In 2002, two experiments were

carried out in the municipality of Tres Valles, Ver., Mexico, in

order to evaluate the effectiveness of cyhalofop-butyl on the

annual grass weed control in rain-fed rice cv Milagro

Filipino. A randomized complete block design with seven

treatments and four replications was utilized for both

experiments. Cyhalofop-butyl was evaluated at 180, 225,

270, 315 y 360 g/ha, propanil at 4320 g/ha and a weedy check

were also included. The treatments were applied when the

rice plants had a height of 25 cm. Annual grass weeds present

in the experiments, were junglerice and Southern crabgrass

[Digitaria ciliaris (Retz.) Koeler]. Grass weed control and

toxicity to rice were evaluated at 15, 30 and 45 days after

application. The highest junglerice and Southern crabgrass

controls were obtained when cyhalofop-butyl was applied at

315 and 360 g/ha. The different dosages of this herbicide, did

not cause any toxicity to rice. The effect of propanil on weeds

was similar to that of cyhalofop-butyl at 360 g/ha during the

first 15 days after application.

Keywords: grass weeds, rainfed rice, cyhalofop-butyl, chemical control, Echinochloa colona, Digitaria ciliaris.