From the Illinois Natural History Survey
Unlike the 1964 invasion orchestrated by John, Paul, George, and Ringo, the newest beetle invasion was brought to us from the Orient, not Europe. The multicolored Asian lady beetle, a small orange/red insect with dark spots, is thriving this year in record numbers thanks to the abundance of one of its favorite foods, the soybean aphid.
A relatively cool summer allowed the populations of soybean aphids to explode in soybean fields. Multicolored Asian lady beetles responded by producing the largest populations seen in Illinois in years. We have seen lady beetle numbers in some soybean fields increase 200 fold during the past month, said Joseph Spencer of the Illinois Natural History Survey a division of the Illinois Department of Natural Resources.
Spencer says that like the exhortation in the nursery rhyme for lady bug to fly away home, lady beetles are expected to do exactly thisfly away to YOUR home. Once cold weather starts to set in, soybean fields mature and the soybean aphids will move to their overwintering host, buckthorn, and lady beetles are going to look for new food and shelter, too.
Multicolored Asian lady beetles evolved in the Orient, where they naturally overwinter in cliff faces. In our area of the world, they will begin to aggregate at spots that appear cliff-like to themthe sides of light-colored houses and buildings.
Many will end up around doors and windows, but they will use any crack, nook, or cranny to gain entrance into your home. The good news is that lady beetles wont eat your food, and they wont harm the structure of your house, said Spencer.
The beetles may become active on warm, sunny winter days and begin flying around a bit. They can also let off an annoying smell when there are large numbers present. For people who are bothered by lady beetles in their homes, the recommended solution is simply to seal cracks and vacuum them up if they get in.
While the lady beetle can be a bit of a nuisance in your home, and it can displace native lady beetles in the outdoors, its presence is considered more beneficial than harmful.
It is our best natural defense against the soybean aphid, and thus is economically important to agriculture, said Spencer.
This beetle was introduced into the U.S. numerous times since 1916 to control tree-feeding aphids and scale insects in the southern and eastern states. By 1994, it had thoroughly colonized the U.S. from Canada to Florida and coast to coast.
The relationship among soybeans, soybean aphids, and multi-colored Asian lady beetles is really an example of an imported food chain, a kind of mini-ecosystem with a plantthe soybean, a herbivorethe soybean aphid, and a predatorthe lady beetle, said Spencer.
Spencer cant predict if there will be a lot of soybean aphids next year. However, if the soybean aphid returns in large numbers, there will be an ample supply of lady beetles ready to keep the aphids in check.
We are fortunate to have these lady beetles to feed on this soybean pest, said Spencer.