Purple Seed Stain and Cercospora Leaf Blight
Symptoms:
- Purple seed stain reduces seed quality and is recognized as purple to pink areas on seeds ranging in size from small spots to large patches.
- Infected leaves appear `sunburned".
- Symptoms on leaves primarily occur in southern areas of the Midwest and begin after flowering.
- Infected seeds do not always express symptoms.
- Red-brown spots may develop on leaves, stems, and pods, and these spots may merge to form large lesions.
Pathogen Involved:
- Cercospora kikuchii (a fungus).
- Survives from year to year on infested debris or seed.
- This fungus overwinters in soybean tissue and in infected seeds.
- The same pathogen also causes Cercospora blight and leaf spot, which can reduce yields.
Time of Occurrence:
- Flowering to maturity.
Conditions Favoring Disease:
- High humidity and warm temperatures.
Disease Management:
- Use pathogen-free seed.
- Some varieties are less susceptible than others.
- Rotation out of soybeans may be helpful.
- Foliar and seed treatment fungicides may provide some control.