By Blake Jackson
As autumn settles in, Missouri welcomes cooler days, football under the lights, and harvest season. Soybean fields shift from green to golden brown, signalling the season’s change.
While this time of year is filled with school routines and Mizzou pride, many farmers are also beginning to notice signs of late-season soybean diseases that threaten yields and cause concern. Among the most common are brown stem rot, sudden death syndrome, and the increasingly discussed red crown rot.
Although red crown rot is not new to the U.S., having been first identified in North Carolina in the 1970s, it has only recently gained attention in the Midwest. The disease appeared in Illinois in 2023 and 2024 and became a major discussion point at Missouri field days in 2025.
According to the Crop Protection Network, cases have now been confirmed in eight Missouri counties Lewis, Shelby, Audrain, Pike, Montgomery, Lincoln, Phelps, and Maries.
The disease is caused by the soilborne fungus Calonectria ilicicola. While plants are infected early in their growth, foliar symptoms such as interveinal chlorosis, where yellowing occurs between the leaf veins before turning brown appear later. Unlike sudden death syndrome, where leaves fall off after necrosis, red crown rot causes leaves to stay attached even after the plant dies.
To correctly diagnose red crown rot, farmers can inspect stems and roots. Brown stem rot creates brown piths inside stems, while sudden death syndrome leaves a white pith with blue or gray fungal growth. Red crown rot, however, produces distinctive red fruiting bodies, called perithecia, at the stem base near the roots.
Thriving in warm, wet conditions with soil temperatures between 77°F and 82°F, the disease found ideal conditions during Missouri’s 2025 spring planting season.
Management options remain limited. Farmers are encouraged to clean equipment between fields, rotate crops, improve drainage, and use seed treatments to slow its spread.
University of Missouri plant pathologist Mandy Bish is leading research alongside the Missouri Soybean Merchandising Council. “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.”
Photo Credit: istock-sandramatic
Categories: Missouri, Crops, Soybeans