Synergistic effects of the insecticide flupyradifurone and the entomopathogen Metarhizium brunneum in ants
The global insect decline is largely driven by agricultural pesticides, whose detrimental effects are further amplified by synergistic interactions with other stressors. Whilst there is increasing evidence of adverse impacts of the next-generation insecticide flupyradifurone (FPF), initially marketed as safe for pollinators, its effects on non-pollinators and potential interactions with other stressors remain poorly understood. Here we investigate the impacts of chronic exposure to FPF alone and in combination with the entomopathogenic fungus Metarhizium brunneum in a non-target arthropod: the ant Lasius niger. Our results show that FPF concentrations upwards of 100 ppm increased worker mortality. Furthermore, while sublethal ([≤] 50 ppm) FPF exposure alone did not affect survival, it increased susceptibility to fungal infection, indicating a synergy between the two stressors. This new report of a synergistic interaction between FPF and pathogens raises further concerns about the impact of novel pesticides and could have important implications for insect conservation.