What is snow mold and what can I do about it?
Snow mold (lat. Microdochium Nivale) is, contrary to what its name suggests, not bound to frost or snow. It feels most at home in high humidity such as dew and fog and alternating low, cool and high temperatures around 0-8° Celsius. If there is snow on the unfrozen lawn, this also favors the development of snow mould.
Other factors that can be the cause of snow mold:
Heavy mechanical tilling of the lawn in the fall and high nitrogen applications in late fall
Potassium deficiency
a compacted soil
a high pH value
At the beginning, small, watery gray spots, also known as "wet rot", appear about 5 centimeters long. These spots can grow up to 25 centimeters and merge into one another. The disease grows from the inside out. At the edge of the fungus, the active zone is often visible as a brown to orange-colored ring. The grasses regenerate from the center outwards. At high humidity, a white-grey to pinkish cotton wool-like mycelium appears;
Avoiding moisture or the possible influence of moisture, i.e. keeping the lawn dry in autumn and at the same time fertilizing with little nitrogen, helps to prevent snow mould. Therefore, even in late fall Potassium fertilizer and leaves, branches, clippings etc. should be removed from the lawn. Other preventative measures include scarifying in spring, the use of Turbogreen lawn aerator to reduce felting, longer drying phases during irrigation and regular light "topdressing" (Sanding).
Promoting factors:
Alternating high and low temperatures
High humidity (dew, fog)
Snow on non-frozen ground
Heavy mechanical tilling of the lawn in the fall
High nitrogen application in the fall
Potassium deficiency
high pH value
Compacted soil
Preventive:
little nitrogen in the fall
Potassium fertilization in late spring
Reduce thatch
Light topdressing (sanding)
Remove leaves, branches, clippings etc. from the lawn
No lime application in the fall
Scarifying in spring.
Avoid moisture, keep the lawn dry