EFFECT OF GLYPHOSATE ON DIFFERENT DENSITIES OF WATER HYACINTH

Water hyacinth is a problem in rivers and reservoirs in Mexico and appropiate control methods need to be evaluated. The phytotoxic effects of the herbicide glyphosate were determined on water hyacinth in the reservoir Endho, State of Hidalgo, Mexico. Duplicate 1m2 areas initially containing 10, 20, 30 and 40 kg/m2 densities of water hyacinth were randomly established. After a 2 week acclimatization period, two doses of glyphosate (Rodeo2 at 5 1/ha and 7 1/ha) were applied to the plots and plots were evaluated at 9, 19, 33, 51, 72 and 94 days after treatment. Glyphosate at 5 1/ha (2.38 kg/ha acid) effectively controlled densities of 10 and 20 kg/m2 in 51 days. At higher plant densities (30 and 40 kg/m2), a second application of glyphosate at day 51 of 2 1/ha (0.95 kg/ha) was necessary to achieve plant control. The response of the plants indicated that a second application 20 to 30 days after the first would provide good results in high density areas.