aspects must be taken into account such as the uniformity of the bolls and the defoliation; therefore, the use of herbicides and maturators become indispensable. Thus, the objective of this paper was to evaluate the efficiency of the prohexadione-calcium regarding its isolate application and in association with other products in the uniformity and opening of the cotton bolls, as well as the defoliation effect and regrowth of the crop. For such, a field experiment was carried out in the municipality of Diamantino - MT. The outline adopted was of randomized blocks with four repetitions and thirteen treatments, those being composed of control without application; prohexadione-calcium + ethephon + cyclanilide; prohexadione-calcium + flumiclorac-pentyl; prohexadione-calcium + diuron + thidiazuron; prohexadione-calcium + pyraflufen-ethyl; prohexadione-calcium; prohexadione-calcium + iharol. The treatments were applied when approximately 85% of the bolls of the crop 975 WS were open. The variables: apple opening, regrowth and defoliation were analyzed at 0, 3, 6, 10 and 15 days after the application (DAA) and, finally, the productivity of seed cotton was determined. Regardless of the dose, the plants that received prohexadione-calcium associated with ethephon + cyclanilide, diuron + thidiazuron and pyraflufen-ethyl presented a greater number of open bolls and greater defoliation. We can conclude that the different chemical treatments did not provide statistical differences regarding the regrowth of cotton before the harvest, at 15 DAA, and that the use of prohexadione-calcium, isolated or in association with other products, regardless of the dose, did not influence in the productivity of the seed cotton.
Residual effect of metribuzin in the soil on the growth of garlic, onion and beans
Metribuzin is an herbicide widely used in the control of weeds in crops such as soybean, potato and tomato. However, there is suspicion of intoxication in crops cultivated in succession due to the residual effect of the product in the soil. As such, our goal was to evaluate the residual effect of metribuzin in the soil on the growth of garlic, onion and beans plants. Three experiments were conducted in a greenhouse, in a randomized block design, with four replications. Each experiment corresponded to the evaluated crop: garlic, onion or beans. The treatments consisted of different metribuzin concentrations in the soil (0; 6; 12; 24; 48; 96; 144; 192; 240 and 480 ppb). Visual intoxication was evaluated at 7, 14, 21 and 28 days after emergence (DAE) of the crops and dry matter at 28 DAE. Intoxication was identified in the garlic and bean plants at metribuzin concentration of 96 ppb, with maximum impact of 55 and 63%, respectively, at 28 DAE. In the onion crop, symptoms of intoxication arose at 40 ppb, and from 14 DAE onwards, plant death was noted at herbicide concentrations from 240 to 480 ppb. The dry matter of the bean and onion plants was reduced by the presence of herbicide in the soil, while garlic plant growth was not affected. Residues of metribuzin in the soil can hinder successive planting of garlic, onion or bean crops. It was concluded that garlic, onion and bean plants are sensitive to the residual effect of metribuzin in the soil.
Brachiaria plantaginea resistance to ACCase-inhibiting herbicides
Weeds are the most important causes for soybean yield losses. Alexandergrass (Brachiaria plantaginea (Link) Hitchc.) is the main grass weed in the soybean crop in the southern region of Brazil. Chemical control has been intensively used to reduce the impact of this weed on soybean. However, the selection pressure imposed by agricultural weed control resulted in several biotypes of Alexandergrass resistant to ACCase-inhibiting herbicides. The proposal of a weed management system that prevents the development of resistence can be complex, but it has lower cost when compared to management systems after resistance has been established.
Plant resistance to herbicides inhibitors ofthe enzyme acetyl coenzyme A carboxilase (ACCase)
Weeds resistant to herbicide inhibitors of the enzyme ACCase present great economic importance throughout the world, due to the wide area infested and limited number of alternative herbicides and/or mechanisms of action availables for their control, This literature review intends to elucidate the mechanisms of weed resistance and of crop tolerance to herbicides inhibitors of ACCase. Weed resistance to ACCase inhibitors is due to alterations in the action site, plant metabolism, and membrane repolarization. Crop tolerance to these herbicides is due to alterations in the action site and to metabolismo The development of tolerant cultivars to ACCase inhibitors will allow selective control of weeds, constituting a promising alternative to manage and control weed species currently problematic. The introduction of herbicides with different mechanisms of action for grass weed control or the use of ACCase inhibitors jointly with herbicides differing in mechanism of action, associated with integrated weed management, are important strategies to be adopted in order to avoid appearance of resistance and to extend the period of utilization of such herbicides.
Weed management in corn with the herbicides sulfentrazone and carfentrazone-ethyl
Experiments were carried out with the objective of evaluating the weed management in com, spraying the herbicide sulfentrazone in pre-emergence conditions, alone or in combination with acetochlor and carfentrazone-ethyl herbicides in post-emergence conditions alone or in tank mix either with atrazine or nicosulfuron. The experiments were in completely randomized block design, with four replicates, in Piracicaba 1 SP, Brazil, in the experimental area of the Crop Production Department from University of São Paulo - ESALQ/USP. The weed control and the phytotoxic effects on the crop were evaluated as well as the final yield and plant height. The herbicide sulfentrazone was efficient in weed controI and selective to com crop sprayed in pre-emergence conditions at 0.15,0.30 and 0.45 kg/ha alone or when the same rates were applied in mixture with the herbicide acetochlor at 2.52 kglha; in post-emergence ofthe com crop the herbicide carfentrazone-ethyl was selective and efficient in the control ofweeds at the rates ofO.004 e 0.007 kg/ha, sprayed aIone or tank mix either with atrazine at 2.5 kg/ha, when the weeds are at the two pair of leaves growth stage; or with the herbicide nicosulfuron at the rate of 0.04 kg/ha, when the weeds are at the four pair of leaves stage.
Herbicides alachlor pendimethalin and trifluralin on the nodulation and initial growth of peanut plants
This work had the objective of evaluating the effect of the herbicides alachlor, pendimethalin and trifluralin on the initial growth of peanut plants (Arachis hypogaea L.) under greenhouse conditions for a period of thirty days as well as nodule number and dry weight for sixty days after the sowing period. The experiment was conducted at the Agronomy College of the Federal University ofBahia.The first experimental design was completely randomized with four treatments (control- rate zero; alachlor - 2.90 kg/ha, pendimethalin - 1.00 kg/haand trifluralin - 0.89 kg/ha) and three replieations. For each replication, plastie trays (70 em x 50 em x 10 em) were used with a yellow Latosol as the substrate and peanut seeds of the variety BRS 151-L 7 provided by EMBRAPA-CNPA. A seeond experiment was condueted with plastic pots of 5 kg, the same substrate, same treatments and experimental design with eight replieations. The following parameters were evaluated: seedling emergence, percentage of abnonnal seedlings and dead seeds, plant height, index of seedling emergenee velocity, root and shoot dry weight,number and dry weight of nodules. The results show that herbieides stimulate the initial nodulation of peanut plants, but reduce the pereentage of emergence, shoot dry weight and plant height. Therefore, the herbicides should be recommended with restrietions, for the studied eonditions. .
Efficacy of isoxaflutole in weed control in potato crop
This experiment was carried out at Bayer CropScience Experimental Station, in Paulínia, SP, Brazil, in a loamy soil cultivated with potato cv. Monalisa, during the 2002 growing season. The objectives were to evaluate the efficacy of isoxaflutole in weed control, to verify its selectivity to the potato crop and its effect on tubercule yield. The experimental design was a completely randomized block with seven treatments and four replications. The experimental plots consisted offour 7 m rows, with plants spaced in 0.60 m. The treatments were: controls (weedy and weedfree) and isoxaflutole rates (0.075, 0.150 and 0.300 kg/ha). Metribuzin (0.720 kg/ha) and linuron + metribuzin (0.910 + 0.384 kglha) were used as standards. The evaluations of the percentage ofweed control and the selectivity on the potato crop were carried out at 14, 28 and 42 days after treatment adopting a scale in which zero meant no weed control or no crop damage and one hundred corresponded to total control or death of the crop. The main weed species presented in the area were: Digitaria horizontalis Willd., Brachiaria plantaginea (Link.) Hitch, Galinsoga parviflora Cav., Raphanus raphanistrum L. and Amaranthus viridis L.. Potato plants did not show any visual symptoms of damage attributed to herbicide treatment. The species weed were efficiently controlled with isoxaflutole but there was no significant difference wheri compared with metribuzin. The treatments with isoxaflutole provided better control than linuron + metribuzin on grasses. Isoxaflutole did not affect the tubercule yield.
Dose of economical injury of cyanazine in corn
The tolerance of the com crop to the herbicide cyanazine depends on the growth stage of the crop. An experiment was conducted in Eldorado do Sul, RS, Brazil, to evaluate the selectivity of cyanazine applied at different rates on com, and at different growth stages, to estimate the economic impact of crop injury caused by the herbicide. The com hybrid AG 501 was planted on a no-till system where the weed control was performed with preemergence herbicides. Treatments tested were combinations of cyanazine (rates of 0.0, 2.0 and 2.5 kglha) at different growth stages (V3, V6 and V). Cyanazine selectivity decreases after the com crop reaches the six leaf stage, and with herbicide rates superior to 2.0 kglha. The rate of economic injury, that is, the herbicide rate which the benefit of the weed control is equivalent to the yield loss due to weed competition, reduces with the reduction of the economic impact of the weed on the crop, and with increased com price. These results suggest that when the weed infestation is almost above the weed economic threshold, the economic impact of the herbicide injury is higher than at high weed densities.
Cloransulam-methyl efficiency in postemergence control of Conyza bonariensis in RRTM soybeans crops
With the introduction of transgenic soybean resistant to glyphosate, which was widespread in southern Brazil, the number of applications and the selection of biotypes of horseweed (Conyza bonariensis) resistant to herbicide have stepped up. Thus, new chemical alternatives are essential for the efficient control of horseweed. Thus, the aim of this study was to evaluate the effectiveness of cloransulam-methyl (PactoTM), applied in postemergence, in controlling C. bonariensis and SYN 1059 RR VtopTM soybean yield. The experiment was conducted in the Brazilian municipality of Assis Chateaubriand, PR, in an experimental design of randomized blocks with four replications. The treatments consisted in doses of cloransulam-methyl (25, 30, 35 and 40 g a.i. ha-1), chlorimuron-ethyl (20 g a.i. ha-1) and weeded and unweeded controls. The horseweed plants were between 5 to 10 cm high and had an average density of 35 plants per m2. Cloransulam-methyl, at doses of 25 and 30 g ha-1, did not manage horseweed efficiently (< 80%) from 28 DAA (days after application), being inferior to chlorimuron-ethyl. However, cloransulam-methyl at 40 to 35 g ha-1 showed horseweed control (87.0% and 90.7%), which did not differ significantly from chlorimuron-ethyl at 42 DAA (85.7%) and it did not cause symptoms of injuries and soybean productivity reduction either. Cloransulam-methyl, despite not having been effective in controlling C. bonariensis at 30 g ha-1, showed soybean yield similar to the weeded control, and superior to chlorimuron-ethyl. The weed interference caused by the horseweed infestation reduced soybean yield in 47.5%.
The efficiency of glyphosate in the control of Brachiaria decumbens in guariroba crop (Syagrus oleracea)
This study was carried out to analyze the use, in total area, of different doses of glyphosate in guariroba crop to control Brachiaria decumbens in post-emergence. The commercial product Roundup Transorb (648 g of glyphosate 1L) was applied at the doses of: 972,1215,1458,1701 and 1944 g/ha. The experimental design was arandom blocks, with four repetitions. The volume of solution applied was 2001 L/ha, at a temperature of26°C and relative humidity of 84%, by the use of a manual sprayer, pressured by C02 at 32 lb/in', with six flat nozzles TI 110.02. Phytotoxicity and the control of Brachiaria decumbens were analyzed 6, 12,21 and 31 days after chemical application (DAA).1t was conclued that the species Syagrus oleracea was highly tolerant to the herbicide glyphosate, even at the highest studied dose and the herbicide glyphosate independent1y of the studied dose, was very efficient in the control of young Brachiaria decumbens plants, exerting 100% control.
Weed control in sunflower crop with application of aclonifen isolated or in mixture
The aim of this work was to evaluate the selectivity and the efficacy of ac1onifen, isolated or in mixture with other herbicides, in postemergence weed control in a sunflower crop. The experiment was conducted in 1998/99, at the Experimental Farm ofMaringá State University, Paraná State, using the hybrid Morgan 742. The experimental design was randomized block with nine treatrnents and four replications. The evaluated treatments were: control (with and without hoeing), aclonifen (780 and 900 g/ha), quizalofop-p-ethy (75 g/ha), aclonifen +quizalofop-p-ethy (900 +75 and 900 + 100 g/ha), aclonifen +fomesafen (900 +25 g/ha) and aclonifen +chlorimuron-ethyl (900 + 2.5 g/ha). The treatments were applied when the sunflower plants were in V6 to V8, using a carbon dioxide-pressurized backpack sprayer, with a spray volume of 200 Llha. The mixtures of aclonifen + quizalofop-p-ethyl and the quizalofop-p-ethyl alone were seletive for sunflower and efficient in Cenchrus echinatus control, not differing significantly for the control. Ac1onifen.alone or in mixture with fomesafen, chlorimuron-ethyl and quizalofop-pethyl were efficient in the control of Commelina benghalensis and Portulaca oleracea not showing differences between these treatments and the control. Aclonifen alone or in mixture with fomesafen and chlorimuron-ethyl did not cause visual injury to the sunflower crop. The presence of weeds, especially C. echinatus, hindered the harvest and decreased the sunflower yield up to 50.0%.
Mixtures oftlumioxazin with glyphosate and sulfosate for weed management in citrus
To evaluate the efficacy of flumioxazin mixtures with glyphosate and sulfosate used in handling postemergence in citros, an experiment was conducted in Presidente Castelo Branco, PR, in a 3 year old orange orchard, "Pear" variety. The experimental design was randomized blocks with seventeen treatments and four replicates. The evaluated treatments were: flumioxazin (10, 15,20 and 25 g/ha), flumioxazin + glyphosate (l0+960, 15+960, 20+960, 20+ 1920 and 25+960 glha), flurnioxazin + sulfosate (10+960, 15+960, 20+960, 20+ 1920 and 25+960 g/ha), glyphosate (960 g/ha), sulfosate (960 glha) and check without weed control. The products were sprayed under the crop plants. The weeds present in the area were: Sida rhombifolia (up to 60 em high), Bidens pilosa (up to 50 em high), Richardia brasiliensis (flowering), Digitaria horizontalis (up to 3 tillers) and Brachiaria decumbens (up to 20 tillers). The flumioxazin mixtures with glyphosate and sulfosate, starting from rate of 10+960 g/ha, were efficient in the control of the weeds. The glyphosate and sulfosate alone were efficient in the control of the present species, no significant differences being observed between mixtures starting from 7 days after application (7 DAA). The flumioxazin alone did not provi de adequate control ofthe weeds, but when in mixture with glyphosate and sulfosate presented faster control effect, observed at 3 DAA. For B. decumbens, glyphosate or sulfosate up to 1920 g/ha in mixture with flumioxazin at 20 g/ha provided longer weed control, with few tillers. No chemical treatment visable injured the orange crop.
Efficacy of carfentrazone-ethyl applied in the control ofweeds in no-tíll cotton
The objective was to evaluate the efficacy of the herbicide carfentrazone-ethyl in mixture with glyphosate, in the control of weeds in a no tillage system and to evaluate the tolerance of the cotton crop. The experiment was developed in the period from January to March of2001, in the FEP-UNESP in Selvíria, MS, in soil with a loamy texture. The cultivar of cotton used was 'ITA-90', with 0.90 m of spacing. The experimental design was randomized block with six treatments and four replicates. The treatments were the following: 2,4-D (670 g/ha), flumioxazin (25 g/ha) and carfentrazone-ethyl (20, 25 and 30 g/ha), all with glyphosate and mineral oil (0.5% v/v) and a weed free controI. The application was carried out with a manual pulverizer under constant pressure of 45 Ib/in? (CO), with a bar equipped with four fan type nozzles, spaced 0.5 m apart and spray volume of 250 Llha. The treatments carfentrazone-ethyl (20, 25 and 30 g/ha), 2,4-D (670 g/ha) and flumioxazin (25 g/ha), added to glyphosate (960 g/ha) + mineral oil Assist (0.5% v/v), applied before cotton plantation, were efficient for the control of Commelina benghalensis and Ipomoea nil for the weed control in a no tillage system and selective for cotton plants, for cultivate 'ITA-90' .
Effect ofpropisochlor with and without other herbicides in pre and post-emergence in corn
Two field experiments were carried out in Engenheiro Coelho, SP, to evaluate the selectivity and efficiency of the herbicide propisochlor, alone and in combination with other herbicides, applied in pre and post-emergence in com. A randomized block design was used with four replications inc1uding the following treatments: propisochlor (at 1008, 1080 and 1152 g/ha), propisochlor formulated with atrazine (at 1008/1400, 1080/1400 e 1152/1400 g/ha), and with terbutylazine in tank rnix (at 1008+1800, 1080+ 1800e 1152+ 1800 g/ha), acetochlor at 2688 g/ha, metolachlor at 1250 g/ha, atrazine at 3500 g/ha; terbutylazine at3000 g/ha and controls with and without application products for selectivity and control respectively. The results showed that propisochlor alone and in mixture with atrazine or terbutylazine at any dose controlled efficiently Brachiaria plantaginea, Digitaria horizontalis, Eleusine indica, Amaranthus viridis and Bidens pilosa, up to 45 days with pre application. Propisochlor only in combination with either atrazine or terbutilazine did not have satisfactory post-emergence activity. None of the chemical treatments affected com growth.
Effect of sorghurn straw associated with irnazarnox herbicide on the developrnent of the soybean crop planted in succession
This experiment had the objective of evaluating the effects of grain sorghum, Saara, DK 860 and Ambar hybrids, associated with the imazamox herbicide, applied at O, 15 and 30 g/ha, on soybean (cv. Conquista) growth planted after sorghum desication. Sorghum straw did not affect soybean plant height, above ground dry matter and grain yield. Node number was reduced by DK 860 and Saara straw while these hybrids promoted 11% increase in 100 seed weight. Imazamox caused a decrease in the soybean evaluated parameters with a 8% grain yield reduction. Sorghum hybrids straws and the imazamox herbicide performed as independent factors with no interactive effects on soybean.
Picloram residues and leaching in water in a sugar cane area
The region of Ribeirão Preto, SP, Brazil, is located on the Guarani aquifer, the most important source of ground water in the South Central region of the country. The recharge area of this aquifer is located in the Espraiado watershed. The presence of sandy soi! and a sugar cane crop treated with pesticides makes the aquifer vulnerable to groundwater contamination. The herbicide picloram was among the pesticides used. To study its behavior, a gas chromatography analytical method for residue analysis was developed and picloram was measured during the years of 1996 until 1999. The movement also was evaluated with simulation using the software CMLS-94-"Chemical Movement in Layered Soils". The gas chromatography analytical method resulted in a 98.0% correlation of the area in the graphics and the herbicide concentration, and indicated that it was highly effective. No residue of picloram was detected in water in any year from 1986 to 1989. The simulation model CMLS have indicated the leaching down to maximum depth of 8.2 m for "Areia Quartzosa cinza" (AQ-Cin) sandy soi!, 7.3 m for "Areia Quartzosa rosa" (AQ-Ros) sandy soil and 6.7m for "Areia Quartzosa amarela" (AQ-Ama) sandy soi!, followed by latossols "Latossolos Vermelho-Escuro" ( LE-Col, 5.7 m) and "Latossolos Vermelho-Roxo" (LR-Col, 5.3 m), indicating possibilities of picloram leaching.
Weed control and selectivity of diclosulam as a preemergence soybean herbicide
The present research involved two field experiments. The first one, carried out at Iguaraçu, PR, inc1uded rates of diclosularn (30,35 and 40 g1ha), imazaquin (140 g/ha), flumetsulam (108 g1ha) and a weed-free control were evaluated in a completely randomized block design with four replications. Diclosulam provided efficient control ofthe grass Pennisetum typhoideum up to 42 days after application (DAA), requiring a suplementary postemergence grass herbicide to al\ow suitable control at harvest. In relation to Commelina bengalensis, diclosulam at 30 g1ha provided 89% control at 63 DAA. For broadleaves like Raphanus raphanistrum and Sida rhombifolia, diclosulam provided good control (>97%) even at the lowest rate, being similar or superior in relation to imazaquin and flumetsulam at harvest. Since diclosulam alone did not provide suitable grass control until harvest, in the second experiment the mixture of diclosulam and metolachor was evaluated. Diclosulam, at 25 g/ha, alone or with metolachor (~1200 glha) provided good control (~93%) of C. benghalensis, Euphorbia heterophylla and Desmodium tortuosum, with no significant differences among evaluated combination of rates. It was not possible to evaluate the efficacy of the combined application of diclosulam and metolachor on grass weed control due to absence of infestation.
Efficacy of herbicides in pre and postemergence control of balloonvine (Cardiospermum halicacabum)
Balloonvine (Cardiospermum halicacabum) is distributed throughout South Brazil. Because of size and shape similarities, balloonvine seeds are difficult to separate mechanically from soybean seed and this weed is spreading quickly by contaminated soybean seed. It is tolerant to most herbicides, mainly to contact products and highly infested soybean areas are difficult to harvest. Three experiments were carried out at Embrapa Soybean, Londrina, Paraná State, in order to evaluate balloonvine chemical control with pre and postemergence herbicide applications. Oxyfluorfen (480 g/ha), sulfentrazone (600 g/ha), acetochlor (2304 g/ha), prometryne (1600 g/ha), alachlor (3360 g/ha), and atrazine (2500 g/ha) were efficient on preermergence balloonvine control. Glyphosate plus carfentrazone (720 g/ha a.e. + 12 g/ha), glyphosate plus flumioxazin (720 g/ha a.e. + 25 g/ha), glyphosate plus lactofen (720 g/ha a.e. + 144 g/ha) and glufosinate-ammonium (400 g/ha) were efficient on postemergence balloonvine control.
Imazethapyr selectivity for three common bean genotypes
With the purpose of evaluating the selectivity of the imazethapyr herbicide at different dosages to common bean genotypes, an experiment was conducted in greenhouse at the Department of Agriculture of the Universidade Federal de Lavras, from April, 20 to August 4, 2001. The experimental design was a completely randomized with four replications in a 3x4 factorial arrangement, i.e., three common bean genotypes (Pérola, CII-I02 and Ouro Negro) and four dosages of the imazethapyr herbicide (O, 50, 100 and 150 g/ha). The phytotoxicity, plant height and dry weight of the aerial parts, pod number per plant, seed number per pod and one hundred seed weight were evaluated. The bean genotypes showed differential behavior to herbicide dosages. Pérola and Ouro Negro cultivars showed the highest tolerancy to imazethapyr and the CIl-l 02 lineage, on the other hand, showed high sensibility to the herbicide. Nevertheless, the herbicide did not interfere with the plant height ofthe genotype, but the phytotoxicity symptoms and yield losses showed linear increase with increasing dosages of imazethapyr. At 21 days afie r the herbicide application, ali the visible symptoms on bean plants were reverted. The lineage ClI-102 grain yield decreased 37% with the increasing dosages ofthe herbicide.
Efficacy and selectivity of cloransulam-methyl in postemergence control of weeds in soybean
An experiment was carried out on a "Cerrado" oxisol with a loamy texture during 1996/97. The objective of present work was to evaluate the selectivity and efficacy of cloransulam-methyl, alone or tank mixed with lactofen, applied postemergence on soybean (cv. Doko) in controlling broadleafweeds. The experimental design was a complete randomized block with seven treatrnents and four replications. The treatrnents were: cloransulam-methyl (20, 30 and 40 g/ha), chloransulammethyl+ lactofen (30+96 glha), chlorimuron-ethyl+lactofen (12.5+96.0 g/ha) and control with and without weeds. Cloransulammethyl, independent ofthe used dose, provided efficient control of Aeanthospermun hispidum and Blainvillea latifolia and in mixture with lactofen presented efficient control of Nieandra physaloides. The tank misture chlorimuron-ethyl+lactofen presented efficient control of Aeanthospermun hispidum, Blainvillea latifolia and Nieandra physaloides. Significant differences were not observed among the productivity with the chemical treatrnents, but reduced productivity ofthe control without weed cIearance and with lower dose of cloransulam-methyl in 48% and 35% in relation to the weed free control, respectively. The application of the treatrnents did not affect significantly the initial and final population, height of the plant and nor height of insert of the first bean. The index of mechanical harvesting with the chemical treatrnents was excellent, except for plots which received cloransulam-rnethyl at 20 glha. All the tested treatments were selective for soybean.
Herbicide efficacy and selectivity for burn-down and residual weed control in soybeans
The effects of chlorimuron-ethyl at the rate of 10.0 g/ha applied alone and as tank mixture or in sequence with glyphosate, and diclosulam at the rate of35.2 g/ha plus glyphosate, as tank mixture, were studied for burn-down and residual control of Brachiaria p/antaginea (Link) Hitchc. and Bidens pilosa L. and for their safety to soybean in no-til\. The study was conducted during the 2001/2002 growing season at the National Wheat Research Center of Embrapa in Passo Fundo, RS, Brazil, on a medium-textured soi!. The experimental design was a completely randomized block with four replications. Ali treatments were effective in desiccating B. pilosa. Chlorimuron-ethyl and diclosulam, applied alone, in mixture or in sequence with glyphosate provided season long weed control. No crop injury was observed and there was no effect on grain yield.
Postemergence broadleaf herbicide selectivity in cassava
The main management problem in the cassava crop in due to interference by weeds, where they bring about root yield reductions. Inexistence of selective postemergence herbicides, makes weed control only possible with preemergence herbicides or through hand hoeing. The objective of this research was to evaluate broadleaf herbicide selectivity when applied postemerg.ence on cassava plants. An experiment was carried out at University of Rio Grande do Sul, Brazil, using 10-liter volume pots, where four cassava cuttings were planted. The experimental design used was a completely randomized one, with five replications. The tested herbicides were: acifluorfen, bentazon, fomesafen, byspiribac, chlorimuron, imazethapyr, nicosulfuron and linuron. The variables evaluated were herbicide injury at 4, 8, 14 and 28 days after treatment application (DAT), and shoot dry weight at 14 and 18 DAT. Nicosulfuron was selective for cassava when applied at an early growth stage, significa~tly different from the other treatments as far as biomass production is concemed, constituting a promising option for selective broadleafweed control in this crop.
Effect of the sequential application of glyphosate in Commelina benghalensis and Commelina dif/usa control in coffee crop
Different strategies to reduce C. benghalens is and C. diffusa tolerance to glyphosate were studied in two field experiments in coffee. The effect of glyphosate sequential application at increasing doses and comparing the glyphosate formulations, glyphosate SA (isopropilamine salt) and glyphosate WG (ammonium salt) in the control ofthese species and the respective phytotoxicity was evaluated. No significant difference were foundamong formulations of glyphosate SA (2160 g/ha a.e.) and glyphosate WG (2160 g/ha a.e.), in C. diffusa and C. benghalensis controI. The sequential application of glyphosate WG at 1440 and 1080 g/ha a.e., with the second application 21 days after the first, was efficient for C. diffusa and C. benghalensis control, from 30 to 100 days after application (DAA). The tank mixture glyphosate SA+2,4-D, at 1080 + 1005 g/ha a.e., and the mixture diuron/paraquat at 300/600 g/ha resulted in accentuated phytotoxicity until 60 DAA. However, glyphosate SA and glyphosate WG in sequential application or in unique application, in the studied doses, caused accentuated phytotoxicity until 30 DAA, tuming to light phytotoxicity in the folIowing evaluations.
Control of Euphorbia dentata with different formulations of glyphosate in transgenic soybean resistant to glyphosate
Euphorbia dentata is a highly competitive and difficult to control weed in soybean crops in the central are a of Buenos Aires Province, Argentina. Development of transgenic soybean resistant to glyphosate (GR) allows exploration of new techniques of chemical weed control, mainly where the herbicides traditionalJy used are inefficient. The objetive of this . research was to evaluate the effectiveness of Euphorbia dentata control with different formulations of glyphosate in soybean GR. The trial was carried out in Azul district, province of Buenos Aires, during the 99/00 and 0010 I agricultural seasons using soybean cv. AX 4100 GR and with an infestation of E. dentata of 135 pl/m" The treatments consisted in the application of three doses of glyphosate (720, 1260 and 1620 g/ha acid equivalent) using three commercial formulations of the same active ingredient available in Argentina: formulation 1 (isopropylanmine salt SL 48%, Ru) , formulation 2 (monoamonic salt WG 74,7%, Ru_M), formulation 3 (isopropylamine salt with transorb technology SL 48%, Ru_F), weeded control and non weeded, where the weeds were removed manually. The sprayings were performed when the weed had developed 4 true leaves and with a volume equivalent to 100 Llha, using a CO2 manual equipment. Weed control and crop yield were evaluated. Ali the glyphosate formulations obtained high levels of control (more than 85 %) with the use ofthe maximum doses but did not differ significantly among themselves. The isopropylamine salt formulation (Ru_F) showed high efficiency even with a doses of 720 g/ha, whereas the other formulations only obtained partial controls (50 and 60%). Concerning yield, ali the treatments differed significantly from the weeded control whose productivity was about 2500 kglha. The treatments which obtained the maximum levels of control did not differ significantly from the control without weeds which had a yield of 4000 kg/ha.
Efficacy of flumioxazin applied alone and in a tank mix with diuron or diclosulam added with different adjuvants in cotton
A field experiment was carried out in Itapira, SP, to evaluate the selectivity and efficiency ofthe herbicide flumioxazin alone or in a tank mix with diuron or diclosulam applied in post-ernergence to weed control in cotton cv. Coodetec 40 I,with two different mineral oils. The experimental design was a randomized block with four replications and the foIlowing treatments: flumioxazin (30 g/ha), flumioxazin+diuron (25+800 and 25+ 1,000 g/ha), flumioxazin+diclosulam (25+30 and 25+35 g/ha), MSMA+diuron (1,800+1,000 g/ha) with standard treatrnent and controls with and without weeds. The adjuvants used were Assist at 0,5% v/v and Triomax at 0,25% v/v. The results showed that flumioxazin herbicide alone or in a tank mix with diuron or diclosulam have controIled efficiently Commelina benghalensis L., lpomoea grandifolia (Dammer) O'Don. and Raphanus raphanistrum L. until 39 days afie r the post-emergence application. The two adjuvants had no significant effect on the results. None of the chemical treatments affected the cotton plant development or yield.
Diquat defoliation effieiency on pre harvest bean crop
The best time to harvest the bean crop is after the occurrence ofphysiological maturation, when the seeds vigour, the gemination and the weight of dry matter are high. To carry out mechanical harvesting at this moment is difficult because a high number of leaves is still green. Besides, the mechanical injuries may be inflicted on the seeds. The use of defoliation can minimize this occurrence, promoting uniformity of plants maturity at harvest with grains maintaining low moisture. ln order to evaluate the agronomic efficiency on defoliation of diquat at pre harvest ofthe bean crop, an experiment was carried out in Ponta Grossa (PR), during 1999/00, using the cultivar FT Nobre. The experimental design was a randomised block with six treatments and four replications. The following treatments were tested with applications 14 days before harvesting: diquat (200,300,400 and 500 g1ha), ammonium-glufosinate (400 g1ha) and controI. Diquat at doses equal to or higher than 300 gI ha and ammonium-glufosinate showed efficiency in the control (or defoliation) of Bidens pilosa, Eleusine indica and Digitaria horizontalis. AlI treatments showed efficiency for plant defoliation after four days of application, indicating the possibility of anticipation ofharvest. Differences in seed germination, vigour, health and even on the yield among the treatments, including the control were not observed.
Efficacy and selectivity of acetochlor isolated and mixed with atrazine, in corn
This experiment was intended to evaluate the selectivity to maize hybrid AG 30 I O and efficiency of acetochlor herbicide alone and tank mixture with atrazine applied in preemergence to control Cenchrus echinatus, Brachiaria plantaginea, Digitaria horizontalis, lndigofera hirsuta, Bidens pilosa and lpomea grandifolia . The experiment was conducted in laboticabal, SP, on red oxissol. Treatrnents inc1ued acetochlor 2.52,3.36 and 4.20 kg!ha, acetochlor/atrazine 3.76, 4.38 and 5.0 I kglha, and the commercial pattem atrazine/metolachlor at the rate of 3.50 kg!ha, besides controls with and without weeds. The herbicides were applied with costal sprayer, to constant pressure (2.8 kgf/cm-), with four nozzles XR 11002 with equivalent spray volume of200 Llha. The best results were obtained with metolachlor/atrazine 3.50 kg!ha and with two rates of acetochlor/ atrazine (4.38 and 5.0 I kg!ha) for the weed control. Despite the slight reduction at the beginning of growth on maize treated with acetochlor, they recovered quickly making the utilization of the acetochlor on the tested hybrid a possibility.
Efficacy of burndown herbicides in Richardia brasiliensis control in no-tillage systems of common bean crop
No-tillage systems, characterized by presence of straw on soil surface, provoke some alteration in weed population dynamics, such as a reduction in annual species and increase in perennial species, as well as the appearence of weeds that are hard to control , such as Richardia brasiliensis. The objective of the present work was to evaluate the efficiency of burndown herbicides in Richardia brasiliensis control and their effect on yield and yield components in beans grown under no-tillage systems. The experimental design was a complete randomized block with six treatments and four replications. The treatments were: sulfosate (878 g/ha), glyphosate SC (960 g/ha), sequential application of sulfosate and paraquat/diuron (627 and 200/100 g/ha), glyphosate WG (958 g/ha) and glyphosate+2,4-D (720+720 g/ha). The percentage of control in bean sowing, at 7 days after the sowing (DAS) and at 18 DAS were evaluated. The results at sowing were defficient, lower than 40% for ali treatments, while at 7 DAS was 72% for sulfosate and at 18 DAS there was no difference between sulfosate and glyphosate, with 80% and 75% of control, respectively. The best bean yields were with sulfosate and glyphosate, however there was no significant difference between them. Regarding yield components, the best results for average number of pods per plant was achieved with sulfosate and for the others components there was no difference between treatments.
Efficacy of herbicides in postemergence control of weeds in corn crop
The objective of this research was to evaluate the agronomic efficiency of herbicides applied as a postemergence treatment on the control of weeds and to evaluate the tolerance of the treatments for com. The experiment was developed during the period from december/OO to april/O 1, at FEP-UNESP at Selvíria, Mato Grosso do Sul, Brasil. The experiment was carried out in a conventional system and the hybrid com used was 'Master ' at a spacing of 0.9 m between rows with 5.4 seeds per meter. The experimental design was a randomized complete block, with 9 treatments and 4 replicates with 5 !ines of the crop. Plot size was 4.5 x 5.0 m. The treatments were: foramsulfuron (35.0 and 45.5 g/ha), foramsulfuronliodosulfuronmethyl- sodium (36.0/2.4 and 45.0/3.0 g/ha), nicosulfuron (50.0 g/ha), foramsulfuron- atrazine (35.0+1000.0 and 45.0+1000.0 g/ha) and a weed-free and a weeded control. The applications were accomplished with a manual sprayer and constant pressure (COz) of 45 lb/pol-, equipped with four Teejet 110.03 XR nozzles, spaced at 0.5 m and volume of 250 I/ha. The treatments were selective for the crop. The treatments foramsulfuron (45.5 g/ha), foramsulfuronliodosulfuron-methyl-sodium (36.0/2.4 and 45.0/3.0 g/ha) and foramsulfuroru-atrazine (45.0+1000.0 g/ha) were efficient in the control of Bidens pilosa, Commelina benghalensis and Digitaria horizontalis. The treatments foramsulfuron (35.0 g/ha), nicosulfuron (50.0 g/ ha) and forarnsulfuron+atrazine (35.0+ 1000.0 g/ha) were efficient in the control of B. pilosa and C. benghalensis.
Effect of seed size on dry bean tolerance to s-metolachlor under low temperature conditions
The objective of the work was evaluate the potential phytotoxic effects of s-metolachlor herbicide on different sizes of seeds of a single bean variety cultivar belonging to a same lot, in low temperature conditions. The experiment was carried out in a growth chamber with 12 hours photofase, 16/13 ± 3°C (day/night) temperature (until plant emergence) and 300 umol of photosynthetically active radiation (PAR)/m2 s. The cultivar used was Pérola, belonging to the Carioca group. The treatments included the combination of three seed sizes (sieves 14, 18 and 21) and four s-metolachlor doses (0.00, 0.96, 2.88 and 4.80 kg/ha), totalling 12 treatments. The herbicide was applied preemergence, the following evaluations being carried out: 1) time (days) until the emergence of 75% of the seedlings; 2) number of emerged plant in the crop; 3) visual toxicity; 4) final plant height; 5) final dry matter of the aerial part; and 6) final dry matter of the roots. The larger the seed size the most retarded was the emergence of the bean plant. The seed sizes together with the s-metolachlor levels did not interfere in the number of emerged plants. The increase in the s-metolachlor doses caused higher reduction in the dry matter of the aerial part of the bean plants than the roots, for ali the seeds sizes. Plants from larger seeds presented high herbicide toxicity levels, reaching 71% of symptoms at the highest s-metolachlor dose (4,80 kg/ha) and largest seed size (sieve 21), though no dry matter reduction was observed.
Control of Panicum maximum in sugar cane with preemergence herbicides
The major problem with the sugar cane crop is weed competition, specially Panicum maximum Jacq., which is a very agressive plant. The trial was carried out at Usina São Carlos (a sugar will), in Jaboticabal-SP, during 1998/1999 aiming to study imazapyr and imazapic herbicides, sprayed alone in preemergence, or imazapic in mixture with pendimethalin, for P maximum control. The experimental design was a randomized block with nine treatments and four replications. The treatments were: controls (with and without weeds), imazapic (73.5 and 98 g/ha), imazapyr (122 and 147 g/ha): imazapic+pendimethalin (50+ 1000 and 60+ 1200 g/ha) and pendimethalin (1200 g/ha) at preemergence. The herbicides were applied with a manual sprayer, with constant pressure of 2.8 kg/crrf and jet nozzles with descontinuous deposition (DG11002), using 250 Ilha of the herbicide solution. The sugar-cane variety used was RB 72454. The best preemergence weed control was observed with imazapic+pendimethalim in ali treatments 126 days after application. The postemergence treatment cannot be used because they caused high crop toxicity. The herbicide mixture (imazapic+pendimethalin) showed low efficiency in ali tested treatments.
Influence of simulated rain on the efficacy of different formulations and doses of glyphosate
The effects of simulated rainfall on the performance of different formulations and doses of glyphosate in the control of Brachiaria plantaginea (Link) Hitchc. were studied under field conditions. The experimental design used was that of a split-block in strips. The strips consisted of the irrigation factor. Formulation and doses were arranged in a factorial arrangement, with four replications. Plots measured 2.5 m x 4.0 m. The irrigation factor consisted of a simulated rainfalI of 20 mm applied at different timings (l, 2, 4 and 24 hours after treatment application) which was carried-out using a system of sprinklers. Rainfall simulated less than 4 hours after spraying the products reduced the phytotoxicity of the ammonium salt formulated as water auto-dispersible granules (WG) to a greater extent than that of the potassium and isopropylamine salts formulated as soluble concentrate (SC) when alI compounds were applied at the rate of 360 g/ha acid equivalent. Higher rates of glyphosate reduced the negative rainfall effect. The efficiency of the compound was affected by the type of salt and formulation. The isopropylamine and the potassium salts both as SC formulation, presented daily control rates higher than the isopropylamine as WG formulation. The final control of B. plantaginea was also affected by the formulation; both the isopropylamine salt and the potassium salt formulated as SC showed control rates higher than the ammonium salt formulated as WG. In conc1usion, glyphosate efficiency is determined by its salt type, formulation, rate, and time interval between its application and rainfall. These factors affect glyphosate absorption and translocation determining the final controllevel of the studied species.
Sugar cane tolerance to sequential application of nematicides and herbicides
A field experiment was carried out in a sandy soil (85 % of sand) aiming at studying herbicide/nematicide interaction in sugar cane. Terbufos and carbofuran, both applied at 3000 g/ha in the furrow at planting and the herbicides oxyfluorfen--ametryne (480+ 1500 g/ha), oxyfluorfen+diuron (480+2400 g/ha) and thiazopyr+ametryn (360+ 1500 g/ha) were studied. The herbicides were applied before emergence of the sugar cane plants, with a CO2 knapsack sprayer, equipped with 6 nozzles Teejet DO 80.02. The experimental design was a completely randomized block design in a factorial 3 x 5 arrangement, with four replications. The nematicides did not show any interaction with the herbicides. Carbofuran was better than terbufós, producing higher sugarcane yield. Thiazopyr + ametryn showed the most severe phytotoxic effects until 123 DAA (days after application). A tank mixture oxyfluorfen + ametryn and oxyfluorfen+diuron were the most selective products for the sugarcane plants. Sugarcane yield was not affected by any of the applied herbicides.
Efficacy and selectivity of 2,4-D applied at different rates, growth stages and formulations in paddy rice
An experiment was carried out at Epagri, in Itajaí, Santa Catarina State (26°56'35"S and 48°45'37"W), during 1996/ 97 and 1997/98 growing seasons, to evaluate the efficacy and selectivity of 2,4-D herbicide at four rates, two times of application and two formulations, in infested rice. Herbicides were applied postemergence, with rice plants at the 3-4 leaf stage, and late postemergence, 38-39 days after planting. Herbicide formulations and rates evaluated were: 2,4-D amine at 200,400,800 and 1200 g/ha a.e. (acid equivalent) and ester at 56, 112,224 and 336 g/ha a.e. Overall results showed that higher 2,4-D rates of both formulations at both application timings, injured rice. However, crop injury did not increase spikelet sterility because the rice cultivar was a late season variety and lhe second application was carried out at least 30 days before panicle differentiation. Herbicide 2,4-D, ester or amine, applied postemergence, at low rates (100 g/ha a.e. of ester formulation or 200 g/ha a.e. of amine formulation), controlled Fimbristylis miliacea, Ludwigia longifolia, and L. octovalvis. Heteranthera reniformis was less sensitive to 2,4-D, and higher rates were required for good control. These results suggest that 2,4-D application in rice should be carried out before tillering because, in such conditions, even low rates ofthe herbicide would provi de good broadleaf and sedge control, besides minimizing crop injury.
Chemical weed control in areas of no-till cassava
The aim of this work was to evaluate the selectivity of some pre and postemergence herbicides on cassava, as well as their efficiency to control the weeds Avena sativa, Bidens pilosa, Commelina benghalensis, Raphanus sativus and Sida rhombifolia. The field trial was carried out in no-till areas, in Araruna, northwestern Paraná State. Although some herbicides provided outstanding results either in relation to weed control or crop selectivity, when both aspects were taken into consideration, the best results were achieved with arnetryne-i-clornazone (1.50+ 1.00 kg/ha) and ametryne--diuron (0.62+0.96 kg/ha), both applied postemergence of weeds, when 5 to 10% of cassava sprouts had already emerged from the soil.
Efficacy and selectivity of trifloxysulfuron-sodium/ametryne in the control of weeds in sugar cane fields
A trial was carried out in a sugar cane field in Santa Helena County, Goias State, Brazil, during the 1999/2000 growing season. The objectives were to evaluate the agronomic efficiency of a misture of trifloxysulfuron-sodium/arnetryne in the control of weeds and to evaluate the selectivity for sugar cane. The experimental design was a completely randomized block with four replications and eight treatments. The treatments were as follows: cleaned and noncleaned plots, trifloxysulfuronsodiurnJametryne (32/1280, 37/1463 and 42/1646 g/ha), trifluxysulfuron-sodium+ametryne (tank mixture), at 37+ 1500 g/ ha, hexazinone/diuron (330/1170 g/ha) and trifluxysulfuron-sodiurn (22 g/ha). The herbicides were applied at postemergence, with the broadleaf weeds at the 4 to 61eaf stage and the grasses at 2 to 3 stem stage. Acanthospermum hispidum, Alternanthera tenella, Chamaesyce hirta and Digitaria horizontalis were effectively controlled with trifloxysulfuron-sodium/ametryne at all studied rates, trifloxyxulfuron-sodium+ametryne (tank mixture) at 37+ 1500 g/ha, and hexazinone/diuron (33011170 g/ ha). Trifloxysulfuron-sodium (22 g/ha) showed very low control of Digitaria horizontalis as well as an efficient control of broadleaf weeds. All herbicide doses were selective for sugar cane cv. RB 84-5257. There were no statistical differences for sugar cane plant height, new stem formation and yield, although the control, where weeds were not cut, presented a 5,4% reduction in yield compared to the control where it was not c\eaned.
Dose-response curves of a resistant Brachiaria plantaginea biotype to ACCase inhibitor herbicides
The development of a Brachiaria plantaginea resistant biotype to ACCase inhibitor herbicides has occurred in several soyabean production areas in Brazil, especially in Paraná State. However, little research has been conducted in order to prove scientifically the resistance using dose-response curves. In order to draw dose-response curves and determine GRso and GRso of a suspected 8. plantaginea biotype, herbicides of the chemical groups ariloxyphenoxypropionic acid (haloxyfop-rnethyl, quizalofop-p-ethyl, fluazifop-p-butil and fenoxaprop-p-ethyl) and cyclohexanodiones (sethoxydim, clethodim and butroxydim) were sprayed at rates of 0.1, 1.0, 10 and 100 times the recommended rate. The experiment was installed in the greenhouse of the Plant Production Department of USPIESALQ, in 500 ml plastic pots. The herbicides were sprayed at postemergence when the weed was at 2 to 3 shoot stage. The Brachiaria plantaginea biotype studied showed cross resistance to both ACCase inhibitor herbicides; however, the degree of resistance varied among the individual herbicides.
Efficacy of herbicides in the control of weeds in no-till corn
The experiment was conducted in 1999/00, in the FEP-FEIS-UNESP, Selvíria-MS, in soil with a loamy texture. The objective was to evaluate the efficacy ofthe herbicide carfentrazone-ethyl in mixture with glyphosate, for the control ofweeds in a no tillage system, and to evaluate the tolerance ofthe crop. The com used was 'CO-32'. The experimental design was a randomized block with seven treatments and four replications. The chemical treatments were the following: 2,4-0 (670 g/ ha), flumioxazin (25 g/ha) and carfentrazone-ethyl (15, 20, 25 and 30 g/ha). In ali treatments glyphosate (720 g/ha acid equivalent) and mineral oil Assist at 0,5% v/v was added. A treatment with no weed control was also included. The efficacy ofthe treatments was evaluated on the weed control and crop yield. It was observed that the treatments are highly selective for the com crop. The treatment with the carfentazone-ethyl, at 20, 25 and 30 g/ha, is efficient for the control of Commelina benghalensis and Bidens pilosa. At 15 g/ha, carfentrazone contrais B. pilosa. The treatment with 2,4-0 is efficient in the control of C. benghalensis and B. pilosa. The treatment with flumioxazin is efficient in the contrai of B. pilosa. It was also observed that weed interference reduced the com yield in 96%, in relation to the average of the treatments with chemical control.
Chemical control of Cissampelos glaberrima
The aim of this study was to find a chemical alternative for the control of C. g/aberrima, a weed that has became a serious problem in sugar cane plantations. The post emergent herbicides tested included: glyphosate, by itself and mixed with carfentrazone or sulfentrazone, metribuzin, 2,4-D + diuron, acetochlor, ametryne and oxyfluorfen mixed with diuron and acetochlor. In preemergence, oxytluorfen mixed with diuron, 2,4-D/picloram, clomazone, imazapyr, carfentrazone and sulfentrazone, tebuthiuron, 2,4-D/picloram, clomazone mixed with imazapyr, and diuron/hexazinone mixed with MSMA were tested at recommended rates. A third trial was setup under semi controlled conditions aiming at a pre emergence controI of this plant. A PVC cylindrical container containing 42 I of soil was used. The rhizomes were placed at two differents depths: 30 and 55 em, In relation to postemergence herbicide treatments only oxyfluorfen mixed with acetochlor showed good control during the first 30 days after application, after which this treatment started to lose effect. The pre emergent treatments with 2,4-D/picloram and tebuthiuron showed the best control over 90 days and the treatments with imazapyr mixed with oxyfluorfen and clomazone resulted in an excellent control during 60 days in preemergence. The treatment with 2,4-D/picloram did not cause toxicity to the crop. None ofthe preemergence treatments killed the rhizomes at 55 em depth, but 2,4-D/picloram caused death ofthe new shoots, this being the most promising herbicide to control this weed.
Sequential application of burndown herbicides in the establishment of no-tillage systems in common bean
The sequential application ofherbicides at pre-planting can be used as a strategy to reduce the effect of weed competition with bean plants through the elimination of the first flushes of emergence of weeds. The objective of this research was to evaluate the advantages of sequential application ofburndown herbicides in beans grown under no-tillage, with the elimination of first emergance flushes of weeds prior to planting, and their impacts on the effectiveness of post-emergence herbicides. The experimental design used was randomized blocks with four replications and the treatments in the main plots consisted of bumdown herbicides: sulfosate (396 g/ha a.e.) at 20 days before planting with a supplementary treatment of paraquat (200 g/ha), paraquat + diuron (200 + 100 g/ha), diquat (200 g/ha), paraquat/diuron + diquat (100/50 + 100 g/ha) at planting (sequential application of bumdown - SAB); application of sulfosate + 2,4 0(594 + 720 g/ha a.e.) 10 days before planting (only one bumdown application - OBA) and an untreated control. The sub-plots consisted of post-emergence herbicides: fomesafen + fluazifop-p-butyl (100 + 80 g a.i. ha'), (fomesafen + fluazifop-p-butyl) + bentazon « I00 + 80) + 420 g a.i. ha') and an untreated control was also included. At 7 days after planting there was no difference between the SAB and OBA, both which controlled up to 85% ofthe weeds. There was no difference between the two post-emergence herbicides, both with effectiveness in the control of weeds up to 98%, independent of applícation ofbumdown herbicides. At the time of planting, the plots with OBA had lower weed density (71 %) than the plots treated with SAB. In addition, at the time of postemergence herbicide application, the density ofweeds was lower (41 %) with the SAB than the OBA plots, with a more favorable stage of development ofweeds for the post-emergence control.
Efficacy oftrifluralin formulations and doses in soybean
The objective ofthis study was to evaluate the efficacy of different formulations oftrifluralin to control grass weeds in soybean (cv. Garimpo) on a Red-Yellow Latossolo, with a sandy texture, in Uberaba, MG, Brazil. The treatments were: trifluran WG (500 g/l) at 750 and 1000 g/ha, trifluralin EC (600 g/I) at 720 g/ha and trifluralin EC (445 g/l) at 667 g/ha, as well as an unweeded and a weeded control. The experimental design was a complete randomized block with four replications. The two trifluralin formulations (WG and EC) controlled 80-90% of Brachiaria decumbens and B. p/antaginea. The agronomic characteristics of soybean such as productivity, plant height, first pod insertion, seed weight, and mechanical harvest indice, were not affected by the formulations nor doses of trifluralin. The' herbicide also did not provoke toxicity to the soybean. However, a slight superiority of the EC formulation in the early control of Brachiaria decumbens (15 days after herbicide application) and late control (45 days after herbicide application) of B. plantaginea was noticed.
Productivity and physiological quality of soybean seed originated from plants desiccated by carfentrazone-ethyl
The purpose of the experiment was to evaluate the application of carfentrazone herbicide as desiccant on a soybean crop and its effect on soybean seed yield and physiological quality. A randomized complete block design with 10 treatments and 4 replications was set up. The experimental plot consisted of 8 rows, each 5 m long. The following treatments were applied to plants of the FT-Jatobá cultivar: I) control, without desiccant; 2) carfentrazone (50 g/ha); 3) carfentrazone (70 g/ ha); 4) carfentrazone + MSMA (50 + 480 g/ha); 5) carfentrazone + MSMA (60 + 408 g/ha); 6) carfentrazone + MSMA (70 + 336 g/ha); 7) MSMA (1200 g/ha); 8) amonium gluphosynato (500 g/ha); 9) paraquat (400 g/ha) and 10) diuron / paraquat (250 / 500 g/ha). The desiccants were applied with a carbon dioxide-pressurized backpack sprayer, between R6 and R7 soybean development stages, the seeds having between 32 and 40% humidity. The following characteristics were analyzed: w~ter conten~, standard germination, first count of standard germination, accelerated aging, water content after accelerated ~gl~g.' electr~c condutivity and seed yield. It was concluded that carfentrazone applied as a desiccant on soybean crops, individually m dos~ges of 50 and 70 glha or with MSMA at dosages of 50 + 480, 60 + 408 and 70 + 336 glha, did not affect the soybean seed yield and their physiological quality. More studies on carfentrazone-ethyl as a desiccant of soybean is necessary.
Evaluation of the efficacy of glyphosate+carfentrazone-ethyl on desiccation of weeds in soybean
A test was conducted in Chapadão do Céu city, state ofGoiás, to evaluate the biological efficacy ofa tank mixture of glyphosate + carfentrazone-ethyl, comparing it with glyphosate + 2,4-0 on the desiccation ofweeds in a soybean plantation. The experimental design adopted was that ofrandom blocks, with four replications and nine treatments, as follows: glyphosate (720 and 1080 g/ha), glyphosate + 2,4 -O (720+670 and 1080+402 g/ha), glyphosate + carfentrazone-ethyl (360+30, 720 + 25 and 1080 + 20 g/haj.and 2,4-D (670 g/ha), as wel! as a control treatment. The vegetative cover ofthe are a at application was 95%, with a higher frequency of capim-colchão (Digitaria horizontalis), picão-preto (Bidens pilosa), guanxuma-preta (Sida rhombifolia), guanxuma-branca (Sida cardifolia) and. in lower numbers, erva-quente (Spermacoce latifolia). The evaluations were carried out at 8, 18 and 28 days after treatrnent, adopting a percentual scale in which zero meant no control and one hundred corresponded to total control. The combination ofglyphosate + carfentrazone-ethyl (720+25 and 1080+20 g/ha) caused efficient control of D. horizontalis, B. pilosa, S. cordifolia, S. rhombifolia and Spermacoce latifolia. Glyphosate -i- 2,4-D (720+670 and 1080+402 g/ha), caused efficient control ofweeds, except Spermacoce latifolia. which was satisfactorily control!ed. Glyphosate (720 and 1080 g/ha) was efficient for weed control, except Spermacoce latifolia, whose control was deficient. The hercicide 2,4- D (670 g/ha), caused low levei control of D. horizontalis, satisfactory control of Spermacoce latifolia and efficient control of the other species. A substitution ofthe herbicide 2,4-D by carfentrazone-ethyl in cornbination with glyphosate is possible for the desiccation of weeds in no till plantations.
Purple nutsedge (Cyperus rotundus L.) control in sugar-cane crop with imazapic herbicide, isolated or in mixture whith pendimethalin
The major problem with the sugar cane crop is weed competition, especially purple nutsedge which is a very agressive plant. The trial was carried out at Usina São Carlos (a sugar mill), Jaboticabal-Sl', during the summer period (1999/2000) aiming to study the effect of imazapic herbicide on purple nutsedge control, sprayed at pre and postemergence, alone or in mixture with pendimethalin. The experimental design was randomized blocks with thirteen treatments and four replications. The treatments were: controls (with and without weeds), imazapic herbicide (13.5,98.0, 122.5 and 147.0 g/ha), imazapic + pendimethalin (50+ I000, 60+ 1200, 70+ 1400 g/ha), in preemergence application. Postemergence treatments were imazapic, at the same doses, with surfactant 0.15% v/v. The herbicide was applied with a manual sprayer, with a constant pressure of 2,8 kg/cm- and jet nozzles with descontinuous deposition (XR II 002), using the equivalent of 250 Ilha of the herbicide solution. The sugar cane variety used was RB 855536. The best pre-emergence weed control (96%) was observed with 147 g/ha of ~mazapic at 27 days afte~ appl~cation .. The P?stemergence applications cannot be used because they caused high toxicity 111 the culture. The herbicide mixture (imazapic+pendimethalin) showed low efficacy for ali tested treatments.
Efficacy of carfentrazone-ethyl and glyphosate mixtures on control of Commelina benghalensis in coffee crop (Coffea arabica)
The objective of this research was to evaluate the efficacy in control of Commefina benghalensis using mixtures of carfentrazone-ethyl and glyphosate herbicides on the coffee crop. The experiment was carried out in São José Farm, Garça- SP, Brazil. The treatrnents were: postemergence application of carfentrazone-ethyl + glyphosate (10+ 1200, 15+ 1200,20+ 1200, 25+1200,30+1200,40+1200 and 50+1200 g/ha), 2,4-0 (2680 g/ha), glyphosate (1200 g/ha) and an untreated control. Experimental design was a randomized complete block with three replications. The carfentrazone-ethyl mixture with glyphosate herbicide was efficient in the control of Commelina benghalensis starting with doses greater than or equal to 30 g/ha. The maximum dose of carfentrazone-ethyl (50 g/ha) mixture and glyphosate herbicides were fully efficient in control of the weed, up to 15 days after application on the coffee crop. The glyphosate herbicide control on the weed species was more efficient, presenting a faster dessication period, when used with increasing doses of carfentrazone herbicide above 25 g/ha, when compared with glyphosate alone. The evaluated herbicides and mixtures did not present toxicity to the coffee leaves.
Selectivity of herbicides applied in pre and postemergence of perennial peanut (Arachis pintoi)
Two experiments were installed under greenhouse conditions at Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba - SP, Brazil, in order to evaluate the dry biomass production and toxicity due to pre and postemergence herbicides on the perennial cover crop Arachis pintoi. The experiment was conducted in randomized complete blocks with four replicates. The herbicides sprayed in preemergence conditions (one experiment) were trifluralin at 0.25 kg/ha, diuron at 1.5 kgi ha, oxyfluorfen at 0.6 kg/ha, atrazine at 2.0 kg/ha, metolachlor at 2.88 kg/ha, and a control plot without herbicide application. In the experiment with postemergence herbicides, the treatments were fluazifop-p-butyl at 0.25 kg/ha, MSMA at 1.92 kg/ha, glyphosate at 0.72 kglha, ammonium glufosinate at 0.40 kg/ha, sulfosate at 0.96 kg/ha and a control plot without herbicide application. The evaluations were carried out at 30, 45, 60 and 75 days after pre-emergence herbicide treatments, and 7, 14, 21 and 28 days after post-ernergence herbicide treatments. The results showed that atrazine, glyphosate, arnmonium- glufosinate and sulfosate, at the sprayed rates, should not be applied on the cover crop; however, the herbicides trifluralin, oxyfluorfen and metolachlor can be sprayed at recommended crop rates, with some effects on the development of A. pintoi. Diuron, fluazifop-p-butyl and MSMA are fully selective to the green manure. It can also be concluded from the experiment, that, in general, pre-ernergence treatments are more selective to A. pintoi than post-emergence herbicides, causing lower toxicity and dry biomass reduction, when compared to post-ernergence herbicides.
Efficacy of herbicide mixtures in the control of an Euphorbia heteropylla biotype tolerant to acetolactate synthase in soybean
An experiment was conducted under field conditions to study the efficacy of the herbicides lactofen, irnazethapyr, chlorimuron-ethyl, cloransulam-metil, oxasulfuron, and flumiclorac-pentil, alone and in combination with lactofen, for E. heterophylla control in soybeans. The E. heterophylla biotype was supposed to be tolerant to herbícides whose mechanísm of action is on ALS enzyme ínhibition. The best treatment in absolute terms was lactofen at 120 g/ha plus Attach 0.2 % as sequential applicatíons. However, lactofen + imazethapyr (120+50 g/ha), lactofen + oxasulfuron (120+45 g/ha), lactofen + flumiclorac-pentil (120+40 g/ha), lactofen (120 g/ha) + Attach 0.2 %, lactofen (120 g/ha), lactofen + cloransulam-methyl (120+ 30 g/ha) and lactofen + chlorimuron-ethyl (120+ IO g/ha) were not statiscally dífferent (5% probability). It should be pointed out that the control of the biotype was considered medi um, therefore indicating that additional studies should be carried out to verify in which conditions mixtures of protox inhibitors with ALS inhibiting herbicides should be recommended considering the tolerance of the biotype to imazethapyr and chorimuron-ethyl that were components of some herbicide mixtures.
Identification of glyphosate-tolerant soybean plants through germination test
Since DNA tests are relatively expensive and time-consuming for the detection of the presence of the gene in plant materiais confering glyphosate tolerance to soybean, an experiment was carried out with the objective of developing a rapid and simple laboratory test for identifying glyphosate-tolerant soybean seeds, through standard seed germination tests. Seeds from six susceptible and twelve glyphosate-tolerant genotypes were used. The treatments consisted of cotiledonar/foliar spray of a glyphosate solution at the concentration of 8960 mg/l with 100 Ilha spray volume (equivalent to 2 g/ha) on the fifth day from the beginning of the germination test and soaking of the germination paper with glyphosate solutions at the concentrations of 0, 280, 560, 1120,2240,4480,6720, and 8960 mgll. The experimental units consisted of roIled germtest paper containing 50 seeds, replicated 8 times, except for the foliar spray treatment where 25 seeds were lined on the first third ofthe germtest paper. The germtest paper was weighed and the glyphosate solutions were added according to the treatments, in volume equivalent to three times the paper weight. Percentage of normal, abnormal and dead seedlings was assessed for eight days, by which time germination had ceased. This research demonstrated that it is possible to detect the presence of glyphosate-tolerant soybean seeds by the lab germination test using glyphosate at the rate of280 mg!liter ofthe imbibition water.
Summer development of wild poinsettia (Euphorbia heterophylla) biotypes resistant and susceptible to ALS inhibitors
A trial was developed under greenhouse conditions to compare the summer development ofthree ALS resistant wild poinsettia (Euphorbia heterophylla) biotypes from Passo Fundo, Não-Me-Toque and Rio Pardo, and one susceptible, from Porto Alegre. The experimental design was completly randomised, with three replicates, in a 4 x 5 factorial design ,where the first factor corresponded to the four biotypes ofwild poinsettia and the second to five periods of development (13,23,33,43 and 53 days after emergence (DAE)). Except at 13 DAE, total dry matter and leaf area were not different among biotypes. Total dry matter of the biotype from Não-Me- Toque stabilized before others and this had a high proportion of its mass allocated to the leaves.
Efficacy and selectivity of tank mixtures of preemergence herbicides in no-till soybean.
A trial was carried out on Bela Vista Farm, Serranópolis (GO), to evaluate the efficiency and selectiveness ofherbicide combinations applied in preemergence for soybean cv. Rainha. The treatments used were: metalochlor+diclosulam (2400+35 g/ha), sulfentrazone+diclosulam (250+25, 300+20, 350+ 15 and 200+35 g/ha), clomazone+diclosulam (504+25, 720+25, 828+25, 504+30, 720+30 and 828+30 g/ha), as well as an untreated control. It was concluded that the herbicide mixtures were selective for soybean cv. Rainha. Sulfentrazone+diclosulam and clomazone+diclosulam, independently ofthe dose used showed an efficient control of capim-carrapicho (Cenchrus echinatus), picão-preto (Bidens pilosa), trapoeraba (Commelina benghalensis), leiteiro (Euphorbia heterophylla) and guanxuma (Sida rhombifolia), close to that ofmetolachlor+diclosulam (2400+35 glha). The lowest bean yield was obtained with the untreated control. Significant differences betwen the chemical treatments for productivity were not observed but the lowest bean yield was obtained with the untreated control. The dry weight of weeds in the untreated control was superior to that obtained with chemical treatments.
Selectivity of preemergence herbicides in a sunflower crop
One obstacle to sunflower production is weed competition. A limited number of herbicides have been registered for this crop in Brazil and the lack ofwide spectrum broadleafweed control herbicides increases the need for other weed control methods. A field experiment was conducted at Embrapa Soja, Londrina county, Paraná State, Brazil, to evaluate sunflower tolerance to preemergence herbicides. The treatments were acetochlor+oxyfluorfen (1536+240 g/ha), oxyfluorfen (360 g/ha), oxyfluorfen (240 g/ha), Iinuron (1000 g/ha), aclonifen (1800 g/ha), oxadiargil (800 g/ha), diflufenican (25 g/ha), triflluralin (1800 g/ha), metolachlor (1920 g/ha), sulfentrazone (300 g/ha), prometrine (1600 g/ha), alachlor (3360 g/ha) and a noherbicide control. The treatments acetochlor+oxyflorfen (1536+240 g/ha) and oxyfluorfen (360 g/ha) caused crop injury but this phytotoxicity did not affect oil content and yield. AIl evaluated treatments were suitable for use with the Morgan M-742 sunflower cultivar.
No-tilIage management systems and their influence under postemergence herbicides in a soybean crop
The objective of the experiment was analyse different no-tillage management systems and postemergence control under a soybean crop, in São João do Ivaí (PR), in the agricultural year 1998/99. The treatments used in the management system sequence to control Commelina benghalensis (from 2 leaves to ramified plants) and Brachiaria plantaginea (from 2 leaves to tillered plants) were: (M1) sulfosate and paraquatldiuron+diquat (864 and 300+240 g/ha); (M2) sulfosate+2,4-D and paraquatldiuron+diquat (864+670 e 300+240 g/ha); (M3) sulfosate and paraquat/diuron+diquat (672 e 300+240 g/ha); (M4) sulfosate+2,4-D and paraquat/diuron+diquat (672+670 and 300+240 g/ha); (M5) control. The first application of the M1 and M2 sequence was carried out 26 days before sowing (DBS) and at 40 DBS with M3 and M4, and the second application was carried out on the sowing day for ali treataments. Ali manegement systems were subdivided and the control of C. benghalensis (I - 2 leaves) and Raphanus raphanistrum (I - 2 leaves) after soybean emergence was evaluated for the treatments with fomesafen (125 g/ha) in a single dose, 19 days after sowing (DAS); fomesafen and fomesafen (125 and 125 g/ha) in sequence 19 and 27 DAS; chlorimuron-ethyl+imazethapyr (10+ 150 g/ha) in a single dose 25 DAS, and a control. The antecipation ofthe management (40 DAS), facilited reduction in herbicide use and a better control of C. bengalensis and B. plantaginea. Where the management system obtained control above 97% (Ml e M4) the half fomesafen dose (125 g/ha) provided a satisfactory control of C. benghalensis. The sulfosate and paraquat/diuron+diquat sequences al\owed the management of C. benghalensis.
Impact of herbicides on a predator ant guild
The effects of alachor, metolachlor, dimethenamid and diuron herbicides on a predator ant guild were evaluated in Dourados, MS (22°13'16"S and 54°48'20"W). Two control areas, with and without weeds, were used in the study. The ants were sampled using two sardine baits per plot with four replications per treatment. Solenopsis sp. was the most abundant ant species among the five sampled species. There was a decrease in the number of ants in the treatment and control plots afier 40 days. No significant differences were found between the herbicide and control plots.
Selectivity of sulfentrazone on soybean cultivars and the residual effects on rotation crops, in Savanna soils
Edaphic characteristics, in interaction with the clímate and the specific cultivar, may cause crop toxicity in an area treated with a residual herbicide. Two experíments were carried out on two Cerrado soils, in Campo Grande (MS), to evaluate the selectivity of sulfentrazone on 21 soybean cultivars, as well as the residual effects on successive soybean crops.The first experiment was on a sandy soil, with 8% clay, 2% lime, 90% total sand and 2.3% organic matter. The second experiment was carried out on a soil with 35% clay, 11% lime and 54% sand. Treatments in both cases were: sulfentrazone at 500 and 1000 g/ha, diclosulam at 35 and 70 g/ha, sulfentrazone+diclosulam at 250+25 and 500+50 g/ha, and a control where the weeds were mechanically cut. Results showed that higher phytotoxicity was found only in the experiment on sandy soil, with sulfentrazone at 1000 g/ha and diclosulam at 70 g/ha, in Conquista cultivar, and at a lower level in the Taquari and Paiguás cultivar. Millet, oat and sorghum sown in sucession to soybean, showed phytotoxicity symptoms to sulfentrazone (1000 g/ha) and diclosulam (70 glha). Chemical treatments, in both experiments, showed efficient control of Digitaria horizontalis, Amaranthus viridis, Ipomoea grandifolia, Portulaca oleraceae and Bidens pilosa. It was concluded that preemergence aplications of diclosulam can injure some soybean cultivars on sandy soil.
Efficiency of herbicides in preemergence control of weeds in a rice crop
The experiment was developed in 1998/99, in the ill\TESP Experimental Farm, in Selvíria (MS), on soil with a loamy texture. The objective ofthe present work was to evaluate the tolerance and efficiency ofpreemergence herbicides on rice and observe the effects ofthe treatrnents on the productivity ofthe crop. The rice strain used was Caiapó. The experimental design was a complete randomized block with ten treatments and four replications. The treatrnents were the following: trifluralin (1200 g/ha), oxyfluorfen (120 and 240 g/ha), c1omazone (500 g/ha), trifluralin + oxyfluorfen (1800 + 120 and 1200 + 240 gI ha), c1omazone + oxyfluorfen (500 + 240 g/ha), pendimethalin (1250 g/ha) and controls with and without weeds. The efficiency of the treatments was evaluated in terms of the control of the weeds and the effect of the treatments on the productivity of the crop. The herbicides and doses tested in the experiment provoked symptoms of initial toxicity to the rice plants, which disappear 45 days afie r application and these do not affect the productivity ofthe crop. The main weed species that appeared in the experiment included: Ipomoea acuminata, Commelina benghalensis, Blainvillea rhomboidea and Amaranthus dejlexus. The treatments oxyfluorfen (240 g/ha) and c1omazone + oxyfluorfen (500 + 240 g/ha) provided the best control ofthe studied weed. The interference ofthe weeds reduced the productivity ofthe crop in 56% in relation to the weed free control.
Effect of postemergence herbicides, applied at different weed stages, compared to atrazine+metolachlor in corn
The experiment was carried out during 1997/98, in Rio Verde (GO), to evaluate the efficacy ofpostemergence herbicides, applied at ditferent times, compared to atrazine+metolachor applied at preemergence.The etfect ofthese herbicides on some agronomic characteristics of com was also evaluated. The hybrid com used was AG-50 11, sown on 10/26/97, and the treatments were: postemergence application of atrazine+metolachlor (1400+2100 g/ha), early postemergence application of atrazine/metolachlor+nicosulfuron (1000/1500+ 12 g/ha), postermergence aplication of atrazine vegetal oil+nicosulfuron (1600+20 g/ha), late postemergence application of atrazine+nicosulfuron (1000+40 g/ha), late aplication of nicosulfuron (50 glha) and two controls: with and without hoeing. The herbicides controlled Ipomoea grandifolia, Euphorbia heteroplylla and Commelina benghalensis. Only nicosulfuron (50 g/ha) did not control C. benghalensis. Final stand and height of first com ear were not atfected by the herbicibes. Nicosulfuron (50 glha) however atfected plant height. The index ofmechanical harvest was excellent, except for crops which received nicosulfuron. This index was excellent and difficult, respectively, for the control with hoeing and without hoeing. The weed dry weight was higher in the control without hoeing.
Use of 2,4-D as a burndown treatment for soybeans in no-till cropping systems in the Cerrados region
A field experiment was carried out in the Cerrados region in Rondonõpolis, MT, Brazil, in order to evaluate the behavior of2,4-D amine, applied alone and as a pre-site preparation at 72, 144,216,288,432,576 and 720 grams per hectare, to control the weed spectrum in no-till soybean. Commelina benghalensis was the predominant weed species. Soybean was seeded at 1,2,3, 4,5,8 and 10 days after burndown treatment and the planting timing was crossed with 2,4-D rates, applied in a randomized block design in three replications. The crop response as measured by stand and plant height was evaluated at 45 days after spraying and as a pre-harvest evaluation at the first pod insertion. The number of pods per plant, dry weight and productivity were assessed. The results sbowed that ali the variables analyzed were affected by the herbicide when soybean was planted up to 5 days after spray treatment. Considering only the planting time, the productivity was not statisticaIly different, however it was significantly reduced when the rates of2,4-D were increased. Even at the lower rate, a plant growth reduction was observed. As conclusion, 2,4-D amine can be recommended as a burndown treatment for Cerrados sandy soil, up to 720 g/ha, since soybeans are planted at least 8 days after the herbicide application.
Metsulfuron-methyl avaliation in the control of weeds in an área of pasture seed production
An experiment was conducted at the Bom Futuro Farm, Rondonópolis, MT during 1999/2000 in a sandy soil, to determine the effects of metsulfuron-methyl on postemergence control of weeds in a field of Brachiaria brizantha seed production. Treatments were: metsulfuron-methyl at 3.0 glha and at 3.6 glha in one application or in two applications, 2,4-D at 288 glha (as a reference) and a check. Tridax procumbens, Spemacoce latifolia, Chamaesyce hirta were controlled by metsulfuron-methyl at 3.0 and 3.6 glha in a sole application. It was observed slight injury-to B. brizantha caused by the treatrnent with two applications of metsulfuron-methyl and by 2,4-D. B. brizantha seed production, weigth of 100 panic\es were ligher in the treatments with herbicides.
Residual effect of chlorimuron-ethyl tank mixed with glyphosate applied as a burndown treatment for pre-site preparation in soybean
An experiment was conducted on a Cerrado sandy soil during 1999/2000. The objective ofthe experiment was to evaluate the residual effect of chlorimuron-ethyl tank mixed with glyphosate applied as burndown treatment for pre-site preparation, to control Bidens pilosa in preemergence. The experimental design was a randomized complete block with four replications. Treatments were as follows: glyphosate at 720 and 1440 glha, glyphosate+chlorimuron-ethyl at 720+ IO and 720+20 glha, glyphosate+chlorimuron-ethy"I+flumioxazin at 720+20+40 glha and glyphosate+ 2,4-0 at 720+460 glha. An untreated check was also included. Treatments were applied by a CO2 backpack sprayer, using 2.1 kg/crrr' ofpressure, with four 110.02 XR nozzles, and spray volume of200 Ilha. Evaluations ofpercentage control and number of Bidens pilosa per square meter were made at )5, 30 and 45 days after treatments. Chlorirnuron-ethyl+glyphosate at 20+ 720 g/ha and chlorimuron-ethyl+flumioxazin+glyphosate at 20+40+720 g/ha showed excellent residual control for Bidens pilosa. Consequently, chlorimuron-ethyl can be used as an alternative and safe herbicide in soybean for pre site preparation tank mixed with glyphosate.
Efficacy of desiccant herbicides in no-till soybean
This research was done to evaluate the tolerance and efficacy ofpostemergence herbicides to contrai established weeds in no-ti 11soybean. Experiment was conducted at Rondonópolis, Mato Grosso, from 1999 to 2000, in the Sementes Maggi 2 Farm, on a loamy texture soil, using Emgopa 313 variety. Planting was done in an are a with adult weeds, in the system of "direct planting on the weeds". Herbicides were applied in postemergence ofthe weeds and the culture. Experimental design was a randomized complete block with seven treatments and four replications. The treatments were as follow: glyphosate (960 and 1920 g/ha), chlorimuron-ethyl+glyphosate (10+960 and 20+960 g/ha), chlorimuron-ethyl+glyphosate+flumioxazin (20+960+40 gI ha), glyphosate+ 2,4-D (960+868 g/ha) and untreated check plot. Efficacy ofherbicides was evaluated in the base of controlling adult weeds and the residual effect of the treatments. No injury on soybean was caused by any treatment. Weeds found in the experimental area were: Commelina benghalensis, Cenchrus echinatus and Bidens pilosa. Ali treatments were efficient in the contrai of the studied weeds, except for glyphosate isolated, in C. benghalensis. Chlorimuron-ethyl (10 and 20 g/ha) applied together with glyphosate, provided a significant residual effect for Bidens pilosa, reducing the occurrence ofthe weed during the entire soybean cycle. .
Efficacy of postemergence herbicides to control Euphorbia hetrophylla in no-till soybean
The experiment was carried out in 99100, at the experimental field ofthe State University ofSão Paulo, in Selvíria,MS, on a medium texture soil. The objective of the study was to evaluate the tolerance and agronomic efficacy of postemergence herbicides in the control of adult plants of Euphorbia heterophylla for no-till planting of soybean cv. Tucano. Planting was done in area with adult plants of E. heterophylla, in the system of"direct planting on the weeds". The herbicides were applied in postemergence ofthe weeds and the culture. Experimental design was a randomized complete block with six treatments and four replications. Treatments, applied one day before planting, were: glyphosate (960 and 1920 g/ha), chlorimuronethyl+ glyphosate (10+960 g/ha), chlorimuron-ethyl+ TY029+glyphosate (10+ 10+960 giba) and control with and without weeds. The parameters evaluated were the control of weeds, the residual effect and the crop tolerance. No injury to soybean was observed in any treatment. Glyphosate (960 and 1920 g/ha), chlorimuron-ethyl+glyphosate (10+960 g/ha) and chlorimuronethyl+ TY029+glyphosate (10+ 10+960 giba), were efficient in the control of adult plants of E. heterophylla. The herbicide chlorimuron-ethyl (10 g/ha) applied together with glyphosate, on adult weeds, provided residual effect for E. heterophylla, reducing the occurrence of the weed during the entire soybean cycle.
Effect of postemergence herbicides on agronomics characteristics of soybean cv. Emgopa 316
A experiment was carried out at the Bela Vista Farm, in Serranópolis, State ofGoiás, with the objective to evaluate the effects of postemergence herbicides on agronomic characteristcs of soybean cv. Emgopa 316, with premature maturation cycle. Treatments consisted oflactofen (168 glha), chlorimuron-ethyl (15 glha) + mineral oil (0.2 v/v), fomesafen (250 g/ha) + mineral oil (0.2 v/v), imazethapyr (100 g/ha), chlorimuron-ethyl+lactofen (12.5+96 g/ha), chlorimuronethyl+ fomesafen (12.5+ 150 g/ha), chlorirnuron-ethyl+imazethapyr (12.5+50 g/ha), imazethapyr+lactofen (50+96 g/ha), imazethapyr+fomesafen (50+ 150 g/ha), and a handweeded control. The studied herbicide doses caused some injury to soybean, with more intensity in the treatments with lactofen. However, they did not significantly intluence the height of plants at 15, 30 and 45 days after treatments and at soybean harvest. The herbicides also did not significantly affect insertion height of the first pod, final stand, number of podslplant, weight of 1000 seeds and grain production. Imazethapyr+fomesafen (50+ 150 g/ha) gave the best result in number of internodes, but it did not differ statistically from the other treatments, except for lactofen (168 g/ha), that proportioned the lowest number of internodes. Lactofen isolated or combined with chlorimuron-ethyl or with imazethapyr can be used in soybean cv. Emgopa 316, showing results similar to fomesafen isolated or in mixture with chlorimuron-ethyl or imazethapyr.
Control of Euphorbia dentata in soybean with postemergence herbicides
Euphorbia dentata is an annual weed which grows during spring and summer. Its has acquired importance mainly associated with soybean crops in the central area in Buenos Aires Province, Argentina. This weed is highly competitive in soybean fields and its control is very difficult. The objective of this work was to evaluate the effectiveness of Euphorbia dentata control with postemergence herbicides in soybean crops. Field studies were conducted in Azul Co., in a highly naturally infested soybean crop (110 plants of Euphorbia dentata/m2). The treatrnents were: imazethapyr 100 g/ha, chlorasulam-methyl 33.6 g/ha + no ionic surfactant 0.2% v/v, lactofen 96 g/ha + no ionic surfactant 0.2% v/v, chlorimuron-ethyI8.75 g/ha + no ionic surfactant 0.2% v/v, chlorasulam-methyI33.6 g/ha + lactofen 96 g/ha + no ionic surfactant 0.2% v/v, chlorimuron-ethyI8.75 g/ha + lactofen 96 g/ha + no ionic surfactant 0.2% v/v, untreated control and control without weeds which were removed by hand. The experimental design was a randomised complete block with four replications. Evaluations were made 20 and 45 days after application and on harvest. No treatment reached 70% control. The highest levels of effectiveness were obtained with imazethapyr (67%) and with the mixture chlorasulam+lactofen (65%) with no significant differences between them. Soybean yield showed a similar response: the productivity in those treatments were 2850 and 2650 kglha respectively. Crop productivity decrease by 35% in untreated control compared with the treatment without weeds whose yield was of2920 kg/ha.
Herbicides inhibitors of EPSPs: literature review
The herbicides inhibitors ofthe enzyme EPSPs, glyphosate and sulfosate, are among the most used compounds in Brazil and in the world. The objectives ofthis review are to synthesize the information about the weeds controlled, physic-chemical characteristics, fundamentais of absorption, translocation, decomposition, mechanism of action, environmental performance, and plant resistance to the EPSPs inhibitors. With this review, we want to provide to the agricultural community information to obtain a more rational, efficient and economical performance ofthese compounds.
Responses of soybean cuItivars to herbicides
An experiment was conducted in Passo Fundo, RS, on a Red Oxissol distrofic soi!, during the 1999/2000 soybean growing season to evaluate cultivar differences in response to herbicides applied alone and as tank mixtures. Height reductions were observed in cultivars BRS 153 and BRS 138. The cultivar BRS 153 exhibited height reductions to diclosulan applied at the rate of 70 g/ha while the cultivar BRS 138 exhibited height reductions to sulfentrazone at 1200 g/ha, diclosulan at 70 g/ha, sulfentrazone+diclosulan at 250+25 g/ha and sulfentrazone+clomazone at 1000+ 1440 g/ha. There was no effect ofthe treatmens on the other evaluated soybean parameters, including yield.
Selectivity ofpre-emergence broadleafweed herbicides applied on clay soil in sunflower crop
Weed control in sunflower is required to avoid poor growth, yield loss, and weed problems in crops grown after sunflower. Limited availability of sunflower herbicides requires a rigid weed control program consisting of cultural, mechanical, and chemical measures for the most profitable crop production. Two experiments were carried out at Embrapa Soja, Londrina, Parana State, Brazil, in 1998, to evaluate the selectivity ofpre-emergence broadleafweed herbicides in sunflower crop.ln one of the experiment, acetochlor was used at rates of O, 1152,2304,3456 and 4608 glha. In the other experiments, oxyfluorfen was applied at rates of 0,360,720, 1080 and 1440 g/ha, Acetochlor at2304 glha and athigherrates reduced oil content and sunflower yield. However, oxyfluorfen (360 g/ha) was seletive to sunflower. The risk offitotoxicity appears to be greater on low organic matter and coarse textured soils.
Herbicide retention by mulching in corn, under no-tillage system
The objective ofthis trial was to study the reactions ofthe residual herbicide mixtures metolachlor plus atrazine and atrazine plus isoxaflutole applied in pre-ernergence for com under no-till system. The experiment was settled in Londrina, using black oat (Avena strigosa) mulch. A randomized complete block design was used. The treatments comprised the following rates ofherbicides: zero, 0.5N, 1.ON, I.5N and 2.0N (N=normal rate ofherbicide). In the present study, N=21 00 g/ha metolachlor + 1400 g/ha atrazine and 1660 g/ha atrazine + 68 g/ha isoxaflutole. Twenty four hours after herbicide applications, 48,3 mm ofwater was applied in the experiments . In the next day, samples of soil and straw were taken for chromatographic analysis purposes. The results showed that 50% of the metolachlor and atrazine leached from the straw to the soil. Approximately 10% of atrazine and 30% of isoxaflutole were detected in the soil after irrigation.
Selectivity ofherbicides diclosulam, flumetsulam, and cloransulam in several soybean cultivars
Selectivity is the capacity ofherbicides to control weeds in a crop without reducing the productivity and quality ofthe final product. It cannot be determined only by the verification of presence or not oftoxicity symptoms, because there are already well-known herbicides that can reduce the productivity of crops without producing visual effects and also herbicides that provoke quite accentuated toxicity, but that allow the crop to manifest its productive potentials fully. This work has the objective to evaluate the selectivity of diclosulam, flumetsulam and cloransulam in soybean BR-16, BR-911241 O, Embrapa 64 (Ponta Porã), BR-37, BR-9113306, Lambari, Cambará, Embrapa-61, Conquista and Embrapa 65 (ltapoty) cultivars. The experiment was carried out in the experimental area of Embrapa Agropecuária Oeste, in Dourados, MS, during 1998/99. The experimental design was a split plot, with four replications. The main plots were the herbicides and the subplots were the cultivars. Plant height, number of plants by meter and grain production were evaluated. Diclosulam at 35 g/ha and mixtures of diclosulam+flumetsulam at the rates of20+94 g/ha, cloransulam+lactofen at 40+ 120 g/ha and cloransulam+imazethapyr at 30+50 g/ha did not affect the height and 1998/99. A semeadura e aplicação dos tratamentos em préemergência ocorreram em 12.12.98. Os tratamentos em pósemergência foram realizados em 05/01/99. As cultivares de soja utilizadas foram BR-16, BR- 911241O,Embrapa64(pontaPorã), BR-37, BR-91 13306,Lambari, Cambará, Embrapa-6I, Conquista e Embrapa 65 (Itapoty). Foram realizadas as práticas culturais recomendadas para a região de acordo com Embrapa (1996). O solo da área experimental apresentava as seguintes características de fertilidade e textura: number ofplants by linear meter and the production ofgrains, showing to be highly selectives to soyben BR-I6, BR-9II2410, Embrapa 64 (ponta Porã), BR-37, BR-9113306, Lambari, Cambará, Embrapa-61, Conquista and Embrapa 65 (ltapoty) cultivars.
Efficacy of flumioxazin alone or in mixture with sulphosate to desiccate Ageratum conyzoides and Commelina benghalensis previous to soybean
Two experiments were carried out to test the efficacy offlumioxazin to desiccate Ageratum conyzoides and Commelina benghalensis previous to soybean planting. One of them tested doses of the herbicide alone and the other tested doses of flumioxazin in mixture with sulphosate. Flumioxazin (30, 40 and 50 g/ha) mixed with mineral oil (0,5 and 1,0%) showed an excellent control (more than 90%) of Ageratum conyzoides and Commelina benghalensis. The mixture flumioxazin (20 or 25 g/ha) + sulphosate (960 or 1,440 g/ha) showed an excellent (90-99%) or acceptable (80-89%) control of Ageratum conyzoides and Commelina benghalensis, respectively. No toxicity was observed in the soybean plants by any treatrnent involving flumioxazin.
Postemergence broadleafweed control in soybean with bentazon 400/acifluorfen 170 and bentazon 400/acifluorfen 140
The objective ofthe experiment was to evaluate the efficacy of hérbicides bentazon 400/acifluorfen 170 and bentazon 400/acifluorfen 140, alone and in mixture with mineral oil (Assist) in early postemergence control ofweeds in soybean. Treatrnents were: bentazon 400/acifluorfen 140 (570, 684 and 855 glha), bentazon 400/acifluorfen 170+mineral oil (684+378 glha), bentazon 400/acifluorfen 140 (540, 648 and 810 glha), bentazon 400/acifluorfen 140+mineral oil (648+378 glha) and fomesafenlfluazifopbutyl (500 g/ha) and a weedy and a weeded control. The results showed no difference in grain productivity between the herbicide treatments and the weeded control. However the weedy control showed differences in relation to alI treatments, with productivity of 813 kglha. Soybean density at harvesting, plant height, first pod insertion height and weight of 100 seeds, showed no difference between treatments. Amaranthus viridis was controled by ali herbicides, with 95% control or more until 21 days after aplication. Nicandra physaloides was also controlled by ali herbicides from 7th to 21 st day after spraying. In Sida rhombifolia, ali herbicides showed index control higher than 97% until 21 days after aplication. Seven days after herbicide spraying it was observed negligible toxicity to soybean plants. Seven days later there was no toxicity.
Weed control in sunflower on clay textured soil
Lack ofbroadleaf chemical control options in sunflower is a major production problem. An experiment was conducted at Embrapa Soja in Londrina, Paraná State, Brazil, to evaluate broadleafweed control and agronomic efficiency ofpreemergence herbicides applied on clay soil. The treatrnents were: sulfentrazone (350 and 600 g/ha), acetochlor (2100 and 2520 g/ha) and oxyfluorfen (360 and 480 g/ha), weed and hand hoeing treatments. Sulfentrazone applied at 350 g/ha was seletive to sunflower cultivar M 734 and efficient in controlling wild poinsettia tEuphorbia heterophylla) and momingglory (Ipomoea grandifolia). Acetochlor was not efficient in wild poinsettia control. Oxyfluorfen applied at 360 g/ha was seletive to sunflower cultivar M 734 and efficient in wild poinsettia control. The risk offitotoxicity appears to be greater on low organic matter and coarse textured soils.
Efficiency and selectivity of lactofen mixed with other broadleaf herbicides in the control of weeds in soybean
An experiment was carried out with the objective to evaluate the efficiency and selectivity of lactofen in conbination with other herbicides in the control of weeds and to study the effects of the mixtures on some soybean characteristics. The experimental design was a randomized complete block, with ten treatrnents and four replications. Treatrnents were: oxasulfuron (45 g/ha), oxasulfuron +lactofen (37.5+96.0 and 45.0+96.0 g/ha), c1oransulam-methyl + lactofen (29.4+96.0 and 37.8+96.0 g/ha), and two controls ( with and without hoeing). Ipomoea grandifolia, Sida rhombifolia and Commelina benghalensis were efficiently controlled by the combination of oxasulfuron + lactofen, c1oransulam-methyl + lactofen and chlorimuronethyl + lactofen, with more than 82% control at 45 days after treatrnents. Herbicides aplied alone (not in combination) except Revista Brasileira de Herbicidas v.l, n.I, 2000 79 Antônio Carlos de Barros for cloransulam-methyl, did not give good weed control. Treatrnents did not influence soybean height, first pod insertion height and final stand. Weeds dry weight was higher in the control without hoeing. There was no productivity difference between the treatrnents with herbicides; however, the interference ofweeds in the control without hoeing decreased productivity in 22% compared to the productivity in the treatrnent chlorimuron-ethyl + lactofen (10+96 g/ha).
Evaluation of tank mixtures of imazethapyr with other herbicides for Bidens pilosa and Euphorbia heterophylla control in soybean
This study was intended to evaluate the selectivity to soybean and efficiency to control Bidens pilosa and Euphorbia heterophylla of tank mixtures of imazethapyr and other broadleaf herbicides. Treatrnents included imazethapyr (100 g/ha), imazethapyr + chlorimuron-ethyl (50+ 10,50+ 12.5 and 60+ 10 g/ha), imazethapyr + lactofen (50+96,50+ 120,60+96,60+ 120 and 12.5+120 g/ha), imazethapyr+oxasulfuron (50+37.5 and 60+37.5 g/ha), chlorimuron-ethyl + lactofen (12.5+120 g/ha), oxasulfuron (45 g/ha), chlorimuron-ethyl (15 g/ha), lactofen (168 g/ha), and weedy and weed free checks. All combinations ofherbicides were applied postemergence, at V4-V5 soybean growth stage (3 to 4 composite leaves). Weeds, development stage and population density in experimental area were: Bidens pilosa (2 to 4 leaves and 179 plants/m") and Euphorbia heterophylla (4 to 5 leaves and 63 plants/m-). Tank mixtures of imazethapyr with chlorimuron-ethyl, lactofen and oxasulfuron were bighly eificient for both weeds, providing >97% control at pre-harvest evaluation, with no significant diferences among different mixtures or among different rates within each mixture. ln relation to E. heterophylla, mixtures containing imazethapyr were more eff1cient than both chlorimuron-ethyl+lactofen, and isolated use of chlorimuron-ethyl or lactofen. Mixtures containing imazethapyr provided a residual effect up to 21 days afier application for E. heterophylla. No chemical treatrnent affected soybean development or productivity.
Herbicide retention by mulching in soybean, under no-tillage system
The objective of this trial was to study the mulch retention of the herbicide mixtures imazaquin + pendimethalin and sulfentrazone + metribuzin applied in pre-emergence for soybean under no-tillage system. The experiment was settled in Londrina-PR, Brazil, with black oat (Avena strigosa) mulch. A randomized complete block design was used. The treatrnents comprised the following rates of herbicides: zero, 0.5 N, 1.0 N, 1.5 N and 2.0 N (N=normal rate of the herbicide). ln the present study, N=150 g/ha imazaquin + 1200 g/ha pendimethalin and 350 g/ha sulfentrazone + 360 g/ha metribuzin. After twenty four hours ofherbicide applications, 48.3 mm ofwater was applied in the experiments. ln the next day, samples ofsoil and straw were taken for chromatographic analysis purposes. The results showed that 100% of imazaquin and sulfentrazone leached from the straw to the soil. Approximately 50% of metribuzin and 100% of pendimethalin were retained by the oat straw.
Glyphosate biological efficacy in the control of andropogo grass
Andropogo grass (Andropogon gayanus) is a forage very well adapted to poor pasture soils throughout Cerrados (Brazilian savannas). During the last years, with the expansion of no tillage, specially within the cropping system named "crop/pasture integration", where glyphosate is the main tool the farmers have to c1ean the fields before planting. Andropogo grass became a problem weed due to its natural resistance to that herbicide. Andropogo leaves are strongly hairy, and this is, probably, the cause of that resistance. The field trial was carried out in Jataí-GO, to evaluate the efficacy of two glyphosate formulations (Roundup CS-liquid and Roundup WG-soluble granules), alone and in tank mixtures with three adjuvants (Silwett L77, Assist and diesel oil) in the postemergence control (bumdown) of andropogo grass. Adjuvants were supposed to improve glyphosate uptake, overcoming the presence of hairs on the leaf surface. Results showed that: 1- there were no differences between the two glyphosate formulations; 2- the addition of adjuvants slightly improved efficacy, but differences were not statistically significant; 3- Andropogo control can be obtained by the use of glyphosate at the rate of, at least, 1800 g AE/ha, with or without adjuvants, when the grass is under an intense vegetative growth, with 30 to 40 em of height.
Efficacy of selected herbicides in the desiccation of three plant species for soil cover
An experiment was carried out with the objective of evaluating the efficiency of selected herbicides in the desiccation of three plant species in Dourados (MS), Brazil, in 1995/96. A randomized block design was used in three plant species: black oat (Avena strigosa ), millet (Pennisetum typhoydes) and Brachiaria plantaginea, with four herbicides in three rates: paraquat (0.30, 0.40 and 0.60 kg/ha), glyphosate (0.72, 1.08 and 1,44 kg/ha), sulfosate (0.96, 1.44 and 1.92 kg/ha) and glyphosate+2,4-D (0.54+0.67, 0.54+1.0 and 0.54+1.34 kg/ha). The herbicides glyphosate, sulfosate and the mixture glyphosate+2,4-D were efficient to desiccate the three species in all doses. The plants of millet and Brachiaria plantaginea showed a re-growth after 36 days of the application of paraquat.
Efficiency of lactofen in controlling Euphorbia heterophylla resistant to herbicides inhibitors ofthe enzyme acetolactate synthetase (ALS)
The occurrence of resistant weeds is a process ofbiotype selection, with mutant genetic traits, which support applications of certam herbicides to which most of the population are susceptible. Imazethapyr, chIorimuron-ethyl, and oxasulfuron herbicides have the same mode of action; they are inhibitors ofthe acectolactate synthetase enzyme (ALS), which is responsible for the synthesis ofthree essential aminoacids: valine, leucine, and isoleucine. These herbicides are widely recommended and used for controlling Euphorbia heterophylla. However, biotypes of E. heterophylla which are resistant to those herbicides were identified in Central Western Brazil. This work was carried out with the objective of evaluating the efficiency of lactofen, applied singly and in mixture with imazethapyr, chlorimuron-ethyl, and oxasulfuron for the control of E. heterophylla biotypes which are resistant to ALS inhibitors. The results showed that sequential application oflactofen at 60 + 60 g/ha was efficient in controlling E. heterophylla. Lactofen mixtures with imazethapyr, chIorimuron-ethyl, and oxasulfuron showed good efficiency, thus demonstrating that mixing herbicides of different action mechanisms is a good strategy for controlling E heterophylla biotypes which are resistant to ALS inhibitors. Lactofen mixture with flumic1orac-pentil showed good control of E. heterophylla. The evaluated herbicides and mixture rates were not harmful to soybean plants.
Efficacy of mixtures of imidazolinone herbicides on tolerant mayze
Mixtures of imidazolinone herbicides were applied in pre and postemergence on a hibrid of maize tolerant to this group, to control Richardia brasiliensis, Acanthospermum australe, Brachiaria decumbens and Spermacoce latifolia. Two experiments were conducted, one in each time of application. ln pre-emergence the following mixtures were tested: imazethapyrl imazapyr (79+26, 90+30, 70+35 and 80+40 g/ha), imazethapyr/imazapic (60+30, 70+35 and 80+40 g/ha), imazapicl imazapyr (68+22, 70+35 and 79+26 g/ha), compared with atrazine/metolachlor (3250 g/ha). The following mixtures were tested in postemergence: imazethapyr/imazapyr (57++ 18, 68+22, 79+26, 50+25, 60+30 and 70+35 g/ha), imazapic/imazapyr (40+20,50+25,60+30,45+ 15,57+ 18 and 68+22 g/ha), compared with nicosulfuron (60 g/ha). Two other controls were also included on both experiments: presence or absence ofhand weeding. No toxicity was observed on maize by any mixture, dose or time of application. The used doses of imazethapyr/imazapyr, imazapic/imazapyr and imazethapyr/imazapic, applied in pre-emergence, showed an excellent control of A. australe, R. brasiliensis and S. latifolia. lmazethapyr/imazapic also controlled B. decumbens. ln postemergence application an excellent control of both R. brasiliensis and A. australe was only achieved with imazapic/imazapyr, Imazethapyr/imazapyr also controlled very well A. australe. The control of B. decumbens was acceptable in postemergence applications.
Effect of delayed havesting on the quality of soubean seeds desiccated with paraquat
This work was carried out in the field, in an area of comercial production of soybean seeds, Dokko cultivar, and in the Seed Laboratory ofthe University of Uberlândia, Brazil. In the field the treatrnents were distributed in a factorial arrangement (2 x 4) oftwo rates ofthe desiccant paraquat (0,0 and 0.2 kg/ha) and four harvesting times (at physiological maturation, normal harvesting time, 14 and 28 days after normal harvesting time). In the laboratory a new factor (treated and no treated seeds with fungicide). Data taken included seed humidity, weight of 1000 seeds, damage to the integument, seed germination and seed emergence in the field. Plant desiccation and delayed harvesting did not influence the weight of 1000 seeds. Damage to integument was small when the soybean seeds were harvested during physiological maturation and it increased with the delaying of harvesting. Germination and emergence in the field was reduced with harvesting delay, mainly when the plants were desiccated. Fungicide treatrnent did not influence germination or field emergence, showing that deterioration was caused by damage to the integument and not by incidence of plant pathogens.
Efficacy of the herbicide sulfentrazone in preemergence control of weeds in soybean
The experiment was conducted at the Teaching and Research Farrn of the State University of São Paulo, in Selviria- MS, a region ofCerrados vegetation. The objective ofthe study was to evaluate the selectivity and efficacy ofpreemergence application ofsulflentrazone in soybean. Treatrnents included sulfentrazone at 500,550 and 600 g/ha, sequential postemergence application of imazaquim and clethodim at 140 + 72 g/ha and tank mixed fomesafen + clethodim at 250 + 72 g/ha. A weedy and a weeded control were also included. Sulfentrazone at ali rates caused very low toxicity symptoms in soybean, IAC-15 cultivar, and gave good control of Acanthospermum hispidium, Bidens pilosa, Commelina benghalensis and Cenchrus echinatus.
Effects of desiccants aplication on the production and quality of soybean seeds in Uberlândia-MG, Brazil
Field and laboratory experiments were used to test the effect of selected desiccants on the productivity and quality of soybean seeds, Savana cultivar. ln the field ten treatrnents were arranged in a randomized complete block design, with four replications. Treatrnents were: (1) control (harvested during physiological maturation), (2) glyphosate-360 (0.36 kg/ha), (3) glyphosate-360 (0.72 kg/ha), (4) glyphosate-720 (0.36 kg/ha), (5) glyphosate-720 (0.72 kg/ha), (6) glyphosate-480 (0.36 kg/ha), (7) glyphosate-480 (0.72 kg/ha), (8) paraquat (0.30 kg/ha), (9) diquat (0.30 kg/ha), and (10) control (harvested during normal harvesting time). The treatrnents were evaluated for productivity, weight of 1000 seeds, mechanical damage ofthe integument, germination, vigor (natural aging) and field germination. Desiccants, at all rates, did not affect productivity and germination of soybean seeds. Seeds originated from plants desiccated by contact herbicides showed best vigor than those desiccated by sistemic herbicides. The desiccants did not improve seed quality, but their utilization could avoid, in adverse climate conditions, seed deterioration in the field, since the harvesting is antecipated in six days.
Efficacy of atrazine + simazine in post-emergence controI of weeds in maize, in Brazilian Cerrados
A trial was carried out to test the efficacy of formulations and doses of atrazine + simazine, in post-ernergence on maize (cv. BR-201). The following treatrnents were tested in a sandy Latosoil, in Uberaba, Brazil: Primatop 500 se (atrazine 250g/1 + sirnazine 850 g/l) at the doses of2500, 3000 and 3500 g/ha and Prirnatop 80 PM (atrazine 400 g/I + simazine 400 g/I) at the doses of2400, 3200 and 3600 g/ha, plus mineral oil (0.25% v/v); Triamex se (atrazine 250 g/l +sirnazine 250 g/I) at the dose of3000 g/ha; hand weeding and no control. There was no difference between treatrnents concerning the plant density, number of cobs and height ofthe first cob. The highest yield (3512 kg/ha) was observed with the application ofPrimatop 80 PM at 3200 g/ha and Triamex. The lowest seed weight was observed with Primatop 80 PM at 3500 g/ha. There was no difference between the herbicides and hand weeding concerning plant height. The best index for mechanical harvesting (98.0 - 98.5%) was achieved with Primatop 500 SC at 3000 and 3500 g/ha, Primatop 80 PM at 3200 and 3600 g/ha and Triamex. The best control of Digitaria horizontalis was achieved with Primatop 80 PM at 3600 g/ha (98.5%) and Primatop 500 SC at 3500 g/ha (98.0%), but the other doses of these formulations also showed excellent control of this species. The best control of Eleusine indica was obtained with Primatop 80 PM at 3600 giba (99.5%), Primatop 80 PM at 3200 giba + mineral oil (98.5%) and Primatop 500 SC at 3500 giba (98.0%). Primatop 500 se and Primatop 80 PM showed an excellent control of Borreria alata and Acanthospermum australe at 65 days after application, in ali tested doses. No symptom offitotoxicity was observed on maize after herbicide application.
Efficacy of chlorimuron-ethyl in the control of Melampodium perfoliatum in soybean
A new and important weed, Me/ampodium perfoliatum, has been growing in soybean plantations in the "Cerrados" of Minas Gerais, BraziI. The objective of this study was evaluate the biological activity and soybean tolerance to chorimuronethyl alone or tank rnixed with other postemergence herbicides. Treatrnents were: chlorimuron-ethyl (12.5 and 15 g/ha) + mineral oil (0.05% v/v), chlorimuron-ethyl + lactofen at 12.5+120 g/ha, chlorimuon-ethyl + fomesafen (12.5 + 150 gIha) + mineral oil (0.1% v/v) chlorimuron-ethyl + imazethapyr at 12.5 + 30 g/ha and a weedy and a weeded controI. Results indicate that chlorirnuronethy I (12.5 and 15 g/ha) + mineral oil has controlled efficiently (95 and 97%) M. perfoliatum. When chlorimuron-ethyl was rnixed with lactofen, and imazethapyr control increased to 96-99% up 132 days after application. Chlrimuron-ethyl alone or tank mixed with lactofen, fomesafen and imazethapyr has shown to be highly selective to soybean.
Effect of preemengence herbicides diclosulam and metolochlor for Sida rhombifolia control in soybean
An experiment was conducted on a Cerrado oxisol during 1996/97. The objective of experiment was to evaluate the effects of diclosulam and metolochlor alone or in combination, in preemergence control of Sida rhombifolia in soybean. The experimental design was a complete randomized block with four replications. Treatrnents were as follows: diclosulam at 25 and 35 g/ha, diclosulam + metolachlor at 25+1200,25+1800,35+1200 and 35+1800 g/ha, metolachlor at 1200,1800 and 2400 g/ha, and a tank mix of chlorimuron + lactofem at 1.5+96 g/ha used for comparison. A weedy and a weeded control were also included. Soybean seeds (BR-16 cultivar) were sowed December 5. 1996 and herbicides applied in the same day using a back sprayer, with four 110-02XP nozzles, operated at 2,45 kg/cm- to deliver 200 Ilha. Diclosulam and diclosulam + metolachlor at the smaller rates gave good control of S. rhombifolia, with no significant differences to the highest dosages. Metolachlor at 1800 and 2400 g/ha contralled about 80% of the weed. These results were significantly different frorn the results with diclosulam and diclosulam + metolochlor. Due to adverse climate condition in the area, chlorimuron + lactofen was applied when S. rhombifolia had 4-12 leaves and 5-25 em high. After 49 days chlorimuron + lactofen had controlled 80% of S. rhombifolia, wich was equal to metolachlor (2400 g/ha) results. Diclosulam and diclosulam + metolachlor gave less than 5% toxicity to soybean. lt was concluded that diclosulam at 25 g/ha and diclosulam + metolachlor at 25+ 1200 g/ha gave good control of S. rhombifolia.
Chemical management of Pilea microphylla in orchid seedlings
Orchidaceae species are produced on a large scale for commercialization of its flowers. However, because of its slow development, the substrate is subject to weed infestation, such as brilhantina (Pilea microphylla). Thus, we aimed to evaluate the selectivity of herbicides to the orchid seedlings of genre Rhynchostylis ([Rhynchostylis gigantea Alba x Rhynchostylis gigantea] X Rhynchostylis gigantea Semi-Alba) and control of P. microphylla. A completely randomized design with four replicates per treatment was adopted. The herbicides studied were oxyfluorfen (0, 120, 240, and 480 g ha-1 a.i.), flumioxazin (0, 12.5, 25 and, 40 g ha-1 a.i.), nicosulfuron (0, 20, 40, and 80 g ha-1 a.i.), and mesotrione (0, 96, 144, and 192 g ha-1 a.i.), with a control without application for each molecule. At the time of spraying, the plants of orchid presented four leaves and were 5 cm high, while P. microphylla was 10 cm high. Nicosulfuron did not control P. microphylla, while oxyfluorfen and flumioxazin showed control levels exceeding 90% on 14 days after application (DAA). The mesotrione showed low ability to control the weed, reaching around 35% efficiency at 49 DAA. All herbicides were selective to the hybrid seedlings Rhynchostylis. The oxyfluorfen and flumioxazin molecules were efficient in controlling P. microphylla in the tested dose ranges.
Influence of glyphosate herbicide in the weed community in the agricultural region of Rio Verde, Goiás
The increasing use of glyphosate in Brazil has increased the selection pressure on species of weeds tolerant and resistant to this herbicide. This study aimed to evaluate the influence of glyphosate use pattern in the population dynamics of weeds in soybeans in thirty-five sampling areas of different properties. These areas were classified as to the number of applications and equivalent amount of glyphosate acid. We used the square-inventory method in thirty-five sampling areas in the 2012/2013 harvest. The structural parameters relative frequency, abundance and value indicator of individuals number and dry weight of shoot were calculated. The graphical representation of the differences of the floristic composition was performed by the non-metric multidimensional scaling technique, with distances of Sorensen. The multi response permutation procedures test was used to test hypotheses of differences in floristic composition. The occurrence of typical species of each treatment was evaluated by the indicator value using the Monte Carlo test (p<0,05). The floristic composition of the number of plants differ between areas using average standards of glyphosate (six applications or 6001 to 8000 g ha-1 of acid equivalent) compared to very low standard areas (four or five applications or 2000 to 4000 g ha-1 of a.i.). The Gnaphalium coarctatum, Eugenia sp., Rumex acetosella and Spermacoce latifolia, Digitaria horizontalis, Urochloa decumbens, Panicum maximum, Gossypum hirsutum and Indigofera hirsuta species showed significant indicator value of environments with different levels of use of glyphosate. Different glyphosate usage patterns exerted influence on the floristic composition of weeds in soybean areas evaluated.
Sub-doses of 2-chloroethylphosphonic acid in vegetative stages of corn cultivation
The use of ripeners has been common practice in sugarcane cultivation. The application of these products is often performed through aerial spraying, which increases the chances of molecules from the ripener drifting into other crops, such as corn. With the aim of studying possible phytointoxication in corn caused by ethephon drift, a field experiment was conducted in order to evaluate the effect of ripener sub-dosing when applied in the V4 and V8 development stages of corn cultivation. The experiment was set up in a randomized block design, with four replications. Treatments were arranged in a 2 x 5 factorial scheme, with first factor corresponding to the corn growth stages in which the ripener was applied (V4 and V8), and the second factor referred to the ethephon sub-doses (0; 14.26; 28.51; 42.77, and 57.02 g ha-1 a.i.). Visual phytotoxicity effects were not perceptible when sub-doses were applied in the V4 and V8 corn growth stages. Similarly, agronomic characteristics and grain yield were not altered by ethephon sub-doses of up to 57.02 g ha-1 a.i.
Chemical control of Talinum paniculatum in three stages of development
Talinum paniculatum is a species of the Portulacacea family, popularly known as “maria-gorda”, weed in crops such as sugarcane, common bean, soybean, corn and carrot, as well as in non-agricultural areas. This work aimed to study the efficacy of herbicides in the control of T. paniculatum, as well as its effect on fresh and dry mass of these plants in three stages of development. The experimental design was completely randomized, with nine treatments and four replications, positioned in three stages: 4-6 leaves, 10-12 leaves and flowering. To evaluate the effectiveness of the treatments, the percentage of the control of plants was evaluated, in addition to its fresh and dry mass. There was higher control for some treatments within the development stages of weeds, with application of isoxaflutole, diuron+hexazinone, ametryn, and imazapic in the first stage, glyphosate at the dose of 2000 g a.e. ha-1, diuron+hexazinone and 2,4-D in the second stage, and 2,4-D, glyphosate at 2000 g a.e. ha-1, and ammonium-glufosinate in the third stage. Fresh and dry mass of weeds were affected, following the behavior obtained for the evaluations of control. The use of herbicides was efficient in the minority of arrangements tested for control of T. paniculatum. The development stage of the plant was influenced by the efficacy control of treatments.
Desiccants application season in pre-emergence in conventional soybeans
The weed management in soybean cultures stands out as an important tool to ensure its high yield potential. The direct tillage advent increased the importance of management performed in the soybean off season and pre-seeding, in order to avoid the weeds interference in the initial cultivation period. The survey was conducted in order to evaluate the weeds control and the agronomic performance of conventional soybean, using different desiccant herbicides. The experiment was conducted in randomized blocks design with four replications. Treatments were arranged in factorial 4x3, the first factor being the glyphosate herbicides application - diisopropylamine salt; glyphosate - potassium salt, glyphosate isopropylamine- salt + 2,4-D; and paraquat + diuron, the second factor the application time periods (13 and 7 days before seeding - DBS; and 1 day after seeding - DAS). The percentage of weed control, booth, seedling emergence, plants height, number of pods, mass of hundred seeds and productivity were evaluated. Only the management desiccation with glyphosate near the seeding time showed a decrease in the weeds control percentage, the glyphosate + 2,4-D use led to a decrease in the early crop growth, due to seeding proximity, the paraquat + diuron application near the seeding season caused a lower insertion of the first pod in the culture. There were no significant differences between treatments for soybean production components under these experimental conditions.
Aspects of the mechanism of action of the ammonium glufosinate: resistant crops and resistance of weeds
With the release of genetically modified organisms for tolerance of the non-selective herbicide ammonium-glufosinate in Brazil, along with its importance as an alternative herbicide to glyphosate-resistant weed, the knowledge of certain aspects related to its mode of action, chemical features and rational management become necessary. In this context, the present literature review was idealized in an attempt to cover, in the light of the current knowledge, some concepts about the biochemistry related to the mode of action of this herbicide, its uptake dynamics, its usage in GM plants and its rational management, with the purpose of making it last as long as possible in the agriculture systems.
Screening and dose-response of herbicides to mauve and jute
The production of mauve (Urena lobata) and jute (Corchorus capsularis) fiber is demanded by the industry as a raw material in the production of canvas, ropes, book covers and other applications. The production cycle of this fiber is a sustainable activity because it uses renewable resources of the floodplains of the Solimões River in the Amazonas state. The crop management combined with weed control are conditions for the species to express the maximum productive potential. The use of selective herbicides constitutes an efficient and economically viable alternative for this purpose. The objective of this research was to evaluate the selectivity of herbicides through screening and dose-response for these two species producers of natural fibers. Two experiments were conducted in a greenhouse: the first, in the form of screening to assess herbicides applied in post-emergence as bentazon, clethodim, fluazifop-p-butyl, fomesafen, linuron, oxyfluorfen, and sulfentrazone at recommended doses for other crops; and the second, the herbicides clethodim and fluazifop-p-butyl that were selective to jute and mauve, in 7 doses. The herbicides bentazon, linuron, fomesafen, oxyfluorfen, and sulfentrazone caused death of all plants while clethodim and fluazifop-p-butyl were moderately phytotoxic. The two species were more tolerant to fluazifop-p-butyl than to clethodim.
Effectiveness of herbicides in weed control and selectivity in Runner IAC 886 peanut crop
It was aimed to verify the efficacy and selectivity of herbicides applied alone or in tank mixture for the weed control in peanut crop cv Runner IAC 886. Therefore, it was settled a field experiment, in a randomized block design with four replications. The treatments applied in pre-emergence were: 1-imazapic, 3-imazapic + pendimethalin, and 5-imazapic + trifluralin; the treatments applied in post-emergence were: 2-imazapic, 4-imazapic + pendimethalin, and 10-imazapic + (bentazon + paraquat); and treatments with application in PRE followed by POST were: 6-trifluralin and imazapic, 7-trifluralin and bentazon, 8-trifluralin and 2,4-D, 9-imazapic and bentazon + paraquat; besides the checks with and without weeding (treatments 11 and 12, respectively). It were evaluated the efficacy of herbicides and symptoms of intoxication in peanut plants by visual evaluations at 7, 14, 21, 28, 45, and 90 days after application, and, after the harvest, the pods yields. Treatments 2, 3, 4, 5, 6, 7, and 8 had no significant reduction in peanut productivity. Treatment 10 was the least effective in controlling weeds and presented yields 47.3% lower than treatment 3 and 51.2% lower than the weeded control. It is concluded that for a weed community composed mainly of Cenchrus echinatus, Acanthospermum hispidum, Amaranthus deflexus, Parthenium hysterophorus, Alternanthera tenella, and Eleusine indica, the best weed control was obtained by imazapic in post-emergence. The application of imazapic + (bentazon + paraquat) in post-emergence was not effective in controlling weeds, resulting in yield losses.
Management of Merremia aegyptia with mixtures of herbicides under different rainfall simulation and in in the presence and absence of sugarcane straw
The high frequency of M. aegyptia in sugarcane harvested mechanically is related to its adapting behavior to this harvesting system, what resulted in an increased the infestation potential of this species in relation to other weeds. The aim of this study was to evaluate the management M. aegyptia by spraying pre-emergence herbicides, in the presence and absence of straw in clay soil, under different rainfall simulation. Two experiments were carried out in a completely randomized design with four replications. In each experiment was evaluated the mixtures of herbicides: mesotrione + atrazine (0.25 + 3.0 L ai ha-1) and diuron + hexazinone + sulfometuron-methyl (1386 + 391 + 33.35 g i ha-1). The treatments were arranged in factorial 8 x 2 x 2 design, composed by eight evaluated depths (0, 5, 10, 15, 20, 25, 30 and 35 cm), two covers (with or without straw) and two rainfall simulation after herbicide application (20 and 40 mm). Herbicides were applied to columns filled with clay soil and with 0 and 10 t ha-1 of straw coverage. After herbicide application, the columns were placed under simulated rainfall during the time necessary to apply the equivalent of 20 and 40 mm of rain. After this process, the columns remained for 72 hours in the horizontal position and opened longitudinally to sowing M. aegyptia (target plant). Mesotrione + atrazine presented, in greater depth (23 cm), control of M. aegyptia under 40 mm rainfall and the ineffective control under 20 mm of precipitation with or without straw. Diuron + hexazinone + sulfometuron had control until close to 15 cm depth in both rainfall simulations and the straw had little interference in the action of this mixture.
Ryegrass biotypes sensitivity to glyphosate, iodosulfuron-methyl and clethodim
Ryegrass (Lolium multiflorum) is an annual grass, traditionally used as forage that has become weed in crops in the south of Brazil. It has been observed that there are ryegrass biotypes resistant to glyphosate that survive the application of herbicides that inhibit ALS and ACCase. Therefore, the objective was to evaluate the sensitivity of different ryegrass biotypes to glyphosate, iodosulfuron-methyl and clethodim herbicides. The experiment was carried out in a greenhouse, in randomized blocks, in a triple factorial arrangement with three repetitions. Four ryegrass biotypes were used, where: biotype 1 (B1), susceptible to glyphosate; biotype 2 (B2), resistant to glyphosate; biotype 3 (B3) and biotype 4 (B4), biotypes suspected to be resistant to iodosulfuron-methyl. The doses were standardized in 0; 0.25; 0.5; 1; 2; 4 and 8 times the commercial doses of glyphosate (1080 g ha-1 a.i.) and clethodim (96 g ha-1 a.i.). The variables evaluated were control, in a percentage scale, and dry shoot biomass (DSB) of the plants at 28 days after the application of treatments (DAT). With that data, we calculated the parameters of the equation, from which the necessary dose was determined to reduce the DSB in 50% comparing to the non-treated plants (GR50) and the resistance factor (F). Biotypes B2, B3 and B4 obtained Resistance factors (F) above 10 comparing to glyphosate and iodosulfuron-methyl herbicides, B3 being the highlighted biotype because, besides being resistant to those two herbicides, also showed an F value close to the clethodim threshold, which can characterize a low resistance level to this herbicide. All biotypes, except the control one, were resistant to the iodosulfuron-methyl and glyphosate herbicides, which characterizes multiple resistance to those herbicides. The clethodim herbicide can be an alternative for the control of biotypes resistant to glyphosate and iodosulfuron-methyl; however, attention should be paid to the chemical handling of these populations, because we identified biotypes with low resistance level to this herbicide.
Efficiency and quality of glyphosate + carfentrazone application in controlling Commelina diffusa depending on the spray nozzles and Triunfo FlexTM adjuvant
The study aimed to evaluate the efficiency and the quality of technology application of the tank mixture of glyphosate + carfentrazone-ethyl in Commelina diffusa control. The experiment was conducted in plastic greenhouse and the experimental units were represented by vessels with four plants of C. diffusa. The experimental design was the entirely randomized, with nine treatments in a factorial scheme (4x2)+1, being four spray nozzles, (XR11002; DG11002; TT11002 and AI11002), two spray solutions of glyphosate + carfentrazone-ethy at 480 + 8 g ha-1 (with and without Triunfo FlexTM adjuvant at 0.05% v v-1) and a check without application. In the spray solution was added the FD&C-1 dye (1500 ppm), and applied over natural (15 replications of four leaves of C. diffusa) and artificial targets (4 replications of two plastic blades over the soil). The tracer quantification on the targets was realized by spectrophotometry, beyond evaluated the pH, static surface tension and conductivity of the solutions and control of C. diffusa at 5, 10 and 15 days after application. The Triunfo FlexTM adjuvant reduced the surface tension and the pH of carfentrazone-ethyl + glyphosate mixture. There was significant interaction between nozzles and glyphosate + carfentrazone-ethyl solution with the adjuvant for the deposit on the leaves of C. diffusa. With the exception of TT11002 model, the other nozzles promoted significant increase of the deposition on C. diffusa when combined with the adjuvant. For solution deposition in plastic blades the best performances were characterized by DG11002 nozzle with and without adjuvant and AI11002 nozzle with adjuvant. The initial control of C. diffusa with glyphosate + carfentrazone-ethyl was improved when associated with the adjuvant, mainly for AI11002 and TT11002 nozzles.
Effect of application time of sulfonylurea herbicides to control annual ryegrass in wheat crops
The adoption of weed management practices is one of the main tools that can contribute to increased grain yield in wheat crops. This study has aimed to evaluate the efficiency of the chemical group of the sulfonylurea herbicides, alone and in combination, at different times of the application, on the productivity of wheat cultivars, and control of annual ryegrass (Lolium multiflorum L.). The design was randomized blocks with 5 repetitions. The treatments were arranged in a 4 x 2 x 2 factorial design consisting in applying metsulfuron-methyl and iodosulfuron-methyl, alone and in combination, and control, using two commercial cultivars of wheat (Quartzo and BRS Tangará) in two application periods, 21 and 30 days after application. Cultivars phytointoxication, the level of control of annual ryegrass and the performance of agronomic traits of wheat crops were evaluated. For the control of annual ryegrass, it was found that there is a difference when using sulfonylurea herbicides, and iodosulfuron-methyl in use alone and in combination with metsulfuron-methyl is efficient in control. The application of iodosulfuron-methyl (5.0 g a.i. ha-1) and metsulfuron-methyl (2.4 g a.i. ha-1) + iodosulfuron-methyl (5.0 g a.i. ha-1) at 30 days after sowing resulted in higher productivity of wheat grains.
Influence of soil texture on selectivity of fomesafen applied in cotton pre-emergence
The selectivity of pre-emergence herbicides depend of the soil characteristics. In this context, the aim of this works was evaluated the fomesafen selectivity to cotton crop in soil with contrasting textural class. The experiment was performed under greenhouse conditions in completely randomized design, with five replications. The treatments were organized in factorial arrangement 5 x 2, with the first level representing five doses of fomesafen (0, 175, 350, 525 e 700 g ha-1) and the second factor two soils with contrasting texture: sandy loam texture (200 g kg-1 of clay, 40 g kg-1 of silt and 760g kg-1 of sand, pH de 4,47 e 1,59% de O.M.) and clayey (760 g kg-1 of clay, 110 g kg-1 of silt and 130g kg-1 of sand, pH 5,7 e 2,30% de O.M.). The evaluations performed were the number of emerged plants at 7 and 14 days after emergence (DAE), phytointoxication at 7, 14 and 21 DAE. At 35 DAE, it was collected the shoot and the roots of cotton plants to determined the shoot and roots dry mass. Fomesafen presented potential to be used for cotton, cultivar FM 993, however, the phytointoxication symptoms was very intense in plants treated with high doses in sandy loam soil. Thus, the fomesafen doses need to be adjusted according to the textural class, and the content of organic matter of the soil.
Physiological changes in tomato crop due to simulated drift of herbicides
The accidental drift can occur as a result of the herbicide application. However, little is known regarding the physiological changes in crops resulting from herbicide drift. The aim of the study was to evaluate the effects of simulated drift of glyphosate and clomazone in tomato. The experimental scheme was randomized and the treatments arranged in a factorial design, where factor A compared herbicides (glyphosate or clomazone) and factor B rates (0, 12.5, 25, 37.5 and 50% of the recommended rate). Content of total phenols, chlorophyll contents (a, b and total) and carotenoids, lipid peroxidation and electrolyte leakage were evaluated. Increasing rates of herbicides resulted in increased content of total phenols and electrolyte leakage in plants. Drift of herbicide glyphosate results in the reduction of photosynthetic pigments and causes higher lipid peroxidation of membranes in tomato, compared to clomazone. The accidental drift results in alteration in the metabolism of tomato plants, resulting in oxidative stress.
Weather conditions and application volumes in the desiccation of Urochloa ruziziensis and spontaneous vegetation
In the desiccation of the vegetation cover, failures are of common occurrence, resulting from insufficient deposition of herbicides. Thus, it becomes important to know the factors that may interfere in the application. The present work aimed to investigate the efficiency of the pulverization of spray volumes in different weather conditions. The applications were carried out during the day for desiccation of Urochloa ruziziensis and spontaneous vegetation for no-tillage establishment. It was adopted a randomized block design with four replications in a split plot scheme of 2 x 4. The plots consisted of application volumes (50 and 200 L ha-1); and the subplots consisted of different atmospheric conditions obtained by applying at different times (4:30, 10:30, 16:30 and 22:30 hours) throughout the same day. In the application, it was used a customized sprayer, pressurized by CO2 with the spray nozzle model 110015 TT generating mean drops. It was used glyphosate herbicide at a dose of 1.3 kg a.e. ha-1. At 5, 10, 15, and 20 days after herbicide application, it were performed visual assessments of the percentage of control of the vegetation cover. Weather conditions (air temperature, relative humidity, wind speed, and irradiance) found in the application schedules exerted no influence on the efficacy of the herbicide in control of U. ruziziensis in both application volumes. Reducing the spray volume had influence on the control effectiveness of the natural vegetation in all weather conditions where the herbicide was applied.
Droplets size categories and application volumes in burndown of plant covers
This study has aimed to verify the influence of the droplets size categories and application volumes on burn down Urochloa ruziziensis and Conyza sp. Therefore, two trials were conducted in a randomized block design with four replications in a 2x4 split plot arrangement. The plots consisted in droplets size categories (very fine droplets and ultra coarse droplets) and the subplots consisted in four application volumes (50, 100, 150 and 200 L ha-1). For desiccation, glyphosate herbicide was used at 0.975 and 1.3 kg of a.e. ha-1 for controlling plant covers Urochloa ruziziensis and Conyza sp., respectively. Saflufenacil herbicide was used at a dose of 49 g of a.i. ha-1 in association with glyphosate to control Conyza sp. In the application was used a pressurized sprayer by CO2 with spray nozzles model ATR 1.0 and AI 110015. At 5, 10, 15 and 20 days after application (DAA) of the herbicides, visual assessments were done of the control percentage of Urochloa ruziziensis and defoliation in Conyza sp. At 25 DAA, one regrowth percentage assessment of Conyza sp. plant was done. It is concluded that the category of ultra coarse droplets is efficient for desiccation of Urochloa ruziziensis with volumes of up to 50 L ha-1, while the category of very fine droplets reduces the efficacy with reduced volume application. It was also found that reducing the application volumes increases the possibility of regrowth on burn down Conyza sp.
The benefits of the Roundup Ready technology are expressive and the acceptance of this technology by farmers is undeniable, giving support to the rapid growth of RR2 corn. Recent studies indicate, however, that glyphosate applied in post-emergence in RR2 corn can eventually cause damage to plant development. Therefore, there are many speculations and questions that need to be clarified in the scientific and technical context glyphosate. Thus, it is necessary the search for information allowing to diagnose the real consequences of its use. And thus foster safer and sustainable positioning of this new technology, providing benefits to farmers related to proper weed management in different agroecosystems.
Selectivity of ethoxysulfuron to soybean and common bean
The emergence of soybean seeds in fields during the common bean cultivation can negatively affect the growth and yield of this crop. This problem can be minimized with the use of selective herbicides to common bean but non-selective to soybean. Aiming to define management strategies to voluntary soybean plants in the common beans crop, this research was carried out to evaluate the selectivity of ethoxysulfuron to soybean and common beans crops. Two experiments were conducted in a greenhouse, in randomized block design with four replications. Each experiment corresponded to a crop: soybean or common bean. Treatments were arranged in factorial arrangement 2x9, where the first factor corresponds to herbicide application single or in tank mixture with mineral oil Nimbus® at 0.5% v/v and the second was related to ethoxysulfuron doses (0, 1.8, 3.6, 5.4, 7.2, 9.0, 13.5, 18 and 36 g a.i. ha-1). At 7, 14, 21, and 28 days after application (DAA) was evaluated the visual intoxication, and at 35 DAA the leaf area and total plant dry matter. The ethoxysulfuron caused low intoxication to common bean plants, without interfering in leaf area and total plant dry matter. Soybean was sensitive to this herbicide, especially in higher doses and in the presence of mineral oil. The dose of 36 g a.i. ha-1 of ethoxysulfuron plus mineral oil caused the death of soybean plants without interfere in growing of common bean crop.
Desiccation of Brachiaria ruziziensis with paraquat before soybean sowing
Information regarding the desiccation of Brachiaria ruziziensis are scarce in the literature, especially with the use of contact action herbicides. The objective was to evaluate different doses and spray volumes of paraquat in the management of the desiccation of the foraging B. ruziziensis and the effects on soybean crop and weed suppression. The experimental design was completely randomized block with four replications. The treatments were arranged in a factorial scheme 4 x 6 + 1, corresponding to the evaluation of four doses of paraquat (100, 200, 400, and 800 g ha-1) in six spray volumes (67, 140, 199, 283, 323, and 396 L ha-1), besides a check without application. To study the population dynamics of the weeds was also used a control in fallow condition and another only with the crop without the presence of straw (weeded). It is concluded that the desiccation of B. ruziziensis with paraquat was effective to 7 days after application, being the highest efficiency obtained from the dose of 200 g ha-1, regardless of the spray volume used. From this period, the forage plants began a new cycle of growth and interfered negatively on soybean yield. The infestation of weeds was reduced in areas with B. ruziziensis in consortium with soybeans in relation to the fallow area.
Andréia Cristina Peres Rodrigues da Costa
Glyphosate and cotton growth regulator sub-doses systems application
In order to increase productivity levels, reduce costs and improve efficiency in mechanical harvesting, new technologies are being incorporated such as governor use of growth and application of sub-dose of glyphosate with promising hormetic effect on cotton plants. To do this, this study aims to evaluate the effect of the application of sub-dose of glyphosate and growth regulator system on cotton agronomic characteristics. The experimental design was randomized blocks in a factorial 6 x 2 + 1, with four replications, the first factor was frequency of application of glyphosate, using the same dose (78 g a.e. ha-1) in one single time 40 days after emergency (DAE), split in 2 times (at 40 and 50 DAE), in 3 times (40, 50 and 60 DAE), in 4 times (40, 50, 60 and 70 DAE) and 5 times (40, 50, 60, 70 and 80 DAE) , and the second factor was with and without the application of mepiquat chloride in the dose 1 L ha-1, with split spraying in 5 times, at 45, 55, 65, 75, 85 DAE, besides the control without application of products. It has been found that the use of mepiquat chloride reduced the plant height and the number of nodes of the stem. The split application of sub-dose of the herbicide in 3 times led to increased cotton yield compared to treatments without application.
Chemical management alternatives weed infests barley crop
Ryegrass is the main weed that infests barley, causing high yield losses and quality of grain. Thus, this work intended to evaluate the selectivity and efficacy of herbicides for weed control in barley. For such, we carried out an experiment in the field with randomized block design in factorial scheme 2 x 12, with four replications. Factor A is composed by the barley genotypes MN610 and Criola and factor B by herbicides: iodosulfuron imazethapyr + imazapic; clomazone; propanil; oxyfluorfen; metsulfuron-methyl; 2,4-D; cyhalofop; penoxsulam; were allocated pyroxsulam, weeded and infested. MN610 genotype showed high sensitivity to clomazone and imazethapyr + imazapic, with its yield components reduced in the presence of these products. Criola genotype presented itself with more tolerance to iodosulfuron, propanil, pyroxsulam, imazethapyr + imazapic, clomazone and oxyfluorfen because its yield components were lesser negatively affected by herbicides. The herbicides may cause, depending on the genotype, reduction in yield components of culture, which consequently affect the grain yield of barley. The herbicide that had the best response was iodosulfuron, keeping the crop free of weeds and combined with a lower phytotoxicity culture. The herbicide that had the best response was iodosulfuron, it kept the crop free of weeds with lowest phytotoxicity to culture.
Evaluation of wild poinsettia biotypes with suspicion of resistant to ALS and Protox inhibitors herbicides
The objective of the present study was to evaluate the confirmation of occurrence of wild poinsettia resistance, coming from Rondônia and Rio Grande do Sul, to herbicides with different mechanisms of action, and to determine the dose of herbicides required for 50% reduction in the dry mass of plants (GR50) and for the control of 50% of these plants in each experimental unit (C50). Therefore, an experiment was conducted over greenhouse conditions, in randomized block design with four replications. The herbicides used were: imazethapyr, chlorimuron-ethyl, cloransulam-methyl, saflufenacil, fomesafen, and carfentrazone-ethyl. The doses used were: 0; 0.5; 2; 8; 16; 32 and 64 times the commercial dose. The variables evaluated were control of wild poinsettia at 7, 14, 21, and 28 days after treatments (DAT), and also at 28 DAT was determined the dry mass of plants. The Rio Grande do Sul biotype showed sensitivity to the herbicides tested, at meantime the Rondônia biotype presented cross-resistance to ALS-inhibitors (imazethapyr, chlorimuron, and cloransulam), and susceptibility to PROTOX-inhibitors (carfentrazone, fomesafen, and saflufenacil).
Distribution, droplet diameter and phytotoxicity of herbicides applied in eucalyptus seedlings with air induction nozzles
The spray nozzles are responsible for the formation of droplets, each nozzle type exerts a different function, with its own characteristics related to the deposition of droplets according to the desired target. This study aimed to evaluate the distribution, droplet diameter and phytotoxicity of glyphosate and isoxaflutole herbicides applied in eucalyptus seedlings with air induction nozzles (AIUB 04 and TTI 110 04). The spectrum of droplet diameter was determined by particle size analyzer by laser light diffraction. The volumetric distribution was evaluated in deposition table to collect the sprayed volume. The visual assessments of phytotoxicity of the herbicides were carried out at 7, 14, 21, and 28 days after application. At the end of the experiment it was determined the dry mass of stem and leaves. The TTI 110 04 nozzle had greater volumetric median diameter (VMD), lower percentage of droplets smaller than 100 µm and lower uniformity coefficient of drops compared to the AIUB 04 nozzle. For the spray nozzle model TTI 110 04, the spacings of 0.45 and 0.75 cm showed better uniformity (variation coefficient lower than 10%). The model AIUB 04 resulted in no acceptable coefficient of variation. The application of glyphosate with the AIUB 04 nozzle increased phytotoxicity. The herbicide isoxaflutole was shown to be selective to eucalyptus.
Tolerance of two cotton varieties to herbicides applied in pre-emergence
This work aimed to evaluate the selectivity of herbicides applied pre-emergence, isolated or in tank-mixtures, for two cotton varieties, Delta-Opal and FMT-701. Treatments applied were: alachlor, S-metolachlor, diuron (two rates), prometryn (two rates), oxyfluorfen, alachlor + diuron, alachlor + prometryn (two rates of this mixture), S-metolachlor + diuron, S-metolachlor + prometryn (two rates of this mixture), oxyfluorfen + diuron, oxyfluorfen + prometryn. Evaluations performed were related to the visual plant intoxication, height of plants and crop yield. When rates of diuron and prometryn were increased, symptoms of crop injury were also more evident, in relation to lower rates of the same products. Oxyfluorfen, isolated or in tank mixture with diuron or prometryn propitiated intense symptoms of crop injury, but the only treatment which was considered as non-selective for both cotton varieties was the mixture of oxyfluorfen + prometryn (0.192 + 0.9 kg ha-1).
Paraquat doses and spray volumes in desiccation Brachiaria ruziziensis before planting off-season maize
Brachiaria ruziziensis can contribute to the consolidation of the no-tillage system due to high production of biomass that can be used in integrated management of weeds. However, there is little information regarding the desiccation of this forage, particularly with the use of contact action herbicides. The present work aimed to evaluate the different management methods of desiccation of B. ruziziensis, and the effect in second season maize crop and weed suppression. The experimental design was a randomized complete block design with four replications. The treatments were arranged in a factorial 4 x 6 + 1, corresponding to evaluation of four doses of paraquat (100, 200, 400, and 800 g ha-1), six spraying volumes (69, 138, 204, 273, 342, and 411 L ha-1), and an untreated control. To study the population dynamics of weeds a control was also used in fallow condition and another with only the crop, without the presence of straw (weeded). The spray nozzle used was Turbo TeeJet simple plan jet with angulation of 90°. The paraquat was efficient in desiccation B. ruziziensis up to 14 days after application. After this period there was regrowth of forage plants interfered negatively on maize yiled. The weed infestation was reduced in areas with B. ruziziensis in crop rotation with maize in relation to fallowing areas.
Selectivity of residual herbicides and mixture with glyphosate applied after the pruning of cassava ‘Fécula Branca’
Cassava varieties (Manihot esculenta L. Crantz) intended for industrial starch manufacturers are usually pruned during the period of physiological rest of the plants, requiring the adoption of management practices to prevent weed competition in the second cycle of crop development. The objective was to evaluate the selectivity of pre-emergent herbicides applied alone or in tank mix with glyphosate in applications after pruning of cassava 'Fécula Branca'. The experimental design was a randomized block with four replications. The treatments were: glyphosate (720 g ha-1), carfentrazone (25 g ha-1), chlorimuron-ethyl (10 g ha-1), clomazone (1,080 g ha-1), flumioxazin (83 g ha-1), metribuzin (480 g ha-1) metsulfuron-methyl (2.4 g ha-1), glyphosate + carfentrazone (720 + 25 g ha-1), glyphosate + chlorimuron-ethyl (720 + 10 g ha-1), glyphosate + clomazone (720 + 1080 g ha-1), glyphosate + flumioxazin (720 + 83 g ha-1), glyphosate + metribuzin (720 + 480 g ha-1), glyphosate + metsulfuron-methyl (720 + 2.4 g ha-1), and an untreated control. Evaluations included percentage of phytotoxicity, plant height, root yield and starch content of cassava. The herbicides applied alone and in tank mix did not cause phytotoxicity in cassava plants after application. The herbicides applied alone and in tank mix did not reduce plant height, root yield and starch content of cassava compared to untreated control. The isolated application of residual herbicides and mixes with glyphosate were considered selective when applied after pruning of cassava plants 'Fécula Branca'.
Tolerance of sunflower to herbicide application in post-emergence
The most used method in weed control is chemical, though, the sunflower is very sensitive, especially the post-emergent herbicides that control dicotyledonous weed species. Thus, the aim of this work was to evaluate the tolerance of sunflower to different herbicides as well as to evaluate the effect of these products on physiological characteristics of sunflower plants. For this, we assembled an experiment conducted in a greenhouse. We used a completely randomized design with five replications. The treatments consisted of 10 herbicides applied in post-emergence of sunflower plants and a check without herbicide. The check was used to evaluate the growth and physiological characteristics of sunflower plants. The herbicides interfered variously in sunflower plants, and the crop appears more tolerant to flumioxazin herbicide, fenoxaprop-p-ethyl + clethodim, haloxyfop-p-methyl, fluazifop-p-buthyl and clethodim regarding related variables or sunflower growth, highlighting that these herbicides cited caused lesser degree of intoxication had on the culture. In assessing the physiological characteristics, fomesafen, the mixture (fluazifop-p-buthyl + fomesafen) and chlorimuron-ethyl stand out with the most harmful to culture, adversely affecting A, gs, E and ΔC plants treated with these products.
Alteration of period before the interference of soybean on presence of volunteer corn
The aim of this work was to characterize the onset of weed interference in two soybean cultivars, with different growth cycle, under two conditions of corn plants infestation. The experimental design was split plot design composed by two factors: periods of coexistence of soybean with corn (no coexistence, coexistence during 14, 28 and 42 days after sowing (DAS) and throughout the soybean cycle) and two corn densities: 10 plants m-2 and 30 plants m-2. The cultivar Fundacep 63RR had its growth altered in period equal or longer than 42 DAS with no relation to corn populations. The reduction in grain yield of soybean occurred at 28 DAS for 10 plants m-2 density and 14 DAS for 30 plants m-2. The cultivar Fundacep 59RR changed its morphological characteristics in period equal or longer than 28 DAS. With 30 plants m-2 of corn the height and number of soybean branches changed at 60 DAP. For the same cultivar, the yield loss started at 42 DAS for 10 plants m-2 of corn and 28 DAP for 30 plants m-2.
Potencialization of mesotrione efficiency in tank mixture with inhibiting of Photosystem II by distinct absorption pathways of crabgrass
With the objective of evaluating the potencialization efficiency of mesotrione in tank mixture with inhibitors Photosystem II in Digitaria horizontalis control, four experiments were conducted in plastic greenhouses belonging to Superior School of Agronomy of Paraguaçu Paulista County, São Paulo State, being used a Latosoil with sandy texture. The experimental design of four experiments was entirely randomized, with 10 treatments and 5 replications, in factorial scheme 3x3+1, being considered the contrast between mesotrione (96 g ha-1) and inhibitors of the Photosystem II herbicide (ametryn, 1500 g ha-1; metribuzin, 1440 g ha-1; diuron + hexazinone, 936+264 g ha-1 and atrazine, 2000 g ha-1) products, isolated and in tank mixture for three absorption conditions and a check. The absorption conditions were constituted by the isolation and/or partial exhibition of target seedling of D. horizontalis (3 to 6 leaves) in relation to deposition of pulverizations for the modalities: a) seedlings protected with plastic tubes in discovered soil (root absorption pathway); (b) unprotected seedlings in soil covered with aluminum sheet (leaf absorption pathway); (c) seedlings and soil submitted to deposition of the herbicides (absorption roots + leaves pathways) and (d) check. The largest synergism levels obtained for D. horizontalis control were registered to root absorption and leaf + root of the tank mixture with mesotrione + atrazine, as well as for leaf absorption and leaf + root of mesotrione + diuron + hexazinone from the 3 to the 7 DAA (days after application) and of mesotrione + ametryn starting from 7 DAA, both characterized by reduction of control initial time in reaching great levels (≥ 90%). Antagonistic effects were not verified for the tank mixtures.
Urochloa plantaginea control with residual herbicides and agronomic performance of two bean cultivars
The objective of this study was to evaluate the effects of the use of residual herbicides applied in the pre-emergence of beans, on reducing weed infestations, and the agronomic performance of the crop. Two field experiments were conducted, one had the cultivar UFT -06 (Carioca Group, short cycle and erect) and another, the IPR Graúna (Black Group, long cycle, prostrate habit). The treatments consisted of application of the herbicides pendimethalin (1.2 and 1.4 kg ha-1) and trifluralin (1.2 and 1.4 kg ha-1); and dimethenamid (1.4 and 1.6 kg ha-1) and S-metolachlor (1.4 and 1.6 kg ha-1), and weedy and weed-free checks for comparison. In the experimental areas, Urochloa plantaginea (Alexander grass) infestation predominated. It was evaluated the density and the biomass of this weed, and the number of pods and yield of the bean. Trifluralin was the herbicide that most reduced the infestation of the weeds and increased the yield of the bean, when compared to the other products. The UTF-06 bean cv. was more competitive with U. plantaginea than IPR Graúna. The treatments with herbicide reduced the infestation of weed, but this did not result in higher yields of bean, compared to the weed-free treatment.
Herbicides effect on microbial activity of soil cultivated with different genotypes sugarcane
We aimed with this work to evaluate the effects of herbicides on microbial activity of soils planted with sugarcane. The experiment was installed in a randomized blocks design in a factorial scheme 5 x 4 with four replications. Factor A was composed by sugarcane genotypes (RB72454, RB835486, RB855113, RB867515 and RB947520) and B corresponded to the herbicides (ametryn, trifloxysulfuron-sodium and the formulated mixture ametryn + trifloxysulfuron-sodium), and a no herbicide control. At 15 and 45 days after herbicide application (DAT), the rhizospheric soil was collected for determination of the basal respiration (C-CO2), microbial biomass carbon (MBC) and the metabolic quotient (qCO2). Herbicide effects on soil microbiote varied with sugarcane genotype. RB835486 was the one which most affected MBC mainly at 45 DAT, and qCO2 was most affected by RB72454. For herbicides, especially trifloxysulfuron-sodium, there was change in MBC as herbicide dose increased for most genotypes, which also promoted reduction on qCO2 proving this herbicide to be the one with greatest impact on micro-biological indicators of soils. The herbicides ametryn and mixture ametryn + trifloxysulfuron-sodium negatively affect the C-CO2, and the CBM qCO2, in particular when applied on the genotype RB72454.
Efficiency of the application of the mixture of glyphosate with saflufenacil on Brachiaria decumbens plants
The aim of this work was to investigate the synergism or antagonism of glyphosate with and without mixing with saflufenacil to control B. decumbens. The following treatments were evaluated: glyphosate (1.080); glyphosate + saflufenacil + Dash (1,080 + 24.5 + 0.5 % v/v); glyphosate + 2,4-D (1,080 + 720); glyphosate (1,440); glyphosate + saflufenacil + Dash (1,440 + 24.5 + 0.5% v/v); glyphosate + 2,4-D (1,440 + 720); saflufenacil + Dash (24.5 + 0.5 v/v); 2,4-D (720), doses in g a.i./e.a. ha-1. The efficiency control of Brachiaria decumbens was evaluated at different times: 3, 7, 14, 21, 28, 35, 42 and 49 days after application (DAA), with basis on phytotoxicity symptoms, using the scale of 0 % to 100%. The results were submitted to the F test and the average values were compared using Tukey test at 5 % probability. The herbicide glyphosate applied isolated at both tested doses, or mixed with saflufenacil, provided excellent control of B. decumbens after 14 days. Saflufenacil and 2,4-D when applied isolated without the presence of glyphosate were ineffective in controlling plants. The control of B. decumbens provided by mixtures of glyphosate with 2,4-D and saflufenacil was similar to the application of glyphosate isolated. Mixtures showed no synergism or antagonism on the control of B. decumbens plants.
Selectivity of post-emergence herbicides to crambe
Crambe is a dedicated oilseed crop suitable for production of industrial feedstocks. Due to the lack of information of post-emergent herbicides, the aim of this study was to evaluate the selectivity of post-emergence herbicides to crambe. The experiment was conducted in Maracaju, MS, Brazil, in 2013. Clethodim (120 g ha-1 a.i.), haloxyfop-p-methyl (63.35 g ha-1 a.i.), fomesafen + fluazifop-p-butil (125 + 125 g ha-1 a.i.), fomesafen + fluazifop-p-butil (187.5 + 187.5 g ha-1 a.i.), nicosulfuron (45 g ha-1 a.i.) herbicides without and with mineral oil, and a control without herbicide application were assessed. Evaluations were performed 7, 14, 21 and 28 days after herbicide application based on the percentage of crambe plants with visual phytotoxicity, on the percentage of dead plants caused by herbicides, and the grain yield. In general, mineral oil increased the phytotoxic effects of herbicides on crambe plants when sprayed post-emergence. The mineral oil addition to haloxyfop-p-methyl increased the phytotoxicity to crambe plants. The herbicide fomesafen + fluazifop-p-butil and nicosulfuron were harmful to crambe plants with or without mineral oil, and clethodim (with and without mineral oil) and haloxyfop-p-methyl (without mineral oil) were harmless to crambe plants and can be used on post-emergence.
Selectivity of herbicides for sugarcane Plene® system in pre and post-emergence
The Plene® system is a new cane planting technology that came to simplify and streamline the initial phase of planting, since it employs mini-stalks previously treated. However, there is a lack of information on the selectivity of herbicides in this new system and, due to this, it was aimed to evaluate the phytotoxicity of herbicides commonly used in the traditional cultivation of sugarcane for the control in pre-and post-emergence of weeds when employed in Plene® system. Two experiments have been developed, one with application in pre-emergence and another with post-emergence. In both experiments it were planted two stalks per pot (5 L), previously filled with mixture composed of four parts of soil (extracted from the arable layer of Red Oxisol) and one portion of filter cake. After planting the first experiment, it was performed herbicide applications in pre-emergence (imazapic, sulfentrazone, ametryn, isoxaflutole, tebuthiuron, amicarbazone, mesotrione, and a check without application). For the second experiment, the applications of herbicides in post-emergence were performed at 14 days after plant emergence, and the treatments consisted of sulfentrazone, ametryn, isoxaflutole, amicarbazone, ametryn + clomazone, diuron + hexazinone, and a check without application. Treatments phytotoxicity evaluations were performed using visual scale. At the end of the experiments, it was conducted evaluations of plant height, number of tillers and leaves. In addition, it was determined the dry mass of leaves, stem, root, tholes, and it was recorded the number of regrowth in each pot after ten days of the cane plant cutting. The herbicides sulfentrazone, ametryn, tebuthiuron, amicarbazone, and mesotrione were selective to sugarcane 'SP81-3250' in Plene® system when applied in pre-emergence, while ametryn, sulfentrazone, ametryn + clomazone, and diuron + hexazinone (468 g kg-1 + 132 g kg-1) were selective for post-emergence.
Aminocyclopyrachlor and indaziflam: Selectivity, control and fate in the environment
Aminocyclopyrachlor and indaziflam are two new molecules that are currently under development in Brazil. Aminocyclopyrachlor is an auxinic herbicide, and indaziflam acts in the biosynthesis of cell wall and both herbicides are expected to have great potential for pre-emergence weed control. Aminocyclopyrachlor is selective to the species belonging to the Poaceae family, while indaziflam is less selective for annual crops, and is under development for perennial crops. Although the two herbicides pose distinct properties related to sorption to soil, both present positive correlation between sorption and organic matter contents. The long persistence of residual activity in soil of these two molecules requires that they be used with caution, because of their carryover potential.
Herbicides residues in water bodies - a review
Herbicides are the most important pesticides in the world and essential for food production. They are synthesized to affect plants but on the other hand can cause negative impact to non-target organisms in case of contamination of aquatic environments. Thus, monitor the loss of herbicides to aquatic environments is an indispensable assignment to practice a sustainable agriculture, especially in Brazil: the most important pesticide user in the world, one of the largest food producers and watershed holder. The purpose of the text is to present technical factors, operational, edaphoclimatic, physical and chemical of the herbicides and laws about water sources contamination by it. In addition, results of works that monitored herbicides in Brazilians water bodies and the main techniques for detection and quantification of these products also will be presented. Due to the importance of Brazil on the world stage, with respect to food production, studies related to the monitoring of herbicides in water sources should be developed more frequently, especially with respect to countries that have agriculture developed over time.
Efficacy of Haloxyfop R (GR-142) herbicide isolated and associated to 2.4-D in maize hybrids RR® volunteer control
The volunteer corn Roundup Ready® has been effective managed by ACCase graminicides as burndown prior to sowing soybean. However, before crop installation, there are other glyphosate-tolerant weeds in the field such as Conyza sp., Commelina sp., Ipomoea sp., Spermacoce latifolia and Richardia brasiliensis. Thus, the tank mixture of ACCase inhibitor herbicides with 2.4-D, is increasing in this segment. The present study evaluated the efficacy of Haloxyfop (GF-142) isolated and with 2.4-D (DMA 806 BR®) to volunteer corn control sprayed at different stages. One trial was conducted in field conditions with the corn RR® hybrids as DKB240PRO 2, AG8025RR2, Pioneer30F53HR and AG9045RR2 using a randomized block design in a split-plot factorial 8x2+1 with four replications. The main factor was the rate of haloxyfop GF-142 (25, 50 and 62 g a.i. ha-1) and clethodim (84 g a.i. ha-1) with or without the herbicide 2.4-D (670 g a.e. ha-1). The second factor was the application on volunteer corn stage at V5 and V7. The herbicide GR-142 at 25, 50 and 62 g a.i. ha-1, alone or with 2.4-D, was effective to control the volunteer corn plant hybrids DKB 240 PRO2, RR2 AG 8025, AG 9045 and RR2 Pioneer 30F53HR at both V5 and V7 stages. The same result was observed with the standard clethodim, alone and mixed with 2.4-D. However, the control at the V7 stage was slight slower than at the V5 stage.
Efficiency of herbicides in suppressing regrowth of sourgrass clumps
Sourgrass (Digitaria insularis) is a species native to the Americas, in tropical and subtropical regions. In areas where there is continuous use of glyphosate, plants develop clumps with rhizomes and become difficult to control, leading to the possibility of occurring regrowth after the herbicide treatments. This study evaluated the efficacy of different herbicide treatments to suppress the regrowth of D. insularis. The experiment was conducted in Nova Aurora – PR, from July to August 2013. The treatments were check (no herbicide), glyphosate + clethodim, glyphosate + imazethapyr + clethodim and glyphosate + s-metolachlor. We used a CO2 precision sprayer fitted with tips with flat fan nozzles ADIA 110.02. Evaluations were performed at 21, 28 and 35 days after application (DAA). The results showed that all treatments were suitable in suppressing regrowth of D. insularis, compared to no a played plants.
Alternative herbicides to control Raphanus raphanistrum L. resistant to metsulfuron methyl herbicide
The control of weeds in winter crops is done primarily with ALS-inhibitor herbicides. The intensive herbicide use in areas with wheat has provided selection pressure on R. raphanistrum resulting in biotypes resistant to these herbicides. The objective of this work was to determine the existence of cross and multiple resistance to ALS-inhibitors herbicides and alternatives to chemical control of this weed resistant to metsulfuron methyl. Treatments consisted of R. raphanistrum resistant (biotype R) and susceptible (biotypes S), with 12 herbicides: glyphosate, atrazine, bentazone, 2,4-D, sulfometuron methyl + chlorimuron ethyl, chlorimuron ethyl, cloransulam methyl, iodosulfuron methyl, nicossulfuron, imazethapyr, metsulfuron methyl, imazapic + imazapyr and a control without herbicide. It was applied the recommended dose of each herbicide at 3 to 4 true leaves stage. Control efficiency and reduction in dry matter of shoots were analyzed. The biotype S was susceptible to all herbicides used in the study. The biotype R has cross resistance to herbicides that belong to chemical group’s imidazolinones, sulfonylureas and triazolopyrimidines varying degree of sensitivity between these groups. The biotype R was not diagnosed with multiple resistance and glyphosate, bentazone, atrazine and 2,4-D shown to be effective in controlling biotype R and can be used for chemical management of R. raphanistrum.
Effect of herbicides applied as direct spray in the initial development of jatropha plants
The objective was to evaluate the effect of glyphosate, paraquat and glufosinate-ammonium applied as directed spray in initial development of jatropha plants. A randomized block design was used, with five replicates. The treatments consisted of glyphosate (180, 360, 720 and 1,440 g ha-1), paraquat (100, 200, 400 and 800 g ha-1) and glufosinate-ammonium (125, 250, 500 and 1,000 g ha-1) and a control (no application). Herbicide application was performed at 145 days after sowing, with spraying directed to the lower third middle of the plants. The rates glyphosate provided average phytointoxication of 2.4% and no reduction in leaf area, however, there was an average reduction of 9.0% of dry weight at 35 days after application (DAA). Paraquat, for rates ≤ 200 g ha-1, phytointoxication was lower than 20% to 35 DAA, however, there was a reduction in leaf area and plant dry mass of 47.0 and 18.2%, respectively. The rate of 125 g ha-1 glufosinate-ammonium was the one that gave the lowest values of phytointoxication (<20.0%), reduction in leaf area (2.7%) and dry mass (10.5%) plants up to 35 DAA. It was concluded that the contact of paraquat and glufosinate-ammonium with stems and lower leaves may impair the initial development of jatropha. However, application of glyphosate direct spray did not impair the initial development of jatropha, regardless of the rate used.
Alternatives to chemical scavenging of clumps of guinea grass and signal grass clumps in sugarcane ratoon
In sugarcane areas of Parana State, Panicum maximum (guinea grass) and Brachiaria decumbens (signal grass) stand out as weeds with difficult control and may compromise the useful period sugar cane crop. This research aimed to evaluate alternatives to chemical scavenging of P. maximum and B. decumbens clumps in sugar cane crop. This way, two experiments were conducted in field conditions by using a complete randomized block design with four replications for the first and five for the second one. In the first experiment, hexazinone and diuron + hexazinone herbicides were evaluated at 0, 10, 11.7, 13.3, 15 and 16.7% concentrations. In the second one, isoxaflutole herbicide was used at 0, 1.5, 3.0 and 4.5% concentrations. Visual control evaluations were performed at 4, 10, 20 and 30 days after treatments application. Diuron + hexazinone and hexazinone herbicides were effective in controlling P. maximum and B. decumbens at 10% concentration. Regarding to isoxaflutole, it was necessary a minimum concentration of 4.8 and 4.2% for maximum efficiency control of P. maximum and B. decumbens sprouting, respectively.
Efficiency and deposition of paraquat application with adjuvant and nozzles inclination angle over Digitaria spp., Sonchus oleraceos and Amaranthus viridis
The use of contact action herbicides with paraquat usually requires more attention with application technology aspects in relation to the systemic action ones. In order to evaluate the efficiency and deposition of paraquat application associated with adjuvant and nozzles inclination angle in weeds control, an experiment was conducted in field conditions using a factorial scheme 2 x 3 +1, with five repetitions. Seven treatments were constituted by two conditions of Gramoxone® herbicide (paraquat, 150 g a.e. ha-1), used with Agral® (0.1% v/v) and Fulltec® (0.05% v/v;) adjuvant, three nozzles inclination angle in direction of application offset (+30°; 90°; -30°) and a check without application. Natural targets were Digitaria spp., Sonchus oleraceos and Amaranthus viridis and artificial targets, plastic covers positioned over soil surface, with 10 repetitions. No significant differences were observed between application medium deposition of paraquat with adjuvant and nozzles inclination angles for A. viridis plastic covers. For Digitaria spp., paraquat deposition with Agral® was superior to Fulltec® using +30° and 90° angles. For S. oleraceos there was increased in paraquat deposition with Fulltec® for -30° angle. All treatments presented efficient management (³ 91.0%) for weeds control at 3 days after application, with no significant differences regarding the studied conditions.
Straw influence on chemical weed control in raw sugarcane system
In the mechanical harvesting system of sugarcane, without previously burning (raw sugarcane), a straw layer is left over the soil, that may overcome up to 20 t ha-1, what represents a difficulty for germination and emergence of some weed species being possible to affect herbicides leaching and efficacy. This way, considering this environmental change, herbicides used for weeds control in pre-emergence conditions, in raw sugarcane system, must present some specific physicochemical characteristics to be effective on weeds control such as high solubility in water, low vapor pressure and low Kow. Furthermore, it is important to consider straw amount and distribution in the field and rainfall intensity after herbicide application, since these factors determine how much of the applied product is intercepted by straw, do not reaching the soil, its final destination. According to this information, the present review aims to elucidate how straw presence on soil surface may influence the chemical weeds control and herbicides behavior in areas cultivated with sugarcane crop.
Selectivity and effectiveness of Kapina® and Kapina Plus® herbicides controlling Cyperus sp. in Zoysia japonica and Cynodon dactylon grasses
The use of herbicides in turf grasses is a promising technique, since required precautions regarding the selectivity. In order to evaluate the selectivity and effectiveness of Kapina® and Kapina Plus® herbicides in controlling Cyperus flavus and Cyperus rotundus in Zoysia japonica and Cynodon dactylon, two experiments were conducted in green house conditions. Applications were performed with a CO2 pressurized spray, using application fee of 250 L ha-1. Kapina® e Kapina Plus® herbicides, from 750 mL ha-1, showed excellent control of C. flavus and C. rotundus; as well as satisfactory selectivity for Zoysia japonica and Cynodon dactylon grasses. Kapina Plus®, from 750.0 mL ha-1, besides herbicide action, also presented viability as regulator of vegetative and development growth of Emerald grass.
Chemical control and leaf surface characterization of Conyza bonariensis and C. canadensis (Asteraceae)
The genus Conyza includes approximately 60 species which are widely distributed across the globe. The species Conyza canadensis and Conyza bonariensis are noted for their ability to invade abandoned areas, pastures, perennial crops and annual crops. The objectives of the present study were to: (1) characterize the leaf surface of C. bonariensis and C. canadensis by scanning electron microscopy, (2) evaluate the control of these plants with glyphosate mixed with herbicides distinct mechanisms of action. To analyze the leaf surface by scanning electron microscopy two segments of approximately 50 mm2 were taken from the median region of young (but fully expanded) leaves of C. bonariensis and C. Canadensis. The herbicide control study was conducted in completely randomized design with four replicates. Herbicides were applied post-emergence when plants showed three to four pairs of true leaves. The herbicide treatments were: glyphosate (0.42 kg ha-1), mixed with glufosinate-ammonium (0.5 kg ha- 1), 2,4-D (1.0 kg ha-1), bentazon (0.72 kg ha-1), chlorimuron-ethyl (0.15 kg ha-1), carfentrazone-ethyl (0.03 kg ha-1), metribuzin (0.48 kg ha-1) and sulfentrazone (0.6 kg ha-1), as well as the same herbicides applied in isolation and a control treatment without herbicide. Both species are amphistomatic (with stomata on the adaxial and abaxial surface), and both possess unicellular and multicellular non-gladular trichomes. C. bonariensis had a visually larger number of trichomes on the adaxial leaf surface. For C. bonariensis the following treatments were more effective than the control: glufosinate-ammonium and glyphosate mixed with glufosinate-ammonium, bentazon, chlorimuron-ethyl and metribuzin. For C. canadensis the treatments more effective than the control were: glyphosate + glufosinate-ammonium, glyphosate + bentazon, and glyphosate + metribuzin.
Selectivity of Kapina® and Kapina Plus® herbicides applied in fairway Tifway 419 Bermuda
Cynodon spp. specie is the predominant grass frequently used in fairways, greens, tees and roughs of golf courses, but does not necessarily requires intense preventive maintenance. In order to evaluate the selectivity of Kapina® and Kapina Plus® formulations herbicides for Cynodon spp. Tifway 419, in fairway of golf camp, an experiment was conducted on turf grass belonging to Maringa Golf Club. Experimental design used was randomized blocks, with seven treatments and four replications, constituted by Kapina® (750, 1500 and 2250 mL ha-1), Kapina Plus® (750, 1500 e 2250 mL ha-1) herbicides and a check without application. Kapina® e Kapina Plus® herbicides, from 750 mL ha-1, presented a satisfactory selectivity for Tifway 419 Bermuda, and may be recommended in fairways of golf courses and other sports.
Herbicides carryover effects for the crop Crambe abyssinica in succession
Herbicides applied in previous crop may present residual effects, causing injuries in the crop in succession. Furthermore, it essential the research of tolerant crops to possible residual effects which is denominated like carryover. The objective of this research was to evaluate the carryover effects of the herbicide associations adopted in the desiccation for the soybean cultivate, in Crambe abyssinica FMS-Brilhante cultivar, grown in succession. The experiment was established and conducted in a completely randomized experimental design, with eight treatments and three replications. Treatments were: glyphosate (1,300 g a.e. ha-1), glyphosate + 2,4-D (1,300 g a.e. + 1,005 g a.e. ha-1), glyphosate + (paraquat + diuron) [1,300 g a.e. + (600 + 300 g a.i. ha-1)], glyphosate + carfentrazone-ethyl (1,300 g a.e. + 40 g a.i. ha-1), glyphosate + saflufenacil (1,300 g a.e. + 24,5 g a.i. ha-1), glyphosate + flumioxazyn (1,300 g a.e. + 35 g a.i. ha-1), glyphosate + diclosulam (1,300 g a.e. + 25 g a.i. ha-1), glyphosate + chlorimuron-ethyl (1,300 g a.e. + 20 g a.i. ha-1). After soybean harvest, it was sown the crambe crop. The evaluations were based on the determination of the plants population, at 30 days after sowing, dry biomass at flowering (45 days after sowing). At 90 days after sowing, it was evaluated the agronomic characteristics and yield of the crambe crop. It was concluding that the glyphosate association with the studied herbicides, when adopted in system of “applies and plant” the soybean, has no carryover effects for crambe crop when cultivated on clayey soils.
Sensibility of coffee plants micorrized to herbicides
The objective of this work was to evaluate the effects of herbicides applied in post-emergence of Arabic coffee plants inoculated and non-inoculated with arbuscular mycorrhizal fungi. The experiment was conducted in a factorial arrangement 2 x 6, being seedlings of Arabic coffee (Catuaí IAC 99 cv) inoculated and non-inoculated with mycorrhizal fungi (Factor 1), and five herbicides (chlorimuron-ethyl, oxyfluorfen, fluazifop-p-butil, fomesafen, [fluazifop-p-butil + fomesafen]) and a control treatment (Factor 2), with four replications. The seedlings inoculated with mycorrhizal fungi (Rhizophagus clarus and Gigaspora margarita) were produced in polyethylene bags and transplanted to 20 dm3 pots when it was in five pairs leaves stage. In seven pairs leaves stage the plants were submitted to the herbicide applications. After 45 days were measured: percentage of intoxication, height, leaf area, root volume, leaves and roots dry matter, leaf nutrient content and root colonization. Noted that chlorimuron-ethyl, oxyfluorfen and [fluazifop-p-butil+fomesafen] resulting in less increment of variables and higher phytotoxicity. The fluazifop-p-butil showed greater selectivity to coffee plants. The inoculated plants obtained higher root colonization than non-inoculated. Considering all parameters, it is concluded that the Arabica coffee cultivar Catuaí Vermelho IAC 99 inoculated with mycorrhizal fungi showed higher tolerance to fluazifop-p-butil. Similarly, also concludes that coffee plants inoculated with FMAs had become more tolerant to the adverse effects of chlorimuron-ethyl, fomesafen, oxyfluorfen and [fluazifop-p-butil + fomesafen].
Effect of herbicides on yield components of sugarcane genotypes
The most used weed control method in the sugarcane crop nowadays is the chemical. However, there is a great variation in selectivity of the genotypes regarding these products. The aim of this work was to evaluate the effect of herbicides on yield components of sugarcane genotypes. It was used a randomized blocks design, in a split-splot, with four replicates. In the plots were allocated the treatments: ametryn (2000 g ha-1), trifloxysulfuron-sodium (22.5 g ha-1), ametryn + trifloxysulfuron-sodium (1,463 + 37 g ha-1) and the weeded control. In the subplots were the sugarcane genotypes: RB72454, RB835486, RB855113, RB855156, RB867515, RB925211, RB925345, RB937570, RB947520 and SP80-1816. Results show that herbicide phytotoxicity was higher in the RB835486 and RB855113 genotypes, when compared to the weeded control. Stalk diameter of ‘RB867515’, ‘RB925211’ and ‘SP8018-16’ was not affected when applying herbicides. The number of nodes per plant and the number of sugarcane plants per meter were affected by the use of trifloxysulfuron-sodium and ametryn + trifloxysulfuron-sodium in ‘RB867515’, ‘RB925211’ and ‘RB947520’. Sugarcane productivity of the RB855156 genotype was lower when applying the herbicides. Comparing all the genotypes among themselves and in the presence of the herbicides, it was observed that the ‘SP80-1816’ and the ‘RB867515’ were the most tolerant, standing out in relation to the others. Based on the results, it can be concluded that there is different tolerance of the sugarcane genotypes regarding the tested herbicides.
Comparative dose-response curves between sourgrass (Digitaria insularis) resistant and susceptible biotypes to glyphosate
The frequent use of glyphosate in citrus cropping systems of citrus in Brazil has selected resistant populations of sourgrass (Digitaria insularis) to this herbicide, and it is important to characterize this resistance levels for reasons of rational recommendations for management measures. Thus, an assay was conducted to elaborate comparative dose-response curves between two biotypes sourgrass weed, one resistant (R) and one susceptible (S) to glyphosate. The assay was conducted in a greenhouse from February to May 2012, with five doses of the herbicide glyphosate, based on the recommended dose of the herbicide 900 g ae ha-1 ( 0.0, 450, 900, 1,800, 3,600 and 7,200 g ae ha-1) , and the weed with 3-4 tillers at time of application. It was evaluated the percentage of the dry matter in relation to dose 0.0 of glyphosate, percentage of visual control, 14 days after herbicide application. The resistance factor R/S was 16.66, when based on dry matter and 20.26 when based on the percentage of control. Thus, the R biotype has a high degree of resistance, higher than those previously reported in the literature that are smaller than 10. High degree of resistance may indicate that the mechanisms of glyphosate resistance in this biotype are the result of changes at the site of action or super gene expression, and not to metabolism, as usually occurs in weeds with low values of R/S factor. Further studies are necessary to determine these mechanisms. It was also concluded that the management of this biotype should be based on alternative herbicides to glyphosate, because increments in the dose of glyphosate are probably not economically viable.
Coexistence periods between wheat crop and weeds combined with growth regulator
The use of growth regulators in wheat crop is a usual practice, and one of its effects is the changing in plants architecture, what may interfere in the early season for weeds control. With the objective of evaluating the influence of growth regulator (trinexapac-ethyl) effect over agronomic characteristics and wheat yield, in order to determining the best period to initiating weeds control in wheat crop, an experiment was conducted in Ponta Grossa County, Parana State in 2011 agricultural year. Experimental design used was randomized complete blocks, in factorial scheme 2 x 10, represented by two treatments with or without growth regulators and 10 coexistence periods between weeds and wheat crop Quartzo genotype. The ideal period for initiating weeds control, avoiding yield reduce was up to 25 days after emergence (DAE), independent or no of trinexapac-ethyl use as growth regulator, that decreased plant height, leaves length and leaf area index, but without interfering over yield and weeds control period.
Efficacy of glyphosate in the burndown of Urochloa species
In Burndown cover plants in areas under no-till the glyphosate herbicide is the most widely used. With the aims to determine the lower dose to burndown the cover crop species adopted the Urochloa ruziziensis cv. Kennedy, U. decumbens cv. Basilisk e U. brizantha cv. BRS Piatã, in four doses (0, 0,72, 1,44 and 2,16 kg ha-1 of acid equivalent). The experimental design was of randomized blocks with four replications, in a plot scheme subdivided (3 x 4), in which the plots were set up by the species of Urochloa and subplots by doses of glyphosate. The U. ruziziensis was efficiently controlled the 14 DAA of glyphosate at 1.44 kg ha-1, or up to 28 DAA with 0.72 kg ha-1. Glyphosate applied at the rate of 2.16 kg ha-1 was not sufficient to control the U. decumbens until 14 DAA, and until 28 DAA for U. Brizantha. The speed control of vegetation formed by U. ruziziensis with glyphosate was greater than U. decumbens and U. Brizantha.
Physiological activity of sugarcane after the application of pre-emergence herbicides
The objective of this study was to evaluate the physiological characteristics of sugarcane after application of pre-emergence herbicides. For this, an experiment was conducted in a 2x5 factorial scheme, where the first factor consisted of cultivates RB 867515 and SP 81-3250, and factor B of the pre-emergence application of tebuthiuron, diuron, ametryn, a formulated mixture diuron + hexazinone and a control without herbicides. The experimental design was completely randomized, with four replications. The internal concentration of carbon (Ci), internal and external carbon (Ci/Ca) and SPAD index of cultivars of sugarcane ratio were not affected by the application of pre-emergence herbicides. However, stomatal conductance (gs), respiratory rate (E) and the photosynthetic rate (A) were reduced when treated with tebuthiuron. The A and efficiency of water use (U.S.) cultivar RB 867515 was negatively altered by the application of ametryn. It is concluded that a difference in sensitivity of the genotypes of sugar cane herbicide, and the SP 81-3250 was more tolerant. The application of tebuthiuron and ametryn reduces the A of RB 867515.
Susceptibility of crabgrass biotypes (Digitaria ciliaris) to ACCase inhibitor herbicides
Species belonging to Digitaria genus are including among major weeds infesting rice and soybeans crops. The objective of this study was to evaluate the differential susceptibility of crabgrass biotypes crops at Rio Grande do Sul State, to clethodim or cyhalofop herbicides. Three experiments were conducted in greenhouse conditions, in the period of 2009-2011 agricultural years. Seeds of Digitaria spp. were collected from different places in the State, covering areas of irrigated rice production and soybeans crops, totalizing 169 biotypes. To evaluate the biotypes sensitivity to the herbicides was applied 225 g a.i. ha-1 of cyhalofop or 96 g a.i. ha-1 of clethodim, being selected eight Digitaria ciliaris biotypes with higher and lower tolerances after herbicides application to the studies of response curve doses. It was found four biotypes with higher tolerance to cyhalofop coming from Santa Vitória do Palmar, Viamão, Santa Barbara do Sul and Cruz Alta County, with controls between 50 and 60%. Biotypes of crabgrass were susceptible to clethodim herbicide, with a control superior greater than 90%. The D. ciliaris populations collected in rice and soybeans crops in RS were susceptible to clethodim herbicide when the application was made at recommended dose, while specie susceptibility cyhalofop herbicide was differential among biotypes.
Efficacy of herbicides on post-emergence control of Sisyrinchium micranthum Cav. and Agrostis sp.
This work aimed to evaluate the effectiveness of herbicides applied during post-emergence on weed control in onion crop that recently have infested the onion crop areas in Monte Alto city, São Paulo state, Brazil. Fourteen herbicides, either alone or in mixture, were tested to control Sisyrinchium micranthum Cav. and an unidentified specie of the genus Agrostis. The herbicides used were: flumioxazin, bentazon + ioxynil + oxyfluorfen, fluazifop-p-butyl, fluazifop-p-butil + ioxynil, fluazifop-p-butil + oxyfluorfen, paraquat + oxyfluorfen, paraquat + fluazifop-p-butil + oxyfluorfen, metribuzin, sethoxydim, clethodim + fenoxaprop-p-ethyl, oxadiazon, trifluralin, and oxyfluorfen. Herbicide efficacy was evaluated at 5, 10, 15, 20, 25 and 30 days after herbicide spraying. The herbicides paraquat + oxyfluorfen, paraquat + fluazifop-p-butyl + metribuzin and oxyfluorfen showed good efficacy for Agrostis until 30 DAS and the herbicides bentazon + ioxynil + oxyfluorfen and paraquat + oxyfluorfen was considered satisfactory for S.micranthum.
Glyphosate in post-emergence at Roundup Ready® soybean
Generation of RR® soybean genotypes allowed many farmers adopted the use of glyphosate in weed management in post-emergence in cerrado. However, information about the use of this technology on soybean crop growth in “cerrado” region is important in order to obtain desired yields. Thus, the objective of this study was to evaluate the effects of glyphosate application in post-emergence condition over agronomic characteristics and over RR soybean nodulation. The trial was conducted in randomized blocks experimental design in factorial scheme (3x4)+1 with three replications corresponding to three glyphosate doses (960; 1,920 and 2,880 g a.e ha-1) associated to four application phenological stages of application (V1, V2, V3 and V1+V4) plus a treatment without herbicide application (check). The following characteristics were evaluated: grain yield, mass of a thousand grain, plant height, phytointoxication, leaf closing, root dry matter and length, besides dry mass and nodules viability. Results revealed that the dose and stage of glyphosate application did not affect the nodulation, agronomic characteristics and grain yield. The highest percentage of phytointoxication and lowest leaf closing were observed at 2,880 g a.e. ha-1 glyphosate dose sprayed on phenological stages V1+V4, without affecting nodulation and grain yield.
Herbicides selectivity and efficacy to caupi bean crop
Caupi bean is grow by small farmer’s family using low technological level, where weeds management is conducted by hoeing, and an exhausted practice with low efficiency action. The objective of this study was to evaluate herbicides selectivity and control weeds efficacy in caupi crop, BRS Guariba cultivar. The experiment was conducted in field conditions with the application of herbicides (g a.e. ha-1) sulfentrazone (500) e oxadiazon (600), in pre emergence conditions, and bentazon (600), bentazon + paraquat (39 + 62), fomesafen (225), fluazifop-p-butyl (250) and fomesafen + fluazifop-p-butyl (125 + 125), in post emergence, one treatment with hoeing at 20 and 34 days after crop emergence and a check without hoeing during the whole crop cycle. Bentazon + paraquat application promoted high phytotoxicity in caupi bean, and oxadiazon, sulfentrazone, bentazon and fluazifop-p-butyl guaranteed an excellent control of weeds, with yields really similar to those obtained with two hoeing. Fomesafen associated or not to fluazifop-p-butyl caused moderate phytotoxicity, delays flowering and harvest, besides crop yield reduction. Weeds interference during the whole crop cycle reduced grains yield in 42%.
Initial growth of cassava submitted to herbicide application in post-emergence
The aim of this study was to evaluate the initial growth of cassava plants after post-emergence application of herbicides. The experiment was carried out in greenhouse, with randomized block design and four replications. Treatments consisted in the application of herbicides 25 days after crop emergence. The herbicides applied were bentazon, clomazone, fomesafen, fluazifop-p-buthyl, glyphosate, nicosulfuron, chlorimuron-ehtyl, sulfentrazone and the fluazifop-p-buthyl + fomesafen, and a treatment without herbicide application. The visual intoxication of cassava plants was evaluated at 7, 14, 21 and 28 days after herbicide application. Thirty-five days after application, we determined the height, stem diameter and dry matter of plants. Sulfentrazone and glyphosate caused the death of cassava. All herbicides caused reduction in stem dry matter, with the exception of fluazifop-p-buthyl. Chlorimuron-ethyl and nicosulfuron caused greater reduction of dry matter accumulation and crop leaf area. The application of herbicides bentazon, nicosulfuron and chlorimuron-ethyl reduced the stem diameter. It is possible to conclude that the herbicide application affected cassava growth, except for fluazifop-p-buthyl application.
Dynamic of herbicides applied in preemergence on sugarcane straw under different water regimes
Maintenance of mulch on the soil surface can reduce the potential for weed infestations, and may affect transposition of the herbicides, the dynamics of wetting and washing the straw by rainwater. The study had as objectives evaluate the dynamics of the herbicides diuron, tebuthiuron and metribuzin in different water regimes with and without straw, and point out the main relationships between the presence or absence of straw removal of herbicides by rainwater and influence on the effectiveness of weed control. The experimental design was a completely randomized in factorial 6X3X2, with four replications, they were tested six levels for the rain factor (control, 0, 5, 10, 20 and 20 +20 mm), three herbicides (diuron 2000 g a.i. ha-1), metribuzin (1920 g a.i. ha-1) and tebuthiuron (1200 g a.i. ha-1), and two quantities of straw (0 and 10 ton ha-1). One day after application, straw was removed from the vessels and Ipomoea grandifolia and Cucumis sativus species were sown in pots, evaluating the control at 15 and 30 and 10 and 21 days after application, respectively. Diuron was less effective in the treatments with straw compared to tebuthiuron and metribuzin. The straw significantly affected the weed control by herbicides in the absence of rain, and a rain of 20 mm was sufficient to cause leaching of the herbicides into the soil making them available for absorption by the plants and to promote excellent levels of control thereof.
Narrow row spacing of corn crop and its influence on herbicide dose
Management practices integration as an auxiliary tool in weeds chemical control in post emergence in corn crop (Zea mys L.) may reduce herbicide dose to be applied. Thus, this study aimed to evaluated by spacing changes, the reduction possibility of tembotrione and mesotrione herbicides recommended doses of and without damaging weeds control and corn yield. The experimental design was randomized complete blocks, arranged in split-plot scheme with four replications. Treatments used were two row spacing (0.40 and 0.80 m); two herbicides (tembotrione - 100 g a.i. ha-1 and mesotrione - 192 g a.i. ha-1); and four herbicides doses (100, 80, 60 and 0% of recommended dose). It was evaluated effect phytotoxicity visual to the crop, wild radish (Raphanus raphanistrum L.) control and alexandergrass [Urochloa plantaginea (Link) Hitchc.] at 7, 14, 21 and 28 days after treatment application), as well as the number of plants per plots, ears per plant, thousand grain mass and yield. Results evidenced that spacing did not interfer in wild radish and alexandergrass control and in corn yield. Mesotrione herbicide was more efficient in wild radish control, and tembotrione for alexandergrass control, allowing the use 80% of recommended dose for both herbicides without affecting weeds control and corn yield.
Herbicides selectivity influenced by nutritional status of sugarcane
In order to validate the hypothesis that sugarcane crop adequately fertilized is less damaged by herbicides, phytotechnical characteristics and isoenzyme profiles of α-esterase and peroxides in IACSP96-2042 and IACSP95-5094 sugarcane genotypes were evaluated, submitted to different planting fertilizers and treated or no with herbicides. In field conditions, two experiments were conducted, one for each cultivar, in vases (43 L), by using the randomized completely design with treatments arranged in factorial scheme 3 x 3 + 1, with four replications. The first factor consisted of herbicides: clomazone (1000 g ha-1), diuron (1440 g ha-1) + hexazinone (396 g ha-1) and sulfentrazone (800 g ha-1) and the second factor was characterized by fertilization: NPK doses (absence, 20-120-100 and 40-240-200 kg ha-1) and a control without fertilizers and herbicides. In herbicides application the plants showed 20 cm height and 3 to 4 leaves. In the field, were evaluated the visual symptoms of intoxication, total chlorophyll content, plant height, leaf length, number of tillers and fresh and dry mass of plants. In laboratory conditions, it was characterized the profile of α-esterase and peroxidase isozyme before herbicide application and 58 days after, by electrophoresis on acrylamide gel. IACSP96-2042 genotype was less sensible to herbicides, without damaging fresh and dry mass, total chlorophyll content, plant height, leaf length and number of tillers. Peroxides’ isoforms were different in number and intensity; α-esterase’ isoforms were changed in bands intensity. IACSP95-5094 genotype was sensitive to phytotoxicity effects of herbicides for damaging in height, fresh and dry mass, particularly in the treatment with diuron + hexazinone.
Andréa Aparecida de Padua Mathias Azania
Control of Conyza bonariensis resistant biotypes with glyphosate + chlorimuron-ethyl as a function of development stage
Desiccation is considered the initial crops management and one of the most important practices for soybean deployment in no-tillage system. After starting the cultivation of transgenic soybean, the use of glyphosate in this crop increased expressively and provided Conyza bonariensis selection resistant to this herbicide. This study aimed to evaluate the efficacy of glyphosate in association with chlorimuron-ethyl in controlling glyphosate-resistant C. bonariensis, at different growth development stages. Eight treatments were constituted by the associated use of 2.5 L ha-1 of glyphosate (1250 g a.e.ha- 1) and 60 g ha-1 (15 g a.i. ha- 1) of chlorimuron - ethyl in plants with 3 leaves, 4 to 6 leaves, 6 to 9 leaves, 10 to 13 leaves, 13 to 16 leaves, 20 leaves, in flowering stage and a control without application. Experimental design was a randomized block with six replications. Visual control evaluations were performed at 7, 15 and 21 days after application (DAA), also determining leaves dry mass. Excellent control was found by using the association of glyphosate + chlorimuron-ethyl at plants < 9 leaves.
Effect of 2.4-D addition to glyphosate for difficult control weeds species
The 2,4-D has been one of the most widely used herbicide in combination with glyphosate, especially in applications desiccation pre-planting. The objective of this study was to evaluate the effect of adding 2,4-D to glyphosate for the control of weed species considered difficult to control (Commelina benghalensis, Richardia brasiliensis, Euphorbia heterophylla, Spermacoce latifolia, Ipomoea grandifolia e Conyza spp.). The experimental design was completely randomized, and treatments were arranged in a 3 x 4 factorial design with four replications. The first factor was composed of stages of development of weeds (2-4, 4-6 e >10 leaves) and the second factor by treatment with glyphosate (720 g i.a. ha-1), 2,4-D (670 g i.a. ha-1) glyphosate+2,4-D (720+670 g i.a. ha-1) and a treatment without herbicide (control). For Conyza spp. in green house, were performed three additional herbicide treatments varying doses of glyphosate and 2,4-D. The addition of 2,4-D to glyphosate is crucial to accelerate and improve weed control considered unwieldy as those studied in this work.
Selectivity of herbicides applied with mineral oil in cassava ‘Cascuda’
The use of adjuvant can influence the selectivity of herbicides on crops. Aimed to evaluate the selectivity of herbicides with different concentrations of mineral oil adjuvant in cassava 'Cascuda'. The experimental design was a randomized block design with four replications. We used a factorial design 3x3+1 which consisted of three herbicides clethodim (120 g ha-1), fluazifop-p-butyl (250 g ha-1) and mesotrione (240 g ha-1), three concentrations of mineral oil (Assist®) 0.0, 0.5 and 1.0% v v-1, and a control without application. All plots were kept free of weed interference by hand weeding. Only the mesotrione promoted phytointoxication mild to moderate (5.5 to 51.3%) when applied with mineral oil. However, all herbicides were selective for cassava plants 'Cascuda' in applied both in the presence and absence of mineral oil to 1% v v-1.
Andreia Cristina Peres Rodrigues da Costa
Efficacy of herbicides in controlled conditions for controlling sugarcane grass weeds under water restriction
Chemical control of weeds in sugarcane crop may be performed in dry season, mainly due to agricultural operations planning, and logistics in relation to the use of equipment and labor. This study aimed to evaluate the agronomic efficacy of herbicides for controlling sugarcane grass weeds by using different periods of water restriction. Evaluated weeds were Digitaria nuda, Panicum maximum and Brachiaria decumbens. Herbicides treatments applied in total pre-emergency condition were: diuron + hexazinone + sulfometuron-methyl (1387 + 391 + 33.35; 1507.5 + 425 + 36.25 1658.25 + 467.5 + 39.87 and 1809 + 510 + 43.5 g a.i. ha-1; amicarbazone (1190 g a.i. ha-1); amicarbazone + isoxaflutole (840 + 82.5 g a.i. ha-1) and an check without application. After application, plots were submitted to 0, 30, 60 and 90 days of water restriction. Control visual evaluations were performed 28 days after humidity restoration, with the weeds biomass determination. All studied doses of diuron + hexazinone + sulfometuron-methyl were effective in controlling the plants studied in all water restriction periods. Amicarbazone sprayed alone was not efficient on weeds control under the condition of 60 days with water restriction. Amicarbazone + isoxaflutole presented satisfactory weeds control, except for Digitaria nuda, in 60 days of water restriction.
Strategies to control of sourgrass (Digitaria insularis) glyphosate resistant in the out-of-season corn crop
The sourgrass (Digitaria insularis) characteristics of aggressiveness and the existence of glyphosate resistant biotypes puts this weed in evidence in the Brazilian agricultural scenario In this regard, the present study aimed at the development and evaluation of strategies for the management of sourgrass (Digitaria insularis) resistant to glyphosate in out-of-season corn crop. The use of paraquat in pre-harvest burn-down of soybean followed by the application of clethodim two days after harvesting soybeans provided flexibility to choose the herbicide used as post-emergent in corn.
Potential use of dietholate as a safener for clomazone in common beans
Safeners are chemicals applied to crops, usually by seed treatment, to improve their tolerance to herbicides. The objective of this research was to evaluate the potential use of dietholate as a safener for pre-emergence applications of clomazone in common beans. Treatments were arranged in a factorial combination 2 x 5 x 6 composed by two herbicide treatments (without or with clomazone at 750 g ha-1), five doses of dietholate (0, 125, 250, 375 and 500 g. a.i. per 100 kg of seeds), and six cultivars (Diamante Negro, Ouro Branco, Jalo Precoce, BRS Pérola, BRS Pontal and BRS Radiante). Dietholate only did not exhibit potential to protect common bean from injuries caused by clomazone, but also increase crop sensibility to the herbicide.
Potential for drifting of mix 2,4-D + glyphosate
The application of the mixture of glyphosate with 2,4-d took on great importance with high adoption of no-tillage system in the early 90s, and with the constant reports of weed biotypes resistant to glyphosate. However, studies on the drift of this mixture are still scarce. The aim of this study was to evaluate the potential drift of these herbicides, with or without the adjuvant, applied in wind tunnel. The experimental design was completely randomized considered, arranged in a factorial design 5 x 3, with four replications, and five tails and three collection distances (5, 10 and 15 meters). The spray tested were: glyphosate, 2,4-D, 2,4-D+glyphosate, glyphosate+2,4-D+adjuvant, and a control in which water was applied. The collection points were installed at 5, 10 and 15 meters and in this points each 20 cm of height in relation of tunnel ground until 1,0 m of height. The application of the products took place in a wind tunnel with 20 m length and cross-sectional 4 m2 with speed wind of 2.0 m s-1,. The mean values obtained in the samples were subjected to analysis of variance, and their means were compared by Tukey test at 5% probability. It was observed that herbicide application associated produces more drift than when applied alone mainly to 5 and 10 meters of distance to sprayer boom. The drift of each herbicide applied alone did not differ. When added to the adjuvant mixture glyphosate plus 2,4-D, there was a 23% reduction in drift at 5 m and 6 m to 10%.
Dose-response curves and efficacy of ALS enzyme inhibitors herbicides applied in pre emergence over Amaranthus species
Weeds from Amaranthus genus may cause major yield losses in economic crops, including cotton, if not controlled properly. In order to avoid it, it’s necessary correct species identification, besides herbicides suitability and recommended doses. The aim of this study was to develop the dose-response curve of ALS enzyme inhibitors herbicides (trifloxysulfuron-sodium and pyrithiobac-sodium) applied in pre emergence conditions becoming possible to verify the control effectiveness over four important species of Amaranthus (A. hybridus, A. viridis, A. lividus and A. deflexus) as well as the difference in susceptibility between them. For each herbicide, isolated experiments were carried out and studied doses were: 0; 1.8; 3.7; 7.5; 15.0 and 30.0 for trifloxysulfuron-sodium and 0; 35; 70; 140; 280 e 560 for pyrithiobac-sodium, equivalent to 0, ¼, ½, 1, 2 and 4 times recommended rate for clay loam soils. Results indicated that used doses to obtain dose-response curve of trifloxysulfuron-sodium and pyrithiobac-sodium provided control higher than 80% for all Amaranthus species, characterizing the possibility of herbicides application in pre emergence conditions. Besides it, differential susceptibility between Amaranthus species were reported, being A. hybridus and A. lividus the most susceptible species to both herbicides.
Burndown programs in winter wheat crop and residual activity in soybean crop
The winter field system has impacted the Conyza spp. infestation on the next Field. Thus, the aim of the research was evaluate burndown efficacy to Conyza spp. control in wheat crop area during the winter season, as well as at monitoring the residual effect of herbicides in soil on weed control within soybean cycle. The same experiment was conducted in two locations during the months of November 2010 and January 2011, in two locations in Rio Grande do Sul state (Condor and Estação) where have been cultivated with wheat winter crop. The treatments were composed by check without herbicide and for herbicides tank mixture. All the tank mixtures were glyphosate 720 g a.e. ha-1. The glyphosate was mixture with 2,4-D (402 g a.e. ha-1), diclosulam (25,2 g a.i. ha-1), chlorimuron-ethyl (10, 20 e 25g a.i. ha-1) and chlorimuron + flumioxazin (15+50; 20+50; 25+50; 15+60; 20+60 e 25+60 g a.i. ha-1). Was evaluated the burndown control at 7, 15 and 40 DAA and the density of weeds per m2 and the growth stage of the weeds at 40 DAA. The tank mixtures of glyphosate with chlorimuron-ethyl + flumioxazin, chlorimuron-ethyl and diclosulam, independently of rates, were efficient to Conyza spp. burndown control. Treatments with glyphosate + chlorimuron-ethyl + flumioxazin were the only treatments efficient to suppress the growth of new fluxes of E. heterophylla in Condor. All the tank mixtures with chlorimuron-ethyl + flumioxazin, chlorimuron-ethyl or diclosulam suppressing the initial development of Digitaria spp., Sida rhombifolia and Ipomoea triloba in Estação.
Toxicological impact of herbicides recommended for corn crop in nymphs of Podisus nigrispinus (Hemiptera: Pentatomidae) predator
Weeds presence in corn crop (Zea mays L.) may cause high losses in production. Chemical control of these plants is the most used, but may adversely affect natural enemies present in crops. Therefore, the objective of this study was to evaluate herbicides toxicity s registered for corn crop to nymphs of Podisus nigrispinus Dallas, 1851 (Heteroptera: Pentatomidae) predator. It was evaluated the effect of atrazine, nicosulfuron, mesotrione, paraquat and its control based on distilled water over three immature stages of insects (third, fourth and fifth) in doses equivalent to half, to twice, four and ten times the recommended one for corn crop. Herbicides were applied over plastic pots of 500 mL each, containing five nymphs in each stage of the insect, constituting the experimental plot, with six replications. After 96 hours was performed the counting of survivors individuals. For all stages of P. nigrispinus increasing herbicides doses caused a decrease in survival rate. This one was inferior for insects exposed to atrazine and paraquat herbicides. Mesotrione herbicide was the least toxic and nicosulfuron showed median toxicity. It was concluded that nymphs from third to fifth stage of P. nigrispinus natural enemy are more susceptible to atrazine and paraquat herbicides. Moreover, mesotrione and nicosulfuron may be used for controlling weeds in corn crop when the objective is to preserve the population of this predator.
Canola desiccation at different stages of pods maturation
Canola has outstanding as a great winter crop option and nowadays occupies the fourth place among oil species in production. One of the major difficulties in canola cultivation is the harvest season, because its pods do not show maturation uniformity. A technique that may be used to facilitate the harvest is the use of desiccants. Therefore, this study aimed to evaluate desiccation effect, in distinct pods maturation in canola crop. The work was conducted in field conditions, in Terra Roxa County, Parana State, by using a randomized complete blocks design with four replications. Treatment consisted of paraquat application (2.5 L ha-1 of Gramoxone 200®), sprayed at different periods of crop development, from three percentages of maturate pods, 30, 45 and 75% (visual assessment), plus a check without desiccant herbicides. There were no significant differences for yield and mass of a thousand seeds. In relation to seeds moisture, significant differences were observed, with 75% of mature pods occurring with inferior moisture.
Weed control in distinct light conditions with diuron
This study aimed to evaluate the weed control with the herbicide diuron sprayed in pre- and post-emergence, either under shade or full sun. It was studied the effect of the diuron at in the formulation 500 SC at 3.2 and 4.8 L ha-1 of the trade product on the plants of Euphorbia heterophylla, Ipomoea grandifolia and Raphanus raphanistrum sprayed in pre-emergence, as well as the same doses sprayed in post-emergence on plants of E. heterophylla, I. grandifolia and Senna occidentalis. For both application times, a set of pots was planted and maintained either under full sun or under a mesh that allowed only 30% of the radiation to reach the pots. The control levels were considered excellent for both application times; however there was a slower control of plants subjected to shading independent of the dose applied.
Biology aspects of Digitaria insularis resistant to glyphosate and implications for its control
Sourgrass (Digitaria insularis) is a perennial weed which has the ability to germinate, grow and develop during the entire year under Brazilian weather conditions. Once established with the formation of rhizomes, the difficulty of control greatly increases. With the recent confirmation of the existence of resistant biotypes to glyphosate, the problems became worse and knowledge on the biology of this species is critical to develop strategies for chemical management of sourgrass. The presence of this species should be monitored during the crop growing seasons (winter and summer) and also during off-season period, once neglecting the occurrence of this plant in the area can lead to a sharp increase in the population of Digitaria insularis and consequently to serious crop yield losses and increased production costs.
Leaf application of manganese in genetically modified soybean submitted to glyphosate levels
The aim of this study was to evaluate glyphosate application in Roundup Ready® soybean and yield at different levels of manganese applied by foliar way. The experiment was conducted in 2011/2012 agricultural year in Nova Maringa County, Mato Grosso State, in randomized blocks experimental design, in factorial scheme 3 x 4, with four replications. Three glyphosate levels (0.0; 0.972; 1.620 kg a.i. ha-1) and four manganese levels (0.0; 0.350; 0.700 and 1.050 kg ha-1) were used. Glyphosate was applied at V2 crop growth stage and manganese levels during V8 crop growth stage. Analyzed parameters were plant height, height of first pod insertion, green mass, dry mass, number of pods per plant, mass of 1,000 grains and yield. For height of first pod insertion, plant height, mass of 1,000 grains and yield, glyphosate and manganese applications did not cause significant effects over TMG 133 RR development. Treatments with glyphosate and manganese and its interaction did not provide increased yield in TMG 133 RR genotype.
Desiccation species of ground cover with glyphosate formulations
The management of coverage species may be accomplished by mechanical or chemical methods. In chemical method nonselective herbicides are used mainly the ones belonging to glyphosate group. The objective of this study was to evaluate phytotoxicity and agronomic efficacy of two formulations with active ingredient glyphosate over desiccation in ground cover species. The present study was conducted in field conditions in Marechal Candido Rondon County, Parana State. Experimental design used was randomized complete blocks with four repetitions in factorial scheme 2x5 (formulations x species), in that the species were white oat, black oat, ryegrass, common vetch and oilseed radish, desiccated by two herbicides: Zapp Qi® (ZQ) and Glyphosate 480 Agripec® (GA). Phytotoxicity and agronomic efficacy of coverage species were evaluated. Zapp Qi® has provided greater phytotoxicity and agronomic efficacy of coverage species when compared to Glyphosate 480 Agripec®. Zapp Qi® at 32 days after desiccation presented the highest values of agronomic efficiency. The only specie that presented 100% of efficacy was oilseed radish.
Evaluation of glyphosate and paraquat in management of Brachiaria ruziziensis
The objective of this study was to evaluate the effect of doses of paraquat and glyphosate on desiccation Brachiaria ruziziensis. The experimental design was randomized blocks with four replications. The rates glyphosate were 0, 90, 180, 360, 720 and 1440 g ha-1 and paraquat were 0, 50, 100, 200, 400 and 800 g ha-1. Based on the results obtained it can be concluded that paraquat was ineffective in desiccation B. ruziziensis and the glyphosate was only effective at rates of 720 and 1440g ha-1. There was no issuance of new tillers after desiccation of forage plants to allow practical use for management in crop-livestock system.
Control and weeds new fluxes with association to amonio-glufosinate and pyrithiobac-sodium in cotton Liberty Link®
The accompaniment of cultivated areas with cotton Liberty Link genotype (LL®) in Brazilian Cerrado-like vegetation has conducted to the observation that amonio-glufosinate isolated does not have proportionate the adequate weeds control commonly found in these areas, becoming clear the necessity of several control interventions until crop closing. The objective of this work was to verify the benefits in associating pyrithiobac-sodium to applications carried with amonio-glufosinate in cotton Liberty Link genotype (LL®) for controlling and reducing weeds new infestation. The experiment was installed in Chapadão do Sul County, Mato Grosso do Sul State, using Fiber Max 966 LL® genotype spaced 0.90 m between lines. Treatments applications was carried out 15 days after crop emergency, by using the association between amonio-glufosinate and pyrithiobac-sodium herbicides in different doses, besides a treatment formed by the mixture between pyrithiobac-sodium and trifloxysulfuron-sodium. Amonio-glufosinate used alone was not efficient for controlling weeds presented in the area. The addition of pyrithiobac-sodium contributed for controlling weed specie as Commelina benghalensis, Amaranthus retroflexus, Ipomoea grandifolia and Euphorbia heterophylla. Residual activity of pyrithiobac-sodium, mainly in 42 or 56 g ha-1 doses represented to be an excellent option for Bidens pilosa and Euphorbia heterophylla residual control, what may cause the reduction of applications number in post emergency of the crop along its cycle.
One of the most important aspects that include intercropping systems with respect of interspecific competitive ability of crops grown, however, while taking into account the integrated weed control. Because of this complexity, the adoption farming systems Crop-Livestock Integration is small, but with great capacity for expansion. Focusing on the factors that limit adoption of this system seems to be strategic point for further studies. Thus, the aim of this work was to compile a set of information related to weed management and forages concomitantly aiming to identify the main alternative for the proper management of integrate system.
Ammonium-glufosinate effectiveness associated with other herbicides in Liberty Link® cotton crop
The objective of this study was to evaluate the efficiency of ammonium-glufosinate in management programs for weeds in cotton crop FiberMax 966 Liberty Link® genotype. The experiment was installed in experimental area of Paiaguás Farm, located in municipality of Diamantino, Mato Grosso State. The experiment was conducted in a randomized block design with eight treatments and four replications. For weeds efficient management in FiberMax 966 LL genotype, the application of herbicide treatment in pre-emergence may reduce up to two post-emergence applications with no significant losses in production, but the pre-emergence treatment needs to be effective. If the application of a herbicide treatment in pre-emergence is not possible, the use of three sequential applications of ammonium-glufosinate (0.5, 0.4, 0.6 kg ha-1) at 10, 25 and 40 days after crop emergence (DAE) result in similar information. In the conditions that the experiment was conducted, all herbicide treatments were selective to the crop, without significant differences in bolls number and yield.
Association effects of glyphosate and phosphite in maize plants
The objective of this study was to evaluate the effects of glyphosate herbicide association with potassium phosphite in maize plants. The experiment was accomplished in green house conditions, with seeding of Pioneer 30F53H simple hybrid in vases. Experimental design used was entirely randomized with six treatments and four replications. Treatments application was made with plants in V7 developmental stage. Evaluations of electron transport rate (ETR) in photo system II were conducted during periods of 1, 2, 5, 32, 56, 80, 104, 128, 152, 176, 200 and 360 hours after application (HAA), as well as visual determinations of intoxication in the same plants at 2, 4, 6, 10 and 15 days after application (DAA). At the end of experiment (15 DAA) it was determined plants height with a graduated ruler from soil level as far as the insertion of last leaf fully expanded, and leaves and stalks dry mass. Glyphosate association with potassium phosphite Fosway® (3.0 L ha-1, with 30% of P2O5 and 20% of K2O) with 72 g a.e. ha-1 dose increased the levels of plant intoxication. Maize plants submitted to 72 g a.e. ha-1 dose alone showed higher growth than control. ETR of treated plants showed an increase in the first hours after application, and subsequent reduction in plants exposed to higher doses of glyphosate associated or not with potassium phosphite.
Diagnosis and methodological description proposal for scientific-technological articles relational to assessment of herbicides application
Chemical control is a viable tool and practically essential in the management of weeds control. However, insufficient details about application methods of pesticides have been observed in most scientific publications that deal with herbicides utilization. With the objective of verifying the presence or absence of basic information about herbicides application found in scientific papers, as well as to propose a criterion of minimum description needed with information that may guarantee better repeatability of methods and techniques used, it was conducted a survey in 200 papers published in national and international periodic. It was observed that minimum descriptions required about herbicides application technology have not been observed. Besides all papers showed the used application rate (L ha-1), outstanding with insufficiency the description of droplets spectrum formed by sprayer, with lack of information in 84.5% of evaluated works; work pressure (15.5%); spray solution concentration (20.5%); distance and position of nozzles in relation to the target (58.5%) and meteorological conditions, with median absence (temperature, air humidity and winds speed) of 62.6% in evaluated papers. In order to rescue the importance of criterion description about herbicides application technologies in scientific papers, it was elaborated a simplified methodological description, that offers to maximize the security and fidelity in information’s reproduced referred to weeds control.
Glyphosate and post emergence herbicides associations for controlling Commelina benghalensis on soybean RR®
This research aimed to evaluate the selectivity and efficacy of glyphosate tank mixture with different post- emergent herbicides on controlling Commelina benghalensis in soybean RR® crop. The experiment was conducted in field conditions using complete randomized block design, with four replications, where the treatments were four rates of cloransulam-methyl herbicide (10, 20, 30 and 40 g ha-1), four rates of chlorimuron-ethyl herbicide (2.5; 5.0; 7.5 and 10 g ha-1), imazethapyr at 100 g ha-1 and lactofen at 72 g ha-1, all in association with glyphosate herbicide at 960 g ha-1. It was also included three controls, characterized by an isolated rate of glyphosate at 960 g ha-1, a sequential application of glyphosate at 960/ 960 g ae.ha-1 besides a check without weeds handle control. The results obtained showed that only the unique application of glyphosate herbicide at 960 g ha-1 and its association with the lower rate of cloransulam-methyl (10 g ha-1) or chlorimuron-ethyl (2.5 g ha-1) did not promote effective C. benghalensis control. All chemical treatments did not influence soybean RR® yield, although the association of glyphosate and the higher rate of chlorimuron-ethyl (10 g ha-1) have promoted significant reduction in 1000 soybean grains weight.
Diuron, hexazinone and sulfometuron-methyl leaching separately and in commercial formulation in two contrasting soils
The objective of this research was to evaluate contrasting textures soils (clay and loamy sand) in the leaching of diuron + hexazinone + sulfometuron-methyl (1386.9 + 391 + 33.35 g ha-1) commercial formulation, and also hexazinone (391 g ha-1), diuron (1386.9 g ha-1) and sulfometuron-methyl (33.35 g ha-1), in soil columns mounted in PVC pipes. One day after the herbicide application, half of the columns received 40 mm of simulated rainfall and Ipomoea triloba weed was sown. At 21 and 30 days after sowing, it was accomplished the evaluation about percentage of weed control. For the clay texture soil, diuron + hexazinone + sulfometuron-methyl and hexazinone herbicides reached approximately 10 to 13 cm deep with 0 and 40 mm, respectively. In loamy sand texture soil, herbicides leaching was evident up to 20 cm deep, with 40 mm of precipitation. For diuron and sulfometuron-methyl herbicides, leaching tended to approach to clay texture soil with 40 mm and to loamy sand texture soil in the two simulated precipitations. Hexazinone and D+H+SMM were the herbicides that presented the highest trend to leaching, facilitated in loamy sand texture soil. Diuron and sulfometuron-methyl herbicides’ leaching was lower, fact that exposes hexazinone influence in the leaching of the evaluated commercial formulation. DOI: http://dx.doi.org/10.7824/rbh.v11i2.172
Herbicide selectivity to species of ornamental turfgrasses
The experiment was conducted with the objective of evaluating the selectivity of herbicides, applied in different times, in ornamental turf grasses. The first experiment was conducted in greenhouse conditions in randomized entirely design, with four replications, in a 4 x 5 x 2 factorial scheme. The factors corresponded to the pre-planting application herbicides ( sulfentrazone - 800 g ha-1, s-metolachlor - 1440 g ha-1 and atrazine - 2000 g ha-1 and control without herbicide application) in five species of turfgrass: Zoysia japonica (emerald), Axonopus compressus (blanket grass), Paspalum notatum (bahia grass), Zoysia tenuifolia (no-mow grass), Stenotaphrum secundatum (sant agostine grass), in sandy loam and clayey texture soils. In the second experiment, the experimental design was completely randomized, with four replications in a 6 x 6 factorial scheme. The factors corresponded to the five post emergence herbicides: atrazine (2000 g ha-1), sulfentrazone (800 g ha-1), halosulfuron (112.5 g ha-1), bentazon (0.72 g ha-1) and 2.4 D (670 g ha-1) applied on the five grasses, cited above and control without herbicide application. Phytotoxicity evaluations were assessed at at 7, 14, 21, 28 and 35 days after herbicide application. In the case of pre planting herbicides, were not detected any phytotoxicity in the grass species, regardless of soil texture. In the experiment with post-emergent herbicides, the bahia and blanket grass were sensitive to the herbicide atrazine, with 38 and 33% phytotoxicity at 21 DAA. However, the recovery of bahia grass was more effective at 35 DAA. The sulfentrazone was phytotoxic on blanket grass. The herbicides bentazon, 2,4-D and halosulfuron were selective to all species studied.
Effect of predecessor crops to sugarcane on floristic composition of weeds
This study, during one year period, dealt with the identification of the floristic composition of weeds in areas of sugarcane production, in Felixlândia, Minas Gerais State (Brazil), in response to predecessor crops to sugarcane planting. The experiment was carried out at the EPAMIG Experimental Farm, in a randomized complete block design with six treatments and four replications, being evaluated the sugarcane variety SP81-3250. The treatments were the predecessor crops to sugarcane: Pennisetum glaucum, Crotalaria juncea, Stizolobium aterrimum, Cajanus cajan and Glycine max, plus a control (degraded pasture of Brachiaria decumbens). The floristic composition was evaluated during the four seasons of the year, being identified 23 weed species distributed in 18 genera and 13 families. The most representative families were Leguminosae and Solanaceae, with four species, followed by Malvaceae, with three species and two Rubiaceae and Convolvulaceae species. The B. decumbens specie was found in all periods of the year and in all different treatments of predecessor crops to sugarcane during winter and spring seasons. The differences in floristic composition as much to the predecessor cultivations as the evaluated periods become relevant for planning the proper management of weeds in sugarcane crop.
Potential use of clomazone in common bean cultivars
Weed interference can cause severe damages to common bean grain yield. Although the use of herbicides is considered as an efficient means to control weeds, there are just a few alternatives to use in pre-emergence applications. The objective of this work was to evaluate the potential use of pre-emergence applications of clomazone for five cultivars of common bean. Experiments were carried out under greenhouse conditions in a completely randomized design, and the treatments were increasing rates of clomazone (0, 300, 600 and 900 g ha-1) applied to five cultivars of common bean: Diamante Negro, Jalo Precoce, Pérola, BRS Pontal and BRS Radiante. Increased rates of clomazone caused more visual injuries for all varieties. Increased rates of clomazone also inhibited plant growth, chlorophyll content and shoot dry mass for all cultivars except BRS Pontal. Cultivar Jalo Precoce was the most sensitive in relation to all parameters of crop injury. Chlorophyll contents in cv. BRS Radiante at 28 days after crop emergence (DAE) were not changed with increases in clomazone rate. For cv. BRS Pontal, increases in herbicide rate up to 900 g ha-1 did not cause any reduction of crop growth, chlorophyll content and shoot dry mass at 28 DAE.
Selectivity of herbicides to crops by using chemical safeners
Chemical safeners may be used to increase the tolerance of crops to herbicides, when applied as seed treatment, as well as in mixed or formulated joint to the herbicide. The mechanisms of action of these safeners are related to the reduction in the absorption and/or translocation, metabolization and to the competition with the site of herbicides action. This review aims to describe the ways of use, action mode, limitations and future perspectives for using safeners as an additional tool to increase the selectivity. Safeners use allows obtaining higher efficiency control of weed species, because provides both dose increasing of compounds that show which moderately impact over crops, and for the use of herbicides non selective to the crops, increasing the safety of application as well as the range of weed species controlled. By other side, the use of safeners aiming to increase the applied doses of herbicides, besides the ones established in respective registers, may result in optimization of environmental contamination, of crops and also of the personnel involved in the application.
Effectiveness of herbicides imazapic and amicarbazone sprayed on different amounts of sugarcane straw for the control of weeds
The straw left on the soil surface after the sugarcane mechanical harvest affects directly the weed infestation, due to, among others, the limitation of temperature variation on the seed bank, the formation of a physical barrier which enables weed emergence, and the possible allelopathic effect of the sugarcane straw. On the other hand, the straw also works as a barrier to the herbicide until it is leached into the soil. The objective of this study was to test the effect of herbicides amicarbazone and imazapic applied on different amounts of straw for the control of Luffa aegyptiaca, Ipomoea hederifolia and Bidens pilosa. Two herbicides - amicarbazone and imazapic were tested at three different rates: 1008 g a.i. ha-1, 1260 g a.i. ha-1 and 1512 g a.i. ha-1 of amicarbazone, and 123.2 g a.i. ha-1, 154 g a.i. ha-1 and 184.8 g a.i. ha -1 of imazapic, combined with the following amounts of straw: 6 t ha-1, 8 t ha-1, 10 t ha-1 and 12 t ha-1, for both herbicides. The effectiveness of the control was evaluated until 120 days after the date of application. For the species Luffa aegyptiaca, the herbicide imazapic provided an efficient control during the 120 days of evaluation. This species growth showed a positive correlation with the amount of straw on the soil surface. The herbicide amicarbazone effectively controlled Luffa aegyptiaca at all doses, even when associated with higher amounts of sugarcane straw, where this species had a greater development. For the species Ipomoea hederifolia, both herbicides amicarbazone and imazapic showed satisfying control at all doses during the first 120 days, showing no statistical differences between the factors studied. For the species Bidens pilosa, all three doses, associated with all four amounts of straw, for both herbicides, showed above 95% of control in all assessments, with no statistical differences between the treatments.
Efficacy and selectivity of imidazolinone herbicides applied in flooded rice
This study aimed to evaluate the control of red rice and the selectivity to commercial mutant rice varieties under application of imidazolinone herbicides. The experiment was installed in completely randomized blocks design, under factorial scheme 4x4, with four replications. Factor A was composed by the herbicides and Factor B by doses of these herbicides. The herbicides and doses were: imazethapyr + imazapic [(0.00; 37.50 + 12.50; 75.00 + 25.00 and 150.0+50.00 g ha-1) + Dash 0.5 v v-1], imazapyr + imazapic [(0.00; 36.75 + 12.25; 73.50 + 24.50 and 147.00 + 49.00 g ha-1) + Dash 0.5 v v-1], imazethapyr (0.00; 75.00; 150.00 and 300.00 g ha-1) and imazapic (0.00; 12.25; 24.50 and 49.00 g ha-1 + Dash 0.5 v v-1). The control of red rice was evaluated 14 and 28 days after treatment (DAT), as well as at the pre-harvest; toxicity to commercial rice was evaluated 7, 14 and 21 DAT. Commercially available mixtures of imazapic + imazapyr, at the recommended dose (73.5 + 24.5 g ha-1), and imazethapyr + imazapic at twice the dose (150.00 + 50.00 g ha-1) were efficient in controlling red rice. These same mixtures were also selective to the rice variety Puitá Inta-CL, independently of dose. Herbicides not registered for control of red rice, imazethapyr and imazapic, were not efficient in controlling red rice.
Performance of herbicides used in cotton for control of Amaranthus
Some species of Amaranthus are widely distributed in cotton crops. In recent years, ineffective weed control after herbicide use of some species has been reported. The current study was installed in order to find effective alternatives to a proper management of these species. Two simultaneous experiments were carried out for each species in this study (Amaranthus lividus and Amaranthus hybridus), and in each of them, a different stage of weed development (2 to 4 and 4 to 6 leaves) was focused. Twenty two herbicide combinations were arranged in a completely randomized design with four replicates for each experiment. Treatments were composed by the single or combined application of pyrithiobac-sodium, ammonium-glufosinate, glyphosate and trifloxysulfuron-sodium at different doses. For pyrithiobac, the best weed control results for both A. lividus and hybridus were found with applications of doses ³ 28 g ha-1. Glufosinate and glyphosate presented excellent control of both Amaranthus species, despite doses or stages of application. Comparing the use of single herbicides and tank mixtures, trifloxysulfuron+pyrithiobac resulted in improved weed control only for early applications. No negative effects of Amaranthus species were observed for mixtures of glyphosate and pyrithiobac. Mixtures of pyrithiobac and glufosinate increased A. lividus and A. hybridus control levels.
Bioindicators selection for monitoring mobility and persistence of herbicides applied in soil
The objective of this work was to select appropriate bioindicators for monitoring the mobility in soil and persistence of amicarbazone, ametryne, diuron and clomazone herbicides. The experiments were conducted in greenhouse conditions, in polyethylene pots of 250 cm3 with dystroferric Red Latosol. In each experiment, it was used one herbicide (amicarbazone, ametryn, diuron or clomazone) and three bioindicators (10 seeds of each specie), distributed in randomized blocks design in a factorial scheme 5 x 3, with three replications. Studied factors were herbicides rates (0; 12.5; 25; 50 and 100% of recommended rate of each herbicide) and species used as bioindicators (Cucumis sativus, Brachiaria decumbens e Sorghum bicolor). Thirty days after sowing, aerial parts of plants were cut and kept in a forced air oven at 40 °C in order to determine dry matter. Among bioindicators species tested, C. sativus was the one that had the highest sensitivity to the concentrations of amicarbazone and ametryne applied in soil. B. decumbens also had an appropriate response for biomonitoring clomazone and diuron, evidencing this idea for further experiments of mobility and persistence in clay soil. S. bicolor specie had the lowest inhibition of biomass among the bioindicators for all herbicides evaluated, therefore not indicated to evaluate the behavior of these herbicides in soil.
Herbicides selectivity and weeds population dynamics in sunflower crop for biodiesel production
Experiments were conducted in Prudente de Morais County, Minas Gerais State, in 2010 and 2011 years, with the objective of to evaluate selectivity and efficiency of pre and post-emergence herbicides in sunflower crop, as well as to study weeds populacional dynamic. The work conducted in 2010 was carried out in greenhouse, in a randomized complete block design, with 11 treatments and three replications. Treatments consisted by ten herbicides, four in pre emergence and six in post-emergent of the crop (alachlor, imazaquin, metribuzin, trifluralin, chlorimuron-ethyl, fenoxaprop-p-ethyl, [fluazifop-p + fomesafen], imazapyr, imazethapyr e sethoxydim) and a check. The following characteristics were evaluated: phytotoxicity effects, plants height, leaves number and dry biomass of shoot and root 60 days after product applications. In 2011, the work was accomplished in filed conditions following a randomized complete block design with six treatments and four replications. The treatments consisted of two pre-emergent herbicides: alachlor and trifluralin, two post-emergence: fenoxaprop-p-ethyl and sethoxydim and two checks (with and without weeding). Crop cycle, flowering initial, plant height, stem diameter, achenes physiologically mature, chapters diameter, broken plants number, lodged plants number, final stand and achenes yield were evaluated. Based on the obtained results, it was possible to conclude that herbicides that showed higher toxicity to sunflower plants were: imazaquin, metribuzin, chlorimuron-ethyl, [fomesafen + fluazifop-p], imazapyr and imazethapyr. The pre emergent herbicides alachlor, trifluralin, fenoxaprop-p-ethyl and sethoxydim were selective to sunflower crop. Fenoxaprop-p-ethyl herbicide may be used in a program of weeds integrated management in sunflower crop, because only trifluralin, alachlor and sethoxydim herbicides are registered for this crop in Brazil.
Herbicides efficacy applied in Crotalaria spectabilis and Crotalaria ochroleuca adult plants
The objective of this study was to evaluate the efficacy in herbicides control applied in Crotalaria spectabilis and Crotalaria ochroleuca adult plants. Three experiments were installed with seven herbicides arranged in a randomized block design with four repetitions. It was realized visual evaluations of control at 3, 7, 14, 21, 35 and 42 after applications (DAA), and regrowth at 21, 28, 35 and 42 (DAA). It was concluded that treatment with sequential application of glyphosate(1,550 + 1,860 g ha-1) provided satisfactory control for both Crotalaria species. The treatments glyphosate + 2,4-D (1,240 + 806 g ha-1), glyphosate + flumioxazina (1,240 + 50 g ha-1) and glyphosate + metsulfuron-methyl (1,240 + 1.8 g ha-1), were efficient only for controlling C. spectabilis, while glyphosate + carfentrazone-ethyl (1,240 + 32 g ha-1) and glyphosate + saflufenacil (1,240 + 52.5 g ha-1) were efficient for controlling C. ochroleuca. Glyphosate + chlorimuron-methyl (1,240 + 10 g ha-1) treatmentwas not efficient for any species of sun hemp. Independent of flumioxazina doses (20; 30; 40; 50; and 60 g ha-1) it was not verified the effectiveness of control for C. spectabilis.
Mechanical and chemical control of weeds in ares in recovery
The objective of this study was to evaluate the effects of application of glyphosate and paraquat compared to mowing to control invasive grasses in degraded areas. For the present study, the area was divided into two areas with different values of penetration resistance of soil and the fresh weight of the shoots. In each environment were selected five plots of 6x6 m². Each plot was divided into four subplots receiving treatments: glyphosate (1,44 kg ha-1), paraquat (0,40 kg ha-1), mowing and mechanical control (without herbicide and mowing). Evaluations were carried out on measurements of photosynthetically active radiation intercepted by the grass after treatment application, and estimating the total microbial activity on the basis of the evaluated and a control area. It has been found that cutting is treatment that allows higher incidence of light on the ground and paraquat application that allows a lower incidence of light. The plots treated with paraquat was hardly the arrival of new species, but shoots of the species present before. The highest rates of metabolic coefficient were found in the environment to be recovered. However, other recovery techniques must be adopted concurrently with the management for the control of species weeds.
Ipomoea hederifolia control with low volume using adjuvant spray liquid with spray rotary nozzle
The use of scientific knowledge that make possible the characterization and choice of spray nozzle suitable to control of biological target is a function of application technology. This work aimed to characterize the volumetric distribution, the spacing between nozzles, the diameter and uniformity of droplets produced by spraying nozzle of centrifugal energy and control in post-emergence of I. hederifolia with herbicide diuron + hexazinone (1170 g ha-1 + 330 g ha-1) using spray volumes of 20 and 40 L.ha-1 with or without addition of adjuvants (organosilicone - 0,025% v/v (Silwett) and vegetable oil - 1% v/v (Veget Oil). Treatments with use of rotative jet Herbi-4® model were compared to the check with hydraulic nozzle TT110.01 (150 L ha-1). Weeds control, volumetric median diameter (VMD), the percentage of droplets below 100 μm (% 100 μm) diameter and relative amplitude (RA) were evaluated. The addition of adjuvants to spray solution did not increase I. hederifolia control. The nozzle of centrifugal energy (model Herbi-4) has significantly reduced the risk of drift towards the use of hydraulic nozzle TT110.01, due to increase diameter of droplets, reducing the percentage of droplets less than 100μm and greater uniformity of droplet size, despite a pattern of distribution to be no uniform. There was no difference in I. hederifolia control between rotative jet Herbi-4® and hidraulicnozzles TT110.01.
Growth and phosphorus absorption by common bean 'Xodó' genotype under effect of glyphosate reduced rates
It was evaluated the effect of glyphosate reduced rates on growth and phosphorus (P) uptake of ‘Xodó’ common bean (Phaseolus vulgaris L.) genotype. The experiment was conducted in factorial scheme 4 x 2, in randomized blocks design with four replications, with the first factor constituted by reduced doses of 0, 4.32, 8.64 and 12.96 g ha-1 equivalent acid (e.a.) of glyphosate and the second factor consisted of soil P rates (50 and 250 mg dm-3). Evaluations were conducted 30 days after glyphosate application (DAA). The reduced dose of 12.96 g ha-1 stimulated common bean cv. Xodó growth as well as increased P concentration in stem and P content in shoot dry mass plants.
Glyphosate application using solution of urea + ammonium sulfate
Several trials have been carried out for increasing glyphosate efficacy on weed burndown, including the addiction of ammonium sulfate and urea as adjuvants. On a physiological approach, there are explanations to complementary effect of these fertilizers when concomitantly added to herbicide spray solution. Therefore, three experiments were developed in field conditions with the objective of evaluating glyphosate efficacy for burning down different weed species by using solution of nitrogen fertilizers as spraying vehicles. Six treatments were evaluated, as follows: glyphosate (540 g a.e. ha-1) application using water, solution of ammonium sulfate – AMS (15 g L-1), solution of urea – U (5 g L-1), solution of U+AMS (2.5 + 7.5 g L-1) as spraying vehicles, glyphosate at 1080 g a.e. ha-1 sprayed with water, and check without application. Treatment’s efficacy was evaluated on mixed community of weeds, Brachiaria decumbens and Sorghum halepense. The use of nitrogen fertilizer solutions as glyphosate spraying vehicles did not increase B. decumbens control. The lower rate of glyphosate had higher efficacy over mixed weed community and over S. halepense due to the use of ammonium sulfate (15 g L-1) or U+AMS (2,5 + 7,5 g L-1) solution as spraying vehicles. The positive results reached after glyphosate application with nitrogen fertilizers were also observed on the reduction of the mixed weed community fresh mass and for S. halepense fresh and dry mass.
Chemical control alternatives for sourgrass (Digitaria insularis) resistant to glyphosate
Herbicides alternatives for controlling sourgrass (Digitaria insularis) weed in infested citrus areas are limited, mainly due to the few options of registered herbicides and by the modalities in that these chemical products are used (directed applications). Thus it is important to evaluate other post-emergence herbicides, to be used in association with glyphosate, for the efficient control of glyphosate-resistant biotype of sourgrass (Digitaria insularis), resistant to glyphosate. The experiment was conducted in Matão County, Sao Paulo State, in area belonging to Cambuhy Farm, during September to October 2009, in areas presenting biotypes of D. insularis resistant to glyphosate. Application occurred when sourgrass plants were with 3 to 5 tillers stage. Treatments consisted of different herbicides in association with glyphosate. It was conducted control visual assesments at 7, 14, 21, 28 and 35 days after application and collecting and weighting of weed dry mass dossel. Treatments that showed better results were glyphosate in association with clethodim, complemented by paraquat + diuron 7 days after the first application and glyphosate in association with clethodim complemented by ammonium-glufosinate 7 days after the first application. Further, glyphosate treatments mixture to haloxyfop-methyl, glyphosate + fenoxaprop-p-ethyl + clethodim and glyphosate + tepraloxydim showed excelent performance, even with just one application.
Macroptilium lathyroides control with pre and post-emergence herbicide applications
Macroptilium lathyroides (wild bushbean) specie was found infesting relatively large areas of soybeans in the southern region of Mato Grosso do Sul State, Brazil, where farmers complained about lack of herbicides efficiency in controlling this species. There is no herbicide registered for controlling this species in Brazil, and the amount of researches involving its susceptibility to several actives principles is so limited. This study aimed to verify the efficiency of glyphosate herbicide, isolated or in association with other actives principles, in controlling M. lathyroides at three crop growth stages, as well as to find alternative herbicides for chemical control of this species in pre- and post-emergence. The experiment was conducted under greenhouse conditions, where plants were established in plastic vases containing 4 dm3 of soil, where herbicides were applied, according to the treatments, in three moments: pre-emergence (4 days after seeded), early post-emergence (4 to 6 definitive leaves) and late post-emergence (initial flowering). Under pre-emergence applications M. lathyroides was particularly susceptible to sulfentrazone and diuron herbicides; in early post-emergence, glyphosate and trifloxysulfuron-sodium were efficient, and in late post-emergence glyphosate and ammonium-gluphosinate were also efficient in controlling this species. Carfentrazone-ethyl efficiency was dependent on growth stage and pyrithiobac-sodium did not show satisfactory control. Further studies must be conducted under field conditions to confirm the results obtained in this study under controlled environment.
Effect of nozzles and pressures on spray drift of glyphosate + 2,4-D in field conditions
The aim of the work was to evaluate the effect of nozzles and pressures on the spray drift from glyphosate + 2,4-D. The nozzles designs and the respective studied pressures were: XR 11002 (150 and 300 kPa), DG 11002 (300 kPa), TT 11002 (300 kPa), AI 11002 (300 kPa) and TXVS-10 (400 kPa). Nylon strings outside the application area (1, 5, 10, 20, 50, 100 and 200 m distance) with four replications and six foam cylinders placed on the boom of the sprayer were used to collect the spray drift. Salt tracers were added in the spray solutions to quantify the deposits of each treatment by spectrophotometer. Herbicides were less and more susceptible to drift with the flat fan nozzle with pre-orifice and air induction (AI) and the hollow cone nozzle (TX), respectively. The nozzle selection and the reduction on the spray pressures may be used to decrease drift.
CONTROL OF Urochloa decumbens AND Ipomoea triloba BY THE ASSOCIATION OF HERBICIDES WITH SUGARCANE STRAW
This research aimed to evaluate the efficacy of herbicides associated with sugarcane straw on the control of Ipomoea triloba and Urochloa decumbens after simulation of different time periods of rain. Two experiments were conducted in greenhouse in pots filled with soil, being placed on them the equivalent of 0, 5 and 10 t ha-1 of sugarcane straw, after weed species sowing. The herbicides mesotrione, formulated mixture of [hexazinone+diuron] and imazapic were applied in pre-emergence on the pots with or without straw and with dry soil. At the first experiment, it was simulated a rainfall of 30 mm 1 day after application (DAA), and at the second experiment, the same quantity of rain was simulated 14 DAA. The association of sugarcane straw with the herbicide [hexazinone + diuron] does not alter its efficacy. However, the association of sugarcane atraw with imazapic increase the weed control.For the mesotrione herbicide, the late simulation of rainfall reduced I. triloba control.
Determining the level of burndown in soybean genotype with indeterminate growth habit in Mato Grosso
For cultivars with indeterminate habit, there are no reports of the most appropriate period to conducted burndown in pre-harvest. The study aimed to evaluate the influence of burndown on three different times over physiological and sanitary quality of seeds and agronomic characteristics of SYN-9074 RR cultivar with indeterminate habit, in three areas simultaneously. It was used a randomized complete block design with four replications, and joint analysis were conducted for the three distinct areas. Treatments refer to the application period of diquat (0.3 kg ha-1), or better, in soybean plants at maturation stages R6.5 (fully formed seeds, pods 50% yellow and 50% green), R7 (pods 70% yellow, with a fully mature pod on the main stem) and R7.5 (90% yellow pods) and a check without herbicide. Germination test, dry mass of dossel and little root part, shoot length and little root, sanitary condition and mass of 1000 seeds and yield were evaluated. The period more adequate to accomplish burndown in pre harvest of SYN-9074 RR cultivar with indeterminate habit was with plants showing 90% of yellow pods, or maturation period R7.5, that provided higher yield and lower incidence índex of Phoma sp., Colletotrichum dematium var. truncata and Fusarium sp. fungi.
Residual activity of ACCase inhibitor herbicides applied at pre-sowing of corn crop
The aim of this work was to determine residual activity of ACCase inhibitor herbicides applied at pre-sowing of corn crop. The experimental design was completely randomized blocks with four replications in a split-plot scheme, where the factor time interval (seven and two days prior to corn sowing) was the plot and herbicide treatments were the sub-plot: 1. check without application; 2. tepraloxydim (80 g ha-1); 3. tepraloxydim (100 g ha-1); 4. clethodim (72 g ha-1); 5. clethodim (96 g ha-1); 6. quizalofop-P-tefuryl (96 g ha-1) and 7. quizalofop-P-tefuryl (120 g ha-1). Evaluated variables were: visual phytotoxicity at 07, 14, 21 and 28 days after crop emergence, plant height, number of ears per plant, number of grains per ear, weight of thousand seeds and grain yield. All treatments proved to be selective to corn when applied prior to sowing crop period.
Glyphosate deposition with different aprayer nozzles in burndown of Panicum maximum plants
The objective of this work was to evaluate the deposition of a tracer solution constituted by glyphosate (2,160 g ha-1) + FD & C No. 1 (2,000 ppm) blushing with different sprayer nozzles in burndown of Panicum maximum cv. Mombaça plants, besides the losses quantification of the sprayer to the soil. A randomized complete block design was used with four replications. Each experimental unit consisted of three lines with 5m long, spiced of 1.0 m. Treatments were applied 12 months after P. maximum seeding, and 40 days before application, a cut was conducted to become the area uniform. The following sprayer nozzles were evaluated: fat flan nozzle XR 110015 VS (100 L ha-1) and XR 11002 VS (200 L ha-1), cone nozzle TX-4 VS (100 L ha-1) and TX-8 VK (200 L ha-1), air induction nozzle AI 11002 VS (200 L ha-1) and double flat fan nozzle TJ 60 11002 VS (200 L ha-1). Immediately after application, 25 tillers per replication were collected and washed separately leaves and stem of each one in 150 ml of distilled water, for later quantification of the tracer in a spectrophotometer. Obtained data were adjusted to a regression curve by Gompertz model. All treatments were effective in burndown P. maximum plants, independently of the spray nozzles or used volume used, which suggests the possibility of reducing application volume and herbicide dosage in burndown desiccation the studied specie, considering the use of systemic herbicide. However, there was difference in the quantity, as well as in the uniformity of solution distribution sprayed in the evaluated targets in relation to spray nozzles used, and consequently of used volume. The cone nozzle TX-VK 8 (200 L ha-1), provided less spray deposition on the soil.
Adjuvant association with herbicides in burndown and post-emergency control of weeds in wheat crop
This work aimed to evaluate associations between adjuvant to herbicides used in burndown and weeds control in post emergence conditions in wheat crop. The experiment was conducted by using randomized complete blocks with four repetitions, in factorial scheme 2 x 5 + 1, constituted by two burndown forms in pre sowing, represented by only one application and in sequence, with five adjuvant combinations (without adjuvant; Triunfo 515®; Grap Super Gun®; Assist® and Fulltec®) and a check without application. All treatments developed in burndown were submitted to the complement of post emergence control with metsulfuron-methyl or metsulfuron-methyl + 2.4-D, join to adjuvant from the respective burndown treatments. Triunfo 515®, Grap Super Gun® and Assist® (70 mL ha-1) adjuvant provided increased in Digitaria insularis control for glyphosate Polaris® and Atanor 480® (2.25 L ha-1) formulations, in unique application in pre sowing. For Commelina benghalensis, besides burndown reduction efficiency in pre sowing conditions, the use of adjuvant increased glyphosate action isolated and/or in mixture with 2.4-D and 2.4-D + metsulfuron-methyl. Associations between metsulfuron-methyl + 2.4-D, with the adjuvant, controlled satisfactory C. benghalensis in post emergency. Metsulfuron-methyl (2.4 g ha-1) and metsulfuron-methyl + 2.4-D (2.4 + 322.4 g ha-1), associated to the studied adjuvant did not cause harmful plant toxic action to wheat crop BRS 220 genotype.
Yield and quality of sugarcane cultivars raw material submitted to herbicides application
Herbicides may cause toxicity to the crop and also negative effects on yield characteristics and industrial quality of sugarcane. This study evaluated the effects ametryn, trifloxysulfuron-sodium, ametryn + trifloxysulfuron-sodium and sulfentrazone herbicides over quality and stalk yield of RB867515, SP801816, SP803280, RB937570 and RB925211 cultivars. The experiment was conducted at the Federal University of Viçosa, Viçosa County, Minas Gerais State. A distinct behavior was observed for the cultivars in the presence of herbicides, both for quality as for the stalk yield. The quality showed greater variability among cultivars than among herbicide treatments that act directly on stalk production and indirectly in sugar production, being ametryn and sulfentrazone herbicides the ones that caused higher negative interference. SP803280 cultivar was the genotype with the lowest susceptibility to herbicides.
Cassava cultivars sensibility to mesotrione herbicide
Unsuitable weed management is one of the main factors responsible for low mean yield of cassava (Manihot esculenta Crantz) in Brazil. In this crop, mechanical weed control is the most commonly used, due to the lack of registered herbicides for cassava crop. In the search for alternatives to this problem, this work aimed to evaluate the tolerance level of cassavas cultivars to mesotrione herbicide applied in post emergence. A experiment was conducted, in green house conditions, in randomized blocks with four replications. A factorial scheme 5x5 was adopted, consisting of the combination of five dosages of mesotrione herbicides and five cassava cultivars. Intoxication of cassava plants, height, stem diameter and number of leaves of plants were evaluated weekly and 35 days after application (DAA) plants were harvested for determining dry matter and leaf area.n. The highest values for visual intoxication were observed at 14 and 28 days after the herbicide application (DAA) and caused by the highest doses of mesotrione herbicide. These symptoms consisted of whiteness in new leaves. At 35 days, plants showed signals of recovery, mainly due the sprout of new leaves. The herbicide did not affected the height, stem diameter, number of leaves, foliar area and dry matter accumulation of leaves, stems, roots and in total characteristics, in any of the evaluated doses. This is an evidence of cassava cultivars tolerance to mesotrione herbicide.
Control of Euphorbia heterophylla with mesotrione and oils to different nozzles
The aim of this study was evaluate the interaction between adjuvants and spray nozzles Euphorbia heterophylla control with mesotrione. Was held application of the herbicide by three models of spray nozzles (TT 110.02, AI 110.02 and TTI 110.02) and two dosages of mineral and vegetal oil (0.5 and 3.0%). Also was verified the qualitative attributes of nozzles, using a distribution table and a droplet analyzer laser. We evaluated the visual intoxication in plants at 2, 7, 14 and 21 days after application, the dry mass of the plants at 21 days, the distribution of the drops given by the nozzles, the VDM, the percentage of volume applied with drops smaller than 200 microns, the coefficient of space variation (CV) between nozzles and the coefficient of uniformity (SPAN). Higher doses of oil were more damaging to dairy plants, with all spray nozzles tested. The vegetable oil performed better in relation to the mineral. The adjuvants reduced the DMV of all nozzles, increasing the percentage of droplets smaller than 200 microns and reduced SPAN values for TT 110.02 nozzle. The adjuvants addition enables greater uniformity even with the increased spacing of nozzles (TT 110.02 and TTI 110.02) on the spray boom.
Tolerance of cassava cultivars to herbicides fomesafen and fluazifop-p-butyl
Several studies report herbicide tolerance variations of same species with different genotypes. Thus, this study aimed to evaluate the tolerance of five cassava cultivars to the post-emergence applications of fluazifop-p-butyl, fomesafen and the association of both products. In the first visual assessment of intoxication, the most visible symptoms in cassava plants of poisoning was observed at 7 days after application (DAA), caused by mixture treatment (fomesafen + fluzifop-p-butyl) and fomesafen isolated as well. At the end of the evaluation period (35 DAP), was observed reduction of intoxication signs and foliage recovery of all cassava cultivars tested. The mixture showed to be very toxic causing reductions in leaf dry matter, stem dry matter, shoots dry matter, stem diameter, leaf area and plant height. Despite a high rate of poisoning by the herbicide fomesafen, variations in dry matter accumulation was not observed Treatments based on fluazifop-p-butyl were not toxic to culture similar to plants of the check plots. There were no differences of tolerance level to herbicide treatments in the all cassava cultivars tested.
Residual activity of pre-emergent herbicides applied in contrasting soils
This study investigated the residual activity of different rates of the herbicides alachlor, oxyfluorfen, prometryne and S-metolachlor applied in pre-emergence in soils of contrasting textures. For that, eight simultaneous experiments were conducted with samples of PSAMENT (sandy texture) and RED LATOSOL (clay texture), which received alachlor (0; 2.40 and 3.36 kg ha-1), oxyfluorfen (0; 0.48 and 0.72 kg ha-1), prometryne (0; 0.75 and 1.50 kg ha-1) and S-metolachlor (0; 1.20 and 1.44 kg ha-1) applications. The treatments monitoring was made through sowing of bio-indicator (Brachiaria decumbens or Cucumis sativus). Control was assessed by scores from 0 to 100% at 0, 25, 50, 75, 100 days after application (DAA). Regardeless of rate, alachlor provided control around 80% to 66 DAA, in clay soil and up to 50 DAA in sandy. Oxyfluorfen showed control around 80% to 56 DAA to clay soil and up to 36 DAA to sandy, in both rates. Both rates of prometryne in clay soil provided control over 80% to 28 DAA, with residual activity higher in recommended rate (1.50 kg ha-1). In samples sandy, S-metolachlor provided the same control for both rates, controlling the bio-indicator at 80% up to 52 DAA, and for clay soil in rate at 1.44 kg ha-1, presented 96% control the 80 DAA. Thereby, there was no increase in residual activity in sandy soil, even with the application of the recommended rate for clay soil.
Efficacy of nicosulfuron isolated and associated with atrazine on the weeds management of corn
The potential yield of corn may be affected by weed interference. The aim of this research was evaluate the chemical control of weed in fields of corn (BRS 1035), with sub lethal rates of nicosulfuron associated with atrazine in order to reduce doses without lose large spectrum of action in the control of weed community. The herbicides treatments were: nicosulfuron at 20, 40 e 60 g ha-1, nicosulfuron + atrazine at 20 + 1000 and 40 + 1000 g ha-1 and a check without weed management. The crops management was the same from region. The spraying was done with CO2 backpack pressurized equipment at 210 kPa, with four spray nozzles DG 11002, at 200 Lha-1 of application volume. The evaluations were based on the efficacy of herbicides and production characteristics and weight of 100 grains. It may be concluded that using nicosulfuron associated to atrazine showed satisfactory control of Ipomoea triloba, Alternanthera tenella and Digitaria horizontalis. The major grains productivity of corn was obtained with the application of nicosulfuron + atrazine at 40 + 1000 g ha-1. The weight of 100 grains was not affected by the weed community and herbicides treatments.
Convolvulaceas weeds chemical control in sugar cane
Some Convolvulaceas can cause serious damage to the sugarcane crop. In addition, can interfere on cultural practices, in mechanical harvesting, quality reducing and productivity. The aim of this estudy was verify effectiveness of some herbicides applied in pre-emergence of sugarcane culture in the absence or presence of straw, on control of six species of convolvuluses. The experimental was a completely randomized design, in a factorial with three replications, six species of Convolvulaceas (Ipomoea grandifolia, I. hederifolia, I. nil, I. purpurea, I. quamoclit and Merremia cissoides) submitted the application of herbicides imazapic (245 g ha-1), diuron + hexazinona (1770 + 330 g ha-1) and clomazone + hexazinona (720 + 180 g ha-1), in the absence and presence of cane straw. The combinations diuron + hexazinone and clomazone + hexazinone were effective in control the species Ipomoea grandifolia, Ipomoea hederifolia, Ipomoea nil, Ipomoea purpurea, Ipomoea quamoclit and Merremia cissoides, and the control was slightly increase in the presence of straw (12 t ha-1).
Control of solanaceae by herbicides used in cotton
In recent years some species of Solanaceae has appeared more frequently infesting cotton crops. Information on the management of these species are still scarce in this culture. In order to seek effective alternatives in the management of these weeds was installed this work. The experiments were conducted in green-house and installed two for each species evaluated (Nicandra physaloides Gaertn e Solanum americanum Mill.), varying the stage of application (2 to 4 and 4 to 6 true leaves). The treatments were composed by the application isolated and in mixture of herbicides pyrithiobac-sodium, amonio-glufosinate, glyphosate and trifloxysulfuron-sodium in different doses. Excluding the trifloxysulfuron-sodium, all the other herbicides applied alone showed efficacy in control of these Solanaceae. Trifloxysulfuron-sodium did not compromise the effectiveness of pyrithiobac-sodium applications in mix. The associations of amonio-glufosinate and glyphosate to pyrithiobac-sodium showed no antagonism, it is interesting to use these mixtures by residual control exercised by pyrithiobac-sodium.
Aerial application of herbicides in clay granules to weed control in Eucalyptus
An experiment was carried out in the eucalyptus area of Capão Bonito in the São Paulo state, Brazil, to evaluated the efficacy of the aerial application of the herbicides sulfentrazone and isoxaflutole using clay granules for weed control in Eucalyptus area. Aerial application of the herbicides sulfentrazone at 500 and 750 g a.i. ha-1 and isoxaflutole at 150 e 225 g a.i. ha-1, was carried out using clay granules with 1,05 g cm-3 density, high absorption capacity (24 ml 100 g-1), high wear resistance, and particle size between 500 microns and 1 mm. Liquid spraying was also performed using the same herbicides at the same doses. A check plot without herbicide application was also used. Brachiaria decumbens, Ipomoea grandifolia, Merremia cissoides e Panicum maximum were sown in the experimental plot, and control evaluations being conducted at 75 and 110 days after application. A low level control was observed for both herbicides at lower doses. Sulfentrazone at 750 g a.i. ha-1 showed better control of B. decumbens and P. maximum for the aerial application of clay granules and similar results to both applications techniques on other weeds tested. The isoxaflutole at 215 g a.i. ha-1 showed superior weed control for liquid spraying at the beginning and similar and superior results for the aerial application in the final evaluation, indicating an extension of residual effect of herbicide.
Effects of glyphosate subdoses in seedlings of rubber tree (Hevea brasiliensis Aubl.)
This study aimed to evaluate phytotoxic effects of glyphosate subdoses in seedlings of rubber tree (Hevea brasiliensis Aubl.). One year after seedlings planting three reduced rates of glyphosate were studied, as follows: T1 - 86.4, T2 - 172.8 and T3 - 345.6 g e a ha-1 and T4 - control (without application). At 7, 14, 21, 28 and 180 days after application (DAA) of herbicide, scores were assigned for visual phytotoxicity, and in the last evaluation were took measurements of increase in height and in trunk diameter plants. Glyphosate drift in H. brasiliensis caused damage to the application at 345.6 g i.a ha-1 dose, reducing plant development in height and diameter, however, there was recovery in the growth of these plants observed after 180 days after herbicide application.
Saflufenacil in controlling Luffa aegyptiana, Merremia cissoides, Mucuna aterrima and Ricinus communis
The present study aimed to verify the effectiveness of saflufenacil herbicide in post-emergence weeds control. Saflufenacil herbicide was applied over Luffa aegyptia, Merremia cissoides, Mucuna aterrima and Ricinus communis weeds, when the plants contained the second pair of true leaves at 0x, 0.25x, 0.5x, 1x, 2x, 4x, 8x with the last one the commercial recommended dose (50 g a.i. ha-1). The evaluations of control and plants canopy dry matter mass were conducted at 28 days after treatments application. The experimental design was entirely randomized with four replications. Saflufenacil dose of 50 g a.i. ha-1 controlled satisfactorily M. cissoides, M. aterrima and R. communis. However, L. aegyptiana specie was tolerant when the herbicide was used in the recommended dose. It was possible to conclude that saflufenacil herbicide was effective in controlling M. cissoides, M. aterrima and Ricinus communis but L. aegyptiana specie was tolerant when applied 50 g a.i. ha-1.
Control of Ipomoea nil using tip centrifugal machine of spraying in different volumes of the application with and without adjuvant
The incorporation of tools related to the technology of application of pesticides is inevitable for a sustainable agriculture. We tested the efficiency in the control of Ipomoea nil in initial after-emergency with diuron + hexazinone, in two volumes of application (20 ha-1 and 40 L ha-1), with or without the addition of adjuvant, using peaks of rotating and hydraulically spraying, comparatively. Other two assays had been carried to compare the volumetric distribution of solution and the diameter of the drops produced for the hydraulical and rotating peaks. The percentage of necrosis in the leaves of I. nil plants increased progressively, in two volumes, with or without the use of adjuvants. The rotating peak did not differ from the hydraulically peak how much to the effectiveness. The use of rotary peak decreased coefficient of uniformity (SPAN) in relation to hydraulic peak, indicating the production of drops with greater uniformity. The distribution of the droplets produced by the rotary nozzle provided uneven distribution pattern in relation to the control peak (TT110.01 a 40 L ha-1), due to lower volume of solution used. The peaks spacing was greater with the use of vegetable oil to the volume of 20 L ha-1. The association of the adjuvants to diuron + hexazinone provided to increase the diameter of the drops, with similar efficiency between the two tested volumes. The lower volume of application of diuron + hexazinone (20 L ha-1) in I. nil control can be used, because it provided similar efficacy to the higher volume. The use of adjuvant organ silicone (0.025 % v/v) and vegetable oil (1.0% v/v) may be recommended in the spray system with rotating tip allows for increasing the diameter of the droplets, reducing problems with drift, allowing the use of lower application volume (20 L ha-1), increasing the potential for overlapping droplets on the target.
Common bean tolerance to herbicides applied in sugarcane crop
This work was aimed to evaluate the selectivity of main herbicides used in sugar cane crop applied in pre or post emergence conditions to common bean (“Jalo” Group – cultivar “Jalo Precoce”). In pre emergence modality the treatments evaluated consisted of: ametryn (2.500 g ha-1), tebuthiuron (800 g ha-1), [hexazinone + diuron] (237.6 + 842.4 g ha-1), metribuzin (1,440 g ha-1), clomazone (800 g ha-1), isoxaflutole (112.5 g ha-1), sulfentrazone (600 g ha-1), imazapic (105 g ha-1), trifluralin (1,800 g ha-1), S-metolachlor (1,920 g ha-1), and a check without herbicide application. In post emergence modality treatments evaluated were: MSMA (1,440 g ha-1), MSMA + diuron (1,080 + 420 g ha-1), [hexazinone + diuron] (237.6 + 842.4 g ha-1), metribuzin (1,440 g ha-1), ametryn (1,500 g ha-1), [ametryn + trifloxysulfuron sodium] (1,280 + 32.4 g ha-1), halosulfuron (112.5 g ha-1), 2.4-D (1,005 g ha-1) and mesotrione (120 g ha-1) besides a check without herbicide application. Phytointoxication, stand, plant height, wet and dry matter of shoots, number of plants at harvest, height of first pod insertion, and grain yield were evaluated. S-metolachlor, tebuthiuron, trifluralin and clomazone herbicides showed satisfactory selectivity to bean plants cv. Jalo Precoce, when applied in pre-emergence. However, ametryn [hexazinone + diuron], metribuzin, isoxaflutole, sulfentrazone and imazapic were not selective, even in pre-emergence applications. None of tested herbicides showed selectivity conditions for being used in post-emergence in one bean integrated cultivation system (cv. Jalo Precoce) in areas with sugar cane crop production.
Kinetics of phosphorus uptake in transgenic soybeans after glyphosate application
There are indications that glyphosate could affect the phosphorus nutrition of soybean. Thus the present study was to evaluate P uptake absorption and allocation in soybean after glyphosate application. Two experiments were conducted in green-house in randomized complete block. The 1st experiment evaluated the glyphosate at 0,0; 1,5; 3,0; 6,0 and 12,0 g ha-1 and the 2nd experiment evaluated the glyphosate at 0,0; 200; 400 and 800 g ha-1. Glyphosate was applied at 21 days after plant emergence in foliar soybean variety 'Valiosa RR'. Then the plants were grown in nutrient solution using the technique of exhaustion of the solution. After the exhaustion test, the plants were collected for determination of dry matter and P contents in shoots and roots. Although it was not possible to determine the kinetics of absorption, was not observed stimulatory effect of P uptake in soybean after applied at low rates or depressant effect when applied at compatible rates with those recommended for weed control.
Chemical management of green manure for succession of sugar cane crop in minimum tillage system
Studies on chemical management of green manure are scarce in national literature. This work aimed to evaluate the herbicides efficiency in chemical control of green manure used in succession with sugarcane crop, in minimum cultivation system. Two experiments were conducted with Mucuna aterrima and Crotalaria spectabilis species, arranged in a randomized complete block design with 19 treatments and four replicates. The treatments were composed by three distinct rate for herbicides: glyphosate+2,4-D+carfentrazone-ethyl; glyphosate+2,4-D; glyphosate+MSMA; 2,4-D+carfentrazone-ethyl; 2,4-D; 2,4-D+picloran and check without herbicide application. Chemical control with tank mixture between glyphosate+2,4-D+carfentrazone-ethyl and glyphosate+2,4-D were the outstanding alternatives on of M. aterrima and C. spectabilis management, allowing the possibility of succession planting sugar cane crop in minimum cultivation system, with economy of operations of plowing and harrowing.
Phytotoxicity of Aspidosperma desmanthum under glyphosate drifting
This study aimed to evaluate the phytotoxic effects of glyphosate increasing doses in Aspidosperma desmanthum Benth. ex Müll. Arg. young plants. Doses of glyphosate applied one year after planting were: T1 - 86.4, T2 - 172.8, T3 - 345.6 g i.a ha-1 and T4 – check (without application). Evaluations of visual phytointoxication were conducted at 7, 14, 21, 28 and 180 days after application (DAA) of herbicide, in order that in the first and last evaluations measures of trunk diameter and height were developed. Herbicides doses caused light phytotoxicity, with necrosis in leaves, showing a tendency of recovery at 180 DAA.
Residual effect of herbicides in soil (Carryover)
The present review aimed to collect information from main studies about carryover effect of some herbicides in different crops. Therefore, some relevant subjects were discussed to better understand herbicide dynamics in soil such as the ionization equilibrium constant (pKa/pKb), octanol/water partition coefficient (Kow), solubility, vapor pressure, Henry's constant (H), half-life and the interaction among these properties. From these points, it was developed the review about the residual effects of several herbicides such as imazaquin, imazethapyr, sulfentrazone, nicosulfuron, fomesafen and other, besides pointing out damages to crops and natural environment. Phytoremediation was also discussed, as a technique of soil decontamination through cropping some plant species. For rational herbicide utilization, it is extremely important to choose appropriate products for mixtures, apply suitable doses depending on soil type and climate, as well as understand the causes of problems and control failures in order to reduce the risk of environmental impact caused by residual effects or carryover.
Selectivity of herbicides applied in post-emergence on physic nut (Jatropha curcas L.)
The lack of information on herbicides selective for cultivation of physic nut makes it difficult to tame the chemical control of weeds, especially during the initial stage of the crop. Therefore, the objective of this study was to evaluate the selectivity of herbicides applied in post-emergence to the culture of physic nut (Jatropha curcas L.). We used experimental design completely randomized with 16 treatments and 11 repetitions, three herbicides in five doses and a control without herbicide. The doses of herbicides (L ha-1) were: glyphosate (180, 450, 720, 990 and 1.260 g ha-1), fluazifop-p-butyl (100, 125, 150, 175 e 200 g ha-1) and 2,4-D amine (720, 1.080, 1.440, 1.800 e 2.160 g ha-1). The herbicides were applied 55 days after sowing, when the plant seedlings had two to three pairs of leaves. Of the three herbicides applied in post-emergency, only fluazifop-p-butyl and glyphosate at the lower dose, was completely selective to plant seedlings physic nut and is promising for the control of weeds in young plantations. None of the herbicides affected the height of the plant seedlings, though the herbicide glyphosate (in higher doses) and 2,4-D amine showed toxic effects with changes in appearance and morphology of plant seedlings.
Efficacy of amicarbazone herbicide in controlling morningglories in sugar cane (Saccharum spp.) crop
The objective of the work was to evaluate the selectivity and efficiency of amicarbazone herbicide in pre-emergency, in controlling Ipomoeas species in sugarcane crop. The experiment was developed between November, 2005 to November, 2006, in Santa Terezinha Farm, Pereira Barreto County, São Paulo State, cultivated by Pioneiros Bioenergia Company. The soil of the area is classified as LVE sandy texture. The experiment was developed in area of sugarcane crop of second year (first cut), with RB 86-5486 genotype and spacing of 1.4 m between lines. Ipomoeas species selected for the experiment: Ipomoea grandifolia, Ipomoea hederifolia, Ipomoea nil, Ipomoea quamoclit and Merremia cissoides, were sowed in parallel lines to the crop lines, after sugarcane cultivation operation. The experimental design was randomized complete blocks, with five treatments and four replications, with plots of 20 m2(5m x 4m). Treatments were constituted by amicarbazone (1050, 1225 and 1400 g ha-1) and checks, with and without weeds. Applications were accomplished in weeds pre-emergency, at 25 days after sugarcane harvest, by using a CO2 pressurized sprayer (45 lb pol-2), with bar equipped with four bar branding tips Teejet XR110.03, spaced of 0.5 m and spray volume of 200 L ha-1. It was concluded that amicarbazone herbicide (1050, 1225 and 1400 g ha-1) was selective to sugarcane plants and highly efficient in controlling I. grandifolia, I. hederifolia, I. nil, I. quamoclit and M. cissoides.
Alternative herbicides for controlling Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitor in cotton crop
The presence of Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitors is a problem to weed management in cotton crop, due to the fact that few alternatives broadleaf selective herbicides area available. In order to supply this information gap, four experiments were established in greenhouse conditions with the objective of evaluating herbicides applied in post-emergence conditions, recommended either for conventional and transgenic cotton (resistant to glyphosate and amonio-glufosinate) for controlling these resistant biotypes. The experimental design was entirely randomized with four replications and 21 herbicides treatments, besides a check without herbicide application. Two experiments were conducted per species, where the first one corresponded to herbicides application in stages of two to four leaves, and the second in the stage of four to six. It was evaluated the percentage of control at 7 and 28 days after herbicide application. Amonio-glufosinate and glyphosate applied isolated or in combinations with other herbicides were effective in controlling B. pilosa independently of the growth stage. The two biotypes demonstrated to be highly resistant to ALS inhibitor herbicides. E. heterophylla showed greater sensitivity to herbicide amonio-glufosinate herbicide and glyphosate in early stages applications. Glyphosate stood out as a satisfactory alternative for controlling E. heterophylla. For this biotype, synergistic effect was verified for associations between amonio-glufosinate and pyrithiobac-sodium.
Efficacy of s-metolachlor associated to ametryn and hexazinone+diuron in controlling pre and post-emergent of weeds in sugar cane
The work aimed to evaluate, in sugar cane crop, the selectivity and effectiveness of S-metolachlor herbicide associated to ametryn and [hexazinone+diuron], applied terrestrial and aerial forms, in pre and post emergent weeds control. The experimental design used in experiment 1 (terrestrial application) was randomized complete blocks with 16 treatments and four repetitions, applied in pre and post emergence: S-metolachlor + ametryn (1920 + 1500; 2400 + 1500 and 2880 + 1500 g a.i. ha-1; S-metolachlor + [ hexazinone+diuron ] (1440 + [ 702+198 ] and 1920 + [ 702+198 ] g a.i. ha-1; [ hexazinone+diuron ] + ametryn ([ 936+264 ] + 1500 g a.i. ha-1; tebuthiuron + ametryn (1000 + 1500 g a.i. ha-1 and checks with and without weeding. In experiment 2 (aerial application), the treatments were constituted by S-metolachlor (2880 g a.i. ha-1), S-metolachlor + ametryn (2400 + 1500 g a.i. ha-1) and checks without application, being herbicides applied in two bands of one hectare for each treatment. All herbicides treatments caused initial phytotoxicity to sugar cane crop (RB 835486), with total recovery at 45 DAA (days after application). Terrestrial application in S-metolachlor + ametryn, S-metolachlor + [hexazinone+diuron], [hexazinone+diuron] + ametryn and tebuthiuron + ametryn pre-emergence was efficient in controlling Digitaria horizontalis, Ipomoea nil and Amaranthus deflexus. In post emergency, treatments were less efficient in controlling D. horizontalis; more efficient in controlling I. nil and equivalents in A. deflexus control. Aerial application of S-metolachlor and S-metolachlor + ametryn was efficient in D. horizontalis e B. plantaginea control, providing higher sugar cane yield than the check without herbicides application.
Weeds management systems in soybean pre-planting
The study aimed to evaluate the efficiency and residual effect of herbicides, applied in management operations, in modalities “Apply-Plant” and “Anticipated Management” in soybean crop. The experimental design was randomized complete blocks with four repetitions in 8 x 2 factorial scheme, with eight herbicides associations (with flumioxazin, chlorimuron-ethyl and glyphosate) in two management systems. For “Anticipated Management” was conducted glyphosate application 20 days before sowing, with treatments being applied two days after planting. For “Apply-Plant” system, treatments were applied one day before crop sowing. It was evaluated the control efficiency and residual effect of herbicides over Euphorbia heterophylla, Amaranthus hybridus e Commelina benghalensis, besides plant height, stand and soybean yield. Results showed that “Anticipated Management” proportionate better weeds control than “Apply-Plant”, besides ensuring that soybean crop could be able to develop under better conditions, thus guaranteeing greater yield. Flumioxazin and chlorimuron presence was enough to ensure the closing canopy of crop without a post-emergency application.
Position selectivity of herbicides to cotton crop
Adequate planting depth is one of the most important factors in germination and seedling emergence, thereby ensuring a uniform stand. Thus, this study aimed to evaluate the effect of sowing depth in cotton crop (Delta Opal var.), over diuron, oxyfluorfen, alachlor, clomazone, pendimetalin, S-metalachlor, prometryne and trifluralin herbicides plant toxicity. Evaluations on crop toxicity were carried out at 7, 10, 12, 14, 17, 19, 21, 28 and 35 days after herbicide application (DAA), through EWRC scale and total dry mass at 35 DAA. No decrease in plant biomass of cotton was observed when oxyfluorfen, clomazone, pendimethalin and trifluralin herbicides were used. Dry mass decrease was observed for 0.5, 1.0, 2.0 and 3.0 cm sowing depths when diuron was applied, to 0.5, 1.0 and 3.0 cm sowing depths with the use of prometryne and for alachlor and S-metolachlor in sowing depth of 1,0 cm.
Photosynthetic efficiency of sugarcane crop submitted to atrazine and tebuthiuron application in pre-emergency
The objective of this work was to assess the photosynthetic efficiency of sugarcane crop, in pre-emergency application, of two inhibiting photosynthesis herbicides. For sugar cane cuttings planting (SP80-3280 genotype), pots with a capacity of 8 dm3 were used. Atrazine and tebuthiuron application was performed by using a stationary spray installed in laboratory conditions and after treatment application, plants were transported to a green house where were kept until the end of the trial. The reading of electrons transport rate (ETR) was conducted in the middle portion of the youngest leaves of sugarcane with a portable fluorometer, with intervals for ETR assessment constituted by: 16, 17, 19, 25 and 30 days after herbicide application. It was also developed visual analysis of phytotoxiciy performed 30 days after application. The results showed that tebuthiuron herbicide caused greater reduction in electrons transport rate than atrazine. In relation to herbicide symptoms, there was no significant difference between the studied herbicides. At the end of the study it could be verified that the chosen methodology by using fluorometer to measure the electrons transport rate after herbicide application was adequate, allowing verifying sugar cane crop intoxication, even before any visual detection of herbicides performance in plants.
Herbicides selection for controlling soybean volunteer plants resistant to glyphosate
This study aimed to evaluate the effectiveness of herbicides in controlling soybean volunteer plants resistant to glyphosate. The experiment was conducted in field conditions by using randomized complete block design in factorial scheme 6x9, with four replications, with the first factor represented by six soybean genotypes resistant to glyphosate herbicide (BRS Favorita RR® , BRS Valiosa RR® , CD 219 RR® , M-SOY 7908 RR® , P98Y11® and P98R31® ) and the second factor represented by herbicides sprayed isolated or in mixture (2,4-D, 2,4-D + glyphosate, metsulfuron-methyl, metsulfuron-methyl + glyphosate, [MSMA + diuron], [MSMA + diuron] + glyphosate, [paraquat + diuron], [paraquat + diuron] + glyphosate, and a check without herbicide). MSMA+diuron and [MSMA+diuron] + glyphosate treatments showed effective control only for CD 219 RR® . Metsulfuron-methyl+glyphosate showed efficacy in controlling M-SOY 7908 RR® , P98Y11® , P98R31® , BRS Favorita RR® and CD 219 RR® ; as soon as BRS Valiosa RR® was the most tolerant to this treatment. Glyphosate addition did not cause any antagonist effect in effectiveness of the herbicides, but increased the action of metsulfuron-methyl. The herbicides [Paraquat + diuron] and 2,4-D were effective in controlling RR soybean crop. There were differences in sensitivity of genotypes to metsulfuron-methyl, metsulfuron-methyl + glyphosate, [MSMA + diuron] and [MSMA + diuron] + glyphosate herbicides.
Selectivity of herbicides sprayed in pre-emergency in crambe crop
In Brazil, there are no herbicides registered for crambe (Crambe abyssinica Hochst), and little is known about the selectivity of herbicides over this crop. Therefore, two experiments were conducted, simultaneously, in plastic green house, with the objective of evaluating the selectivity of herbicides sprayed in pre emergency over crambe crop initial development. In the first study, it was evaluated the answer-dose of herbicides treatments trifluralin (225, 450, 675 and 900 g ha-1), alachlor (240, 480, 720 and 960 g ha-1) and pendimethalin (250, 500, 750 and 1000 g ha-1), in factorial scheme (3x4) +1, represented by herbicides (three) and doses (four) factors and a check. In the second experiment, four herbicides tank mixtures were analyzed: trifluralin + alachlor (450+480 g ha-1), trifluralin + pendimethalin (450+500 g ha-1) and alachlor + pendimethalin (480+500 g ha-1) and a check. In both studies, vases containing 4 dm3 of soil were used in randomized entirely design with eight replications. Crambe crop was extremely sensitive to pre emergency herbicides evaluated. Only trifluralin, in doses inferior to 450 g ha-1 , demonstrated selective to crambe crop. Thus, it was evident the need for more comprehensive studies aimed to assessing the selectivity of herbicides to crambe crop.
Selectivity evaluation of chlorimuron-ethyl and nicosulfuron herbicides sprayed in post emergence in alfafa crop
Two experiments were conducted simultaneously with the objective of evaluating the selectivity of nicosulfuron and chlorimuron-ethyl herbicides, applied in post-emergence at two developmental stages in alfalfa crop. Trials were conducted in greenhouse conditions in randomized entirely design, with five replications, in a 4 x 2 factorial scheme. The factors corresponded to the application of chlorimuron-ethyl herbicide at 0, 7.5, 15 and 30 g ha-1 (Trial 1) and nicosulfuron at doses of 0, 20, 40 and 80 g ha-1 (Trial 2). Herbicides were sprayed in plants with four and seven fully expanded leaves, corresponding to stages 1 and 2, respectively. Phytotoxicity evaluations were assessed at 7 and 21 days after treatment application (DAA) and of plant height and dry biomass accumulation at 44 DAA. Nicosulfuron herbicide was not selective to alfalfa crop, independent of the vegetative stage in which the application was conducted. By contrast, chlorimuron-ethyl herbicide at 8 g ha-1 was selective to alfalfa crop.
Simulated drift of glyphosate in jenipapo (Genipa americana L.) young plants
This study aimed to evaluate the effects of glyphosate sub doses in genipap (Genipa americana L.) young plants. One year after seedlings planting, three glyphosate sub doses were tested, being: T1 - 86.4, T2 - 172.8 and T3 - 345.6 g i.a. ha-1 and T4 - Check (without application). At 7, 14, 21, 28 and 120 days after herbicide application (DAA) scores were provided for visual phytotoxicity, and in the first and in the last evaluation, measurements of plant height and plant diameter were conducted. After 120 DAA it was observed that G. americana specie was sensitive to glyphosate herbicide application, affecting significantly height growth, but not plant diameter. Glyphosate doses superior than 86.4 g a.e. ha-1 caused only damages, however, with 345.6 g a.e. ha-1 occurred plant death.
Bioindicators species selecting to trifloxysulfuron-sodium and pyrithiobac-sodium herbicides
Using bioindicator species is really common in studies concerning herbicides behavior in soil. Trifloxysulfuron-sodium and pyrithiobac-sodium are herbicides recommended for post-emergence weed control in cotton crop and present potential carryover to rotational crops. The research aimed to evaluate the susceptibility of vegetal species to doses of trifloxysulfuron-sodium and pyrithiobac-sodium herbicides looking forward to selecting plants that may be used in monitoring low concentrations of these herbicides in soil. Two experiments were simultaneous carried out, in randomized entirely design, disposed in factorial scheme 4x5 with four replicates, constituted by four species used as bioindicators (cucumber [Cucumis sativus], soybean [Glycine max], corn [Zea mays] and bean [Phaseolus vulgaris] and five herbicides doses (trifloxysulfuron-sodium 0; 0.94; 1.87; 3.75 and 7.5 g ha-1 and pyrithiobacsodium at 0; 8.75; 17.5; 35 and 70 g ha-1), applied in pre-emergence, before bioindicators sowing. Twenty-one days after application (DAA), plants were evaluated in relation to phytointoxication, height and dossel mass accumulation, calculating I50 (necessary dose for reducing 50% of analyzed variable), in order to compare species sensibility to herbicides. It was concluded that cucumber and corn behaved as the most sensitive species to trifloxysulfuron-sodium and pyrithiobac-sodium herbicides, showing potential for utilization in bioassays with these herbicides.
Conyza bonariensis management with glyphosate + 2,4-D and glufosinate according to development stage
Knowing the stage where the weed is more susceptible to chemical control is a fundamental part of weeds integrated management. In the specific case of C. bonariensis that is a weed with difficult control, this knowledge has a direct influence on herbicides efficiency. Thus the aim of the present study was to evaluate the effectiveness of glyphosate + 2,4-D and glufosinate herbicides in controlling C. bonariensis sprayed at different stages of development. Treatments were arranged in a 2x5 factorial scheme, where the first factor was represented by glyphosate + 2,4-D (960 + 496 g ha-1) and glufosinate (400 g ha-1) and second one for different development stages of C. bonariensis plants (cotyledon or 0, 7, 14, 21 and 28 cm height). For each development stage of this specie was used a check for evaluating the efficiency of these herbicides and dry mass comparison. The development stage of C. bonariensis plants at application time affects significantly the efficiency of glyphosate + 2,4-D and glufosinate herbicides. Excellent controls for this species occurred when glyphosate + 2,4-D and glufosinate applications were performed on plants taller than 6 cm. Satisfactory control of C. bonariensis was obtained when plants showed maximum height of 10 and 11 cm at application time of glyphosate+2,4-D and glufosinate herbicides, respectively.
Selectivity of nicosulfuron formulations for corn hybrids in function of nitrogen fertilization period
Aimed in the present work to evaluate the interaction effect between periods of nitrogen coverage fertilization and different formulations of nicosulfuron herbicide over the selectivity to 2B-710 and 30K73 corn hybrids. Two experiments were conducted, simultaneously, with corn seedlings in V3 and V6 stages using treatments disposed in a factorial scheme 2x4+1, where the first factor was composed by two nicosulfuron formulations (18.8 g ha-1) (SansonTM and AccentTM) in mixture with atrazine (1250 g ha-1) and the second factor constituted by four periods of nitrogen coverage fertilization (67.5 kg N ha-1), represented by 0, 3, 6 and 9 days after herbicide application (DAAH); and an additional check without herbicide application. 2B-710 and 30K73 corn hybrids showed variable selectivity in relation to nicosulfuron herbicide application, with the major effects and symptoms of phytotoxicity occurring when nitrogen fertilization was performed in coverage in the same day of SansonTM formulation applying for V3 stage and three days from applying AccentTM to V6 stage.
2,4-D residual activity over soybean emergence in soils with distinct textures
– This research aimed to evaluate the 2.4-D residual activity over soybean emergence in soils with distinct textures. The experiments, each one with a distinct soil type (clay sand and clay), were conducted in greenhouse conditions, in a randomized entirely design, in factorial scheme 6x2+1 with treatments constituted by the combination of six application period: 0, 3, 5, 7, 10 and 14 days before soybean sown (DBS) and two 2.4-D (502.5 e 1,005 g e.a. ha-1) doses, besides an absolute check without herbicide application. 2.4-D residual activity was evaluated through the emergence speed index (ESI), germination percentage (%), visual phytointoxication (%), plant high (cm) and soybean plants dry biomass (g) at 26 DBS. In both soil types, 2.4-D residual activity was observed, ranging in function of herbicide dose and time period between herbicide application and soybean sown. The effect was more pronounced in plants grown on cland soil where there was higher phytointoxication and reduction of dry biomass in relation to the check, mainly at the treatment where herbicide was sprayed and soybean genotype V-Max sowed in following.
Photosynthetic efficiency of sugar cane crop after S-metolachlor and atrazine herbicides application in post-emergence
The objective of the work was to evaluate the photosynthetic efficiency through electrons transport rate in sugar cane crop, after S-metolachlor and atrazine herbicides application in post-emergence. For planting sugar cane cuttings (SP80-3280 genotype), vases with 8 dm3 capacity were used for atrazine and S-metolachlor application. Application was performed through a stationary sprayer installed in laboratory and after treatments application, plants were transported to a green house and kept until the end of the study. Reading of electrons transport rate (ETR) in the middle portion of sugar cane young leaves, with a portable fluorometer (Yield protocol) in intervals of 01, 04, 24, 48, 72 and 96 hours after application were conducted. Results demonstrated that SP80-3280 sugar cane genotype presented satisfactory selectivity to herbicides applied in post-emergence conditions, outstanding atrazine. Greatest reductions in ETR and phytointoxication were detected with S-metolachlor herbicide, with the use of fluorometer being considered an alternative and complementary methodology to evaluate herbicides selectivity.
Components of production and soybean yield in relation to the time of burndown and of management in post-emergency
Aiming to evaluate the yield and productivity of soybean crop in response to burndown time and herbicide application in post-emergence in conventional and transgenic genotypes, the area of Technological Center COMIGO, was used to conduct this study. The experimental design was a randomized complete block in factorial arrangement 2 x 7, adopting eight repetitions. The first factor corresponded to burndown times before seeding, performed 15 and 1 day before sowing (DBS). The second factor was constituted by seven managements postemergent, described as follow: 1 - BRS-GO Luziânia RR® without chemical control with manual weeding; 2 - BRS-GO Luziânia RR® uncontrolled post-emergence; 3 - BRS-GO Luziânia RR ® glyphosate application at 15 DAE; 4 - BRS-GO Luziânia RR® glyphosate application at 30 DAE; 5 - BRS-GO Luziânia RR® glyphosate application at 15 and 30 DAE; 6 - BRS-GO Luziânia with chemical control; and 7 - BRS-GO Luziânia without chemical control with manual weeding. All plots were manual weeding along the crop cycle, except those which were allocated to Treatment 02. Variables evaluated were: plant height at harvest, height of first pod, number of pods with 1, 2 and 3 seeds, total number of pods per plant, weight of one hundred grains and yield. The results allow the conclusion that: imazethapyr (30 g ha-1) + lactofen (84 g ha-1) + chlorimuron-ethyl (80 g ha-1) + haloxyfop-methyl (72 g ha-1) herbicides used on conventional soybeans caused smaller growth of soybean plants and smaller height of first pod; number of pods per plant was not affected by all treatments; the weight of one hundred grains and soybean productivity was reduced when it was realized early management (15 DBS) and none management in postemergence was adopted.
Use of glyphosate associate to herbicides applied in post-emergence on soybean crop genetically modified
Frequent utilization of associations among post-emergence herbicides has remained a lot of questions about the selectivity and effectiveness of weeds control in soybean crop. Thus, this study aimed to evaluate the selectivity and effectiveness of herbicides tank mixtures on weed management in Roundup Ready® soybean crop. For this purpose, the following treatments were evaluated: glyphosate (960 g ha-1), glyphosate + Agrus 200® adjuvant (960 + 200 g ha-1), glyphosate+chlorimuron-ethyl (960 +12.5 g ha-1), glyphosate+lactofen (960 + 96 g ha-1) and checks with and without weeds. The spraying of treatments in post emergence conditions occurred when CD 219 RR® soybean genotype plants achieved V4 leaf stage (third leaf stage). Control levels of Alternanthera tenella, Senna obtusifolia, Cenchrus echinatus and Commelina benghalensis species and crop phytotoxicity symptoms were evaluated at 3, 7, 14 and 21 days after application. The association between glyphosate+lactofen provided higher levels of phytotoxicity over the crop. All herbicide treatments evaluated were efficient in controlling Alternanthera tenella and Cenchrus echinatus, but showed unsatisfactory control of Senna obtusifolia and Commelina benghalensis, causing significant reductions in crop yield.
Metsulfuron-methyl over agronomic performance and seed quality of wheat crop
On wheat crop there is scarce scientific evidence regarding the use of herbicides, limiting the information about their effects. In this context, the objective of this work was to evaluate some yield components and seed quality of wheat crop under the effect of increasing doses application of metsulfuron- methyl in two stages of development, from the premise that the use of high doses in combination with developmental stage may affect the plant. With this purpose an experiment was conducted in field conditions, in which treatments consisted of five doses of metsulfuron-methyl herbicide: 0; 1.8; 3.6; 5.4; 7.2 g a.i. ha-1, applied at two crop stages: 4 and 10.4. Variables evaluated were: yield, thousand seed mass, germination and vigor. According to obtained results, it’s possible to conclude that metsulfuron-methyl herbicide may be harmful to wheat crop, only when it is used doses increment at silking stage.
Evaluation of Herbicides Used in the Preemergence to the Portulaca oleracea Control
Portulaca oleracea is found intervening in several crops mainly vegetables, besides crops like sugar cane and cotton. The study was developed with the objective of improving the recommendation of herbicides alternatives in pre emergency used on cotton crop, for controlling P. oleracea. The work was conducted in two stages in greenhouse conditions: the first to establishing, through dose-response curve, herbicides rates able to promote efficient control of P. oleracea; the second one, to verify the period of residual activity provided by herbicides rates considered efficient and selected in the first stage, and by recommended rates. In the first stage, increasing rates of alachlor, diuron, clomazone, oxyfluorfen, pendimethalin, prometryn, smetolachlor, trifluralin 600 and trifluralin 450 herbicides were used. In the second stage, an effective rate and a recommended one of each herbicide were applied in four periods preceding weeds sowing, evaluating control percentage at 0, 10, 20 and 30 days after treatments application (DAA). It was verified, in the first stage, that herbicides efficiently controlled P. oleracea species, with exception of two trifluralin formulations. However, the effective rates (C95) of alachlor and prometryn showed short residual activity, as observed in the second stage. Recommended rate of prometryn promoted the efficient control up to 30 DAA, unlike to alachlor. Diuron, pendimethalin, oxyfluorfen, s-metolachlor in both rates used, besides trifluralin 600 and clomazone in recommended rates, showed effective residual activity for periods up to 30 DAA, to sandy clay loam texture soil.
Efficacy and selectivity of herbicides associations applied in post-emergence in corn crop
The objective of this work was to evaluate herbicides efficacy and selectivity applied in post-emergence for controlling weeds in two corn cultivars. The experiment was conducted between December/2007 and April/2008, at FEP – UNESP, Selviria County/MS. The experiment was conducted in conventional tillage, by using seven treatments and four replications, in split plot scheme for cultivar factor: Pioneer 30 S31 and Dow Agroscience 2B710. Applications were effected in crops and weeds post-emergence, 7 and 14 days after crop emergence, by using a pressurized sprayer (CO2), with spray volume of 200 L.ha-1. It was concluded that the treatments: HerbitrinTM + AccentTM + Joint OilTM (2500 mL + 25 g. ha-1 + 0,5% v/v); HerbitrinTM + Sanson 40 SCTM + Joint OilTM (2500 mL + 470 mL ha-1 + 0,5% v/v); HerbitrinTM + CallistoTM + Joint OilTM (2500 mL + 250 mL ha-1 + 0,5% v/v); and sequential applications of HerbitrinTM + AccentTM + Joint OilTM (1250 mL + 21 g ha-1 + 0,5% v/v))/ HerbitrinTM + CallistoTM + Joint OilTM (1250 mL + 125 mL ha-1 + 0,5% v/v); HerbitrinTM + CallistoTM + Joint OilTM (1250 mL + 125 mL ha-1 + 0,5% v/v)/ HerbitrinTM + AccentTM + Joint OilTM (1250 mL + 21 g ha-1 + 0,5%v/v) and HerbitrinTM + AccentTM + CallistoTM + Joint OilTM (1250 mL + 13 g + 100 mL ha-1 + 0,5% v/v)/(1250 mL + 13 g + 100 mL ha-1 + 0,5% v/v) were highly selective to Pioneer 30 S31 and Dow Agroceres 2B710 cultivars, with expressive efficacy in controlling Amaranthus deflexus, Ipomoea nil, Commelina benghalensis e Panicum maximum weeds. It was also observed that these treatments may be recommended for controlling weed in corn crop.
Effects of different periods without rains occurrence in the efficacy of flumioxazin applied in soil and in the sugarcane mulch
The present work aimed to evaluate the efficacy of flumioxazin applied over the soil or in association with sugarcane mulch, followed by different periods without the rain occurrence. The experiment was conducted in vases under greenhouse conditions in Botucatu County, São Paulo, Brazil. Vases were filled with soil and Brachiaria decumbens, Digitaria horizontalis, Ipomoea nil, Ipomoea grandifolia, Bidens pilosa and Sida rhombifolia weeds were sown and then covered or not with sugarcane mulch, depending on the treatment used. The experimental design used was entirely randomized with four replications. Treatments were displaced in 4 x 2 factorial scheme, with factors representing four periods without rain occurrence, 1, 15, 30 and 60 days and two herbicides positioning, over the soil without sugarcane mulch and over sugarcane mulch. Control evaluations were carried out at 14, 28 and 42 days after rain occurrence. In general mode, it was possible to observe that flumioxazin application over the soil or over sugarcane mulch promoted control satisfactory levels of weeds. Reductions on control levels of some weed species were observed when the herbicide was exposed to a period of 60 days without rain occurrence.
Glyphosate effects in lignin, cellulose and fiber contents in Brachiaria decumbens
This study aimed to quantify the levels of fiber, cellulose and lignin in Brachiaria decumbent dossel, submitted to different doses of glyphosate. The experiment was carried out in a pasture area containing Brachiaria decumbens at Fazenda Experimental Lageado, FCA/UNESP, Botucatu County, São Paulo State. Treatments consisted of five glyphosate doses (36, 72, 180, 360 and 720 g ha-1) and an untreated control, by using a randomized complete block design with four replications. For herbicide application, a backpack sprayer pressurized by CO2 and equipped with a spray bar with four nozzles DG11002 VS was used, spaced 0.5 m, with solution volume of 200 L ha-1 . In general, it could be observed that fiber contents were not affected by glyphosate application and that all applied doses promoted increase in cellulose levels, 60 days after application. Glyphosate application reduced levels of lignin from 30 days after herbicide application, improving Brachiaria decumbens digestibility by reducing levels of lignin in plant.
Carryover effect of nicosulfuron alone and tank mixture with atrazine on subsequent crops
The work was developed with the objective of evaluating the carry over effect in soil of nicosulfuron herbicide isolated and nicosulfuron + atrazine over soybean, bean, cotton, cucumber, sunflower and rice crops, sown in different periods after herbicides application. The experiment was carried out from November/2008 to April/2009, at FEP-UNESP, in Selviria, County/MS, with clayey soil. The experiment was conducted under conventional tillage with crops sown in 0.5 cm spacing. The experimental design was randomized complete block with 13 treatments and 4 replications per crop. Plots were scaled with 15 m2 (3m x 5m), with 10 m2 of applied central area. Treatments consisted of nicosulfuron + atrazine (30 g + 1500 g .ha-1) and nicosulfuron (60 g .ha-1) herbicides applied to the soil at 75, 60, 45, 30, 15 and 7 days before crop sowing and a check without herbicide. Considering the obtained results, it was concluded that bean (Carioca cultivar), cucumber (Caipira-Esmeralda cultivar) and sunflower (Doe M734-G3 genotype) crops may be sown 30 days after atrazine + nicosulfuron application, as soon as isolated nicosulfuron. Soybean crop (Carrera cultivar) may be sown between 15 and 30 days after nicosulfuron + atrazine application and isolated nicosulfuron, respectively. Cotton crop (DeltaOpal cultivar), may be sown after 60 and 45 days of nicosulfuron + atrazine and isolated nicosulfuron application, respectively. However, rice crop (Primavera cultivar) may be sown 60 days after nicosulfuron + atrazine and isolated nicosulfuron application.
Efficacy of clomazone and hexazinona association over weeds control in sugarcane
The aim of this study was to evaluate the association between the herbicides clomazone + hexazinone applied during a dry period and at different doses, on soil and sugarcane mulch, in the weed control. The experiment was applied in August 22, 2007 in Santa Maria, São Paulo, Brazil. The experimental plots were constituted of five sugarcane lines spaced in 1,5 m, with 6 m of length. In the plots were sown the weeds Brachiaria decumbens, Euphorbia heterophylla, Ipomoea grandifolia, Ipomoea nil, Ipomoea hederifolia, Ipomoea quamoclit e Merremia cissoides. The treatments were the herbicides clomazone + hexazinona at doses 720 + 180; 800 + 200; 880 + 220 e 1000 + 250 g ha-1 and imazapic at 147 g ha-1, applied over the soil and sugarcane mulch. Two herbicide untreated were also used as check, being one with and other without sugarcane mulch. The treatments promoted an efficacy control of weeds species evaluated, especially until 119 days after application (DAA). At 153 DAA were observed good control for M. cissoides, E. heterophylla, I. nil and B. decumbens for the association of clomazone + hexazinone. For I. quamoclit clomazone + hexazinone only at higher doses in the presence and absence of mulch and imazapic applied over the mulch promoted satisfactory levels of control. For I. hederifolia, to the 153 DAA, the combination of clomazone + hexazinone promoted unsatisfactory levels of control and imazapic applied on the straw promoted effective control of this species and I. grandifolia only imazapic and clomazone + hexazinone at the highest dose, both over the mulch promoted good control.
Evaluation of herbicides applied on sugar cane during rainy season in Brazil
This research aimed to study different herbicides applied in the sugarcane culture during the rainy season. The experiment was established in a 3rd ratoon crop of cultivar SP84- 2025 and planted in a soil with 49.9% clay, 36.6% sand and 13.5% silt. The experimental design was a randomized block in a split-plot scheme with experimental units consisting of five sugarcane interrows with 5 m, spaced 1,5 m (37.5 m2 ) and sub-plots with one cane row of 5 m (7.5 m2 ). Seeds of Ipomoea quamoclit, Ipomoea hederifolia, Merremia cissoides, Panicum maximum and Brachiaria decumbens were sown in the sub-plots and untreated control. The herbicides evaluated were imazapic (147 g ha-1), imazapic (98 g ha-1) + sulfentrazone (600 g ha- 1 ), sulfentrazone (800 g ha-1), tebuthiuron (1000 g ha-1), amicarbazone (1400 g ha-1), flumioxazin (125 g ha-1), diuron (1066 g ha-1) + hexazinone (134 g ha-1) + imazapic (98 g ha-1), amicarbazone (840 g ha-1) + isoxaflutole (82.5 g ha-1), imazapic (98 g ha-1) + isoxaflutole (85 g ha-1) and applied at pre-emergence of the crop and weeds. During the 120 days following spraying, 698.7 mm of rainfall was observed, the average minimum and maximum temperature being 21.9 and 30.6 °C, respectively. The herbicides that were more persistent and better control on the species studied in the following descending order: amicarbazone (91.2% control), imazapic (90.8%), imazapic + sulfentrazone (89.6%), amicarbazone + isoxaflutole (89.2%), imazapic + isoxaflutole (85.6%), diuron + hexazinone + imazapic (84.4%), tebuthiuron (76%), sulfentrazone (70.8%), flumioxazin (19.2%).
Weed management in sugarcane (Saccharum spp.) grown with break-backs operation aiming mechanized harvesting
Mechanized harvesting has introduced some new factors in the cultivation of sugar cane which affect the dynamics of occurrence and weed control. One such factor is the operation of break-backs performed 60 to 90 days after planting in order to standardize the soil to work the machine harvester, but this operation causes damages to residual herbicides applied at planting. The present work was to evaluate the selectivity and performance of chemical weed control applied in two seasons: the planting of the crop and after the operation of break-backs. The experiment was carried out from November 2008 to June 2009, in the growing area of Vale do Parana distillery, Brazil, in plant-cane variety RB 92579, spaced 1.5 m between rows. The operation of break- backs was performed 70 days after planting. The experimental design was randomized blocks with 8 treatments and 4 replicates. The applications were performed in preemergence (at planting) and post-emergence of crop (after the break-backs), using a pressurized sprayer (CO2), with a bar equipped with four nozzles of the fan type, spaced at 0.5 m and a volume of 200 L ha-1. It was observed that treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + ametryn (1920 + 1500 g ha-1 after the break-backs) was effective in control of Brachiaria decumbens and Mimosa pudica, and was selective to plants of sugar cane. The treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + hexazinone+diuron (1920 + 900 g ha-1, after the break-backs) was effective in controlling B. decumbens and was selective to plants of sugar cane. The treatment s-metolachlor (1920 g ha-1 at planting) and s-metolachlor + amicarbazone (1920 + 1050 g ha-1, after the break-backs) was highly efficient in controlling B. decumbens and M. pudica, but had little selectivity to plant sugar cane. The treatment smetolachlor + ametryn (960 + 750 g ha-1 at planting) and s-metolachlor + ametryn (960 + 1500 g ha-1 after the break-backs) was effective in controlling M. pudica and was selective to the crop.
Chemical Control voluntary Roundup Ready® soybean plants
This study aimed to evaluate the efficacy of several herbicides to control volunteer Roundup Ready soybean plants. The experiment was carried out in a greenhouse at Fesurv, Rio Verde - GO, in 2008, and the experimental plots were composed of pots of 10 dm3 of capacity. We have used the GR Valiosa® soybean cultivar, arranged in a randomized block design, replicated five times. It was applied the following treatments: atrazine (1,500 g ha-1), tembotrione (100.8 g ha-1), mesotrione (120 g ha-1), nicosulfuron (40 g ha-1), 2,4 D (670, 1,050 e 1,340 g ha-1), diquat (300 g ha-1), paraquat (400 g ha-1), [paraquat + diuron] (500+250 g ha-1) and a control without herbicide. The application was made when the plants were at the V3 growth stage. All herbicides except nicosulfuron, mesotrione, tembotrione and 2,4 D (670 g. ha-1) were effective in controlling soybean voluntary. In contrast the highest levels of control were obtained by atrazine and [paraquat + diuron].
Effects of flumioxazin permanence period in soil and in corn and oat mulch on weed control efficacy
This work aimed to evaluate the efficacy of flumioxazin applied over soil and over oat and corn mulch for controlling weeds, after different periods of permanence without rain. The experiment was carried out in vases, under greenhouse conditions in Botucatu County, São Paulo, Brazil. Vases were filled with soil, and weeds seeds of Brachiaria decumbens, Ipomoea nil, Digitaria spp, Bidens pilosa, Ipomoea grandifolia and Sida rhombifolia were sown and covered or not with oat and corn mulch, depending on the treatment used. For each coverage specie (oat and corn), treatments were constituted by factorial scheme 2 x 4, in randomized entirely design, with four repetitions, with two positions of herbicide application (over soil and over mulch) and four periods without occurrence of rain after herbicide application (1, 15, 30, and 60 days), besides checks without product application, in presence or absence of mulch. It was observed that flumioxazin application over corn and oat mulch promoted excellent weeds control levels. It was also observed a tendency of reduced control levels for some weeds species when the product was exposed for periods longer than 30 days between the application and the occurrence of rains.
Effects of different soil humidity conditions and germination depths of Brachiaria plantaginea and Digitaria spp. over amicarbazone herbicide efficacy
An experiment was conducted in green house, with the objective of evaluating the efficacy of amicarbazone herbicide in controlling Brachiaria plantaginea and Digitaria spp., in function of germination depth and soil humidity conditions. Treatments were constituted by five germination depths of weeds (1; 2; 3; 4 e 5 cm) and four humidity conditions (15 mm of rainfall followed by herbicide application; 15 mm of rainfall, followed by herbicide application and 15 mm of rainfall after 7 days after application (DAA); 15 mm of rainfall, followed by herbicide application and 15 mm of rainfall at 14 days after application (DAA); herbicide application on dry soil and 15 mm of rainfall at 14 DAA, and check without herbicide application, disposed in factorial scheme 5 x 5, with four replications. Weeds seeds were seeded in vases in different depths of germination and visual evaluations of plants control were conducted at 14, 28 and 42 days after application (DAA). It was observed that for B. plantaginea, the best control results occurred in treatments with rains occurrence, being observed initials flaws in controlling when the product was applied in wet soil and without rains occurrence in 1, 2 and 5 cm of depth, with recover and superior control levels at the end of the study. For Digitaria spp., satisfactory levels of efficacy on weeds control were observed in the different application conditions.
Different chemical ripeners action on sugarcane yield and technological quality
This study objectified to determine the effect of the ripeners, ethephon, trinexapac ethyl, sulfumeturon metal, fluazifop-p-butil and glyphosate, over technological quality and sugarcane yield. The experiment was carried out in ratoon cane, (RB86 – 7515 genotype) at Santa Antonina Farm, in Sertãozinho County, São Paulo State, in 2007 agricultural year. The experimental design used was randomized complete block with four replications. Treatments tested were constituted by: glyphosate at 0.40 L ha-1, sulfumeturon-methyl 20 g ha-1, sulfumeturonmethyl 10 g ha-1 glyphosate + 0.20 L ha-1, fluazifop-p-butyl 75 mL ha-1, trinexapac-ethyl 0.80 L ha- 1 , ethephon 0.67 L ha-1 and a check without ripeners application. Evaluations were made in the moment of application, 15, 30, 45 and 60 days after products application (DAA). Application of all used products as ripeners promoted significant effect, in relation to the check, for sugar cane Pol characteristic, since the first period of evaluation (15 DAA) until the final (60 DAA). Plant height and ATR were modified by ripeners application inside evaluated periods. Fluazifop-p-butyl application stopped sugarcane growth. Yield was changed by ripeners applications in all evaluated periods. Fluazifop-p-butyl application increased yield immediately after application (15 DAA), however for the other periods, this treatment showed the lowest yield. Sulfumeturon-methyl, sulfumeturon-methyl + glyphosate and ethephon showed the best yield results from 30 and 60 DAA. ATR values were higher with glyphosate and fluazifop-p-butyl application.
Herbicides and nematicides interactions on sugarcane (Saccharum spp.)
The research aimed to evaluate the effects of insecticides/nematicides interaction, applied at planting groove, and herbicides in pre and post-emergence, in the initial stage of sugarcane crop. The experimental design for pre and post emergency conditions was randomized complete blocks with three replications distributed into split plot, with insecticides located in the plots and herbicides in the splits. Studied inseticides were carbofuran (2100 g ha-1) and aldicarb (1500 g ha-1) and the herbicides in pre emergency conditions were tebuthiuron (1000 g ha-1), diuron+hexazinone (702+198 g ha-1), diuron+hexazinone (936+264 g ha-1), ametryn+trifloxysulfuron-sodium (1097+27.8 g ha-1) + diuron+hexazinone (702+198 g ha-1), ametryn+trifloxysulfuron-sodium (1097+27.8 g ha-1) + metribuzin (960 g ha-1). Herbicides applied in post emergency were diuron+hexazinone (936+264 g ha-1), diuron+hexazinone (936+264 g ha-1) + mesotrione (120 g ha-1), metribuzin (960 g ha-1), metribuzin (1440 g ha-1) + mesotrione (120 g ha-1), all added to mineral oil. It was concluded that didn’t occur synergistic interactions between insecticides/nematicides and herbicides since the products did not interfere significantly in crop initial development.
Viability of the tubers of purple nutsedge (Cyperus rotundus L.) treated with sulfentrazone and flazasulfuron
The use of herbicides for weed control have improved in the last years, mainly for the control of purple nutsedge (Cyperus rotundus L.) and other perennial weeds. In order to study the control of purple nutsedge, sulfentrazone and flazasulfuron isolated and in mixture, were applied in field conditions with high infestation of this species and repeated on the second year. The variable analysed were viability of the tubers of C. rotundus at 90 and 300 DAT in 2004 and at 90 and 270 DAT in 2005, collected in the arable layer (25x25x25cm), and taken to a greenhouse where they were planted. Evaluation of the percentage of germination was done at 20 days after the planting of the tubers of C. rotundus. The results showed that the herbicides provided significant reductions of the tubers viability of purple nutsedge. Best control was achieved with flazasulfuron at 50 g.ha-1 and flazasulfuron at 50 + 50 g.ha-1 in sequential applications.
Evaluation of Cyperus rotundus tubers sprouting by breathing test
The breath test is a indirect biochemical test that means to measure the amount of oxygen consumed, has been extensively used in measuring the respiration rate of seeds and soil respiration. The objective was to develop and validate a methodology to assess sprouting of purple nutsedge (Cyperus rotundus) tubers by breathing test. In order to develop the methodology, tests were carried out with the objective of homogenizing the sprouting. In these tests the tubers suffered a preconditioning with glucose, gibberelic acid or with distilled water. In addition to validate the methodology it was used the glyphosate in five rates that was sprayed in pots infested with C. rotundus at the full development (before flowering). The results obtained showed that there is no significant difference in the sum of the breathed amount considering the use of glucose or water in the preconditioning and a reduction in use of gibberellic acid. In the period of 48-96 hours the CO2 production was decreased with the increased glyphosate rate, as well as the percentage of sprouting. Therefore the proposal methodology can be used as a fast and simple technique to foresee the percentage of sprouting tubers.
Leaching of flazasulfuron and flumioxazin in two different soils
Flazasulfuron is recommended for sugarcane and flumioxazin for soybean and other leguminous crops in Brazil. Due to the importance of these crops the herbicides may be widely used and there is a need to know their behavior in the cultivated soils. In order to study the leaching of these compounds, an experiment was carried out in greenhouse with two soils: a sandy loam Typic Hapludox (LVd) with 22 g dm-3 of organic matter and a clay Rhodic Eutrudox (LRe) with 13 g.dm-3 of organic matter. Flazasulfuron was applied at 50 and 100 g.ha-1 and flumioxazin at 50 g ha-1. The soils were put in 50 cm high PVC columns, with 10 cm diameter. The herbicides were applied with a CO2 sprayer over the surface of the columns. Rains of 50 and 100 mm were dripped over the surface with perforated recipients in amounts of 10 mm each time. All treatments had four replicates. After this, the columns were cut longitudinally in halves and Cucumis sativus and Avena sativa were sown all along as test-plants. Visual evaluations of herbicide symptoms were done at 7, 11, 14 and 23 days after sowing, measuring the extent of damaged plants along the columns. Only C.sativus showed sensibility to the herbicides. Flazasulfuron at 50 g, in LRe, leached to 6,5 cm with 50 mm of rain and to 10 cm with 100 mm. In the LVd soil, it reached 3,6 cm with 50 mm and 1,1 cm with 100 mm. At 100 g, in LRe it leached 6,2 cm with 50 mm and 10,5 cm with 100 mm. In the LVd it reached no more than 2,0 cm with both rains. Flumioxazin showed very little leaching in both soils, being the symptons detected in no more than 2,7 cm in the LRe and 2,0 cm in the LVd. Symptons of the herbicides were detected in the bottom of the columns, showing that some amount was leached through the entire column of soil. The differences observed between the soils may were related to the organic mater content of the soils.
Efficacy of amicarbazone herbicide on post-emergence control in morningglory species (Ipomoea grandifloia and Merremia cissoides)
Different weeds species are present in Brazilian sugar cane areas interfering negatively in productive process, and morningglory species, Ipomoea sp. and Merremia sp., are outstanding, particularly in raw cane areas. This way, the objective of this study was to verify the effectiveness of amicarbazone herbicide in controlling Ipomoea grandifolia and Merremia cissoides species, applied in post emergency and compared to 2,4-D herbicide. So, it was conducted an experiment, in green house conditions, in pots, with Latossoil Red distrofic (LRd), seeded with weeds. The experimental design used was entirely randomized with five treatments and four replications, and mediums submitted to Tukey test at 5% of probability. Treatments consisted of 700, 1050, 1400 g i.a. ha-1 of amicarbazone, 1612 g i.a. ha-1 of 2,4-D and an check. Treatments application was carried out in post-emergence, when weeds containing 15 cm tall, and at 7, 14 and 21 days after application (DAA) and the control was assessed, with dossel plants collect for obtaining dry mass, at 21 DAA. After collecting plants, it was conducted a new sowing in pots with the same weeds species and at 7, 14 and 21 days after sowing (DAS) visual control evaluations were conducted, in order to verify the residual effect of treatments. The experimental design was entirely randomized with five treatments and four replications, and mediums submitted to Tukey test at 5% of probability. It was verified that, independent of morningglory species studied, amicarbazone herbicide at 700, 1050, 1400 g i.a. ha-1 doses showed total control at 21 DAA, as well as up to 21 DAS, it was also observed excellent residual effect for this herbicide.
Ananas erectifolius Growth Under Effect of Glyphosate Low Doses
Amazonian native plant, Ananas erectifolius has been a specie of great interest for automobile industry, due to the fibers contained in its leaves that show resistance, softness and reduced weight. Some studies about simulation of glyphosate drift have been demonstrating the occurrence of tolerance and/or incentives of dossel growth of some vegetable species. This way, with the objective of evaluating the effects of glyphosate subdoses application in growth, development and yield of Ananas erectifolius an experiment was conducted in field conditions at Fazenda Pematec Triangel do Brasil Ltda, Santarém County, PA State. Studied treatments were constituted by glyphosate application in the concentrations of 0.0; 11.2; 22.5; 45.0; 90.0; 180.0; 360.0 g a.e. ha-1 and a hoe check. Ananas erectifolius plants presented low tolerance to glyphosate herbicide, and superior subdoses to 45.0 g a.e. ha-1 promoted the most significant reductions of benefitted leaves yield when applied in post-emergency. None of the studied subdoses promoted incentive or increase of Ananas erectifolius plants vegetative development.
Methodology for determining the tubers viability of Cyperus rotundus
This work aimed to develop and to validate a methodology based on tetrazolium test to determine the viability of purple nutsedge tubers (Cyperus rotundus). The treatments for methodology development were combined in factorial design 3 x 4 x 5, three tubers conditions (dead as control, conditioning with water and conditioning for loss of moisture), four concentrations of tetrazolium (0.1, 0.25, 0.5 , and 1%) and 5 assessment periods (8, 16, 24, 32 and 48 hours after immersion in solution). For methodology validation the treatments were arranged in factorial design 2 x 5, with two methods to evaluate the tubers (tetrazolium test and sprouting) and five rates of glyphosate: 0, 180, 360, 720 and 1440 g a e ha-1, applied to C. rotudus at the pre-flowering. At 30 days after glyphosate application the tubers were collected for evaluation by tetrazolium test and sprouting. The concentration of tetrazolium used for validation was 1%, keeping the tubers in the solution for a period of 24 hours. At the end of each studied period, the tubers were removed, washed and cut to conduct visual assessment, determining the presence and intensity of coloration along the surface of them. The best treatments were those in which the tubers were previously dehydrated, indicating that tetrazolium entrance predominantly occurs by mass flow. The treatments results for methodology validation indicated that the coloration percentage decreased as the glyphosate rates increased. Tetrazolium test is a good indicator of the viability of purple nutsedge tubers, with satisfactory results when immersed in 1% concentration for at least 8 hours.
Low doses of glyphosate and its effects on Commelina benghalensis growth
With the objective of verifying the effect of low doses, simulating glyphosate herbicide drift in growth and initial development of Commmelina benghalensis, a study was conducted in greenhouse conditions. C. benghalensis was superficially sowed (approximately 2 cm) in small tubes filled out with substratum. After the germination, just one plant by tube was kept and treatments were applied. Treatments were constituted by different glyphosate doses, 2, 4, 8, 16, 20 and 24 g a.e. ha-1 and a check without application. By obtained results, it was possible to verify that, doses starting from 2 g a.e. ha-1 may cause effects in growth and development of dossel and roots of C. benghalensis plants.
Tank mixtures of 2,4-D+picloram and plant growth regulators in Brachiaria brizantha pasture cv. MG-5
With the aim of studying tank mixtures of 2,4-D + picloram and plant growth regulators in Brachiaria brizantha pasture cv. MG-5 an experiment was carried out in field conditions at Rancharia County, São Paulo State, Brazil. The experimental design was constituted by randomized complete blocks with 14 treatments and 4 replications, composed by commercial mixture of 2,4-D + picloram (Tordon™), in dose of 750 g a.i. ha-1 and its tank mixtures with phytoregulators: Ethrel™ (ethephon), Pro-Gibb™ (GA3), Moddus™ (trinexapacethyl) in doses of 40, 80 e 120 g a.i. ha-1 and Stimulate™ [citocinine (0.09 g L-1) + GA3 (0.05 g L- 1 ) + IBA (0.05 g L-1)] in doses of 35, 70 e 140 mL ha-1 and one hoe check. The applications were developed in the tillered pasture stage and with six expanded leaves. All mixtures controlled efficiently Sida glaziovii specie at 21 days after application, without causing phytotoxicity to the pasture. The content of gross protein in B. brizantha leaves, after harvest seeds, showed medium increase in order of 1.0 % for isolated Tordon™ in relation to the other treatments. Tordon™ + Ethrel™ (80 g ha-1) and Tordon™ + Moddus™ (120 g ha-1) mixtures provided increase in dry matter of pasture dossel, overcoming the treatment with isolated Tordon™ and equalizing to the check. Ethrel™, Moddus™ and Stimulate™ tank mixtures with Tordon™ did not interfere in B. brizantha cv. MG-5 seed production, but may favor the pasture dossel development, without interfering in S. glaziovii control.
Selectivity of postemergence herbicide associations in early soybean
The frequent use of associations among postemergence herbicides has raised many questions about the selectivity of these for soybean crop. The objective of this work was to evaluate the selectivity of postemergence herbicide associations, and their influence on agronomic aspects, and yield of Msoy 6101® , a soybean cultivar with early cycle. The study was conducted in Motevidiu - GO, during the 2004-2005 crop season. The experimental block design was entirely randomized in split-plot scheme with twofold checks, and four replicates. Tested treatments consisted of : flumiclorac – pentil + chlorimuron ethyl (40 + 12,5 g ha-1), lactofen + chlorimuron ethyl (96 + 12,5 g ha-1), chlorimuron ethyl + Imazethapyr (60 + 12,5 g ha-1), flumiclorac - pentil + chlorimuron ethyl + clethodim (40 + 12,5 + 60 g ha-1), and Lactofen + chlorimuron ethyl + haloxyfop methyl (96 + 12,5 + 42 g ha-1). Results showed that the mixture lactofen + chlorimuron methyl + haloxyfop methyl caused the highest levels of phytotoxicity, reducing plant height. No herbicide association reduced the number of pods per plant. However, the mixture flumiclorac-pentil + chlorimuron-ethyl + clethodin caused significant reduction on yield, and cycle of the early soybean cultivar Msoy 6101® .
Effect of sulfentrazone in the integrated system using sugarcane mulch residue, herbicide and vinasse on purple nutsedge (Cyperus rotundus) initial development
The objective of this work was to evaluate the interactions among sugarcane mulch residue, the herbicide sulfentrazone and different application methods of vinasse, a sugarcane industry residue, on the initial development of purple nutsedge (Cyperus rotundus L.). A greenhouse experiment was set up using pots with soil, in randomized complete blocks, with four replications and the following treatments were studied: control (C), straw alone (P), vinasse alone (V), herbicide alone (H), straw + vinasse (PV), straw + herbicide (PH), herbicide + vinasse applied before the herbicide (HVa), herbicide + vinasse applied after the herbicide (HVd), herbicide + vinasse applied together (HVj), straw + herbicide + vinasse applied before the herbicide (PHVa), straw + herbicide + vinasse applied after the herbicide (PHVd) and straw + herbicide + vinasse applied together (PHVj). Sulfentrazone was applied at the rate of 700 g ha-1, and in the treatments HVj, sulfentrazone was diluted in water until ¼ of the necessary volume, the remaining ¾ being completed with vinasse. In the statistical analysis the F test was used while the Scheffé test was employed to study the following contrasts: C x H, C x P, Cx V, C x treatments with H, C x treatments with S; C x treatments with V; without herbicide x with herbicide; without straw x with straw, without vinasse x with vinasse, HVa x HVd; HVa x HVj, HVa x HVj; HVa x SHVa, HVd x SHVd, HVj x SHVj, SHVa x SHVd, SHVd x SHVj and SHVd x SHVj. It was uses the Duncan’s test for the umidity straw avaliation. It was concluded that sulfentrazone applied alone or on the sugar cane mulch residue or with vinasse applied before, after or in mixture with herbicide controlled the initial development of purple nutsedge. Sugar cane mulch residue reduced the initial development of purple nutsedge but the height of plants was increased due to etiolation. Vinasse applied on the soil without sugar cane mulch residue and without sulfentrazone stimulated the development of this weed. There wasn’t difference among appling vinasse before, after or in mixture with sulfentrazone in the treatments with or without straw.
Chemical control quantification of weeds through different uptake forms
The work aimed to quantify the intensity of herbicides action in Brachiaria decumbens (BRADC) and Digitaria horizontalis (DIGHO) control, through different uptake forms. This way, three experiments were carried out in plastic greenhouse conditions represented by atrazine (3.00 kg ha-1 + mineral oil 0.5% v v-1), oxyfluorfen (0.72 kg ha-1) and isoxaflutole (0.06 kg ha-1) herbicides, applied in initial post-emergence. Three uptake possibilities (root, foliar and root + foliar) and a check treatment were studied, in sandy and clay soils, constituted by 4x2 factorial design, with five replications. For the isolation of uptake herbicides it was used plastic tubes and aluminum paper to guarantee the presence or absence of seedlings or soil protection. It was observed that isoxaflutole foliar and root uptake controlled BRADC efficiently in sandy and clay soils to 15 DAA (days after application). For DIGHO, isoxaflutole provided efficient control by root route, in the order of 1.9 and 5.6 times, superior than foliar route for sandy and clay soils to 15 DAA. Oxyfluorfen foliar uptake controlled BRADC (> 93%) in the order of 16.8 and 15.1 times superior than root route for sandy and clay soils. DIGHO specie was not satisfactorily controlled by atrazine and oxyfluorfen herbicides for none of different uptake routes and soil types.
Weeds control and selectivity of tembotrione herbicide in the corn culture
With the aim of evaluate the efficiency and the selectivity of the tembotrione herbicide, isolated and complemented with atrazine, in the weeds control of the corn culture, an experiment was installed at the UEPG School Farm, in the 2004/05 agricultural year. The experimental design was a complete randomized blocks with nine treatments and four repetitions. The treatments consisted of the postemergence application of Equip Plus (foransulfuron & iodosulfuron methyl sodium) - 0,12 L ha-1 complemented with Atrazinax (atrazine) - 2 L ha-1 and Hoefix (adjuvant) - 1,0 L ha-1; Sanson (nicosulfuron) - 0,60 L ha-1 complemented with Atrazinax - 2,0 L ha-1; Callisto (mesotrione) - 0,30 L ha-1 complemented with Primóleo (atrazine) - 3,0 L ha- 1 ; Soberan (tembotrione) - 0,18 and 0,24 L ha-1 complemented with Atrazinax - 2 L ha-1 and added of Aureo (metilado oil of soy) - 1,0 L ha-1; Soberan (tembotrione) - 0,24 and 0,30 L ha-1 added of Aureo (metilado oil of soy) - 1,0 L ha-1; with and without weeding. The used hybrid was DKB-215. Soberan complemented with Atrazinax is efficient in the control for Brachiaria plantaginea, Digitaria horizontalis e Bidens pilosa , with similar results to Callisto + Atrazinax and equal or superior results to Equip Plus and Sanson + Atrazinax. When applied isolated Soberan it showed equal result for the grassy ones, however, for Bidens pilosa the control was efficient, but inferior to some treatments; Soberan in the biggest rate and with Atrazinax after promoted light symptoms of fitotoxicity up to 14 days its application, such which the mixture of Equip Plus and Sanson + Atrazinax.
Herbicides to control Chloris distichophylla (False-Star-Grass)
The weed Chloris distichophylla (Lag) has been selected in areas of orchards and RR soybean in the Rio Grande do Sul- RS (Brazil), resulting of its possible tolerance to the herbicide glyphosate. This selection occurs due to intense use of this herbicide in the last years resulting in a disturb caused by the high pressure selection imposed by the herbicide occurs, resulting in selection of tolerant plants. The objective of this study was to evaluate the effectiveness of herbicides pertaining the different mechanisms of action in the control of the Chloris distichophylla and the possible tolerance of this species in three growth stages to the glyphosate herbicide. Three experiments were carried out in the College of Agronomy of the UFRGS in Porto Alegre – RS (Brazil) through the experimental design completely randomized with four replications. C. distichophylla in early growth stages was not tolerant to glyphosate. Moreover, the atrazine, glufosinate, glyphosate and paraquat herbicides showed high control when the weed had four leafs, whereas the fluazifop, imazapyr and mesotrione herbicides had showed satisfactory control.
Effectiveness of herbicides for Alternanthera tenella control
The objective of this work was to evaluate the efficacy of different herbicides, applied both at pre and post-emergence, to control Alternanthera tenella. Two assays were accomplished: the first one for pre-emergence herbicides, and the second one for post-emergence herbicides, applied at two pair of leaves stage. Pre-emergence herbicide treatments and respective rates (g i.a. ha-1) were: alachlor (2880); chlorimuron-ethyl (15); metribuzin (576); clomazone (1000); flumetsulam (120); sulfentrazone (600); trifluralin (540); amicarbazone (1050); pendimethalin (1500); oxyfluorfen (360); ametryn (1500); diuron (1500); imazapic (140); isouron (175); s-metolachlor (576 and 960) and check plot. Post-emergence herbicide treatments were: fomesafen (250); [diuron+paraquat] [200+400]; 2,4-D (1005); carfentrazone-ethyl (60); chlorimuron-ethyl (15); lactofen (168); bentazon (720); flumiclorac-pentyl (60); [glyphosate+imazethapyr] [444,5+75]; diquat (400); glyphosate (540 and 1440) and check plot. For pre-emergence applications, all herbicides were considered efficient for A. tenella control, propitiating more than 98% control at 28 days after application (DAA). The post-emergence herbicide treatments, fomesafen, lactofen and bentazon did not control A. tenella. Remaining post-emergence treatments provided more than 97% control of A. tenella at 28 DAA.
Efficacy and selectivity of imazapic isolated or associated with other herbicides applied with and without sugarcane straw
The management of weeds in the sugarcane is based on the integration of cultural methods, mechanical, physical and chemical. As a physical measure, there is the presence of waste straw from mechanical harvesting, which may act as a barrier, reducing the infestation of weeds or as a physical barrier on the action of herbicides on weed control when applied in preemergence of these plants on the straw of the sugar cane. As a result, the objective of this work is analyze the influence of the layer of straw on the ground in the action of imazapic and mixtures used in the cultivation of sugar cane in weed control in areas where sugar cane is harvested mechanically without straw burning. The experiment was performed in Santa Fe - Paraná, with sandy soil. The treatments in the experiment were isolated imazapic, imazapic + [diuron + hexazinone], and tebuthiuron imazapic sulfentrazone + [diuron + hexazinone], applied in the absence and presence of straw. In general, the presence of straw contributed to control of Brachiaria decumbens and Ipomoea grandifolia. The effectiveness of herbicide treatments in the presence of straw was similar to or higher than the performance of the same in the absence of straw. The presence of straw does not affect the operation of imazapic in weed control, and may even increase its effectiveness to control. All herbicide treatments were harmless to the tiller, regardless of the presence of straw.
pH reducers and metals complexes in the laboratory
The research aimed to evaluate the behavior of various pH reducers and metals complexers, under laboratory conditions. Were used 15 commercial products (10 pH reducers and 5 metals complexers), added to the spray mix. Five experiments were conducted; two to assess the stability of pH, after addition of pH reducers (Experiment 1) and metals complexers (Experiment 2) at 1% concentration, two to determine the necessary quantity of pH reducers (Experiment 3) and metals complexers (Experiment 4) to pH 3.5, an experiment to evaluate the reduction Ca activity in CaCO3, after addition of metals complexers (Experiment 5). Treatments with pH reducers do not differ and were statistically lower than the control (Experiment 1). Redumax was the complexer which has the lowest pH of the solution, with pH 1.3 (Experiment 2). In Experiment 3, pH Fos (0.06 L), P 30 (0.07 L) and Ubyphos (0.08 L) were the products that were used the smaller rate to reduce pH. The largest rate necessary was observed for NP10 with 0.8 L (Experiment 3). The product that uses the smallest volume in Experiment 4 was Redumax (0.12 L). L1 was the complexer that required higher rate, with 3.56 L (Experiment 4). No significant difference between L1 and control in Experiment 5, showing that this product does not confer complexant action.
Addition of pH reducers and rates of glyphosate in the weeds desiccation
Two experiments were conducted to evaluate the influence from the addition of pH reducers and rates of glyphosate in the spray mix to Euphorbia heterophylla and Glycine max control. The treatments were arranged in a factorial scheme (4 x 2) + 1, randomized blocks design and four replications. Each experiment used a pH reducer (pH Fós ou Redumax), four rates of reducer (0, 50, 75 and 100% of the rate recommended), two rates of glyphosate (450 and 900 g ha-1) and an untreated check. The weed control was evaluated at 4, 6, 8, 10, 12 and 14 days after application (DAA) of treatments, in visual scale from 0 to 100% of control. In both experiments, 450 g ha-1 glyphosate, the addition of reducers in the spray mix provided greater weed control in relation to only glyphosate. There was no difference in 50, 75 and 100% of the rate recommended of reducers. With the use of adjuvant has a satisfactory control with half the recommended rate of glyphosate at 14 DAA. These results demonstrate the possibility of reduced rates of glyphosate when used these adjuvants in the spray mix.
Performance of herbicides mixtures in sugar cane (Saccharum officinarum)
The present work was aimed to evaluate the selectivity and efficiency of herbicides mixtures in sugar cane variety RB 83-5486. Four experiments were carried out in Nova Londrina (PR) and Marilena (PR). In each locality were developed two experiments. The experiments were conducted in randomized blocks, with nine treatments and four replications. In all experiments, the treatments were applied in pre-emergence: T1 (tebuthiuron) + (hexazinone + diuron), T2 (clomazone + ametrina) + (clomazone), T3 (clomazone + ametrina), T4 (trifloxysulfuron sodium + ametrina), T5 (trifloxysulfuron sodium + ametrina) + (hexazinone + diuron), T6 (clomazone + ametrina) + (hexazinone + diuron), T7 (hexazinone + diuron) + (clomazone), and two untreated checks (T8 - weedy and T9 – weed-free). Most treatments caused phytotoxicity in the culture. However, in all experiments, the crop recovered from the phytotoxicity caused by chemical treatments at 100 days after the application. T1 and T7 (Nova Londrina) and T5 and T6 (Marilena) provided total control of weeds up to 100 DAA. In both localities, the biomass accumulation at 150 DAA of the herbicides indicated no significant differences, in comparison with the weed-free ckeck. The weed interference reduced sugar cane biomass from 49,9% (Nova Londrina) to 56,2% (Marilena).
Association of sulfentrazone and glyphosate for weed control in RR® soybean
The use of herbicides with residual activity in weed management has become a common practice in order to reduce weed initial competition. This study aims to evaluate the selectivity and efficiency of the sulfentrazone + glyphosate association at pre-planting management, supplemented with postemergence glyphosate. To reach such intent, an experiment was conducted in Bandeirantes – Pr, on a Eutrophic latosol. The experimental design was randomized blocks in split plot scheme with 11 treatments and 04 replicates. The main weeds in the experimental area (Bidens pilosa, Commelina benghalensis) were in full vegetative growth at the time of application management. During this period, injury caused by treatment to soybean crop, weed density, and grain yield were evaluated. The results showed that sulfentrazone significantly reduced the density of Bidens pilosa and Commelina benghalensis, which ensured an increase in yield of up to 22.49%. In addition, no symptoms of injury were observed by the use of herbicides.
RESISTANCEOF BEGGARTICKS (Bidens subalternans L.) IN FARMING OF SOY OF RIO GRANDE DO SUL
Weed herbicide resistance is a phenomenon defined as ability of a biotype survives to herbicide sprayed, at a recommended rate that control a susceptible population. This research had the objective of determine, the level of resistance the herbicides of the Bidens subalternans. The herbicides treatments they were with bentazon, fomesafen, imazethapyr e chloransulam-methyl. Sprayed in post-emergency, when B. subalternans reached stage four-leaf pairs. The herbicide rates sprayed was crescents in a logarithm scale of 0,0; 0,001; 0,01; 0,1; 1,0; 10 e 100 times of the control recommended rate. Through visual evolution and with aid of the percentile scale they were obtained the control data. The ratio between the C50 of the resistant biotype, and C50 of the susceptible biotype (R/S) were 0,79, 1,87, 53,69 and 486,02 to the herbicides bentazon, fomesafen, imazethapyr and chloransulam-methyl, respectively. The weed herbicide resistance happen in Rio Grande do Sul soybean fields and the biotypes R of B. subalternans presented high level of cross-resistance the herbicides inhibitions of ALS, of the chemical groups of the imidazolinones and sulfonanilides.
NODULATION AND GROWTH OF SOYBEAN IAC-19 PLANTS WITH APPLICATION OF THE HERBICIDES DICLOSULAMAND FLUMETSULAM
In order to study the influence of the herbicides diclosulam and flumetsulam on soybean IAC-19 growth and nodulation, an experiment was carried out in pots, in greenhouse, using sandy-loam and clay soils. The seeds were inoculated with Bradyrhizobium japonicum. The treatments were: no herbicide and no innoculation, no herbicide with innoculation, diclosulam at 16,8, 33,6 and 50,4 g/ha; flumetsulam at 60, 120 and 180 g/ha, applied in pre-emergence, all innoculated. Nodulation was evaluated at 41 days after treatment (DAT). Plants height were also measured. At the end of the crop cycle fresh and dry weight of pods and grains were obtained. Both herbicides showed to be very selective to the soybean at the low and recommended rates. Flumetsulan, at 180 g/ha caused some plant stunting and reduced roots dry weight, at 41 DAT. Soybean plants grew better in the sandy-loam soil, due to its physical characteristics. The herbicides were tolerated by the bacteria, with no reduction in number, fresh or nodules dry weight.
EFFICACY OF FLUMIOXAZIN, APPLIED ISOLATEDAND MIXTURE WITH GLYPHOSATE, FOR WEED CONTROL IN CITRUS
It was evaluate the efficacy of the herbicide flumioxazin, applied isolated and in mixture with glyphosate, in orange orchard, for control of Panicum maximum, Cenchrus echinatus, Digitaria horizontalis, Alternanthera tenella, Bidens pilosa, Malvastrum coromandelianum, Commelina benghalensis, Amaranthus spinosus and Ageratum conyzoides. The treatments were: 0.025 and 0.05 kg ha-1 of flumioxazin (plus mineral oil 0.5%); 0.025 kg ha-1 of flumioxazin plus 1,08 kg e.a. ha-1 of glyphosate (plus mineral oil 0.5%); 0.025 kg ha-1 of flumioxazin plus 1.44 kg e.a. ha-1 of glyphosate (plus mineral oil 0.5%); 1.08 and 1.44 kg e.a. ha-1 of glyphosate. It was kept two checks: weeded and hand hoed. The herbicides were applied using costal sprayer, constant pressure (30 lbf pol-2), with four nozzles Teejet XR 110.02. The equivalent spray volume was 200 L ha-1 . The weed control evaluations were realized 7, 13, 29, 50, 70 and 133 days after herbicide application, in percentages. It was also evaluated herbicide fitotoxicity toculture. The mixture of flumioxazin with glyphosate, as well as isolated glyphosate, resulted in excellent weed control, in all dosages tested. Not were observed intoxication in citrus plants.
MANEJO DE AZEVÉM RESISTENTE AO GLYPHOSATE EM POMARES DE MAÇÃ COM HERBICIDA SELECT (CLETHODIM)
Glyphosate is a broad spectrum herbicide, used for more than 15 years in apple orchards in the Vacaria-RS region for vegetation management on the crops row. In general, 3-4 glyphosate applications are done in each crop cycle with the normal herbicide rate of 720-1,080 g e.a. ha-¹ . Lolium multiflorum is a frequently found weed specie in orchards and regularly sensible to glyphosate. Biotypes of Lolium multiflorum resistant to the glyphosate did not show any significant glyphosate symptoms. Clethodim is a highly efficient grass herbicide for Lolium multiflorum control. An experiment was carried out under field conditions during 2004 growing season in order to study the effects of herbicide Select (clethodim) on a ryegrass glyphosate resistant biotypes. The results indicated that the lower tested rate (Select 0,25 L ha-1 or clethodim 60 g ha-1) gave 99% control while the higher rates (0,30 and 0,35 L ha-1) gave 100% control.
EFFECT OF GROWTH REGULATOR HERBICIDES APPLIED AT DIFFERENT STAGES OF DEVELOPMENT IN WHEAT
The phytotoxicity level caused by hormonal herbicides that work as growth regulators in wheat plants is associated with the growth stage of the apical meristem. Applications of such herbicides when wheat plants are at double ridge and at terminal spikelet stages are very unlikely to cause damage to the ear and to the grain production. So, it is necessary to determine precisely the stages of plant development for having a secure use of these herbicides. However, small alterations may occur as a function of the environmental conditions, the mode of translocation of the herbicides, and tiller development. So, to determine the effect of the application of hormonal herbicide in two wheat cultivars (Embrapa 18 and BR 23), two field experiments were established. The application of hormonal herbicides at double ridge and at terminal spikelet stages did not cause any damage to the ears or to grain production. Applications before such stages caused deformities in the ears, flag leaves, and did no harm to grain yield. Applications after such stages reduced grain yield significantly for both cultivars, reaching the level of 60% reduction. The number of grains per ear was the component that mostly reduced grain yield for both cultivars.
PHYTOTOXICTY OF SULFONYLUREA IN TWO POTATO CULTIVARS
In 2004, abnormalities in the formation of potato tubers were observed in the region of Casa Branca and Aguaí, São Paulo State, Brazil, due to the contamination of sprayer tanks with sulfonylurea. Most of the tubers from all plants presented many cracks and other deffects that disqualified them commercially. Potato response to simulated tank contamination of three sulfonylurea herbicides was evaluated in pot studies in Águas da Prata, São Paulo State, Brazil. Metsulfuronmethyl, nicosulfuron and sulfometuron-methyl were applied in post-emergence in Atlantic and Lady Roseta cultivars at rates corresponding to 0, 0.00001, 0.0001, 0.001, 0.01, 0.1 and 1 times the recommended use rate of each one, corresponding to 3 g ha-1, 60 g ha-1 aand 15 g ha-1, respectively. Potato foliar injury was evaluated visually 5, 20, 35 and 42 days after treatment on a scale of 0 to 100, with 0 indicating no injury, and 100 a complete kill. There was not product effect on average plant height. None of the dosage applied kill the potato plants. Potato foliar injury was generally most severe with metsulfuron-methyl and least severe with nicosulfuron. In general, for the Atlantic cultivar, the phytotoxicity increased exponentially with increased sulfometuron-methyl dosage, for all evaluations. For metsulfuron-methyl and nicosulfuron, the phytotoxicity increased according to a second order equation. For the Lady Rosetta cultivar, the phytotoxicity increased exponentially at 5 and 20 days, but at 35 days, for metsulfuron-methyl and sulfometuron-methyl, increased following a second order equation. All products, specially metsulfuron-methyl and sulfometuron-methyl, delayed notably the vegetative cycle, even at lowest dosages.
NO-TILLAGE EFFECT IN YELLOW NUTSEDGE (Cyperus rotundus L.) AND OTHER WEED SPECIES CONTROL AT MAIZE CROP
It was aimed at in this work to evaluate the population dynamics of yellow nutsedge (Cyperus rotundus L.) and of other species of weeds at maize (Zea mays L.) crop also cultivated for grain and for silage, under no-tillage and conventional tillage of the soil conditions. In the first year, the maize was cultivated in total area, being half of the area in no-tillage and the other half in conventional tillage. Later each area was splitted in two plots: one to produce maize for grain and other to produce maize for silage. They were appraised: a) weed plants before the desiccation and/or the soil tillage and after the crop of the maize and bean; b) weed control after the application of the herbicides in post-emergency at the maize. It was ended that: the type of management of the soil influence C. rotundus L. control that was observed independently in the areas where it was made the no-tillage, whether maize for grain or silage. There was no increase of C. rotundus L. infestation at conventional tillage. Infestation of the other weeds species was not influenced by the type of the soil management or maize cultivation system, except the lyon velvet bean (Stizolobium niveum Kuntze), that had infestation at maize for silage.
Performance of foransulfuron + iodosulfuron and imazapic + imazapyr on Bidens spp. biotypes
Bidens spp. especies are present in 74% of the farms of central plateaus of the state of Rio Grande Do Sul, Brazil. The species Bidens pilosa was the first weed to be documented as resistant to herbicides inhibitors of the enzyme acetholactate sinthase (ALS), in Brazil. Foransulfuron + iodosulfuron and imazapic + imazapyr are ALS inhibitors recently launched to use on the corn crop. Since, there is no record of the action of these herbicidas on resistant Bidens spp. biotypes, the objective of this work was to evaluate the performance of foransulfuron + iodosulfuron and imazapic + imazapyr on biotypes collected in several places in Brazil. Experiments were conducted in the greenhouse at Federal University at Rio Grande do Sul. Seeds of Bidens spp. had been sown in trays with capacity for 2000 ml, with soil:sand substratum (2:1). After emergence, seedlings were transfered to vases with 300 ml capacity and kept irrigated. When seedlings had reached the four leaved stage they were sprayed with the herbicides with rates from 0 up to 8 times the recommended dose. The experimental design was a complete random design with four replicates. At 21 days after the application it was evaluated the plant control. The results had been submitted to the analysis of variance and when evidenced interaction of biotype and rate, dose-response curves had been adjusted, for each biotype. The results confirmed difference of sensitivity to the herbicides between the tested biotypes. The biotypes susceptible to other ALS inhibitors had confirmed its susceptibility to the herbicidas foransulfuron + iodosulfuron and imazapic + imazapyr. But, the biotypes resistant to other ALS-inhibitors were also resistant to these herbicidas. The mixtures of foransulfuron + iodosulfuron and imazapic + imazapyr are new herbicidas for the corn crop but do not solve the problem of ALS-resistance in Bidens spp.
SELECTIVITY OF HERBICIDES FOR Stylosanthes capitata and S. macrocephala
Aiming to study the herbicides selectivity at pre-emergence: diclosulam (35,28 g a.i./ha), flumetsulan (120 g a.i./ha), flumioxazin (50 g a.i./ha), imazaquin (30 g a.i./ha), smetolachlor (1.920 g a.i./ha) and sulfentrazone (600 g a.i./ha) and post-emergence: flumioxazin (25 g a.i./ha), 2,4-D (840 g a.i./ha), 2,4-D (536 g a.i./ha), bentazon/acifluorfensodium (450 g a.i./ha), acifluorfen-sodium/bentazon (240 g a.i./ha), chlorimuron-ethy (l17,5 g a.i./ha), fomesafen (250 g a.i./ha), imazethapyr (100 g a.i./ha) and lactofen (168 g a.i./ha), in Stylosanthes capitata and S. macrocephala, field trails were carried out in Quartzpsament soil and Haplorthox soil in Campo Grande, Mato Grosso do Sul State, Brazil. The pre-emergence trials were installed in the two soil types and for each one of the legume species and, to the post-emergence, the trails were only installed in Haplorthox soil and for both species of the forage legume. The evaluations were phytotoxicity of the herbicides through visual assessment at 10, 20, 30 and 40 days after the application of the treatments (DAT), and 15 and 40 DAT to the post-emergent one. In Haplorthox soil, it was selected the products imazaquin and diclosulam. In Quartzpsament soil, none of the applied herbicides was selective for the plants. To the post-emergent ones, the herbicides tested did not provide high levels of phytotoxicity and the ones that more affected the plants were 2,4-D, flumioxazin, followed by chlorimuron-ethyl. The herbicides lactofen, imazethapyr, fomesafen, acifluorfensodium/bentazon and bentazon/acifluorfen-sodium, in post-emergence, showed promising results to control weeds in areas of Stylosanthes seed production.
POST-EMERGENCE APPLICATION OF GLYPHOSATE ON TRANSGENIC SOYBEAN GROWN IN THE CERRADO ABSTRACT
The experiment was installed on a transgenic soybean field (Glycine max (L.) Merrill), variety Soy 8888-RR, planted on January 11, 1999. One glyphosate application at 1.2 kg/L was performed before seeding, which was carried out seven days after that management practice, in the no-till system. The products were applied in the entire area of the plot, using a carbon dioxide (CO2) precision sprayer. Treatments consisted of: glyphosate at 0.48; 0.72; 0.96; 1.20 and 1.44 kg/ha, applied 31 days after emergence (DAE); glyphosate at 0.72 kg/ha 22 DAE and at 0.48 kg/ha applied 42 DAE; glyphosate at 0.96 kg/ha applied 22 DAE and at 0.72 kg/ha applied 42 DAE; chlorimuron-ethyl + lactofen at 0.01 + 0,072 kg/ha, respectively, applied 31 DAE, plus hand-weeded and unweeded controls. The evaluated parameters consisted of apparent phytotoxicity at 15, 20, 42 and 51 days after treatment application (DAA), plant height and agronomic efficiency at 20 and 51 DAA, and grain yield. From the results obtained, it can be seen that glyphosate at the employed formulation, regardless of the concentration used, showed a very slight apparent phytotoxicity effect on the soybean plants, and was efficient in controlling the existing weeds with a single or with two sequential applications.
ISOXAFLUTOLE PERSISTENCE IN A CLAY SOIL CULTIVATED WITH POTATO
In order to study the isoxaflutole persistence in a clay soil cultivated with potato cv. Monalisa, a field experiment was carried out at Bayer CropScience Experimental Station, in Paulínia - SP. A complete split-plot randomized block design with four replication was used. In the main plots were studied the rates 0, 75, 150 and 300 g ai/ha in a pre-emergence application. On the day of treatment and at seven day intervals until 140 days after treatment, except at 119 days, soil cores were taken from each plot. The isoxaflutole residual activity was evaluated by bioassay using bean (Phaseolus vulgaris L. cv Eté) as a test-plant. The isoxaflutole persistence of each rate was analyzed by regression analysis, with time as the independent variable and rate herbicide remaining as the dependent variable. The lost of the isoxaflutole residual activity in a clay soil was very slow. For the 75 and 150 g/ha rates, the residual period were, respectively, 84 and 112 days; it was observed recharge activity at 70 and 98 days. For the 300 g/ha rate, residual period was greater than 140 days.
GLYPHOSATE AND GLUFOSINATE AS SELECTIVE AGENTS FOR GENETIC TRANSFORMATION OF YELLOW PASSION FRUIT (Passiflora edulis f. flavicarpa Deg.)
The yellow passion fruit is one of the most interesting economic species of Passifloraceae family. The biotechnology tools are useful to solve some problems that affect the productive potencial of this specie, like fungal and bacterial diseases, and the creation of more productivity varieties. In this context an experiment of yellow passion fruit was corried out to evaluate the glyphosate and gluphosinato herbicides as selective agents for genetic transformation. The culture medium used was Murashige & Skoog (1962) supplemented with B5 vitamin and organic complex, 30 g.L-1 sucrose, 100 mg.L-1 inositol, 1 mg.L-1 6– benzilaminopurina, solidified with 2,6 g.L-1 Phytagel. The experimental design was entire occasional and the bud regeneration and rooting formation experiments were evaluated. The glyphosate concentrations used in experiments of bud regeneration were: 0; 0,2; 0,4; 0,6; 0,8; 1,0 mg.L-1, for rooting experiments: 0; 0,05; 0,1; 0,15; 0,20; 0,30; 0,40 mg.L-1. The glufosinate treatments for bud regeneration were: 0,0; 0,2; 0,4; 0,6; 0,8 mg.L-1 and for rooting experiments: 0,0; 0,1; 0,15; 0,20; 0,25 mg.L-1. Number of explant with shoots and number of shoots per explant were evaluated in the experiment of caulogenesis. For rooting evaluation: number of rooted apexes, root size, primary root number and root fresh weight. Both herbicides glyphosate and glufosinate were efficient in the inhibition of the bud regeneration to a low concentration (0,785 mg.L-1 e 0,768mg.L-1 respectively), as well as in the inhibition of rooting (0,404 mg.L-1 e 0,249 mg.L-1 respectively). That allows the recommendation of those herbicides as selective agents in tissue culture of passion fruit for works of genetic transfer.
EFFECTIVENESS AND SELECTIVITY OF FLUMIOXAZIN HERBICIDE IN PRÉ-EMERGENCY ON ONION CULTURE TRANSPLANTED
The work was carried out to evaluate the herbicide flumioxazin performance compared to commercial patterns applied in pre-emergency in the transplanted onion culture. Field trials were carried out in Monte Alto, SP, arranged in a randomized complete block design with four repetitions. The used herbicides were: flumioxazin (0,080; 0,120; 0,180; 0,240 kg ha-1), oxadiazon + linuron (0,500 + 0,900 kg ha-1), linuron (1,350 kg ha-1) and oxadiazon (0,75 kg ha-1). Two controls also were maintained, one with and other without weed control during all the culture cycle. The portions consisted of four spaced lines of 0,36 m and three meters in length each, totalling 4,32 m2 area. Were considering useful the three central lines. The distance among plants in the line was 0,36 m. All the herbicides were considered excellent for the Lepidium virginicum control, standing out flumioxazin (100%) in all the dosages, until the 80 days after application (DAA), with great selectivity for the culture. The plants recovered well of the initial symptoms of the oxadiazon (0,750 kg ha-1). The mixture oxadiazon + linuron (0,500 + 0,900 kg ha-1) as well as isolated linuron (1,350 kg ha-1), promoted fitotoxicity varying moderate to medium.
Selectivity and efficacy of herbicides to winter cereals
An experiment was carried-out with the objective of evaluating the selectivity and efficacy of herbicides applied for weed control on winter cereals. The experiment was conducted under field conditions at the field station of Embrapa, in Passo Fundo, RS, during the 2005 growing season. The soil of the station is a loam Oxisol. The evaluated crops were wheat, barley, rye and triticale. Black oats, oats, turnipseed and vetch were sown in order to act as volunteer crops interfering with those crops. The tested herbicides were bentazon, metsulfuron-methyl, dichlofop-methyl clodinafop-propargyl, 2,4-D, 2,4-D + picloran, 2,4-D + glyphosate (as sequential application) and iodosulfuron-methyl. The pre-emergence treatments were applied in 23/06/2005, one day before sowing the crops. The post-emergence treatments were applied in 27/07/2005 at the 3-5 leave weed stage. The results indicated that the treatments were selective to wheat, triticale and rye while barley was the species more sensible to them especially to iodosulfuron-methyl. Black oats, oats, and ryegrass responded differently to the treatments according to the tested rate while turnipseed and vetch are efficiently controlled by iodosulfuron-methyl, 2,4-D and 2,4- D + picloram.
Effect of soil moisture status on carfentrazone-ethyl selectivity and weed control on soybeans
The effects of soil water and, by inference, the plant water status prior to herbicide treatment, on the response of soybean and Euphorbia heterophylla L. to carfentrazoneethyl applied alone and in mixture with imazethapyr were studied under field conditions. The study was conducted during the 2001/2002 growing season. The experimental design was a split block in strips with four replications. The strips consisted of irrigation (irrigation and no-irrigation) and herbicide. The irrigation consisted of an event of 30 mm of water 2 which was carried-out in the day prior to herbicide application using sprinklers. The herbicides were carfentrazone-ethyl 10,0 g a. i. ha-1, carfentrazone-ethyl 10,0 g a . i./ha + imazethapyr 24,5 g a. i./ha. A check and a hoed treatment were included. High moisture status plants (irrigated) were more sensitive to carfentrazone-ethyl applied alone and in mixture with imazethapyr than unirrigated plants. The best E. heterophylla control was given by carfentrazone-ethyl 10,0 g a . i./ha1 + imazethapyr 24,5 g a. i./ha. Soybean plants recovered from the initial phytotoxicity caused by carfentrazone-ethyl treatments and there was neither effect on the final plant height or biomass and grain yield.
PRE-HARVEST DESICCANTS EFFECT ON THE PHYSIOLOGICAL QUALITY OF DRY BEAN SEEDS
One of the strategies to improve the mechanic harvest performance is using desiccants in pre-harvest application. Thus, an experiment was carried at “Fundação ABC” experimental area during 2001/2002 season, in Arapoti, Parana State, Brazil. The aim of the study was to evaluate the pre-harvest desiccants effect on common bean seeds quality (germination and vigor) after harvest and after a period of 8 month of storage. The variety Carioca under no tillage system was used. The treatments were applied using a pressured and manual pulverization when the crop shows 55% dry pods. The experimental design was random blocks with 10 treatments and 4 replications (g a.i. ha-1): glufosinate-ammonium + ethephon (120 + 100) + Hoefix (0.2%), glufosinate-ammonium + ethephon (120 + 100) + Agral (0.1%); glufosinate-ammonium + ethephon (240 + 200, and 480 + 400); diquat (300 and 600); glufosinate-ammonium (300); paraquat (240); glyphosate (720), and the control, without application. The averages were compared with the DMS test with 5% of probability. The treatments glufosinate-ammonium + etephon (440 and 880 g a.i. ha-1), diquat (33 and 600 g a.i. ha-1), and glufosinate-ammonium (300 g a.i. ha-1) were adequate desiccants and not affected the germination and vigor of the seeds. Paraquat (240 g a.i. ha-1) and glyphosate (720 g a.i. ha-1) shown less efficiency and affected the germination, since that gliphosate affect the seeds vigor.
Atrazine leaching in water in a recharge area of Guarany aquifer in Brazil
The Espraiado watershed is located on a recharge area of the Guarany aquifer, the most important source of groundwater in South Central Brazil. The presence of crops in which herbicides of triazine group are used and sandy soils make the area vulnerable to leaching. One of the herbicide used is atrazine (2-chloro-4-(ethylamino)- 6-(isopropylamino)-S-triazine). Due to its physical and chemical characteristics, atrazine has a high potential to leach into groundwater. In order to evaluate atrazine leaching in the soil, surface and groundwater samples have been collected during the period of 2000 to 2002. Soil physical properties have been determined and water samples submitted to analysis by HPLC (High Performance Liquid Chromatography) followed by GC-MS (Gas chromatography-Mass Spectrometry) for confirmation. Among all surface water samples collected, only four have shown atrazine residues, two with 0.04 and others with 0.05 and 0.09 µg/L. Only one ground water sample has shown residue at level of 0.03 µg/L None of those sample residue level has been confirmed with the CG-MS thus indicating no residue. The leaching potential has also been evaluated by mathematical modelling simulation using the Chemical Movement in Layered Soils- CMLS-94. The simulator has also shown that atrazine did not reach the aquifer.
EFFECTS OF A COMMERCIAL MIXTURE OF AMETRYNE PLUS SIMAZINE WITH GLYPHOSATE AND PARAQUAT FOR WEED CONTROL IN COFFEE CROP
This research was conducted from 01/06 to 03/08/98 at the location of Irai de Minas, with the objective of evaluating the biological activity of a commercial mixture of ametryne plus simazine with glyphosate and paraquat, for the control of Brachiaria plantaginea, Digitaria horizontalis, Amaranthus hybridus, Commelina benghalensis and Eleusine indica in a Catucai coffee crop. Treatments were constituted of two doses (2500+960 and 3000+960 g.ha-1) of the commercial mixture of ametryne plus simazine with glyphosate, two doses (2500+300 and 3000+300 g.ha-1) of ametryne plus simazine with paraquat compared with a single dose (2500+300 g.ha-1) of diuron with paraquat and two check treatments with no herbicides (hoeing and without hoeing). It was utilized a back-packed manual sprayer pressurized with CO2 at 39 lb/in2 , with four tee-jet nozzles 110.02 XR, calibrated at a flow rate of 200 liters of the solution per hectare. The experimental design used was a randomized complete-block with four replications. The evaluations of weed control were performed at 15, 30, 45 and 60 days after application. It was concluded that: 1) mixtures of ametryne plus simazine with glyphosate at doses of 2500 + 960 g.ha-1, control with efficacy B. plantaginea; 2) mixtures of ametryne plus simazine with glyphosate at doses of 3000 + 960 were efficient for the control of D. horizontalis and C. benghalensis up to 60 DAA and up to 45 DAA in the control of E. indica and A. hybridus; 3) the mixture of ametryne + simazine with paraquat at both doses studied controls efficiently C. benghalensis up to 45 days DAA; 4) the mixture diuron plus paraquat, was efficient for the control of A. hybridus and C. benghalensis.
Selectivity of Diclosulam Herbicide Applied in Pre and Post-emergence over Several Sugarcane Cultivars
The objective of this study was to evaluate the selectivity of diclosulam applied alone in pre or post-emergence to different sugarcane ratoons. The trial was carried out at Barra Bonita town, Brazil. It was used eleven different sugarcane cultivars, as following: RB 72 454, RB 82 5336, RB 83 5089, RB 83 5486, RB 85 5035, RB 85 5156, SP 70 1143, SP 71 1406, SP 79 1011, SP 80 1842 e PO 8503. The treatments used were (i) diclosulam at 200 g h-1 applied in pre-emergence; (ii) diclosulam at 200 g h-1 applied in post-emergence; and (iii) and an untreated check. Visual injury evaluations were done after applications. Technologic and productive parameters were analyzed at harvest timing, as Pol, Brix, fiber, straw diameter, straw number, straw length, straw and sugar yield. Only the cultivars RB 85 5035 and RB 85 5156 showed visual symptoms of intoxication provided by diclosulam in both applications pre or post-emergence. The symptoms disappeared completely during the sugarcane cycle. The technologic characteristics as Pol, fiber and Brix were not influenced by the diclosulam herbicide.
ADSORÇÃO DE ATRAZINA, DESETILATRAZINA E HIDROXIATRAZINA EM LATOSSOLO VERMELHO ESCURO SOB CERRADO E SOB PLANTIO DIRETO NO DISTRITO FEDERAL
The environmental fate of a pesticide depends on many factors, among them the soil characteristics as mineralogy, soil chemistry and organic matter content. This study aims to verify how the adaptation of chemical and mineralogical properties of a dark red latosol from the Brazilian savanna under the continuous use of no till practice can affect its affinity to atrazine and two metabolites (deethylatrazine and hydroxyatrazine). Therefore, beyond the characterization of the cited parameters, batch studies were performed with both no till and native vegetation soils. The comparison between them showed that the changes in some soil properties due to agriculture use of it were enough to change significantly its affinity for the studied compounds. Atrazine and deethylatrazine showed significant affinity to the high organic matter content horizon, while deeper horizons with smaller amounts of organic matter atrazine sorption was neglectible, deethylatrazine was present, but in smaller amounts.
CONTROLE DE GRAMÍNEAS EM SOLOS DE VÁRZEA
The aim of this work was to evaluate the effects of herbicides and tillage systems used to control weeds, on corn, soybeans and sorghum crops, cultivated in sequence of irrigated rice. These crops were grown in no-till, minimum tillage and conventional systems in Hidromorfic Soil. The best results for these crops in that kinds of soil were achieved with the conventional system. The sorghum crop stood out that objective, when compared to the other two crops. The atrazine herbicide used in sorghum, attained 80% of grasses control, while s-metolachlor (soybean) and atrazine + s-metolachlor (corn) accomplished 70% and 50%, respectively. The maximum technical efficiency ratio for atrazine and smetolachlor herbicides was, respectively 3.85 and 3.26 l/ha (c.p.), no matter the tillage system used. There were interactions with ratios and tillage systems when atrazine + smetolachlor was used (corn). The maximum technical efficiency ratio to that herbicide on minimum tillage was 5.7 l/ha (c.p.), on no-till was 3.9 l/ha (c.p.) and on conventional system was 3.65 l/ha (c.p.).
EFFICIENCY OF HERBICIDE FORAMSULFURON + IODOSULFURON TO CONTROL WEEDS IN CORN PLANTATIONS
The objective of this study was to determine efficiency of herbicide foramsulfuron + iodosulfuron applied as post-emergence to control weeds in corn plantations. The experiment was established at UNIOESTE – Campus de Marechal Cândido Rondon, from October 2000 to March 2001. The postemergence application of the herbicides was executed at the 4 – 5 fully expanded corn leaves. We used a backpack pulverizer at constant pressure (CO2) of 2,1 Kgf/cm2 and a bar equipped with 6 XR Teejet 110-02 nozzles that delivered 200 l/ha. The experimental design was a randomized block design with 4 repetitions. Treatments consisted of: foramsulfuron (35 and 45.3 g/ha), foramsulfuron + iodosulfuron (36 + 2.4 e 45 + 3 g/ha), foramsulfuron + atrazine (35 + 1000 and 45.5 + 1000 g/ha), nicosulfuron (50 g/ha), hoed and non hoed control. All products had excellent control of weeds present on the experimental plots. None of the herbicides caused any injury to the corn. No significant difference in corn production was detected as result of the tested herbicides. On the other hand, all treatments yielded corn production superior to the non hoed control.
METHODOLOGY FOR STUDY OF SELECTIVITY OF HERBICIDES IN THE CULTURE OF SUGAR-CANE (Saccharum spp)
Studies on herbicides selectivity in the culture sugar-cane, they plows generally done together with rehearsals of effectiveness on harmful plants and always being used the witness by experimental block. When the contrast treatment is analyzed with herbicide in relation to an only witness without herbicide, there is a tendency in obtaining larger values for the variation coefficient, being able to not in that way, to hide some non selective herbicides. Therefore, the objective of the present work, specifically went evaluate to herbicides selectivity about the production of stems of the sugar-cane, constantly staying the portions weeded, and being used two lateral witness adjacent to each treatment with herbicide. With that methodology, the results showed that the herbicides 2,4-D + ametryn (1,34 +1,50 l i.a./ ha), tebuthiuron + diuron (0,96 + 1,25 l i.a/ ha), 2,4-D + hexazinone + diuron (1,34 + 0,27 + 0,94 l i.a./ ha), ametryn (1,50 l i.a./ ha), tebuthiuron (0,96 l i.a./ ha) and tebuthiuron + ametryn (0,96 + 1,50 l i.a/ ha) they reduced the stems production significantly in 19,5; 17,0; 16,6; 15,1; 11,9 and 10,9 t ha-1 respectively, with levels of smaller significance than 3%. Therefore, such products were not considered selective the cv. RB 835089 when applied in the powder-emergency of the culture.
SUPEROXIDE DISMUTASE ACTIVITY IN SOYBEAN (Glycine max L.) PLANTS CULTIVED UNDER OXIDATIVE STRESS CAUSED BY HERBICIDE
Some herbicides frequently used in economical main crops, such as soybean, cause oxidative stress in aerobical organisms, characterized by formation of oxygen reactive species, like superoxide radicals. Superoxide dismutase (SOD) is an enzyme that plays important role in response to oxidative stress in plants, by acting over superoxide radical, forming hydrogen peroxide and molecular oxygen. The aim of this research was to determine the activity of SOD in order to verify your action to protect soybean plants protection against oxidative stress induced by oxyfluorfen, and also the lipoperoxide content formed in the experiment conditions. Oxyfluorfen was applied at 2500, 5000 and 10000 mg/L. Soybean plants were sprayed at different development phases (16, 23 and 30 days after germination). Samples of shoot were collected 24, 48 and 72 hours after application. The experimental design used was completely randomized, in factorial arrangement (4x3), with five replications. It was observed that oxyfluorfen at 2500 and 10000 mg/L increased SOD activity, while lipoperoxide content increased in plants submitted with all concentrations. The results showed that SOD has action against oxidative stress induced by oxyfluorfen in soybean plants.
Study of the surface tension in drops of solutions with surfactants of agricultural use
The present work had the objective to study the behavior of the superficial tension in solution drops elaborated with different surfactants concentrations. To analyze the tension he/she made himself weight of the drops formed in the extremity of the burette, with the following combined treatments of form factorial (15x12) 15 surfactants (Ag-Bem, Agral, Aterbane BR, Agrex, Break Thru, Extravon, Energic, Fixade, Gotafix, Haiten, Herbitensil, Iharaguem, Lanzar, Silwet L-77 and Will Fix) and 12 concentrations (0; 0,001; 0,0025; 0,005; 0,01; 0,025; 0,05; 0,1; 0,25; 0,5%; 1 and 2%) in to total of 180 treatments. Analyze it statistics of the dates it was accomplished with I aid of the SAS program and it goes it analyzes of regression, the model of adjusted Mitscherlich was adopted and modified it goes the obtained it dates. It was observed that the surfactants organosilicons Break Thru and Silwet reduced the surface tension significantly (19,87 and 19,08 mN/m; respectively) and they presented the highest coefficients of effectiveness (169,81 and 143,43). Will Fix and Agrex in spite of they have presented low coefficients of effectiveness (1,52 and 4,01; respectively), they reduced the superficial tension significantly (24,71 and 29,29 mN/m) they put in the close high concentration attn 2% v/ v. The other surfactants presented quit close minimum tensions; the comparison among them can be made exclusively by the coefficient of effectiveness.
RATES OF METOLACHLOR IN COMMON BEAN (Phaseolus vulgaris L.) DEVELOPMENT
In Brazil, the maize crop presents the biggest consumption of metolachlor herbicide; however, with the increase of winter beans cultivated area, this culture became an important market for this product. The work was developed in FCA/UNESP, Botucatu, SP, with objective to evaluate rates of the metolachlor herbicide in the common bean, being used cultivar FT Bonito, in winter season. the development stadiums V2, V3 and V4. The treatments had been constituted of five doses (0; 1,0; 2,0; 3,0; 4,0 and 5,0 L/ha) totalizing 6 treatments with 5 repetitions. The herbicide was applied in pre-emergency, being carried through the following evaluations in the stadio V2, V3 and V4, corresponding to the unfolding of primary leaves, emission of the first trifoliate leaf and emission of the third trifoliate leaf: height of plants; dry matter of shoot and symptoms of toxicity. It was verified that in relation to the height of plants in the V2 stadium was not verified significant difference. However, it was observed the occurrence symptoms of toxicity, that were more intense in the biggest rate of herbicide. Despite the reduction in the development of the plants in three development stadiums it did not have reduction in the production of dry matter.
SELETIVIDADE E EFICIÊNCIA DO HERBICIDA FLUMICLORAC-PENTIL NO CONTROLE DE Euphorbia heterophylla L. NA CULTURA DE SOJA
The selectivity and efficacy of flumiclorac-pentil applied alone and as tank mixture with imazethapyr or cloransulam-metil on Euphorbia heterophylla L. were studied under field conditions. The study was conducted during the 2000/2001 growing season. The experimental design was a randomized completely block with four replications. The treatments (rate of active ingrediente per hectare) consisted of flumiclorac-pentil (60 gi.a./ha), flumiclorac-pentil (40 g) + imazethapyr (59,5 g), flumiclorac-pentil (40 g) + cloransulam-metil (30 g), imazethapyr (98 g) and cloransulam-metil (41 g). A check and a hoed treatment were included. The treatmens that included flumiclorac-pentil (applied alone and as tank mixture with the herbicides) plus Assist at 0,5 % (mineral oil) caused higher injury to the crop which varied from 27,0 to 33,7 % at the assessment carried-out at 5 days after treatment applicatio (DAT). The injury symptoms were identified as curling and scorch mainly in recently emerged leaves. At 14 DAT, the crop was recovering from the symptoms which were seen just in older leaves. All treatments showed more than 95 % and 92,0 % E. heterophylla control at 15 and 30 DAT However, at 30 DAT, flumicloracpentil, applied alone, gave poorer control and was statistically inferior Sto the other herbicide treatments but still with 92,5 % weed control. The same treatment behaviour was observed at 60 DAT. The soybean plants recovered from the initial phytotoxicity caused by flumiclorac-pentil treatments and there was no effect on the grain yield.
Herbicides selectivity on the characteristics of production of the sugarcane using two witnesses
In Brazil studies of herbicides selectivity on the production parameters in sugar cane are generally carried out together with rehearsals of agronomic effectiveness in weeds and always using a checkplot per experimental replicate. When the contrast is analyzed considenry herbicide in relation to only one check without herbicide, there is a tendency in obtaining larger values for the variation coefficient, what could hide some effects of herbicides not selectives. Therefore, the objective of the present work, was specifically evaluate herbicide selectivity on sugarcane yield parameters: diameter, length, number of among knot and production of sugarcane stems, maintaining the portions constantly weeded, and using two lateral checks without herbicide adjacent to each treatment with herbicide. The results showed that in post-emergence, 2,4-D + hexazinone/ diuron (1.34 + 0.27/ 0.94 kg i.a./ there is) affected the diameter and the length of stems signifratinely, reducing the production in 16,6 t/ha. Tebuthiuron (0.96 kg i.a./ha) it affected the diameter, tebuthiuron + diuron (0.96 + 1.25 kg i.a./ha) and diuron + ametryn (1.25 kg i.a.l/ha) affected the number of among knot, reducing the stem production in 11.9; 17.0; 5.5 t/ha respectively. Ametryn (2.25 kg i.a./ha) and oxyfluorfen (0.72 kg i.a./ha) applied in pre-emergence they were not considered selective for the parameter number of among knot, however they didn't cause reduction in the stems production.
EFFECT OF PRE-EMERGENCE HERBICIDES ON THE INITIAL DEVELOPMENT OF TREE SPECEIS
The objective of this work was to evaluate the effect of different treatments with pre-emergent herbicides on the emergence, survival and initial growth of seedlings of tree species from riparian forests. The experiment was conducted in a greenhouse in a randomized blocks design with four replicates and five treatments. The herbicides used were imazapyr, atrazine, acetochlor and oxyfluorfen at the rates of 3,0L p.c./ha, 5,0L p.c./ha, 3,0L p.c./ha e 4,5L p.c./ha, respectively, plus a control treatment (no herbicide). Acetochlor showed satisfactory results in the emergence and seedlings surviving of Senna multijuga, Senna macranthera, Solanum granuloso-leprosum and Trema micrantha. Imazapyr affected all other species but not T. micrantha in the seedlings surviving. Atrazine and oxyfluorfen can be used in some cases but it is necessary a close evaluation of each species. Herbicides did not show better results on the emergence or seedlings survival when compared to the control (no herbicide). Observed phytotoxic effects were 2 similar to those described in the literature. The tested herbicides were efficient to control all weeds found in the control treatment.
EFFICACY OF ACETOCHLOR APPLIED IN POST EMERGENCY ON THE WEEDS IN MAIZE
It intend with experiment evaluate the performance of the acetochlor herbicide by itself tank mix with nicosulfuron, applied in post emergency on the following weeds: Cenchrus echinatus, Digitaria horizontalis, Indigofera hirsuta, Portulaca oleracea, Ipomoea grandifolia. The experiment was conducted at the FCAV-UNESP CAMPUS, in Jaboticabal – SP, on red oxissol. Late on, it was evaluated the possible toxicity symptoms on the maize. The treatments were: acetochlor + nicosulfuron a 1,68 + 0,032; 2,52 + 0,032 and 3,36 + 0,032 Kg/ha, nicosulfuron a 0,032 Kg/ha, in two sprayer age, compered of the witness with and without weeds. The weeds ages application were early (2 leaf) and late (4 to 6 leaf) post emergency. The herbicides were applied with costal sprayer, to constant pressure (40 lbf/pol2 ), with four nozzles XR 11002. The equivalent spray volume was 200 L/ha, and the maize used was Ag 3010. To the C. echinatus the mixture acetochlor + nicosulfuron, in all the rates tested, can are applied latiest, why earned with residual. But to the other weeds evaluated, have to accomplish the herbicides aplication the earliest, and but acetochlor + nicosulfuron mixture have best residual effect. Haven’t diference to control between smaller rate (1,68 + 0,032) and larger rate (3,36 +0,032) at mixture. Despite the slightely reduction in the beginnig on maize treated with acetochlor, they recovered quikly making possible the utilization of the acetochlor on the tested hybrid.
EFFICACY OF GLYPHOSATE POTASSIUM AND BUTAFENACIL MIXTURE ON CONTROL OF Commelina benghalensis IN COFFEA CROP (Coffea arabica)
The objective of this research was to evaluate the efficiency in control of purslane (Commelina benghalensis) with mixtures of glyphosate potassium and butafenacil herbicides on coffee crop in February and May. Two experiments were carried out on Bom Retiro Farm, Vera Cruz-SP, Brazil. The treatments were: post emergence application of glyphosate potassium + butafenacil (100 g i.a./L) (1000+30; 1000+40; 1000+50; 1000+60; 1000+70; 1000+80; 1000+90; 1000+100 g/ha + mineral oil, 0,5% v/v), glyphosate + carfentrazone-ethyl (2000+30 g/ha + mineral oil, 0,5% v/v), glyphosate potassium (1000 g/ha), butafenacil (60 e 100 g/ha + mineral oil, 0,5% v/v) and an untreated control. Experimental design was randomized complete block with four replications. The herbicide butafenacil improved performance of glyphosate potassium in purslane control; glyphosate potassium + butafenacil mixture was efficient to control of purslane above 1000 + 100 g/ha respectably; and glyphosate + carfentrazone-ethyl mixture was efficient to control purslane in all tested doses; the application of herbicides at different seasons (February and May) provided a faster control in a shorter period in February, and the opposite for May, when it happened slower and longer control.
Chemical control of Brachiaria decumbens in pasture of the coast-cross and tifton 85 hybrids (Cynodon dactylon)
Aiming at the control of the Brachiaria decumbens in degraded pastures of the Coast-Cross and Tifton 85 hybrids (Cynodon dactylon), two experiments were carried out, each one for each forage, where increasing doses of the commercial mixture diuron/ MSMA and one dose of MSMA were applied. The randomized block experimental design was used with seven treatments and four replicates. The plots were 6m long and 4m wide. The treatments were applied on the total area and on mature weeds. The diuron / MSMA mixture at the dose of 1120 + 2880 g/ha, respectively, provided efficient control (90%) of B. decumbens at 42 DAA. MSMA at the dose of 2880 g/ha was not effective in controlling B. decumbens over the appraised period, since its control was lower than 70% from 14 to 42 DAA. Diuron / MSMA at the dose of 1120 + 2880 g/ha and MSMA at the dose of 2880 g/ha provided light injuries in C. dactylon hybrids from 7 to 14 DAA, that disappeared at 30 DAA and not affected the development of the forages, so making possible a fast reestablishment of the pasture.
Avaliação da eficiência e seletividade de herbicida Cobra aplicado isolado ou em mistura com CLASSIC na cultura da soja
Foi conduzido um ensaio no município de Serranópolis-GO, com o objetivo de avaliar a eficiência agronômica e seletividade do herbicida COBRA aplicado isolado ou em mistura com CLASSIC, para o controle de plantas daninhas na cultura da soja. Os tratamentos foram: COBRA 0,625 e 0,750l/ha, COBRA + CLASSIC (0,5l + 50g)/ha, CLASSIC 80g/ha, além das testemunha com e sem capina. Conforme resultados conclui se que: a) nas doses testadas os herbicidas foram seletivos para a cultura da soja; b) COBRA + CLASSIC (0,5l + 50g)/ha e CLASSIC 80g/ha apresentaram praticabilidade e eficiência agronômica no controle do carrapicho-rasteiro, picão-preto e erva-palha, podendo, portanto, ser recomendada para o controle destas espécies; c) COBRA 0,750l/há foi eficiente no controle da erva-palha; d) Não foram observadas diferenças significativas entre as produtividades obtidas nos tratamentos químicos e a testemunha capinada.
EFFICIENCY OF HERBICIDA FLAZASULFURON IN THE CONTROL OF WEEDS IN SUGAR-CANE AND ITS EFFECTS IN THE GROWTH AND PRODUCTIVITY OF THE CULTURE
The objective this study was to evaluate the tolerance of the sugar-cane to the flazasulfuron and the herbicide efficiency on the Cyperus rotundus control. The experiment was carried on a sandy soil texture, at the Usina Destivale, at Araçatuba, SP. The used variety was RB 72-454. A randomized block design was used, with 12 treatments and 4 repetitions. The herbicides were applied in post-emergency of the crop and weeds, at 20 and 45 days after the plantation. The seletivity to the herbicides was evaluated to the sugar-cane and the efficiency in the control of the weeds by visual evaluations and number of tubers. It was also evaluated the effect of the treatments on the crop growth and yield. It was concluded that the flazasulfuron, at 100, 125, 150, 37.5+37.5, 50+50, 62.5+62.5 and 75+75 g/ha, was selective to the crop of the sugar-cane and efficient in controling of C. rotundus, providing average reduction of 80% in the number of viable tubers of purple nutsedge. The yield of the sugar-cane was of 81.2 t/ha against 55.6 t/ha of the control without weeding. At 50 and 75 g/ha, the herbicide was not very efficient. The herbicide 2,4-D was not very efficient in the control of the purple nutsedge and MSMA was efficient until 45 days after the first application, with 85% of control.
SULFENTRAZONE MOBILITY IN THE PROFILE OF CLASSES OF SOILS
The objective of this study was to determine the mobility of sulfentrazone in two soils classes as a function of increasing rain indices, as well as possible influences of the chemical and physical properties of soils with different iron oxides contents, on the herbicide action. The containers were 36 PVC tubes (10 cm diameter X 50 cm long). The containers were filled with soils and irrigated in 65%(w/w) and, then, the application of sulfentrazone (800g a.i/ha) was done on the exposed area. Subsequently, daily rainfalls of 10mm were simulated and, as the desired rain indices were reached (30, 60 and 90mm), six PVC tubes from each soil (with and without application) were disassembled. Five sorghum (Sorghum bicolor) seeds were sowing on soil from the depths 2,5-7,5-12,5-17,5-22,5-30,0 cm, and were maintained in a greenhouse for 15 days to evaluation of the germination and initial growth. After this time, an evaluation of possible morphophysiological changes that could be characterized as toxic effects of the product was done and the length of the shoot up to the last visible ligule. After measurement the shoots were dried in a forced draught over (70°C for 96h) to determine the dry matter. The results indicated that on the Dusky Red Latosol (Typic Acrustox) the product was percolated down to 12,5 cm with 90mm rainfall and on the Yellowish Red Latosol (Typic Acrustox) the sulfentrazone had little mobility, staying on the top 7,5cm, independently the rainfall.
INFLUÊNCIA DO MOMENTO DA CHUVA NA EFICÁCIA DO HERBICIDA GLIFOSATE, EM DIFERENTES CONCENTRAÇÕES, NO INVERNO E NO VERÃO
Two field assays were carried out aiming to evaluate the rain effects on the glyphosate herbicide activity, applied at different concentrations, under two growing seasons (winter and summer). The experiments were conducted at the FCAV / UNESP Experimental Station, during 2000/01. The winter experiment was installed from June to August of 2000 and the summer one was installed from January to March of 2001. The treatments were glyphosate (0,5; 1,0; 2,0 e 4,0%), used as check treatment. In the field, all the trials were set up in the randomized block experimental design, with four replications. The experimental plots was 3.0 m wide x 3.5 m long in the winter assays. In the summer one, the plots' size was 3.0 m x 4.0 m. The treatments were arranged in factorial designs 5 x 4 factors, with five periods between the herbicide spraying and the rain incidence and four concentrations. The herbicide treatments were applied through a back spraying, with six nozzles DG 11002 spaced by 0.5 m, at 30 p.s.i. constant pressions. The artificial rain was provided by a top irrigation system raining 18 - 19 mm during one hour. The artificial rain reduced the glyphosate action, mainly in the shorter periods. Raising the glyphosate concentration to 2.0% supressed the problems promoted by the rain, one hour after sprayings, under winter conditions. Similar results were observed raising the glyphosate concentration to 1.0%, under summer conditions.
EFFECT OF THE DIFFERENT GLYPHOSATE FORMULATIONS ON THE MANAGEMENT OF WEEDS IN COFFEE TREE CROP ABSTRACT
An study was carried out in a commercial one-year-old coffee crop following undercutting, aiming to evaluate the efficiency of different glyphosate salts, that is, potassic, isopropylamine and diamonium in managing weeds in coffee tree crop. The treatments consisted of 10 different managements corresponding to three sequential applications of herbicides, that could be performed with or without the same products. The control efficiency of the weed species were verified at 15, 30, 41, 58, 75, 84, 116 and 140 days after beginning the management (DAM). The management with sequential application of 720 g.ha-1 ac.eq. of potassic salt glyphosate and diamonium salt glyphosate, as well as the management with diuron and paraquat (150 + 300 g.ha-1 a.i., respectively, with added Agral 0.1% v/v) at the third application or at the second and third applications, with the second application performed at 41 days after the first application, and the third one at 54 days after the second application, were all efficient in controlling Brachiaria plantaginea and Bidens pilosa, but inefficient in controlling Euphorbia heterophylla and Commelina diffusa. The management with 720 g.ha-1 ac.eq. of isopropylamine salt glyphosate at the first application, and latter at the second and third ones with the tank mixture of 720 g.ha-1 ac.eq. of isopropylamine salt glyphosate + 30 g.ha-1 a.i. of carfentrazone-ethyl, showed to be effective in controlling Brachiaria plantaginea and Bidens pilosa from 7 to 140 DAM and the Commelina diffusa from 58 to 140 DAM. However, Euphorbia heterophylla were moderately controlled over this period.
RAINFALL EFFECTS ON THE EFFECTIVENESS OF THE DIFFERENT GLYPHOSATE FORMULATIONS IN CONTROLLING Bidens pilosa
This study aimed at evaluating the effects from increasing doses of different glyphosate salts - ammonium (Roundup WG), isopropylamine (Roundup Transorb) and potassic salt (Zapp Qi) - on Bidens pilosa plants under controlled conditions, when they were subjected to a 20-mm rainfall over 30 minutes, at intervals of 1, 2, 4, 6, 12 and 24 hours after application of these products. The efficiency of the glyphosate salts in controlling B. pilosa were affected when the rainfall occurred after their application. The reduction in control was higher as the interval without rainfall after these product applications was diminished. The visual control of B. pilosa was similar from 7 to 28 days after application (DAA) for all these products, and it did not differ as to reduction of the accumulated dry matter in relation to the control without herbicide. The herbicide doses differed in controlling this species, and the most efficient control was obtained with the highest doses. The isopropylamine salt showed a better control upon this species at the shorter intervals without rainfall after its application. (1 and 2 hours), showing to be superior to the other salts. In those intervals without rainfall and longer than two hours, however, the ammonium salt was superior as to the visual control of this species. The potassic salt provided a lower control than the other salts over the periods without rainfall shorter than 12 hours, but showed to be superior to the isopropylamine salt at those intervals without rainfall and longer than 12 hours. Although presenting an excellent control upon the species in visual evaluations, the ammonium salt provided a lower reduction in dry matter than the other salts. The isopropylamine salt provided a higher reduction in dry matter of B. pilosa than the other treatments.
EVALUATION OF SELECTIVITY AND EFFICACY OF FORMULATION MIXTURES OF BENTAZON AND ACIFLUORFEN APPLIED TO SOYBEANS
A trial was carried out to test the efficacy and selectivity of different formulations and doses of bentazon with acifluorfen, applied in post emergence of soybean (cv. Doko). The following treatments were tested in a sandy Latosoil, in Prudente de Morais, Brazil: bentazon+acifluorfen (480+204 g/ha and 600+255 g/ha) with or without mineral oil (0,25% v/v); bentazon+acifluorfen (480+168 g/ha and 600+210 g/ha) with or without mineral oil (0,25%v/v); and bentazon +acifluorfen 600+160 g/ha and weeded and no weeding checks. Independently of the doses and formulations (with or without mineral oil) all chemicals provided efficient control of Amaranthus hybridus, Galinsoga parviflora and Solanum americanum. Significant differences were not observed among the productivities for the several chemical treatments, but reduced the interference of weeds caused an average decrease in yield of 1445 kg/ha in relation to the weed check. These was no difference between treatments concerning plant density, plant height, height of first pod and weight of 100 seeds. All tested treatments were selective for the soybean.
EFICACY AND SELECTIVITY OF FORMULATED MIXTURES OF ATRAZINE/ DIMETHENAMID-P AND ATRAZINE/DIMETHAMID IN THE WEED CONTROL IN CORN
A trial was carried out to test the efficacy and selective of formulation and doses of atrazine/ dimethenamid-p andatrazine/dimethenamid, in pre-emergence on corn (cv. Primaiz BR 3101). The following treatments were tested in a sandy Red Yellow Latossol soil, in Uberaba, Brazil: atrazine 396 g/L/dimethenamid-p 204 g/L (1800, 2100, 2400 and 2700 g/ha) and atrazine 320 g/L/ dimethenamid 289 g/L (2100, 2400, 2700 and 3000 g/ha), s-metolachlor 960 g/L (2880 g/ha) and hand weeding and weeded. The mixture of atrazine/dimethenamid-p and atrazine/ dimethenamid, independently of the rates provided good control of the weeds Bidens pilosa, Portulaca oleracea, Commelina benghalensis and Digitaria horizontalis. No significant differences was observed in the productivities of the chemical treatments, but weeded treatment reduced 72% of the crop yield in relation to the hand weeding treatment. These was no difference among treatments concerning to the crops density, cobs numbers and first cob height and seed weight. The harvest index for mechanical harvesting in the chemical treatments was excellent. All the tested treatments were selective to corn.
The tolerance in soy plants, using the herbicides imazaquim, diclosulam and sulfentrazone
With the objective to evaluate the genotypes of soybeans when using the herbicides Imazaquim, diclosulam and sulfentrazone, this research was conducted at “ Fazenda Tres Irmãos “ pertaining to Jatai county, Goias, during the growing season 2000/2001. After planting the genotypes of soybeans in arenaceous soil, containing 17,19% clay, 44 g/kg of organic material and CTC of 12,49 cmol/dm³, the herbicides, imazaquin, diclosulan, and sulfentrazone, were sprayed pre-emergence in the following doses – 140 and 280g. /ha, 35 and 70g/ha, 600 and 1200g/ha, respectively. After 15 and 30 days, after the spraying (DAT) of the herbicides, the plant intoxication of the herbicides was evaluated in the genotypes of soybeans. By random of harvest, the height of the plants and insertion of the first string bean, number of plants and yield were evaluated. The conclusions were: a) The herbicides imazaquin, diclosulam and sulfentrazone caused plant intoxication in the genotypes of soybeans planted in arenaceous texture. Especially when the double, of the recommended dose was used. b) In the doses tested, the herbicides didn’t significantly affect the plant density, nor the height of the insertion of the first string bean in the genotypes of soybeans. c) Sulfentrazone in dose equivalent to 1200g/ha, reduced significantly the height in the genotypes-GOBR 93-1283, EMGOPA-316 and CRIXÁS, compared with the untreated area. Diclosulan, in dose equivalent to 35g/ha caused reduction in height in the genotypes – GOIÂNIA, GOBR 93-122243 RNC and LUZIÂNIA. GOBR 93-122243 RCN, GOIÂNIA, LUZIÂNIA, EMGOPA 316, SANTA CRUZ and CRIXÁS already had their heights affected compared with the untreated area, in a dose equivalent to 70g/ha of diclosulan. Imazaquin, in a dose equivalent to 280g/ha, affected significantly the height in the plants of the sort, CRIXAS. d) Diclosulan in dose equivalent to 70g/ha caused significantly reductions in yield in the genotypes – GOBR93-1283, GOBR93-12243 RCN, EMGOPA-302, SANTA CRUZ and EMGOPA-313. Sulfentrazone, used in a dose equivalent to 1200g/ha, caused a reduction in the productivity in the genotypes – GOBR 93-1283, GOBR 93-122243 RNC, GOIATUBA, LUZIÂNIA, EMGOPA-316, EMGOPA-314, SAMBAÍBA, EMGOPA-302, EMGOPA-313 and CRIXÁS. The genotypes – GOIATUBA, EMGOPA-316 and SANTA CRUZ had already showed reductions in productivity, when using imazaquin in a dose equivalent to 280g/ha; e) The genotypes of soybeans showed different tolerance with the herbicides sulfentrazone, diclosulan and imazaquin, specially when there was used a doublet dose.
ALTERNATIVES OF MANEGMENT TO THE POPULATIONS OF Bidens pilosa AND Bidens subaltenans RESISTANTTO THE ALS INHIBITORS HERBICIDES
Resistant populations of Bidens pilosa and Bidens subalternans to the ALS inhibitors herbicides become more frequent at the soybeans fields from middle-west, that is due the intensive use of ALS herbicides, aimed to obtain data that can contribute on the choose of the best alternative of control for those populations. A trial in a green-house, in Piracicaba, SP, to test many herbicides as an possible alternatives of management of those resistant weeds. Initially we used two populations of Bidens pilosa and two populations of Bidens subalternans, one of these was resistant and the other was susceptible to each species. The herbicides treatments were sprayed when the plants showed up 2 to 4 leaves, chlorimuron (17,5 g.i.a.ha-1); imazethapyr (100 g.i.a.ha-1); chlorimuron + lactofen (10+96 g.i.a.ha-1); clomazone (800 g.i.a.ha-1 ); sulfentrazone (500 g.i.a.ha-1 ); glyphosate (600 g.i.a.ha-1); flumicorac (30+30 g.i.a.ha-1); flumicorac + bentazon (40+480 g.i.a.ha-1); bentazon (720 g.i.a.ha-1 ); fomesafen (250 g.i.a.ha-1 ); acifluorfen + bentazon (204+480 g.i.a.ha-1 ); lactofen (150 g.i.a.ha-1); metribuzin (480 g.i.a.ha-1); diclosulam + clomazone (30,24+800 g.i.a.ha-1 ); cloramsulan + lactofen (30,24+150 g.i.a.ha-1); lactofen (72+72 g.i.a.ha-1); lactofen (144 g.i.a.ha-1); nicosulfuron (50 g.i.a.ha-1 ). We analyzed the percentage of control at 7, 14, 21 and 28 days after the application (DAA) and dry weight at 28 DAA. Applied the test F over the variance analyses followed by tukey test at 5%. The herbicides chlorimuron, imazethapyr and nicosulfuron showed up poor control to all resistant populations, being more inefficient on Bidens subalternans than Bidens pilosa. The other herbicides treatments had a very good efficacy to all populations.
THE USE OF A MECHANISTICMODEL TO PREDICT THE EMERGENCE OF Echinochloa crus-galli in rice
The control efficient of the weeds is one of the essential factors to obtain high rice yields, primarily in areas moistened fields, that generally represent higher number of species, probably due to heterogeneous of physical characteristics and chemicals of the soil and moisture contents in the different areas. For the development of these control systems of the unwanted species, it is necessary to anticipate the stage of emergence of weed plants in relation of emergence of the crop. These models where conducted using parameters(cardinal temperature) for the model that were determined by statistic process of linear regression. Using the regression model between the average of elongated function of temperature, determines the base temperature (6,6 and 4,0 °C), preferential (21,7 and 23,6 °C) and maximum (49,0 and 58,8 °C) for the elongation of radicle and hypocotil, respectively. The observed values and calculation for the process of emergence of rice (Echinochloa crus-galli) in different temperatures indicate that the model can establish in an efficient mechanism to predict the desired specie emergence under environmental conditions.