Testing the selectiveness of electric harps: a mitigation method for reducing Asian hornet impact at beehives.

Abstract

Abstract The Asian hornet ( Vespa velutina ) has rapidly become a source of stress for the beekeeping sector. Several methods have been developed to control its impact and spread, though some of these impose a high risk for native insects. Among these methods are electric harps, which are physical barriers that electrocute hornets passing through two wires powered by a current generator. However, the risk to local fauna of electric harps has not previously been tested. Here we evaluated the selectiveness and risk of damage for local entomofauna of the electric harps in a study carried out over three years and four locations in Girona province (NE Catalonia, Spain). The electric harps showed a high selectiveness, with 82.9% of all insects trapped (3,902 individuals) catalogued as Asian hornets, although this greatly varied over years and locations with values ranging from 20.5% to 94.3%. The risk damage of electric harps for local entomofauna was very low in all surveyed areas and years. Native insects accounted for, as a mean, 1.7% of all insects trapped over the study period (range 0-4.5%). Accordingly, the electric harps imply a low risk for the native European hornet Vespa crabro , since only 0.1% of the captures belonged to that species. Our results suggest that electric harps might be a useful method to reduce predation pressure of the Asian hornet at beehives while imposing a low risk for local entomofauna. The employment of standardised techniques, such as the placement of electric harps, may be useful to assess inter-annual variations or site-specific differences on the predation pressure of the Asian hornet at beehives. Further research should evaluate whether the placement of electric harps improves bee colony survival or vigour parameters (i.e. honey production, amount of brood, pollen, etc.).