This work aimed to evaluate the interspecific competitiveness of Echinochloa spp. biotypes resistant or susceptible to the herbicide quinclorac. The trial was installed under greenhouse conditions, with the biotypes resistant (ITJ-13) and susceptible (ITJ-17) to quinclorac under competition with the rice plants. The treatments consisted of maintaining one rice plant at the center of the experimental unit, surrounded by 0, 1, 2, 3, 4 or 5 Echinochloa plants, according to the treatment. The trial was arranged in a completely randomized blocks design and factorial scheme 2 x 6, with four replications. Forty days after emergence, fresh dry weights and water content of the shoots were evaluated. There was a significant effect for all the variables when the rice was grown in the presence of R or S. Echinochloa spp. This effect was additive in the proportion of one plant m-2. However, the competitive capacity of R and S to quinclorac Echinochloa spp biotypes against the rice plants showed similar behavior when plant density per area varied.
interference; resistance; chemical control; environmental resources
