Soybean gall midge research underway06/25/2019 | Crop Production Research, Soybean News
By Carol Brown, ISA environmental communications specialist
Not much was known about the soybean gall midge beyond the fact that it loves to eat soybeans and it is only found in four Midwestern states, including Iowa. But researchers are feverishly working on several levels to get ahead of this destructive pest.
Erin Hodgson, an Iowa State University (ISU) Extension entomologist, is a lead researcher in Iowa on the pest that brings both excitement and anxiety for researchers — and mainly anxiety for farmers.
This summer Hodgson and others are studying this fly to learn more about it to eventually save soybean fields from destruction.
“I have a student who is helping me set up adult emergence cages in four western Iowa locations,” Hodgson said. “We began monitoring last week nearly daily. Last week we captured our first adult in northwestern Iowa and yesterday we captured a couple adults in Griswold.”
Hodgson spoke about the gall midge at the Iowa Soybean Association (ISA) Farmer Research Tour in February. She said the first report of the pest was in Nebraska in 2011 and it has since been reported in South Dakota, Minnesota and Iowa. “Finding this fly has changed the direction of my career,” she said.
The pest is so new, researchers are scrambling to learn as much and as quickly as they can. Entomologists in Nebraska recorded soybean field loss from 20 to 100 percent, and it doesn’t take many midges to kill a soybean plant, Hodgson said.
The adult gall midge is not the life stage that impacts soybeans, she said, but of concern are the eggs laid on the stems near the soil line for the next generation. The gall midge’s bright orange larvae, or maggots, are located at the base of the main stem and can be seen by the naked eye.
“The maggots are feeding on the inside of the plant and once they get inside it’s difficult to manage. There aren’t a lot of systemic products available to us for the soybean plant right now,” said Hodgson. “One avenue would be adult control, so they don’t get a chance to lay eggs.”
Hodgson and her team will continue to monitor for adults this summer and then make some insecticide applications and potential management strategy recommendations, she said.
On-farm insecticide research
The ISA On-Farm Network® is also conducting research on the gall midge in southwest Iowa, where evidence was found last year. The On-Farm Network team is studying insecticide application timing, rates and frequency for best mitigation results.
“Approximately eight farmers in southwest Iowa who saw the gall midge in their fields last year have volunteered to participate in the field trials,” said Scott Nelson, On-Farm Network director. “We are working with Syngenta and Valent to test two insecticides. We hope that our on-farm research will help Erin’s efforts as a supportive project.”
The protocol of the trial is spraying only the perimeter of a field in sections with an early treatment, a late treatment, a two-pass application as well as a control section where there is no insecticide application. The research team will start the first spray application in early July, likely next week, Nelson said. This is the first year of this study for the ISA On-Farm Network. The protocol can be found on the ISA website.
The layers of research are mounting the siege on the gall midge. Hodgson’s work is exploring the fly’s emergence and concentrated testing of insecticides to find out how to reach the larvae. The On-Farm Network research is conducted at the field scale on actual farms. These efforts, combined with work being done in Nebraska and other states in the region, are building knowledge on how to suppress the destructive activity of this pest and saving soybean fields from loss or complete destruction.
Contact Carol Brown at firstname.lastname@example.org.
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