Studies on Metabolism of Parathion in Parathoin Susceptible and Resistant Larvae of the Rice Stem Borer

The mechanism of metabolic detoxication of parathion in the rice stem borer was examined in relation to parathion resistance. From each of susceptible and resistant larvae, O, O-diethyl phosphorothioic acid, O, O-diethyl phosphoric acid, des-ethyl parathion, des-ethyl paraoxon and monoethyl phosphoric acid (or phosphoric acid) were detected, but there were differences in quantities of each metabolite. But there were almost equal amount of des-ethyl parathion, O, O-diethyl phosphorothioic acid and monoethyl phosphoric acid (or phosphoric acid) in the susceptible and resistant larvae. However, O, O-diethyl phosphoric acid was the predominant metabolite in the susceptible larvae while des-ethyl paraoxon was predominant in the resistant larvae. It seems that alkyl-phosphate bond of paraoxon is a “weak link” which is responsible for selective toxicity between parathion susceptible and resistant larvae of the rice stem borer.