Utilizing Benzobicyclon to Control Weedy Rice in Imidazoline-Resistant Rice Systems.

An increase in weedy rice (Oryza sativa L.) populations resistant to herbicides has heightened the need for alternative modes of action. Benzobicyclon is a 4-hydroxyphenylpyruvate dioxygenase inhibitor, the first of its kind labeled in rice. Benzobicyclon has shown substantial control of various monocot and broadleaf species, and this study evaluated the effectiveness of benzobicyclon as a weed control partner in imidazoline-resistant rice weed control systems. The study was organized as a split-plot in a randomized complete block design. The whole-plot factor was the presence or absence of benzobicyclon at 12.6 fl oz/ac applied post-flood, and the subplot factor was herbicide treatments containing imazamox and imazethapyr applied at either 2- to 3-leaf (early postemergence) or 5-to 6-leaf (preflood). Weedy rice and barnyardgrass (Echinochloa crus-galli) visual control, visual rice injury, and stunting evaluations were taken five times up to six weeks after post-flood treatment (WAFT). Rough rice yield was taken at crop maturity. Visual injury was minimal, never exceeding 12%, and there was no more than 8% injury due to bleaching. Improved visual weedy rice control was observed with the addition of benzobicyclon to 1) no additional herbicide, 2) imazamox at 5 fl oz/ac applied at 5- to 6-leaf rice, and 3) imazamox at 5 fl oz/ac applied post-flood. Rice yields were similar among all treatments. The findings from this research show that adding benzobicyclon to existing weed control programs in imidazoline-resistant rice can improve weedy rice control and aid in lowering weedy rice seedbank density. [ABSTRACT FROM AUTHOR]