For North Dakota farmer Jay Myers, this year’s soybean harvest delivered a frustrating reminder: Soybean cyst nematode (SCN) can take a bigger bite out of yield than growers realize, especially when the varieties and technologies they’ve relied on for years start losing their effectiveness.
Dry conditions made the problem more apparent in some of Myers’ fields this season. Yields ranged from about 20 bushels per acre in the hardest-hit fields to 60 bushels on some irrigated ground.
“That old cyst nematode showed its face on some of our drier fields here earlier this summer,” Myers said during an AgriTalk Farmer Forum conversation. “It snuck up on everybody, you know, faster than we thought.”
A Widespread Problem
The challenge facing Myers is part of a much larger, national problem. SCN occurs in every major soybean-producing state,
and many growers have it in their fields without realizing it’s impacting yield.
In Illinois, SCN has been found in all 102 counties. In Iowa, it occurs in all 99 counties. Greg Tylka estimates that more than 75% of Iowa soybean fields have SCN at yield-reducing levels.
“I tell my farmers here there’s a three out of four chance any field they grow soybeans in has SCN,” says Tylka, nematologist and director of the Iowa Soybean Research Center at Iowa State University.
Pioneer documented the pest’s broad distribution in a 2021 survey of 439 soybean fields across Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Ohio and Wisconsin. The company reported that more than 80% of the sampled fields had some level of SCN infestation, while 27% had populations capable of causing heavy to severe crop damage.
For farmers who don’t believe they have SCN in their fields, Tylka says to consider corn yields versus soybean yields. “If your corn yields are going up but soybeans are stagnant, that’s a sign SCN could be a problem for you.”
The financial consequences can add up quickly, as Tylka notes that a 30% yield loss in an SCN-infected field is common. In a field capable of producing 70-bushel soybeans, that amounts to a 21-bushel hit per acre. At $11 per bushel, that represents $231 per acre in lost revenue.
SCN is estimated to cause about $1.5 billion in soybean yield losses annually across the United States.
Growing Concern in North Dakota
Chris Johnson, an agronomist and certified crop adviser with Central Crop Consulting, works with farmers along the North Dakota-Minnesota border. As soybean acreage expands in North Dakota, he sees SCN as an increasingly important concern.
USDA data shows North Dakota soybean acreage has more than tripled since 2000, compared with just 17% growth nationally. Despite that expansion, state yields have plateaued at approximately 35 bushels per acre over the last decade — roughly 35% below the national average of 53 bushels per acre.
High-pH, sandy soils can be particularly challenging. When dry weather compounds in-season stress, soybean plants have less ability to compensate for root damage caused by nematodes.
Johnson saw that combination in many fields this season as moisture became scarce. In fields with high SCN populations, he reports yield losses of 10 to 20 bushels per acre were common. Many farmers, not knowing they had SCN in their crop, suffered sharp yield losses.
“You can live with it and live with it, and all of a sudden you can just get clobbered,” he says.
Traditional Resistance Is Losing Ground
For years, soybean growers have fought SCN by relying heavily on varieties with resistance derived from PI 88788, a genetic source that has helped keep SCN populations in check. But the nematode has overcome that technology in many fields, making it less effective, notes Tylka.
“Mother Nature has an innate ability to adapt, and adapt she has,” Tylka says. If farmers don’t diversify their SCN management strategies, he warns, yield losses to SCN will continue.
Researchers estimate that, if current management practices remain unchanged, PI 88788 resistance could provide only about 40% control of SCN by the end of this decade.
Limited Options for Peking Varieties
Growers are looking for alternatives to PI 88788, including varieties with Peking resistance. Promising yield results from local test plots have caught Myers’ attention, and he wants to try the technology.
“In local test plots, varieties with the Peking trait yielded about 56 bu./acre (on dryland acres), versus 36 bu./acre without it — a 20-bu./acre difference,” he reports.
The challenge is for the 2027 growing season, he expects to have only about three Peking-based varieties to choose from.
“You got to have some other traits in there that can also handle iron deficiency chlorosis (IDC) and some other problems we have,” Myers says. “So, it kind of limits what we can do.”
He plans to keep evaluating Peking varieties, looking for variety options that deliver the right combination of SCN resistance and agronomic performance.
Testing and Sampling Are Invaluable
Tylka recommends farmers collect soil samples this fall and send them to a diagnostic laboratory that specifically tests for SCN.
Some state soybean organizations offer free SCN testing, though programs vary from year to year. The SCN Coalition is a useful place to find testing information and management resources, including guidance on available state programs.
Sampling technique matters, too. SCN populations can be concentrated in localized field hot spots, meaning a sample taken from the wrong area may miss the problem.
Integrated Management Approach
Once SCN is identified, farmers need more than one tactic to address and manage it. The most effective approach, Tylka notes, combines resistant varieties, crop rotation, population monitoring and, when appropriate, seed treatments.
If feasible, Johnson recommends considering a break from soybeans for a couple of years in fields with significant SCN pressure. Rotating to nonhost crops deprives the nematode of the soybean roots it needs to reproduce.
Corn is the most common nonhost crop used in soybean rotations. Small grains and sorghum can also be options, depending on the farm’s production system.
Tylka explains that SCN eggs hatch over time, but the juvenile nematodes need a suitable host to continue developing. When corn is planted instead of soybeans, some juveniles hatch but cannot reproduce, allowing populations to decline.
The reduction varies with field conditions and other factors. Tylka says SCN egg numbers can drop by roughly 5% to 10% in some situations and by as much as 50% in others.
Not every crop provides that benefit. Dry beans, clover and hairy vetch can host SCN, so growers should check a rotation crop’s host status before assuming it will help reduce populations.
Seed treatments may provide additional protection, Tylka says, but they shouldn’t be viewed as a stand-alone solution for severe infestations.
The SCN Coalition’s Soybean Cyst Nematode Management Guide, originally developed by the coalition and recently updated and reissued by the North Central Soybean Research Program, offers additional guidance.
New Technology on the Horizon
While growers work to diversify existing management practices, the industry is developing additional tools to combat SCN.
BASF Agricultural Solutions is developing Nemasphere, a biotechnology trait designed specifically to target soybean cyst nematode. Unlike conventional resistance sources such as PI 88788 and Peking, Nemasphere uses a transgenic trait that produces a Cry14 protein in soybean plants.
According to Hugo Borsari, BASF vice president of business management for seeds in North America, the protein targets SCN when the nematode feeds on developing soybean roots. BASF reports that the technology can reduce SCN populations by up to 60% and is intended to help protect yield potential compared with varieties relying solely on traditional resistance traits.
“We’re not just adding yield; we’re giving farmers access to the yield potential SCN has taken away,” Borsari says.
BASF anticipates that Nemasphere could reach the market as early as 2028, but Borsari says that is a projected timeline only.
For now, farmers can’t wait for a new product to address SCN, adds Tylka. He says testing for it this fall can establish a baseline, while variety selection and crop rotation decisions can help reduce the risk of continued yield losses in 2027.
