Wedoany.com Report-Oct. 12, Red crown rot (RCR), a soilborne soybean disease that weakens plants and reduces yields, was identified in Minnesota for the first time in August. The infection was confirmed in a field in Rock County, according to Dean Malvick, a plant pathologist at the University of Minnesota.

Stem symptoms of red crown rot begin as a reddish discoloration. Tiny, red, ball-shaped perithecia can develop near the soil line but are not always present.

“This is the first known case of red crown rot in Minnesota, and the nearest known infection before this was more than 400 miles away in NW Illinois,” Malvick wrote in a University of Minnesota Extension bulletin. “It raises questions about how this pathogen is moving and whether it has gone undetected in other fields.”

The disease, caused by the fungus Calonectria ilicicola, was first detected in Midwest soybean fields in Illinois in 2018 and has since spread to Missouri, Indiana, Ohio, Michigan, and recently south-central Wisconsin. The pathways facilitating its spread across the region remain unclear, posing challenges for tracking and containment.

Managing red crown rot presents significant hurdles. Most soybean varieties tested in the Midwest are susceptible, and the fungus can persist in soil for years. “The red crown rot pathogen is thought to survive for multiple years in soil, thus minimizing the usefulness of crop rotation,” Malvick noted. While some seed treatment fungicides show promise, further research is needed to identify effective products and practices.

Stephanie Porter, an outreach agronomist with the Illinois Soybean Association, described the disease’s symptoms: “Foliar symptoms look similar to sudden death syndrome (SDS), stem canker, or brown stem rot, where foliar symptoms are caused by a toxin produced by the pathogen in the root that is then sent to the leaves following a midseason rain.” She added, “This disease is a lot like SDS. However, it has distinctive bright-red fruiting structures at the base of the stem called perithecia.”

Symptoms include reddish stems, root discoloration, and rot, often resembling other diseases like SDS or brown stem rot. Severely affected plants senesce early, with leaves remaining attached, unlike SDS where leaves typically drop. Accurate diagnosis is challenging, and Malvick cautioned that the disease may be present but undetected in other Minnesota fields.

Researchers are investigating the extent of red crown rot’s presence in Minnesota and exploring management strategies to reduce its impact. Farmers are encouraged to monitor fields closely for signs of the disease and adopt practices that could limit its spread, supporting the region’s soybean production.

This development highlights the need for ongoing research and vigilance to protect Midwest agriculture from emerging threats, ensuring sustainable yields for farmers.