Abstract: 【Aim】In this study, the sublethal effects of indoxacarb and beta-cypermethrin on Plutella xylostella (L.) were investigated so as to further understand the mechanism of insecticides and provide a theoretical basis for proper application of pesticides and mitigating the damage to environment and negative effects on agriculture. 【Methods】 Leaf dipping method was used to test the acute toxicity of indoxacarb and beta-cypermethrin to the 2nd instar larvae of P. xylostella, and the LC₁₅, LC₃₀ and LC₅₀ values of indoxacarb (designated as TI-LC₁₅, TI-LC₃₀ and TI-LC₅₀, respectively) and beta-cypermethirn (designated as TB-LC₁₅, TB-LC₃₀ and TB-LC₅₀, respectively) were determined. After the 2nd instar larvae of P. xylostella were exposed to the six lethal concentrations above for 48 h, the biological characteristics including the survival rate, developmental duration, and larval and pupal weight were recorded, the fecundity and adult longevity were also investigated, and the age-stage and two-sex life tables was established to analyze the subthal effects of indoxacarb and beta-cypermethrin on biological characteristics of the offsprings of P. xylostella. 【Results】 The developmental duration in TI-LC₃₀, TI-LC₅₀, TB-LC₁₅, TB-LC₃₀ and TB-LC₅₀ groups were significantly longer than that of the control group （P<0.05）, and the larval and pupal weight and fecundity tended to decrease (P<0.05). But the developmental duration of the 3rd and 4th instar larvae in TI-LC₁₅ group was significantly shorter than that of the control group （P<0.05）. The total oviposition periods of offsprings in TI-LC₃₀, TI-LC₅₀, TB-LC₃₀ and TB-LC₅₀ groups were significantly shortened (P<0.05). Meanwhile, the fecundity of these groups was significantly decreased compared to that of the control (P<0.05). The mean values of the intrinsic rate of increase (r_m), finite rate of increase (λ), gross reproductive rate (GRR) and net reproductive rate (R₀) were significantly lower in all the treatment groups than in the control group (P<0.05). 【Conclusion】 The low concentrations of indoxacarb and beta-cypermethrin could restrain the growth and development of P. xylostella, decrease the fecundity of its parents and offsprings and reduce the population growth of its offsprings.

Key words: Plutella xylostella, indoxacarb, beta-cypermethrin, sublethal effects, growth and development, population growth