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The SCN Coalition: The sequel

Article cover photo
Greg Tylka, Iowa State Univeristy nematologist, co-leads the revival of the Soybean Cyst Nematode Coalition. The group is spearheading an effort to get farmers to actively manage SCN again. (Photo: Joseph Murphy/Iowa Soybean Association)

By Matthew Wilde, ISA senior writer


A wildly successful education and awareness campaign is back after a 20-plus-year hiatus to help soybean farmers fight a familiar, yield-robbing foe.

The Soybean Cyst Nematode (SCN) Coalition re-launched late last month at Commodity Classic in Anaheim, California. The goal, members say, is more soybeans in bins and money in pockets.

SCN, a small parasitic roundworm, attacks the roots of soybeans and robs nutrients from plants.

A 25-year Iowa State University (ISU) study shows SCN has gradually adapted to resistant seed varieties, reducing soybean yields by an average of 14 bushels per acre compared to when the pathogen was well controlled. SCN costs farmers more than $1 billion annually, experts say.

But the scary thing, according to coalition members, is many farmers don’t even realize it as they’ve watched yields escalate.

“It’s the reason we’re back,” said Greg Tylka, Ph.D., coalition co-leader and ISU nematologist. “SCN-resistant varieties are quietly losing effectiveness, so a new awareness campaign is needed.”

Researchers and farmers held a press conference at Classic announcing the SCN Coalition’s return and a panel discussion about the most damaging pathogen to North American soybean production.

The past holds the key to future success, officials said. In the late 1980s, SCN decimated fields across the Midwest to the point farmers thought it would threaten the viability of the soybean industry.

Ron Heck, coalition member and Perry farmer, recalled finding areas of stunted growth in soybean fields. Losses were finally documented with the advent of the yield monitor and yield mapping technology.

“I barely knew what SCN was in 1994,” said Heck, a former Iowa Soybean Association and
American Soybean Association president. “It was out there and no one knew it.”

Soybean checkoff-funded efforts changed that.

The North Central Soybean Research Program (NCSRP) formed the first SCN Coalition in 1997 after a survey showed 65 percent of farmers never tested fields for the No. 1 yield robber. The coalition’s iconic campaign, “Take the Test. Beat the Pest,” pushed awareness and soil testing for SCN.

Checkoff investments contributed to the development of SCN-resistant soybean varieties. Yield losses attributed to the parasite were greatly reduced.

“Eventually, we become a victim of our own success,” Tylka said.

Ron Heck, center, Perry farmer and SCN Coalition member, encourages farmers to soil test for soybean cyst nematode. The pest is the No. 1 yield robber in soybeans. (photo: Joseph Murphy/Iowa Soybean Association)

SCN testing and vigilance waned the past two decades as soybean yields increased. Market research shows 94 percent of farmers know little or nothing about SCN scouting, 59 percent grow SCN-resistant varieties but of that number, 68 percent didn’t know the source of resistance.

Continuous use of the same resistant breeding line — namely PI 88788, which out-yielded others — in commercial varieties contributed to the buildup of nematode resistance.

Research shows SCN reproduction has skyrocketed in fields using PI 88788-resistant varieties. Effective control is 10 percent reproduction or less. In Iowa, it’s about 60 percent. In Illinois, it’s 88 percent.

“Farmers are now clearly losing yield even growing the best varieties with SCN resistance available,” Tylka said.

To slow the troubling trend, Tylka said the coalition was revived to convince farmers to actively manage SCN again.

“The goal is to help farmers grow more soybeans profitably,” Tylka said. “I still meet farmers today who remember, ‘Take the Test, Beat the Pest.’ We want to build off that equity.”

This time around, industry and academic stakeholders are all in. Eight corporate sponsors and 12 university partners joined checkoff-funded associations — NCSRP, United Soybean Board and several states — to help farmers better manage the microscopic worms that are a giant problem.

The message hasn’t changed much: Losses can be mitigated with proper management. Recommendations include:

  • Test field to know SCN numbers.
  • Rotate resistant varieties to slow the buildup of SCN populations. SCN populations can adapt to individual resistant varieties as well as to sources of resistance such as PI 88788 and Peking.
  • Rotate to non-host crops.
  • Consider using a seed treatment nematicide.

After 20-plus years of using mostly the same source of resistance, natural selection spurred SCN reproduction — a trend that can’t be reversed, according to coalition literature. Tylka, one of the nation’s leading experts on the subject, contends the SCN battle isn’t lost.

“It’s just that farmers now have to use an integrated approach,” he said. “The traditional way of management is no longer working.”

That means testing and scouting fields even if they appear normal.

If a field with SCN averaged 65 bushels per acre last year, it could have done about 80, research shows.

“Even if you think you’re getting great yields, you could be doing better,” Tylka added. “Farmers shouldn’t wait until they have sick-looking beans. By that time, the proverbial horse is out of the barn.”

Max Wenk, a Wisconsin farmer and coalition member, said apathy is the greatest challenge for the group.

Appealing to a farmer’s pocketbook may be the best way to get them to believe SCN is a serious threat again and take action, he said.

“To improve margins in the new normal of the ag economy, this is the best place to look,” Wenk continued.

For more information check out the coalition’s website,

Matthew Wilde can be contacted at

For media inquiries, permission to republish articles or to request high-res photos, please contact Katie James, ISA Public Relations Manager at © 2020 Iowa Soybean Association. All rights reserved.

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