This study aimed to evaluate the efficacy of the herbicide diquat in controlling Eichhornia crassipes and Brachiaria subquadripara plants under reservoir conditions. The experimental plots were 650 m², delimited and positioned on the shores of the Salto Grande Reservoir in Americana-SP, Brazil, using fishing nets. The treatments consisted of herbicide diquat, applied as the REWARD commercial formulation at 960 g a.i. ha-1 (two applications at 480 g, at an interval of 15 days), 960 g a.i. ha-1 (single application), 1.920 g a.i. ha-1 (two applications at 960 g, at an interval of 15 days) and a control without herbicide application. The concentrations of diquat in water were monitored before herbicide application and 1, 2, 4, 7, 14 and 28 days after application (DAA), in the experimental area and downstream and upstream. Diquat efficiency was evaluated through visual assessments of control at 1, 2, 4, 7, 14, 21 and 28 DAA of herbicide application and two days after the second application. Diquat showed excellent control of E. crassipes, regardless of the dose tested and type of management, with its effect on B. subquadripara plants being temporary.
aquatic weed; herbicide; aquatic plant; weed; tanner-grass
