Resistance monitoring to four insecticides and mechanisms of resistance in Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) populations of southeastern USA cotton

BACKGROUND Economically damaging infestations of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), have become more frequent in Virginia and North Carolina cotton since 2013 and 2010, respectively. Foliar insecticide use has increased dramatically in response. Efficacy data (LC50) are needed to evaluate L. lineolaris susceptibility and resistance levels (RR50) to commonly used and recommended insecticides for managing this pest in the southeastern USA. RESULTS Elevated resistance levels to acephate and bifenthrin were measured in L. lineolaris populations collected from wild and cultivated hosts in Virginia, North Carolina and northern Alabama when compared to a susceptible laboratory population. High levels of bifenthrin resistance were observed in 2018 and 2019. Mixed‐function oxidase and esterase (EST) inhibitors, piperonyl butoxide and S,S,S‐Tributyl phosphotrithioate, respectively, had a synergistic effect on bifenthrin with resistant populations of L. lineolaris. Bifenthrin‐resistant L. lineolaris populations expressed elevated levels of cytochrome P450 (CYP450) monooxygenase and general EST activity. Results suggest that insecticide resistance is present in some locations and that CYP450 and EST activity in L. lineolaris contribute to pyrethroid resistance in the southeastern USA. CONCLUSIONS Results can serve as a baseline for continued monitoring of L. lineolaris insecticide resistance and inform insecticide resistance management strategies that help southeastern USA cotton producers to minimize inputs and slow resistance development. © 2020 Society of Chemical Industry Adult Lygus lineolaris resistance ratios (RR50) for bifenthrin log‐probit contact assays in 2018 (A) and 2019 (B). Respective symbol colors in resistance maps represent populations with low (≤3), medium (≤10) and high (>10) RR50 values in wild (circle) and cultivated (triangle) hosts in the southeastern USA cotton. Elevated levels of L. lineolaris pyrethroid resistance was observed in 2018 and 2019 in this region.