Nicosulfuron provides POST weed control in corn, pastures, and grassy roadsides, and has potential for use in fine turfgrass. The objective of this research was to evaluate tolerance, absorption, translocation, and metabolism of nicosulfuron in annual bluegrass and four turfgrass species. In greenhouse experiments, relative tolerance of grasses to nicosulfuron (35, 70, or 140 g ai ha⁻¹) from high to low was bermudagrass  =  zoysiagrass > tall fescue > creeping bentgrass > annual bluegrass. In laboratory experiments, grasses had similar foliar and root absorption of ¹⁴C-nicosulfuon. Annual bluegrass and creeping bentgrass averaged 80% greater radioactivity per unit dry mass in shoots than bermudagrass following root uptake of ¹⁴C-nicosulfuron, but other species were similar to these grasses. At 72 h after treatment (HAT), annual bluegrass metabolized 36% of absorbed ¹⁴C-nicosulfuron, which was less than bermudagrass, tall fescue, and zoysiagrass that metabolized 47 to 58%. Creeping bentgrass metabolism of nicosulfuron was similar to annual bluegrass. Tall fescue had similar levels of metabolism to bermudagrass and zoysiagrass, averaging 67%, at 168 HAT but produced fewer metabolites. Overall, turfgrass tolerance to nicosulfuron is associated with relative herbicide concentrations in shoots and differential species metabolism.

Nomenclature: Annual bluegrass (Poa annua L.); bermudagrass (Cynodon dactylon × transvaalensis Burtt-Davy) ‘Princess 77’; creeping bentgrass (Agrostis stolonifera L.) ‘Penn A-4’; tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] ‘Titan’; zoysiagrass (Zoysia japonica Steud.) ‘Zenith’.