IDENTIFICATION OF SULFOMETURON-RESISTANT ITALIAN RYEGRASS (LOLIUM-MULTIFLORUM) SELECTIONS

Two sulfometuron-resistant biotypes of Italian ryegrass were identifie d from rights-of-way of U.S. Highway 49E in Holmes County, MS, and Sta te Highway 14 in Humphreys County, MS, Sulfometuron at 5.2 g ai/ha app lied PRE or POST reduced shoot fresh weight of these selections 20% or less at 4 wk after treatment. A susceptible 'Gulf' Italian ryegrass w as reduced 52% or more in shoot fresh weight by 0.5 g/ha sulfometuron applied PRE or POST, The biotype from Highway 49E was reduced 47% or l ess in shoot fresh weight by 520 g/ha sulfometuron applied PRE or POST .