Snow Mould

Submitted on March 20, 2018

In some parts of the Maritimes this winter there has not been much snow and there is more bare ground than is typical for March. If your lawn is free from snow, you may see snow mould in areas that were covered with snow and ice.

What is snow mould?

Snow mould is a fungal disease that is most prevalent when we’ve had heavy winters with extended periods of snow cover. The fungi live in thatch, soil, and dead leaves within the lawn all year long, feeding on grass nutrients and destroying vital plant cells in the process.


Snow mould most often appears in circular patches of dead or matted grass. Patches will often join together to become a large, discoloured mass, causing your grass to look dead or tired. Gray snow mould (Typhula blight) may result in tiny black sclerotia (hardened fungi) on the plant, and makes infected areas turn light brown, gray, or straw coloured. Pink snow mould (Fusarium patch), appears in the form of yellow, tan, or salmon-coloured patches, and is more damaging because it affects both the crown and roots of the grass, rather than just the blades.

Click here to see a picture of pink & gray snow mould in a home lawn. (Source: Ontario Ministry of Agriculture Food and Rural Affairs)


Snow mould primarily affects lawns that have become nutrient deficient over the winter due to harsh, seasonal conditions and excessive snow coverage. A poorly timed application of fall fertilizer on your lawn may also play a role in the disease. High nitrogen levels can cause a growth surge too late into the cooler season, leaving your lawn more susceptible to winter damage.


  • Fall fertilizations should be properly timed so excessive top growth is not encouraged too late into the season
  • Mow the lawn until it stops growing to minimize foliage exposed to winter elements
  • Rake leaves in the fall. If the disease is already present, rake affected areas in the spring and remove lawn debris.
  • Aerate your lawn yearly to improve drainage and manage thatch; which can both contribute to snow moulds

Fertilization, topdressing, or reseeding may be necessary depending on the severity of snow mould damage. Your friends at Weed Man can help you tackle this problem by providing a free healthy lawn analysis to help identify problems that may stand in the way of a lush, green lawn.

For more information about dealing with winter damage in your lawn, click here.


[Revised from original post by Weed Man Canada, April 8, 2014.]


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