The Response of Creeping Bentgrass, Roughstalk Bluegrass and Perennial Ryegrass to Pinoxaden in Combination with Herbicide Safeners.

The herbicide pinoxaden is a phenylpyrazoline inhibitor of acetyl-CoA carboxylase. Research was conducted to determine the effects of pinoxaden (90 g ha^-1) alone and in combination with herbicide safeners on creeping bentgrass (Agrostis stolonifera) injury, as well as perennial ryegrass (Lolium perenne) and roughstalk bluegrass (Poa trivialis) control. Preliminary glasshouse research determined that the herbicide safeners cloquintocet-mexyl, fenchlorazole-ethyl, and mefenpyr-diethyl reduced creeping bentgrass injury from pinoxaden; creeping bentgrass injury from pinoxaden (90 g ha^-1) decreased as herbicide safener rates increased. Research was conducted in a glasshouse at the University of Tennessee to evaluate the effects of cloquintocet-mexyl, fenchlorazole-ethyl, and mefenpyr-diethyl on pinoxaden injury to creeping bentgrass and efficacy against perennial ryegrass and roughstalk bluegrass. Herbicide safeners were applied at 68 or 450 g ha^-1 to evaluate their effects on pinoxaden (90 g ha^-1). While safeners reduced roughstalk bluegrass control these compounds also reduced creeping bentgrass injury from 25% to ≤ 5%. Safeners did not affect perennial ryegrass control. Cloquintocet-mexyl and mefenpyr-diethyl generally reduced creeping bentgrass injury from pinoxaden more than fenchlorazole-ethyl. Field experiments should evaluate pinoxaden in combination with cloquintocet-mexyl and mefenpyr-diethyl to optimize safener:herbicide ratios in different climates and seasons.