WSU Extension

Hortsense

Lawn and Turf : Typhula blight (Gray snow mold)
(revision date: 1/22/2016)


Biology
Typhula blight is a fungal disease which can occur beneath snow cover on unfrozen soil. Under snow, light yellow to gray circular areas develop. These range in size up to a foot or more in diameter. Grass leaves are matted together and may be covered with a fluffy, grayish to white fungal growth, particularly near the margin of the patch. Small dark fungal structures often speckle the white mats. In cool, moist conditions such as under wet leaves, the disease usually appears as circular, yellow or brownish areas 3"-6" across. Typically only the leaves are killed by Typhula blight, but occasionally roots and crowns are also killed. Excessive thatch, high late fall fertility, and poor drainage contribute to disease development. Typhula blight often occurs in conjunction with Fusarium patch.
Management Options

Non-Chemical Management
  • Mow regularly at recommended height until grass stops growing in the fall. Remove clippings.
  • Rake leaves and mulches off lawns prior to snowfall.
  • Provide adequate, balanced nutrition. Avoid excessive nitrogen in late fall. Fertilizers with moderate levels of nitrogen or slow-release fertilizers are best for fall use.
  • Provide good drainage.
  • Remove thatch and aerify as needed.
  • Avoid compaction of snow. Remove snow from disease-prone areas in the spring.
  • For more information on proper care of lawns see EB0482E, Home Lawns.
Select non-chemical management options as your first choice!

Chemical Management

Make applications prior to snow cover. Reapply fungicides if snow melts. Do not repeatedly apply the same fungicide or fungicides with the same active ingredient as tolerant strains may result. Carefully check product labels.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • ferti-lome Liquid Systemic Fungicide II R-T-Spray
    Active ingredient: propiconazole  |  EPA reg no: 53883-184-7401
  • This list may not include all products registered for this use.
Images
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Caption: Typhula blight
Photo by: R.S. Byther
Caption: Typhula blight fruiting bodies
Photo by: R.S. Byther