Friday, March 29, 2024

New predator colonizes Midwest crops

March 14, 2001
Field Crops Entomologist Christina DiFonzo and Pesticide Educator Rebecca Hines investigate a Buckthorn tree for Aphid eggs Tuesday next to the train tracks on the corner of Farm Lane. In the winter the Aphid migrate from soybean plants to harbor among the Buckthorn trees, and come spring time the Aphid females will emerge and return to the soybean plants. —

MSU insect specialists are taking to the fields to research the effects of a new plant predator - the soybean aphid.

“The aphid migrated here from Asia and was first detected in Wisconsin last July,” said Christina DiFonzo, an assistant professor of entomology. “We have only begun to research this insect, so we don’t know too much about it.”

Researchers do know the aphid is a yellow insect about the size of a pinhead.

It appeared in the Midwestern states suddenly last summer with populations highest near lakes, she said.

Edward Grafius, chairperson for the Department of Entomology, said prior to the insects, soybeans - a major crop in Michigan and the Midwest - didn’t require insecticide treatment.

“If the aphid becomes a seriously damaging pest, insecticide treatments may be required, increasing costs to growers,” Grafius said.

Although scientists don’t know when aphids colonize the fields they prey on, they do know how damage is caused. The insects have a needle-like mouth piece which they use to tap into plants with and suck out the juices, DiFonzo said.

“There was only a short time in the 2000 field season to observe soybean aphid damage,” DiFonzo said. “We were able to document much of the life cycle and we tried to figure out which conditions favor the insect the most.”

It takes hundreds of aphids to cause serious damage to soybean plants, but it only takes a few to transmit diseases, she said.

“Aphids are like little dirty, flying hypodermic needles,” DiFonzo said. “They can also spread some nasty plant diseases.”

One problem the insects is causing growers is not knowing how to deal with them.

“It is difficult to spray pesticides on the fields late in the season without physically damaging the soybeans,” she said. “Last year, infested fields tended to have large numbers of natural enemies.

“Spraying kills the natural enemies but not all the aphids, usually resulting in a rebounding of aphid numbers.”

MSU researchers have been getting an early start this year, in hopes to get a jump on the insect that surprised soybean farmers last season, DiFonzo said.

Doug Landis, professor of entomology, has studied natural enemies in field crop management for 13 years and teamed up with DiFonzo in researching the aphids.

“We suspect soybean aphids can be managed by biological control because predators will naturally attack them,” he said. “We expect the insect left some of its natural predators behind in Asia and we want to study more general natural enemies common to this area to see the impact in North America.”

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