Bad news for bees – the Asian hornet has reappeared in western Switzerland – knowledge

Bad news for the bees: the Asian hornet is spreading again in Switzerland. Their great appetite threatens bee diversity.

Autumn is here and with it peace for the bees. In the warm months, the entrances to the beehives still resembled a battle zone. Several hornets hover in front of it and watch out for the honey bees that return with food. “Once a hornet has caught a bee, it rips off its head and tail, because the hornet is only interested in the chest, where the flight muscles are located,” explains biologist Daniel Cherix from the University of Lausanne. The attacks mean that the bees no longer dare to leave the box. “If this happens over several days, the people starve,” he specifies.

These hornets have a great appetite. It eats much more than the European hornet, so many bees that it poses a threat to populations. Cherix has already seen hornet colonies consisting of 13,000 individuals. That is around ten times more than that of the European species.

Rare wild bee species are also threatened

The Asian hornets not only hunt honey bees, but all bees, including rare wild bee species. This is the only way for the hornets to obtain enough food to raise the new queens and drones. “This appetite reduces the biodiversity of wild bees, which is essential for pollinating some flowering plants,” adds Cherix. Because of this, some plants may disappear.

The biologist has often observed how the hornets hunt. He is one of the few specialists in Switzerland who is familiar with the immigrant insect and has been commissioned by the federal government to find and eradicate the animals. Beekeepers should not pursue the predator themselves because they would catch many other species of insects with their traps and would also endanger local insect diversity.

Imported from China

The Asian hornet first arrived in Europe in the winter of 2004 in south-west France. Three young queens were in pots for bonsai from China. Two of them died, one escaped. Since then, the species has spread throughout France and neighboring countries. It first appeared in Switzerland in 2017, then again in 2020 and hasn’t disappeared since then. Ten nests have already been discovered this year and most of them destroyed, in the cantons of Geneva, Jura, Vaud, Friborg and Baselland.

Cherix fights the hornets by finding their nests and removing the brood. To do this, he first catches a hornet and hangs a tiny tracking device around its waist. Using a receiver, Cherix captures the transmitter’s signal and tracks down the hornet, which eventually leads him to its nest. The pear-shaped nests are always hidden high up in the canopy of tall trees, which makes destroying and removing the nest very laborious. “It takes people who can climb,” says Cherix and laughs.

Together against the hornet

A colony produces up to 500 new queens, all of which start new colonies the following spring. So the public should help. If someone discovers an Asian hornet, this should be reported to Apiservice, the advice and competence center for Swiss beekeepers. So it could be possible that the hornet does not stay. But the bees, without which many flowering plants would not survive.