Selective Postemergence Herbicide Control of Torpedograss in Centipedegrass

Torpedograss infestation in centipedegrass has reduced centipedegrass quality in home lawns along the Gulf Coast. This study was conducted to evaluate three selective postemergence herbicides. Field trials were conducted at two sites in Louisiana to evaluate quinclorac, sethoxydim, and clethodim applied once or sequentially every 4 wk for selective torpedograss control in centipedegrass turf. Herbicides were applied to mixed stands of torpedograss/centipedegrass at two locations in Louisiana and evaluated for changes in torpedograss coverage and centipedegrass injury every 2 wk for 16 wk. All herbicides controlled torpedograss more with each sequential application. Sethoxydim and clethodim applied three times reduced torpedograss cover 84 and 87%, respectively, and more than quinclorac 12 wk after initial treatment (WAIT). Increasing clethodim or sethoxydim rates did not improve torpedograss control. Torpedograss regrowth occurred within weeks after final herbicide applications regardless of herbicide. Only multiple clethodim applied at twice manufacturer's labeled rate or quinclorac applications resulted in commercially unacceptable (> 25%) injury to centipedegrass. Multiple sethoxydim or clethodim applications at 0.32 kg ha(-1) or 0.30 kg ha(-1) every 4 wk reduced torpedograss competitiveness in centipedegrass; however, multiple applications for more than 1 yr might be necessary to achieve torpedograss control.