Problem: Gray Snow Mold
A plant disease that primarily affects cool-season grasses, gray snow mold is caused by the fungus Typhula incarnata. Active only at cold temperatures (30° to 40°F) when moisture is abundant, gray snow mold is most likely to occur after snow has been in place for several months. Prolonged cold weather worsens symptoms; turf recovers quickly if warm weather follows the melting of snow.
Lightly infested turf usually recovers on its own. Rake dead patches thoroughly, then reseed them. Do not apply nitrogen-rich fertilizer in the fall. Since gray snow mold can form under fallen leaves, rake and remove leaves before snowfall. Tall grass is most susceptible to the disease, so mow lawn prior to snowfall. Reduce thatch buildup.