TechNotes Dec. 9 – Snow Mold, Turf Hardening, Soil Temps

SNOW MOLD DESCRIPTION. With cold weather arriving and snow throughout the Great Lakes and the New England regions snow mold season always brings concerns.  Although symptoms are for the most part still a few months off, knowing what to expect should be of interest.
 
Typhula blight (Typhula incarnata) is first evident at snowmelt.  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.  A diagnostic key to Typhula blight is the appearance of small hard spherical fruiting structures called sclerotia.  Often times these sclerotia appear reddish to reddish-brown in color.
 
Pink snow mold and/or fusarium patch 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. 
 
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.

TURF HARDENING. With the arrival of cold temperatures the freeze (or cold) tolerance of turfgrasses becomes of interest.  Turfgrasses become their hardiest during the months of December and January.  Turfgrasses that produce rhizomes or stolons are also protected from cold temperatures through the insulating or moderating affect of soil or snow cover.  Turf that contains a significant amount of thatch is more likely to suffer freeze injury.  Thatch is a porous unbuffered media where wide fluctuations in temperature can occur.

SOIL TEMPERATURES.