Research HighlightsSoybean Gall Midge Fight Continues
In this article, you’ll find details on:
- Midwest entomologists are exploring several methods to reduce soybean gall midge impact.
- Research includes searching soybean germplasm and commercial varieties for pest resistance, and exploring cultural practices to lessen the damage.
- The research is supported through the Nebraska Soybean Board and a larger project with the North Central Soybean Research Program.
- The Soybean Gall Midge Alert Network has proven effective with some farmers for timely spray applications.
By Carol Brown
First identified in Nebraska in 2019, the soybean gall midge has made its presence known among Midwest farmers and entomologists. The insect was previously unknown to science and it has been documented only in the United States. Now, soybean gall midge occurs in seven states.
The North Central Soybean Research Program (NCSRP) funded a special, off-cycle grant for researchers to capture as much information on this yield-robbing pest as quickly as possible. Led by Justin McMechan, University of Nebraska entomology professor, his team found soybean gall midge in Iowa, Nebraska, South Dakota and Minnesota. Populations have since been identified in more counties in these states. Gall midge has also been detected in several Missouri and Kansas counties and in one North Dakota county.
Through continued soybean checkoff support by NCSRP and the Nebraska Soybean Board, McMechan leads research from several aspects to reduce soybean gall midge damage. George Graef, a soybean breeding expert at the University of Nebraska, is searching soybean germplasm for gall midge resistance and McMechan is testing current commercial varieties for resistance. Included in the project is research on tillage and mowing to improve control along with the documentation of gall midge locations and soybean injury levels across the Midwest.
“Studying the soybean gall midge is challenging as we’re learning both the biology and the ecology of this pest,” McMechan explains. “If you look at rootworm for example, scientists have been studying it for over a century, and they accumulated a wealth of knowledge on its biology and capabilities and they are still conducting management research. With soybean gall midge, we’re researching both areas hand-in-hand.”
During the last seven years, the team has collected considerable knowledge about the pest, but several unknowns remain. Gall midge impact has dropped slightly, he says, but there are growers getting hit hard and several areas still show a lot of pressure.
“Over the years, farmers have shifted the soybean varieties they grow. Our soybean germplasm work shows there’s a considerable amount of resistance, but farmers don’t know the whether the varieties they are planting are resistant,” he says. “We tested several commercial varieties for resistance – the same varieties farmers are planting on their farms. We’ll find results together, but we won’t see how the varieties perform until mid to late season.”
Tillage is a Head-Scratcher
The team is exploring tillage and mowing for gall midge control, and results have been varied.
“The tillage research has been one of the most frustrating studies in terms of knowledge gained,” comments McMechan. “In controlled, confined conditions, we’ve seen the mobility of gall midge pupa. They can wiggle through the soil to the surface, allowing the adults to emerge. Farmers have had emergence in all tillage levels – from extreme tillage to no-till. The results are inconclusive regarding why some farmers are successful in some locations and not others.”
This year, McMechan and his team are altering the tillage trials. In some areas, they have seen that spring tillage in the current year’s soybean, just prior to planting, was effective in reducing infestation of the gall midge. He believes the planter’s press wheels pushed down the soft soil in the tilled treatments and subsequent rains may have caused the soybean stem fissures to be covered up. He’s hoping to confirm these theories through the tillage trials.
He and his team are also evaluating infested soybean stems buried in the soil to study the effects of tillage and patterns of adult emergence. Capturing adults from overwintering sites or previous year’s soybean fields in the spring has proven to be difficult due to their uneven distribution across a field.
“By concentrating larvae in small, defined areas through stem burial, the likelihood of collecting emerging adults increases, which improves our ability to assess soil-based management tactics,” says McMechan. “Using different tillage equipment and application timing on these burial sites may further clarify the impact of these practices on soybean gall midge. Additionally, stem burials may improve the chances of detecting adults from infested fields, which growers use to guide the timing of their spring foliar insecticide applications.”
Hilling, which covers the fissure at the base of the stem, has also been used to reduce the soybean gall midge impact.
“With hilling, a cultivator, such as a Hiniker 6000 with shovel-like steel points, pulls the soil from the center of the rows onto the soybean plants. Doing this at the V2 growth stage covers the fissures on the stem, which is where the adult gall midge lays its eggs,” he explains. “Covering the plant at this stage is scary as the plants are so small, but our research shows it can save a considerable amount of yield in high-pressure situations. A few growers have mentioned they used the tactic through an interrow cultivator at high speeds to throw the soil on the base of the plant.”
In fields with high soybean gall midge infestations, the team compared soybean yields in hilled and non-hilled rows, resulting in a 95% difference. In one county, they recorded the lowest soybean yield at 2.2 bushels per acre with no hilling to 46 bushels per acre in the hilled rows.
Mowing research was conducted in Nebraska and Minnesota, also with varied results between sites and years. They mowed the vegetation along field edges to reduce the amounts of available moisture, which adult midges need as they move from the over-wintering sites to the soybean field. The team believes that the mixed results could have been influenced by plant height prior to mowing or environmental conditions when adult midges emerged.
Keeping Tabs and Getting the Word Out
Annual survey efforts across the region detected soybean gall midge on an additional 3.9 million acres at the county level last year, for a total of 19.2 million acres affected. McMechan notes that several of the new detections were on sweet clover, a host plant for the soybean gall midge. Sweet clover can be used as a cover crop, but most of the gall midge detections were in ditches next to soybean fields, or in pastures and CRP acres.
The website, www.soybeangallmidge.org, has had more than 14,000 unique visitors from all U.S. states and 72 countries. Farmers can sign up to receive notifications through the Soybean Gall Midge Alert Network, which can be done on the website. Subscribers to the alert network increased from 452 in 2021 to more than 600 in 2024. Because of the alert system, some growers reported successful insecticide applications, demonstrating the value of these timely notifications.
The larger NCSRP project includes research on other pests as well as the soybean gall midge. Project objectives include finding easier scouting methods for stink bugs, testing insecticides for soybean aphid effectiveness and searching for aphid-resistant soybean varieties, and learning more about the recently discovered soybean tentiform leafminer.
Other Resources:
Soybean Gall Midge Alert Network – website
Soybean Gall Midge Research Update – YouTube video, April 2024
Nebraska Research is Gathering Data on Newest Soybean Pest – SRIN article
Studying the Cold-Hardiness of the Soybean Gall Midge – SRIN article
Getting to Know – and Manage – Soybean Gall Midge – SRIN article
Identifying Soybean Gall Midge Management Opportunities – SRIN article
Published: Jul 28, 2025
The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.
