Snow Mold Fungus: Learn About Snow Mold Control

By: Kristi Waterworth

Spring is a time of new beginnings and the awakening of lots of the growing things you’ve missed all winter. When the receding snow reveals a badly damaged lawn, many homeowners despair – but try not to worry, it’s only snow mold. This fungus is unsightly, but is easy to manage for homeowners of all skill levels. Read on to learn more about snow mold and how to manage it on your lawn.

What is Snow Mold?

As the snow melts for the last time this spring, you may notice some unusual brown rings and matted areas on your lawn. This is the calling card of one of the more frustrating turfgrass diseases: snow mold fungus. Snow mold in grass is a problem that seems to defy logic entirely. After all, isn’t it too cold under the snow for fungi to grow?

Snow mold is actually a group of fungal diseases caused by pathogenic fungus that lie dormant in the soil until the conditions are just right to invade nearby grasses. Snow mold can tolerate more cold than most members of its Kingdom and it thrives in the conditions present under a thick blanket of snow. Because of the insulating properties of snow, the ground beneath a heavy coat of the white stuff can be completely unfrozen despite freezing air temperatures.

When this happens, the snow melts ever so slowly into the grass, creating a cool and incredibly humid environment for the snow molds to take hold. Once all that snow is finally thawed, a lawn infected with snow mold will show new straw-colored patches, rings or matted areas. It’s rare that snow mold will kill the crowns of your turfgrass, but it preys heavily on the leaves.

Snow Mold Control

Snow mold treatment starts with a thorough dethatching of your lawn. After all, the thatch helps hold moisture against the grass, so removing as much as you can at the beginning of the season is a good idea. Watch the grass for the next few weeks after dethatching. If you get new, unaffected growth, you’ll only need to keep the grass in good condition in case snow mold returns next season.

Grass that has died completely, on the other hand, will need to be overseeded. Kentucky bluegrass and fine fescue have shown some resistance to certain types of snow mold, and they may be a good solution if snow mold is a chronic problem in your area.

Once you’ve got your lawn re-established, it’s important to maintain it in a way that discourages snow mold in the winter.

  • Continue to mow your grass until the growth has stopped completely, as a tall canopy will make snow mold worse.
  • If your grass must be fed, do so in the spring so your grass can use the nitrogen up since high nitrogen environments contribute to some snow mold problems.
  • Lastly, remember to dethatch your lawn late in the fall to remove as much build-up as possible before the snows start again.

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How to Treat Snow Mold on Your Lawn

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Pink snow mold, more commonly known as Microdochium patch or Fusarium patch in areas that do not see snow cover, is caused by the fungal pathogen Microdochium nivale. This disease, which prefers moist conditions and temperatures between 32 and 60 degrees Fahrenheit, appears on lawns as circular patches up to 6 inches wide. Grass blades look water-soaked or greasy and the patches look reddish-brown or salmon-colored. Gelatinous spore masses may appear on dead grass and infected grass may have a pinkish cast in early mornings. Certain care practices usually can address Microdochium patch sufficiently and limit its presence in subsequent years.

Prune off branches on nearby trees that are hanging over the lawn area selectively, and thin out adjacent shrubs to increase the amount of light reaching the lawn and improve air circulation around the turf.

Rake up leaves, twigs and any other debris on the lawn regularly during fall and winter, as Microdochium can develop under fallen leaves and other debris during cool, wet weather.

Apply a fungicide to infected and surrounding turf areas as soon as you notice the disease. Treatment with a fungicide rarely is necessary and warranted only for highly-visible, important areas, as the fungus will disappear with the onset of warm, dry weather. Fungicides to address Microdochium patch include fludioxonil, thiophanate-methyl, propiconazole, triticonazole, and triadimefon.

Mow the lawn regularly at the height recommended for the grass species and cut off no more than a third of the grass blade height with a single mowing. Continue to mow the grass through fall as long as it still is growing.

Dethatch the lawn area in late winter or early spring once new growth begins if thatch, the layer of living and dead stems, roots and other debris between the soil surface and the bottom of the green grass blade, is thicker than 1/2 inch. Pull a dethatching rake over the soil surface in small areas or use a vertical mower, or verticutter, to break up thatch in a larger site. Monitor the thickness of the thatch layer throughout the growing season and make sure it is less than 1/2 inch thick about 45 days before the grass begins to go dormant to minimize the presence of fungal diseases during cool, moist conditions.

Aerify areas that are compacted or were severely affected by Microdochium patch the previous winter. Use a hand or machine aerifier to pull up cores of soil and leave them on the lawn. This will help to alleviate the poor drainage that encourages the disease.

Fertilize the lawn in spring when weather is relatively warm and dry, no longer favoring Microdochium patch development. Time fertilizer application for when grass is beginning to show growth, and after any dethatching and aerifying. Broadcast a complete fertilizer that contains some slow-release water-insoluble nitrogen at a rate of one pound of nitrogen per 1000 square feet of lawn. Do not fertilize the lawn in fall, as this will force a buildup of lush new growth particularly susceptible to Microdochium patch.

Water the turf deeply and infrequently, irrigating the lawn only when soil 2 inches below the soil surface feels dry to the touch and wetting the top 6 to 8 inches of soil each time you water. Shallow, frequent irrigation can contribute to thatch accumulation and constantly-moist conditions that the disease prefers.

Apply a preventative fungicide at regular intervals beginning in the fall just before the onset of cool, moist weather to areas of the lawn where Microdochium patch was present the previous year or where you have chronic problems with this disease. Fungicides to control Microdochium include thiophanate-methyl, fludioxonil, propiconazoole, myclobutanil, azoxystrobin, and chlorothalonil. Continue applying fungicide regularly to prevent the appearance of the disease, stopping when conditions no longer favor disease development. Rotate between different types of fungicide to avoid problems with the pathogen developing resistance to a certain type of fungicide.

Snow mold is a fungus that grows in circular patches on your lawn. It typically appears after the snow melts in late winter or early spring, but doesn’t always require snow to form. It comes in two varieties: Gray (Typhula blight) and Pink (Fusarium patch).

What does snow mold look like?

1. Gray snow mold

Gray snow mold is the less destructive of the two. It will appear in circular patches of flattened, discolored grass with a gray web of fungus growing over top. Typically, it only damages the blades of the grass, not getting down into the roots.

2. Pink snow mold

Pink snow mold is the more serious of the two and it doesn’t even need snow to form. After an extended period of cool wet weather, usually in the fall, you may start to notice red/brown or orange spots appearing on your lawn. These will grow as winter progresses until it takes over large portions of your lawn. This mold is worse than the gray variant because it will go after the crowns and roots of your grass, effectively killing it.

Tips for snow mold prevention

Prevention is the key to eliminating snow mold. There are a number of methods that have proven successful in the battle against the mold:

1. Fungicide treatment

The best way is to have your lawn professionally treated with a fungicide. This is ideally done in the late fall, before the first snow of the year. This should protect your lawn throughout the winter and into the spring. LawnMatters offers an excellent snow mold prevention treatment.

2. Don’t over water your lawn

Mold thrives on moisture so it is important to ration the amount of water you give your lawn as the temperatures drop. Giving your grass the bare minimum that it requires is another great way to prevent snow mold.

3. Continue to mow your lawn in fall

Make sure that you are mowing your lawn throughout the fall. Keeping the grass between 2.5 – 3 inches will make your lawn less susceptible to disease and mold. Your final mow of the year should be kept short at 2″.

4. Clear your lawn of piles of leaves and snow

In the fall it’s important to remove any piles of wet leaves. This will reduce the amount of unnecessary moisture building up on your lawn.

The same goes for piles of snow. When shoveling your driveway or sidewalk try to avoid making large piles of snow in your lawn as they will take a much longer time to melt, offering more time for the snow mold to develop.

Worried about snow mold? LawnMatters has everything you need to keep the fungus at bay, contact us today!

Tips for Prevention

In the fall, part of your winterizing maintenance should be to mow your lawn as short as possible. Long grass is a breeding ground for mold, so cutting it short before the first heavy snowfall will help prevent this disease. Short grass will also expose the ground, allowing it to freeze more quickly.

Rake Your Leaves

Raking leaves in the fall has plenty of benefits, but clearing your lawn before winter is another way to prevent snow mold. A thick layer gives mold and other winter diseases a chance to grow, so mulch or rake the fallen leaves to help protect your lawn.

Go Easy on Late-Season Fertilizer

Nitrogen-rich fertilizers are great in the spring and summer months for rapid growth and green grass. However, you should avoid using these fertilizers in the fall as they can invite mold into your lawn during the winter. Instead, try using a slow-release lawn food until winter arrives.

For residential and commercial properties in Salem, OR, snow mold and other winter damage can be unsightly once the snow melts in the spring. At Green Acres Landscape, we offer a variety of winter landscaping treatments. If you see any dead, grey, or pinkish patches in your lawn this coming spring, make us your first call by dialing (503) 399-8066.

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Usually, snow mold can stay inactive in the ground fungal structures or spores immune to high summer temperatures. In late winter, when the temperatures beneath the piles of snow are slightly between below freezing to about 45 F, the spores or fungal structures resume active growth.

As the snow melts from the earth surface, the aggressive fungal growth keeps thriving and spreading until the earth surfaces dry out or temperatures are gradually above 45 F. Pink snow mold is a little more persistent, as long as the grass is moist, and temperatures are between 32 F and 60 F, it keeps growing.You can treat snow mold within a few weeks using the following lawn treatment tips

#1. Apply fertilizer regularly.

Because snow mold only affects the grass blade at the early stage, fertilizing will enable your grass to push new growth and “outgrow” the fungus.

#2. Mow your lawn regularly

You’ve got make up your mind to mow your lawn regularly because tall grass holds more moisture, and they are vulnerable to snow mold.

Mow the lawn at a length that is shorter than the usual, to minimize the moisture trapped under the first snowfall of the season. Continue this until the mold is no more actively growing. Ensure you clear out all grass shavings after mowing.

#3. Gently rake over the affected areas to dry out the discolored patches quickly

Rake lightly so as not to tear out all the grasses. Raking out the loose grass allows air to circulate the affected spots and boost the recovering process of the lawn grass.

#4. Detach any thatch layer that is above 1/2 inch thick

Wait until the moisture has dried out moderately from the lawn, and you have mowed two or three times before removing thatch. Mechanical dethatching machines are known to damage fresh grass sprouts in the spring.

#5. Overseed the bare areas

For severe snow molds, overseed the bare areas. In this case, you should not fertilize or mow these seeded areas until the new grass is actively growing.

#6. Apply fungicides to treat your lawn of snow mold

This should be a last resort. You should delay using chemicals on year lawn because in most cases of snow mold, with proper care, the grass heals itself. Except in severe occurrences when the disease persists, then you can apply fungicides to clear the fungus.

Stopping Snow Mold Before It Starts

The best way to keep your lawn lush and healthy is to prevent snow mold from growing in the first place. The following steps will keep the fungi at bay.

  • Avoid fertilizing within six weeks of the first expected snowfall in your area to allow your lawn to go dormant. Dormant grass blades are dry and dehydrated—far less hospitable to snow mold.
  • Mow the lawn to a height of 1½ inches in the fall when grass turns yellow and stops growing, signs that it is going dormant.
  • Rake up dry leaves before they can decompose on the lawn.
  • Dethatch lawns with a thatch rake, such as Ames 15-inch Adjustable Thatch Rake (available from Amazon). The best way to control thatch is to rake it away two or three times a year, during your lawn’s active growing period in summer and in fall.
  • Fill low spots in your yard with topsoil to encourage water to drain off rather than sit in those areas.
  • Apply a preventative turf fungicide, such as Scotts DiseaseEx Lawn Fungicide (available from Amazon) in late fall, just before the first heavy snow is set to arrive. This acts as a barrier to freeze-tolerant snow mold.

Melting snow can trigger snow mold allergies

Snow mold forms when snow partially melts but still covers the ground.

Early-spring allergies don't just come from pollinating trees and grasses. They can start up even before the trees have regained their leaves and the grass has started growing again. If you live in an area that got a lot of snow this winter and you're experiencing allergy symptoms earlier than usual, there may be an unexpected culprit: snow mold.

Snow mold makes its home in the pockets of dampness on the ground that occur when accumulated snow begins to melt but still covers the ground. Damp, dead grass covered with snow provides ideal nourishment for the fungus. Once the snow has completely melted, the mold's spores begin to be released into the air, which is what causes allergic reactions in people with mold allergies.

There are two main types of snow mold: gray and pink. Gray snow mold grows mainly on blades of grass, while the pink version attacks the roots and crowns of the plant and takes on a sickly bright pink color as it develops.

To avoid letting snow mold form on your lawn, there are several things you can do this spring. One is to break up any remaining snow banks once the snow starts to melt, allowing them to melt faster and avoiding letting the snow cover the damp ground. If you have to rake up debris from the lawn this spring and you know you have mold allergies, wearing a simple face mask can help you get through the task without triggering allergic symptoms.

If you suffer from allergies in the spring, one of the best things you can do for yourself is invest in a home air purifier. For help finding the best air purifier for allergies, contact US Air Purifiers today.

Watch the video: Bayer Beyond the Basics: Snow Mold and Winter Damage Prevention

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