Low Risk of Resistance Evolution of Spodoptera frugiperda to Lufenuron and Chlorfenapyr in China

Spodoptera frugiperda is a highly destructive migratory pest that severely restricts global agricultural production. Chemical insecticides remain the primary means of field population control, yet the resistance evolution risk of S. frugiperda to two commonly applied insecticides, lufenuron and chlorfenapyr, remains poorly clarified in China. In this study, we found that the four field S. frugiperda populations collected from Jiangsu, Guangxi, Guizhou, and Yunnan Provinces exhibited susceptible or low-level resistance to chlorfenapyr, lufenuron, emamectin benzoate, and spinetoram. However, moderate resistance to chlorantraniliprole (resistance ratio > 5) was detected in the Guangxi and Guizhou populations, consistent with regional variation in diamide insecticide pressure. After 10 consecutive generations of indoor resistance screening, the selected resistant strains showed only 2.89-fold and 3.40-fold resistance increases to lufenuron and chlorfenapyr, respectively, indicating an extremely slow resistance development rate. Furthermore, the lufenuron-resistant and chlorfenapyr-resistant strains displayed negligible cross-resistance to emamectin benzoate, chlorantraniliprole, and spinetoram. Significant fitness costs were detected in both resistant strains, with marked declines in multiple growth, development and reproductive indicators. Collectively, these findings confirm that Chinese field S. frugiperda populations have a low evolutionary risk of resistance to lufenuron and chlorfenapyr, and resistance emergence is constrained by obvious fitness trade-offs. This study provides empirical evidence and theoretical guidance for the scientific formulation of S. frugiperda chemical control and resistance management strategies in China, while highlighting the need for region-specific monitoring of diamide resistance.