What is snow mold?
Snow mold is a fungal disease that appears in the early spring as the snow melts. There are two types of snow mold. Grey snow mold (also known as Typhula blight) and pink snow mold (sometimes referred to as Fusarium patch). Pink snow mold infects the crown of the plant and can cause more severe injury than gray snow mold which only infects the leaf tissue.
What does it look like?
Snow mold damage looks like circular patches (3"-12") of dead and matted grass. Depending on the severity of the outbreak, the circles can coalesce and become a large mass. It is not uncommon to find both gray and pink snow mold together.
Pink snow mold is distinguished by the pink color of the web-like mycelium growing on the grass surface. While the grass is wet, the mycelium starts out white and resembles cobwebs, as it matures it turns its pink or salmon color. The mycelium quickly disappears as the grass dries.
Gray snow mold is similar to pink snow mold except that its mycelium remains whitish-gray. Gray snow mold is also distinguished by the presence of tiny black mycelial masses (sclerotia) on the grass blades and leaf sheaths of infected plants which pink snow mold does not produce.
What causes snow mold?
Snow mold is caused when there is an extended period of snow cover on ground that is not completely frozen. It can also be brought on by a badly timed fertilizer application which causes a flush of growth too late in the fall. Snow mold can also occur under leaves that have not been cleaned up or amongst long grass that should have been mowed once more before winter set in.
How is snow mold prevented?
To minimize the risk of snow mold occurring on the lawn it is important to "put the lawn to bed" properly.
- Avoid excessive nitrogen fertilizers in the fall,
- mow the lawn until it stops growing,
- clean up leaves in the fall,
- manage thatch to avoid accumulations of more than 2"
How do I repair snow mold damage?
Fungicides are available for both preventive and curative treatments of snow mold. However, they are not recommended due to the largely superficial and temporary damage snow mold inflicts on the lawn.
Although it can look really nasty in the early spring, most snow mold damage will recover in time. Once the area has dried, the infection will cease and the turf will grow out and renew itself. To speed up the process, the infected area can be lightly raked to encourage drying. Some overseeding may be necessary and if the damage is extremely severe, topdressing can be applied and areas can be repaired like a bare patch.