University of Wisconsin - Extension

If you have had problems in the past with Asian lady beetles in your home, this is the best time to seal them out or spray. The last week of September and the first two weeks of October are the times to treat for these invasive insects. As the weather turns cool they begin looking for a place to settle in for the winter. Unfortunately, they may choose your house.

Phil Pellitteri, University of Wisconsin-Extension's "bug doctor" and a professor of entomology at the UW-Madison Insect Diagnostic Lab, urges homeowners to act now to keep the bugs out.

Pellitteri recommends physical barriers to keep them from entering houses and other buildings as a long-term solution. Sprays are a temporary and secondary solution. And he said it's important to act quickly when an invasion begins because the bugs can be almost

impossible to kill or remove once they've found a snug spot to spend the winter.

It has become common to see large numbers of lady beetles clustered around homes and other buildings during the fall. 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 known 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 native to eastern Asia and is an important predator of scale and aphid pests on trees in Asia. The first specimens recovered in the

U.S. were collected in Louisiana in 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 are congregating on homes in search of overwintering sites. They usually select the west or southwest side of buildings for initial congregation sites, but many leave on their own by nightfall. It is likely they 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 intrusions 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 chances of future sightings. Equipment and materials mentioned can be purchased at

most home improvement or hardware stores.

1. Install door sweeps or thresholds at the base of all exterior entry doors. While you are lying on the floor, check for light filtering under doors. Gaps of 1/16 inch or less will permit entry of the bugs. Apply caulk (see #3 below) 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.

2. Seal utility openings where pipes and wires enter the foundation and siding 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.

3. 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.

4. 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 late September or early October to kill and repel the beetles before they get in. The most effective sprays are various synthetic pyrethroids such as permethrin, cypermethrin, cyfluthrin, deltamethrin and lamda-cyhalothrin. Concentrate along doors, windows, and overhangs on the south, west and east sides of the structure. It may take 2 or more gallons of spray to get thorough

coverage. You may wish to hire a professional pest control company for this 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, walls or curtains. They can also be collected by hand and released outside.

A UW-Extension fact sheet on the Asian lady beetle can be found at http://www.uwex.edu/ces/wihort/gardenfacts/X1050.pdf. For more information on this and other insect pests, see the web site of the UW-Extension Urban Agriculture/Horticulture Team at http://www.uwex.edu/ces/wihort/.