By Andi Anderson
Ohio soybean growers are being encouraged to closely monitor their fields for signs of red crown rot, an emerging soybean disease that was first confirmed in the state in 2025. Researchers at The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) are working to determine how widely the disease has spread and are asking farmers for assistance.
Red crown rot is caused by the soilborne fungus Calonectria ilicicola. The disease can survive in soil for many years, making early detection and accurate identification important for long-term crop management. The fungus thrives in warm and wet soil conditions, making recent periods of heavy rainfall a concern for soybean production.
Horacio Lopez-Nicora, Associate Professor of Soybean Pathology and Nematology and a Provost’s Early Career Scholar at CFAES, emphasized the importance of field scouting during late summer.
“This is an important time to scout because red crown rot symptoms become most visible during the reproductive stages of soybean, particularly during pod fill,” said Horacio Lopez-Nicora. “August and September are an excellent window for growers to walk fields and look for patches of plants showing premature yellowing, interveinal chlorosis and necrosis, wilting, or plant death.”
Researchers are particularly interested in understanding the disease’s distribution across Ohio. “That is one of the major questions we are trying to answer,” Lopez-Nicora said. “Growers, crop consultants, and Ohio State University Extension educators can play an important role by scouting fields and submitting suspicious plants for diagnosis.”
“The more samples we receive from across Ohio, the better we can begin to understand where this disease is occurring."
The disease poses a serious risk to soybean yields. According to researchers, severe infestations may cause yield losses of up to 80%, while moderate disease pressure can reduce yields by 15% to 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,” he said.
One challenge is that red crown rot closely resembles sudden death syndrome (SDS). Both diseases can cause yellowing and browning between leaf veins while the veins remain green.
“That is why growers should not diagnose red crown rot or sudden death syndrome based on foliar symptoms alone,” Lopez-Nicora said.
Researchers recommend digging up entire plants, including roots, and examining crowns and lower stems for reddish discoloration or red fungal structures.
Ohio State’s Soybean Pathology and Nematology program is offering free diagnostic testing for suspected red crown rot and SDS samples. Encouraging growers to take action, Lopez-Nicora said, “If you see suspicious symptoms, scout, dig and submit. Do not rely on the leaf symptoms alone. Dig up the entire plant, including the roots, and send it to us for diagnosis.”
FAQ 1: How can I tell if my soybeans have red crown rot?
Answer: Look for patches of plants with premature yellowing, browning between leaf veins, wilting, or plant death. To confirm, dig up the entire plant and check for reddish discoloration near the soil line and small red fungal structures on roots and crowns.
FAQ 2: Why is red crown rot a major concern for soybean growers?
Answer: Red crown rot can survive in soil for years and cause severe yield losses. In heavily affected fields, losses can reach up to 80%, making early detection critical for protecting profitability.
FAQ 3: What should growers do if they suspect red crown rot?
Answer: Don't rely on leaf symptoms alone. Collect whole plants, including roots, and submit them for free diagnostic testing through Ohio State University's Soybean Pathology and Nematology program to get an accurate diagnosis.
Photo Credit: gettyimages-zoran-zeremski
Categories: Ohio, Crops, Soybeans