Red crown rot, a soilborne fungal disease, has emerged as a significant concern for soybean farmers in Missouri. Confirmed for the first time in Marion County and Audrain County in the summer of 2024, the disease can cause yield losses of up to 80% in severe cases.
There is currently no cure for red crown rot. Seed treatments may reduce symptoms and infection but cannot eliminate the fungus, which can persist in the soil for extended periods.
Key Characteristics and Lookalikes
Red crown rot often resembles sudden death syndrome (SDS) due to similar leaf symptoms, including yellow spots that progress to larger yellow and brown areas between veins. However, distinguishing signs of red crown rot include:
- Reddish discoloration at the stem base and root near the soil line.
- White fungal growth (mycelia) on roots, followed by the appearance of red perithecia (small round fruiting bodies).
Another fungus, Clonostachys, produces pink to orange perithecia and may also be mistaken for red crown rot.
Spread and Survival
First identified in southern U.S. peanut crops in the 1960s and soybeans in the 1970s, red crown rot has since spread to 11 soybean-producing states. Its spread may be hastened by the movement of contaminated soil via used farm equipment. The fungus thrives in wet conditions and survives through winter in plant residue, though cold temperatures may reduce inoculum levels.
Management Strategies
While there are no resistant soybean varieties, farmers can adopt best management practices to contain the disease:
- Thoroughly clean equipment when moving between fields to prevent soil contamination.
- Rotate crops to non-host plants like corn for at least two years.
- Improve field drainage to limit favorable wet conditions.
- Time planting to avoid soil temperatures between 77-86°F, which favor the pathogen.
Early identification is critical. Farmers should scout fields, inspect roots and stems for characteristic symptoms, and distinguish red crown rot from similar diseases like SDS and brown stem rot.
As red crown rot continues to spread, containment and proactive field management remain the most effective tools to mitigate its impact on soybean yields.
