October 21, 2020

Gray Snow Mold is a common winter disease of creeping bentgrass on golf course greens in central Iowa.  It is caused by the fungi Typhula incarnata (and a few other species) It occurs during the winter, usually under snow cover.  We generally see the cottony mycelia of the organism as the snow melts in the spring. 


This disease has a resting stage called “sclerotia” (see picture below).  These are quite large and can be seen with the naked eye.  Under just the right conditions, the sclerotia will germinate, which results in rather large white to brown fruiting bodies.  These can be one half inch or more.  The germinating sclerortia pictured below are standing erect, but they can also result in a “fiddle head” like appearance as they emerge.  It is very rare to see the germinating sclerotia.  The conditions that bring this about is an early snow fall on actively growing turf, such as we just had in central Iowa.  Watch your greens for this phenomenon and send me some pictures if it shows up.  I have only seen it twice in 41 years.  They will go away very quickly. 


These are the sclerotia as they appear on creeping bentgrass.

This is what the germinatiing sclerotia look like just after an early snow melts.


The pictures are from the American Society of Agronomy turfgrass disease slide set.