Efficacy of Protein Baits with Fipronil to Control Vespa velutina nigrithorax (Lepeletier, 1836) in Apiaries

SIMPLE SUMMARY: Since the accidental introduction of the yellow-legged hornet (Vespa velutina nigrithorax) at the beginning of 21st century in Europe, it has become a threat to many pollinators, including domestic bees. After its arrival in France in 2004, it quickly spread across the continent, reaching Gipuzkoa (Basque Country) in 2010, where it poses a serious problem for beekeeping. To reduce this problem, various control strategies have been developed, such as the removal of nests or the capture of founder queens in spring. However, these methods have not been effective in reducing the impact of hornets on beekeeping. The use of protein baits with biocides has shown to be an effective method to control invasive wasp populations in natural environments, however, they have not been used to control V. velutina. This study evaluated the efficacy of these baits in reducing the impact of hornets in apiaries. The results have shown that when the presence of hornets in apiaries is high, high-bait consumption is produced, leading to a significant reduction in the number of hornets within 48 h. This reduction lasts for at least two weeks after baiting and allows the honey bees to recover and return to their normal activity. ABSTRACT: The yellow-legged hornet (Vespa velutina nigrithorax), outside its natural range, has become a major threat to domestic bees. Several control methods have been used to fight against V. velutina, but the results achieved are not satisfactory. The use of protein baits with biocides has shown to be an effective method to control invasive wasp populations, but they have not been used to control V. velutina. Thus, the efficacy of protein baits containing fipronil to reduce the presence of hornets in apiaries was evaluated in this study. After laboratory determination of the optimal efficacy of a protein bait at a 0.01% concentration of fipronil, field trials were conducted involving 222 beekeepers. The data reported by the 90 beekeepers who completed the requested questionnaire demonstrated that in the groups of apiaries with the highest pressure of hornets (groups with 10–30 and >30 hornets), there was a significant decrease in the presence of V. velutina, lasting at least two weeks. The reduction in the number of hornets was positively correlated with bait consumption, and bait consumption was positively correlated with the number of hornets present at the time of treatment. Although the method used has shown good efficacy and the concentration of fipronil used was very low; possible negative effects on the environment should also be evaluated.