Abstract: 【Aim】 Spodoptera litura (Fabricius) is an important agricultural insect pest, and its growth and development are different under the selective pressure of different drugs and environments. Thiacloprid, the second neonicotinoid insecticide, has potent agonist activity on nicotinic acetylcholine receptors of insects. This study aims to explore the sublethal effects of thiacloprid on S. litura so as to provide a scientific basis for the integrated management program for S. litura and the rational use of thiacloprid. 【Methods】 The toxicity of thiacloprid on the 3rd instar larvae of S. litura was assayed with diet-incorporation bioassays, and the effects of thiacloprid at two sublethal doses (LC₂₅ and LC₅₀) on the activities of three detoxifying enzymes including the carboxylesterase (CarE), glutathione-S-transferase (GSTs) and P450-ECOD were analyzed by in vitro enzyme activity assay. The growth, fecundity and population growth data of the tested insects were recorded, and the differences of the age-stage two-sex life table parameters between the LC₂₅ and LC₅₀ treatment groups and the control group of the offspring (F₁) of S. litura were analyzed by using the age-stage two-sex life table method. 【Results】 The results showed that when the 3rd instar larvae of S. litura were treated with two sublethal doses of thiacloprid (LC₂₅ and LC₅₀) for 48 h, the CarE activities obviously increased by 14.2% and 45.1%, respectively, whereas the GSTs activities were inhibited significantly with the inhibition rates of 9.8% and 37.1%, respectively, as compared with those in the control. The activities of P450-ECOD in the treatment groups decreased with the inhibition effect positively related to the thiacloprid doses, but had no significant difference from those in the control group. The preadult duration of F₁ generation in the LC₂₅ and LC₅₀ treatment groups was prolonged about 3.05 d and 4.80 d, respectively, as compared with that of the control group, while the male adult longevities were shorten by 2.06 and 3.31 d, respectively, the female adult longevities were shortened by 0.13 and 0.92 d, respectively, and the mean numbers of eggs laid per female were decreased significantly by 17.7% and 33.3%, respectively. The pupation rates in the LC₂₅ and LC₅₀ treatment groups were decreased by 10.7% and 11.4%, respectively, and the intrinsic rates of increase (r), finite rates of increase (λ) and net reproductive rates (R₀) were significantly lower than that of the control group, and the mean generation time (T) became longer obviously. 【Conclusion】 The results demonstrate that CarE may be the major enzyme in the metabolic detoxification of thiacloprid in S. litura and involved in the resistance development, and the sublethal dose of thiacloprid can significantly restrain the growth, development and reproduction of S. litura.

Key words: Spodoptera litura, thiacloprid, sublethal effect, metabolic detoxification enzyme, agestage twosex life table