Soybean

Purple Seed Stain of Soybean

Cercospora kikuchii

Fungus

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In a Nutshell

  • Mottled purplish to brown discoloration of the upper leaves.
  • Red-brown spots may also appear on stems and pods.
  • Pink to purple discolorations varying in size (from spots to large patches) on the seeds.
  • Germination rates and seedling emergence may be affected.

Can also be found in

1 Crops
Soybean

Soybean

Symptoms

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.

Recommendations

Organic Control

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.

Chemical Control

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, for example mancozeb ( 2.5 g/l of water) during early pod stages to prevent leaf blight and pod infections.

What caused it?

Cercospora leaf spot is caused by Cercospora kukuchii. This fungus overwinters in plant debris in soils and on seeds. High relative humidity, 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 color.

Preventive Measures

  • Use certified pathogen-free seeds.
  • Tolerant varieties are available.
  • Rotate with non hosts to limit the incidence.
  • Tillage and exposure to solar radiation and wind reduce the survival of these fungi on plant residues.
  • Remove plant debris after harvest and destroy them.

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