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
pests such as aphids, scales and others. Adult lady beetles eat 90 to
270 aphids per day. Yet, their tendency
to over-winter 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
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
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
over-wintering sites, is the best way to keep them out. This will also
keep out other unwanted insects such
as wasps, and will save homeowner 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.
Agricultural Research Service