Kentucky Bluegrass and Annual Bluegrass Responses to Ethofumesate

Abstract In a 1983 study, ethofumesate at 1.1, 2.2, and 3.3 kg°ha −1 ; bensulide at kg°ha −1 ; and an untreated control were compared for annual bluegrass [ Poa annua var. annua (L.) Timm] control and injury to ‘Park’ and ‘Touchdown’ Kentucky bluegrass ( Poa pratensis L.). Ethofumesate at 1.1 to 3.3 kg°ha −1 reduced verdure and clipping yields of both cultivars, but gave significant P. annua control. Bensulide at 13.6 kg°ha −1 caused no injury and had unsatisfactory P. annua control. In 1984 ethofumesate was applied to ‘Touchdown’ at 1.1 and 2.2 kg°ha −1 and in repeat treatments of 1.1 + 1.1 kg°ha −1 and 2.2 + 1.1 kg°ha −1 with a 30-day interval between treatments, and was compared to bensulide at 13.6 kg°ha −1 and an untreated control. Ethofumesate caused injury at 7 and 15 days after treatment (DAT), but only the repeat treatments had significant injury at 60 DAT. No injury was detectable at 260 DAT. Excellent annual bluegrass control was obtained at 2.2 kg°ha −1 and 2.2 + 1.1 kg°ha −1 . Good annual bluegrass reduction was noted for the other treatments with exception of bensulide, which only reduced the pest population by 50%. Lateral spread of ‘Touchdown’ increased with ethofumesate treatment (when compared to the untreated control) due to reduced annual bluegrass competition. Chemical names used: (±)-2-ethoxy-2,3-dihydro-3.3-dimethyl-5-benzofuranyl methanesulfonate (ethofumesate); and O , O -bis(l-methylethyl) S -[2[(phenylsufonyl) aminojethyl] phosphorodithioate (bensulide).