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Gray snow mold is a cold-weather fungus primarily affecting cool-season grasses.
Most signs of spring are the welcome kind, including buds, blooms, warmer temps, and green grass. But gray-colored circles on your lawn? Not so much. Snow mold is caused by cold-weather fungi that primarily affect cool-season grasses. Signs of a problem aren't noticeable until the spring when the snow melts.
A heavy blanket of melting snow may look really pretty, until it you see the damage it can do to your lawn. Snow mold is most problematic when you receive a heavy, deep snowfall before the ground has completely frozen. All that weight on fragile grass plants, coupled with lots of wintertime moisture, not to mention cover from leaves, long grass, and lawn debris, spells trouble in the form of snow mold. There are two types of snow mold: gray snow mold (also called Typhula blight) and pink snow mold (also called Microdochium patch or Fusarium patch).
Signs of both pink and gray snow mold are usually most noticeable in the spring when the snow begins to melt. As the snow melts, straw-colored circular patches ranging in size from a few inches to several feet across appear in the lawn. The grass in these patches is usually matted down and crusty. The patches will have a grayish-white appearance if they are caused by gray snow mold, or a whitish-pink appearance when caused by pink snow mold. Pink snow mold can be more severe than gray snow mold, as it can kill the crown and roots of grass plants; gray snow mold usually only affects the grass blades.
The key to beating snow mold is prevention, as there are no fungicide treatments that work on snow mold in the spring when the snow melts. If you have repeated issues with snow mold in the spring, you can apply a preventative application of Scotts® DiseaseEx™ Lawn Fungicide in fall (usually around Thanksgiving) before the first heavy snowfall.
If you don't apply a preventative fungicide in fall and you find snow mold damage in your lawn in early spring, the first thing you'll need to do is gently rake the affected areas to loosen any matted grass. This will help the lawn dry and give unaffected grass room to grow.
In spite of your best efforts, dead, dying, or discolored grass may never recover its healthy appearance. In that case, any damaged areas should be repaired using a patching product like Scotts® EZ Seed® Patch & Repair, as soon as the weather permits.