Purple seed stain of soybean
Purple seed stain is caused by the fungus Cercospora kikuchii. Seeds infected with this pathogen can be symptomless or have pink to purple spots extending from the hilum. Discoloration can cover the entire seed or appear as small spots.
Crop value may be lowered by dockage or seed certification denial, but yield is not reduced.
Purple seed stain incidence can be increased by warm, wet weather during and after flowering.
Although caused by the same organism, there is no consistent relationship between occurrence of Cercospora leaf blight and purple seed stain. Purple seed stain symptoms on soybean seed. Image: T. Mueller
Purple seed stain symptoms on soybean seeds. Image: A. Sisson
For more information see the Soybean Seed Quality Considerations feature article.