Imazethapyr Absorption and Fate in Leafy Spurge (Euphorbia esula)

Absorption, translocation, root release, and metabolism of imazethapyr by leafy spurge were determined under growth chamber conditions. 14C-imazethapyr was applied to vegetatively propagated leafy spurge plants in a 1% solution of 28% urea ammonium nitrate containing 0.25% by vol nonionic surfactant Plants were harvested 2 and 8 d after herbicide application. Imazethapyr absorption increased from 9% at 2d to 20% at 8d. Acropetal and basipetal translocation out of the treated leaf was observed, with 3.4 to 4.2% of the applied radioactivity accumulating in the root by the end of the 8-d time course. Eight days after herbicide application, radioactivity in dormant and elongated adventitious shoot buds was twofold higher than in root tissue (compared on a dry wt basis). Two days after herbicide application, 93% of the radioactivity remained as intact imazethapyr in the treated leaf, crown, root, and shoot buds. Eight days after application, crown, roots, and adventitious shoot buds had metabolized an average of 61, 36, and 47% of the imazethapyr, respectively, while only 14% was metabolized in the treated leaf. The primary metabolite cochromatographed with 5-hydroxyethyl-imazethapyr standard.