With harvest just around the corner, it’s easy to become complacent with crop scouting. Soybean gall midge, a relatively new pest issue, proves scouting is critical until combines are in the field.
Shortly after July 4, Wayne Martin a farmer from Shelby, Iowa started having plants along the field edges that were dying. He had a drone up looking for green snap corn and noticed another soybean field with significant damage. Together with his seed dealer, they began to investigate what was causing the damage. Martin discovered he had soybean gall midge upon scouting direction from Allison Roberts, a plant pathologist at Iowa State University.
Soybean gall midge, also called orange gall midge, is making its way across the corn belt, now found in Nebraska, Iowa, South Dakota and Minnesota. Here’s what you need to know:
How Does Soybean Gall Midge Spread? “The fly comes in and it deposits the eggs into the stems just above the ground,” Martin explained to AgriTalk host Chip Flory. “Then that eventually turned into a larva and they apparently are just having a free lunch in there. Then, eventually that they turn back into a fly and the cycle is repeated again.”
What Do The Larva Look Like? “The young ones they start out almost clear and very, very short,” Martin said. “It's hard to see them with the naked eye.” Then as a the larva ages, they turn to a pink, and then a dark orange or red color, but they're still fairly short. “When you find as many as what I've seen in some of my stands a month ago, we can have as many as 40 in one stem,” Martin said. “It’s pretty sickening to see that.”
What Does Soybean Gall Midge Do To Plants? The fly lays eggs in the stem of the plant. “Oftentimes we'll find a pin prick. And I guess we're assuming that that's where the fly deposited the eggs,” Martin explained. “Then that's where that gall is formed. That's just basically an enlarged portion of that stem that is caused by hormones changing within that plant. As the [larva] keep eating in there, it just chokes that circulation going up and down that stem. And above that gall, the plants will die. It's a fairly quick process to death, especially the numbers that we were seeing.”
How Can You Find It? Scouting is the only way to find this pest. At a certain point the plants will die, so it’s not uncommon to see dead soybeans at the edges of fields that have this problem. However, in early stages they look fine. “The bad part is that even apparently healthy plants, they can look just fine but you can take your hand and swipe across and you just hear them snap,” Martin explained. “You inspect those plants and guess what? They’ve got the damage also.”
How Widespread Is This Pest? Soybean Gall Midge has been spotted in Nebraska, South Dakota, Iowa and Minnesota. On Miller’s farm the damage started out in 10ft swaths along the edges of the fields, but recently he’s notices 60 to 80 ft. swaths to near 100% death loss from the midge. “I'm not talking a small area and I'm talking maybe half mile long, and then it tapers off as you go towards the center of the field,” Martin said.
Can It Be Treated? Because adult flies do not eat, they only reproduce, he says any kid of residual chemical control is going to very difficult. He says this pest will to be treated systemically, but there’s no control method at this point. “We’re signed up with Iowa State [to do] some in depth testing next year,” he said. “We're going to try and run a maximum rate on a seed applied insecticide, hoping that we can move pretty quickly.”
For more information visit University of Minnesota Extension’s Crop News blog here.