Risk assessment, resistance monitoring and mechanism of field-evolved resistance to broflanilide in the tobacco cutworm, Spodoptera litura

Abstract

Spodoptera litura, a globally destructive agricultural pest, has evolved significant resistance to many popular insecticides. Broflanilide, a new meta-diamide pesticide that targets the specific site of γ-aminobutyric acid (GABA) receptor, provides broad-spectrum control against pests in the orders Lepidoptera and Thysanoptera. However, its potential resistance risk in S. litura remains unclear. In this study, a laboratory-selected strain was generated through ten consecutive generations of selection with broflanilide, revealing a low overall risk for resistance development. Concurrently, field resistance monitoring across China indicated that most S. litura populations remained highly susceptible, while the Sanya (SY) population exhibited moderate resistance (26.8-fold). Following seven additional generations of selection, the SY population evolved high resistance (56.2-fold) and was designated the SY-R strain. Using SY-R, we investigated inheritance, cross-resistance, and mechanism of detoxification underlying field-evolved resistance. Broflanilide showed minimal cross-resistance to the tested pesticides. Genetic and synergistic analyses indicated that resistance was incompletely dominant, autosomal, and polygenic, primarily associated with detoxification of glutathione S-transferase (GST) and cytochrome P450 (P450). These findings provide a comprehensive assessment of broflanilide resistance risk and provide valuable information and data for developing effective strategies of pesticide resistance management.