TRANSLOCATION AND PERSISTENCE OF TOPICALLY APPLIED DIAZINON AND PHORATE IN BEANS

Diazinon (O,O-diethyl O-(2-isopropyl-6-methyl-4-pyrimidinyl)phosphorothioate) and phorate (O,O-diethyl S-[(ethylthio)methyl] phosphorodithioate) were each applied to one leaf of each of 48 bean (Phaseolus vulgaris L.) plants to trace translocation and persistence within the growing plant. Both insecticides moved readily from the treated leaf to the opposite leaf and upward into the shoot. Residues appeared in the stem, but downward movement into the roots was limited. With diazinon, only the parent compound was recovered; with phorate, the sulfoxide and sulfone metabolites were the major fractions after the 1st day. By 14 days after treatment, total residues of phorate and its metabolites had diminished to 0.02 ppm or less, except in the treated leaf itself; diazinon levels had decreased to 0.02, 0.04, and 0.08 ppm in the untreated leaf, stem, and shoot, respectively.