Absorption, Translocation, and Activity of Fluazifop-Butyl as Influenced by Plant Growth Stage and Environment

Absorption and translocation of14C-fluazifop-butyl {butyl ester of (±)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoate} was compared in susceptible quackgrass [Agropyron repens(L.) Beauv. ♯3AGRRE] and tolerant soybean [Glycine max(L.) Merr.]. Foliar absorption was more rapid in soybeans with 75% of the recovered14C absorbed 6 h after treatment compared to 36% in quackgrass. Translocation of the radiolabel occurred in both soybean and quackgrass with no significant difference between the species. Differential absorption and translocation did not contribute to the selectivity of fluazifop-butyl. Herbicidal activity was lower on quackgrass plants at the five- to six-leaf stage when compared to the two- to three-leaf stage. Greater quackgrass control was observed at 30 than at 20 C. Foliar absorption of14C-fluazifop-butyl was significantly greater at 30 than at 20 C. Translocation of the radiolabel was greater in plants exposed to full light as compared to shade. Moisture stress significantly reduced quackgrass control with fluazifop-butyl.