Integrated Pest Management

Gray Snow Mold

Typhula sp.

Gray Snow Mold

Gray snow mold (Penn State Department of Plant Pathology and Environmental Microbiology Archives,

Gray Snow Mold

Gray snow mold (William Brown, Colorado State University,

Snow Mold

Snow mold (noricum,

Hosts, Symptoms & Signs

  • affects all grass types
  • circular patches visible after snowmelt
  • size of spots ranges from 1 inch to 2 – 3 feet
  • leaves are matted and often white to gray mycelium is visible (disappears after desiccation)
  • typically only leaves are infected
  • plants regrow as soon as temperatures rise
  • small, hard, reddish-colored fruiting structures (sclerotia) can be seen on grass; the sclerotia are the fungal survival structures

Disease Cycle

  • oversummers as sclerotia (hard balls of fungal tissue in plant debris)
  • sclerotia germinate under wet and cold conditions
  • resulting mycelium infects turfgrass under snow cover
  • newly formed sclerotia oversummer again and cause new infections the following fall in the same location

IPM Recommendations

  • Avoid heavy nitrogen fertilizer in fall to avoid fast growth of grass before snowfall. Fertilizer should be applied a few weeks prior to dormancy to stimulate root growth.
  • Mow until late fall to avoid snow falling on tall grass and weighing it down.
  • Avoid compaction of snow by skis, etc., and large snow drifts.
  • Apply a fungicide (azoxystrobin; iprodione; propiconazole) as a preventative treatment in fall; these fungicides are not useful as a curative treatment.

For more information, see our Snow Mold on Turfgrass fact sheet.