Influence of Adjuvants and Bromoxynil on Absorption of Clethodim

Abstract

The effect of nonionic surfactant, crop oil concentrate, organosilicone surfactant, methylated seed oil, and a blend of organosilicone surfactant and methylated seed oil on absorption of14C-clethodim was evaluated in barnyardgrass (Echinochloa crus-galli). Absorption of14C-label was greatest during the first 40 min after application when14C-clethodim was applied with methylated seed oil or a blend of methylated seed oil and organosilicone surfactant. These adjuvants increased the rate of absorption more than crop oil concentrate, organosilicone surfactant, or nonionic surfactant. Crop oil concentrate was more effective than organosilicone or nonionic surfactant in increasing absorption, with nonionic surfactant being more effective than organosilicone surfactant. These results generally agreed with the order of increasing efficacy of clethodim on barnyardgrass as affected by adjuvants in field experiments. Another study was conducted to determine the effect of bromoxynil on absorption and translocation of14C-clethodim in yellow foxtail (Setaria glauca). Bromoxynil reduced absorption of14C–clethodim 4, 8, and 24 h after application and also reduced the amount of14C-label translocated from the treated leaf. These data suggest that antagonism of clethodim control of yellow foxtail by bromoxynil observed in previous research can be attributed partially to decreased absorption and translocation of clethodim.