Purple Seed Stain of Soybean
Visual symptoms appear during later growth stages, flowering and podding. The disease is characterized by a mottled purplish to brown discoloration of the upper leaves and their sunburned appearance. Red-brown spots may also appear on stems and pods. The infected seeds may look healthy or have pink to purple discolorations varying in size from spots to large patches on the seed coat.This may not have a negative impact on yields, but germination rates and seedling emergence may be affected.
Cercospora leaf spot is caused by Cercospora kukuchii. This fungus overwinters in plant debris in soils and on seeds. High relative humidities, warm temperatures (around 22 to 26°C), wind and splashes of rain favor the spreading of the fungus onto the leaves and the development of the disease. Initial infections are often latent and do not appear visible until flowering or pod formation stages. The fungus gradually enters the pod and grows on the seeds, giving them the characteristic mottled purplish or brown colour.
Sorry, we don't know of any alternative treatment against Cercospora kikuchii . Please get in touch with us in case you know of something that might help to fight this disease. Looking forward hearing from you.
Always consider an integrated approach with preventive measures together with biological treatment if available. On lots with a high percentage of discolored seeds treat the seeds with fungicides. This may provide some control on the spreading of the disease. Consider applying foliar fungicides during early pod stages to prevent leaf blight and pod infections.