Does Snow Cover Cause Snow Mold in Lawns? Yes....and no...

Posted by Tony Koski, CSU Extension Turf Specialist

Gray snow mold can occur during very snowy winters or on shaded

areas of lawns - whenever snow cover persists for 60 days or longer

Our first long-lasting (for us in the lower elevations anyway ) snow of the year has people thinking of snow mold in their lawns.  When gray snow mold does occur in lawns, it is caused by the fungus Typhula incarnata. Fortunately, that “when” comes pretty infrequently for most Colorado lawns. Unless you live in the mountains or where snow cover persists for more than a couple of months, snow mold is not an important home lawn concern.  The fungus that causes snow mold requires 40-60 days of continuous snow cover before it begins infecting lawn grasses. Even when we do have those rare, extended periods of snow cover, the snow mold that results rarely kills home lawn turf. Kentucky bluegrass and fine fescues are more resistant to this disease, while perennial ryegrass and tall fescue are more susceptible.

The gray, fuzzy mold is easily seen as the snow melts

Prevent snow mold by mulching fallen tree leaves into the lawn with your  mower – or collecting them
if you have deep accumulations of leaves (because leaving a matted layer of tree leaves on the lawn over the winter can mimic snow cover… possibly resulting in snow mold under the leaves). And try to avoid shoveling or plowing snow from sidewalks and drives into long-lasting piles.

Snow mold damage on home lawns is almost always cosmetic,

with only the grass blades being affected.

When snow mold does occur in the home lawn, damage is usually cosmetic and will recover fairly quickly as warm weather occurs in the spring.  Recovery can be hastened by light raking with a leaf rake to lift up any matted grass.  In areas where snow was piled for 3-4 months, turf killed by snow mold can be aerated and overseeded in the spring.  

Raking affected areas with a leaf rake to "fluff up" the moldy,
matted grass will help speed up recovery.

Golf course superintendents apply fungicides to prevent gray snow mold (and another called “pink snow mold”), because both of these diseases can kill the closely mown turf of greens, tees and fairways. However, fungicide applications to prevent snow mold are not recommended for Colorado home lawns since damage to higher cut turf is almost always cosmetic, rarely fatal, and quick to recover in the spring.