Red crown rot: A new threat to soybean production

Marty Chilvers<chilvers@msu.edu>, Austin McCoy<mccoyaus@msu.edu> and Sunao Ochi, Michigan State University Department of Plant, Soil and Microbial Sciences -

Red crown rot can be spread through contaminated soil, providing yet another reason to not move soil and to clean equipment when possible.

Red fruiting bodies on a soybean stem.
Photo 1. Red crown rot signs of red perithecial fruiting bodies on the outside of a soybean stem. Photo by Sunao Ochi.

Red crown rot is caused by the fungal pathogen Calonectria ilicicola, which was first identified in the United States on peanuts in 1965 and is now a prominent pathogen throughout the peanut growing region of the United States. In 1972, C. ilicicola was identified causing red crown rot of soybean for the first time in the United States. Alarmingly, red crown rot appears to be moving into more northern climates with reports of soybean fields with severe disease occurrence and significant yield losses in Indiana, Illinois, Kentucky and Missouri.

Foliar symptoms of red crown rot are like that of sudden death syndrome or brown stem rot, typically presenting during late reproductive growth stages. Small chlorotic (yellow) blotches on leaf tissue will begin to form that will eventually expand into interveinal chlorosis and necrosis (Photo 2). In severe cases wilting, loss of leaves and premature senescence can occur. While not always present, dark red structures (perithecia) and a maroon coloration of the soybean stem at the soil line are indicative of red crown rot (Photo 1).

A diseased soybean field and a closeup of a diseased soybean plant.
Photo 2. Red crown rot symptomatic soybean plants that appear similar to sudden death syndrome in Pike County, Illinois, in 2023. Photo by Sunao Ochi.

To date, little is known about why this disease is moving northward and why it is now impacting soybean in these regions. If you suspect red crown rot, be sure to submit a sample to the Michigan State University Plant and Pest Diagnostic Services or contact the Chilvers Lab directly at chilvers@msu.edu to help us keep ahead of this disease in Michigan.

Thank you to the Michigan Soybean Committee for supporting these efforts.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).

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