Abstract: 【Objective】 Spodoptera exigua is a polyphagous pest and shows different characteristics of growth and development under the selective pressure of different environments, drugs and so on. Chlorantraniliprole, a novel insecticide that acts on ryanodine receptors, has highly activity to those insects in Lepidopteran. The objective of this study is to explore the effects of S. exigua larvae treated by the sublethal doses of chlorantraniliprole on the toxicities, the activities of three main detoxifying enzymes, including carboxylesterase (CarE), glutathione S-transferase (GSTs), and mixed-function oxidase (MFOs), and population breeding.【Method】 The toxicities of chlorantraniliprole on SE-Lab and SE-Sel strains were detected by incorporation bioassay and the SE-Sel strain was achieved with continuous selecting with LC₂₅ sublethal doses for six generations from SE-Lab strain, then the synergistic effects of enzyme inhibitors (TPP, DEM, PBO) with chlorantraniliprole on the SE-Lab and SE-Sel strains were assayed using the dip-leaf method. The toxicities of chlorantraniliprole on the insects which were fed the leaves soaked with the solution of enzyme inhibitor or 0.1% TritonX-100 as blank control before 12 h were assayed by the dip-leaf method. The midgut and fatbody of tested insects were dissected on the ice and the effects of the sublethal doses of chlorantraniliprole and enzyme inhibitors on three metabolic detoxification enzyme activities were analyzed by the determination of detoxification enzyme activities. According to the age-stage two-sex life tables theory, the growth, mortality, fecundity data of the tested insects were also recorded to analyze the differences of the age-stage two-sex life table parameters between the strains of SE-Lab and SE-Sel. 【Result】 The synergistic effect of the PBO was the strongest among the three enzyme inhibitors and the synergic ratios on the strains of SE-Sel and SE-Lab reached 1.58- and 1.69-fold, respectively. The activities of the three detoxification enzymes, which were induced by the continuous selection of the sublethal doses of chlorantraniliprole, were promoted and the MFOs activities were the most significant, which of the SE-Sel strain in the midgut and fatbody were enhanced by 2.07- and 2.10-fold, meanwhile, the MFOs activities of the insects of SE-Sel induced by the sublethal dose of chlorantraniliprole again were also promoted by 4.02- and 3.44-fold in the midgut and fatbody compared to those in SE-Lab strain, respectively. The enzyme activities of three detoxifying enzymes were decreased when the tested insects were treated with enzyme inhibitors and the descend range of MFOs activity among the three enzymes was maximum, which was only 42.3%-44.8% compared to the treatment not treated with the enzyme inhibitor. The adult preoviposition period and total preoviposition period of F₁ generation of SE-Sel strains became shorter and spawning quantity of became higher compared to those in F₁ generation of SE-Lab. SE-Sel strains had the longest mean generation time and least amount of eggs. The intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R₀) of SE-Sel strain were significantly lower than those in SE-Lab strain. The r, λ and R₀ values of SE-Lab and SE-Sel strains were 0.18 and 0.16 d^-1, 1.20 and 1.17 d^-1, 358.42 and 203.12 d^-1, respectively. Even though the mean generation times of SE-Sel strain was longer than SE-Lab strain, there was no significant difference between the two strains.【Conclusion】MFOs may be the major detoxication enzyme on the metabolic detoxification of chlorantraniliprole in the S. exigua and involved in the formation of resistance. A longer generation period, lower fecundity and slower population growth of S. exigua were demonstrated when it was treated by a continuous selection of lethal dose of chlorantraniliprole. The sublethal doses of chlorantraniliprole have a continuous control effect on S. exigua.

Key words: Spodoptera exigua, chlorantraniliprole, sublethal doses, synergists, MFOs, age-stage two-sex life tables