Sublethal concentration of beta-cypermethrin results in the mating failure of Helicoverpa armigera by inhibiting sex pheromone biosynthesis

Abstract

Beta-cypermethrin is a commonly used insecticide for controlling major agricultural pests as Helicoverpa armigera in crop fields. This study investigated the sublethal effect of beta-cypermethrin on the mating physiology of H. armigera. The results demonstrated that the sublethal exposure to beta-cypermethrin significantly decreased sex pheromone production, hindered female ability to attract males and reduced the proportion of successful matings. Further investigations revealed that trehalose content in the sex pheromone glands (PGs) significantly decreased following sublethal beta-cypermethrin treatment, leading to a subsequent decrease of acetyl-CoA content within the PGs. Furthermore, such exposure caused a significant decrease in mRNA expression levels of the trehalose transporter, calcineurin (CaN), acetyl CoA carboxylase (ACC), protein kinase A (PKA), pheromone biosynthesis-activating neuropeptide receptor (PBANR), Δ11-desaturase (DES) and fatty acid reductase 2 (FAR2), as well as a decrease in the enzyme activities of membrane-bound trehalase, ACC, CaN and PKA. Sublethal exposure lowered the expression levels of pheromone binding protein 1, pheromone binding protein 2 and odorant receptor 13 in males, suggesting decreased male recognition capabilities. Altogether, sublethal exposure to beta-cypermethrin resulted in a decrease in the precursor material (trehalose, acetyl-CoA) and enzyme activities involved in sex pheromone biosynthesis, This, in turn, led to reduced pheromone production and female attractiveness, as well as diminished male detection abilities, ultimately resulted in a lowered likelihood of successful mating. This study enhances knowledge on how sublethal pesticide exposure affects pest biology and their mechanisms of action, providing a basis for including such impact in pest management strategies.