Abstract: 【Aim】 This study aims to establish the relative susceptible baselines of the fall armyworm, Spodoptera frugiperda, to commonly used insecticides in order to provide basic data for systematically monitoring the resistance of S. frugiperda to insecticides in China. 【Methods】 S. frugiperda individuals were collected from corn fields and bred in the laboratory without exposure to any insecticides for 5-7 generations. The susceptibility of the 3rd instar larvae of S. frugiperda to seven commonly used insecticides (emamectin benzoate, spinetoram, chlorfenapyr, indoxacarb, tetrachlorantraniliprole, lufenuron and chlorantraniliprole) belonging to six pesticide categories was determined by leaf-dip method and topical application, and that of the 2nd instar larvae of S. frugiperda to these seven insecticides was determined by diet surface overlay method. Based on the bioassay results, the relative susceptible baselines of S. frugiperda to these seven insecticides were established. 【Results】 The LC₅₀ or LD₅₀ values of the above seven insecticides to S. frugiperda larvae were 0.054-12.131 mg/L by leaf-dip method, 0.355-4.707 μg/g by topical application (excluding lufenuron), and 0.003-0.238 μg/cm² by diet surface overlay bioassay, respectively. 【Conclusion】 The relative susceptible baselines of S. frugiperda larvae to the commonly used insecticides have been established using three different bioassay methods, providing basic data for the resistance monitoring and chemical control of S. frugiperda in China.

Key words: Spodoptera frugiperda, insecticide, leaf-dip method, topical application, diet surface overlay bioassay, susceptible baseline