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The Fall Invasion of the Asian Lady Beetle

By Marie Woodward, UConn Home & Garden Education Center

multi-colored Asian ladybeetle on a flower

As the leaves change color and the weather turns colder, many people look forward to the beauty and coziness of autumn. However, one uninvited guest often accompanies the season: the Asian lady beetle. This insect, scientifically known as Harmonia axyridis, can be a nuisance to homeowners as it seeks shelter in warm buildings during the fall months.

The Asian lady beetle is native to eastern Asia but was introduced to the United States and other parts of the world in the early 20th century as a biological control agent for aphids and other pests. While they are highly effective at controlling these pests in the gardens and crops, their rapid spread and tendency to congregate in large numbers have caused problems for homeowners.

These beetles are easily recognizable by their orange to reddish-brown coloration, small black spots on their wing covers, and distinctive M-shaped marking behind their head. Their size ranges from 5-8mm in length. They have six short legs and two antennae.

During the fall, the Asian lady beetle seeks protected locations to spend the winter. They gather in large groups, often on the sunny side of buildings, before ultimately finding their way into homes and other structures through cracks and gaps. It is not uncommon to find them gathered in attics, wall voids, or other quiet, undisturbed areas.

Once inside, these beetles can become a nuisance due to their sheer numbers and tendency to release a yellowish, foul-smelling liquid when disturbed. This liquid can stain walls, fabrics, and other surfaces, and may cause allergic reactions in some individuals. Additionally, some people find the beetles’ scent unpleasant or even nauseating.

Prevention is key to avoiding an Asian lady beetle infestation. Sealing entry points, such as cracks around windows, doors and utility openings, can significantly reduce the likelihood of an invasion. Additionally, keeping exterior lights off at night and planting trees or shrubs away from the house can reduce the attractiveness of your home to these insects.

If beetles have already found their way inside, using a vacuum cleaner is the best means of removal. However, be sure to dispose of the vacuum bag or empty the canister outdoors immediately to prevent the beetles from returning back into your home. Alternatively, insect light traps or sticky traps can help capture and remove beetles.

It’s essential to remember that while the Asian lady beetle can be a nuisance, it is not a significant threat to your home or your health. Taking proactive measures to prevent their entry and managing their presence can significantly reduce the annoyance caused by these uninvited guests.

As the fall season arrives, keep in mind the potential for Asian lady beetles to seek shelter in your home. By understanding their behavior and implementing preventive measures, you can enjoy the beauty and warmth of autumn without the invasion of these pesky insects.

If you have questions about Asian lady beetles or other gardening topics, contact the UConn Home & Garden Education at (877) 486-6271 or www.homegarden.cahnr,uconn.edu or your local Cooperative Extension Center.