Abstract: 【Aim】 The aim of this study is to evaluate the sensitivity of field populations of the fall worm, Spodoptera frugiperda, in Hubei, central China to four insecticides, and to detect the genotype and mutation frequency of the insecticide target genes Ace-1, VGSC and RyR, so as to ascertain the insecticide sensitivity of field populations of S. frugiperda in Hubei and to provide guidance for scientific application of pesticides. 【Methods】 The sensitivity of S. frugiperda larvae collected from corn fields in four regions, Huanggang, Wuxue, Xianning and Jingzhou of Hubei to four insecticides, chlorantraniliprole, spinetoram, indoxacarb and methylamino abamectin benzoate, was investigated using a standard leaf-dip bioassay. Eighty larvae from 4 regions were used for total RNA isolation and cDNA synthesis, and the target fragments were amplified by PCR using specific primers. Besides, the genotypes and target site mutation frequencies of Ace-1, VGSC, and RyR were determined by sequence alignment and sequencing chromatogram peak analysis. 【Results】 Toxicity assays showed that the four field populations of S. frugiperda larvae in Hubei were susceptible to all the tested insecticides, and the sensitivity of these populations to four insecticides was as follows: methylamino abamectin benzoate>spinetoram>chlorantraniliprole>indoxacarb. The sequencing results demonstrated that in the four field populations of S. frugiperda the resistant heterozygote of all three mutations of Ace-1 (A201S, G227A, and F290V) was detected, while the resistant homozygote of F290V was detected. However, no site mutation in VGSC and RyR was detected in all the tested field populations of S. frugiperda. 【Conclusion】 Though the four field populations of S. frugiperda in Hubei are susceptible to the four tested insecticides (chlorantraniliprole, spinetoram, indoxacarb and methylamino abamectin benzoate), these field populations have already carried resistant genes conferring resistance to organophosphorus and carbamate insecticides and possess high resistance risk to these insecticides. Therefore, resistance monitoring needs to be strengthened.

Key words: Spodoptera frugiperda, insecticide sensitivity; Ace-1; VGSC, RyR, genotype, mutation frequency