Production Blog

Are you letting nematodes have their day in your soybean fields?

Soybean cyst nematode (SCN) is the No. 1 threat to soybean yield across North America. To spread awareness about the pest, Oct. 6, 2025, has been declared National Nematode Day by The SCN Coalition.

Quizzes asking "Are You Smarter Than a Nematode" have been testing farmers during the past few weeks. This informative series sponsored by BASF, Indigo and Syngenta challenges participants to test their nematode knowledge.

There's no such thing as being late to class for this quiz. Here are the questions and answers being used to help educate about plant-parasitic nematodes and their significance to soybean production.

Question 1: How often should soybean farmers test fields for SCN?

A: Every three years.

Testing is the cornerstone of every successful SCN management plan, said Dylan Mangel, plant pathologist at the University of Nebraska-Lincoln.

"We encourage farmers to get fields tested every three to five years, or after every second or third soybean crop -- especially right after harvest when SCN numbers tend to peak," Mangel said. "Regular testing not only lets you check if your current SCN management strategies are doing the job, but it also helps you spot when it's time to shake things up with new tactics like trying nematode-protectant seed treatments. Plus, don't miss out -- many state checkoff organizations offer free soil testing, making it even easier to stay ahead of this yield-robbing pest."

Question 2: Is SCN 100% resistant to PI 88788 soybean varieties?

A: It's complicated.

"PI 88788 was a victim of its own success," said Carl Bradley, plant pathologist at the University of Kentucky. "Most soybean varieties on the market rely on PI 88788 for its genetic resistance to SCN. But as this strategy became the norm, SCN began adapting, slowly building up resistance and making PI 88788 less effective over time."

Bradley indicated that the good news is soybean farmers have tools in their arsenal. "By rotating to other SCN-resistant varieties like those that use Peking as a source of resistance and rotating to a non-host crop, they can turn the tables on SCN and keep this yield-stealing pest in check," he added.

Question 3: Which root-knot nematode species is the most damaging and widespread?

A: Southern root-knot nematode.

The SCN Coalition has expanded its education and awareness efforts to include other nematodes that have an impact on soybean production because southern root-knot nematode is the No. 2 threat to the soybean crop in the southern U.S.

"Several root-knot nematode species can infest soybean fields, but the southern root-knot nematode is the most damaging and widespread," said Horacio Lopez-Nicora, soybean pathologist and nematologist at Ohio State University. "While it's impossible to eliminate its presence, proper active management can significantly help you reduce its impact."

TAKE THE TEST

When farmers and agronomists understand the widespread parasitic nematode issues, they are more inclined to test fields. SCN soil test results can be entered into a calculator called the SCN Profit Checker (https://www.thescncoalition.com/…), which estimates the economic influence of SCN on each field. Realizing the dollars being lost helps spur motivation for management.

For the most recent DTN article about how dry weather encourages SCN go to: https://www.dtnpf.com/….

Find a library of resources from The SCN Coalition here: www.TheSCNCoalition.com. The SCN Coalition is a public/checkoff/private partnership formed to increase the number of farmers who are actively managing SCN. 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, Indigo, Nufarm, Pioneer (Corteva), Syngenta, Trace Genomics, UPL Ltd., Valent and Winfield United.

Pamela Smith can be reached at pamela.smith@dtn.com

Follow her on social platform X @PamSmithDTN

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