SELECTIVITY OF ALS INHIBITORS HERBICIDES AT DIFFERENT STAGES OF UPLAND RICE DEVELOPMENT

Abstract

The availability of herbicides registered for upland rice is still limited, increasing the management difficulty level for weeds under this crop system. The objective of this study was to evaluate the effect of the ALS inhibitors herbicides application, at different periods, on upland rice (cv. Cambará). The experimental design was randomized blocks with four replications, in a 5x3 factorial scheme, consisting of the herbicide treatments penoxsulam (36 g ha^-1), bispiribaque-sodium (50 g ha^-1), pirazossulfurom-ethyl (20 g ha^-1), 2,4-D (670 g ha^-1), and a control, and three application periods: 15, 30, and 45 days after emergence (DAE). Plant phytotoxicity, height, and dry biomass were evaluated at 7, 14, and 28 days after application (DAA), and also the number of panicles m^-2, number of grains panicle^-1, and yield. It was observed plant phytotoxicity and height decreasing only when applying bispiribaque-sodium, at 15 and 30 DAE. The plant dry biomass was not affected by herbicide application. The number of grains panicle^-1 decreased only for pirazossulfurom-ethyl, at 45 DAE. Yield decreased with the pirazossulfurom-ethyl and penoxsulam application, at 45 DAE. Generally the best herbicide application period was 30 DAE.