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Return of Multicolored Asian Lady Beetle
Return of Multicolored Asian Lady Beetle
Eric J. Rebek, State Extension Specialist for Horticultural Insects
Where are all these ladybugs coming from? This is an all-too-familiar
question heard around Oklahoma the past few days. The ladybugs in
question are of one species, Harmonia axyridis, also
known as
multicolored Asian lady beetle (MALB). In its native Asia, MALB dwells
in trees and crop fields and feeds on soft-bodied insects such as
aphids, scales, and psyllids. This exotic predator was introduced into
the U.S. from Japan by the USDA during the 1960’s through 1990’s in an
attempt to provide control of various agricultural pests. Reportedly,
MALB has done a great job controlling serious pests such as pecan
aphids, leading to significant reductions in insecticide use in
orchards. However, these beetles have a dark side as they can invade
homes and other structures, acting as nuisance pests fall through
spring.
Identification and Life Cycle
Multicolored Asian lady
beetles are oval, strongly convex, and measure about 1/4 inch long,
making them slightly larger than our native lady beetles. These beetles
range in color from light orange to deep red and have a variable number
of black spots (some have none) on the wing covers (elytra) and
individual beetles may live up to three years. There are multiple
generations per year in Oklahoma.
Pest Status
Although MALB
benefits agriculture, beetles seek out shelter during the fall in order
to survive the cold winter months. Beetles are most active on warm,
sunny days following periods of cool weather and are attracted to
illuminated surfaces, especially the southwestern walls of houses and
other buildings. Beetles will find refuge in cracks, crevices, and other
voids that often lead to spaces behind siding, soffits, and inside
attics. Most beetles will remain in these areas until the weather warms
in late winter or early spring, at which time MALB will begin to wander
and seek escape routes to the outdoors. In general, MALB is not harmful,
but beetles can bite and infestations may cause allergic reactions in
sensitive people. It is also important to point out that unlike
termites, MALB does not consume wood and causes no structural damage.
Unlike fleas, roaches, and fruit flies, MALB does not reproduce inside
buildings; it is only overwintering (hibernating). However, MALB is a
nuisance pest because it can accumulate indoors in large numbers and
when disturbed, it produces an unpleasant, acrid odor and yellowish
fluid that can stain curtains and clothing. These ladybugs also bite
readily, although they cause no serious injury to people and pets.
Management
Several tactics can be used to manage MALB, and most infestations are
controlled without the use of insecticides. This is especially important
for those concerned with spraying chemicals in the home. These
management options are classified as preventative measures for keeping
MALB out of dwellings in the first place and remedial measures for
getting rid of existing infestations. Prevention is the first and best
option for managing MALB and other home invaders. Keep MALB and other
insects from getting indoors by sealing all cracks and crevices in outer
walls with mortar or a similar compound. Caulk should be used to seal
openings around windows and doors. As a bonus, this will help reduce
your heating bills. Also, be sure to repair all holes and tears in
window screens. The outward appearance of a structure may also influence
its likelihood of being invaded and, therefore, could be manipulated to
reduce the number of beetles entering a building. There is some debate
about exterior color as it relates to attractiveness to MALB, but
light-colored buildings tend to be more attractive to these beetlesthan
darker buildings. Contrasting light-dark colors, such
as light trim
on a dark base color, may also attract MALB. If sealing exterior cracks
and crevices is impractical, remedial measures including insecticide
sprays may be needed to reduce numbers of beetles entering the home. In
these cases, contact
insecticides can be applied as a barrier
treatment around likely routes of invasion. These treatments usually
work to repel/deter beetles, but some may be killed if they cross the
chemical barrier. On taller structures, this is probably not a job for
the do-it-yourselfer so be sure to hire a professional pest control
operator who has the proper certification, equipment, and training to do
the job right.
Indoor applications of insecticides, including
“bug bombs” and sprays, aren’t generally recommended for use against
MALB because they seldom work, may leave chemical residues on
walls,
furniture, and countertops, and can be hazardous to the health of
people and pets. Therefore, a vacuum cleaner with a hose attachment is a
simple tool that can be used to remove beetles from the interior of the
home. However, I recommend disposing of the vacuum bag or trap
immediately after use, or simply releasing captured beetles outdoors,
assuming routes of entry have been sealed. Otherwise, your captives can
easily find their way out of the bag and re-infest the home.
These
beetles are also attracted to light. Interestingly, a light trap has
been designed by entomologists from the USDA Agricultural Research
Service for capturing MALB indoors. If you’re interested in trying an
alternative to your old Hoover vacuum cleaner for MALB removal, you can
construct a trap following plans found at http://www.ars.usda.gov/is/br/lbeetle/001030.trap.pdf.
References
United States Department of Agriculture - Agricultural Research Service. The Multi-colored Asian Lady Beetle. https://www.ars.usda.gov/oc/br/lbeetle/index/ (Accessed November 4, 2017).
Potter, M.F., R. Bessin, and L. Townsend. Asian Lady Beetle Infestation
of Structures. ENTFACT-416, University of Kentucky, Dept. of
Entomology. https://entomology.ca.uky.edu/ef416
(Accessed November 4, 2017).
Multicolored Asian lady beetle adults, showing variation in color of
elytra (left). Characteristic black “W”- or “M”-shaped marking on
pronotum (right, arrow). Photos by Bill Ree, Texas A&M University, Bugwod.org; and Scott Bauer, USDA-ARS, Bugwood.org, respectively.