Acaricidal effects of clove oil-based nanoemulsion on Varroa destructor: colony-level, in silico molecular docking, and ADMET studies

Varroa destructor is one of the most destructive parasites affecting honey bee (Apis mellifera L.) colonies worldwide, and resistance to commonly used acaricides is increasing the need for alternative control methods. In this study, the acaricidal efficacy of clove (Syzygium aromaticum L.) oil-based nanoemulsions (NEms) was evaluated under field conditions, and their mechanisms of action were investigated using molecular docking analysis. The average droplet size of the prepared NEms was 249.5 nm, with a polydispersity index (PDI) of 0.553. Field results showed dose-dependent efficacy rates of 65.2%, 72.3%, and 78.1% at concentrations of 50, 100, and 200 ppm, respectively, which were higher than those of the positive control group (flumethrin, 43.5%). GC-MS analysis revealed that the main component of clove oil was eugenol at 64.55%, followed by caryophyllene and humulene. Molecular docking results showed that eugenol, caryophyllene, and humulene exhibited binding affinities of −6.483, −6.156, and −5.515 kcal/mol with acetylcholinesterase (AChE) enzyme, and −6.143, −6.487, and −6.334 kcal/mol with odorant binding protein (OBP), respectively. These findings suggest that NEms may possess both neurotoxic and behavioral mechanisms of action. In conclusion, clove oil NEms have been shown to be an environmentally friendly and effective alternative for controlling Varroa mites.