Soybean aphid populations are on the rise in Ohio, just as entomologists and other industry specialists have predicted.

Ron Hammond, an Ohio State University research entomologist with the Ohio Agricultural Research and Development Center, recommends that soybean growers hit their fields now to monitor numbers and apply a spray treatment if populations hit the 250 aphids-per-plant threshold. One field in northwest Ohio has already hit that threshold, the first time aphid populations have been that high so early in the growing season.

“Everything’s going according to our predictions. We are starting to find aphids in most soybean fields throughout Ohio, and the farther north we go the heavier the populations,” said Hammond. “With cooler temperatures predicted, I would expect the aphids will keep coming and by mid-to-late July we could be seeing a lot more fields reaching threshold.”

The soybean aphid, an insect pest whose quirky behavior has made it more famous than the actual damage it causes, first came on the scene in Ohio in 2001. Since then the insect, a sapsucker which can reduce yields if in high enough numbers and left untreated, has put growers through a rollercoaster ride of low populations one year and high the next. This just happens to be one of those “high” years.

“We are not sure why we are having such early high populations, but I would say that based on what we’ve been seeing in the fields, I would expect more problems to occur in late July and early August,” said Hammond.

This time period corresponds with the soybean plant’s flowering and pod development stages, where pods set and yields are determined. And it’s a stage that’s most sensitive to environmental stresses.

“Soybean plants always tend to put on more flowers and start out with more pods that what they end up with, and any kind of stresses causes a lot of those flowers to abort and pods not to set,” said Hammond. “This is a critical time in the crop’s development where the managing of soybean aphid becomes that much more important.”

Hammond said that growers should be scouting their fields once a week to monitor soybean aphid populations, and spray as soon as populations reach threshold.