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 has become very troublesome in many states and provinces, especially
Ontario. Also known as 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.
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.
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.
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.
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
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.
Frequently spraying the beetles that have landed on the side of a house
with soapy water will reduce the population considerably. 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. Be sure
the product you intend to use is labeled for use on the exterior of
buildings. You may wish to consider hiring a professional pest control
service. They have the experience and access to 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