Soybean Aphids Found in Northwest Ohio

Entomologist tells Ohio farmers big aphid populations to the north mean its time to start scouting and preparing to manage.

Published on: Jun 27, 2007

The soybean aphid, which is predicted in large numbers throughout the Midwest this season, is showing up in Ohio earlier than anticipated.

Soybean fields throughout northwest Ohio are already reporting the presence of the aphid in low numbers. Historically, soybean aphid populations don't first appear until late June.

Northern states, such as Michigan, and the Canadian province of Ontario are already dealing with high aphid populations and are heading for economic thresholds, says Ron Hammond, an Ohio State University Extension entomologist.

"My colleagues are surprised that aphid populations are showing up already in high numbers. The soybean plants are still in the small growth stages and not even flowering yet, and they are getting hammered," says Hammond, with the Ohio Agricultural Research and Development Center. "For this to happen by mid-June is a bit unusual."

Ohio growers to pay closer attention to their soybean fields and begin scouting for the aphid a bit sooner than normal, as Ohio's aphid populations will most likely migrate from more northern areas, he says.

The sapsucker, whose voracious appetite can greatly damage untreated soybean fields, came on the scene in Ohio in 2001. Since then, it has taken growers on a rollercoaster ride of high populations one year and low populations the next. This season is being predicted as a "high" year.

"Our prediction this year is that we will have problems," says Hammond. "Based on observations last year, aphid populations built up at the end of the season, and trap collections done on overwintering buckthorn across the Midwest revealed significant populations and eggs. We know the soybean aphid is coming. Growers need to be ready for it."

Researchers speculate the level of soybean aphid populations may be tied to the population of the multicolored Asian ladybeetle, a known predator. Put simply, when soybean aphid numbers are high, ladybeetle numbers are also high. Although controlling the aphids during the summer months is light, the ladybeetles may prevent the aphids from overwintering by actively feeding on them in the fall. Ladybeetle populations were low last year because aphid numbers were also low, which would account for researchers' assumptions that soybean aphid populations will be high this growing season.

For growers, the best way to manage the soybean aphid is to educate themselves on the insect, know when to scout, and to carefully time foliar insecticide applications if treatments are warranted. The economic threshold of aphids is 250 insects per plant.
For further updates on the soybean aphid, refer to the Ohio State University Agronomic Crops Team Web site at agcrops.osu.edu.