STUDIES ON POSTEMERGENCE GRASS HERBICIDES FOR SOYBEANS AND UPTAKE, TRANSLOCATION AND METABOLISM OF FLUAZIFOP-BUTYL IN SEVERAL PLANTS

Field studies evaluating the efficacy of several new chemistry post-emergence grass herbicides indicated high potential of these herbicides for controlling annual grasses in soybeans. Low rates and delayed application time to allow most grasses to germinate, resulted in nearly 100% grass control for all herbicides studied. Soil based residual grass control is possible if application is made at full label rates.;Studies evaluating the influence of fluazifop-butyl on meristematic ATP levels in foxtail millet {Setaria italica (L.) P. Beauv.}, a susceptible plant, and common cocklebur (Xanthium pensylvanicum Wallr.), a non-susceptible plant indicated that a peak in ATP accumulation in millet occurred at about 12 hours after application followed by a significant decline. Common cocklebur reacted similarly except that a peak in ATP was observed at about 3 hours with a rapid decline thereafter. While ATP influences many plant responses, especially protein synthesis, the influence of fluazifop-butyl on the meristematic ATP levels is not considered a mechanism for the mode of action of fluazifop-butyl.;Uptake, translocation and metabolism studies involving ('14)C fluazifop-butyl treatment to foxtail millet and common cocklebur indicated that minimal translocation of herbicide occurred in the foxtail millet, as 3/4 of the applied ('14)C herbicide remained in the treated leaf even after 5 days. Most ('14)C that did translocate appeared to move basipetally in the phloem. Very significant translocation of the herbicide occurred in common cocklebur compared to foxtail millet as concentrations in the treated leaf decreased over time, with subsequent increase in concentration in other plant tissues. Fluazifop-butyl appears to move in the assimilate stream in common cocklebur, but it is also xylem mobile.;In both species, fluazifop-butyl is degraded to fluazifop, the parent acid. ('14)C was exuded by common cocklebur roots more than in foxtail millet and in both species, exuded materials chromatographed as fluazifop.;Separate greenhouse tests studying fluazifop-butyl {((+OR-)) butyl 2-{4-5{{5-(trifluoromethyl)-2-pyridinyl}oxy}phenoxy} propanoate}, indicated that X-77 surfactant resulted in superior grass control compared to crop oil concentrate. Also, no improved grass control was realized under greenhouse conditions between 0.07, 0.14, and 0.28 kg ai/ha but 0.04 kg ai/ha resulted in less control compared to the above three rates.;Differences in selectivity between broadleaf crop and weed species and grass crop and weed species are apparently not due to differences in absorption and probably not due to differences in translocation and subsequent accumulation in certain plant tissues.