First Report of Resistance to Nicotinic Acetyl Choline Receptor Competitive Modulators in Mango Leafhopper, Idioscopus nitidulus (Walker)

Abstract

The susceptibility of mango leafhopper, Idioscopus nitidulus (Walker) (Hemiptera: Cicadellidae), to selected insecticides was assessed during 2024–25 in populations collected from two locations, viz., Muthalamada, Palakkad, the major mango-growing tract of Kerala, and from Vellanikkara, Thrissur (Susceptible check). Bioassays were conducted using commercial formulations of imidacloprid (IRAC 4A), thiamethoxam (IRAC 4A) and flupyradifurone (IRAC 4D). The LC50 values for imidacloprid, thiamethoxam, and flupyradifurone in the Muthalamada population were 172.730, 25.249, and 145.079 ppm, respectively, corresponding to resistance of 137.52, 37.85, and 27.23-fold when compared with the susceptible Vellanikkara population, indicating very high resistance to imidacloprid and moderate resistance to thiamethoxam and flupyradifurone. Enzyme assays revealed elevated detoxification enzyme activities in the Muthalamada population, with carboxylesterase, glutathione S-transferase, and cytochrome P450 monooxygenase activities being 1.25, 1.60, and 2.24-fold higher than those of the susceptible population. Among these, cytochrome P450 monooxygenase activity was highest, suggesting its major role in metabolic detoxification. The increased activities of cytochrome P450 monooxygenases and glutathione S-transferases indicate their involvement in imidacloprid resistance and may partly explain the observed cross-resistance to flupyradifurone. The results highlight the development of resistance in mango leafhopper populations from intensively managed orchards, emphasising the need for effective resistance management strategies in mango ecosystems.