Bee Number 9

The Asian Hornet: Luring the foe into a trap

The Asian hornet is fiercely territorial and will defend a source of food, such as an apiary, against other hornets. It may not seem it at the time to the beekeeper, but this is in fact a weakness because it at least means you are only dealing with one nest at a time, although if a nest is destroyed the vacuum is quickly filled by hornets from another nest.

Dismissed by some researchers as making little impact on hornet numbers, the fact is that summer trapping can catch significant numbers of hornets and that can have an impact on the hornet’s nest development, as well as mitigating attacks on hives.

This means that the ‘catch rate’ has to be sufficient to impact on the hornet colony’s ability to replace losses. If a hornet colony reaches a peak population of typically 1,500 workers in the autumn and the hornet’s life-cycle at this time is around thirty days from emergence then a daily catch rate of, say, ten might make a difference in early August, but no difference at all in late September. The key here is to monitor the effectiveness of your bait and to deploy sufficient traps until predation is reduced to the level at which your bees will fly.

The trap is the same as for spring trapping of founder queens but the recommended bait is now protein-based. The idea is to offer the protein to the hornet workers as an ‘easier’ source of food than the honey bee. Shrimps and mashed fish are a common choice, but I suggest that although you should certainly put such a bait in some of your traps, do be aware that it smells and it needs to be changed much more frequently than the sweet carbohydrate bait, perhaps as frequently as every three days. Furthermore, I would be cautious about abandoning the sweet bait entirely. The argument is that the hornet workers want protein to take back to the larvae in the nest, where they get a sweet reward from the larvae. So why not give the hornet its reward earlier in the process; in a trap.

As well as the selective traps located out in the apiary at 1.5m in trees, in the sun, you should deploy additional traps just in front of but between the hives at entrance level. These need not be selective as the zone in front of the hives during peak predation is hostile to any non-target species, so a simple trap will suffice but should not be baited with anything attractive to bees. Even if the ‘piege artisanal’ is not judged to be as efficient as some of the more expensive alternatives, it is cheap and easy to make. So never mind the lower efficiency, make up for it in numbers.

Tests by the INRA, the Institut National de la Recherché Agronomique, has found that hornet workers are partial to a summer bait based on wax operculum; i.e. wax cappings melted and mixed with honey, to which yeast is added and the mix allowed to ferment for three days. If you do not want to make up a wax operculum bait, the sweet bait is still attractive and many French just continue with the ‘French cocktail’ of biere brune, cassis and vin blanc, which is much easier to make and manage (described above).