Fall has arrived, bringing cooler weather, Friday night lights, harvest season and the annual shift from green soybean fields to tawny brown as crops mature. The kids are trading lemonades for hot chocolate and returning to school routines. For our land grant university, the Mizzou Tigers are border war champions once again and research on campus is proving to be just as successful.
However, for many farmers, this season also reveals late-season disease symptoms that can cut into yields and cause concern. The most common late-season soybean diseases are brown stem rot, sudden death syndrome and red crown rot.
Red crown rot is not new to the United States. First discovered on soybeans in North Carolina in the 1970s, the disease has long been managed in southern states. However, it is relatively new to the Midwest, gaining attention in 2023 and 2024 when confirmed in Illinois. In 2025, the disease became a frequent discussion topic at field days across Missouri. As of September, cases have been confirmed in eight counties: Lewis, Shelby, Audrain, Pike, Montgomery, Lincoln, Phelps and Maries, according to the Crop Protection Network. 
The disease is caused by the soilborne fungus Calonectria ilicicola. While infection occurs during vegetative growth stages, foliar symptoms — such as interveinal chlorosis, where leaves yellow between veins before turning necrotic and brown —appear later. Leaves typically remain attached to the plant even after death, distinguishing red crown rot from sudden death syndrome, in which leaves fall once necrosis sets in.
Other symptoms can be confused with sudden death syndrome or brown stem rot, but diagnosis can be confirmed by examining stems and roots. Brown stem rot causes a brown pith inside stems, while sudden death syndrome leaves a white pith and often blue or gray fungal growth at the stem base. Red crown rot, by contrast, produces red fruiting structures called perithecia at the base of stems near the roots.
The disease thrives in soil temperatures between 77 and 82 degrees and favors warm, wet conditions. Missouri’s spring planting season, marked by high soil temperatures and frequent rainfall, created favorable conditions for the pathogen to spread.
Management options are limited. Farmers are advised to slow the spread by cleaning equipment between fields, saving infected fields for last when scheduling field work, rotating to non-host crops such as corn, improving drainage and selecting seed treatments that suppress infection.
Mandy Bish, University of Missouri plant pathologist, is working with the Missouri Soybean Merchandising Council to study samples and identify long-term solutions.
“The initial effort was to educate Missouri farmers and industry professionals to properly identify red crown rot,” Bish said.“Through the partnership and collaborations with MSMC, we’ve been able to obtain the red crown rot fungus from Missouri fields and inoculate soybeans to make them intentionally sick. We plan to use these methods to screen soybean breeding lines and varieties to work on identifying sources of resistance as no currently available commercial soybean lines are resistant.”
Missouri Soybeans encourages farmers to stay alert for symptoms and to consult experts if they suspect red crown rot in their fields.
If you think you have Red Crown Rot in your soybean field, samples can be sent to:
University of Missouri Plant Diagnostic Clinic
Attn: Peng Tian
1100 University Ave.
28 Mumford Hall
Columbia, Missouri 65211
