DROUGHT STRESS REDUCES FLUAZIFOP-P ACTIVITY ON GREEN FOXTAIL (SETARIA-VIRIDIS)

Although drought-stressing green foxtail before and up to 1 d after herbicide application did not reduce control with fluazifop-P in growth chamber trials, extending the drought stress for 2 to 4 d after herbicide application reduced control of green foxtail with fluazifop-P by 40 and 57%, respectively. Absorption and translocation of C-14-fluazifop-P 1, 4, and 10 d after herbicide application were similar between nonstressed and drought-stressed plants. Drought-stressed green foxtail converted slightly more of the parent acid of fluazifop-P to polar conjugates 4 d after herbicide application than did nonstressed plants, but these differences in metabolism were probably not adequate to explain large differences in efficacy. Nomenclature: Fluazifop-P, (R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]-oxy]phenoxy]propanoic acid; green foxtail, Setaris viridia (L.) Beauv. # SETVI3.