Abstract:

 In order to provide the theoretical basis for integrated control of Tetranychus turkestani in Xinjiang province, the sublethal effects of abamectin and pyridaben on experimental populations of T. turkestani were studied. A leaf disc bioassay was employed to examine the effects of sublethal dosage of abamectin and pyridaben on adults and eggs of experimental populations of T. turkestani by means of life tables. The results showed that the fecundity, averagelongevity and egg hatchability of the adults treated by two sublethal concentrations (LC₁₀ and LC₂₀) of abamectin and pyridaben were shortened obviously. The periods of egg, larva, nymph and preoviposition were greatly longer than those of the control, while the adult period and female longevity were significantly shorter than those of the control. The net reproduction rate (R₀), finite rate of increase (λ), survival rate and average number of eggs laid per female per day in first filial generation were markedly decreased compared to the control. The intrinsic rates of increase（r_m） dropped from 0.37 to 0.17-0.29. The mean generation time (T) were all shortened than the controls except for abamectin（LC₂₀）. The population doubling time (Dt) was prolonged. When the eggs were treated by these two sublethal concentrations (LC₁₀ and LC₂₀) of abamectin and pyridaben, the intrinsic rates of increase （r_m） dropped from 0.32 to 0.11-0.22. The net reproduction rate (R₀), the mean generation time (T) and finite rate of increase (λ) were decreased, but the population doubling time (Dt) was extended. The periods of larva, nymph and preoviposition were greatly longer than those of the control, while the adult period and female longevity were dramatically shortened than those of the control. The survival rate and average number of eggs laid per female per day were significantly decreased. These results demonstrated that the sublethal dosage of abamectin and pyridaben could decrease the developmental rate of laboratory populations of T. turkestani, which has positive significance toward developing integrated pest management strategies.

Key words: Tetranychus turkestani, sublethal effect, abamectin, pyridaben, life-table