Abstract

Imidacloprid is a nicotinic acetylcholine receptor (nAChR) agonist with potent insecticidal activity. However, resistance to imidacloprid is a significant threat and has been identified in several pest species. Cycloxaprid with cis-configuration is a novel neonicotinoid insecticide, which shows high activity against imidacloprid-resistant pests. The LC₅₀ of imidacloprid against the resistant Aphis gossypii was 14.33 mg L^?1 while it was only 0.70 mg L^?1 for the susceptible population, giving a resistance ratio of 20.47. In this imidacloprid-resistant population, a point mutation (R81T) located in the loop D region of the nAChR β1 subunit was found out. But this point mutation did not decrease the activity of cycloxaprid against A. gossypii. The LC₅₀ of cycloxaprid was 1.05 and 1.36 mg L^?1 for the imidacloprid-susceptible and imidacloprid-resistant populations, respectively. In addition, cycloxaprid provided better efficacies against resistant A. gossypii than imidacloprid in the fields. Although cycloxaprid was highly toxic to A. gossypii, it showed high selective activity between A. gossypii and its predominant natural enemies, Harmonia axyridis and Chrysoperla sinica. These results demonstrate that cycloxaprid is a promising insecticide against imidacloprid-resistant A. gossypii and suitable for the integrated pest management.