Imidacloprid-resistant Aphis gossypii populations are more common in cotton-dominated landscapes

Widespread reports of reduced efficacy of imidacloprid for managing cotton aphids (Aphis gossypii Glover) in cotton (Gossypium hirsutum L.) prompted an investigation to characterize the susceptibility of 43 populations over a 2-year period. The susceptibility of A. gossypii populations to imidacloprid was examined by calculating LC50 values. Further analyses related resistance assay results to a gradient of cotton production intensity.

Concentration-mortality bioassays documencted populations that were 4.26-607.16 times more resistant than the susceptible laboratory population. There was a significant positive relationship between LC₅₀ values and percentage of cotton within 2.5- and 5-km buffers surrounding collection sites. No significant relationship was detected between LC₅₀ values and the percentage of alternative crop and noncrop hosts.

Variable and high levels of resistance were detected in A. gossypii populations, and this variation was positively associated with cotton production intensity. Cotton is a host that may receive multiple applications of neonicotinoids (via seed treatment and foliar sprays) annually for seedling and mid-season pests. Rotating modes of action and limiting insecticide use should be implemented to delay the evolution of insecticide resistance in A. gossypii populations. © 2022 Society of Chemical Industry.