How to Identify and Treat Grass Fungus

two mushrooms seen through blades of grass, in a lawn

When your lawn starts to look more pink than green, that means something weird is growing on your grass –– fungus!

But not every fungal disease is pink or comes with a batch of mushrooms (which, no, you shouldn’t eat). Learn how to identify and treat lawn fungus so you can keep your turfgrass green, healthy, and mold-free. 

What is turfgrass fungus?

Like a shapeshifter, turfgrass disease can appear in many different colors, textures, and shapes on your lawn. Parts of your yard might be spewing different shades of red, you might identify web-like mold growth, or perhaps unusually shaped patches are popping up in the turf.

If this chaos sounds like your lawn, then a fungus is likely the culprit.

How to identify grass fungus

But there are some signs you should keep a watchful eye out for, since the earlier you detect signs of fungus in your yard, the sooner you can deal with the problem. Here are some signs that might indicate a fungal disease has infiltrated your yard:

  • Yellowing or dying patches of grass
  • Round or circular patches of dead grass
  • Thin red strands standing among your grass
  • Discoloration in grass
  • Grass looks dull or frayed
  • Powdery substance is coating the grass blades
  • Any off-color spots on your grass that might be orange, purple, white, red, black, or gray
  • Fuzzy or slimy growth on grass
  • Mushrooms or other fungal growth

11 types of fungal turfgrass diseases and how to treat them

To treat a fungus in your yard, it’s important to identify them first. Once you know what type of fungus growth you are facing, you will be able to find a solution to treat it. Usually a fungal disease can be eradicated from your yard by changing cultural practices of your lawn care routine. 

Here are a few of the most common type of fungal infections homeowners might find growing in their yard:

1. Anthracnose 

Scot Nelson | Flickr | CC0 1.0

Causal Agent: Colletotrichum cereale (formerly Colletotrichum graminicola)

Turf Types Affected: The most susceptible turfgrasses are:

  • Annual bluegrass
  • Creeping bentgrass 

Symptoms: Anthracnose is most severe in early spring when temperatures are cool and in midsummer when the weather is warm and humid.

The disease appears as reddish-brown patches which fade to yellow and then tan to brown. Elongated, reddish-brown lesions with yellow halos develop on individual grass blades. 

Anthracnose can spread from the grass foliage to the crown and roots, resulting in basal rot (the crown is the base of the grass plant).

Spiny, black fruiting bodies called acervuli may appear on infected grass. 

Conditions for Disease: Grass under stress cultivates an environment for anthracnose to thrive in, and some of the factors that stress grass are:

  • High temperatures
  • Humid conditions
  • Wet leaves
  • Low or unbalanced fertility
  • Drought
  • Poor drainage
  • Compact soil
  • Insect damage
  • Thatch buildup
  • Low mowing heights 


  • Don’t overwater your yard. A drip irrigation system is the best way to prevent anthracnose from infecting your grass. Water in the early morning to avoid damp lawns.
  • Proper fertilization to provide your lawn with the right amount of nutrients it needs.
  • Remove excessive thatch.
  • Aerate compacted soil.
  • Avoid scalping the lawn.
  • When changes to your lawn routine don’t produce results, the Clemson Cooperative Extension recommends applying a fungicide containing propiconazole or azoxystrobin with propiconazole. Always apply chemicals according to the product label directions. 

2. Brown patch

circular brown spot on grass, with brown spots surrounding
Kris Lord | Flickr | CC BY 2.0

Causal Agent: Rhizoctonia solani

Turf Types Affected: Brown patch affects all warm- and cool-season turfgrasses, but it particularly affects:

  • Annual bluegrass
  • Creeping bentgrass
  • Kentucky bluegrass
  • Perennial ryegrass
  • Tall fescue

Symptoms: Brown patch typically forms irregular circles of thin, light brown grass. The patches range between a few inches to several feet in diameter. The turfgrass inside the circle’s center sometimes recovers, resulting in a donut-like shape.

Brown patch symptoms often resemble the signs of dog urine stains, drought, and grubs. Identify the disease by checking the grass in the early morning for white mycelium, a web-like substance that forms between the affected area’s leaf blades. 

When the disease is severe, it can spread rapidly across a large area without forming a circle.

Conditions for Disease: 

Several conditions create an attractive environment for this midsummer disease, including:

  • Poor aeration
  • Overwatering
  • Poor drainage
  • High nitrogen levels
  • Rainy weather
  • High humidity
  • Poor soil airflow
  • Night temperatures above 70 degrees
  • Daytime temperatures 80 degrees or above


  • Correct your watering regime.
  • Water in the early morning instead of the evening.
  • Remove grass clippings after you mow (otherwise, you’ll spread the disease).
  • Remove excessive thatch buildup.
  • Aerate your lawn every year.
  • Mow the lawn regularly.
  • Apply a fungicide in the affected area. Most fungicides list a curative and preventative application rate. Look for fungicides with Azoxystrobin, Pyraclostrobin with Triticonazole, or Fluoxastrobin.
  • Avoid nitrogen applications when the disease is active.

3. Dollar spot

Dollar spot on Bermudagrass
Dollar Spot
Scot Nelson | Flickr | Public domain

Causal Agent: Clarireedia jacksonii (formerly Sclerotinia homoeocarpa)

Turf Types Affected: All species of warm- and cool-season turfgrass are susceptible.

Symptoms: Dollar spot appears as tan spots 2 to 6 inches in diameter sprinkled across the lawn. Many of the spots are the size of a silver dollar (hence the name). Dollar spot is active in late spring through fall.

Affected grass blades have hourglass-shaped lesions with bleached centers and brown to purple borders. In the mornings, you might see cobweb-like mycelium coating the turf. 

If favorable conditions allow the disease to spread, the spots may merge to create large areas of dead grass. Dollar spot might damage the roots of your turfgrass, which will weaken the grass and cause discoloration. 

Conditions for Disease: Several conditions foster dollar spot growth in your yard, including:

  • Droughts
  • Humid weather
  • High temperatures
  • Dry soil
  • Low nitrogen levels
  • Overwatering
  • Low mowing


  • Apply adequate nitrogen fertilizer.
  • Remove thatch buildup.
  • Correct your irrigation regime. Remember to water deeply and less often to promote a robust root system. 
  • Mow grass regularly at the proper height. 
  • Aerate your lawn every year.
  • Apply a fungicide to help prevent further infection as you make corrective cultural measures. 

4. Fairy ring

Fairy ring
Fairy ring
Scot Nelson | Flickr | Public domain

Causal Agent: Many different species of fungi in the fungal group basidiomycetes cause fairy ring. 

Turf Types Affected: All grass types are susceptible to fairy ring disease. 

Symptoms: Fairy ring symptoms vary depending on the fungal species infecting the lawn, but a common symptom is dark green circular (or semi-circular) rings forming in the infested grass. 

The border of the circular rings may appear darker and faster-growing than normal-colored green turf. Older rings may have a band of dead grass with green grass in the middle. Grass within the circles may appear a normal-colored green, declining, or dead. 

Usually a ring of mushrooms may grow during moist or rainy conditions. 

The dark green turfgrass is caused by the fungus releasing nitrogen when it decomposes organic matter. The nitrogen gives that grass an unexpected nutrient boost. 

The brown-colored grass is caused by the fungus forming an almost waterproof layer in the soil that prevents water from reaching the turf’s root system. 

Conditions for Disease: There are several conditions that caus fairy ring to occur spring through early summer. 

  • Light-textured soil
  • Turf low in nitrogen
  • Low soil fertility
  • Drought
  • Excessive thatch


  • Use vericutting to reduce thatch.
  • Aerate the infested area.
  • Remove nearby tree stumps and tree roots to reduce the organic matter on which the disease feeds. 
  • Fertilize inside the ring to stimulate new growth.
  • Drench the brown-colored areas with a wetting agent (a chemical that helps water penetrate and spread) to enable water to access the roots. 
  • Fungicides for this disease are most effective when you use them as a preventative treatment.

5. Gray snow mold 

gray snow mold fungus on grass
Kris Lord | Flickr | CC BY 2.0

Causal Agent: Typhula incarnata

Turf Types Affected: Cool-season grasses are the type of grass primarily affected by gray snow mold

Symptoms: Symptoms appear in late winter or early spring as large snow covers melt away. 

White or tan crusted patches of dead, matted grass develop. Patches can range between a few inches to several feet in diameter. Gray fungal mycelium often appears on infected turf near receding snowbanks.

A notable symptom that can help you distinguish the disease from other snow molds is the presence of small, reddish-brown, rounded fungal structures (known as sclerotia) on the crowns and blades of infected turf.

Conditions for Disease: Growing conditions for gray snow mold are similar to pink snow mold. 

The disease develops underneath large snow covers that last a long time. The longer the snow covers remain, the more severe the infection. But unlike pink snow mold, which can exist without a snow cover, gray snow mold can only occur if snow covers it. 

Some things that make your lawn vulnerable to gray snow mold include:

  • Applying high amounts of nitrogen fertilizer
  • Recently planted grass seed that didn’t mature before winter
  • You didn’t cut the grass before winter


  • Remove piling snowdrifts.
  • Rake crusted, matted areas.
  • Avoid using high nitrogen fertilizer.
  • Affected turf will likely recover in spring with proper maintenance.

6. Leaf spot and melting-out 

Closeup of Leaf Spot on a Blade of Grass
Leaf Spot | Shutterstock

Causal Agent: Drechslera spp. and Bipolaris spp. (formerly Helminthosporium spp.)

Turf Types Affected: Many turfgrasses are susceptible to leaf spot and melting-out. The types of grass most severely affected are:

  • Bermudagrass
  • Kentucky bluegrass
  • Perennial ryegrass
  • Tall fescue

Symptoms: Disease symptoms can occur in spring, summer, and fall. 

Turf blades develop small brown spots after infection. As the disease progresses, the spots enlarge and develop tan centers with brown or purplish-red borders. The leaf tissue surrounding the spots begins to yellow. 

The melting-out phase, which is more detrimental to the turfgrass than the leaf-spotting phase, results in the dieback of the crown and roots. The grass tissues rot and turn black, and the turf begins to thin. 

Conditions for Disease: 

There are several possible conditions that can cultivate leaf spot and melting-out:

  • High nitrogen fertilizer
  • Thick thatch
  • Excess water
  • Wet weather
  • Mowing grass short 


  • Overseed lawns with a resistant cultivar.
  • Avoid high nitrogen fertilization.
  • Correct your watering regime so the lawn isn’t wet for long periods.
  • Water in the morning so the grass has plenty of time to dry out before nightfall. 
  • According to the PennState extension, spring and summer fungicide applications for turfgrass diseases performed in the early stages of leaf spot are the most effective. For good leaf spot control treatments, look for products that contain chemicals such as:
    • Azoxystrobin
    • Iprodione
    • Chlorothalonil
    • Fludioxonil
    • Mancozeb
    • Penthiopyrad
  • Applying fungicides in the melting-out phase is usually not effective.

7. Pink snow mold 

Pink snow mold
Pink snow mold
Bevegelsesmengde | Wikimedia Commons | CC BY-SA 3.0

Causal Agent: Microdochium nivale

Turf Types Affected: The turfgrasses most commonly affected by pink snow mold include:

  • Annual bluegrass
  • Bentgrass
  • Creeping bentgrass
  • Fescue
  • Perennial ryegrass

Symptoms: Pink snow mold occurs in late winter or early spring but can appear in late fall if conditions are right. Infected grass develops circular patches that typically range from 2 to 10 inches in diameter, although some patches may merge to create a large area of affected turf.

The patches often start small and will enlarge as cold weather conditions continue. Patches appear as gray, tan, or light pink matted grass with a white center. 

Conditions for Disease: Pink snow mold typically develops underneath deep snow cover that remains on the turf for a long time. The longer the snow cover stays on the grass, the greater the infection. Even without snow cover, pink snow mold can occur in cold and wet conditions.

Factors that make lawns especially susceptible to pink snow mold include:

  • Tall grass
  • High levels of nitrogen fertilizer
  • Poor soil drainage 
  • Excessive thatch
  • Grass seed that has not matured before winter
  • Temperatures that are 30 to 60 degrees Fahrenheit


  • Remove piling snowdrifts.
  • Rake diseased areas to break up matted grass.
  • Avoid applying high nitrogen fertilizer.
  • Remove excessive thatch.
  • Pink snow mold usually becomes less active when the turf dries and the air temperature rises.
  • Overseed the lawn with cultivars that are resistant to pink snow mold.
  • Use a fungicide such as azoxystrobin, iprodione, or propiconazole to treat the pink snow mold.

8. Powdery mildew 

Powdery mildew
Powdery mildew
Björn S | Wikimedia Commons | CC BY-SA 2.0

Causal Agent: Blumeria graminis

Turf Types Affected: Powdery mildew is a fungal disease that can afflict any grass, but it most commonly infects:

  • Annual bluegrass
  • Bentgrass
  • Fescues
  • Kentucky bluegrass

Symptoms: The first sign of powdery mildew appears as isolated, white spore masses developing on the blades of grass. The white or gray masses may eventually cover the whole blade, making the turf look as if it’s sprinkled in flour. 

If you look closely, you might see tiny black fruiting bodies within the white growth of powdery mildew.

Severely infected grass will turn yellow and possibly die. The reason for the dead turf is less likely powdery mildew and more likely weak turf succumbing to other stresses, such as drought or another disease.

Conditions for Diseases: Kentucky bluegrass growing in shade is one of the turfgrasses most susceptible to powdery mildew, but other conditions foster growing conditions for it as well, including:

  • Shaded areas
  • Poor air circulation
  • Humid conditions
  • Cool air temperatures


  • Increase sunlight in affected areas.
  • Remove or transplant plants that are inhibiting air circulation around the infected turf.
  • If you cannot modify the turf’s environment, Clemson Cooperative Extension recommends applying fungicides containing myclobutanil, propiconazole, or triadimefon.
  • Neem oil is an effective treatment for powdery mildew.
  • Home remedies made with baking soda or milk also can be used to stop powdery mildew. 

9. Red thread 

Kris Lord | Flickr | CC BY 2.0

Causal Agent: Laetisaria fuciformis   

Turf Types Affected: Red thread typically infects:

  • Bentgrass
  • Fine fescue
  • Kentucky bluegrass
  • Perennial ryegrass

Symptoms: Although red thread may be playfully nicknamed “pink patch,” you definitely don’t want to deal with this fungus frolicking in your yard. This fungal disease occurs in spring and fall but also can emerge in summer when rain persists. 

Red thread can be recognized by irregular patches of pink spots that look a bit like cotton or thread strands developing in the yard. Sometimes the patches might appear as a reddish-brown or orange fungal growth. 

In the late stages of the disease, reddish threads of fungal mycelium grow at the tips of the affected blades. Red thread affects the turf’s leaf, stem, and sheath, but severe infections can kill the whole plant. When the turf dies, the affected areas turn light pink or tan. 

Conditions for Disease: 

Certain conditions make your yard more susceptible to red thread, including:

  • Inadequate nitrogen fertilizer
  • Excessive moisture and overwatering
  • Humid weather
  • Temperatures are 60 to 75 degrees Fahrenheit


  • Apply adequate levels of nitrogen fertilizer.
  • Practice good watering techniques so that your lawn doesn’t remain wet for too long and you don’t overwater the lawn. 
  • Fungicides are usually not necessary to treat red thread. If the infestation is severe and a fungicide is warranted, you’ll need a licensed applicator to apply the product for you.  

10. Rust 

Rust lawn disease
NC State Cooperative Extension

Causal Agent: Puccinia spp., Uromyces spp.

Turf Types Affected: The most severely affected by rust are:

  • Kentucky bluegrass
  • Perennial ryegrass
  • Tall fescue
  • Zoysiagrass

Symptoms: The most common turfgrass rust diseases are stem rust (Puccinia graminis), stripe rust (Puccinia striiformis), crown rust (Puccinia coronata) and leaf rust (Uromyces spp.). An early sign of rust is yellow speckles appearing on the blade and stem. 

As the yellow areas grow larger and spread, the leaf eventually ruptures and releases yellowish-orange to reddish-brown spores. Orange powder will collect on your shoes and fingers when you walk on or rub the infected turf. 

Conditions for Disease: Rust occurs in early spring through mid-summer. The diseases thrives under certain conditions:

  • Moist areas
  • Low sunlight
  • Low nitrogen levels 


  • Apply adequate levels of nitrogen.
  • Reduce shade by trimming trees and bushes.
  • Improve air circulation by aerating your soil.
  • Correct irrigation practices.
  • Fungicides are not always necessary, but severe rust infections may benefit from chemical treatment. 
  • Mow regularly.

11. Summer patch 

Causal Agent: Magnaporthe poae

Turf Types Affected: The grasses most affected by summer patch are:

  • Annual bluegrass
  • Fine fescue
  • Kentucky bluegrass

Symptoms: Summer patch symptoms look like crescent-shaped or circular patches with slow-growing, thin, wilted grass. Patches range from a few inches to 3 feet in diameter and can merge to create a sizable infected area. Many times healthy grass grows in the patch’s center. 

Summer patch bears a resemblance to other turf diseases and turf injuries associated with drought and heat stress. For successful identification of summer patch, a qualified diagnostician must look at the affected turf with a microscope. 

Conditions for Disease: 

Summer patch is root disease. Improper cultural practices promoting shallow root systems will make your lawn susceptible to the fungus. 

Favorable disease conditions include:

  • Heat and drought stress
  • Low mowing heights
  • Frequent and light irrigation
  • Soil compaction
  • Excessive thatch
  • Unbalanced fertility 


  • Aerate compacted soil.
  • Mow your grass at the highest recommended mowing height.
  • Develop a balanced fertilizer regime.
  • Avoid fertilization practices that promote top growth at the expense of root development. 
  • Follow proper irrigation practices. Water the lawn less often and for long periods and avoid overwatering. 
  • Water in the early morning instead of the evening. 
  • Reduce thatch buildup.
  • Don’t scalp your grass.
  • You can resort to fungicides for summer patch control, but they are more effective as a preventative measure. 

What causes fungus to grow in my lawn?

A disease-causing pathogen needs two things for it to flourish: a host and the right environment. 

Your grass type will play a significant role in whether a fungal disease can prosper, since some turfgrasses make better hosts for certain diseases than others. 

Weak lawns that are poorly maintained provide an ideal environment for fungal disease. So if you’ve been slacking on your lawn care chores, like mowing, dethatching, and fertilizing, then you’re sending an open invitation to grass diseases. Yikes

Some of the most common causes of fungus in your lawn are:

How to prevent grass fungus in the lawn

In general, the best treatment is to improve your lawn care practices. Putting specific cultural routines in place and enhancing lawn maintenance makes the environment less hospitable for the fungus. 

A fungicide may help control severe infestations, but it’s not always the best treatment method. Fungicides typically prove most effective when you apply them as a preventative measure. 

For natural fungicide solutions that are safer for the environment, try using treatments such as:

  • Neem oil: Combine 4 tablespoons of neem oil with 5 liters of water. Spray onto the fungus infection every few days until the infection is gone. 
  • Water and baking soda: Mix 1 tablespoon of baking soda and 5 liters of water. The solution should be applied to your lawn every 3 days until the fungus is gone.
  • Compost tea: Mix 4 cups of compost tea in a gallon of water. Treat your lawn with the mixture in the early morning every 2-4 weeks.

As much as you want to skip removing autumn leaves or aerating the lawn this year, you might want to think twice before you ignore the lawn. 

Here are 15 lawn care treatments homeowners can do to help nourish a vigorous lawn that’s resistant to disease: 

  1. Remove leaves and other debris from the lawn. Otherwise, diseases overwinter in debris and take hold of your grass in spring.  
  2. Mow the grass regularly. Letting your grass grow too tall will create a hospitable environment for disease. Be careful not to cut the grass too short. 
  3. Leave behind grass clippings. Grass clippings act as mulch by locking in moisture and adding healthy nutrients to the soil. Keep in mind that if a disease is already infecting your lawn, you’ll want to remove grass clippings so that the fungus doesn’t spread.
  4. Perform proper irrigation practices. Watering for long periods less often is healthier for your lawn than watering for frequent, short periods. To help keep out fungus, the best time of day to water your turf is in the early morning before 10 a.m. 
  5. Invest in a sprinkler system. Most lawns need 1 to 1½ inches of water a week during the summer. A well-watered lawn is important for keeping fungal diseases away from your yard. An automatic sprinkler system will turn on without you ever having to lift a finger. 
  6. Grow a disease-resistant type of grass that’s suitable for your lawn. Talk to a lawn care professional about the best turf for your lawn and which cultivars are most resistant to the common fungal diseases where you live.
  7. Test your soil and add amendments. You can’t have healthy turf if the soil it grows in is poor. Test your soil’s health so you can determine the best way to improve it. 
  8. Fertilize your grass. Just like you need food to grow, so does your grass.
  9. Aerate the soil. Aeration relieves compacted soil by creating small holes in the ground. The holes allow water, oxygen, and nutrients to reach the roots. 
  10. Remove thatch. Thatch is the buildup of dead organic matter that accumulates between the soil layer and turf. Fungus loves to live in thatch. Remove thatch when the layer reaches ½ inch or more.
  11. Overseed the lawn. Help prevent your yard from thinning by overseeding the lawn once a year. It’s a good idea to overseed with a disease-resistant cultivar. 
  12. Remove existing weeds. Overgrown weeds compete with your turf for space, light, moisture, and nutrients. A severe weed invasion can weaken your turf and make it vulnerable to pests and disease.  
  13. Apply pre-emergent herbicide. You can help prevent weeds from popping up by applying a pre-emergent herbicide
  14. Control grubs and other pests. Lawn grubs are a big pest that is often found in yards. They weaken your turf by feeding on the lawn’s root system. 
  15. Spread a ½-inch layer of compost across the lawn. Backyard compost is a nutritious soil amendment. You can spread the compost with a rake or brew a compost tea. 

Chemical control: If your lawn has a history of fungal disease, then applying chemical fungicides as a preventative measure can prove effective. 

FAQ about grass fungus

Will lawn fungus go away on its own?

An infestation’s severity may weaken when the temperature or weather changes, but a fungal disease won’t leave your lawn alone without the proper treatment. If left untreated, the infection may spread or kill your turf.

Can I treat lawn fungus with a fungicide?

Depending on the disease, a licensed professional can treat a fungal disease if the infestation is severe. Fungicides are more effective as fungus control when used as a preventative treatment. The best curative treatment for fungus is implementing good lawn care practices. 

What if I can’t identify the fungus?

Some lawn diseases are challenging to identify. In many cases, their symptoms may mimic turf injuries (such as drought or stress) or the symptoms of other lawn diseases. To determine the best treatment method for your lawn, you must know the disease you’re up against.

If you need assistance with identification, contact a diagnostics lab or a turfgrass pathology lab. These labs specialize in the accurate diagnosis of turfgrass disease and are typically located at state universities. 

Consider all your treatment options

From mowing to aeration, treating fungal disease is hard work. Not only do you need to fertilize and irrigate the lawn to treat a disease, but you also need to perform proper maintenance year-round to ensure an infestation doesn’t reoccur. Take the load off your shoulders and hire a local lawn care professional. Hand the to-do list over to a pro so you can focus on the people, goals, and hobbies that matter to you most. Don’t let fungus, a spore-producing organism that’s anything but fun, steal your time and energy. 

Main Photo Credit: Andrew Skudder | Flickr | CC BY-SA 2.0

Jane Purnell

Jane Purnell is an artist, writer, and nature lover. She enjoys teaching readers about the importance of eco-friendly lawn care, integrated pest management, biodiversity, and sustainable landscaping.