What’s that white stuff on my lawn?

The snow has finally melted in our area and my lawn has this whitish/grey stuff that looks like cotton

candy on it. What’s that?

Well, as you might have guessed, it is not cotton candy; it’s a a disease - mold that is growing in your lawn. It’s called snow mold and it’s very common in the northern tier of states and in Canada. Below is a little about it from Wikipedia –

Snow mold is a type of fungus and a turf disease that damages or kills grass after snow melts, typically in late winter.[1] Its damage is usually concentrated in circles three to twelve inches in diameter, although yards may have many of these circles, sometimes to the point at which it becomes hard to differentiate between different circles. Snow mold comes in two varieties: pink or gray.

Gray snow mold (Typhula spp. or Typhula blight) is the less damaging form of snow mold. While its damage may appear widespread, it typically does little damage to the grass itself, only to the blades.[1] Unlike most plant pathogens, it is able to survive throughout hot summer months as sclerotia under the ground or in plant debris.[3] Typhula blight is commonly found in United States in the Great Lakes region and anywhere with cold winter temperatures and persistent snow fall.[4][5]

References:

1.  "Snow Mold Fact Sheet". University of Rhode Island Landscape Horticulture Program. Retrieved 2012-10-07

2. "RPD No. 404 - Snow Molds of Turfgrasses". Univ. of Illinois Extension. July 1997. Retrieved November 11, 2011.

3. Ash, Cynthia (February 2000). "SNOW MOLDS in LAWNS". University of Minnesota. Retrieved 2012-10-07.

4. Kerns, J.P. (2011). "Turf diseases of the Great Lakes region". Univ. of Wisconsin Extension. Retrieved November 11, 2011.

5. Johnston, William H. (December 2003). "Snow Mold Control in the Intermountain Northwest". U.S. Golf Association. Retrieved November 10, 2011.

I live in Michigan and get grey snow mold in my yard every spring (the picture above was taken in my front yard). Apparently it isn’t really all that harmful to the grass, but perhaps I could do a better job of raking the lawn before the first big snowfall to get it ready for winter. The grey splotches in your lawn now will disappear as the weather warms and certainly be chopped away with the first mowing of the lawn. The mold doesn’t go away, it just goes dormant and remains underground until next winter’s snows.

If you would like to read about alternatives to control snow mold in your lawn, here is a link to an article from the University of Massachusetts that discusses several fungicides that you might use.  Apparently, since the banning of Mercury-based fungicides, there has not been a single fungicide that can effectively control all of the various strains of snow mold, especially the pink type.  

Snow mold is just one of the molds that can infest lawns and you are likely to see most of the other types over the course of a summer, either in your yard or as neighbor’s lawn. Some of the molds are not associated with the grass, but may be growing on the roots of trees, especially trees that were cut down but the roots left to rot. Guess what eats those roots? That’s right – molds.

 So, the bottom line is that you should not necessarily be overly alarmed by the snow mold; but, perhaps take some action this summer and fall to treat your lawn, so that it does not return next year. You won’t see it all summer, but it is still there, underground, just waiting for that first big snow to start growing again. You may still get “fairy rings” and mushroom s popping up from time to time in your lawn and those are forms of molds too, but that’s a different story and usually less harmful to the lawn.