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Distribution and Metabolic Fate of the Fungicide Benomyl in Dwarf Pea. Malcolm R. Siegel, Associate Professor, Department of Plant Pathology, University of Kentucky, Lexington 40506; Anthony J. Zabbia, Jr., Research Associate, Department of Plant Pathology, University of Kentucky, Lexington 40506. Phytopathology 62:630-634. Accepted for publication 12 January 1972. DOI: 10.1094/Phyto-62-630.

Dwarf pea plants growing in nutrient solutions were root-treated with 14C benomyl for 4 days, then harvested at various intervals. No 14C benomyl was recovered from plants at any time. A fungitoxic derivative, 14C methyl 2-benzimidazolecarbamate (MBC), was present in large quantities in organic solvent extracts from treated plants. At senescence (52 days after treatment), 78% of the label was present in MBC, 5% in water-soluble metabolites, and 14% bound to the plant residue. Treatment of residue with hot NaOH released 50% of the bound label, a portion of which was present in 2-aminobenzimidazole. The labeled products were translocated rapidly from the roots to foliage of the plant. Fifty-two days after treatment, 92% of the label was in nonroot portions, concentrated primarily in the foliage which was present during the treatment period. Even when plant roots were continuously exposed to the labeled fungicide, the seeds accumulated only small amounts of radioactivity. The data suggest that long-term chemotherapeutic effects of MBC will be dependent on the mode of application, distribution, and concentration of the fungicide in plants.