What lies beneath?

For years, the Padgett family knew something was robbing soybean yield in certain fields on their farm in Orrick, Mo., but they struggled to explain why.

The symptoms often looked like drought stress, even in years where moisture was plentiful. Sections of rich river-bottom soil didn’t produce as well as they should. Random patches lagged behind the rest of the field with no obvious explanation.

Eventually, soil testing revealed the culprit: soybean cyst nematode (SCN), a soilborne pest that remains one of the most damaging threats to soybean production and one that researchers say has likely been underestimated across Missouri. Because SCN affects the roots of plants, infested fields may look healthy above ground. It takes a soil sample to determine its presence and level of infection.

“We started seeing nematode problems on these soils 20 years ago,” said Darrel Padgett, who farms with his brother, Dave, and other relatives on their Crabtree-Padgett family farm. “We were experiencing so much yield loss in the soybeans—30% to 40% in some places—and we couldn’t figure out what was going on there until we had some tests done.”

The Padgetts aren’t alone when it comes to fighting SCN, which remains the soybean industry’s No. 1 yield threat more than 50 years after it was first detected in the United States. The microscopic parasitic roundworm, which feeds on the roots of soybeans and other legumes, is estimated to cause $1.5 billion in damage annually across the U.S.

In Missouri, SCN can now be found in every soybean-producing county, causing some $224 million in losses, as indicated by recent research from the University of Missouri’s Jeff Barizon, doctoral student and senior research specialist at the SCN Diagnostics Lab. In a two-year survey, he found SCN eggs in approximately 80% of the 200 Missouri fields sampled, with median levels high enough to contribute to yield losses.

Findings like those are helping drive renewed interest in SCN management among growers, agronomists and researchers. At the same time, new genetics, seed treatment options and testing capabilities are emerging.

For DJ Vollrath, MFA district sales manager, those factors prompted two important questions: What do SCN populations actually look like in farmers’ fields, and are newer management tools making a difference?

To find out, MFA conducted an SCN sampling project this summer across central and northeast Missouri, spearheaded by Ag Experience intern Cash Honeycutt. The project included around 20 fields, including seven sites on the Crabtree-Padgett farm, representing different production environments, from river-bottom ground to upland acres, conventional tillage to no-till systems, and multiple soybean varieties and seed treatments.

Honeycutt collected samples at the first of June, July and August and submitted them to the University of Missouri’s SCN Diagnostics Lab for egg-count analysis.

“You can’t go to a grower field day or an agronomy conference these days without someone talking about SCN as the silent yield robber,” Vollrath said. “So, we wanted to get some real-world data in our backyard, something tangible to deliver back to the growers. And, yeah, we found the nematodes are out there. Lots of them.”

Biology finds a way

The growing presence of SCN is largely related to a gradual breakdown of the natural resistance in PI 88788 genetics that have dominated commercial soybean varieties for decades, said Mandy Bish, MU assistant professor, Extension plant pathologist and director of the SCN Diagnostics Lab. Introduced commercially in the early 1990s, the PI 88788 line is now bred into more than 90% of soybean varieties. Because farmers relied heavily on these genetics year after year, SCN populations have gradually adapted, snowballing into a major resistance problem.

Bish compares the challenge to the weed-resistance issue that developed after years of glyphosate overuse.

“We had our solution; we were done,” she said. “There was very little work done on anything new because we found this genetic resistance source and said we don’t have a problem anymore. Then we used that solution for 30 years and what happened? Biology found a way. That’s why it’s so important to continue the research.”

While the majority of soybeans still contain PI 88788 genetics, newer varieties with Peking-based SCN resistance are now helping fill that gap—particularly in fields with higher nematode pressure. MFA’s MorSoy 3601 variety features the Peking trait, as do several of the Brevant and Asgrow partner brand varieties available through MFA.

Researchers also are watching the development of additional resistance solutions, such as BASF’s Nemasphere, touted as the first biotechnology trait designed specifically to protect soybeans from SCN. The company expects the technology to be commercially available in 2028, pending regulatory approval.

One new tool already showing promise is the seed treatment Victrato, which provides protection against SCN in addition to disease control benefits, including red crown rot. According to Syngenta, its parent company, Victrato’s revolutionary TYMIRIUM technology provides higher potency than any other available molecule on the seed treatment market to target plant-parasitic nematodes.

Samples collected this summer on the Crabtree-Padgett farm showed substantially lower SCN egg counts in Victrato-treated soybeans than those treated with Saltro, an earlier-generation Syngenta seed treatment. The samples were taken from fields planted with MorSoy 3830, a non-Peking variety.

“We can see that Victrato is working, even on ground with higher nematode pressure,” said Brandon Edney, MFA agronomy key account manager who works with the Padgetts. “I believe we’ll see the yield benefits outweigh the cost of the treatment.”

Vollrath said he, too, came away encouraged by results from the summer sampling project.

“Judging by the numbers, across the board, SCN was suppressed where Victrato was used more than the other seed treatments,” he said. “How much impact depends on severity and other factors, but I think that Victrato will be an extra layer of defense. We’ll know more when we see the yield data after harvest.”

However promising those results, Bish cautioned that seed treatments cannot be stand-alone solutions.

“Seed treatments are not a silver bullet,” she said. “They have to be part of an integrated program that relies on rotation as the key management practice. And rotation doesn’t just mean crop species but also resistance sources. What I like to suggest is planting PI 88788, corn, Peking, corn, PI 88788, corn, and so on. There’s a lot of concern that the Peking resistance will break down, making stewardship critical. Just be mindful of rotating it with something else.”

Controlling winter annual weeds should also be part of the management program, Bish added. They can serve as alternative hosts for SCN and increase populations, even when soybeans are absent.

For the Padgetts, years of experience battling SCN have reinforced those lessons. Fields that spent too many consecutive years in soybeans often became the ones where SCN pressure was most severe.

“Some of our worst fields are the ones we don’t rotate enough,” Darrel said. “I blame part of the problem on our management. We didn’t want to put some of our marginal ground in corn, so we planted too many back-to-back years of soybeans. We’ve learned you’ve got to rotate away from soybeans into a non-host crop. And we’re hoping this new seed treatment will make a difference, if it shows us the results we think it will. But from all the things I’ve seen, you probably won’t be able to eradicate soybean cyst nematodes. You just have to learn to manage them.”

Early planting raises the stakes

The increased focus on SCN also coincides with a trend among growers to plant soybeans earlier to capture higher yields. The Padgetts are among them.

“Last year was the earliest we’d ever planted corn and soybeans in our life,” Darrel said. “It was also a year we set records on yields for both crops.”

But earlier planting can also create conditions favorable for both SCN and sudden death syndrome (SDS). Researchers believe the longer growing season allows additional SCN life cycles to develop while cool, wet planting conditions can favor SDS infection.

“The earlier you plant, the more generations of SCN are likely to complete, which means egg population densities can quickly build up,” Bish said. “And, as the nematode feeds on the roots, it can open avenues for disease to take hold earlier in the season.”

Bish said demand for testing through the SCN Diagnostics Lab has more than doubled in recent years, driven by increased awareness of SCN as well as new management options entering the marketplace.

“Even five years ago, this was a tough topic because no one was bringing any answers to the table,” Bish said. “Now, we’re seeing new genetics, treatments and other solutions that are having success.”

The current lab infrastructure has struggled to handle the increased volume, but Bish and her team will soon move into a new, state-of-the-art SCN Diagnostics Lab with significantly greater capacity for testing and research. Housed in the university’s East Campus Plant Growth Facility, the new 3,200-square-foot lab will support both immediate needs and longer-term research.

“Our goal is that we will be able to handle over twice as much at the new lab,” said Bish, who expects a spring grand opening. “I really think it’ll be probably closer to three to four times as much as what we’re handling now, allowing us to more precisely map nematode populations in farmers’ fields. It will also help remove bottlenecks so that we can more rapidly screen products for other companies, work with breeders to identify new sources of resistance and look at multi-pronged approaches to manage SCN.”

Know your numbers

For now, Bish encourages growers to take advantage of the existing Diagnostics Lab resources by sampling fields to determine their SCN numbers.

“Fall is a good time to test soybean fields because numbers should be at their highest after harvest,” Bish said. “You can also test in the spring because the eggs will be in a cyst that should survive the winter. Sampling in both the spring and the fall can help you understand how your management’s actually working.”

Growers also have an added incentive to sample this fall. Missouri farmers can submit four samples for free SCN egg count surveys through a program funded by the Missouri Soybean Merchandising Council. Additional tests are $25 per sample. More information about the program and SCN management resources is available at scndiagnostics.org.

If SCN is a problem in your fields, MFA agronomists can help growers with a plan for 2027. Visit with your local MFA representatives or online at mfa-inc.com.