The Multicolored Asian Lady
Beetle
Information Staff Agricultural Research
Service, USDA Beltsville, Maryland
October 30, 2000
The multicolored Asian lady beetle (Harmonia axyridis)
is native to Asia but occurs in many areas of the United States. This
beneficial insect was imported and released as early as 1916 in attempts to
naturally control certain insect pests. But the first populations were not
found in this country until 1988 in Louisiana near the busy port of New
Orleans.
Over the years, federal, state and private entomologists
released the insect at a number of locations. But it was not detected in these
places until some years after it had became established in Louisiana. In
addition, accidental entries have occurred via imported nursery items at ports
in Delaware and South Carolina. Thus, it is uncertain whether the beetle's
establishment resulted from planned releases, accidental entries or both.
Top
Life Cycle
The multicolored Asian lady beetle is similar to other familiar
lady beetles commonly found throughout the United States. Like the familiar
lady beetles, the multicolored Asian lady beetle feeds on insect pests in
orchards and forests but may also occur on row crops and in gardens.
Lady beetles have four distinct life stages: egg, larva, pupa
and adult. The multicolored Asian lady beetle adults begin laying eggs on host
plants in early spring. Eggs hatch in about three to five days, and larvae
begin searching on plants for aphids and other soft-bodied arthropods on which
to feed. Adults and larvae typically feed upon the same prey. Larvae molt four
times, becoming larger after each molt, and enter an immobile pupal stage after
the last molt.
After several days, the adult beetle emerges from the pupal
case. Development time from egg to adult requires about 15-25 days depending on
temperature and food availability. Later in the fall, near the time of killing
frosts, the adult beetles seek shelter to spend the winter.
Top
Mixed Blessing
This variably colored and spotted lady beetle is an effective,
natural control for harmful plant pests such as aphids, scale and other
soft-bodied arthropods. Still, its tendency to overwinter in homes and other
buildings, sometimes in large numbers, may make them a nuisance to many
persons.
If agitated or squashed, the beetles may exhibit a defensive
reaction known as reflex bleeding, in which a yellow fluid with an
unpleasant odor is released from leg joints. This reaction generally prevents
predators, such a birds, from eating lady beetles. But in the home, the fluid
may stain walls and fabrics.
Multicolored Asian lady beetles have become a problem in some
regions of the United States. It is probable that their introduction into new
habitats in the United States 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
and curtail their booming population. Additionally, a period of time may be
required for checks and balances of our native lady beetles to adapt to this
newcomer.
Multicolored Asian lady beetles are beneficial insects. Their
natural control of aphids in pecan orchards has decreased insecticide use
against those pests. Additionally, they have controlled aphids on some
ornamental plants. Still, these lady beetles are unwelcome guests for many
homeowners.
Top
What These Insects DoAnd Don't Do
Lady beetles are not structure-damaging pests, unlike insects
such as termites and carpenter ants. Lady beetles do not chew or bore holes in
walls or eat carpet or furniture. They do not lay their eggs in homes.
Multicolored Asian lady beetles are attracted to lighter colors:
whites, grays, yellows. So, light-colored houses, especially on hillsides in
forested areas, might serve as homing beacons.
Once the lady beetles enter the walls of a building through
cracks and crevices, they may or may not proceed to the interior of the
building. Most stay in the wall spaces.
During warm days of late winter and early spring, overwintering
beetles in a wall space may become active. In their search for an exit, they
may enter the home's living areas and become a nuisance. Warmer temperatures or
lighting in the living areas may attract these active beetles as they search
for an exit.
Top
Prevention and Control
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 beetles seek overwintering
sites-- is the best way to keep them out. This will also keep out other
unwanted insects such as wasps, and will save homeowners money on energy
costs.
Lady beetles that enter wall spaces in the fall may remain
there, without entering living areas, until they depart in spring to search for
food. But some may become active on warm days in late winter or early spring
and move into living areas.
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.
Lady beetles that enter living areas are typically attracted to
light. A trap for indoor use that uses light to attract lady beetles and other
flying insects was developed by entomologist Louis Tedders (retired) and
colleagues at the Southeastern Fruit and Tree Nut Research Laboratory,
Agricultural Research Service, Byron, Ga. The insects become trapped in a
removable bag. Use of insecticide is unnecessary. A patent application was
filed, but a patent was not granted.
Detailed technical instructions and diagrams for
constructing the trap are available on an ARS web site in PDF (portable
document format) at:
http://www.ars.usda.gov/is/br/lbeetle/001030.trap.pdf
Top
For more information
You can request additional information and
guidance from your state and local Cooperative Extension agents and scientists.
Check your local directory for the Cooperative Extension telephone number.
On the Internet, you can find Cooperative
Extension contacts at state land-grant universities by following the state
links at the "State
Partners" page of the web site of the USDA Cooperative State Research,
Education, and Extension Service. The "State Partners" page is at
http://www.reeusda.gov/1700/statepartners/usa.htm.
A March 1995
story in Agricultural Research
magazine discusses Harmonia and several other non-native lady beetle
species.
An ARS scientific research contact is Ted E.
Cottrell of the ARS
Southeastern
Fruit and Tree Nut Research Laboratory, Byron, Ga.,
tcottrell@saa.ars.usda.gov.
|