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Ladybugs from Asia are currently attacking some houses in Switzerland. Insects come by the thousands, but they are not dangerous to humans.
Asian beetles like to overwinter in droves somewhere in buildings, but where it shouldn’t be too hot.
Photo: Alamy Stock Photo
Ladybugs are actually known as lucky charms. But at the moment, many people feel that it is a real hassle. Because in many places in Switzerland there is a massive invasion of Asian ladybugs. “Thousands of them hang on the walls of houses and often invade apartments to find a suitable place to spend the winter,” says Marc Kenis of the Cabi Institute for Agriculture and Biosciences in Delémont.
This year, the beetles were able to reproduce particularly well because there were so many aphids to eat. The voracious aphid hunter “Harmonia axyridis” was originally bred for biological pest control and was also used successfully in greenhouse crops in some European countries such as France, Belgium and the Netherlands from 1995 onwards. Meanwhile, the ladybug species, which is not native here, has long established itself in the wild. In Switzerland, the first specimens were found in Basel in 2004. The insect has had that ever since. the whole country colonized and is our most common species of ladybug today, its variability is quite large. So your wing can sometimes be lighter, sometimes darker, with more or less dots or even completely monochromatic only in yellow, black or orange.
Although these Asian ladybugs look very different, they all belong to the species “Harmonia axyridis”.
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“Because it was cold here in the last few days and then it got hot again, then they swarm and often move into the same winter lodgings together,” says Kenis. The place should not be too warm, but it should have a temperature of 0-10 degrees Celsius. But you don’t have to fear six-legged animals, as they are harmless to humans. For domestic ladybugs, on the other hand, they are a competitor, since they also eat their eggs when there is a shortage of food.
From beneficial insects to pests
While Asian beetles are still welcome guests in fruit farming, this is not the case in viticulture. “They can have a negative impact on the taste of the wine,” says Christian Linder of Agroscope, who has been researching this type of beetle for years. A single insect per kilogram of Chasselas is enough to reduce the delicacy and fruitiness of the wine. Also, the wine would later smell of rancid oil. Because by pressing the grapes, the insect undergoes stress and releases the chemical alkyl methoxypyrazine. With five insects per kilogram, the quality of pinot noir wines is also greatly reduced.
“This year I have seen a lot of Asian ladybugs on apple trees in Switzerland, but never a large number of them in wine-growing areas,” says Linder. That is why so far there has been no problem. The fact that insects now accumulate en masse in buildings always occurs in autumn. Sometimes it’s less than now, so you don’t notice them as strongly. Both experts advise against the use of insecticides due to their environmental and human toxicity.
“The vacuum cleaner is the best weapon,” says Linder. But because they could crawl, they had to be stored in a tightly sealed plastic bag for a few hours in the freezer, for example, or disposed of with household garbage. I would not recommend squashing or squashing the bugs. Because this not only makes stains unsightly, it would stink too.
