Abstract: 【Aim】 Abamectin is one of the commonly used insecticides in forestry systems. This study aims to investigate the sublethal effects of abamectin on a natural enemy insect, Sclerodermus alternatusi. 【Methods】 The toxicity of abamectin to S. alternatusi adults was determined by topical application. After treatment with sublethal doses ［LD₁₀ (3.20×10^-5 μg/individual) and LD₃₀ (8.86×10^-5 μg/individual)］ of abamectin to female adults of S. alternatusi, the changes in the developmental duration, fecundity, survival rate, and longevity of female and male adults of the F₁ generation were determined, and the age-stage, two-sex life table was constructed. 【Results】 Compared to the blank control (non-subjected to any treatment), both LD₁₀ and LD₃₀ of abamectin significantly reduced the male adult longevity of S. alternatusi, but had no significant effects on the egg, larval and pupal duration. However, LD₁₀ of abamectin significantly extended the female adult longevity of S. alternatusi. Additionally, the average numbers of laid eggs per female of the F₁ generation in treatments with LD₁₀ and LD₃₀ of abamectin increased by 24.70% and 64.56%, respectively, as compared with that in the blank control. Furthermore, the results of population parameters of the F₁ generation revealed that, compared to the blank control, both LD₁₀ and LD₃₀ of abamectin significantly extended the mean generation time (T) of S. alternatusi by 7.01% and 4.38%, respectively, but had no significant impact on the intrinsic rate of increase (r) and finite rate of increase (λ). The net reproductive rate (R₀) of S. alternatusi in the treatment group with LD₁₀ of abamectin significantly increased as compared to that in the blank control group. 【Conclusion】 Sublethal doses of abamectin significantly inhibited the survival and increased the fecundity of females of S. alternatusi offspring, but had no significant impact on its population growth. Therefore, abamectin is a promising insecticide for the control of forest pests without affecting the population survival of their natural enemies.

Key words: Sclerodermus alternatusi, abamectin, sublethal effect, age-stage, two-sex life table, fecundity