Microdochium patch (Microdochium nivale), often referred to as pink snow mold, is a disease that can affect most cool-season grasses. Unlike its cousin gray snow mold (Typhula spp.), Microdochium patch does not need snow cover to develop. It will develop and grow in cool (32-46 degrees F), wet and overcast situations. At this time of the year, developing disease will not be under snow, which influences identification. Patches that develop without snow cover generally appear as small bronze or light brown spots. An easy identifier is the grey or brown “smoke ring” that develops on the outer edge.
In addition to weather conditions, high late-season nitrogen rates, excessive thatch and poor drainage can also contribute to outbreaks. One thing I want to highlight in particular is shade. I saw Microdochium patch on a few tees and fairway edges last week, always in shaded areas that are inherently weaker and wetter. In fall, grasses don’t absorb as much water as they do during summer so any water in the form of rain or irrigation will linger longer at the surface than it would have a few months ago, making these areas more susceptible to disease development. Lower sun angles and cooler temperatures also contribute to longer periods of wetness.
I always recommend that courses improve drainage, dilute thatch and have a robust fungicide program to control diseases, but sometimes the answer is as simple as tree removal. If you’re struggling with Microdochium patch in shaded areas, removing a few trees is a more effective and sustainable solution to the problem than relying on chemical disease control and other temporary fixes.
Northeast Region Agronomists
Darin Bevard, senior director, Championship Agronomy – dbevard@usga.org
Elliott L. Dowling, regional director, East Region – edowling@usga.org
Brian Gietka, agronomist – bgietka@usga.org