Assessing the oral toxicity of acetamiprid, spinosad, cypermethrin, and pyrethrins in the invasive hornet Vespa velutina nigrithorax.

The yellow-legged hornet, Vespa velutina subs. nigrithorax Buysson, 1905, is an invasive species in Europe, posing substantial ecological and economic threats. Its biology and behavior, marked by rapid reproduction and aggressive predation, endanger native insects. This has negative impacts on agriculture, biodiversity, and human safety. Effective control is therefore essential to prevent and minimize its spread and ecological impact. This study assessed the acute oral toxicity of four commercial insecticide formulations containing acetamiprid, spinosad, cypermethrin, and a mixture of natural pyrethrins as active ingredients on V. v. nigrithorax workers. Our findings indicate that acetamiprid and spinosad are the most promising compounds, with acetamiprid inducing rapid mortality at low doses, and spinosad causing both lethal and sublethal effects, potentially disrupting hornet behavior and colony viability. Given that oral exposure generally resulted in higher toxicity than contact exposure, pest control strategies should incorporate multiple exposure pathways. Further investigations are necessary to confirm efficacy under field conditions and to evaluate potential ecological risks to non-target species. Overall, this study provides critical data to improve V. v. nigrithorax control and supports the development of more effective and environmentally sustainable control strategies against this invasive species.