Research Highlights

Update on Checkoff-funded Research on Soybean Gall Midge - a New Soybean Pest

Justin McMechan, Crop Protection and Cropping Systems specialist, University of Nebraska-Lincoln

With emergency checkoff funding provided by the North Central Soybean Research Program (NCSRP) and the North Central IPM program, soybean researchers and farmer cooperators in Nebraska, Iowa, Minnesota, and South Dakota have quickly mobilized to start answering basic questions about the soybean gall midge  — a new insect pest of soybean.

The initiative is in response to a significant increase in reports from soybean growers and consultants of dying soybean plants associated with soybean gall midge infestations.  

Midge infestations were previously assumed to be secondary after some kind of injury such as hail or disease. Now gall midge infestations are being found earlier, in higher numbers, and often in the absence of injury or disease.

Wilting or dead soybeans along field edges with decreasing injury into the center of the field is usually the first sign of infestation. Stems of infested plants may break off easily at the soil line, revealing small white to orange larvae feeding on the soybean tissue. The presence of small, orange larvae in the base of a soybean stem is considered diagnostic for this pest.

Checkoff-funded research, much of it on-farm, is underway in four states to address questions of greatest concern to soybean growers, such as pest emergence, the efficacy and timing of insecticide treatments, and the role of cultural practices in preventing injury from gall midge feeding.

Here are some of the results:

• The adult gall midge has been identified and the pest recently described as a new species: Resseliella maxima, soybean gall midge.
• The emergence of the first generation appears to be mid-June. We think at this point that two generations occur during the season.
• Infestation does not occur until after the soybean V3 stage. See an early-season scouting video here.
• The heaviest infestations occur in fields next to a field that had been planted to soybean in the previous year. Injury is most severe in the first few rows at field edges.
• First-year observations in a planting date study found that 45-47% of soybean plants planted on May 1 or May 15th were found to be infested with gall midge, while only 3% of those planted on June 1 were infested. No soybeans planted later than June 15 were infested.
• Several insecticide chemistries were tested in this season as a foliar treatment but their efficacy and value will not be determined until yields are collected. Seed treatments were also tested in multiple states. Insecticide efficacy studies will continue.

Resources

Soybean Gall Midge Updates, UNL Crop Watch  

Update on soybean gall midge: A new pest of Minnesota soybean MN Crop News, June 2019

Soybean Gall Midge: An Emerging Pest of Soybeans UNL Crop Watch, Jan 2019

New Soybean Pest in Iowa: Soybean Gall Midge Integrated Crop Management News, July 2018

Soybean Gall Midge: Adult Stage Identified UNL Crop Watch, Nov 2018

For updates through the season, please follow the Twitter accounts of the researchers below, or visit the Soybean Gall Midge Updates page of the UNL Crop Watch online newsletter.  

If you notice soybeans with symptoms and larvae resembling the soybean gall midge, please take a photo and contact one of the researchers on the project: 

Justin McMechan, justin.mcmechan@unl.edu, University of Nebraska Crop Protection and Cropping Systems specialist.
Twitter: @justinmcmechan

Thomas Hunt, THUNT2@UNL.EDU, University of Nebraska Extension entomologist

Robert Wright, rwright2@unl.edu, University of Nebraska Extension entomologist.
Twitter: @BobWrightUNL

Erin Hodgson, ewh@iastate.edu, Iowa State University Extension entomologist. Twitter: @erinwhodgson

Bruce Potter, bpotter@umn.edu, University of Minnesota IPM specialist

Bob Koch, koch0125@umn.edu, University of Minnesota Extension entomologist

Adam Varenhorst, adamvarenhorst@sdstate.edu, South Dakota State University Extension field crops entomologist

Published: Jul 25, 2019