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Research Highlights

Research Highlights
Identifying Soybean Gall Midge Management Opportunities

Soybean gall midge can be found along field edges causing wilting and dead soybeans. Dark discoloration can be found at the base of the soybean plant stem. Photo: Justin McMechan

By Barb Baylor Anderson

Large, widespread wind events like the derecho in 2020 provide strong justification for the value of scouting fields for emerging soybean pests to determine distribution. One of those pests is the soybean gall midge, which has been spreading in the Midwest the last three seasons. Soybean gall midge has now been found in Nebraska, Iowa, Minnesota, Missouri and South Dakota.

To better understand the distribution and severity of soybean gall midge, emergence timing and the source of adult soybean gall midge, the North Central Soybean Research Program (NCSRP) is funding multi-state research led by Justin McMechan, University of Nebraska Extension entomologist. Soybean lines from U.S. germplasm are being screened for resistance or tolerance. 

“Field surveys provide soybean farmers with an estimation of the level of risk for injury in their area. Newly identified areas provide an opportunity to engage farmers and their retailers to make them aware of the pest and the potential resources to manage it,” says McMechan. 

Soybean gall midge larvae are bright orange, making them easy to identify. Photo: Crop Protection Network

A website has been established to monitor distribution and provide alerts about the new pest, www.soybeangallmidge.org. In 2020, researchers confirmed continued spread in existing states, including 19 new counties, bringing the total to 114 counties across the five states. In addition, collaborators in North Dakota, Wisconsin, Illinois and Kansas monitored fields last year but did not find soybean gall midge.

Soybean farmers in areas already infested with soybean gall midge can scout for the pest and take advantage of the alert network. Farmers also can implement border spray applications, tillage treatments and mow vegetation around fields to try and mitigate losses. 

Last year, McMechan says adults emerged on June 10 with activity across the entire network of adult emergence cages in nine days. 

“The average duration of emergence from overwintering sites (last year’s soybean fields) was 25 days for east central Nebraska, 10 days longer than in 2019,” he says. “Several fields showed an overlap in adult emergence between last year’s and this year’s soybean fields.”

Preliminary management practices have focused almost exclusively on insecticides to mitigate pest pressure. But McMechan says the efficacy of these products and window of opportunity to apply them is largely unknown. In addition, relying on pesticides may lead to secondary pest issues or resistance to insecticides. No commercial varieties have been identified as resistant. Evaluations so far includes 768 soybean lines from U.S. germplasm screened at locations in east central Nebraska and western Iowa. McMechan says approximately 98 percent of those lines were infested. Work continues to identify potential sources. Meanwhile, uninfested lines may just be escapes and not resistant to soybean gall midge at all.

For 2021, McMechan says the adult emergence network will continue and soybean accession line testing will expand to four sites, two in Nebraska and one each in South Dakota and Iowa. 

As for additional research, McMechan says the list is long and daunting. “We did not have much success with foliar applications in 2020, likely as a result of the long duration of emergence,” he says. “We have 15 studies planned for 2021 that include biology/ecology, cultural control, chemical control, population genetics and landscape/environmental factors for injury.”

“There are many production issues like this that affect the entire Midwest, not just specific states,” says Mike Schlosser, who serves on the NCSRP Board of Directors and is a director for the North Dakota Soybean Council from Edgeley, N.D. “It makes sense to pool our research efforts by tapping into the expertise of several resources for more efficient use of checkoff funds. This approach helps speed up opportunities to find solutions to production challenges.”

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.