Smooth Crabgrass and Goosegrass Control with Metamifop in Creeping Bentgrass

Abstract

Smooth crabgrass (Digitaria ischaemum) and goosegrass (Eleusine indica) are problematic weeds in creeping bentgrass (Agrostis stolonifera) because of limited herbicide options for postemergence (POST) control and turfgrass injury potential. Metamifop is a herbicide currently being considered for release to markets in the United States but information is lacking on the most effective rates and application timings for smooth crabgrass and goosegrass control in creeping bentgrass. Field trials were conducted in Auburn, AL in 2009 and 2013 to evaluate metamifop rates (200 to 800 g·ha−1) and single or sequential application timings compared with fenoxaprop (51 to 200 g·ha−1) at two different mowing heights. Metamifop applied twice and three times sequentially at 200 g·ha−1 provided the greatest smooth crabgrass (>97%) and goosegrass (>90%) control at rough (1½ inch) and green (1/8 inch) mowing heights without unacceptable creeping bentgrass injury at 56 days after initial treatment. All treatments caused <20% visible injury on creeping bentgrass at both mowing heights except the highest rate of metamifop. Smooth crabgrass control at the green mowing height was greater than at the rough mowing height, especially at lower metamifop rates with a single application.