Toxicities and sublethal effects of seven neonicotinoid insecticides on survival, growth and reproduction of imidacloprid-resistant cotton aphid, Aphis gossypii.

Imidacloprid has been a major neonicotinoid insecticide for controlling Aphis gossypii (Glover) (Homoptera: Aphididae) and other piercing-sucking pests. However, the resistance to imidacloprid has been recorded in many target insects. At the same time, cross-resistance of imidacloprid and other insecticides, especially neonicotinoid insecticides, has been detected. Results showed that the level of cross-resistance was different between imidacloprid and tested neonicotinoid insecticides (no cross-resistance: dinotefuran, thiamethoxam and clothianidin; a 3.68-5.79-fold cross-resistance: acetamiprid, nitenpyram and thiacloprid). In the study of sublethal effects, imidacloprid at LC(20) doses could suppress weight gain and honeydew excretion, but showed no significant effects on longevity and fecundity of the imidacloprid-resistant cotton aphid, A. gossypii. However, other neonicotinoid insecticides showed significant adverse effects on biological characteristics (body weight, honeydew excretion, longevity and fecundity) in the order of dinotefuran > thiamethoxam and clothianidin > nitenpyram > thiacloprid and acetamiprid. The results indicated that dinotefuran is the most effective insecticide for use against imidacloprid-resistant A. gossypii. To avoid further resistance development, the use of nitenpyram, acetamiprid and thiacloprid should be avoided on imidacloprid-resistant populations of A. gossypii.