Multi-colored Asian lady beetles are moving from fields to homes

Elevated soybean aphid numbers in western Van Buren County will mean high numbers of multi-colored Asian ladybeetles trying to get into area homes soon.

Area farmers and crop scouts saw something this year (2014) that we have not seen in quite a few years in southwest Michigan. In late August and early September, soybean aphid numbers soared in portions of western Van Buren and northern Berrien counties. The infestation occurred late enough in the season that impact to soybean yields should have been minimal. That is good news for growers. And, the increased number of aphids provided a bonanza for predatory insects in the field that provide biological control for this “sometimes” soybean pest. When scouting fields in late August, we found several species feeding on soybean aphids, including green lacewings, minute pirate bugs, and most commonly, multi-colored Asian ladybeetles.

Multi-colored Asian ladybeetles are of particular interest because of their habit of entering people’s homes to survive the winter. The species often looks for protected places to wait out the cold weather. In natural settings, this often includes spaces under the bark of dead or dying trees, such as loose bark on elm trees that have been recently killed by Dutch elm disease. Because they look for protected tight places to huddle together over the winter, they often search along the joints of foundations and siding or windows of houses for cracks or crevices to gain access to the protected interior of homes. Once in the home, they often can be found moving around windows warmed by the sun on bright, sunlit days, sometimes in the fall, but often in late winter and early spring. Since the beetles can find each other through pheromones, they often will congregate in the fall along a protected area of a basement wall.

Exclusion is really the best strategy that works in keeping these insects out of your home, but sealing every opening that is large enough for these intrepid explorers to get into your house can be a real challenge. Insecticide sprays along foundations or siding are usually not very effective because the insect is not trying to ingest the material, and only briefly comes into contact with the pesticide as it moves into the building. Once in the house, Michigan State University Extension recommends the safest and most effective way of removing the beetles is to suck them up in a vacuum and change the bag or take the shop-vac outside and remove the beetles. Read “These ladybugs are driving me crazy!” from Michigan State University entomologists Howard Russell and Christina DiFonzo for more information.

Another insect species that is a native of Asia and is also expanding its way into our area are brown marmorated stink bugs (BMSB). An invasive species, BMSB are moving from areas where the pest has gained a foothold along the eastern seaboard into areas of the Midwest. MSU entomologists have been monitoring fields for this aggressive pest of fruit and vegetable production in Michigan soybean fields this summer. Like the multi-colored Asian lady beetle, BMSB also tend to try to overwinter in people’s homes. While a few BMSB have been observed in southwest Michigan so far, it is anticipated that this pest will become much more prevalent in the next few years.

Movement from fields to people’s homes and garages from both of these pests usually occurs as the soybean fields mature enough to lose their leaves or the first significant frost occurs. Many of the early planted soybeans are rapidly dropping leaves across southwest Michigan this week. 

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