The beetles are coming, again!          

Soybean aphids and lady beetles  

[SEPT. 24, 2003]  CHAMPAIGN -- 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 the ladybug to fly away home, lady beetles are expected to do exactly this -- fly away to YOUR home. When cold weather starts to set in, soybean fields mature, and the soybean aphids will move to their overwintering host, buckthorn. 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 clifflike to them -- the 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 won't eat your food and they won't 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 United States 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 country, from Canada to Florida and coast to coast.

"The relationship among soybeans, soybean aphids and multicolored Asian lady beetles is really an example of an imported food chain -- a kind of mini-ecosystem, with a plant, the soybean; a herbivore, the soybean aphid; and a predator, the lady beetle," said Spencer.

Spencer can't 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.

[Illinois Natural History Survey news release]

Recent articles

• Weekly outlook
  Soybean market

• Corn borer survey complete