As fall settles across Missouri, farmers are wrapping up harvest while school routines resume and the first hints of cooler weather appear. Amid the seasonal changes, soybean fields shift from vibrant green to tawny brown, signaling crop maturity. While the season brings excitement, it also unveils challenges, particularly late-season soybean diseases that can reduce yields and raise concern among growers. Among these, brown stem rot, sudden death syndrome, and red crown rot are the most common.
Red crown rot, caused by the soilborne fungus Calonectria ilicicola, has long been managed in southern states but is relatively new to the Midwest. First noted in Illinois during 2023 and 2024, the disease has become a frequent topic at Missouri field days in 2025. Confirmed cases now span eight counties: Lewis, Shelby, Audrain, Pike, Montgomery, Lincoln, Phelps, and Maries, according to the Crop Protection Network. Infection occurs during vegetative growth, but foliar symptoms such as interveinal chlorosis—yellowing between leaf veins followed by browning—appear later. Unlike sudden death syndrome, leaves typically remain attached after dying.
Red crown rot can be confused with brown stem rot or sudden death syndrome, but careful examination of stems and roots helps differentiate the diseases. Brown stem rot shows a brown pith, sudden death syndrome leaves a white pith with potential blue or gray fungal growth, while red crown rot is distinguished by red fruiting structures called perithecia near the roots. The pathogen thrives in warm, wet soil conditions, with Missouri’s spring planting season providing ideal temperatures and moisture for its spread.
Management options remain limited. Farmers are encouraged to slow the disease’s spread by cleaning equipment between fields, working infected fields last, rotating to non-host crops like corn, improving drainage, and selecting seed treatments that suppress infection.
Mandy Bish, a plant pathologist at the University of Missouri, is collaborating with the Missouri Soybean Merchandising Council to study red crown rot and identify long-term solutions. Bish explained, “The initial effort was to educate Missouri farmers and industry professionals to properly identify red crown rot. Through our partnership, we’ve obtained the fungus from Missouri fields and inoculated soybeans to intentionally study the disease. We plan to screen soybean breeding lines and varieties to identify sources of resistance, as no currently available commercial soybean lines are resistant.”
Missouri Soybeans urges growers to remain vigilant for symptoms and consult experts if red crown rot is suspected in their fields. With continued research and awareness, the state’s soybean industry aims to mitigate the impact of this emerging disease and protect yields in coming seasons.
