Soybean cyst nematode can quietly build up in a field, reducing soybean yield potential before above-ground symptoms appear. Encourage your growers to plan ahead using post-harvest soil testing to help avoid mid-season soybean cyst nematode problems.
Post-harvest is one of the best windows for SCN soil testing because fields are accessible, soil conditions are often suitable for sampling and growers still have time to use the results before making seed and rotation decisions. By confirming whether SCN is present, measuring population levels and evaluating how well resistant varieties are performing, you can help growers build a stronger integrated management plan.
Why post-harvest soil testing for SCN matters
The results of post-harvest SCN soil testing can help you give growers a clearer starting point for management decisions for their next soybean crop. By collecting samples after harvest, growers can confirm whether SCN is present, estimate population levels and establish baseline egg counts before selecting seed or finalizing crop rotations.
The fall is when egg counts for SCN are at their highest, giving growers the best assessment of SCN numbers in their soil. This can help you evaluate whether current resistant varieties are holding up or you need to recommend a different resistance source, a non-host crop rotation or additional management tools before a grower plants soybeans again.¹
How to guide growers through soybean cyst nematode testing
You can make SCN testing easier by walking growers through a consistent sampling process. In suspected fields, growers should collect soil cores randomly across the area using a zigzag pattern. For a 20-acre field, recommend collecting 10 to 20 cores from the top 6 to 8 inches of soil, then mixing them together in a clean bucket to create a single sample.²
Once the soil is thoroughly mixed, growers need only about 2 cups (1 pint) of soil for the final sample. Remind growers to place the soil in a labeled sample bag with the field location and date, then send it to a soil testing lab for analysis. Fields with different cropping histories, soil types or previous SCN concerns should be sampled separately so you can help growers make more accurate field-by-field decisions.³
Turning egg counts into management decisions
SCN egg counts can help turn a soil test result into a management conversation. Most laboratories report SCN as eggs per 100 cc, but make sure results are being compared on the same basis.
Egg counts can help confirm whether a field is infested, estimate the level of pressure and determine how aggressive the management plan should be. Higher egg counts may indicate a greater need to rotate to a non-host crop, select a soybean variety with a different source of SCN resistance or consider additional tools to protect yield potential.⁴
Help growers understand that SCN egg counts are estimates, not exact measurements of SCN abundance. SCN numbers are often unevenly distributed across a field, but tracking the population over time can help growers understand whether their management decisions are working.
When counts remain elevated after repeated use of the same resistance source, you can use that information to discuss alternative resistance sources, crop rotation and other integrated management strategies before the next soybean crop is planted.
Use the SCN Profit Checker to make the risk visible
Direct growers to the SCN Profit Checker to help connect SCN soil test results to potential yield and profit impacts. The SCN Coalition’s calculator allows growers to enter field information and soil test results to estimate the economic return of resistance management, crop rotation and other practices.
That information can make SCN risk easier to discuss before spring decisions are made. You can help growers interpret their SCN levels and have stronger conversations around resistant soybean varieties, seed treatments, crop rotations and long-term SCN management.
Experts are available to help you make your SCN management decisions. 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
- Webster, Wade, and Guiping Yan. “How to Sample for Soybean Cyst Nematode (SCN).” NDSU Agriculture, North Dakota State University, Apr. 2025,https://www.ndsu.edu/agriculture/ag-hub/ag-topics/crop-production/diseases-insects-and-weeds/crop-diseases/how-sample-soybean-cyst.
- Faghihi, Jamal, and Virginia R. Ferris. “Soybean Cyst Nematode.” Purdue Extension Entomology, Purdue University, June 2018,https://extension.entm.purdue.edu/publications/E-210/E-210.html.
- Webster and Yan. “How to Sample for Soybean Cyst Nematode (SCN).”
- Tylka, Gregory L., and Paula Flynn. “Interpreting SCN Soil Sample Results.” Iowa State University Extension, July 1999,https://scn.plantpath.iastate.edu/files/inline-files/SCN_IPM61.pdf.
