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

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.This work was funded by the project ATLANTIC POSITIVE (Interreg Atlantic Area EAPA_800/2018), and co-funded by the Department of Economic Development and Infrastructures, and the Department of Education (project IT1673-22) of the Basque Government. Aitor Cevidanes was supported by a ‘Ramón y Cajal’ post-doctoral grant RYC2021-033084-I funded by MCIN/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. Omaira de la Hera was supported by a pre-doctoral grant funded by Basque Government (project PUE_2021_1_0008)