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Lady beetles invade indoors with onset of cooler weather

Lady beetles are well known for their ability to control pestiferous insects such as aphids and mealybugs that plague many types of plants. However, while beneficial, one species, the multi-colored Asian lady beetle, commonly invades homes and other structures with the onset of cooler temperatures during the fall, and can be a real nuisance to the occupants.

This lady beetle is not native to our area, and was brought in from China back in the 1970s and 1980s to control aphids on pecans and other plants. Over time their populations became established and they began spreading out over a wide area.

In their native habitats, as colder weather approached, they would seek out cavities in cliffs and other dry, protected places. The indoors of structures have a similar environment, and the insects can appear, sometimes in large numbers, inside our homes and places of business. They also are attracted to light, and are often found around windows and other light sources in the home.

On warm, sunny days during the early fall the lady beetles will congregate on the outsides of structures that are in sunlight, and then find their way inside. Some years they are present in greater numbers than other years, depending on availability of food and the weather conditions.

The beetles are roughly 1/3 of an inch long, dome shaped and yellow to deep orange in color. It can have up to 19 black spots, and it has a black "W" shape on its thorax, the region of its body right behinds the head. The beetles do not cause any harm to people or the contents of structures. However, when they are disturbed, they emit an acrid odor and secrete a yellowish substance which occasionally causes minor allergic reactions in some people.

What can be done about an Asian lady beetles infestation? The most effective way to get rid of them is by using a vacuum cleaner. Also, sealing up cracks and other points of entry on structures will inhibit, along with other insect pests, their ability to come inside.

Insecticides applications indoors generally are not effective or efficient in controlling the lady beetles. However, applications of insecticides can be made to the exterior of structures in the late summer and fall to reduce pest entry. Professional pest control companies can apply insecticides for control, and homeowners can use products such as Bayer Advanced Powerforce Multi-Insect Killer, Ortho Home Defense Max, Spectracide Triazicide, and others labeled for this type of use. When using chemical insecticides, make sure you follow all label directions and safety precautions.

Unfortunately there is no "silver bullet" available for controlling indoor invasions of the Asian lady beetle. A combination of vacuum cleaning, sealing up entry points on structures, and insecticide applied to the outside of the structure will help control this pest.