Alternative herbicides for controlling Bidens pilosa and Euphorbia heterophylla resistant to ALS inhibitor in cotton crop

Abstract

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.