Leaf Wash Techniques for Estimation of Foliar Absorption of Herbicides

Three wash techniques, each with 1, 10, or 95% (v/v) ethanol:water were used to measure foliar absorption of 14 C-glyphosate [ N -(phosphonomethyl)glycine], 14 C-3,6-dichloropicolinic acid, and 14 C-chlorsulfuron {2-chloro- N -[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl] benzenesulfonamide} in Tartary buckwheat [ Fagopyrum tataricum (L.) Gaertn. ♯ 3 FAGTA], Canada thistle [ Cirsium arvense (L.) Scop. ♯ CIRAR], and barley ( Hordeum vulgare L. ‘Galt’). For the herbicides and species tested, the most suitable common procedure for determining absorption consisted of a double or triple rinse with or immersion in 10% ethanol. Wiping the treated leaves with cotton balls moistened with the solvent was much less effective. Efficiency of herbicide removal by a given solvent was not related consistently to solubility of the herbicide in the solvent.