Funded by the Illinois Soybean Checkoff
Unwelcome Guests What Pests are Lurking in Your Soybean Fields? By Mace Thornton
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The dectes stem borer larva can be seen inside the soybean stem. Agronomists recommend a robust scouting program to determine whether control programs are worth the cost.
either Nick Seiter nor Kelly Estes has ever come eye-to-antenna with an adult gall midge fly in an Illinois soybean field, nor have they encountered it in its slimier orange larval stage. But if they ever do, the dreaded soybean pest will know it has met a worthy opponent. The damaging soybean pest isn’t the only potential crop-muncher on the minds of Seiter, a University of Illinois Extension Crop Entomologist, or Estes, the state of Illinois’ Ag Pest Coordinator. The two scientists told soybean farmers gathered for the Soybean Summit that they are also surveilling other members of the soybean-loving insect kingdom, such as the dectes stem borer, the green clover worm and the bean leaf beetle. Overall, the researchers noted higher pest populations in some areas of the state in 2023, but nothing so major as to present a significant yield challenge. And each of those situations was controllable with timely pesticide applications. But the best pest news of 2023 had to be the fact that the destructive gall midge was not documented as present in Illinois. Of all potential soybean pests, the gall midge rep-
A PUBLICATION OF THE ILLINOIS SOYBEAN ASSOCIATION
resents one of the biggest potential perils. Although, according to Seiter, the pest has not yet been spotted in Illinois, neighboring states such as Missouri and Iowa – fields as close as 100 miles away — are already midge battlegrounds. Soybean farmers in western Iowa and parts of Nebraska have encountered severe economic losses resulting from early plant death. “The gall midge is a little fly larva,” said Seiter, who also teaches in the University of Illinois Crop Sciences Department and studies pests of both soybeans and corn. “It gets in behind the epidermis of the soybean stem, and usually there are a lot of them. It's not just one back there feeding; it's maybe dozens of them, and if you have a severe enough infestation, they cause the plants to die early.” Seiter told the farmers the gall midge invades fields around June or July, and damage progresses through the season. Loss from the pest is devastating and can be confused with the soil-borne fungal disease sudden death syndrome. Although his work also includes research on corn rootworms and alternative
(See Unwelcome Guests, page 16)
February 2024
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