Bee Number 2

The Asian Hornet: Spring trapping

The first and most urgent task is to get traps out early in the year. The purpose of trapping in the early spring is two-fold. First, it is to detect the presence of V. velutina thus giving the National Bee Unit (NBU) time to assess the overall situation, to gather and to deploy resources in the most effective way. Second, it is to trap ‘founder queens’ that would otherwise go on to found a nest that in turn will produce hundreds of ‘sexual’, male and female hornets that will mate before the females go into hibernation for the winter. Even though the vast majority of those females will perish over winter, enough will survive to found several more nests in the following season.

Spring queen trapping is controversial. Beekeeper associations in France promote it and there is much evidence from beekeepers that predation is reduced in areas where it is widely practised. Researchers and entomologists, however, are concerned because the former doubt its effectiveness and the latter fear for the effect it has on the local entomofauna through collateral damage, i.e. the trapping of non-target species. Unfortunately, we have no choice but to trap. If we do not trap then we rely on the single measure of finding nests in the summer/early autumn and that has been proved in France not to work. We have a one-off opportunity to stop V. velutina i.e. before it has established a foothold.

No doubt recognizing the concerns of entomologists, the NBU initially designed a version of the simple French ‘piege artisan’ trap that incorporated 7mm diameter holes in the entrance funnel to allow V. velutina to enter, but to exclude larger insects such as the European hornet and 5.5mm diameter holes in the trap itself to allow smaller non-target species to escape. However, tests have shown that traps with restrictions on the entrance funnel are far less efficient in trapping V. velutina than traps with a wider or unrestricted entrance and so that initial filter has had to be abandoned. Described below is a modified version of the latest NBU trap in which larger non-target species such as the European hornet, Vespa crabro, are held in an upper chamber for later release. The critical difference is that this trap lets them both in and leaves selectivity to be managed later.