Teflubenzuron Resistance in Diamondback Moth (Lepidoptera: Plutellidae)

Laboratory selection of susceptible and field strains of diamondback moth, Plutella xylostella (L.), larvae for 20 generations or more resulted in only 8-12-fold resistance to teflubenzuron, a benzoylphenylurea (BPU) that interferes with chitin synthesis. Cross-resistance with another BPU, chlorfluazuron, or a number of conventional insecticides was not apparent. Selection of larvae with teflubenzuron caused the diamondback moth to develop considerable resistance to the ovicidal effect of this compound. Piperonyl butoxide, an inhibitor of microsomal oxidases, restored the effectiveness of teflubenzuron against larvae and eggs of the selected strains, indicating that microsomal oxidation was the major resistance mechanism. Larvae selected with teflubenzuron exhibited much higher aldrin epoxidase and aryl hydrocarbon hydroxylase activities than those of the susceptible and field strains. Lack of cross-resistance between conventional insecticides and teflubenzuron-chlorfluazuron, and between teflubenzuron and chlorfluazuron suggested that different microsomal oxidases in diamondback moth might be involved.