Lady beetles are beneficial because they feed on harmful insects such as aphids, that can damage plants in gardens and landscapes. However, one lady beetle species, the multicolored Asian lady beetle, Harmonia axyridis, has become very troublesome in Minnesota. Also known as Halloween lady beetles, Japanese lady beetle, and Asian lady beetle, these insects cluster around buildings in large numbers during fall as they search for protected sites to overwinter.

History
The multicolored Asian lady beetle is a native of eastern Asia. These insects were released in California by the U.S. Department of Agriculture in 1916 and in 1964 -1965 for biological control of pecan aphids. They were also released in the late 1970's and early 1980's in Connecticut, Delaware, Georgia, Louisiana, Maine, Maryland, Mississippi, Ohio, Pennsylvania, and Washington. However, the lady beetles did not appear to become established from these releases.

In 1988 a population of multicolored Asian beetles was found in Louisiana, apparently the result of an accidental introduction from a freighter in New Orleans. These lady beetles spread quickly throughout the southern and eastern United States. No one knows whether their presence today is due to deliberate releases, accidental introductions, or both.

Although multicolored Asian lady beetles were never released in Minnesota, they moved into the state from nearby areas. They were first sighted in Minnesota in 1995. The first report of major infestations around buildings occurred in 1998, and by 2000 the insect had generally dispersed throughout the state.

Identification
The multicolored lady beetle looks very similar to other lady beetles but is generally larger, about 1/3-inch long. Its appearance is quite variable, ranging from orange to yellow to red or even black. This beetle typically has 19 black spots on its wing covers. These spots vary from being relatively thick to being no more than faint traces of spots. Some multicolored Asian lady beetles have no spots at all. There may be fewer spots present when they are faint. There is a prominent black 'M' shape behind the head in most specimens. This 'M' can look thick, thin or even broken in appearance.

Habits
In their native Asian habitat, multicolored Asian lady beetles feed primarily on aphids and other small, soft-bodied insects found in trees. In the U.S., they feed on insects in trees as well as pests in row crops and gardens. In Asia, these insects are usually found congregating in large numbers on white colored cliffs each fall, to overwinter. Lacking cliffs In the U.S., these lady beetles are often found on the west and south sides of tall or prominent, light-colored buildings in mid- to late October.

From the exteriors of buildings they crawl under siding and roofing and into cracks and gaps in foundations and around windows, doors and other openings. They may continue to move into the living areas of homes or they may spend the winter inside the attic or wall voids. Mild, sunny winter days can wake these dormant insects. They become active and move into the home's living quarters. Once spring arrives, the remaining lady beetles wake up and attempt to move outdoors. Not all succeed and many are trapped indoors. Multicolored Asian lady beetles do not reproduce indoors.

Importance
Although multicolored Asian lady beetles can be a nuisance when they occur in large numbers, they do not damage homes or other property. These lady beetles cannot sting and they do not carry disease. They can pinch the skin and cause minor, short-lived discomfort. They can secrete a strong smelling yellowish liquid from the joints of their legs, a process called reflex bleeding. They use this to discourage predators or at other times when they are stressed. This liquid can also stain light colored surfaces. Repeated exposure to dead lady beetles can cause an allergic reaction in some individuals.

Management
Prevention is the most effective step in managing lady beetles. Check the outside of your home for spaces and cracks that may allow insects easy entry. Make any necessary repairs by the end of September.

Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors. Gaps of 1/16 inch or more will permit entry of insects. Seal openings where pipes and wires enter the foundation and siding, for instance, around outdoor faucets, receptacles, gas meters, clothes dryer vents, and telephone/cable TV wires. Holes can be plugged with caulk, cement, urethane expandable foam, steel wool, copper mesh, or other suitable construction sealant. Caulk around windows, doors, chimneys and fascia boards, etc. using a high quality silicone or acrylic latex caulk. Repair gaps and tears in window and door screens. Repair screens in roof and soffit vents, and in bathroom and kitchen fans. Keep siding, eaves and soffits in good repair, replacing damaged areas if necessary, to keep the exterior walls as insect-proof as possible.

Physical exclusion can be supplemented with a residual insecticide barrier. For insecticides to be effective, they must be applied before insects begin to enter buildings, which is early- to mid-October for multicolored Asian beetles. Common examples of insecticides available to the public include those containing bifenthrin, cyfluthrin, cypermethrin, deltamethrin, or permethrin. Be sure the product you intend to use is labeled for use on the exterior of buildings. Apply the insecticide according to label directions to siding, foundation, windowsills, and door thresholds, paying particular attention to the south and west sides where the insects are most common. You may wish to consider hiring a professional pest control service. They have the experience and access to additional residual insecticides to control lady beetles effectively.

Remove lady beetles found indoors with a broom or vacuum. Indoor insecticide sprays are of very limited benefit. Once lady beetles move into wall voids there is no practical control to prevent them from emerging later during winter or spring. The only control is to remove them as they are seen.

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