Insecticidal efficacy of green-synthesized copper nanoparticles and their impact on detoxification genes in the khapra beetle.

The khapra beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae), is a highly destructive and quarantine-significant pest of numerous stored grain products. Despite increasing resistance, its management still heavily relies on chemical insecticides. Green nanoparticles (NPs) have recently been extensively studied as promising alternatives for pest control. In this study, ultra-small copper NPs (Cu NPs) (6.59 ± 0.57 nm) were synthesized using Origanum sp. extract. The insecticidal efficacy of Cu NPs was evaluated, and the 300 ppm concentration exhibited the highest mortality (93.3%) in T. granarium adults. The LC₅₀ and LC₉₀ values were 203.3 ppm and 268.3 ppm, respectively, at 144 h. Due to their roles in detoxifying reactive oxygen species (ROS) and neurotransmission, the genes Superoxide dismutase (TgSOD), Catalase (TgCAT), Glutathione Peroxidase (TgGPX), and Acetylcholinesterase (TgACHE) were identified in the cDNA library of T. granarium for gene expression analysis. Remarkable abundance of the four genes was detected at 200 ppm after 48 h, suggesting that their upregulation may be associated with oxidative stress induced by Cu NPs. It can be inferred that green-synthesized Cu NPs may have an insecticidal effect on T. granarium and can be considered an alternative pest management tool.