Metabolic Fate of Foliarly Applied [14C]Thiabendazole in Three Growing Plants: Wheat, Soybeans, and Sugar Beets

Abstract

Following foliar application of [14C]thiabendazole to growing wheat, soybean, and sugar beet plants, samples were taken 2 h post-treatment, at immature stages, and at normal harvest. Significant levels of [14C]thiabendazole residues were found in straw and immature leaves (∼10−22 ppm), but residues were far lower in wheat grain, soybean seeds, and sugar beet roots (∼0.12−0.88 ppm), demonstrating very limited translocation of thiabendazole-derived residues. Thiabendazole was the major component (≥91%) of the total residues in early foliage. Samples harvested at later growth stages contained increased levels of polar (aqueous-soluble) and nonextractable residues and diminished levels of organic-extractable residues. Most of the extractable radioactivity consisted of thiabendazole. The major transformation product of thiabendazole found was benzimidazole, present mainly in conjugated form. Fractionation of nonextractable residues in wheat straw demonstrated some incorporation into tissue components. Keywords...