Three trials were carried out in Brazil in 1999 to study the effect of herbicides on aquatic weed control in reservoirs. The herbicides and doses used were: diquat at 460, 960 and 1,400 g ha-1; 2.4 D at 1,340 g ha-1; glyphosate at 3,360 g ha-1, imazapyr at 250 g ha-1 and a control. The experiment was arranged in a randomized complete block design with four replications. The plots were constituted by reservoirs with 60 x 60 x 60 cm dimension. The diquat herbicide at all doses showed excellent control of Salvinia molesta, Pistia stratiotes and Eichhornia crassipes. The herbicides 2.4 D and imazapyr did not promote a good control for P. stratiotes while glyphosate showed a very good control. For E. crassipes, 2.4 D and glyphosate showed an efficient control. The herbicides imazapyr, 2.4 D and glyphosate did not show a good control over S. molesta.
weed; aquatic plant; herbicide
