Snow mold. What, me worry?

>> Saturday, March 8, 2008

Most of the snow has finally receded, except for the north side of the house. What it left behind is a little distressing. After searching the internet for possible explanations I learned that it could be snow mold. Looks pretty nasty doesn't it?

I grew up in Indiana, where we have snow for much longer than they do here in Utah, but I don’t remember ever seeing this kind of stuff.

What I learned from Snow Molds in Lawns by Cynthia Ash is:

“Snow mold is a fungal disease that appears in early spring as the snow melts. There are two types of snow molds, gray and pink, that become active under the snow cover. Gray snow mold (also called Typhula blight) is caused by Typhula spp., while pink snow mold (also called Fusarium patch) is caused by Microdochium nivalis.”

“Gray snow mold survives hot summer temperatures in the soil or in infected plant debris as sclerotia, resistant fungal structures, while pink snow mold survives as mycelium or spores in infected plant debris. Fungal growth begins in the winter, beneath a cover of snow on unfrozen ground. Growth can take place at temperatures slightly below freezing and may continue after snow melt, as long as the grass remains cool and wet. Gray snow mold activity stops when the temperature exceeds 45° F or the surface dries. Pink snow mold activity may continue during wet weather in the fall and spring, as long as the temperature is between 32° F and 60° F.”

She goes on to explain that the symptoms first appear as circular, straw colored patches when the snow melts in the spring. I didn’t see any circular patches. It was more or less free-form in that it was spread over this section of lawn, about ten foot by twelve foot without actually being circular.

I took photos on March 1 and over the course of the next few days the patch does not appear to be spreading, which is how snow mold behaves.

Maybe the grass is just naturally brown from lack of sunlight. Since the lawn is in its normal dormant state this time of year I should expect to see brown, but this is the first year I have seen a difference in the shade of brown.

Another contributing factor to snow mold is excessive applications of nitrogen fertilizer in the fall. I did fertilize the lawn but I don’t consider it excessive.

To add to the mystery, snow mold does not appear every year.

So far, nothing has convinced me one way or the other that this is or is not snow mold. Should I worry anyway? Probably not.

One good thing, the damage caused by snow mold is seldom serious. Besides there is nothing that can be done for it now. I just have to wait for the sun to warm up the soil, which I am sure will be any day now.

To prevent snow mold in the future, or at least minimize its damage:

# Avoid excessive applications of nitrogen fertilizer in the fall.

# Continue to mow the lawn at the recommended height until it is no longer actively growing. The taller the grass, the more likely it will mat down and encourage snow mold development.

# Rake up leaves in the fall.

# Manage the thatch layer to avoid accumulations of more than ½ inch.

# Spread out large snow piles to encourage rapid melting. Use snow fencing to minimize snow accumulation in problem spots.

Throughout the year I mow my lawn to about 4” tall to prevent the summer heat from drying out the soil and during the cooler months I gradually lower the blade to about 2”, so I don’t think the grass is tall enough to cause concern.

I always rake up the leaves, you just gotta love that free compost material.

Thatch should not be a problem because the lawn is aerated every year. Maybe I should do it more often? I don’t know.

The final caution to prevent snow mold is spreading out large snow piles to encourage rapid melting! I don’t think so. Sorry, but I’m not that dedicated to my lawn.

The bottom line is that if it is snow mold it will soon disappear and will not cause any significant damage.

Besides, I have bigger things to worry about, like when am I going to be able to plant my garden!

Cynthia Ash co-authored a pamphlet put out by North Dakota State University covering lawn disesases.


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