Herbicides for rooted aquatic macrophytes

The aim of this study was to evaluate the effectiveness of glyphosate, 2,4-D, and diquat to control the aquatic macrophytes Brachiaria subquadripara, Hedychium coronarium, and Myriophyllum aquaticum under greenhouse conditions. The following herbicides and doses were used: glyphosate at 240, 720, 1,680, 2,640, 3,600, and 4,320 g a.e. ha-1, 2,4-D at 335, 1,005, 1,675, 2,345, and 3,015 g a.e. ha-1, diquat at 100, 200, 300, 400, 500, and 600 g a.i. ha-1, and a control with 10 replications. Sprayings were applied with a CO2-pressurized backpack sprayer at a constant pressure of 172.36 KPa, tips DG 11002, and spray solution consumption of 200 L ha-1. The effectiveness of control was evaluated visually at 3, 7, 15, 21, 30, 45, and 60 days after application (DAA) and dry matter accumulation at 60 DAA. Glyphosate promoted the best effectiveness, with 100% control of B. subquadripara, with no dry matter accumulation from 720 g a.e. ha-1. The herbicide 2,4-D presented the best control for M. aquaticum with 100% control from 1,209 g a.e. ha-1, and for H. coronarium with 99% control from 2.015 g a.e. ha-1, both doses with no dry matter accumulation. The diquat was not effective in controlling the plants of M. aquaticum and B. subquadripara, besides allowing resprouts.