Missouri Soybean Growers Warned About Red Crown Rot

By Blake Jackson

Missouri soybean growers should remain vigilant for red crown rot (RCR) in 2026, according to Mandy Bish, University of Missouri Extension state plant pathologist.

The soilborne fungus, Calonectria ilicicola, was confirmed in nine Missouri counties during the 2025 growing season, following its first detection in Marion County in 2024.

RCR can lead to significant yield losses. In 2024, some fields in Missouri experienced reductions of 50%-55%. First identified on soybeans in North Carolina in 1972, the pathogen has spread throughout the southeastern U.S. and into the Midwest.

“The identification of red crown rot across nine Missouri counties in 2025 raises important questions,” Bish said.

“We still have work to do to understand the extent to which the pathogen is actively spreading to new areas versus the extent to which increased awareness is allowing us to detect longer-standing infestations. Detections in areas with limited soybean acreage, such as Maries and Phelps counties, underscore the need to learn more.”

The fungus survives in plant residue over winter and thrives in warm, wet soils between 77°F and 86°F. Symptoms typically appear after the R3 (beginning pod) growth stage, starting as yellow spots on leaves that expand between the veins, similar to sudden death syndrome (SDS).

Unlike SDS, leaves often remain attached after dying. Scouting should include digging up plants to inspect roots and stem bases for reddish discoloration or red perithecia, especially during late reproductive stages. Splitting stems can also help differentiate RCR from brown stem rot.

“There is no silver bullet solution for RCR,” Bish said. She recommends rotating to non-host crops like corn for two years, using fungicide-treated seed labeled for RCR, selecting tolerant varieties when available, cleaning equipment between fields, and working infected fields last.

MU Extension researchers continue to study management strategies and collaborate with other land-grant universities. Growers can contact the MU Plant Diagnostic Clinic for diagnosis and track disease spread through the Crop Protection Network.

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