Brent Jaenisch

Is PI88788 Working in Your Soybean Fields?

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Soybean Cyst Nematode (SCN) is the number one crop yield-reducing pest in soybean production. Potential crop yield loss to SCN is expected to rise as more and more populations of SCN overcome the PI88788 resistance source. The Peking resistance source is not as common as the PI88788, but it is becoming incorporated into more soybean varieties.

If you want to see how the SCN resistance source in your soybeans is holding up this growing season, you can do an early and late SCN soil test. If the egg count increases substantially between the early and late SCN sample, your SCN resistance source is likely failing.

Here are the 4 steps to this simple test.

Collect an early SCN sample (June)

  1. Choose a location in the soybean field to monitor, often near field entrance where SCN may have been first introduced to the field.
  2. Collect 8 to 10 soil cores (0-6 inch depth) within the soybean row at the location. You are trying to collect infected root tissue with SCN eggs.
  3. Mark the location with a large flag or GPS so you can come back to the same location later in the year.

Collect a late SCN sample (mid to late August)

4. Return to same location as the SCN sample from June. Repeat step #2.

Once you have conducted this simple test, you will get an idea of whether or not the SCN resistance source in your soybean varieties is controlling SCN populations, or if it is time to change resistance source in soybean varieties next year. If the SCN egg count increases during the year, that SCN resistance source is not adequately controlling SCN in your field.

AGVISE Laboratories has completed a number of SCN demonstration projects since 2019, using the early vs. late SCN sampling procedure. The projects have shown that the PI88788 resistance source is not adequately controlling SCN populations at some field sites in west-central Minnesota. More information can be found in our agronomy blog for the 2020 and 2021 projects.

Data from the AGVISE SCN field project, 2019-2020.

A silver bullet for managing SCN does not exist and will likely never exist. Do your due diligence and figure out if your SCN resistance source is working in your own fields.

Each year, AGVISE summarizes the SCN egg count that are submitted to our laboratories. The SCN summaries each year continue to demonstrate that the problem is not going away. A consistent SCN soil sampling program remains the best tool to monitor SCN populations. This is how we learn if current SCN management strategies like crop rotation and SCN-resistant varieties are working, or if you need to reevaluate your soybean management plan.

Additional Resources
The SCN Coalition Website
Iowa State University SCN Resource Compendium
SCN in Iowa: A Serious Problem that Warrants Renewed Attention (ISU Extension, June 2021)

AGVISE offers quick and reliable SCN egg count analysis. If you need to order SCN submission forms or supplies, you can order supplies from our online store.