Insecticide resistance profiling in field populations of brown planthopper from major rice zones

Abstract:

Insecticide resistance — the heritable decline in a pest population’s susceptibility to a chemical control agent — is now the single largest obstacle to sustained management of the brown planthopper (BPH), Nilaparvata lugens (Stål), in Asian rice systems. This research profiled resistance levels in five BPH field populations collected from major rice-growing zones in the Philippines, Vietnam, China, India, and a laboratory-susceptible reference colony maintained at Galashiels, Scotland. Topical-application bioassays were run against three widely used compounds: imidacloprid (neonicotinoid), buprofezin (chitin synthesis inhibitor), and pymetrozine (pyridine azomethine). Resistance ratios (RR) for imidacloprid ranged from 3.8-fold in the Mekong Delta population to 14.6-fold in Central Luzon, indicating moderate-to-high resistance across all four field populations. Buprofezin RR values were lower (2.1-6.8), while pymetrozine resistance remained below 5-fold everywhere except Jiangsu (RR = 7.3). Cross-resistance between imidacloprid and pymetrozine was not detected. These baseline profiles provide a reference for regional insecticide resistance management programmes and support rotating insecticide modes of action to slow resistance evolution in BPH.