Soybean Cyst Nematode Resistance Management: A Layered Strategy

The mega-threat of the microscopic soybean cyst nematode (SCN) looms large over U.S. soybean fields. SCN’s insatiable appetite for soybean roots makes it the No. 1 yield-reducing soybean pest routinely causing more than $1.5 billion in annual losses.¹ Soybean cyst nematode claimed close to 90 million bushels in 2024 alone.²
The good news is that you don’t need an agronomy degree to keep SCN in check in your soybean fields. Learn how a multi-faceted approach that includes soybean cyst nematode resistant varieties, crop rotation and seed treatments can help you manage SCN.

Soybean cyst nematode management strategies

No single management solution can effectively combat SCN. Instead, a layered approach, hitting the pest from several angles, is going to be the most effective strategy.

1. Use crop rotation to combat SCN in soybeans

SCN is constantly evolving to outmaneuver your soybean pest management efforts. As many as six generations of SCN can cycle through your soybean fields in a single season.³ That means diligent rotation of crops, and soybean genetics, are crucial for breaking the lifecycle of SCN.

Rotate resistance sources, not just varieties

Since soybean cyst nematode populations are increasingly able to overcome soybean varieties bred from PI88788 and Peking SCN-resistant sources, you should consider rotating among varieties based on different resistance sources. Rotating varieties also keeps currently functioning sources of resistance in production longer, giving researchers a longer runway to introduce novel soybean varieties to combat SCN, such as BASF’s Nemasphere trait.

Rotate to non-host crops to combat SCN

In addition to rotating resistance sources, consider rotating the crops you’re growing in soybean fields as well. Appropriate rotations can include alfalfa, corn, oats, sorghum and wheat. Since none of these harbor soybean cyst nematode, they can help break the SCN lifecycle. This is especially important if you have SCN counts higher than 12,000 eggs per 100 cc of soil after a non-host crop year or 16,000 eggs after a soybean crop year. You might need to plant a non-host crop for several years in a row. That’s because egg-count reductions vary widely, from as little as 5% per year to as much as 50% per year.⁴

2. Understand soybean cyst nematode resistance ratings

Next, you should spend some time brushing up on the best ways to monitor SCN resistance in your soybean fields. The two key concepts here are HG type testing, which pinpoints resistance sources likely to help you limit reproduction of the specific SCN population in your field, and the female index, which helps you begin estimating SCN volume and potential yield damage it could cause.

HG type testing for soybean cyst nematode

This stands for Heterodera glycines, the scientific term for soybean cyst nematode. The goal of this test is to figure out how different varieties of soybeans grown for their ability to resist SCN are performing compared to one another.⁵ This is important to know because if you continue planting varieties vulnerable to SCN, the pest is more likely to expand its footprint in your fields. HG type testing can be performed by dropping off or mailing about half a gallon of soil to your local university laboratory. During the test, researchers take SCN from your soil sample and grow it in a greenhouse along with multiple plant varieties. If populations are higher on one variety, that can be a clue to avoid that variety the next season because SCN is able to use it to gain a stronger foothold. In other cases, you might discover that SCN successfully reproduced on multiple soybean varieties, which could mean more advanced management strategies are needed in your layered approach.⁶

Using the female index to calculate soybean cyst nematode
The SCN female index is calculated using information from the HG type test.⁷ It involves counting the average quantity of female SCN cysts, which look like little white lemons attached to soybean roots, on a resistant soybean cultivar. Then, they divide that number by the average number of cysts on cultivars without resistance. Finally, they multiply the resulting figure by 100. If your female index is less than 10, resistance is working in your soybeans. If it’s between 10 and 30, resistance is moderate. If it’s 30-60, your crop is moderately susceptible to SCN. And if it’s greater than 60, your crop is rated susceptible. Keep in mind that varieties with a female index up to 50 will still generally yield more than those with higher scores, even when SCN levels are high enough to curb yield.⁸

3. Pair resistant soybean varieties with seed treatments

Combining multiple tactics is the most effective way to support your overall soybean cyst nematode management strategy. To combat SCN resistance, layering protection with seed treatments such as Ilevo^® and SCN-resistant soybean varieties can help your crop get a good start early on with protection against SCN. Ilevo seed treatment also provides protection from sudden death syndrome (SDS).

Experts are available to help you select soybean cyst nematode resistant varieties and make other management decisions to combat the threat of SCN. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.

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Endnotes

1. Iowa Soybean Association. “ISR February 2024: The Fight Against Soybean Cyst Nematode.” Iowa Soybean Association, 1 Feb. 2024, https://www.iasoybeans.com/newsroom/article/isr-february-2024-the-fight-against-soybean-cyst-nematode. Accessed 28 Apr. 2025.
2. Allen, Tom W., et al. “Soybean Disease Loss Estimates from the United States and Ontario, Canada–2024.” Crop Protection Network, 2024, https://cropprotectionnetwork.org/publications/soybean-disease-loss-estimates-from-the-united-states-and-ontario-canada-2024. Accessed 28 Apr. 2025.
3. Tylka, Gregory L. “Soybean Cyst Nematode.” Iowa State University Extension and Outreach, 2022, https://crops.extension.iastate.edu/encyclopedia/soybean-cyst-nematode. Accessed 28 Apr. 2025.
4. Mueller, Kaitlyn. “PFP21: Soybean Cyst Nematode and HG Types—What Are They and How Can They Help You Manage SCN?” North Carolina Soybeans, North Carolina State Extension, 21 Apr. 2021, https://soybeans.ces.ncsu.edu/2021/04/pfp21-soybean-cyst-nematode-and-hg-types-what-are-they-and-how-can-they-help-you-manage-scn/. Accessed 28 Apr. 2025.
5. Heiniger, Rick, et al. Management of Soybean Cyst Nematode. University of Nebraska–Lincoln Extension, 2018, https://extensionpubs.unl.edu/publication/g1383/na/html/view. Accessed 28 Apr. 2025.
6. Byamukama, Emmanuel. “HG Type Testing: A Management Strategy for Soybean Cyst Nematode Control.” South Dakota State University Extension, 2022, https://extension.sdstate.edu/hg-type-testing-management-strategy-soybean-cyst-nematode-control. Accessed 28 Apr. 2025.
7. Tylka, Greg. “New Data-Based Calculator Estimates Economic Yield Loss to SCN in Individual Fields.” Integrated Crop Management, Iowa State University Extension and Outreach, 20 Nov. 2023, https://crops.extension.iastate.edu/cropnews/2023/11/new-data-based-calculator-estimates-economic-yield-loss-scn-individual-fields. Accessed 1 May 2025.
8. Dorrance, Anne, and Horacio Lopez-Nicora. “Verification of SCN Resistance in Soybean Varieties.” Ohio State University STEP UP Soybean, Ohio State University Extension, 2024, https://stepupsoy.osu.edu/soybean-production/variety-selection/verification-scn-resistance-soybean-varieties. Accessed 28 Apr. 2025.