PRE EMERGENT HERBICIDES FOR VOLUNTEER Acacia mangium CONTROL IN EUCALYPTUS PLANTATIONS IN INDONESIA

Resumo

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.