Red crown rot (RCR), caused by the soilborne fungus Calonectria ilicicola, has recently emerged as a significant threat to soybean crops in the Midwest. Initially identified in southern soybean fields in 1972, RCR has gradually made its way into Illinois and, more recently, Kentucky. The disease mimics the symptoms of other common soybean diseases, making it difficult to identify without close examination.
Distribution and Symptoms:
RCR has been confirmed in several Illinois counties, including Bureau, Christian, Effingham, Fayette, Ford, Kankakee, Livingston, Madison, Marion, Pike, Tazewell, Sangamon, St. Clair, and Woodford. In Kentucky, the disease was also detected in soybeans. While there have been scouting efforts in Iowa, Indiana, and Wisconsin, RCR has not been confirmed in those states thus far.
The visual symptoms of RCR typically appear between the R3 and R7 growth stages of soybeans, exhibiting interveinal chlorosis and necrosis, which resemble sudden death syndrome (SDS). One distinctive characteristic of RCR is the presence of small, red fruiting structures called perithecia at the base of the plant stem, just above and below the soil line.
Impact and Management:
RCR can cause significant yield losses, with double-digit reductions observed in Illinois soybean fields and up to 25% losses in southern regions. Unfortunately, there are no effective fungicide treatments for RCR once the infection has established in a field. To manage the disease, farmers must rely on proactive management and cultural practices.
Delaying soybean planting may be beneficial as RCR thrives in wet and cool conditions, although it can negatively impact early planting strategies. Improving soil drainage in areas prone to pooling, avoiding excessive organic matter, managing pathogenic nematodes and root-feeding insects, and implementing crop rotation out of soybeans for at least two years can help reduce RCR-related issues.
Red crown rot presents a growing concern for soybean farmers in the Midwest, particularly in Illinois and Kentucky. Recognizing the distinct symptoms and implementing effective management practices are crucial to mitigate the impact of this destructive disease. Continued research and collaboration among experts and farmers are essential to developing long-term strategies for sustainable soybean production in the face of red crown rot.
Photo Credit: istock-sandramatic
Categories: Illinois, Crops, Soybeans