The Snow Molds

With temperatures beginning to rise, the snow that has been on the ground for most of December is beginning to melt.  Although in the  snow belt region of Northeast Ohio the likelihood of snow disappearing is remote.  Given the weather snow mold severity is a concern on creeping bentgrass and Poa annua turf. The various snow molds are:

Typhula blight (Typhula incarnata) is a common snow mold in Ohio and is first evident at snowmelt in late winter. Symptoms appear as circular areas of straw to grayish brown turf. The turf may also appear matted with the appearance of a grayish-white mycelium at time of snowmelt. The mycelium often dries and becomes encrusted over the patch.

Pink snow mold and/or fusarium patch is probably the most common snow mold found in Ohio. It is often associated with Typhula blight. Pink snow mold is the term used when this disease occurs with snow melts, while fusarium patch is used for the disease in the absence of snow. In both cases the organism causing the disease is Microdochium nivale. Circular patches of pinkish-orange to brown infected turf are common symptoms (photograph to the left and bottom).

The following snow molds, Coprinus snow mold and snow scald, are not common in Ohio, but are a problem farther north and west of Ohio. Coprinus snow mold (Coprinus psychromorbidus) is often associated with the northern high elevation locations where extended periods of deep snow cover occur. The pathogen, Coprinus psychromorbidus, is considered a low-temperature basidiomycete, thus the term low temperature basidiomycete is often used to describe this disease. Two strains exist of the pathogen one that produces sclerotia and the other does not.

Under deep snow, snow scald (Myriosclerotinia borealis) may also occur. Snow scald is more severe if the ground is frozen. With both Coprinus snow mold and snow scald, promoting early spring melt will help reduce disease severity.

Authors: Karl Danneberger