Cause Fungi cause four different snow mold diseases including Typhula ishikariensis and T. incarnata, which cause speckled snow mold; Microdochium (Fusarium) nivale, which causes pink snow mold; Myriosclerotinia borealis, which causes Sclerotinia snow mold, also known as snow scald; and Globisporangium iwayami (syn. Pythium iwayami) and G. okanoganense (syn. P. okanoganense), which cause snow rot. These diseases have been found on winter wheat in the Pacific Northwest, and are important when snow cover on lightly frozen/unfrozen ground persists for approximately 100 days. However, pink snow mold is the most widespread and does not require snow cover but is promoted by cool, wet weather. Speckled snow mold is restricted to areas where snow persists. These diseases affect winter wheat, rye, and barley as well as numerous grasses. The pathogens can survive on many plant species and persist in soil or with host debris.
Symptoms A white, felty (or sometimes slimy) fungal mat on plants is evident as the snow disappears. Signs of the disease disappear as temperatures rise and sunlight increases. Damage is highly variable, ranging from a few dead leaves to the entire plant. If crowns are not damaged, plants may recover.
Cultural control
- Grow spring wheat.
- Rotating to legumes can reduce the incidence in a subsequent wheat crop.
- Early seeding (early to late August) enables the development of larger, more tolerant plants.
- Apply charcoal as coal dust to snow cover to speed snow melt.
- The variety Eltan, has some resistance. Sprague, Edwin, and Bruehl have very good snow mold resistance.
Reference Murray, T., Jones, S., and Adams, E. Snow Mold Diseases of Winter Wheat in Washington. 1999. Washington State University Coop. Ext. Bulletin 1880.