Metabolic Fate of Phenothrin in Plants and Soils

NAMBU Kenji, OHKAWA Hideo, MIYAMOTO Junshi

doi:10.1584/jpestics.5.177

(+)-Trans and (+)-cis isomers of phenothrin [3-phenoxybenzyl (±)-cis, traps-chrysanthemate] labeled with ¹⁴C at the methylene group of the alcohol moiety disappeared rapidly from the treated leaves of bean and rice plants with half-lives of less than one day under greenhouse conditions. On and/or in these plants, both isomers underwent ozonolysis at the isobutenyl double bond to yield ozonides of phenothrin isomers which were rapidly decomposed to the corresponding aldehydes and carboxylic acids. These ester products were further metabolized via cleavage of the ester linkage, hydroxylation at 2′- and 4′-positions of the alcohol moiety, and oxidation of benzyl alcohols to benzoic acids. The resulted alcohols and carboxylic acids were subsequently conjugated with sugars. Bean plant seedlings planted in Kodaira soil, Katano soil and Muko sand treated with 1.0ppm of ¹⁴C-phenothrin isomers took up very little ¹⁴C into shoots, and pods and seeds, whereas roots retained 0.21-3.48ppm of ¹⁴C. No parent compounds were detected in shoots. ¹⁴C-Phenothrin isomers were rapidly decomposed in Kodaira and Katano soils with half-lives of 1 to 2 days under upland conditions. On the other hand, degradation of both isomers was much slower under flooded conditions, and half-lives were 2 to 4 weeks and 1 to 2 months for the (+)-trans and (+)-cis isomers, respectively. Degradation of phenothrin isomers in the soils proceeded via cleavage of the ester linkage, hydroxylation at 4′-position of the alcohol moiety, cleavage of the diphenyl ether linkage and oxidation of benzyl alcohols to benzoic acids. These products were not persistent in the soils under both conditions and the labeled carbon was finally decomposed to ¹⁴CO₂.

Metabolic Fate of Phenothrin in Plants and Soils

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