Integrated Management of Potato Blemish Diseases:
Silver Scurf Pathogen: Fungus Helminthosporium solani
Black Dot Pathogen: Fungus Colletotrichum coccodes
By Amanda J. Gevens, Associate Professor & Extension Plant Pathologist, UW-Madison & Julie Crane, Former Research Associate, UW-Madison
Silver scurf and black dot are potato blemish diseases that are growing in prevalence and economic importance. Both diseases cause tuber discoloration that makes infected tubers unmarketable. Distinguishing between the two diseases can be challenging, but is possible with laboratory procedures.
Unfortunately, there are gaps in our understanding of both diseases and how to manage them best, although research on these diseases has been intensifying in recent years.
Silver scurf and black dot are caused by separate fungal pathogens that have distinct life cycles. Management strategies mostly consist of cultural and chemical controls, and are hindered by the lack of commercially available resistant cultivars.
Challenging to control, these diseases require an integrated effort to reduce their impact on potato production.
SYMPTOMS:
Silver scurf and black dot symptoms appear as silver, shiny lesions on the tuber skin. Silver scurf lesions begin as circles with well-defined borders, and are often initially at the stolon-end. Over time, they coalesce to cover much of the tuber surface.
