Imazethapyr Co-Application Interactions in Imidazolinone-Resistant Rice

Abstract

A study was conducted to evaluate interactions of imazethapyr co-application with propanil, thiobencarb, or a prepackaged mixture of propanil plus thiobencarb. At 7, 14, 21, and 49 d after treatment (DAT), synergism occurred for red rice treated with imazethapyr at 70 g ai ha−1mixed with propanil plus thiobencarb at 1,680 and 3,360 g ai ha−1. A synergistic response was also observed with imazethapyr at 70 g ha−1mixed with propanil at 1,680 g ha−1; however, all other co-applications evaluated resulted in a neutral response with no antagonism observed. At 7 DAT, antagonism was observed for barnyardgrass when treated with imazethapyr at 70 g ha−1mixed with propanil plus thiobencarb at 1,680 g ha−1, propanil at 840 g ha−1, or thiobencarb at 840 and 1,680 g ha−1; however, a synergistic response occurred for barnyardgrass control at 14, 21, and 49 DAT with imazethapyr at 70 g ha−1mixed with propanil plus thiobencarb at 3,360 g ha−1. The synergistic response observed for red rice and barnyardgrass control with a mixture of imazethapyr plus propanil plus thiobencarb can benefit producers by increasing control of red rice and barnyardgrass, and this mixture contains three herbicides with three different modes of action, which can be part of an overall resistance-management strategy in imidazolinone-resistant (IR) rice.