By now, the Asian hornet (Vespa velutina nigrithorax) is well established in Wallonia, and eradicating it remains an illusive prospect. In addition to its impact on human health and biodiversity, this invasive species is having a direct effect on the bee-keeping industry. As a result, it is important to develop a sustainable management strategy that combines various approaches. In addition to neutralising nests, trapping foundresses in spring (March–May) appears to be a promising approach. However, it is controversial, since its attractiveness is limited without pheromones, as well as the potential negative effects on non-targeted species (wild bees, queen bumblebees, etc.) when using drowning traps (wasp traps), among other issues.
The CRA-W perfected a model for a T082 pot trap with a cover in 2023. This was designed using 3D printing. After a series of lab tests, the entry and exit holes were calibrated to the nearest millimetre, so that the pot holds the Asian hornet while allowing other insects to escape. This also prevents European hornets from entering the trap. Production was carried out via plastic injection, in order to ensure the size of the holes and reduce costs.
CRA-W called on beekeepers and municipalities to validate the efficacy of this trap. Of the 6,524 traps distributed throughout Wallonia, we collected observations about capture rates from more than 3,125 traps (48%). In total, more than 815 Asian hornet foundresses were captured with these traps. The low capture rate that was observed in certain areas can be explained by the density of this invasive species still being low, in particular in the east of the region. Furthermore, the bait that was used could also be improved – several participants noted that the grenadine was quickly pillaged by bees, which made the trap less attractive. Studies are ongoing regarding the addition of a repellent to keep bees away (alcohol, yeast, acetic acid, etc.).
In terms of the selectivity of the trap, if we exclude bees, ants and flies that enter and exit the traps without being captured, 67% of the insects captured were Asian hornet foundresses. This selectivity rate is very good compared to other traps mentioned in scientific literature, which have selectivity rates below 30%.
Given this good selectivity rate, this initial trapping campaign validates our development of this technique. A new campaign will be rolled out in 2025, with a few adjustments to improve the attractiveness of the traps, in order to determine the optimal density of traps that need to be deployed around an apiary.
Funding: Walloon Recovery Plan
