Residual tau-fluvalinate, a beehive acaricide, disrupts growth and metabolism in the greater wax moth, Galleria mellonella

For almost four decades, efforts to manage the ectoparasitic Varroa mite in colonies of the western honey bee Apis mellifera have involved the use of the acaricide tau-fluvalinate. Consequently, tau-fluvalinate has long been among the most frequently detected pesticides in hives. While tau-fluvalinate residues in hives have been considered hazardous to arthropod residents including the honey bee itself and the greater wax moth Galleria mellonella, a common hive pest, no difference in LC₅₀ values was found between laboratory and field strains of G. mellonella. Consumption of ecologically relevant concentrations of tau-fluvalinate reduced growth rates in both strains and transcriptomic analysis revealed more differentially expressed genes in the fat body (1687) than in the midgut (771). KEGG analysis revealed enriched upregulation of genes in global and overview maps, carbohydrate metabolism, and lipid metabolism pathways. No detoxification-related pathways were enriched in upregulated genes; broader suppression rather than induction of detoxification gene expression was observed. These findings indicate that G. mellonella may not activate metabolic processes to promote resistance or tolerance to tau-fluvalinate. The pesticide likely disrupts normal physiological functions, leading to chronic stress and resource allocation shifts that impair development and fitness. Given the highly lipophilic nature of hive environments, where beeswax serves as a major structural component, pesticide persistence in the hive may prolong exposure effects in arthropod residents. While this prolonged exposure could increase selective pressure on some nest-dwelling species, the extent to which resistance evolves in G. mellonella or other hive inhabitants remains unclear, presenting challenges for designing resistance management plans.