Snow Mold Damage...How Bad is it and What Can be Done?

By Todd Hicks

As the winter finally draws to a close, snow-mold damage may be one of our first issues to deal with for 2025. Due to the prolonged snow cover this winter, chances are high that there may be more damage from this disease than experienced in past years.

Snow mold is active at temperatures just above freezing in moist conditions. The gray snow molds (Typhula incarnata, also called Typhula blight, and Typhula ishikariensis) most often occur when snow cover exceeds 40 to 60 days. Pink snow mold (Microdochium nivaile), however, does not require any snow cover to develop. The freezing and thawing of snow on grass, plus excessive ice buildup, is the major cause of snow mold and can cause winter damage to turfgrasses.

Bentgrasses and Poa annua are especially susceptible to damage, but all cool-season grasses can be affected. With pink snow mold, which is probably the most common snow mold found in Ohio, circular patches of pinkish-orange to brown infected turf are common symptoms. Typhula blight symptoms appear as circular areas of straw-colored to grayish-brown turf. The turf may also appear matted, with the appearance of a grayish-white mycelium at time of snow melt. The mycelium often dries and becomes encrusted over the patch.

If damage from gray snow mold is present, little can be done to undo the damage, so your focus should be on recovery. To help determine the extent of damage, take samples of affected turfgrass and bring them into an environment that is conducive to growth (warm temperatures and light). To assess potential turf recovery, observe the growth of the plants, watching for the development of new shoots. It would be recommended to photograph and document the process, to demonstrate the potential recovery of the turfgrass.

• Remove snow and ice from turfgrass areas (this is easier said than done).
• Lightly rake the grass to promote air circulation and to allow light to penetrate the canopy and encourage new shoot and leaf develop.
• If there is any dead or matted material, rake and remove it. In the case of dead turfgrass, renovation of the site would be recommended as soon as possible.
• If the site did not receive appropriate fertility in the fall, a modest application of started fertilizer would be recommended.
• For gray snow molds, the damage is done, so fungicide applications are of little to no benefit at this time. In the case of pink snow mold (or microdochium patch, the common name for the disease when it occurs without snow), fungicide applications may be recommended, especially if wet conditions are experienced during the spring. Some fungicides to consider for pink snow mold would be fludioxonil, iprodione + chlorothalonil, iprodione, propiconazole, pyraclostrobin, thiophanate-methyl or trifloxystrobin.

To identify gray snow molds, look for the sclerotia (a compact mass of mycelium that is the survival structure of the pathogen, see Figure 1) on the leaf tissue and debt.

Typhula incarnata has reddish-brown to dark-colored sclerotia that are rather large, up to 0.2” in diameter (Figure 2). Typhula ishikariensis has much smaller sclerotia that appear similar to flecks of black pepper on the leaves and debt. Active mycelium is a white to gray color.

Pink snow molds do NOT produce sclerotia, and the active mycelium is a pinkish to white color, depending on exposure to light. Both gray and pink snow molds occur together, so it can be difficult to assess which is the predominate pathogen (Figures 3-5).

Todd Hicks is a Turfgrass Pathology Program Coordinator in the Department of Plant Pathology at The Ohio State University.