Protective Effects of a Polyphenolic Fraction of Bergamot in Improving the Welfare Index in Honeybees (Apis mellifera) Co-Exposed to Deltamethrin and Flupyradifurone: A Laboratory Cage Study

The simultaneous presence of multiple pesticide residues in the environment impairs honeybee health and survival. The toxicological interactions could result in additive, synergistic, or antagonistic effects as documented in previous studies. In most cases, the co-exposure produces an amplification of the singular toxicity, resulting in additive or synergistic effects. More rarely, the interaction of active principles leads to antagonistic effects. Previous studies demonstrated that deltamethrin (DMT, a type II pyrethroid) and flupyradifurone (FLU, a butenolide insecticide) produce antagonistic toxicity when co-administered orally to caged Apis mellifera workers, and that dietary supplementation with the bergamot polyphenolic fraction (BPF) independently protects against FLU- and DMT-induced intoxication. The present study investigates the three-way interaction of DMT, FLU, and BPF on honeybees. Survival rate, solution consumption, and abnormal behavior have been recorded over a 72-h exposure period in groups of twenty caged honeybees orally treated with DMT (21.6 mg/L), FLU (50 or 100 mg/L), their binary combinations, or their ternary combinations with BPF (1 mg/kg). Results demonstrate that BPF alone did not differ from control (p > 0.05) at any time point, confirming its safety. Binary combinations of DMT and FLU showed antagonistic survival profiles consistent with our previous report. The addition of BPF to both binary pesticide combinations significantly improved survival (p < 0.001), reduced abnormal behavioral frequencies (p < 0.05), and increased solution intake (p < 0.05) compared to the respective DMT + FLU groups. These results suggest that BPF exerts a protective effect that extends to complex multi-pesticide exposure scenarios. These effects may be associated with antioxidant and detoxification-related pathways, although further biochemical and molecular analyses are required to elucidate the underlying mechanisms.