WOOSTER, Ohio — The soybean aphid, a pest known to invade Ohio soybean fields each year from the north, has now been found to overwinter in the state.
However, agricultural specialists speculate that the biggest issues with soybean aphid infestations will still come from their migration patterns.
"We don't think there's enough overwintering to lead to our problems in Ohio," said Ron Hammond, an Ohio State University research entomologist with the Ohio Agricultural Research and Development Center. "We think that it will come from migrating adults this summer." Researchers are anticipating a large aphid population in soybean fields this year, in keeping with the pattern of low populations one year, high the next. Last year, soybean aphid populations were very low in Ohio.
"If anything, these overwintering aphids will cause hot spots in certain Ohio soybean fields," said Hammond. "In other words, there will be an unusually high population of aphids in a small area of a field, with low population densities surrounding it."
Hammond said the aphids were found hatching from eggs on common buckthorn — a small shrubby tree considered an invasive species in many states, including Ohio. Buckthorn has been identified as a host for the soybean aphid.
"A small amount of buckthorn has been found in Ohio," said Hammond. "We found a site near the Columbus campus where the buds on the buckthorn broke a few weeks ago. As soon as the buds broke, the soybean aphid eggs hatched. More recently, we also found a similar situation near Marion and Ashland, Ohio — sites further to the north."
However, most of Ohio's problems come from migrating adults arriving in soybean fields in July and August from such places as Minnesota, Wisconsin and Canada. The aphids will feed throughout the growing season, causing severe injury and yield losses if populations are high enough.
"We are recommending growers plant as early as possible and then scout fields on a regular basis. If and when aphid populations reach their threshold (250 insects per plant), then treat with a foliar insecticide," said Hammond. "The IPM approach to managing the aphid, we believe, is still more effective for Ohio growers than the seed treatment that is currently available on the market."
The seed treatment, called Cruiser, offers aphid control at planting. The treatment appears to be more effective in more northern states like Wisconsin, but may not maintain ample efficacy when aphids begin feeding in Ohio fields in July.
"In Ohio, we tend to plant soybeans in May and the problems don't begin until later in July," said Hammond. "We don't think this seed treatment is going to last that long. From that standpoint, we are not recommending it to growers."
Hammond also reminds growers that scouting for soybean aphids may be more of an easier task this year with the potential for the development of soybean rust.
"Growers will be out in their fields monitoring for soybean rust," said Hammond. "While doing so, it would be a good time to closely watch for aphids. Growers can kill two birds with one stone and it would be nothing but a benefit to them."