The SCN Coaltion is a resource for soybean growers fighting a yield-stealing nematode.
Soybean cyst nematode (SCN) is a microscopic parasite that attacks soybean roots, siphoning off nutrients and stunting plant growth. Though small, SCN’s impact is massive, causing approximately $1.5 billion in crop losses each year in the United States alone. This nematode not only reduces yields but also predisposes plants to other diseases, making it a multifaceted threat to soybean production.
SCN has become particularly challenging due to its ability to adapt and overcome traditional management practices. Many growers rely on SCN-resistant soybean varieties as their primary defense. However, SCN is constantly evolving, and some populations can now bypass these genetic defenses, rendering previously resistant varieties vulnerable once again. This adaptive capacity of SCN is why organizations like the SCN Coalition are so vital — they serve as a continuous force in the fight to stay ahead of the nematode’s evolving threat.
Enter the SCN Coalition, led by Horacio Lopez-Nicora, Ohio State University nematology professor. The coalition’s primary mission is to educate growers about SCN and sustainable measure of control. They advocate for routine soil testing, research and innovation that focuses on equipping farmers with the tools and knowledge they need to effectively combat SCN. Lopez-Nicora shares his insights into SCN’s biology, its impact on soybean crops and the Coalition’s proactive strategies for keeping this formidable pest in check.
Understanding the Costly Impact of SCN
SCN has consistently ranked as the most damaging pathogen to soybean crops in the United States. Responsible for an estimated $1.5 billion in annual losses, this tiny nematode is a stealthy adversary, often causing significant yield reductions without showing any visible symptoms.
“No matter where you go and look for that in the literature, you will see that soybean cyst nematode consistently ranked the number one,” Lopez-Nicora says. “It’s robbing yield potential from the crop, quietly taking away as much as 30% of yield potential, even when the crop looks perfectly healthy.”
The SCN lifecycle is particularly problematic for farmers. The nematode can persist in the soil for years, producing eggs that lie dormant until the right host is present.
“Once you have it in your field, it is highly unlikely that you will get rid of it, you will have to manage it, and it can persist in the field for many years,” Lopez-Nicora explains. “Even if you rotate your crops and plant corn for several years, SCN will still be there, waiting,” he emphasized, highlighting the pest’s resilience. “It’s like an unwelcome houseguest that never leaves.”
Lopez-Nicora explains how SCN’s biological mechanisms allow it to thrive within the soybean plant’s roots.
“This animal is penetrating the root system, modifying cells that are not supposed to be modified in a way that now the plant believes that the whole project is down there in the root system,” he says. “The nematode essentially hijacks the plant’s root system, reprogramming the cells to feed itself.”
Once it penetrates the root, Lopez-Nicora says SCN “uses a specialized stylet to inject effectors into the plant cells, manipulating them in ways that suppress the plant’s immune response and redirect nutrients to the nematode.”
The SCN Profit Checker
The SCN Coalition developed a suite of tools designed to help farmers better understand the SCN threat. Their SCN Profit Checker provides an estimate of potential yield losses based on SCN population levels and soil composition, such as sand percent and potential of hydrogen (pH).
The tool works by calculating economic losses associated with SCN, providing farmers with insights into the financial stakes.
“You may have a nematode robbing your yield, and in a way, that is not visible,” he said. “The Profit Checker is really about giving farmers a clearer picture of how SCN is affecting their bottom line and helping them make more informed management decisions.”
Lopez-Nicora emphasizes that SCN often goes undetected in fields that appear healthy, which can lead to substantial financial losses.
“A farmer might not see the impact, but that doesn’t mean it’s not there,” he said. “SCN could be robbing them of yield year after year. With tools like the profit checker, we’re helping to bring that hidden cost to light.”
Managing the SCN Threat with Integrated Approaches
The SCN Coalition advocates for an integrated pest management strategy, which includes rotating crops, soybean varieties and sources of genetic resistance to limit SCN’s ability to adapt.
“The SCN Coalition recommends a very proactive way of starting with rotating crops and varieties. Rotate, rotate, rotate!” he explained. “Using the same resistant variety year after year is like issuing a selection pressure on SCN to evolve and overcome that resistance.”
One of the major challenges in SCN management is the nematode’s growing ability to overcome the commonly used PI 88788 source of resistance. Lopez-Nicora pointed out that over 90% of resistant soybean varieties rely on PI 88788, which has been widely used for decades.
“Unfortunately, SCN has caught up,” he says. “We’re now seeing SCN populations that can reproduce on PI 88788, which is a huge concern because it leaves farmers with fewer effective options.”
The coalition is urging soybean growers to consider rotating different sources of resistance, including varieties with resistance from Peking, which remains effective against many SCN populations. However, Lopez-Nicora acknowledged that varieties with alternative resistance sources are not always easy to find.
“More than 90% of the commercially available resistant varieties have that PI 88788 as a source of resistance,” he notes. “We need more diversity in our soybean genetics. That’s a big part of what the Coalition is advocating for — a broader toolbox for farmers to draw from.”
Understanding SCN Virulence Profiles
Lopez-Nicora also highlights the importance of understanding virulence profiles — a term that describes SCN’s ability to infect different resistant varieties.
“Not all SCN populations are the same, unfortunately,” he says. “Some SCN types have adapted to specific resistance genes, so it’s crucial for farmers to know which SCN types are present in their fields.”
The coalition encourages growers to test their fields to determine the virulence profile of their SCN populations, which can help guide decisions on soybean variety selection and management practices.
“If you know your virulence profile, you can choose the right variety for your field,” Lopez-Nicora says. “It’s about knowing your enemy. The more you know about the SCN in your field, the better equipped you are to manage it.”
Adding Seed Treatments and Cover Crops to the Mix
Beyond crop rotation and genetic resistance, the SCN Coalition advocates for the use of seed treatments and cover crops as part of a comprehensive SCN management plan.
“Seed treatments offer an additional layer of protection,” Lopez-Nicora says. “They can enhance soybean root health and help protect young soybean plants against several soilborne pathogens as they establish themselves.”
He added that seed treatments are especially valuable when combined with resistant varieties, providing a one-two punch against SCN.
Cover crops, which are grown during the off-season, can also play a significant role in managing SCN populations.
“Cover crops improve soil health, which indirectly benefits soybean plants by creating a more robust environment that’s less hospitable to SCN,” he says.
Some cover crops, like cereal rye, act as non-hosts, reducing SCN populations by depriving the nematodes of a food source.
“Cover crops are a great way to support soil health and help keep SCN in check,” Lopez-Nicora says. “It’s about using every tool in the toolbox to fight this pest.”
A Continuing Battle Against a Relentless Pest
Despite these advances, Lopez-Nicora acknowledged that managing SCN remains an uphill battle. He likened the fight against SCN to the Red Queen’s race in Through the Looking-Glass, where characters must run as fast as they can just to stay in place.
“We’re running as fast as we can just to keep up with SCN,” he says. “It’s a constant arms race, and we can’t afford to let our guard down.”
He encourages soybean growers to stay proactive and vigilant.
“SCN isn’t going away, but with the right strategies, we can minimize its impact,” he says. “Know your numbers, understand your SCN type, and be strategic about your management choices. That’s the only way we’re going to stay ahead of this pest.”
The SCN Coalition’s work shows the power of collaboration, innovation and resilience in agriculture. “We’re fighting not just for today’s crops but for the future of sustainable soybean farming,” he adds.
