Assessment of Insecticide Resistance, Biological Characteristics, and Detoxification Enzyme Activity in Rice Brown Planthopper (Nilaparvata lugens) from the Gangavathi Region, India
The brown planthopper, Nilaparvata lugens (Stål), is a major insect pest of rice, and its management is increasingly constrained by insecticide resistance. This study assessed insecticide susceptibility, detoxification enzyme activity, and biological characteristics in a Gangavathi field population relative to a long-term susceptible glasshouse population. Resistance ratios were highest for buprofezin (1403.3-fold), imidacloprid (931.3-fold), and ethiprole + imidacloprid (515.7-fold), while thiamethoxam reached 124.0-fold. Chlorpyriphos resistance ratios ranged from 3.6- to 3.9-fold, whereas acephate, dinotefuran, fipronil, and pymetrozine showed ratios below three-fold. Esterase, glutathione S-transferase, and cytochrome P450 monooxygenase activities in the Gangavathi population were 2.2-, 1.8-, and 4.9-fold higher, respectively, than those in the susceptible population. The field population also showed a longer pre-oviposition period (4.3 days), incubation period (7.9 days), nymphal duration (13.7 days), and total life cycle (25.9 days). Conversely, egg hatchability (72.6%), fecundity (221.4 eggs per female), nymphal survival (77.5%), female proportion (53.7%), and brachypterous forms (50.1%) were lower than those recorded in the susceptible population. The findings demonstrate substantial resistance to several frequently used insecticides, particularly buprofezin and imidacloprid, accompanied by enhanced detoxification enzyme activity and altered biological performance. These results provide a basis for location-specific resistance surveillance and the judicious selection of insecticides within integrated brown planthopper management programmes.