Abstract

Three experiments were carried out in order to evaluate the effect of the herbicide clomazone, alone and mixed with propanil and 2,4-D on weed control and toxicity to rice cv. Milagro Filipino, growing under upland conditions. All the experiments were established in Los Naranjos, a rice-growing area located in the Municipality of Tres Valles, in the state of Veracruz. The dominant weed species in the experimental plots were Cyperus iria, Echinochloa colona, Cyperus rotundus, Scleria setuloso-ciliata and Malachra fasciata. Clomazone applied preemergent, efficiently controlled E. colona at 0,72 and 0,96 kg a. i./ha, but its effect was partial and temporary on S. setuloso-ciliata and it had no effect on C. iria and C. rotundus. Mixture of clomazone + propanil + 2,4-D efficiently controlled E. colona and C. iria from 0.60 + 1.44 + 0.24 kg a. i./ha. It also had a good initial control of C. rotundus, but its effect was completely lost between 45 and 60 days after the application and its effect on S. setuloso-ciliata was influenced by the soil moisture: the higher the moisture the better this weed was controlled and viceversa. Rice grain yields obtained in plots where clomazone, alone or mixed with propanil and 2,4-D was applied were statistically similar to those obtained in plots where the weed control regional treatment was applied.