Influence of Herbicide Safeners on Creeping Bentgrass (Agrostis stolonifera) Tolerance to Herbicides

Glasshouse research was conducted to investigate the efficacy of herbicide safeners for improving creeping bentgrass (CBG) tolerance to various herbicides. CBG injury from amicarbazone (150 g ha(-1)), bispyribac-sodium (110 g ha(-1)), fenoxaprop-p-ethyl (35 g ha(-1)), imazapic (45 g ha(-1)), quinclorac (1,050 g ha(-1)), or topramezone (37 g ha(-1)) applied in combination with the herbicide safeners naphthalic anhydride or isoxadifen-ethyl was evaluated. These safeners reduced CBG injury from topramezone only. Topramezone was then applied in combination with naphthalic anhydride, isoxadifen-ethyl, cloquintocet-mexyl (cloquintocet), fenchlorazole-ethyl, mefenpyr-diethyl, and benoxacor. These experiments determined that CBG injury was lowest from topramezone in combination with cloquintocet. Additional experiments evaluated topramezone (37 g ha(-1)) with several rates of cloquintocet and determined that applications at >= 28 g ha(-1) reduced CBG injury similarly. Cloquintocet (28 g ha(-1)) increased topramezone I-50 values against CBG, but not large crabgrass or goosegrass. The cytochrome P450 (cP450) inhibitor malathion (1000 g ha(-1)) reduced topramezone I-50 values against CBG in one experimental run. Topramezone-cloquintocet combinations warrant further research in field settings.