Comparative Toxicity and P450-Mediated Detoxification of Flonicamid in Lygus lineolaris and Lygus hesperus

The tarnished plant bug, Lygus lineolaris (TPB), (Palisot de Beauvois), and the western tarnished plant bug (WTPB), Lygus hesperus, Knight, are major agricultural pests that cause significant damage to a wide range of crops in the southeastern and southwestern United States. Flonicamid (commercial name: Carbine 50WG) is generally effective against various sap-feeding pests, including both L. hesperus and L. lineolaris. This study evaluated the toxicity of flonicamid on third-instar nymphs and adults of both Lygus species under laboratory conditions. Two bioassay methods were used: spray application to assess both contact and oral toxicity, and dipping to evaluate oral toxicity. Results showed that L. hesperus was significantly more susceptible to flonicamid than L. lineolaris across both bioassay methods. While no significant differences in toxicity were observed between spray and dipping assays, third-instar nymphs exhibited significantly higher sensitivity than adults in both species. The addition of piperonyl butoxide (PBO), a known inhibitor of cytochrome P450-monooxygenases (P450s), significantly enhanced the toxicity of flonicamid, suggesting that P450 enzyme plays a critical role in its detoxification. Sublethal exposure to flonicamid also induced increased P450 activity in both species. These findings provide valuable insights into the differences in susceptibility between L. lineolaris and L. hesperus to flonicamid and indicate that P450-mediated detoxification is critical for flonicamid metabolism. Such insights are valuable for early resistance monitoring and optimizing flonicamid application in integrated pest management programs.