The addition of adjuvants on glyphosate enhances the control of aquatic plant Myriophyllum aquaticum (Vell.)

Background: Knowledge about the action of glyphosate alone and associated with adjuvants in the effectiveness to control aquatic plants is important in the decision-making on its use. Objective: This study aimed to evaluate the effectiveness of glyphosate and five adjuvants in the control of Myriophyllum aquaticum. Methods: Glyphosate (Rodeo (R)) at doses of 1.5, 3.5, 5.5, and 7.5 L ha-1 was sprayed alone and associated with Aterbane (R) BR, Veget'oil (R), Dash (R) HC, Assist (R), and Agral (R) (0.5% v v-1), in addition to the control, with a spray solution volume of 200 L ha-1. The effectiveness of control was evaluated using the scores of a visual scale at 3, 7, 15, 21, 30, 45, and 60 days after application (DAA), regrowth, and dry matter accumulation at 60 DAA. Results: The best effectiveness of control of the glyphosate alone was 85% at the dose of 7.5 L ha(-1), increasing to 100% when associated with Aterbane (R) and Veget'oil (R). The control reached 100% for all glyphosate doses associated with Dash (R). Moreover, glyphosate at the dose of 7.5 L ha(-1) associated with Assist (R) provided a 98% control, while glyphosate doses of 3.5, 5.5, and 7.5 L ha(-1) associated with Agral (R) provided a 100% control. Glyphosate at doses of 5.5 and 7.5 L ha(-1) associated with Dash (R) and Agral (R) was more effective in reducing the regrowth and dry biomass (100%). Thus, glyphosate + Dash (R) and Agral (R) promoted the highest control (above 95%), the lowest regrowth, and the highest reduction in the dry biomass of M. aquaticum. Conclusions: The addition of Aterbane (R) BR, Dash (R), and Agral (R) to glyphosate improved the effectiveness of control of M. aquaticum and contributed to reducing the applied herbicide dose.