SCN Coalition helps farmers fight relentless pest

AMES — The microscopic, soil-borne soybean cyst nematode is considered the most serious biological threat to the U.S. soybean industry. In North America, it causes yield losses worth more than $1 billion annually.

The SCN Coalition helps farmers combat this relentless pathogen in a variety of ways. Established by Professor Greg Tylka, director of the Iowa Soybean Research Center, with several colleagues at other universities, the coalition was launched in 2018 and now includes university scientists from 28 states and Ontario, Canada, grower checkoff organizations and corporate partners.

Each year, Tylka and his team develop an updated list of commercially available SCN-resistant varieties for Iowa that the Coalition helps promote. ISU Extension and Outreach publishes the list in the fall.

Growing resistant varieties is the best management tactic for SCN when growing soybeans, according to Tylka. Even so, the nematodes become “resistant to resistance,” he said.

“So in soybean years, we encourage farmers to alternate growing soybeans that have the two different genetic types of SCN resistance in order to slow the loss of effectiveness of resistance. We also recommend growing non-host crops such as corn in alternating years to disrupt the pest’s life cycle, and there are several nematode-protectant seed treatments that farmers should evaluate when growing soybeans in SCN-infested fields.”

“This pest is not going away,” said Ed Anderson, executive director of the North Central Soybean Research Program, who has long been involved in the SCN Coalition and its outreach efforts. “We have to stay ahead of it if we’re going to be able to grow soybeans profitably into the future.”

The SCN Coalition rolled out its popular ProfitChecker calculator in 2023. The tool, powered by data from over 35,000 research plots studied by Tylka and his team over 20 years, is available online for U.S. farmers and crop advisers. It has been used nearly 90,000 times since it first became available.

The coalition’s tagline, “What’s Your Number? Take the Test. Beat the Pest,” encourages farmers to use the SCN Profit Checker to see an estimate of SCN’s economic toll on their fields. With that information, they can select the best resistant soybean varieties for their location and also consider using other management practices.

The SCN Coalition regularly shares ever-changing information about SCN population levels, the availability of resistant soybean varieties and yield results for SCN-resistant varieties with different genetics.

The coalition also engages farmers with innovative outreach campaigns that have included an annual national nematode day and sweepstakes, and a quiz “Are You Smarter Than a Nematode?” Such initiatives have been recognized for creativity and effectiveness, earning the coalition top awards from groups including the National Agri-Marketing Association and the Public Relations Society of America.

The foundation of ProfitChecker and other SCN educational efforts is the Iowa State SCN-resistant Soybean Variety Trial Program. This program compiles yield and SCN control data collected annually by Tylka and his team from hundreds of SCN-resistant soybean varieties. The varieties are grown in replicated experiments conducted in fields rented from farmers in Iowa's nine crop-reporting districts.

“Fields don’t always look infested — even the reduction in yield isn’t always obvious,” Tylka said. “That’s why it’s so important to test.”

Results from random surveys of fields across the state show that the frequency of SCN infestation has remained relatively stable in Iowa over the 30 years, at around 75% of fields found to be infested, according to Tylka.

The widespread research efforts have revealed some surprising things, Tylka said. “For example, soil was collected from atop snow drifts in late winter to determine if wind-blown soil can spread SCN. The answer was a resounding yes. Results like this amaze me that the SCN is not in more fields."

Anderson said efforts of the SCN Coalition have been very effective at raising awareness and developing solutions through its three-pronged approach

1. Helping farmers make the best decisions for short-term management based on extensive field trials and effective communication and outreach on currently available solutions and recommendations.

2. Working with soybean breeders to develop more diverse genetics to fight SCN and encouraging companies to license the genes and breeding materials, and put them into commercial use.

3. Looking to the horizon for new solutions through promoting basic and applied research to combat SCN and other nematode pests.

Much of the funding for the SCN Coalition and related research has come from checkoff funds from the North Central Soybean Research Program, the United Soybean Board, the Iowa Soybean Association and other soybean commodity groups. Other support has included a USDA NIFA Crop Protection and Pest Management grant (Award 2024-70006-03448) and USDA Hatch funding through the College of Agriculture and Life Sciences at Iowa State (IOW0#3901).