Species-specific insecticide resistance to imidacloprid and fipronil in the rice planthoppers Nilaparvata lugens and Sogatella furcifera in East and South-east Asia

BACKGROUND: In 2003 the development of insecticide resistance against neonicotinoids in the brown planthopper (BPH), Nilaparvata lugens (Stål) (Homoptera: Delphacidae), was first observed in Thailand and has since been found in other Asian countries such as Vietnam, China and Japan. However, the LD₅₀ values of BPH and the whitebacked planthopper (WBPH), Sogatella furcifera (Horváth), against both neonicotinoid and phenylpyrazole insecticides have been poorly reported in many Asian countries.RESULTS: The topical LD₅₀ values for imidacloprid in the BPH populations collected from East Asia (Japan, China, Taiwan) and Vietnam in 2006 were 4.3-24.2 μg g⁻¹ and were significantly higher than those collected from the Philippines (0.18-0.35 μg g⁻¹). The BPH populations indicated a positive cross-resistance between imidacloprid and thiamethoxam. Almost all the WBPH populations from Japan, Taiwan, China, Vietnam and the Philippines had extremely large LD₅₀ values (19.7-239 μg g⁻¹ or more) for fipronil, except for several populations from the Philippines and China.CONCLUSION: Species-specific changes in insecticide susceptibility were found in Asian rice planthoppers (i.e. BPH for imidacloprid and WBPH for fipronil). Insecticide resistance in BPH against imidacloprid occurred in East Asia and Indochina, but not in the Philippines. In contrast, insecticide resistance in WBPH against fipronil occurred widely in East and South-east Asia. Copyright