In late June 2018, entomologists in Nebraska, Iowa, South Dakota, and Minnesota began received reports of soybean fields with visible signs of dead or dying plants that were found to be associated with soybean gall midge. The presence and injury of soybean gall midge was most significant in fields adjacent to crop that was soybean the previous year. In addition, dense vegetation (grasses and shrubs) between these two fields has been observed to increase the infestation potential of soybean gall midge. For three years, emergence cages were used to track overwintering soybean gall midge adults from at least 27 sites across four states as part of an emergence NCSRP project. Between May 31st and June 14th the first overwintering adults have been captured in east-central Nebraska. Within about 11 days of first emergence, soybean plants began showing visible signs of infestation. The duration of overwintering adult emergence varied significantly between sites ranging from 10-44 days in Nebraska with an average of 16 to 36 days depending on the year across all sites. At ENREC near Mead, NE, a preliminary experiment on planting dates of soybean relative to adult emergence was conducted with one year of support from the North Central IPM program. Results showed that approximately 50% of plants were infested with May 1st and May 14th planting date whereas only 3% of plants were infested when planted on May 31st. This 3-year project would continue to evaluate planting date relative to adult emergence and expand this effort to include the use of an insecticide seed treatment. In addition, growers would be identified to evaluate and compare the results of planting dates on their farm relative to soybean gall midge emergence. Results from this study would provide farmers with an understanding of risk for overwintering soybean gall midge infestation with different planting dates as well as the potential for seed treatments to mitigate early season infestations.

The first objective will be to evaluate soybean gall midge infestation and injury of soybean planted at four different planting dates with and without an insecticide seed treatment.

For the second portion of the project, farmer fields will be monitored for adult emergence data as part of an ongoing NCSRP and NSB project. To add to this project, adjacent farmer field’s will be evaluated for the planting date and the use of seed treatments relative to adult emergence at these sites.

In general, it assumed that best methods for controlling soybean gall midge is to limit the infestation potential of the
overwintering generation. This project proposes a combination of small plot and whole field research to provide farmers with the most practical means of evaluating and making management decisions on these tactics.

Milestones will occur during early season with documentation of first adult emergence and infestation assessment of planting dates. Assessments of season long infestation will be reached at the end of each growing season along with yield impacts on field plots.

Resulting data from this project would be presented at a number of Nebraska outreach extension efforts such as Soybean Management Field Days (approx. 400 attendees), Nebraska Crop Management Conference (approx. 300 attendees), Midwest Crop Production Clinic (50 attendees), Crop Production Clinics (1,400 attendees), and Nebraska Soybean Expo (300 attendees). Updates on research progress would be presented through Blackboard Connect Alert System, Twitter, Market Journal, grower listserves, Market Journal interviews, and UNL Cropwatch articles. We would expect that at least two peer reviewed publications will result from this work.

Planting date has always been an important consideration for soybean farmers. Knowledge of the impact on this tactic with significant soybean gall midge pressure would allow farmers to potentially prioritize fields to reduce risk of soybean gall midge injury. Studies of its interaction with seed treatments would provide an evaluation of the value of this tactic in combination with planting date to mitigate losses and maintain production of soybean. To with the first year of the project completed, we have demonstrated the potential of delayed plantings May 22nd and June 1st to reduce infestation, injury and obtain yields that are statistically equivalent to April 22nd and greater than May 2nd and May 12. Such results, if they are consistent could be part of a pest management program for soybean gall midge.