Snow Mold

Is lawn damage from snow mold something to worry about?

By: Sandy Feather 2009
Penn State Extension

Q. I was really shocked to see our lawn after the snow melted. Other lawns look patchy too, but our lawn seems to be the worst. Will I have to replace the entire lawn?

A. Large areas of bleached-out, dead-looking grass that are typical symptoms of snow mold damage. These fungal lawn diseases occur during the winter months and are most severe in areas where snow cover lasts much of the winter. The damage is usually worst where snow tends to accumulate from drifting or shoveling. Although it looks as though the lawn is badly damaged, the good news is it should be just fine once you rake out those matted areas and new growth begins.

Snow mold lawn damage
Snow mold damage on a lawn

Both gray and pink snow mold can occur in Western Pennsylvania. Gray snow mold is generally the less serious because it kills the blades of affected grasses, but it does not kill the crowns or roots, as pink snow mold can.


Spring Lawn Repairs

When the snow melts in spring, it reveals circular patches of bleached out-looking lawn that range in size from a few inches to several feet across. After long periods of snow cover, the entire lawn can be affected. The blades of grass in those areas are dead and matted together.

Long periods of snow cover can lead to this look in March
snow mold

Gray snow mold usually only occurs when we get snow cover before the ground has frozen. Gray snow mold can be distinguished from pink by the presence of fungal bodies called sclerotia. They appear as pinhead-sized light to dark brown hard structures embedded in leaves and crowns of infected turfgrass. Sclerotia are not present with pink snow mold. Simply rake out the affected areas thoroughly and your lawn should recover on its own. Fungicide applications are not effective in helping your lawn recover in the spring.

"Pink" snow mold earned its name due to its pinkish color

Pink snow mold

Cultural control methods are preferred over fungicide applications for controlling snow mold on home lawns. These include mowing your lawn well into fall, until it has stopped actively growing. Your last cut of the season should be slightly shorter than you would normally cut your lawn, say down to 11/2 to 2 inches. This keeps the grass from matting down on itself under snow cover, which creates a favorable environment for the development of snow mold. Rake and remove fallen leaves from the lawn before snowfall. Try to avoid piling snow on the lawn when shoveling sidewalks and driveways.

VIDEO: Snow Mold

Proper Fertilization Helps

Avoid fertilizer applications that contain excessive nitrogen in mid-fall, from late September through early November. Kentucky bluegrass and fine fescues tend to be more resistant to gray snow mold than perennial ryegrass or tall fescue. If fungicides are used, they should be applied around Thanksgiving to prevent gray snow mold from developing. Chloroneb, Bayleton (triadimefon) and thiram are labeled to control gray snow mold on residential lawns.

The variety of grass you plant, and when you apply fall fertilizer, can lead to stark differences like you see along this property line

Pink snow mold is slightly different and can cause more severe damage because it can infect crowns and roots as well as the blades.

Why is it called "Pink?"

The disease is named for the pink fungal spores that accumulate on the leaves of infected grass. Patches of turf appear bleached out and dead but with a pinkish cast. Sclerotia are not present. Pink snow mold develops only under snow cover. A related disease, caused by the same fungus, is called microdochium patch and can develop in cool, wet weather without snow cover.

Cultural Controls for Snow Mold

The same cultural controls that help prevent gray snow mold work to prevent pink. Kentucky bluegrass and fine fescues are more resistant to pink snow mold than perennial ryegrass. Fungicide applications may be recommended for newly seeded lawns. Mancozeb, Cleary's 3336.


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