Emergence of Chinese aphid raises concerns among farmers

NEW LONDON, Mo. -- A small winged insect native to China is causing some concern for farmers in northeast Missouri.

Soybean aphids were detected in late July by a seed company representative in a field near New London, about 100 miles north of St. Louis, said Alix Carpenter, University of Missouri Extension Service agronomy specialist.

"It's a new and emerging pest in our neck of the woods," she said. "It's the first time we've had a report in Missouri where we've had a high enough level that treatment is justified."

The field where the soybean aphids were discovered has been sprayed, apparently successfully, Carpenter said.

Soybean aphids were first identified in the United States in 2000. They've been found in Missouri, Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Ohio, West Virginia and Wisconsin. Some of the heaviest infestations have been observed in southeastern Michigan, southern Wisconsin, southeastern Minnesota, northern Illinois and northern Indiana.

"We don't frequently see new pests," Carpenter said. "This is something completely new no one had seen before four years ago."

Several insecticides are available to combat soybean aphids. The expense of treatment varies, Carpenter said.

"This is not a normal time when someone would be applying insecticide, so having to make an extra application, in that sense it is expensive," she said.

Soybean aphids also have natural enemies: ladybugs and parasitic wasps, which complete their larval development within the body of another insect and eventually kill it. There is also a fungus that will attack soybean aphids.

"In the past, the natural predators have taken care of them and their numbers have plummeted rather quickly," Carpenter said. "This year we did not get that to happen."

The soybean aphid, which is yellow and a little smaller than an uncooked grain of rice, feeds by sucking plant sap, which can cause leaf curling and plant stunting. Early populations feed on developing leaves and stems. As the plant matures, populations begin to feed on the undersides of leaves. Aphids can also transmit viruses harmful to soybeans.