Soybean aphid: New pest bugs soybean growers


WOOSTER, Ohio – Along with the stresses of the weather, soybean growers might be faced with yet another problem: soybean aphids.

Now in Ohio. The pest was recently identified in a Wooster field and entomologists are encouraging growers to scout their fields.

Soybean aphids are relatively new to the United States and to Ohio State University researchers. The pests were first identified in 2000 and were a major problem in northern Ohio and surrounding states in 2001, said Ron Hammond, an entomologist with the Ohio Agricultural Research and Development Center.

Hard to predict. Last year researchers were prepared to battle the bug, but it was almost nonexistent.

“Two years ago, we didn’t really realize we had the pest until too late,” Hammond said. “And last year, it didn’t really show up – it was low throughout the Midwest.

“We don’t really know what it will do this year, but we hope it’s like last year,” Hammond said.

Based on the soybean aphid damage seen in 2001, Minnesota was expecting to spray over 2 million acres last year. Ohio was prepared to spray one-half million acres, and that was based on damage seen only in the northern part of Ohio, Hammond said.

If the aphids get into bigger soybean regions, it could be a major problem.

Costly critter. A population of soybean aphids can easily reduce yields by five to 10 bushels per acre, Hammond said. Injury from soybean aphids include pod abortion, and later in the season, small seed development.

If the soybean aphid becomes a problem, farmers would be facing $10 to $15 per acre of additional costs for spray, Hammond said.

However, because it only takes three to four bushels to cover spray cost, the cost of spray is well justified compared to the losses caused by soybean aphids.

“I hope it’s a problem we don’t have to get into,” Hammond said. “Growers have enough to handle with the weather and prices. They don’t need to have another problem.”

The pests, which cover the plant and suck the juices out of it, can get into the thousands per plant, Hammond said.

Control. Growers want to keep numbers minimal, but do not want to spray too soon or it will allow for the aphids to return by the end of the season.

It is recommended to wait to spray until early- to mid-July when the plants are flowering and setting pods, and the majority of plants are covered with 250 or more aphids.

Look like leafhopper. Soybean aphids, which are often mistaken for small potato leafhopper nymphs, overwinter on buck-thorn. This host is usually found along hedges, fence lines, and wooded areas.

But the Wooster field where the aphids were identified is not close to hedges, fence lines or woods, Hammond said.

The aphid also is thought to be a cool-season pest because of its invasion of northern United States, but researchers are not yet sure.

If the aphids are a problem this year, more traits will be figured out.

Parasite control? While the soybean aphid means additional worries for growers, entomologists are intrigued.

A lot of the aphids found in Wooster were heavily parasitized, Hammond said. That was not the case in 2001.

Parasites are a form of biological control and while they may not completely rid Ohio of soybean aphids, they could help.

Hammond’s colleagues from neighboring universities have been to China and Japan, where the aphid originated, looking for exotic parasites to combat the aphid.


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