Understanding and Managing Snow Mold in Turfgrass

Snow mold is a common cool-season turfgrass disease that appears after snow melts in late winter or early spring. It can be caused by three different pathogens: gray snow mold (Typhula incarnata and Typhula ishikariensis), pink snow mold (Microdochium nivale), and speckled snow mold (Typhula ishikariensis). While all are favored by extended snow cover, they differ in their specific biology, severity, and geographic prevalence. For turf managers in northern climates, snow mold can cause extensive injury, leaving turf thinned, matted, and slow to recover in the spring.

Symptom Development

Gray and speckled snow mold symptoms can vary widely, appearing as light yellow, reddish-brown, straw-colored, or grayish-brown patches. Whereas pink snow mold is characterized by pink, white, or tan patches of dead, matted leaf blades often surrounded by an outer ring of copper-colored turfgrass.

• Patch size: These may range from a few inches to a foot in diameter, with some patches coalescing into blighted patches several feet wide.
• Signs: During times of receding snow cover, grass blades are often matted together with a cottony, web-like fungal growth that may be grayish-white (gray and speckled snow mold) or pink (pink snow mold).

Left unmanaged, snow mold injury can thin turfgrass stands, reduce uniformity, and leave areas unplayable during recovery.

Environmental Conditions Favoring Snow Mold

Snow mold thrives under prolonged periods of snow cover. In areas with frequent snowfalls and slow melt cycles, the disease can persist and spread throughout the winter season. Key conditions include:

• Cool temperatures (30–60°F) are conducive for disease, with high moisture in this temperature range being the primary factor driving development.
• Extended snow cover (more than 60–90 days), which insulates the soil and maintains favorable fungal growth conditions in the turfgrass canopy.
• Dense turf or excessive thatch, which provides an ideal environment for pathogen development because it retains moisture and reduces air circulation at the turf surface.
• Late-fall fertility programs with high nitrogen, which leave turfgrass lush and more susceptible to infection.

Cultural Control Strategies

Cultural practices are the first line of defense to reduce the severity of snow mold. Although these strategies won’t eliminate snow mold, they can significantly lessen its impact.

• Balanced fertility: Avoid excessive nitrogen applications in late fall; instead, focus on potassium and micronutrients to enhance winter hardiness.
• Thatch management: Dethatching and aeration in the fall improve airflow and reduce fungal habitat.
• Mowing: Continue mowing until turf stops growing to avoid leaving long, matted grass under snow cover.
• Debris removal: Leaves and clippings should be removed to prevent moisture entrapment.
• Snow management: Where possible, avoid piling snow in shaded areas where it will prolong cover.

Fungicide Applications for Snow Mold Control

While cultural practices help reduce risk, preventative fungicide applications remain the most reliable tool for snow mold management in high-value turfgrass, especially golf courses and sports turf.

Application Timing and Techniques

• Fungicides should be applied in late fall, just before the first long-lasting snow cover.
• Coverage is critical: applications should be made in high spray volumes (2 gallons/1000 ft² or more) to ensure fungicide penetrates the canopy.
• Avoid post-application irrigation that would move the fungicide through the canopy and thatch layer where the pathogen resides.
• Mixtures of multiple fungicide active ingredients remain the only reliable method for suppressing snow mold, particularly in sites prone to both gray and pink snow mold, as they provide the broad-spectrum activity needed to protect turf against the full range of pathogens.

Enclave Fungicide for Snow Mold

Enclave fungicide is a premier solution for snow mold control due to its quadruple-active formulation:

• Chlorothalonil (multi-site contact activity)
• Iprodione (dicarboximide)
• Thiophanate methyl (systemic activity)
• Tebuconazole (DMI)

This multi-site, multi-mode approach provides broad-spectrum activity against all three types of snow mold, ensuring durable and reliable performance under heavy disease pressure.

Enclave’s combination of systemic and contact activity allows it to protect turfgrass crowns, foliage, and soil surface from infection throughout the winter. When applied properly before snow cover, it provides season-long protection until spring, helping turf emerge healthier, denser, and ready for play or maintenance.

Proven Performance

University trials led by Dr. Paul Koch at the University of Wisconsin during the 2020–2021 winter season demonstrated outstanding control of pink, gray, and speckled snow mold with a single Enclave application in late fall (October–November), providing consistent, season-long protection even under intense disease pressure.