Lady beetles are known to be beneficial insects and, some say, good luck. But many people panic at the sight of the small, reddish colored beetles covering the outside of their homes each fall, especially when they start making their way inside.
There’s no need to be alarmed about these nuisance pests, say specialists from the Pennsylvania IPM Program. The beetles, called multicolored Asian lady beetles, are native of eastern Asia and came to North America two ways: by accident on imported freight from Asia; and introduced on purpose by the U.S. Department of Agriculture years ago as a biological control agent for crop pests such as aphids and scale insects. These insects are tremendously beneficial in gardens and farm fields during the summer months. They are slightly larger than native lady beetles, measuring 0.2 to 0.3 inches long. They vary in color from yellow to red and may (or may not) have black spots on their wing covers.
The beetles become nuisance pests in early October during sunny, warm afternoons after a cold snap. Lyn Garling, education specialist for the PA IPM Program explains that the cold snap tells the beetles they had better get busy and find a good place to hide for the winter. “Like all insects, they need warmth to move, so they gather on the south sides of houses, sheds and other buildings looking for warmth. Once they get warm, they are on the go. If there are openings into your home, it’s not uncommon for hundreds or even thousands of beetles to make their way onto walls, ceilings and attics. Their tendency is to go up into the attic and ball up to wait out the winter. However, they might get stuck in the kitchen and drive you crazy crawling on windows or falling in your soup.”
If disturbed, they can give off a stinky, yellow defensive chemical. “Most people are only annoyed by their odor and the spotting that can occur on walls and ceilings, but some individuals can experience an allergic reaction to these chemicals,” says Garling. “In general, the beetles are harmless and they do not carry diseases. While over wintering, they do not feed or reproduce.”
So, how do you deal with these pests? According to Michelle Niedermeier, PA IPM Community IPM Coordinator, the best offense is a good defense. “The first step is to keep them out. Take a look around your house and caulk cracks around windows, doors, siding, utility pipes and other openings.” Niedermeier explains. “Damaged screens on doors and windows should be repaired or replaced. Attics, fireplace chimneys, and exhaust vents should be covered with number 20 (or smaller) screen mesh.”
If you still find the beetles in the home, Niedermeier says don’t use an insecticide to get rid of them. “Indoor use of aerosol insecticides presents a respiratory health hazard, especially with the house locked up tight as it typically is preparing for winter. Besides, it won’t prevent new beetles from coming in.” Rather, watch their behavior and outsmart them. They will fly to windows and crawl up them during the day. “There are sticky fly strips made to fit on edges of window panes that can trap the beetles and be thrown away. Try to avoid handling them directly to keep them from exuding odor. If your really have lots of beetles, regular vacuuming to collect them works really well; just make sure to empty the bag after each vacuuming,” Niedermeier says.
Black (ultra-violet) light traps may also provide relief from beetles flying or crawling around the interior of homes. These traps are available for purchase from pest control companies and pest control supply companies. “If you decide to buy a trap, get one that has a sticky glueboard trap to collect the beetles. The glueboards can be replaced when they become full of beetles,” explains Niedermeier.
It’s important to seal cracks and openings in your home before lady beetles find their way inside. The following pest-proofing measures can help:
- Seal cracks around windows, doors, siding, utility pipes, and other openings. Use weather stripping or a good quality silicone or silicone-latex caulk. Larger gaps can be sealed with urethane foam, glass wool or stainless steel wool, etc.
- Install tight fitting door sweeps or thresholds at all exterior entry doors.
- Around garage doors, install a rubber seal rather than vinyl, which seals poorly in cold weather.
- Install insect screening (20-mesh maximum) over attic and exhaust vents to prevent lady beetle entry.
- Replace and repair damaged door and window screens.
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