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Research Highlights

Research Highlights
Soybean Gall Midge Battle Continues in the Midwest

By Carol Brown

Soybean gall midge is a newly discovered pest making its presence known in fields across several Midwestern states. Scientists and farmers alike are concerned about its capacity for plant destruction and how to stop it.

Justin McMechan, an assistant professor of entomology at the University of Nebraska-Lincoln, is working with the farming community and his colleagues in four states to learn all they can about this yield-robbing pest.

The soybean gall midge was first identified as a new species in Nebraska fields in 2018. It has increased with each cropping season and moved across state lines. Insect researchers scrambled to get ahead of it and are making strides in learning about this fly’s lifecycle and habits.

“We were awarded an emergency grant from the North Central Soybean Research Program (NCSRP) in 2018,” McMechan said. “With this grant, we were able to track adult midge emergence. I captured adults in the fall of 2018 at the Eastern Nebraska Research and Extension Center near Mead, which led to the identification of the soybean gall midge as a new species.”

Research has revealed initial details about the soybean gall midge fly species. Around the early V3 stage of the soybean plant, the adult midge lays eggs on at the base of the stem in natural cracks that form as a result of stem expansion. The hatched maggots use the stem as a food source. The maggots drop off the plant and burrow into the soil where they pupate. The adult midge emerges from the soil later in the summer. However, the adult does not feed on soybeans and it is assumed that they only consume water.

The midge invasion starts at the edge of a field and works toward the center. Confirming a gall midge infestation takes close examination as visual plant damage looks similar to other diseases and pests.

The entomologists were able to expand their research with several projects funded by the United Soybean Board (USB) and NCSRP and are going full steam ahead.

“In 2019, we set up sites at 27 field locations in Nebraska, Iowa, South Dakota and Minnesota, to capture and track adult midge emergence in the spring, which was successful,” McMechan said. “We’re also looking at host-plant resistance, which is appearing to be a fundamental component to good management. If we can identify resistance especially in combination with a number of management practices, that will help immensely.”

The scientists are looking for answers from many angles including insecticide treatment and timing, and management practices to slow population reproduction. Last year, insecticide tests did not completely eliminate the gall midge with the best results improving soybean yield by 50 percent compared to untreated fields.

“What we learned last year is that it is unlikely we will have a single tactic that provides an acceptable level of control for soybean gall midge,” McMechan said. “Now we’re trying to push multiple cultural and chemical control strategies together to treat infested areas. We know it is not a whole-field scenario, so we’re looking at edge-of-field treatments and trying to understand how much of the area needs treated.”

Farmer input is needed
Two parts of the team’s research requires direct input from farmers. Last year McMechan set up the Gall Midge Alert Network. Farmers can send their contact information to him to receive alerts — just like a severe weather notification — regarding gall midge emergence notices and other timely information.

“This system allows us to quickly push information to the farmer and use multiple platforms – text message, email or a phone call – to make sure they get the message,” he said. “We have about 225 people from five or six states signed up.”

This year, the team is planning to send information farmers in 12 states, which can help them identify if other states may be seeing the gall midge. This will help them focus on specific areas and let research personnel know to be on the lookout.

“The farmers in Nebraska have been more than cooperative,” McMechan said. “Often it’s them asking me if we could do some research on their land. They are helping us identify good sites for research and willing to put their farms at risk to do so.”

Multi-state work
The project is focused heavily in the four states where the soybean gall midge has been identified. They will monitor more than 30 sites for emergence, conduct tests on over 760 soybean lines for genetic variability with resistance or tolerance of the pest.

Other studies include changes in planting dates, tillage, or mowing round fields as well as the insecticide work. McMechan said the gall midge symptoms vary geographically, so sharing information across state borders is important.

“For example, even though the insect is called a ‘gall’ midge, in Nebraska we don’t usually see gall formations on the soybean plant until we travel further north,” said McMechan. “Symptoms are varying, especially with weather and management conditions. Last year, South Dakota had a very different year with atypical weather patterns and there is a lot of tillage use in Minnesota. We’ll look at all of these variables to find differences in Gall Midge behavior so we can win the battle.”

Resources:
Scouting for Soybean Gall Midge (video), Justin McMechan, University of Nebraska – Lincoln
New Soybean Pest in Iowa: Soybean Gall Midge, Iowa State University Extension and Outreach – Integrated Pest Management, 2018
Soybean Gall Midge: An Emerging Pest of Soybeans, University of Nebraska – Lincoln, CropWatch, 2019
Soybean Gall Midge in Minnesota Soybean, University of Minnesota Extension, 2019

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