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Nematodes stealing bushels, revenue and deserve attention, experts advise

Article cover photo
Ron Heck, a Perry area farmer, told farmers at Commodity Classic in Orlando, Florida they need to scout their fields and take action against soybean cyst nematodes. (Photo: Joseph L. Murphy/Iowa Soybean Association)

By Aaron Putze, APR, ISA communications director


With soybean prices under continued pressure and farm inputs remaining stubbornly high, farmers are looking for every opportunity to boost yields and income this growing season.

One opportunity may be difficult to see but is right under their noses, stealing productivity and sales.

“Nematodes are eating your profits,” says farmer Ron Heck of Perry. “If they eat five bushels per acre a year, that means they’re consuming an entire crop every ten years.”

The scourge of soybean cyst nematodes (SCN) has been well documented. But the pest’s negative impact to the bottom line is increasingly ignored and underestimated, argue those in the know. 

“A dirty little secret is that there was a time in the 1990s when managing the nematode in the short-term was easy,” said Iowa State University (ISU) professor and nematologist Greg Tylka. “Well, that was yesterday.”

Counts on the rise

Fast-forward 30 years and nematode reproduction and populations are on the rise.

“There are two types of farmers in the Midwest,” Tylka said. “Those who are worried about SCN and those who should be.”

Heck and Tylka offered their warnings and call-to-action during a panel discussion focused on the income-robbing pest held earlier this month at Commodity Classic in Orlando, Florida.

Joining them in the conversation were Auburn University plant pathologist Kathy Lawrence, Albert Tenuta, plant pathologist for the Ontario (Canada) Ministry of Agriculture and farmers Kip Roberson and Pat Duncanson of North Carolina and Minnesota, respectively.

Rising populations and resistance spells trouble for farmers and the soybean industry, panelists said.

“The nematode is adapting to and overcoming resistance while soybean yields of SCN-resistant varieties are trending lower,” said Tylka, who also serves as director of the Iowa Soybean Research Center at ISU. “Added together, the impact could be a loss of 10-15 bushels per acre. That’s profound when considering this situation is quite likely typical for farmers throughout the Midwest.”

Panelists agreed that admitting and identifying the presence of SCN is what makes it so difficult to manage.

A farmer growing 60-bushel soybeans, for example, may be pleased with the output. Therefore, they’re not as inclined to ask what went wrong despite the potential to harvest 70-bushel soybeans per acre if nematode populations were suppressed.

“Some growers are aware they have an issue,” said Lawrence. “But it usually takes a yield loss – and a rather severe one – for them to start looking to find out why.”

Start sampling

Lawrence and other panelists urged farmers to start sampling nematode populations this spring as soon as field conditions allow. And farmers who have been sampling should do so more often – at least every two years.

“Act now,” urged Tylka. “It’s easier to keep low numbers low than drive high numbers down.”

In addition to taking the test, farmers can also beat the pest by:

  • Rotating crops whenever possible (including a cover crop). Doing so stunts the buildup of SCN populations.
  • Scouting fields and sampling frequently throughout the fields. “Just because you have a test and don’t see it doesn’t mean they aren’t somewhere else,” Heck said.
  • Rotating SCN-resistant soybean varieties by substituting Peking varieties for PI88788 soybeans.
  • Never assuming. Farmers often admit that they noticed “something was going on” in field locations where there were unaccounted yield losses, says Tenuta. “When you see stunted plants that have the visual symptoms, you’re already observing a 20-25 percent yield loss.” Added Heck, “It’s not iron chlorosis. It’s not sour dirt. Take the test and stop blaming other things.”
  • Using seed treatments to help reduce soybean stress. “Don’t let your soybeans get the flu,” said Heck, who first discovered SCN in the early 1990s and measured counts as high as 30,000. “Make your soybeans happy and they’ll perform better.” Ducanson agreed. “As seed treatments have become available, we’ve been aggressively using them,” he said. “Every soybean we planted in 2018 had a seed treatment and helped us manage SCN populations more successfully.”
  • Do something more than you have been doing. “We’re also using cover crops,” Ducanson said. “We still have some things to learn. Our goal is to get something to grow in March and April to get more residue and stubble and biomass when our soils are very susceptible to heavy rains. We’re hopeful there will be a positive impact on SCN, too.”

Roberson, the North Carolina farmer, said he’s living proof that issues with SCN can be mitigated if you pay attention and work at it.

“We saw real problems on acres we began farming that had been planted continually to soybeans. In some parts of the field, we had bare ground with just a stalk,” he said. “We knew we had to make a change, so we began rotating crops and planting cover crops.

“We had nematode populations decrease dramatically and now have good soybean stands in places where we didn’t have soybeans,” he said. “We’re proof that you can manage the pest.”

Despite the availability of several management options and some on-farm successes in battling the pest, Tylka said more work is needed.

He urged farmers to call on seed companies to breed additional soybean varieties resistant to SCN.

“Through your (soybean) checkoff investments, there are breakthroughs. But a critical gap remains between the university scientists and seed companies,” Tylka said. “Industry needs to hear directly from farmers to truly understand the value in investing in these new technologies to better manage SCN.”


Contact Aaaron Putze at

For media inquiries, please contact Katie Johnson, ISA Public Relations Manager at or Aaron Putze, ISA Communications Director at

For permission to republish articles or to request high-res photos contact Aaron Putze at Iowa Soybean Association | 1255 SW Prairie Trail Pkwy | Ankeny | IA | 50023 | US

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