Comparative Bioefficacy of Insecticides Against Regional Populations of the Brown Planthopper, Nilaparvata lugens (StÅl), from Different Rice-Growing Regions of India

The brown planthopper (Nilaparvata lugens Stål) is a major rice pest capable of causing substantial yield losses. We evaluated the bioefficacy of 11 insecticides against brown planthopper populations collected from five rice-growing regions of India: Kampasagar (Telangana), Gangavathi (Karnataka), Raipur (Chhattisgarh), Bargarh (Odisha) and Ludhiana (Punjab), along with a susceptible glasshouse population. Bioassays were conducted using 7-9-day-old nymphs reared on rice variety TN1 under glasshouse conditions. Mortality was recorded at 2, 24, 48 and 72 h after treatment, except for buprofezin, which was assessed up to 120 h. Dinotefuran exhibited the highest efficacy, causing >90% mortality within 72 h in most populations, followed by dichlorvos (82-95%), chlorpyriphos (78-92%) and fipronil (75-89%). Buprofezin was least effective, causing <45% mortality even at 120 h. We observed maximum susceptibility in the glasshouse population, whereas the Gangavathi population showed comparatively lower susceptibility. These findings demonstrate regional variation in insecticide response and support location-specific management of N. lugens in rice.