D3244: Biochemical and molecular characterization of pyrethroids and neonicotinoids resistance in the tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae)

In the southern United States, pyrethroids and neonicotinoids are commonly applied as foliar insecticides to control sucking insect pests, such as the tarnished plant bug (TPB, Lygus lineolaris Palisot de Beauvois). In this study, we conducted spraying bioassays to investigate the resistance levels of adult TPB to six common pyrethroids, five neonicotinoids and sulfoxaflor to susceptible and late fall field-collected TPB adults from Delta of Mississippi. Compared to a susceptible population, the field-collected TPBs showed varying levels of resistance to different pyrethroids, neonicotinoids and sulfoxaflor insecticides. A synergist study demonstrated that P450 inhibitor piperonyl butoxide (PBO) greatly increased the toxicity of pyrethroids and neonicotinoids against resistant TPBs, while triphenyl phosphate (TPP) and diethyl maleate (DEM) only showed 2-3-fold synergism to pyrethroids and neonicotinoids. In the field-collected TPBs, activities of three detoxification enzymes, esterase, glutathione S-transferase (GST) and CYP450 monooxygenase (P450) were significantly increased by 3.43-, 1.48- and 2.7-fold, respectively, when compared to the susceptible population. The synergistic and biochemical assays consistently indicated that P450 and esterase were involved in pyrethroid and neonicotinoid detoxification in TPBs. Further examinations revealed that the expression of certain detoxification genes was significantly elevated in resistant TPBs. Overall, these results suggest that elevated P450s expression and enzyme activity are key mechanisms for metabolic resistance in TPBs to pyrethroids and neonicotinoids. Our findings provide valuable information for the continued use of pyrethroids, selection and adoption of neonicotinoid insecticides for resistance management of TPBs in the Mississippi Delta region.