Asian hornets have been spreading across Europe for years, causing concern among experts. The species introduced from Southeast Asia also feeds on bees and endangers their existence. With tracking transmitters, helpers are now able to track down their nests.
They lurk in front of beehives and intercept returning honey bees: Asian hornets are worrying beekeepers in Baden-Württemberg and other regions of Germany. The species, introduced from Southeast Asia, likes to besiege beehives, and sometimes the hornets even force their way into the hives, says Kristin Krewenka, Managing Director of the Baden Beekeepers Association. "We are very concerned." Due to the hot and dry summer last year, the animals would probably have multiplied considerably. As early as 2022, sightings would have almost tripled compared to the previous year.
Although native hornets (Vespa crabro) also like to hunt bees, the Asian hornet (Vespa velutina) does this much more frequently and more specifically. The influence on the native insect world has not been studied well enough to be able to make reliable statements, says Sabine Holmgeirsson, wild bee officer at the Naturschutzbund (Nabu) Baden-Württemberg. According to Nabu, the introduced species was first detected in Germany in 2014. France - where the first finding was made in 2004 - has already settled in large parts, and there are also increasing reports in other European countries. In Baden-Württemberg, the invasive species Krewenka is particularly widespread around Heidelberg and Karlsruhe. Last year it was also detected in Tübingen and in the administrative district of Stuttgart. According to Nabu, there were also reports from Hesse and NRW.
Asian hornets are slightly smaller than native hornets, but their colonies can number thousands. More than 15 nests were counted in Baden-Württemberg in 2022, says Benjamin Waldmann, consultant for invasive species at the Baden-Württemberg State Ministry for the Environment. "But we assume that the number of unreported cases is high." The balloon-shaped nests are difficult to find, they are often hidden in treetops. The hornets are supposed to betray themselves with tracking transmitters: helpers lie in wait for them near beehives with nets and catch individual animals to which they attach tiny transmitters. "The idea is that we can follow the hornets to the nest in this way," says Waldmann. The method has already been successful several times.
If a nest is found at a great height, a fire brigade turntable ladder is used, explains the speaker. The opening of the nest is closed with a foam extinguisher, then the corresponding branch is sawn off. The nest is then placed in a box and frozen. The hornets die from the cold. So far, beekeepers have not suffered any major damage from the invasive species, according to the Baden Beekeepers' Association. But the problem must be considered in the long term. In addition, the hornets also tasted grapes and fruit - in southern Europe this is already a problem for wine and fruit growers. The invasive species does not pose a greater direct threat to humans than its native relatives. According to the experts, they behave peacefully and defensively - but hitting them or approaching their nest is not a good idea with these hornets either. "Then there is a risk of being bitten," says Waldmann.
The Asian hornet is not to be confused with the Asian giant hornet (Vespa mandarinia). These insects, which are up to five centimeters in size and originally found in East and Southeast Asia, are spreading to the USA, among other places, and are feared enemies of bees. Their sting can be dangerous to humans due to allergic reactions. The species does not occur in Germany.
(This article was first published on Sunday, March 05, 2023.)