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Paynesville Press - Sept. 21, 2005

Asian beetles will be back, act now

By Michael Jacobson

Ladybugs have been absent from in and around our homes all summer and have been busy eating aphids in soybean fields, cornfields, and other plant areas. Unfortunately, it will soon be time for them to start congregating on the outside of our homes, and we may see large numbers of them on sunny days.

Once they gather on the outside of the home it's time to use some preventative measures, or we will soon find the pesky insects on the inside. Typically, we can expect them to begin to congregate on the south and west sides of homes on the first sunny day following a hard frost.

The "ladybug" is the multicolored Asian lady beetle, which is an imported lady beetle that has become a common household pest. 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.

These beetles become a nuisance not only by their 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.

Prevention is the most effective step in controlling lady beetles, and the time to act is now! Seal as many openings as possible that will allow lady beetles into your home. Check the outside of your home for spaces and cracks that may allow insects easy entry. Install tight-fitting door sweeps 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, fascia boards, etc., using a high quality silicone or acrylic latex caulk. Repair gaps and tears in window or door screens as well as the screens in roof and soffit vents or bathroom and kitchen fans.

This should be done by the end of September, before the lady beetles start to enter homes.

Physical exclusion will probably need to be supplemented with application of a residual insecticide. For insecticides to be effective, they must be applied before insects begin to enter the home.

Insecticides available for use by the public include bifenthrin, cyfluthrin, deltramethrin, and permethrin. 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 experience and access to effective residual insecticides not available to the public.

These steps are effective but are not always going to prevent 100 percent of the lady beetles from entering your home. Once lady beetles get inside the home, there are few options but to physically remove them with a vacuum.

The use of insecticides indoors is of very limited value and is not recommended. The lady beetles that enter the home move into wall voids and similar places where there is no practical control. They will then emerge during the winter and spring and must be tolerated or removed physically.

The important thing to remember is that they do not reproduce indoors and, therefore, all of the lady beetles you find in your home entered from the outside.

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

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