The SCN Coalition wants soybean growers and their advisors to consider the impacts soybean cyst nematode (SCN) can have on their bottom lines if left unmanaged. Developing a plan to actively manage SCN—the No. 1 yield-grabbing pathogen of the soybean crop in North America—protects soybean yields and profitability.
SCN is the most damaging pathogen of the soybean crop for several reasons. In states like Illinois where SCN has been established for decades, it has become resistant to the most common source of resistance known as PI 88788. It’s been found in every county in Illinois and is estimated to be present in 70% to 80% of fields.
Research shows yield loss as SCN populations increase on varieties with the PI 88788 resistance source.
This data is from 15 years of variety trial experiments in farmers’ fields in Iowa.
Research conducted by University of Illinois scientists confirmed that SCN populations in Illinois are increasingly becoming resistant to PI 88788. A 1990 study found that 34% of SCN populations throughout the state had greater than 10% reproduction on PI 88788. A similar follow-up 2003 study showed 70% of SCN populations had greater than 10% reproduction on PI 88788.
Therefore, one can conclude the increase in SCN reproduction on PI 88788 resistance doubled in 13 years in Illinois, and the erosion of PI 88788’s effectiveness almost certainly continued since 2003 and continues today.
As a result, The SCN Coalition developed an “active management” strategy.
SCN Management Tools
Active management of SCN includes these four tools:
  • Test fields to know nematode population densities
  • Rotate SCN resistant varieties
  • Rotate to non-host crops like corn
  • Consider using a nematode-protectant seed treatment
Testing fields every three to five years is a good way to know SCN populations and select the tools to minimize economic impact. It’s also important to keep in mind that resistance to PI 88788 is complex, and different varieties with the same source of resistance often differ in their effectiveness to control SCN populations. If able, rotate between PI 88788 and Peking varieties.
Controlling the First Generation of Nematodes
If soil sampling determines nematodes have become resistant to the resistance, consider incorporating a nematode protectant seed treatment, which can prevent the first generation from becoming a problem.
SCN can complete a life cycle in about four weeks, and SCN reproduces much quicker during hot and dry growing conditions, like many soybean growers faced in 2020. In a traditional corn-soybean rotation, it’s highly possible that in 2022 many of the fields that grew soybeans this year could have increased levels of SCN and increased yield loss.
SCN can complete three to six life cycles each growing season. Fewer life cycles during the growing season can lower the level of reproduction.
The SCN Coalition has compiled a chart of nematode-protectant seed treatments currently available. The chart includes crops, targeted nematodes, active ingredient and mode of action. Click here to view the chart.
Unlike other diseases like sudden death syndrome that are noticeable when scouting fields, a soybean field can have up to 30% yield loss from SCN without visual above-ground symptoms. Therefore, don’t evaluate the success of a nematode protectant seed treatment visually.
Similar to how weather plays a factor in how quickly SCN reproduces, it also plays a role in the effectiveness of a nematode seed protectant. In addition to warmer conditions, SCN favors sandier soil and soil with a pH of 7 or above.
Research is ongoing to determine the effectiveness of nematode seed treatments, and we know it’s not the silver bullet to managing SCN. But it’s certainly a useful tool in an active management strategy for combating the No. 1 yield-grabbing pathogen of the soybean crop.
More Information for Advisors
State-specific advice is available from university experts on The SCN Coalition’s website. For advice specific to Illinois, click here. Visit the Coalition’s new “Let’s Talk Todes” video series, where growers and experts share best management practices. You can also follow the Coalition on Facebook and Twitter.

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About the Author: The SCN Coalition

The SCN Coalition is a public/checkoff/private partnership formed to increase the number of farmers who are actively managing SCN. Our goal is to increase soybean farmers’ profit potential and realize higher yields. Partners in The SCN Coalition include university scientists from 28 states and Ontario, grower checkoff organizations including the North Central Soybean Research Program, United Soybean Board and several state soybean promotion boards, and corporate partners including BASF, Bayer, Growmark, Nufarm, Pioneer (Corteva), Syngenta, Valent and Winfield United.