Key Takeaways

• Early soybean gall midge activity: Soybean gall midge activity began earlier at several monitoring sites than in 2025, though pressure varied by location.

• Dectes populations increase: Dectes stem borer activity was similar to or greater than last year, with larvae now present across monitoring sites.

• Watching for diseases: Diseases have not yet been observed, but researchers expect them to emerge later in the growing season.

A new growing season brings renewed concerns for soybean gall midge, Dectes stem borer, and diseases in Nebraska soybean fields. Since 2024, the Nebraska Soybean Board has funded a study that has allowed us to monitor these pests across eastern and portions of central Nebraska to better understand their distribution, seasonal activity, interactions and impact on yield. You can find the previous project updates from June, July, August and December.

Soybean Gall Midge

June Updates

• First emergence of adults occurred on May 29in Otoe County near Talmage.
• Dead and wilting plants were detected at four of the six monitoring site locations (Figure 2).
• Northern Lancaster and Otoe counties had the highest number of larvae per stem of 4.6 and 1.1, both of which are higher than was observed at these sites in June last year. 
• Despite southern Lancaster County plants having a low larval count, this site showed the greatest proportion of dead or wilting plants.
• Soybean gall midge larvae were detected in Dixon County at low frequencies, and no wilted or dead plant was reported.
• No pest activity detected was in Clay County.

Compared to this time last year, soybean gall midge (SGM) activity appears to be starting earlier at several monitoring sites. 

In southwestern Lancaster County, we found fewer larvae than during the unusually high counts recorded in June 2025, although plant death remained high. At the northern Lancaster County site, larval numbers were more than twice as high as they were at this time last year. Cass and Otoe counties also had more larvae in soybean stems than they did in 2025, suggesting infestations are developing earlier this season. 

In contrast, Dixon and Clay counties looked much like previous years, with low or no soybean gall midge activity.

July Updates

• Larval numbers increased in all monitoring sites where SGM was detected in June.
• The largest increases in larval numbers occurred at the northern and southern Lancaster County sites and Dixon County.
• Except for southwestern Lancaster and Dixon County, all monitoring sites showed an increase in the percentage of wilted or dead plants.
• The Clay County monitoring site was lost following a severe hailstorm.

Compared to last year, soybean gall midge pressure has generally been lower at the northern and southern Lancaster County, Cass County, and Otoe County monitoring sites, despite higher larval numbers early in the season during June. The percentage of wilted or dead plants at these locations is also about half of what was observed at this time last year, except for Cass County, where plant injury remains similar to 2025. 

In Dixon County, larval numbers increased substantially this year, although soybean plants have not yet developed noticeable wilting or mortality. Based on previous observations, we expect symptoms to increase over the coming weeks.

Dectes Stem Borer

June Updates

• No DSB larvae have been detected.
• Only a single egg-laying puncture was found.
• Adult beetles were active in soybean fields.

In 2025, June sampling did not detect any egg-laying punctures or Dectes stem borer (DSB) larvae. 

This year, only a single puncture has been found in Lancaster County. Although adult beetles are now active and can be found on soybean plants, their presence does not necessarily mean egg laying has begun.

July Updates

• Dectes punctures in petioles and larvae were found in plants at all sites.
• The greatest number of punctures was detected at northern and southern Lancaster County sites.
• The highest larvae counts were found in northern Lancaster and Cass counties.
• Dixon County had the lowest DSB infestation overall.

Compared to 2025, Dectes stem borer activity has remained similar or increased across most monitoring sites. Northern Lancaster County continues to have the highest numbers of egg-laying punctures and larvae, whereas Dixon County again had the lowest level of activity. In Cass County, the number of punctures and larvae was nearly identical, suggesting that most egg-laying punctures resulted in successful larval development.

In contrast, the southern Lancaster County site had relatively few larvae compared to the number of punctures, indicating that not every puncture resulted in successful larval establishment.

Diseases and Interactions Among Pests

No diseases or pest interactions were observed in June. However, Dectes stem borer and soybean gall midge were found co-infesting the same petioles in July. Based on observations from 2024 and 2025, diseases are expected to occur later in the season. In July, SGM larvae were found around Dectes egg-laying sites only in southern Lancaster and Cass counties (Figure 6). These co-infestations are expected to be found in sites where both pests are in high numbers.

Our next update is expected in late August after we finish processing the next round of collections. If you have any questions about the project, please don't hesitate to contact us by phone or email.