Sublethal Dose of β -Cypermethrin Impairs the Olfaction of Bactrocera dorsalis by Suppressing the Expression of Chemosensory Genes.

The oriental fruit fly, Bactrocera dorsalis , is one of the most destructive fruit insect pests. β -cypermethrin has been widely used in the orchard to control this major insect. Based on the resistance monitoring in 2011, B. dorsalis developed significant resistance against β -cypermethrin in fields. This indicated that the B. dorsalis has been exposed to sublethal concentrations of β -cypermethrin in the field for a long time. Thus, it is urgent to understand the sublethal effects of β -cypermethrin on this fly to guide the rational use of an insecticide. According to the olfactory preference assays and electroantennogram (EAG) recording, the B. dorsalis after β -cypermethrin exposure (LD 30 = 10 ng/fly) severely decreased the ability to perceive the tested odorants. Moreover, we then performed quantitative real-time PCR and found the chemosensory genes including odorant receptor co-receptor ( BdorORco ) and ionotropic receptor co-receptors (BdorIRcos) were obviously suppressed. Our results demonstrated that the sublethal dose of β -cypermethrin impairs the olfaction of the pest insects by suppressing the expression of chemosensory genes ( BdorORco and BdorIRcos), which expanded our knowledge of the sublethal effects of the pesticide on insects.