Interaction of Flupyradifurone and Deltamethrin, Two Pesticides Commonly Used for Plant Pest Control, in Honeybees.

Nowadays, old-generation pesticides are released into ecosystems alongside new formulations, giving rise to pharmacological interactions (additive, synergistic, and antagonistic effects). The aim of this study was to evaluate the impact that simultaneous exposure to DMT and FLU doses has on bee health. Groups of twenty honeybees were housed in cages to compose six macro-groups. One group consisted of experimental replicates treated orally with a toxic dose of deltamenthrin (DMT 21.6 mg/L); two other groups were subjected to the oral administration of two toxic doses of flupyradifurone (FLU 50 mg/L and FLU 100 mg/L); and two other groups were intoxicated with a combination of the two pesticides (DMT 21.6 + FLU 50 and DMT 21.6 + FLU 100). The consequences of the pesticides' interactions were highlighted by measuring and comparing data on survival, food consumption, and abnormal behavior. Generally speaking, antagonism between the two pesticides has been demonstrated. The bees were able to survive for up to three days at the lowest dosage of FLU (50 mg/L), with 46% of the subjects still alive; however, the maximum dose (100 mg/L) caused all treated animals to die as early as the second day. When DMT and FLU 50 were administered together, the group that received DMT alone had a lower survival rate. When comparing the survival rates produced by the DMT and FLU 50 combination to those of the group receiving FLU 50 alone, the same was clearly visible. While there was no statistically significant improvement observed when the survival indices of the DMT and FLU 100 combination were compared to those of the group intoxicated with DMT alone, an improvement in survival indices was observed when these were compared with the group intoxicated with FLU 100 alone.