What is Gray Snow Mold and How Do You Get Rid of It?

brown spots on grass, along with wispy white mold

The temperatures are rising, the birds are singing, the snow is melting, and your lawn is growing –– mold? If patches of turf mold are replacing the melting snow, your lawn may be suffering from gray snow mold (not to be confused with pink snow mold). 

What is gray snow mold, and how do you get rid of it? How did your lawn get moldy in the first place? Our guide to gray snow mold will show you how to nurse your grass back to health and how to prevent reinfection.

What is gray snow mold?

Gray snow mold is a turfgrass disease that affects all cool-season turfgrasses. 

The fungal disease can be caused by either two pathogens: Typhula incarnata and Typhula ishikariensis. 

  • Typhula ishikariensis infections may result in plant death as the disease progresses down into the crown. 
  • Typhula incarnata infections are typically less severe and recover more quickly. 

How to identify gray snow mold

Correct identification of turfgrass disease is the key to successful treatment. If you misidentify the fungus growing in your lawn, then your control measures might have little effect on the disease. 

If you suspect gray snow mold is growing in your lawn, here are the symptoms to look for: 

  • The first signs of gray snow mold appear as the snow melts in early spring or late winter. That’s because disease development occurs underneath deep snow covers and remains out of sight until the snow recedes. 
  • Gray snow mold appears as circles or irregular patches up to 3 feet or more in diameter. The grass within these patches is white or gray, brittle, and matted. 
  • Infected turf may be covered in a web-like substance called mycelium. Mycelium is most evident during and right after the snow melts. 
  • Tiny structures called sclerotia are embedded in dead grass blades and are visible to the naked eye. Typhula ishikariensis sclerotia are dark brown or black, and Typhula incarnata sclerotia are reddish-brown or tan. 

How to get rid of gray snow mold

Gray snow mold might be an eyesore in the yard, but it doesn’t have to last for long. The right lawn care treatments combined with the warm spring temperatures will green up your lawn in no time. 

  • Remove snow drifts that are piling up in the yard. The longer they remain on the grass, the more severe the disease. 
  • Rake crusted, matted areas to help increase air circulation and remove excessive thatch
  • Promote new growth with light fertilization. Do not use high amounts of nitrogen fertilizer. 
  • Overseed affected areas. 

Chemical control: It may be tempting to spray gray snow mold with fungicide, but this control method is not reliable. Fungicides for gray snow mold are more effective as preventative measures than curative treatments. The best cure for gray snow mold is warm temperatures and maintenance. 

How to prevent gray snow mold

Don’t want gray snow mold to make another visit in your yard? The good news is there are preventive measures you can take: 

  • Mow the grass until late fall. Tall, lush grass in winter is an attractive environment for gray snow mold. 
  • Remove piles of leaves and other plant debris in the yard. 
  • Remove snowdrifts that pile up in the yard. 
  • Prevent snow accumulation by installing snow fences and wind barriers
  • Don’t apply high levels of nitrogen fertilizer in autumn, especially before the first snowfall.
  • Reduce compact snow caused by skis and snowmobiles. Compact snow takes a long time to melt, increasing the chances of disease. 
  • Remove excessive thatch. 
  • Preventing gray snow mold with fungicides is not always necessary for home lawns. If you need to protect a recently seeded lawn, golf course, or sports field, apply a preventative fungicide in the fall before the first snow cover.

What causes gray snow mold?

Gray snow mold loves the cold, wet environment underneath snow covers. It requires 40 to 60 days of snow coverage before it can develop, and the ground must not be frozen.

But snow isn’t the only environmental factor that causes this disease to occur. Some of your lawn care practices (or lack thereof) could be encouraging mold growth. Let’s take a look at some of the common triggers for gray snow mold growth: 

  • Gray snow mold occurs after 40 to 60 days of snow coverage and unfrozen soil. 
  • High amounts of nitrogen fertilizer
  • Piles of leaf litter
  • Lush grass that wasn’t cut before winter
  • Grass that was cut too short before winter (this is common on golf courses)
  • Grass seed planted in the fall did not have enough time to mature before winter

How does gray snow mold spread?

Gray snow mold lies dormant in sclerotia, the small structures that embed themselves in dead turf. When cold and wet weather arrives in the late fall, the disease becomes active. 

The sclerotia produce mycelium (the web-like substance), which spreads from leaf to leaf and infects healthy grass blades. The infection process occurs underneath a snow cover when the ground is unfrozen. 

Once the snow melts and warm weather returns, the fungal mycelium forms sclerotia, and the disease returns to dormancy. 

What grass types are susceptible to gray snow mold?

All cool-season grasses are susceptible to gray snow mold. According to the PennState Extension, Kentucky bluegrass and fine fescues are less prone to injury than creeping bentgrass, annual bluegrass, tall fescue, and perennial ryegrass. 

Gray snow mold vs. pink snow mold

If the snow mold patches in your yard have a pinkish hue and don’t have sclerotia, then the disease may be pink snow mold. These two types of snow molds are similar, but they do have their differences.

Pink Snow MoldGray Snow Mold
Develops underneath snow covers when the ground is unfrozenDevelops underneath snow covers when the ground is unfrozen
It can develop in cold, wet conditions without a snow coverDoes not develop without a snow cover
Develops circular patches typically 2 to 10 inches in diameterDevelops circular patches typically 1 to 3 feet in diameter
Patches contain matted grassPatches contain matted grass
The patches appear gray, tan, or light pink and contain a white center. The grass within these patches usually has a pinkish hue.Patches are white or gray and do not have a pinkish hue 
Develops myceliumDevelops mycelium
Infected grass blades do not have sclerotiaInfected grass blades have sclerotia

FAQ about turfgrass disease

1. What other grass diseases can infect my lawn?

Gray snow mold and pink snow mold aren’t the only turfgrass diseases that can ruin your lawn. Your lawn is susceptible to several diseases, including: 

Anthracnose 
Brown patch
Dollar Spot
Fairy ring
Leaf spot and melting-out 
Powdery mildew
Red thread 
Rust 
Summer patch 

2. How do I prevent turfgrass disease?

The secret to preventing fungal growth in the lawn is good lawn care maintenance. Yard work might be the last thing you want to do, but if you ignore your lawn for too long, a fungus just might destroy it. 

Here are 15 lawn care treatments you can perform to keep those lawn diseases at bay: 
Remove leaves and other debris from the lawn. Many lawn diseases will remain dormant in plant debris. 

Mow the grass regularly (and correctly). Cutting more than ⅓ of the grass blade at a time will stress your turf. Don’t mow so low that you scalp the lawn, but don’t encourage overgrown grass either. 

Leave behind grass clippings. Grass clippings increase long-term lawn health by acting as mulch. But remember, don’t leave behind clippings of infected grass. 

Perform proper irrigation practices. Watering your grass the wrong way can make your lawn more inviting to disease. Water your lawn less often for long periods to promote a strong root system. Watering too often for short periods encourages a weak root system. And remember to water at the right time of day, too. 

Invest in a sprinkler system. Sticking to a watering schedule isn’t always easy. An automatic sprinkler system can help ease the burden of your watering chores while giving your lawn the exact amount of water it needs. 

Plant grass seed that’s disease-resistant and suitable for your lawn. Not just any grass seed will grow well in your yard. You’ll want to plant grass that’s compatible with your local climate. Talk to your lawn care pro about what grass type is the best for your area and which varieties are the most disease-resistant. 

Test your soil. A healthy lawn needs healthy soil. Perform a soil test to determine what nutrients your lawn might be missing. 

Fertilize your grass. After a soil test reveals what nutrients are missing, create a fertilization regime that gives your turf the right level of nutrients at the right time of year. 

Aerate compact soil. Compact soil stresses your lawn by preventing oxygen, water, and nutrients from reaching the roots. An aerator relieves compact soil by creating small holes in the ground. 

Remove thatch that exceeds ½-inch thick. Thatch is the dead organic matter that accumulates between the soil and turf. A thin layer of thatch can be healthy for your turf. But if it gets too thick, it becomes an inviting place for fungal diseases to remain dormant. 

Overseed the lawn. Is your grass thinning and developing bare patches? The key to maintaining a dense, green lawn is routine overseeding. 

Remove existing weeds. Too many weeds growing in the yard can put stress on your grass. Instead of directing its energy towards growing strong, your lawn must outcompete weeds for nutrients, moisture, sunlight, and space. You can remove weeds by hand-pulling them or spraying a post-emergent herbicide.  

Apply pre-emergent herbicide. Pre-emergent herbicides help prevent weeds from establishing. 

Control grubs and other pests. Grubs weaken lawns by eating the root system. 

Spread a ½-inch layer of compost across the lawn. Compost acts as organic fertilizer by adding nutrients to the soil. Spread a compost top dressing with a rake or brew a compost tea and spray it on the lawn.  

3. Can I control turfgrass disease with fungicides?

Fungicide effectiveness depends on the turf disease you’re dealing with. Fungicide can help cure some turf diseases when combined with lawn care adjustments, but many turf diseases quickly develop a resistance to the fungicide. Fungicide applications are typically more helpful as preventive treatments than curative treatments. 

4. What if I can’t identify the fungus on my lawn?

Identifying the fungus growing in your lawn isn’t always a walk in the park. Proper identification is essential because control measures that work on one kind of fungal disease might not work on another. 

If you can’t identify the turfgrass disease, contact a diagnostic lab or turfgrass pathology lab for help. These labs specialize in diagnosing turfgrass diseases and are often located at state universities.

Leave the mold to the pros

Whether you’re dealing with gray snow mold, pink snow mold, or a different turfgrass disease, there’s little fun to be had with fungus in the yard. Instead of spending your free time combing mold out of your grass, hand the job over to a local lawn care professional

Not only can a lawn care pro treat your lawn for turfgrass disease, but they can also help prevent these diseases from reoccurring. Mowing the lawn, testing your soil, applying fertilizer –– that’s a lot to pack into your busy schedule. Why spend your free time preventing fungus when you could be enjoying the weekend with family and friends?

Main Photo Credit: Kris Lord | Flickr | CC BY 2.0

Jane Purnell

Jane Purnell is a freelance writer and actor in New York City. She earned her B.A. from the University of Virginia and enjoys a warm cup of French press coffee.