How to Kill Lawn Mold
Fescue grasses are resistant to mold.
Do not apply high-nitrogen lawn fertilizers in autumn if your area is prone to winter grass mold.
Mold can cause large patches of your lawn to appear dead or diseased. Snow mold, a common occurrence in cold climates, is caused by the fungus fusarium. Pink snow mold attacks the leaves, crowns and roots of the grass. In summer, fusarium may surface in shaded areas and form a substance called powdery mildew. Gray snow mold is not as severe as pink snow mold and usually only attacks the grass blades. Prevention is preferable but commercial cures are available if necessary.
Mow grass in the fall until it stops growing, or until the first snowfall. Keep your grass short enough that the blades don't easily bend over and become matted.
Remove straw and other mulches from the lawn before it snows. Rake the lawn well after each mowing in late fall to remove leaves and grass clippings.
Shovel snow from sidewalks and driveways onto unused sections of paving or areas in the yard without grass. Avoid piling snow on top of the lawn.
Break up packed snow from pathways across a snow-covered lawn. Use the blade of your snow shovel; do not dig into the grass beneath the snow.
Check for areas that appear matted and discolored in the spring after the snow melts. Rake the areas to break up the mats and clumps so mold cannot breed.
Trim trees in spring and summer over areas experiencing powdery mold symptoms. Trim enough from the trees to allow sunlight to reach the affected areas and kill the mold.
Apply a chemical fungicide to affected areas if they don't show signs of improvement, or if you cannot remove shade sources from the area. Purchase fungicide at a garden supplier and apply it according to the package directions.