The Hodgson lab regularly scouts for field crop insect pests during the summer, which includes monitoring the distribution of new pests. Sometimes this effort is part of a regional grant, but occasionally it is for our own interest. This article shares the updated distribution maps for soybean gall midge and soybean tentiform leafminer in Iowa with detections from the 2026 growing season. These are the known distributions; these insects may be present in counties not on the maps but have not yet been detected.
Soybean gall midge
For those who have experienced plant death since its first detection in Iowa in 2018, soybean gall midge may not feel like a new pest. For others, they may have discovered soybean gall midge in their field for the first time this year. Regardless, we have looked for soybean gall midge in Iowa counties since 2018, and one larva discovered in one stem in a county marks the county as “infested.” Figure 1 does not imply severity of infestation; rather, the color denotes the first year that soybean gall midge larvae were detected in the county.
Review the soybean gall midge encyclopedia article to learn how to scout for soybean gall midge next summer. Visit the Soybean Gall Midge Alert Network website to see the full distribution of this pest.
Soybean tentiform leafminer
Although the soybean tentiform leafminer is a new pest of soybean, this insect is not new to the region. Historical data suggest that Macrosaccus morrisella, now known as the soybean tentiform leafminer, is a moth species that feeds on native legumes primarily growing in forested areas. Entomologists at the University of Minnesota are researching the potential impact on soybean and management strategies for this new pest. Read more about identification in this profile from the University of Minnesota.
Our role is to scout 30 fields each year (2025-2027) to look for soybean tentiform leafminer. Since Iowa has limited forested area, we choose soybean fields next to unmanaged tree lines (i.e., tree lines that have a lot of native vegetation) to sample, looking for caterpillars forming tentiform mines on the undersides of leaves. Figure 2 shows the counties in Iowa where soybean tentiform leafminer has been detected in 2025 and 2026.
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 11, 2026. The information contained within may not be the most current and accurate depending on when it is accessed.
- Extension Specialist II
- Professor
- Extension Entomology Specialist
- ANR Crops Team Leader