In late June 2018, entomologists in multiple states received reports of soybean fields with visible signs of dead or dying plants that were found to be associated with soybean gall midge. For the past decade, soybean gall midge has only been considered a secondary pest of soybean, however, a number of observations during 2018 suggest it is likely a primary pest. Unlike previous years, damage from gall midge was observed in late June, two months earlier than observed previously. In most cases, heavily damaged fields were adjacent to a field that had been planted to soybean the previous year and plant death was often greatest next to areas with dense vegetation (uncut smooth bromegrass). A large majority of midge infested plant samples analyzed in 2018 contained a number of different plant diseases. Other species in the same genus have been reported to act synergistically with various diseases in damaging other legume crops, it is unknown how the soybean gall midge interacts with diseases in soybean. This 3-yr project would increase efforts to assess the timing of emergence of soybean gall midge adults and expand this effort to evaluate the potential infestation period over the growing season. Furthermore, interactions between soybean gall midge and plant diseases will also be determined. Sentinel plants would be exposed to a field for a period of one-week beginning in early spring through late August and evaluated for the presence of the midge and plant diseases. Sites would be adjacent to areas with high pressure from soybean gall midge the previous season. In addition, sites would consist of field plots with insecticide, fungicide and combination treatments to evaluate the role and interactions between fungal pathogens and soybean gall midge. Updates on this study would be provided during the growing season via UNL CropWatch and Twitter. Findings will also be disseminated through field days, conferences, as well as extension and research publications. Results from this study would provide farmers with an understanding of the risk period for infestation from soybean gall midge and its yield loss interactions with plant diseases.

The objective of this proposal are to evaluate soybean gall midge infestation potential in soybean throughout the entire growing season and evaluate the presence of plant diseases with these infestations using plants grown in a greenhouse and exposed to the field for brief periods.

The second objective is to evaluate a combination of pesticide tactics such insecticide and fungicide applications for management of soybean gall midge and its interactions with plant diseases under field conditions.

Milestones will occur during early season with documentation of first adult emergence and location of emergence. Assessments of infestation and disease inoculation of sentinel plants will be reached at the end of each growing season along with plant damage assessments and 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 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.

Updated May 26, 2023:

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The lack of interaction between plant disease and soybean gall midge is important for the overall management strategy of this new species. We could not detect any differences in larval abundance on plants, plant injury, or yield even with an excessive use of fungicides was applied in the field. This lack of response along with the cost of fungicides should remove the use of a fungicide as a control strategy for soybean gall midge.

- Provides farmers with a window of the season at which their crop is at risk to soybean gall midge infestation
- Provides insight into potential economic impacts occur after spray dates during early vegetative stages
- Provides a basis for future management practices.
- Provides an understanding of the potential of other strategies that are not designed directly for soybean gall midge to mitigate losses
- Regardless of the results, the data would allow growers to make informed decisions about soybean gall midge management