Translocation and Metabolism of Dicamba in Tartary Buckwheat

Abstract

The herbicide 3,6-dichloro-o-anisic acid (dicamba) is very mobile in Tartary buckwheat (Fagopyrum tataricum(L.) Gaertn.), a susceptible weedy species. After foliar or root application, the compound was translocated rapidly to meristematic tissues at the shoot apex and in leaf axils. Redistribution of dicamba in the shoot, to young tissues, continued for at least 20 days. Metabolism of dicamba occurred very slowly, both in intact plants and in detached leaves, and the only metabolite detected was conjugated with sugars. The nonphytotoxic metabolite was identified by paper and thin-layer chromatography as 5-hydroxy-3,6-dichloro-o-anisic acid. Decarboxylation of dicamba also occurred in the plants but extremely slowly. The rapid entry and translocation of dicamba, its continued mobility in treated plants, and its very low rate of detoxification are major contributing factors to the effectiveness of dicamba for controlling Tartary buckwheat.