Rice (Oryza sativa) Response and Annual Grass Control with Graminicides

Abstract

Field studies were conducted to evaluate rice injury and control of propanil-resistant and -susceptible (natural infestation) barnyardgrass, broadleaf signalgrass, and Amazon sprangletop with BAS 625, cyhalofop, and fenoxaprop plus the safener isoxadifen in rice. BAS 625 at 100 g ai/ha applied to two- to three-leaf rice resulted in 19 to 72% injury in three of four experiments. Fenoxaprop plus isoxadifen at 90 + 98 g ai/ha injured rice 11 to 31%, and cyhalofop at 280 g ai/ha consistently resulted in minimal rice injury. The most effective control (84 to 99%) of propanil-resistant and propanil-susceptible barnyardgrass across all experiments was achieved with sequential applications of the BAS 625 at 75 and 100 g ai/ha, cyhalofop at 210 and 280 g ai/ha, and fenoxaprop plus isoxadifen at 68 + 74 and 90 + 98 g ai/ha. When the graminicides were applied to four- to six-leaf rice (one tiller), propanil-resistant and propanil-susceptible barnyardgrass control was generally very poor. Fenoxaprop plus isoxadifen controlled broadleaf signalgrass 91 to 100%, even when applied once to four- to six-leaf rice. BAS 625 at 75 and 100 g ai/ha and cyhalofop at 210 and 280 g ai/ha applied sequentially provided consistent broadleaf signalgrass control (≥98%). Amazon sprangletop control was good (85 to 99%) with fenoxaprop plus isoxadifen at 45 + 49, 68 + 74, and 90 + 98 g ai/ha (applied in a single application or sequentially), BAS 625 at 100 g ai/ha applied to two- to three-leaf and four- to six-leaf rice or 50, 75, and 100 g ai/ha applied sequentially, and cyhalofop at 140, 210, and 280 g ai/ha applied to two- to three-leaf rice or sequentially.