Suspect red crown rot in soybeans? These tips will help manage threat 

By Darcy Telenko, Purdue Crop Pathologist 

Red crown rot of soybean, caused by Calonectria Ilicicola, continues to be a concern in Indiana. Purdue University researchers identified the first symptoms in 2026 in a field that has had a previous history with soybeans at beginning pod (R3) growth stage. 

There weren’t any foliar symptoms, but when the canopy was pulled back, the red discoloration at the crown or soil line could be seen. (Figure 1 B) 

Figure 2 shows the map of Indiana counties where red crown rot has been confirmed in previous years. As the rest of the growing season moves ahead, Purdue researchers are actively surveying fields to better understand the distribution and prevalence of red crown rot across Indiana. 

Grower participation is critical to this effort, and any farmer who suspects red crown rot is encouraged to report affected fields and submit samples to help document its occurrence. 

What to look for 

Red crown rot often occurs in patches within a field and can resemble other soilborne diseases such as sudden death syndrome (SDS) and brown stem rot. Early foliar symptoms include interveinal chlorosis (yellowing) and necrosis (browning) of leaf tissue, making diagnosis based on foliage alone difficult. (Figure 1A) 

If these symptoms are observed, collect several affected plants and examine the lower stem and roots. Plants affected by red crown rot typically exhibit a reddish discoloration at the stem base near the soil line, often accompanied by small, red, spherical perithecia on the stem surface. (Figures 1 and 2) 

When stems are split open, the pith may appear gray to dark gray, roots are often rotted, and plants can be pulled easily from the soil due to root deterioration. 

Purdue is working with colleagues across the Midwest to track this disease. Samples of soybeans infected with red crown rot will greatly assist researchers in determining the distribution of red crown rot and guide future research. 

Purdue appreciates the samples that have been received previously, and farmers are urged to get out and look at these suspect areas in their fields. 

Any farmer who suspects damage from red crown rot should collect several plants showing the symptoms and send them to the Purdue Plant Pest Diagnostic Laboratory (PPDL). Please ship early in the week. Anyone sending samples from multiple locations should label the samples and provide the date collected, variety, field zip code or county and previous crop. 

The cost for that sample is covered by the Indiana Soybean Alliance (ISA). Information on how to submit a sample can be found at indianafieldcroppathology.com. Mail the samples to: 

Plant and Pest Diagnostic Laboratory 
LSPS-Room 116, Purdue University 
915 W. State Street 
West Lafayette, IN 47907-2054 

Checkoff funding from the United Soybean Board and Indiana Soybean Alliance (ISA) are supporting this initiative and sample processing, therefore there will be no charge for soybean samples submitted to the clinic.