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Gray Snow Mold

Typhula incarnata

Snow mold diseases occur during winter and/or late spring under snow cover. Several snow mold diseases affect turfgrasses in the northeastern United States. The two most common are gray snow mold and pink snow mold.

Symptoms and signs

Matted leaves of gray snow mold-affected turf

Matted leaves of gray snow mold-affected turf.            

This disease is usually noticed first as the snow melts in the spring. It is commonly found in those turf areas of greatest snow accumulation, such as along driveways or over the brink of a hill where snow drifts tend to accumulate. The most notable symptoms are white crusted areas of grass in which blades are dead, bleached, and matted together. These bleached areas range from several inches to several feet across. The chief diagnostic feature of gray snow mold is the presence of hard pinhead-sized fungal bodies called sclerotia. These light to dark brown sclerotia are embedded in the leaves and crowns of the infected grass plants.

Disease cycle

Sclerotia

Sclerotia of Typhula incarnata, cause of gray snow mold.    

Sclerotia oversummer in thatch, clippings, and the crown area of the grass plants. They germinate in fall and produce mycelial growth beneath the snow cover and infect plants. Gray snow mold seldom occurs except under snow cover when the soil is not frozen. In most instances, the fungus kills the blades of the plant, but does not kill the crown and roots.

Cultural control

Gray snow mold usually can be managed successfully in home lawns without the use of fungicides. Keep the turf mowed well into the fall to avoid leaving unclipped grass that tends to fall over and mat when snow falls. Try to avoid creating long-lasting snow banks when removing and piling snow from sidewalks and driveways. When symptoms appear at snow melt in the spring, rake the infected areas and break the crusted, matted leaves to encourage new growth. Kentucky bluegrass and the fine fescues tend to be more resistant to gray snow mold than creeping bentgrass, perennial ryegrass, and tall fescue.

Gray snow mold on home lawn

Gray snow mold on home lawn.

Chemical control

If gray snow mold tends to occur even though the cultural practices are correct, fungicides may be considered. Apply the fungicide prior to the first permanent snow cover in the fall. In many areas, this may be around Thanksgiving. A single application at this time usually will provide a satisfactory measure of control. Applying fungicides after the symptoms appear in the spring is of no value.