Chemical Azolla filicoides L. control.
Post-emergence herbicide control of Azolla filicoides [Azolla filiculoides] was studied in Botucatu, Sao Paulo (Brazil). The herbicides and rates (g/ha) tested were: diquat (Reward) at 940 g/ha; diquat (Reward) at 940 g/ha + Agral; diquat (Reward) at 1400 g/ha; diquat (Reward) at 1400 g/ha + Agral; 2,4D at 1340 g/ha; glyphosate (Rodeo) at 3360 g/ha + 0.5% Aterband; and imazapyr (Arsenal) at 250 g/ha. A. filiculoides plants were distributed in black, plastic pots (28.5×13.5×12.0 cm, with a capacity of nearly 4 litres) covering the whole water surface. Phytotoxicity was evaluated at 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 and 22 days after application (DAA). Diquat-treated plants had the first phytotoxicity symptoms at 2 DAA. Independent of rate used diquat provided overall control of A. filiculoides plants at 12 DAA. Phytotoxicity symptoms began at 4 DAA in glyphosate-treated plants. 2,4-D and imazapyr provided the poorest control.