By Dean Malvick
Red crown rot of soybean has been found for the first time in Minnesota. It was detected and confirmed in one field in southwestern Minnesota. This disease can cause significant yield loss in soybean depending on severity, weather, and timing of disease development.
Red crown rot is caused by a soilborne fungal pathogen (Calonectria ilicicola) that infects the roots and lower parts of stems of soybean plants. Symptoms on leaves include yellow and brown patches between veins that are like symptoms of sudden death syndrome (SDS) and brown stem rot (BSR). Red coloration (similar to Rhizoctonia stem rot) and reddish dots develop on roots and lower stems, and roots are often rotted. The disease in Minnesota was confirmed to be red crown rot based on signs and symptoms of the disease as well as by isolation and identification of the pathogen via DNA sequencing.
Red crown rot was first found in Midwestern soybean fields in Illinois in 2018 and had spread to multiple fields in Illinois as well as fields in Missouri, Indiana, Ohio, and Michigan prior to its detection in Minnesota. When the disease was found in Minnesota (Rock County) in August 2025, the nearest known location with red crown rot was over 400 miles away in NW Illinois. Red crown rot has also recently been confirmed in south central Wisconsin.
The modes by which red crown rot is spreading in the Midwest are unknown. In the 1990s, red crown rot of soybean was a problem in the southern U.S. in Louisiana and Mississippi, but it appears to have since become uncommon in those areas. Although red crown rot is known to occur in only one field in Minnesota, it can be difficult to diagnose and could have escaped detection in other fields.
Source : umn.edu