MULTICOLORED ASIAN
LADY BEETLES
Phil Pellitteri
- UW Insect Diagnostic Lab
It has become common
to see large number of lady beetles clustered around homes and
other buildings during the fall. The species is native to eastern
Asia and is called the Multicolored Asian Lady Beetle. Lady beetles
are usually considered beneficial insects, but this species can
congregate by the thousands on the sides of buildings and if given
the opportunity, move inside. Fortunately, they are harmless,
but repeated exposure has caused allergic reactions in a small
number of people. This ladybird beetle, Harmonia axyridis,
has only been recorded in numbers in Wisconsin since 1994. It
is not know exactly how it became established in the United States,
but there have been numerous attempts (from 1916 until 1985) to
establish this species as a biological control agent for pecan
aphids. The Asian lady beetle is an important predator of scale
and aphid pests on trees in Asia. The first specimens recovered
in the US were collected in Louisiana during 1988. Since then
the beetle has increased its distribution to include all states
east of the Mississippi.
These oval, convex,
1/3 inch beetles are pale orange in color with 19 black spots
on the wing covers. The 19 spots are arranged as a row of five
spots, followed by two rows of six spots, and a fourth row of
two spots. Some of these beetles are either without these spots
or may only have traces of 4 to 6 spots on the wing covers. In
Asia, this beetle occurs in at least 100 different color forms
including black forms with orange spots.
The ladybird beetles
congregate on homes in search of over wintering sites. They usually
select the west or southwest side of buildings for initial congregation
sites, but many leave on their own by nightfall. If is likely
these beetles will move into leaf litter, underneath boards or
logs, or other protected areas after the first frost.
As usual, prevention
is the key to keeping this ladybird beetle from getting into homes.
Make certain that cracks along windows and doors are tight fitting.
Ventilation openings in attics should be screened or sealed as
appropriate.
One of the best ways
to limit unwanted intrusion by insects is to deny them entry -
a procedure known as pest proofing. Many pests seek refuge in
homes and other buildings in response to changes in weather, such
as extended periods of rain or drought, or the onset of cooler
temperatures in autumn. Taking steps to block their entry before
they end up inside can greatly reduce the changes of future sights.
Equipment and materials mentioned can be purchased at most home
improvement or hardware stores.
- Install door sweeps or thresholds at the base of all exterior
entry doors. While lying on the floor, check for light filtering
under doors. Gaps of 1/16 inch or less will permit entry. Apply
caulk (see #3) along bottom outside edge and sides of door thresholds
to exclude ants and other small insects. Gaps under sliding
glass doors can be sealed by lining the bottom track with 1/2
to 3/4 inch-wide foam weather stripping. Repair gaps and tears
in window and door screens.
- Seal utility openings where pipes and wires enter the foundation
and sliding around outdoor faucets, gas meters, clothes dryer
vents, and telephone/cable TV wires. These are common entry
points for such pests as rodents, ants, spiders and yellowjackets
. Holes can be plugged with caulk, cement, urethane expandable
foam, steel wool, copper mesh (Stuffit), or other suitable sealant.
- Caulk cracks around windows, doors, fascia boards, etc. Use
a good quality silicone or acrylic latex caulk. Although somewhat
less flexible than pure silicone, latex-type caulks clean up
easily with water and can be painted. Caulks that dry clear
are often easier to use than pigmented caulks since they don't
show mistakes.
- If the lady beetles cannot be built out there are a number
of sprays that can be applied to the outside of the structure
during mid-October to kill the beetles before they get in. The
most effective sprays are various synthetic pyrethroids
such as permethrin, cyfluthri, deltamethrin and lamda-cyalothrin.
Concentrate along doors, windows and the south and west sides
of the structure. You may wish to hire a professional pest control
company for application.
When all else fails,
a vacuum cleaner or broom is often the best response once the
beetles have come indoors. Lady beetles defend themselves by bleeding
from their joints. If handled too roughly they can stain carpets, outside.
There is no effective chemical for use indoors. Control is possible
by using Pyrethrim sprays on outside walls in fall when these
beetles start to congregate.
For more information
contact the Marathon County UW-Extension
office.
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