Randy Nelson, University of Minnesota Extension, Published April 25 2013
Snow molds may be present in your lawnMOORHEAD - As the snow continues to melt, some people are finding gray, pink or straw colored patches in their lawn. These patches may vary in size from a couple of inches to several feet in diameter.
Grass within these patches often have a matted appearance with mycelia - thread-like fungal structures - bordering or completely covering the area. These symptoms are caused by a group of fungi known as snow molds.
The two most common types of snow mold fungi are gray and pink. Gray snow mold is caused by Typhula spp. and produces white to gray colored mycelium. Pink snow mold is caused by Microdochium nivalis and produces off-white to pink colored mycelium. Both types of snow mold are active at temperatures around freezing and under wet environmental conditions.
Snow molds are most common when an early, deep snow cover prevents the ground from freezing.
Damage caused by snow molds is seldom serious. These areas generally take a little longer to green up in spring. Gently raking the affected areas of lawn using a leaf rake will promote drying and help to suppress further fungal growth. Remember that the grass is still wet so rake affected areas gently to avoid pulling out the grass by its roots.
To minimize the severity of snow molds next season, avoid excessive nitrogen fertilization after the middle of September, which can lead to succulent grass tissue that is conducive to snow mold growth. Continue mowing lawn until it is no longer actively growing. Tall grass is more likely to mat down and encourage the development of snow molds.
Raking leaves in the fall, spreading large snow drifts to encourage faster melting and selectively placing snow fence to minimize snow accumulation in problem spots will also help to minimize the severity of snow molds next season. Snow molds do not generally occur every year, therefore, a preventative fungicide application in the fall is generally not recommended.