Comparison of Herbicides for Control of Diclofop-Resistant Italian Ryegrass in Wheat

Diclofop-resistant Italian ryegrass ( Lolium perenne L. ssp. Multiflorum (Lam.) Husnot) is a dominant weed problem in non-irrigated winter wheat ( Triticum aestivum L.) in mid-south USA. Field studies were conducted from 2001 to 2007 to evaluate the efficacy of herbicides for diclofop-resistant ryegrass control and effect on wheat yield. In 2001 through 2004, chlorsulfuron/metsulfuron at 0.026 kg ha −1 preemergence (PRE) followed by (fb) mesosulfuron at 0.048 kg ha −1 at 4-leaf to 2-tiller ryegrass provided 89% control of diclofop-resistant Italian ryegrass, resulting in the highest wheat yield (3201 kg ha −1 ). Flufenacet/metribuzin at 0.476 kg ha −1 applied at 1- to 2-leaf wheat had equivalent Italian ryegrass control (87%), but lesser yield (3013 kg ha −1 ). In 2005–2006, best treatments for Italian ryegrass control were chlorsulfuron/metsulfuron, 0.013 kg ha −1 PRE fb mesosulfuron 0.015 kg ha −1 at 3- to 4-leaf ryegrass (92%); metribuzin, 0.280 kg ha −1 at 2- to 3- leaf wheat fb metribuzin at 2- to 3-tiller ryegrass (94%); chlorsulfuron/metsulfuron (0.026 kg ha −1 ) (89%); and flufenacet/metribuzin at 1- to 2-leaf wheat (89%). Chlorsulfuron/metsulfuron fb mesosulfuron provided higher yield (3515 kg ha −1 ) than all other treatments, except metribuzin fb metribuzin.