Soybean disease can be difficult to diagnose from the road, but they can also make it even more difficult to manage profitably without knowing exactly what is causing the problem.
That’s why researchers with the University of Nebraska-Lincoln’s Soybean Pathology Lab are taking their work beyond small research plots and into farmers’ fields, examining how diseases, varieties, seed treatments and environmental conditions interact on a field-scale level.
“This is actually part of the Nebraska On-Farm Research Program, where we try to do larger-scale things,” says Dylan Mangel, Extension soybean pathologist at the University of Nebraska.
One of those trials is in Mead, Nebraska, where researchers are evaluating two soybean varieties with and without a seed treatment in a field with a history of high sudden death syndrome (SDS) pressure.
“We have two pivots here, and the trial runs all the way across the whole field,” Mangel says. “We’ve got four treatments, which is two different varieties, and then with and without a seed treatment.”
When More Water Isn’t Always Better
The field provided an unexpected look at how environmental conditions can influence disease development. Early-season rains created wet soils, conditions Mangel says can increase the potential for disease.
“When we’re going into cooler, wetter soils, the potential for disease is higher,” he says.
Researchers intentionally included a seed treatment designed to help protect against SDS. From the air, differences in the plots became visible, with treated soybeans maintaining greener foliage longer. But irrigation created another twist.
“In the irrigated areas, we started to see the variety dry down faster. We started to see more sudden death syndrome symptoms,” Mangel says. “So that extra water spurred on those symptoms.”
The difference was especially visible from above. Dry corners of the field remained greener while irrigated areas showed more disease symptoms and moved toward maturity more quickly.
“Water doesn’t always mean better,” Mangel points out.
The trial is one of nearly 30 studies being conducted by the Nebraska soybean pathology team this year.
“We have seven different locations, almost about 30 different trials that we’re running this year,” says Bhanu Dangi, field research technologist with the University of Nebraska-Lincoln Soybean Pathology Lab.
Those locations allow researchers to examine disease and management decisions under a range of conditions. Some sites are irrigated, giving researchers the ability to manipulate water availability within individual trials.
“There is a lot of variation,” Dangi says. “Some of our sites are pivoted, and because of that, we are able to turn on the specific trials and close some others. And so we can control a lot of environment in this specific location.”
Don’t Spend on Disease Management You Don’t Need
With farmers scrutinizing input costs heading into 2027, seed treatments and other disease-management products are under a closer microscope. Mangel says the key isn’t simply determining whether a product works. It’s determining whether the disease pressure is high enough to justify the expense.
“Seed treatments can pay if you’re in the right conditions, if you have disease,” he says. “No management product is going to pay if you’re on a field without the disease.”
Magel says that makes diagnosis the first and most crucial step.
“I always tell growers, step one, figure out what you’ve got in that field,” Mangel says. “Management is going to be disease-specific and it’s most likely to pay if you’re in a high-disease-pressure field.”
That can be more complicated than it sounds. Several soybean diseases — and even some non-disease issues — can produce similar symptoms.
“We’ve got a lot of things in soybean that’ll cause that similar sudden death syndrome symptom,” Mangel says. “We’ve got brown stem rot, we’ve got triazole injury from not a pathogen at all. We’ve got sudden death. Red crown rot makes similar symptoms.”
The distinction matters because a treatment designed for one problem may not provide protection against another.
Free Testing Helps Identify Hidden Yield Robbers
Nebraska researchers are also working to help farmers determine what is happening below ground.
Olivia Dooley, a second-year master’s student in the UNL Plant Pathology Soybean Lab, is focused on soybean cyst nematode (SCN). Nebraska growers, crop consultants and agronomists can submit soil samples to the lab to determine whether SCN is present and, if so, at what level.
“I think one big thing that Nebraska is really great about is we have a testing program where the growers, crop consultants, agronomists, anybody in the state can send in soil samples to our lab and then we can actually tell them do they have a SCN their field and then at what level, too,” says Dooley. “And the Nebraska Soybean Board sponsors that, so it’s completely free for anybody to send those in.”
That information can then help farmers make more targeted management decisions.
“What we can learn from that is, OK, is this field bad? Should we use a seed treatment here, or should we save it and use it somewhere else in a location where it’s more needed?” he says.
SCN is particularly challenging because it can rob yield without creating obvious above-ground symptoms.
“I think there’s a lot of small contributors,” Mangel says. “Soybean cyst nematode, for example, is one of those. You can lose significant yield with no noticeable symptoms.”
Red Crown Rot Moves Closer to Nebraska
Another disease researchers are watching closely is red crown rot, which has been emerging and spreading across parts of the Midwest. As of the time of the research, Nebraska researchers had not confirmed red crown rot within the state.
“We have not found it in the state yet,” Mangel says. “I’m sure there’s a high likelihood that it’s already in the state. We hear people talking about it. We just haven’t been able to get those samples in our hands and verify it in a lab.”
Researchers are studying fields near Nebraska’s border in an effort to better understand the disease before — or if — it becomes established in the state.
At this point, there are still major questions surrounding red crown rot, including how it spreads and how quickly it can move.
“We really don’t know exactly how it’s spreading,” Mangel says. “We don’t know how quickly it’s going to move.”
For farmers scouting fields, one of the biggest challenges is that red crown rot can look much like SDS.
“That’s the hard part, the unfortunate thing,” Mangel says. “It’s going to look from the road just like sudden death syndrome.”
There is one visual difference. With SDS, affected soybean plants tend to drop their leaves. With red crown rot, leaves may dry down but remain attached to the plant.
Still, confirming the disease requires getting closer to the plant.
“It’s a lot of getting out checking fields that look like sudden death for the actual red crown rot on the base,” Mangel says.
Researchers are looking for small, spherical structures around the base of the plant that are a deep scarlet red. Finding those structures can confirm red crown rot, but they aren’t something farmers are likely to identify from the cab of a combine or from the road.
Red Crown Rot Can Spread Quickly
Dooley recently traveled to Illinois to learn more about red crown rot and saw firsthand the potential severity of the disease.
One grower she encountered had initially found the disease in an isolated pocket of a field. After rotating to corn, the grower planted soybeans again, only to see the problem spread across the field.
“One year he just had it in one kind of pocket of the field,” Dooley says. “Rotated out of soybeans and planted corn, and then the next time he planted soybeans it was just spread throughout his entire field instead of just that one isolated pocket.”
The grower reported a yield loss of about 40 bu. per acre. For that farmer, the lack of an effective solution raised a difficult question about whether to continue planting soybeans in the affected area.
“He told us he was just going to keep planting corn there, not plant soybeans,” Dooley says.
Cracking the Code for Yield Potential in Soybeans
For Mangel, the goal of this research extends beyond managing individual diseases. It’s about finding the collection of small yield losses that can add up to a significant difference across an entire field.
“I think there’s a lot of yield potential in soybeans, and we’re not cracking it,” Mangel says.
He believes farmers may have become accustomed to a certain yield level because some of the factors limiting production are difficult to see.
“I think a lot of growers have just accepted that the yield level I’m at might be what we can do in this field,” Mangel says. “And I think there’s actually some yield on the table.”
As researchers better understand diseases such as SDS, SCN and red crown rot, along with the interactions between varieties, seed treatments and environmental conditions, Mangel sees potential for continued yield gains.
“With new technology, with new varieties, new seed treatments, new traits, I think we’re going to see an increase in soybean yields,” he says.
For farmers trying to squeeze more production from every acre, that means some of the biggest opportunities may not be visible from the road or even from the combine.
“Don’t sleep on soybeans,” Mangel says.
