Snow Mold
Snow mold, also referred to as snow rot, is a fungal lawn disease that is active underneath snow cover during the winter months. It typically appears as a matted area of grass with web-like fuzzy strings, or mycelia, in-between grass blades. These circles of matted grass and web-like fungus can be gray or pinkish in color and can appear as smaller patches throughout the lawn or as one large intertwined collection of patches.
There are two types of snow mold; gray snow mold (Typhula Blight) and pink snow mold (Microdochium Patch). While these two types of snow mold look similar, their effect on the grass is different. Gray snow mold typically only affects the grass blade and in most cases will recover fully as the grass grows through the spring. Think of this as being like a scratch in a finger nail. As the nail grows it pushes the affected area out and replaces it with healthy new growth. Pink snow mold, on the other hand, is more aggressive and kills the crowns and roots of the grass of the affected area.