Abstract: 【Aim】 This study aims to clarify the effects of sublethal concentration of indoxacarb on the biological parameters and detoxifying enzyme activities in the cotton bollworm, Helicoverpa armigera with reduced susceptibility to indoxacarb, so as to scientifically control this insect pest and to effectively avoid the rapid development of its resistance to indoxacarb. 【Methods】 The toxicities of indoxacarb to the 3rd instar larvae of the indoxacarb-selected population (TP) of H. armigera and its homologous control population (CP) were determined with leaf-dipping method. The effects of indoxacarb at the concentration of LC₂₀on the biological parameters of the TP population of the age-stage (F₀) were analyzed by two-sex life table method, and the activities of detoxification enzymes ［mixed function oxidase (MFO), carboxylesterase (CarE) and glutathione S-transferase (GST)］ and acetylcholinesterase (AchE) in the CP and TP populations after exposure for 48 h were assayed. 【Results】 The LC₂₀values of indoxacarb to the 3rd instar larvae of the CP and TP populations of H. armigera were 2.27 and 9.91 mg/L, respectively. After the 3rd instar larvae of the TP population were exposed to LC₂₀ of indoxacarb for 48 h, their growth, pupation rate, emergence rate and adult malformation rate were significantly lower than those of the untreated control, while their age-stage-specific life expectancy (e_xj) was higher than that of the untreated control. Meanwhile the activities of GST and MFO in the 3rd instar larvae of the TP population were significantly increased while the CarE activity was obviously decreased compared with the CP population. 【Conclusion】 The results showed that TP population of H. armigera shows obvious disadvantages of growth and reproduction under the selection pressure of indoxacarb at the concentration of LC₂₀, and has also developed the adaptability to this concentration of indoxacarb. The induced activities of GSTs and MFO in the TP population by LC₂₀ of indoxacarb indicate that the two enzymes are closely related to the resistance to indoxacarb in H. armigera, while the inhibited CarE activity indicates that CarE may be involved in the activation of indoxacarb converting into N-decarbomethoxyllated indoxacarb (DCJW).

Key words: Helicoverpa armigera; indoxacarb, biological parameters, sublethal concentration, enzyme activity, induction effect