Purple seed stain (Cercospora kikuchii)
Symptoms of purple stain are most evident on the seeds, but the fungus also attacks leaves, stems and pods. On the seeds, discolouration varies from pink or light purple to dark purple and ranges from a small spot to the entire seed coat. Cracks often occur on the discoloured areas giving the seed coat a rough, dull appearance. When infected seeds are planted, the fungus grows from the seed coats into the cotyledons (seedling leaves) and into the hypocotyls (seedling stem). The fungus produces spores abundantly on infected seedlings and these spores serve as source of infection to leaves, stems and pods. The spores are spread by wind and rain splash.
- Use certified disease-free seeds.
- Plant resistant varieties, if available.
- Avoid overhead irrigation.