Soybean gall midge is proving to be a difficult pest to manage. Bob Koch with the University of Minnesota says the insect is still new, so threshold levels for treatment have not been established.
“It seems like seed-applied insecticides aren’t providing much control, based on research from my colleagues in Iowa (and) Nebraska,” said Koch. “Foliar-applied insecticides, the insecticide sprays, aren’t really doing all that much. And that may be due to the fact that these larvae are protected inside these stems.”
Gall midge larvae feed on the base and lower stem of soybean plants, hindering the movement of water and nutrients. The complicating factor is the adult flies coming out over extended periods of time in multiple generations over the years. It is not effective to target them with just a single spray. According to the Soybean Gall Midge Alert Network, the pest has been identified in several Midwestern states this summer including two new counties in Iowa and three in Minnesota. The group says there’s also been a significant increase in adult emergence and plant injury in eastern Nebraska.