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Paynesville Press - March 10, 2004

Asian ladybugs coming out once again

By Carl Hoffman

The warmer weather recently has brought with it a large number of calls regarding "ladybugs" in the house. The warm days have wakened the insects from their winter slumber in wall voids, attics, and other hiding places, and they are now trying to return to the outside.

For this reason, homeowners may find them in relatively large numbers around windows, patio doors, and other openings to outdoors.

The "ladybug" is the multicolored Asian lady beetle, which is an imported lady beetle that has become a common household pest. These lady beetles are about a third of an inch long that makes them a little larger than the common ladybug. Their 19 black spots on their back and the black "M" on the prothorax, behind their head, can identify them. The background color is variable, ranging from orange to yellow to red or even black. The black spots may be so faint that they appear to have no spots at all.

The lady beetles are very beneficial as predators on aphids and scale insects, but become a pest when they congregate in large numbers around and inside homes. Indoors, these beetles become a nuisance not only by their annoying presence, but also by staining surfaces with a defensive fluid they secrete, giving off a disagreeable odor, and by pinching the skin.

Repeated exposure to dead beetles can cause an allergic reaction in some individuals. They do not feed or reproduce indoors.

Unfortunately, once they get into the home, you can't prevent them from coming out of their hiding places during the winter and spring. The only practical control is to remove them by hand or with a vacuum cleaner. Insecticides are not effective or recommended.

The multicolored lady beetles generally start to enter homes sometime in mid to late September, but this time is variable.

Prevention is the most effective step in controlling lady beetles. Check the outside of your home for spaces and cracks that may allow insects easy entry. Install tight-fitting door seeps or thresholds at the base of all exterior entry doors. Gaps of 1/16 inch or more will permit entry of insects. Seal openings where pipes and wires enter the foundation and siding using caulk cement, urethane expandable foam, steel wool, or other suitable construction sealant. Caulk around windows, doors, chimneys, etc. Repair gaps and tears in window or door screens as well as the screens in roof and soffit vents or bathroom and kitchen fans. Physical exclusion will probably need to be supplemented with an insecticide application. For insecticides to be effective, they must be applied before insects begin to enter the home. Consider applying one of the insecticides labeled for application on the exterior of the home in the fall when you see them congregating in large numbers.

The beetles tend to begin congregating on the first warm, sunny day after a killing frost.

Be sure the product you choose to use is labeled for use on the exterior of buildings. Apply the insecticide according to label directions to soffits, siding, foundation, windowsills, and door thresholds, paying particular attention to the south and west sides where the insects congregate in the largest numbers.

You may consider hiring a professional pest control service as they have access to insecticides that are not available to the public.

(Hoffman is a horticulturist for the University of Minnesota Extension Service.)

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