Formamidines and Formanilides as Inhibitors of Permethrin Degradation by Insect Preparations

Abstract

Several formamidines and formanilides were evaluated at concentrations of 1 × 10−3 and 1 × 10−5 M for their ability to inhibit the degradation of permethrin in vitro by oxidase and esterase preparations from adult house flies, Musca domestica (L.), and by pyrethroid esterase from gut preparations of larval cabbage loopers, Trichoplusia ni (Hubner). Formamidines and formanilides inhibited the activity of house fly oxidase and esterase preparations; however, they generally were better inhibitors of oxidase activity than esterase activity. Neither formamidines nor formanilides showed appreciable inhibition of permethrin degradation by cabbage looper pyrethroid esterase at 1 × 10−5 M , but most compounds were active inhibitors at 1 × 10−3 M . Several of these formamidines and formanilides have been shown in other studies to interact synergistically with insecticides and acaricides in insects and mites. Inhibition of pesticide metabolism by these compounds might playa role in the synergistic interaction. Dual action on oxidases and esterases could be significant in the case of compounds such as pyrethroids that are degraded by both oxidative and hydrolytic modes.