As autumn approaches, the adult beetles leave their summer feeding sites in yards, fields and forests for protected places to spend the winter. Unfortunately, homes and buildings are one such location. Swarms of lady beetles typically fly to buildings in September through November depending on locale and weather conditions. In Tennessee, most migration to buildings occurs in October. Beetle flights are heaviest on sunny days following a period of cooler weather, when temperatures return to at least the mid-60s. Consequently, most flight activity occurs in the afternoon and may vary in intensity from one day to the next. Studies have shown that Asian lady beetles are attracted to illuminated surfaces. They tend to congregate on the sunnier, southwest sides of buildings illuminated by afternoon sun. Homes or buildings shaded from afternoon sun are less likely to attract beetles. House color or type of construction (concrete, brick, wood/vinyl siding) is less of a factor for attraction than surface contrast. Contrasting light-dark features tend to attract the beetles — dark shutters on a light background, light shutters on a dark background, windows edged with light-colored trim, gutters and downspouts on contrasting siding, etc. Dwellings near woods or fields are especially prone to infestation, although those in other locations can be infested as well. Once the beetles alight on buildings, they seek out crevices and protected places to spend the winter. They often congregate in attics, wall cavities, and other protected locations. Typical locations include cracks around window and doorframes, behind fascia boards and exterior siding, and within soffits, attics, and wall voids. Structures in poor repair with many cracks and openings are most vulnerable to infestation. As temperatures warm in late winter/early spring, the beetles once again become active. This usually occurs first on the sunnier, southwest side of the building. As awakening beetles attempt to escape to the outdoors, some inadvertently wander inward, emerging from behind baseboards, walls, attics, suspended ceilings, etc. Since lady beetles are attracted to light, they are often seen around windows and light fixtures. Once the beetles are indoors, the easiest way to remove them is with a vacuum cleaner. If you later wish to release the beetles outdoors, place a handkerchief between the vacuum hose and the dust collection bag to act as a trap. A broom can also be used, but is more likely to result in staining when beetles emit their yellowish defensive secretion. Sealing cracks and openings is the most permanent way of preventing lady beetles from entering buildings. The time to do this is in late spring or summer, before the adults begin flying to buildings in search of overwintering sites. Cracks should be sealed around windows, doors, soffits, fascia boards, utility pipes and wires, etc. with caulk or other suitable sealant. Larger holes can be plugged with cement, urethane foam or copper mesh. Repair damaged window screens and install screening behind attic vents, which are common entry points for the beetles. Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors. Gaps of 1/8″ or less will permit entry of lady beetles and other insects. Gaps under sliding glass doors can be sealed with foam weather stripping. These practices will also help prevent entry of flies, wasps, crickets, spiders and other pests. Unfortunately, there is no “quick fix” or easy answer to annual lady beetle invasions. Vacuuming, pest proofing and properly timed exterior insecticide treatments can provide relief but will not prevent entry of every single beetle. For more information about this topic please call the UT Extension office in Cannon County at 563-2554
