Efficacy and selectivity of imidazolinone herbicides applied in flooded rice

Abstract

This study aimed to evaluate the control of red rice and the selectivity to commercial mutant rice varieties under application of imidazolinone herbicides. The experiment was installed in completely randomized blocks design, under factorial scheme 4x4, with four replications. Factor A was composed by the herbicides and Factor B by doses of these herbicides. The herbicides and doses were: imazethapyr + imazapic [(0.00; 37.50 + 12.50; 75.00 + 25.00 and 150.0+50.00 g ha^-1) + Dash 0.5 v v^-1], imazapyr + imazapic [(0.00; 36.75 + 12.25; 73.50 + 24.50 and 147.00 + 49.00 g ha^-1) + Dash 0.5 v v^-1], imazethapyr (0.00; 75.00; 150.00 and 300.00 g ha^-1) and imazapic (0.00; 12.25; 24.50 and 49.00 g ha^-1 + Dash 0.5 v v^-1). The control of red rice was evaluated 14 and 28 days after treatment (DAT), as well as at the pre-harvest; toxicity to commercial rice was evaluated 7, 14 and 21 DAT. Commercially available mixtures of imazapic + imazapyr, at the recommended dose (73.5 + 24.5 g ha^-1), and imazethapyr + imazapic at twice the dose (150.00 + 50.00 g ha^-1) were efficient in controlling red rice. These same mixtures were also selective to the rice variety Puitá Inta-CL, independently of dose. Herbicides not registered for control of red rice, imazethapyr and imazapic, were not efficient in controlling red rice.