Spatial distribution of Vespa velutina-mediated beekeeping risk in France and Germany

The Yellow-legged hornet (Vespa velutina nigrithorax) was accidentally introduced into south-western of France in 2004 and rapidly spread throughout France and neighbouring countries. This insect predator hunts honey bees leading to a hornet-mediated beekeeping risk (HBR) with potential mortality of honey bee colonies and important economic costs. However, the spatial distribution of HBR is not yet assessed and is urgently required to formulate suitable management plans in Western Europe. We conducted a two-year citizen science survey in France and Germany to assess the spatial distribution of (1) the hornet and (2) HBR, and to (3) determine the environmental factors involved. A total of 1678 beekeepers participated in the survey. As expected, the hornet was established throughout the French territory, and was mainly detected near the French border in Germany. We found that HBR was substantially lower in Germany than in France. Temperature had a positive effect on both hornet presence and HBR, whereas distance to the introduction point had a negative effect in both France and Germany. These results suggest that the impact of V. velutina on beekeeping is not homogenous across the invasion range and could be reduced on the eastern front due to the continental climate. Taking into account the spatial variability of HBR could help to formulate regionally adapted management plans to limit the impact of V. velutina on biodiversity, human health and economic sectors.