Residual toxicity of insecticides used against the Asian citrus psyllid and resistance management strategies with thiamethoxam and abamectin
MetadataShow full item record
AuthorVanaclocha, Pilar; Jones, Moneen M.; Tansey, James A.; Monzó, César; Chen, Xulin; Stansly, Philip A.
Cita bibliográficaVanaclocha, P., Jones, M. M., Tansey, J. A., Monzó, C., Chen, X., & Stansly, P. A. (2019). Residual toxicity of insecticides used against the Asian citrus psyllid and resistance management strategies with thiamethoxam and abamectin. Journal of pest science, 92(2), 871-883.
The Asian citrus psyllid (ACP) is the key pest of citrus due to its role as vector of huanglongbing. ACP control mostly relies on frequent insecticide applications therefore increasing selection for insecticide resistance. Optimization of field application rates and rotation of insecticide modes of action (MoA) would minimize this risk. Baseline toxicity responses of ACP to commonly used insecticides provide a basis for defining application field rates and are thus needed to track potential development of resistance. Residual toxicities of 12 insecticides were evaluated through quantal response bioassays. The development of ACP resistance in response to monthly applications of two insecticides with different MoAs, abamectin and thiamethoxam, applied separately, in rotation or as mixtures was also tested. Highest residual toxicities were found for the abamectin + thiamethoxam mixture. In general, nymphs were more sensitive than adults to residues. Nymphs were 10 and 28 times more sensitive than adults to residues of thiamethoxam and imidacloprid, respectively. We found a wide range among ratios of maximum label field concentrations and estimated LC90s. Highest label rates for malathion and dimethoate were more than 30 times greater than LC90s, in contrast to abamectin, zeta-cypermethrin and fenpyroximate which were 4–7 times lower. Abamectin appeared to synergize the mixture of it with thiamethoxam. We observed resistance to both active ingredients, especially abamectin, after 8 months of sequential applications of both insecticides individually or in mixture. Rapid resistance development of the mixture relative to rotation was attributed to loss of the synergetic effect of abamectin on thiamethoxam.