Parathion and Methyl Parathion Resistance in Diamondback Moth (Lepidoptera: Plutellidae) Larvae

Abstract

Laboratory selection of a susceptible strain of diamondback moth, Plutella xylostella (L.), with methyl parathion resulted in >2,600-fold resistance to this insecticide and nearly 500-fold cross-resistance to parathion. Selection with parathion caused> 1,000- fold resistance to parathion and methyl parathion. Significantly higher glutathione S-transferase activity towards 1,2-dichloro-4-nitrobenzene was detected in the strain selected with methyl parathion. The increase of microsomal oxidase activity towards 7-methoxyresorufin in the parathion-selected strain was significant as compared with that in the susceptible strain. Nevertheless, in view of the extents of resistance, increases of these two detoxifying enzyme activities were quite limited and did not appear to account for the observed resistance.