Every fall when it starts getting cold outside, many people have visitors. These visitors aren’t friends or family members. They rudely enter homes without being invited inside! These unwelcome guests often arrive just in time for Halloween. They even dress for the occasion. They wear a coat of orange with black dots and appear to have an armor-like shell.
Asian lady beetles are a mixed blessing. They are an effective, natural control for harmful plant pests such as aphids, scale, and others. Adult lady beetles eat 90 to 270 aphids per day. Yet, their tendency to overwinter in homes and buildings (often in large numbers) makes them a nuisance.
Lady beetles do not cause great harm. Unlike termites and carpenter ants, they are not structure-damaging pests. Lady beetles do not chew or bore holes in walls or eat carpet or furniture. They do not lay their eggs in homes.
If agitated or squashed, the beetles may exhibit a defensive reaction known as “reflex bleeding.” A yellow fluid with an unpleasant odor is released from leg joints. This reaction often prevents predators such as birds from eating lady beetles. The fluid may stain walls and fabrics.
Asian lady beetles have become a problem in some regions of the U.S. It is probable that their introduction into new habitats of the U.S. freed these lady beetles from some natural population checks and balances that occur within their native Asian range. It is likely that these natural controls will catch up to the lady beetles in time. This will decrease their booming population.
Asian lady beetles are attracted to lighter colors: whites, grays, yellows. Light-colored houses might serve as “homing beacons.” Once the lady beetles enter the walls of a home through cracks or crevices, they may or may not proceed to the interior. Most stay in the wall spaces. In their search for an exit from wall spaces, lady beetles may enter living areas. Warmer temperatures or lighting in the living areas may attract these active beetles as they search for an exit.
Preventing the lady beetles from entering is the best approach to keeping them from becoming a household nuisance in fall and winter. Caulking exterior cracks and crevices, before the lady bugs seek overwintering sites, is the best way to keep them out. This will also keep out other unwanted insects reduce such as wasps and will save homeowners money on energy costs.
Sweeping and vacuuming are effective methods for removing these lady beetles from living areas. Using insecticides indoors for control of the lady beetles is not typically recommended unless the infestation is very heavy, and professional pest control advice should be sought.