Q. I have
had ladybugs in my house before, and usually just catch the ones I
see and put them outside. But this year the lady bugs have been unbelievable!
Why so many, and do you have any better recommendations for getting
rid of these lady beetles?
Growing conditions this summer resulted in lush plant growth that
created a favorable environment for insects such as aphids to
thrive. The high aphid population meant a plentiful food supply for
multicolored Asian lady beetles (Harmonia axyridis), so their
rate went up as well. Multicolored Asian lady beetles often become
unwelcome invaders in homes as they look for sheltered locations to
usually begin massing on the sunniest sides of buildings after the
first killing frost, looking for cracks and crevices to gain entry.
In their native eastern Asia, they mass on south-facing cliffs where
they push into rock crevices for shelter from winter cold.
Overwintering lady beetles become active inside your house on sunny
days in February and March, when they will congregate on windows and
doors looking for a way out of your house.
These lady beetles were intentionally introduced into the United
States as a biological control agent for aphids and scale insects.
They were released in Pennsylvania in 1978 and 1981, but
overwintering populations were not reported until 1993. It is
thought that those releases failed to establish, and that the
multicolored Asian lady beetles we have seen since 1993 were
accidentally introduced in New Orleans from an Asian ship.
Although they do not sting, carry diseases or damage wood, fiber or
foodstuffs, they can be annoying when they take up residence in
large numbers. They do occasionally bite, and are equipped with a
foul-smelling defensive chemical they emit when threatened or
crushed that can stain surfaces. Some people report sinus irritation
and mild dermatitis after handling the insects or after being
exposed to large populations of them.
The best way to deal with these nuisance pests is to keep them out
of your house as much as possible. Screen all openings and attic
vents with number 20 or smaller mesh. Make sure your window screens
do not have holes in them and that the weather-stripping on doors
fits snugly. Caulk all cracks around window and doorframes, openings
where utility pipes and wires enter your house, and any other
opening to the outdoors.
You can reduce multicolored Asian lady beetle congregations outdoors
with sprays of synthetic pyrethroids, including the active
ingredients cyfluthrin, deltamethrin, lambda-cyhalothrin, sumithrin
or tralomethrin. A licensed structural pest control operator should
apply these products in late September or early October, just before
insects begin to congregate. Since many pesticides are broken down
by exposure to sunlight, the residual effect of such applications
may not last more than a week.
Do not spray these products inside your home. They will not prevent
insects from coming in through unsealed crevices. Also, even though
these products may kill many insects in wall voids, their decaying
bodies may attract carpet beetles that will damage wool fabrics,
grain products of all kinds, pet food, and many other food items.
VACUUM THEM UP!
Use a vacuum to remove the beetles, and change the bag or empty the
canister frequently. You can also trap them with black light traps
that have sticky glue boards attached. These traps are available
from pest control professionals and pest control supply companies.
They are not the same as “bug zappers;” those should never be used
inside your home. The sticky light traps are most effective at night
when there are no competing light sources.
In addition to multicolored Asian lady beetle, other nuisance
insects that take up residence for the winter include boxelder bugs,
brown marmorated stink bugs and leaf-footed bugs. The same control
options are recommended for them.
Bees in the Garden