Winter Damage, Part I (Snow Mold)

There is danger out there lurking under the snow in your yard.  Its called gray snow mold.  If you have never heard of it, get familiar with it, because you will probably see it soon.  If you have dealt with it before, set your rake in a handy spot - you will need it soon.

Gray snow mold (Typhula blight) affects all cool season turf grass species where there is an extended period of snow cover.  We have experienced probably the longest period of snow cover here in the past ten years, so conditions are perfect for its appearance.

Gray snow mold grows by expansion of mycelium (the white fibers of fungus) under the snow.  It can't develop if there is not a period of snow cover on your turfgrass.  The longer your grass is in the fall, or the more leaf litter around your lawn, the more gray snow mold you can expect to find in the spring.

Gray snow mold in a lawn

The picture here shows some grey snow mold on a lawn as the snow melts.  And below is a close up in an area where the grass wasn't trimmed in the fall…looks like you have mold on your lawn.

Gray snow mold on longer grass

Control of gray snow mold involves three things:

1.  Mow your grass one last time late in the season fairly short (I usually do mine about the week of Thanksgiving).

2.  Clean up leaf litter and debris in the fall.

(Both these items make it harder for the gray snow mold to develop and flourish.  But in March, you've already missed both of those ideas…)

3.  As you see patches of gray snow mold as the snow melts, rake the patches with a leaf rake.  It breaks up the mold patches and increases air circulation and drying.  And that will usually kill the gray snow mold.  The patches should normally fill in as spring proceeds, if not you can overseed in the area of the damage.

Fungicides are rarely used on home lawns for gray snow mold.  Some extension sites recommend avoiding late fall fertilizing, as the additional nitrogen may encourage the growth of gray snow mold.

We're not done yet.  There is a second type, called pink snow mold.  It at least has some color to it…

Pink snow mold in lawn

Wouldn't you like that in your lawn for a bit of spring color?  Pink snow mold, Microdochium patch, is very similar to gray snow mold, but develops without snow cover.  Again, by keeping your lawn cut relatively short and cleaning up leaf litter and debris in the fall, you should be able to avoid meeting this guy in your lawn (the next time we have a winter without snow on the ground for an extended period!).