Abstract: In order to provide the theoretical basis for the management of the diamondback moth, Plutella xylostella (L.) resistant to abamectin, the sublethal effects of metaflumizone on the experimental populations of both abamectin-resistant (AV-R) and susceptible (AV-S) strains of P. xylostella were evaluated by means of the life table technology. The results showed that the estimated LC₅₀ and LC₂₅ values of leaf dip bioassay of metaflumizone on the 3rd instar larvae were 0.24 and 0.09 mg/L for the AV-S strain, and 0.20 and 0.07 mg/L for the AV-R strain, respectively. Metaflumizone at the sublethal concentration (0.09 mg/L) tested decreased the pupation rate and pupal weight, prolonged the pupal duration and decreased the emergence rate, fecundity, oviposition duration and longevity of adults in the treated generation. Such treatment also decreased the hatchability and larval survival rate of the offsprings and their larval duration. Reproduction parameters such as the intrinsic rate of increase (r_m), finite rate of increase (λ), and the net reproductive rate (R₀) in populations treated with sublethal concentrations of metaflumizone were significantly lower than those of the control populations (P<0.0001). The results also showed that the sublethal concentration of metaflumizone had a greater effect on the AV-R strain than on AV-S strain, and had a greater effect on the current generation than on the offsprings. We conclude that the sublethal concentration of metaflumizone might have significant effects on the population dynamics of P. xylostella, especially the AV-R strain, and metaflumizone might be extremely useful for managing pest resistance to insecticides.

Key words: Plutella xylostella, metaflumizone, abamectin, resistance strain, susceptible strain, sublethal effect, biological parameters