By Rose Malisani, MSU Cascade County Agricultural Agent

Montana’s winter has brought a blanket of snow across the Treasure State this season. Snow has
many horticulturalists weary of a fungal disease called snow mold.

Snow mold becomes active once snow covers turf in late fall or early winter but is seen when
snow melts away in early spring. Open winters will not have a large occurrence of snow mold as
the fungus thrives under snow cover. Snow mold is seldom serious but turf affected by snow
mold may take longer to recover than areas not affected by snow mold. The two types of snow
mold are gray and pink and have different characteristics.

Gray snow mold appears when the temperature is 45°F to below freezing and the ground is cool
and wet. Gray snow mold thrives in an environment with snow cover on unfrozen ground. The
fungus is white or gray with webby patches across turf. Gray snow mold will survive summer in
soil and can continuously affect turf if not treated.

Pink snow mold appears with snow cover on unfrozen ground and when temperatures are 32°F
to 60°F. A defining characteristic is the pink or white patches that grow on grass leaf blades in
circular shapes. Both rain and mowing can spread pink snow mold. The fungus does not need
snow to infect turf, just a wet and cool environment. Like gray snow mold, pink snow mold can
continuedly affect turf if not treated.

Fungicides are not recommended to control snow mold, however, fall fungicide applications may
be necessary for sever cases. Fall control methods can be to rake and remove debris from turf,
mow grass to recommended heights until the growing season has subsided, and avoid excessive
nitrogen applications. Snow mold can also be controlled in the spring by raking the patches to
increase aeration and temperature. Other control methods may be to manage thatch layer and
utilize snow fences or shelterbelts to prevent large snowdrifts.

MSU County Extension agents and the Schutter Diagnostic Laboratory can assist in diagnosing
snow mold along with other plant diseases. Visit www.msuextension.org to find your local
Extension office or visit www.diagnostics.montana.edu for the Schutter Diagnostic Laboratory.

Author: Staff

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