Minnesota Faces First Soybean Disease Case

By Scout Nelson

A new soybean disease known as red crown rot has been confirmed for the first time in Minnesota, marking a significant development for the state’s soybean industry. The disease was detected and verified in a single field located in southwestern Minnesota.
Experts warn that the disease has the potential to cause major yield losses depending on its severity, timing, and environmental conditions.

Red crown rot is caused by a soilborne fungal pathogen called Calonectria ilicicola, which attacks the roots and lower stems of soybean plants. The infection leads to yellow and brown patches between leaf veins, which closely resemble symptoms of sudden death syndrome (SDS) and brown stem rot (BSR).

Additionally, infected roots and stems show red discoloration and reddish dots, with roots often appearing decayed. The disease in Minnesota was confirmed through observation of symptoms and DNA sequencing to identify the pathogen.

This marks the first detection of red crown rot in Minnesota, though it was previously reported in several other Midwest states. It was first identified in Illinois in 2018 and has since spread to Missouri, Indiana, Ohio, and Michigan.

The disease was confirmed in Rock County, Minnesota in August 2025, over 400 miles away from the nearest known infected area in Illinois. It has also recently been reported in south central Wisconsin, suggesting that the pathogen may be spreading more widely in the region.

The mode of spread of red crown rot in the Midwest remains unclear. It was once a problem in the southern United States, particularly in Louisiana and Mississippi during the 1990s, but later became less common there. Because red crown rot is difficult to diagnose, experts believe it might already exist undetected in other Minnesota fields.

Managing red crown rot poses challenges. Most soybean varieties grown in the Midwest are susceptible to disease. The fungus can survive in the soil for several years, limiting the effectiveness of crop rotation.

Some seed treatment fungicides have shown potential in reducing disease impact, but further research is needed to determine their effectiveness and understand the disease spread within Minnesota.

Red crown rot’s emergence highlights the need for ongoing surveillance, improved disease management practices, and greater awareness among Minnesota soybean producers to protect yields and crop health.

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