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Asian ladybugs target homes after first frost

Asian ladybugs start to seek shelter during sunny days following the season’s first hard frost. (Duluth News Tribune file)

Multicolored Asian ladybeetles are not native to Wisconsin. Although there are numerous native ladybugs in the state, only the Asian variety are known to aggregate in buildings in the fall and become nuisances.

In their native range, multicolored Asian ladybeetles seek out small caves and holes in limestone walls in which to spend the winter months. In Wisconsin, they look for houses, garages, sheds, holes in trees, firewood piles — anywhere where there are nooks and crannies in which to hide.

Multicolored Asian ladybugs start to seek winter shelter during sunny days following the season's first hard frost. Depending on location, this generally occurs in early to mid-October. While overwintering, they do not feed or reproduce.

Sealing around doors and windows, external vents, bases of buildings and siding can keep ladybugs out of buildings. Insecticidal sprays can also be applied to the outside of buildings as repellents.

Depending on the product's residual effect and how long warm weather lingers, a second application may be necessary. Consider testing an out-of-sight area to make sure the insecticide does not cause any damage to siding or paint. Always follow label directions when applying pesticides.

Once inside, multicolored Asian ladybeetles tend to congregate in windows during the day. Removing them with a vacuum cleaner is effective when done on a daily basis. Vacuum bags should be emptied each time to prevent foul odors as ladybugs emit foul-smelling secretions when disturbed. The beetles may also be drowned in soapy water.

Asian ladybeetles might bite when disturbed, but they are not overly aggressive.

Although they can be annoying in wintertime, Asian ladybugs provide some positive benefits the rest of the year. During the growing season, multicolored Asian ladybeetle adults and larvae feast on aphids and scale insects in gardens, agricultural fields and forests.

During the fall, as aphid populations dwindle, ladybugs may feed on rotting or damaged fruit.

Linda Williams is a forest health specialist with the Wisconsin Department of Natural Resources.