Red crown rot confirmed in Ohio soybeans for the first time

COLUMBUS, Ohio — A new soybean disease that can cut yields by more than half has been detected in Ohio for the first time, raising urgent concerns for the state’s top crop.

Red crown rot, caused by the soilborne fungus Calonectria ilicicola, which has devastated crop fields in neighboring states, was recently identified in Delaware County by The Ohio State University Soybean Pathology and Nematology Laboratory.

“This confirmation is a critical first detection,” said Horacio Lopez-Nicora, assistant professor of soybean pathology and nematology with Ohio State’s College of Food, Agricultural, and Environmental Sciences (CFAES). “Once established, this pathogen is nearly impossible to eradicate, so integrated management is the only sustainable path forward to reduce its impact on our soybean crop.”

The issue is significant, considering that soybeans are Ohio’s top crop by acreage and value.

In states where red crown rot is established, yield losses can reach as high as 80% in severely affected fields, Lopez-Nicora said. Even under moderate disease pressure, farmers often see losses between 15% and 70%.

“For Ohio, if the disease spreads unchecked, growers could face persistent yield reduction and higher production costs year after year, threatening the profitability of the state’s most widely planted crop,” said Lopez-Nicora, who also serves as an Ohio State University Extension state specialist. OSU Extension is CFAES’ outreach arm.

Looks like sudden death syndrome — but isn’t

Red crown rot can be mistaken for sudden death syndrome or other common soybean diseases because all cause yellowing and browning between the veins of leaves during pod fill. But the two can be distinguished by careful inspection.

“With red crown rot, we see red to orange discoloration at the crown of the stem and the presence of perithecia — small, red fungal fruiting bodies — on the lower stem or crown,” Lopez-Nicora said. “Plants often die quickly, and dead plants usually retain their leaves attached to stems.”

Accurate diagnosis is critical, he said. Farmers are urged to dig up plants, not pull them, and submit samples for confirmation to the CFAES Soybean Pathology and Nematology Laboratory.

A high-priority emerging threat

Red crown rot has been in the United States since the 1960s, first affecting peanuts. The exact path red crown rot took into the north-central United States remains unclear. However, the exchange of used equipment is thought to play a major role, as soil clinging to machinery from infected fields can easily introduce the fungus to clean fields.

From an epidemiological perspective, red crown rot’s emergence highlights the challenges affecting Ohio agriculture, said Pierce Paul, professor and chair of the CFAES Department of Plant Pathology. Paul is also an epidemiologist and an OSU Extension state specialist.

“Its soilborne nature, long-term persistence and ability to mimic other soybean diseases make it difficult to detect and manage,” Paul said. “The emergence and spread of a new disease like red crown rot are the result of three major factors: weather conditions favorable for its development, the presence of the pathogen in our fields and our cultivars being susceptible or only partially resistant.”

Paul said understanding and quantifying the damage caused by red crown rot is essential to predicting how epidemics might spread and to modeling the long-term impact on yield.

“This is why continued investment in CFAES is essential,” he said. “Scientific leadership enables early detection, robust diagnostics, systemwide response, and the research needed to forecast and mitigate future outbreaks — ultimately protecting the resilience and profitability of Ohio’s soybean industry.”

What farmers should do now

Lopez-Nicora urged farmers and consultants to take immediate action to limit spread:

• Scout systematically: Check low-lying or compacted areas where symptoms often appear first.
• Dig up whole plants: Look for red to orange crown discoloration and red fungal fruiting bodies.
• Sanitize equipment: Prevent soil movement from infested to clean fields; harvest suspect fields last.
• Submit samples: Collect whole plants with roots and send them to the CFAES Soybean Pathology and Nematology Laboratory, Attn: Horacio Lopez-Nicora, 110 Kottman Hall, 2021 Coffey Rd., Columbus, Ohio 43210. Instructions for submitting a sample are available in the C.O.R.N. Newsletter. The C.O.R.N. Newsletter, produced weekly by the OSU Extension Agronomy Team, provides timely crop observations, research-based recommendations and management updates for Ohio producers and ag industry professionals.

Looking ahead, integrated management will be critical, Lopez-Nicora said.

Practices such as crop rotation with nonhost crops, improving drainage, using seed-applied fungicides and managing soybean cyst nematode populations — which can intensify red crown rot severity — will be important to protect yields in affected areas.

“This first case of red crown rot in Ohio highlights the importance of CFAES diagnostic capacity, research and outreach,” Lopez-Nicora said. “Through our strong partnerships with OSU Extension educators, private consultants and industry agronomists, we can confirm diseases quickly and provide rapid, research-based recommendations to help farmers respond.”

Farmers and producers can learn more about red crown rot and other key issues affecting Ohio agriculture from OSU Extension professionals at the 2025 Farm Science Review, Sept. 16-18 at the Molly Caren Agricultural Center near London, Ohio.

Advance tickets are $10 online and at participating OSU Extension offices and agribusinesses, or $15 at the gate. Children 5 and under are admitted free. Show hours are 8 a.m. to 5 p.m. Sept. 16-17 and 8 a.m. to 4 p.m. Sept. 18.

For details and tickets, visit fsr.osu.edu.