Insecticide Resistance in the Diamondback Moth1

Abstract

Fifteen insecticides were tested for their efficacy against one susceptible (S) and two field (Peng-hu and Ban-chau) strains of Plutella xylostella (L.). The synthetic pyrethroids (permethrin, cypermethrin, decamethrin, and fenvalerate) had the highest inherent toxicity to the S strain, and the organophosphorus compounds were one to two orders less effective, except Tokuthion® (O-2,4-dichlorophenyl-O-ethyl, S-propylphosphorodithioate), which was almost as toxic as the four synthetic pyrethroids. DDT, cartap, and methomyl were intermediately toxic, whereas carbaryl and propoxur were the least effective. The Peng-hu strain was only slightly resistant, whereas high levels of resistance to all compounds tested were observed in the Ban-chau strain. Nevertheless, the four synthetic pyrethroids remained the most potent, followed by Tokuthion,® cartap, and dichlorvos, to this highly multiresistant population of the diamondback moth.