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Plant Diseases in Lawns

Many species
Updated Sep 01, 2022

Make a Positive Identification

Plant Diseases Can Damage Lawns, But Damage Could Be Caused by Other Factors

  • Diseases are not the most common cause of lawn damage.
  • Poor lawn care is the most likely cause of unhealthy or dying lawns.
  • Damage from insects and dog urine looks similar to disease damage.

Inspect Your Lawn for Plant Diseases and Their Damage

  • Look for direct signs of diseases and their damage as described in this article.
  • Disease damage usually begins in small, scattered patches. These may merge into larger damaged areas.
  • The majority of lawn diseases are caused by fungal pathogens.
  • Lawn diseases affect different species of grasses differently.
  • Lawn diseases also vary by region in the Pacific Northwest (west and east of the Cascade Range).

Grow a Healthy Lawn to Minimize Damage from Plant Diseases

You can minimize disease damage to your lawn by growing healthy, robust grasses. See Prevent Lawn Problems to learn more.

Fungal Diseases in Lawns
Species: Anthracnose
Anthracnose on bentgrass
Anthracnose basal stem rot phase
Photo credits

Barb Corwin, Turfgrass Diagnostics, (cropped)


Clemson University - USDA Cooperative Extension Slide Series, (cropped)

Anthracnose (Colletotrichum cereale)

  • Anthracnose occurs west of the Cascade Range.
  • It affects lawns with annual bluegrass. It also affects red fescue and bentgrass.
  • Anthracnose develops on grasses under stress, especially when soil is dry and leaves are wet.
  • Warm, humid summer weather favors its spread.

How to Identify Anthracnose

  • During the summer (leaf blight phase), yellow-to-brown lesions appear on older leaves and sheaths. Later, black fruiting bodies appear. Irregular brown-to-yellow-tan to gray areas (right photo) then appear on the lawn. They range from a few inches to several feet in diameter.
  • During fall and winter (basal stem rot phase, left photo), the disease rots the base of grass plants. Older leaves turn yellow at the tips, then turn bright orange-red. Damaged areas are less than an inch in diameter.
Species: Dollar Spot
Dollar spot on lawn
Dollar spot disease symptoms on grass leaf blades
Photo credits

Mary Ann Hansen, Virginia Polytechnic Institute and State University, (cropped)


Florida Division of Plant Industry , Florida Department of Agriculture and Consumer Services, (cropped)

Dollar Spot (Clarireedia homoeocarpa)

  • Dollar spot occurs east of the Cascade Range.
  • This is a common disease on bentgrass lawn species when fertility is low.
  • Dollar spot occurs in fall when the days are warm and nights are cool; also when leaves are wet for a long time and soil is dry.

How to Identify Dollar Spot

  • It forms small, roughly circular, bleached patches from a few inches to 6 inches or more in diameter (left photo).
  • Spots may merge into large, irregular dead areas.
  • Light-yellow to tan lesions with reddish-brown borders extend across the leaf blade (right photo).
  • Leaf tips may die back. They may wilt and turn tan to brown.
Species: Leaf Spot
Turf showing signs of infection with Drechslera leaf spot
Leaf spot symptoms on leaf blades
Photo credits

William M. Brown Jr., (cropped)


B. Bockus, (cropped)

Leaf Spot (Drechslera spp.)

  • Leaf spot occurs west of the Cascade Range.
  • It is common on Kentucky bluegrass lawns.
  • Leaf spot also affects under- or over-fertilized perennial ryegrass lawns.
  • It occurs in cooler months.
  • Symptoms are worse when grasses are mowed short.

How to Identify Leaf Spot

  • Tiny, water-soaked lesions turn purple with straw-colored centers (right photo).
  • Lesions may girdle the leaves (left photo).
  • The lawn turns brown and thin. It looks drought-stressed.
Species: Microdochium Patch
Microdochium patch on lawn
Microdochium patch on lawn
Photo credits

"Microdochium patch" by John Kaminski is marked with CC BY-NC-ND 2.0 (cropped).


"Microdochium patch" by John Kaminski is marked with CC BY-NC-ND 2.0 (cropped).

Microdochium Patch / Pink Snow Mold / Fusarium Patch (Monographella nivalis)

  • Michrodochium patch occurs west of the Cascade Range.
  • It affects annual bluegrass, tall fescue, and bentgrass.
  • Fine fescues, bluegrass, and ryegrass may also be infected.
  • Michrodochium patch develops in cold weather (under 60 degrees Farenheit) on over-fertilized lawns.
  • Damage occurs in early spring.

How to Identify Microdochium Patch

  • The reddish-brown circular patches are 1–2 inches in diameter (right photo).
  • The center is generally tan. It may contain uninjured grass.
  • White or pinkish fungal growth may be visible at the leading edge of the patches (left photo).
  • It may grow beneath the snow or as snow melts.

Tips to Get Rid of Microdochium Patch

  • Rake and remove tree leaves from the lawn before winter.
  • Continue to cut grass until the fall. Mow with a mulching mower or remove clippings.
Species: Necrotic Ringspot
Necrotic ringspot in Kentucky bluegrass lawn
Kentucky bluegrass with necrotic ringspot
Photo credits

Howard F. Schwartz, Colorado State University, (cropped)


Melodie Putnam (2010), Oregon State University (cropped)

Necrotic Ringspot (Ophiosphaerella korrae)

  • Necrotic ringspot occurs east of the Cascade Range.
  • It affects Kentucky bluegrass and fine fescue when thatch is excessive.
  • Infection occurs in the fall. Symptoms become visible in summer.
  • It usually occurs on 2- to 5-year-old lawns grown from sod.

How to Identify Necrotic Ringspot

  • It forms circular, yellowed areas 2 to 5 inches wide, with reddish-brown margins (left photo). Patches may expand to several feet across.
  • Infected patches lift easily from the soil.
  • Dead rings may have green grass in the center.
  • Roots and rhizomes are blackened as shown in the photo (right).

Tips to Get Rid of Necrotic Ringspot

  • Don’t apply excessive organic matter such as compost.
  • Annual core aeration and dethatching are recommended for susceptible grass types.
  • Avoid over-watering in the fall.
  • If symptoms are seen in summer, water lightly and frequently. This method will help grass grow with a damaged root system.
Species: Net Blotch
Microdochium patch on lawn
Microdochium patch on lawn
Photo credits

OSU Turfgrass Management Program


OSU Turfgrass Management Program

Net Blotch (Pyrenophora dictyoides)

  • Net blotch occurs west of the Cascade Range.
  • It affects tall and fine fescues, and perennial and annual ryegrasses.
  • It occurs in winter when fertility is low.
  • Symptoms are most severe on young grass in wet, shady areas.

How to Identify Net Blotch

  • When net blotch affects fine fescue, you’ll see small, reddish-brown spots, dieback from the tip, and small brown patches of dead foliage in turf (left photo).
  • In tall fescue and perennial ryegrass, net blotch creates short brown streaks in a net-like pattern on leaves (right photo).
  • Heavily infected stands turn yellow and then brown.
Species: Red Thread
Red thread in lawn
Closeup of red fungal structure
Photo credits

Oregon State University Plant Clinic (cropped)


Bruce Watt, University of Maine, (cropped)

Red Thread (Laetisaria fuciformis)

  • Red thread occurs west of the Cascade Range.
  • Red thread is the most common disease on perennial ryegrass. It also occurs on red and Chewings fescue. The symptoms are less severe on bentgrass. Hard fescue is resistant.
  • Symptoms are most severe on lawns low in vigor and when nitrogen fertilizer is limited.
  • The disease is cosmetic. It rarely kills grasses.

How to Identify Red Thread

  • It forms circular or irregular yellow patches, 2–24 inches across (left photo). Bleached or tan grass tips are mixed with healthy grass.
  • Fine pinkish to red fungal threads grow from leaf tips.
  • Red thread grows small pink or red antler-like structures on leaf blades (right photo).
Species: Rust
Rust on lawn
Rust on grass leaf blade
Photo credits

"Rust" by John Kaminski is marked with CC BY-NC-ND 2.0.


"Rust" by John Kaminski is marked with CC BY-NC-ND 2.0.

Rust (Puccinia spp. and Uromyces spp.)

  • Rust is common east of the Cascade Range.
  • Rust is common on Kentucky bluegrass. It also affects ryegrasses and fine fescues.
  • It occurs in the fall when a lawn is under-fertilized.
  • Rust is most severe when grasses are stressed.

How to Identify Rust

  • Affected turf areas may be colored reddish, brown, or yellow (right photo).
  • Yellow specks form on leaf blades. They turn into yellow, orange, orange-brown, or red pustules (left photo).
  • Infection may also occur on stems and leaf sheaths.
  • Severe rust infections can kill leaf blades.
Species: Take-all Patch
Large take-all patch on lawn
Take-all patch symptoms on grass stems and leaves
Photo credits

William M. Brown Jr.,


Holly Thornton, University of Georgia,

Take-all Patch (Gaeumannomyces graminis var. graminis)

  • Take-all patch occurs east of the Cascade Range.
  • It is common on bentgrass species.
  • It occurs when fertility is low.
  • Take-all patch is most severe on young plantings in sandy soils.
  • It spreads in wet weather.

How to Identify Take-all Patch

  • Small circular patches appear in late spring.
  • Patches are reddish brown at first, then brown to gray.
  • They may enlarge to 3 feet or more in diameter over a period of years (left photo).
  • Both shoots and roots are damaged (photo right).
  • Weeds and annual bluegrass may grow in the center of the dead circle.
Species: Gray Snow Mold
Gray snow mold patches with snow in the background
Closeup of gray snow mold on grass

Typhula Blight (Gray Snow Mold) (Typhula spp.)

  • Typhula blight occurs east of the Cascade Range.
  • It develops when grass is covered by snow for more than 60–90 days.
  • It occurs on lawns with heavy thatch layer.
  • Damage is worse under snow on unfrozen ground.

How to Identify Typhula Blight

  • Small circular, yellow to yellow-brown spots appear after snow is gone (left photo).
  • Spots may reach 12 inches if snow cover lasts a long time.
  • A fluffy white-to-gray mass of fungal growth may form a halo at the margin (right photo).
  • It affects grass leaves and does not kill the base of grass plants.
  • Grasses are able to grow back to a normal appearance.

Tips to Get Rid of Typhula Blight

  • Rake and remove tree leaves from the lawn before snowfall.
  • Continue to cut grass until snowfall. Remove clippings.
  • Avoid compaction of snow. Remove snow from disease-prone areas in the spring, if needed.
Non-Fungal Diseases in Lawns
Species: Algae
Algae in lawn

Jay Pscheidt (2017), Oregon State University

Algae (Symploca spp. and Oscillatoria spp.)

  • Algae occurs in coastal regions of the Pacific Northwest.
  • It grows where growing conditions are poor for lawns.
  • Shade, poor drainage, poor air movement, and compacted soils are factors that favor algae growth.

How to Identify Algae

  • Greenish to black scum occurs on the soil surface and plant crowns. It may resemble an oil spot.
  • The algal scum dries to a black, water-repellent crust.
Species: Root-Knot Nematodes
Small galls on roots of grass

Jonathan D. Eisenback, Virginia Polytechnic Institute and State University,

Root-Knot Nematodes (Meloidogyne naasi)

  • Nematodes suck sap from the root.
  • They leave wounds through which parasitic fungi enter.

How to Identify Nematodes

  • Infected grasses lack vigor and may be discolored, stunted, or thin.
  • Grasses may have darkened, rotted roots, and yellowish areas as shown in the photo.
  • Grasses may wilt and die in irregular patches.
  • Nematode-infected grasses don’t respond to fertilizer, fungicides, or irrigation.

Tip to Get Rid of Root-Knot Nematodes

  • Reduce plant stress from soil compaction and low pH. Improve lawn-growing conditions.
Species: Slime Molds
Orange slime mold on grass

"Slime mold" by Oregon State University is marked with CC BY-SA 2.0 (cropped).

Slime Molds

  • Slime molds are non-parasitic fungi that use grass blades as a support.
  • They often appear suddenly.
  • Slime molds appear in wet weather and when there is heavy leaf litter in the lawn.

How to Identify Slime Molds

  • Slime molds are globular structures that form on grass blades.
  • Slime molds vary in color from orange (shown in photo) to white/gray to purple/brown.
  • Their reproductive structures break and release many spores.
  • Slime molds don’t harm grasses in lawns.

What to Do About Slime Molds

  • Slime molds will disappear if left alone.
  • Remove small slime molds by mowing, raking, or washing.
  • Remove larger masses with a shovel or a strong stream of water.
Species: Yellow Spot
Yellow spot on lawn

Brian McDonald (2012), Oregon State University

Yellow Spot (Blue-green algae) Oscillatoria spp. or Phormidium spp.)

  • Yellow spot occurs on annual bluegrass and low-mowed bermudagrass.
  • Drought stress, low fertility, use of organic fertilizers, low mowing, and shade are factors that favor the growth of yellow spot.

How to Identify Yellow Spot

  • Small yellow spots can expand to cover large areas. Growth appears normal, aside from yellow color (shown in the photo).
  • Severe symptoms can result in large declining areas of lawn.
  • Algal scum occurs on the surface of the thatch.
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Plant Diseases in Lawns Benefits

  • Plant diseases that affect lawns don’t have any benefit for people or the environment.

Plant Diseases in Lawns Risks

  • If unchecked, plant diseases in your lawn can spoil its appearance.
  • Some diseases can cause damage to the health of grasses in your lawn.
Risk Card
Does it cause harm?
Adults & Children
Action Optional

Take Action?

Plant diseases are not a common cause of damage in your lawn. People have different tolerance levels for harm.

Do I need to take action?

  • For most lawns, you can tolerate plant diseases. The damage is often minor. Focus on growing healthy grasses. See Prevent Lawn Problems.
  • For high-maintenance lawns that have sustained a lot of damage, consider control options only after you’ve confirmed the identity of a lawn-disease pathogen.

What if I do nothing?
Damage from diseases in lawns is often tolerable.


Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon  and other states  can suggest other methods.

Solutions for Diseases in Lawns
  • Prevention is the best strategy for controlling lawn diseases. Maintain a strong and healthy lawn. See Prevent Lawn Problems.
  • Fungicides (plant pathogen killers) must be applied before diseases appear to work. They will not cure a lawn that is already diseased.
  • Fungicide treatments applied by homeowners tend to be ineffective. Most homeowners don’t have the right tools and experience to treat lawns successfully with fungicides.
  • If you determine you have lawn disease problems, consider hiring a professional turf care specialist to help. Professionals have the right skill and experience to treat plant diseases in your lawn effectively.

Jump To

Method Does it work? Is it safe? Recommendation
Maintain A Healthy Lawn
Very effective
Low risk
Fungicides for Lawns from Stores
Somewhat effective
Moderate risk
Use if Necessary
If Using Fungicides, Protect Yourself & Reduce Risks
Prevent Diseases in Lawns

Maintain A Healthy Lawn

Non-Chemical Method

OSU Turfgrass Management Program

Maintain A Healthy Lawn

You can minimize disease damage to your lawn by growing healthy, robust grasses.

Does it work?
Very effective

Use preventive measures for best results.

How much effort?
High effort

Maintaining a healthy lawn requires planning and ongoing effort.

What's the risk?
Low risk
Possible risk of exposure or harm from chemicals

The best defense against disease problems in your lawn is to maintain a healthy lawn.

Lawn fertilizer package

Weston Miller, Oregon State University

  • The photo shows a package of lawn fertilizer (turf builder). Text on the label states “PROTECT AGAINST FUTURE PROBLEMS.”
  • Fertilizing your lawn is a key step to growing healthy grasses in your lawn.
  • Healthy grasses resist disease problems.

Understand Conditions that Favor Diseases in Lawns

For plant diseases to grow, three factors must align:

  • Presence of the disease-causing pathogen
  • Plant material that is susceptible to the specific pathogen
  • Environmental conditions that favor the growth of plant pathogens

Different types of grasses used in lawns are susceptible to different pathogens at different times of the year.


Fungicides for Lawns from Stores

Chemical Method: Use with caution

Weston Miller, Oregon State University

Fungicides for Lawns from Stores

Use if Necessary
  • Numerous fungicides indicated for lawns are available at garden centers. Consider using fungicides only after if you’ve identified a specific disease that is causing damage and after you’ve tried preventive methods.
  • Fungicides have to be applied before the disease symptoms develop to be effective.


Does it work?
Somewhat effective
  • Fungicides work to stop fungal growth if applied before symptoms develop. They don’t effectively get rid of diseases on your lawn after the symptoms develop.
  • Fungal pathogens can develop resistance if the same fungicide ingredient is used repeatedly. The fungicide may become less effective over time.
  • Use preventive measures for best results.
How much effort?
Moderate effort

This approach requires significant research and understanding of lawn diseases and fungicides. Products have to be applied at the right time to intervene against the disease problem.

What's the risk?
Moderate risk

Fungicides come with real risks. ALWAYS read the entire label front to back. Use a magnifying glass.

Possible risk of exposure or harm from chemicals
Using fungicides includes some amount of risk. The lowest risk comes without using fungicides.

You may be exposed to a fungicide if you:

  • Get it on your skin
  • Breathe it in
  • Eat or smoke afterward without washing hands
  • Touch or eat plants that are wet with spray (you, pets, or children)
  • Bring it inside on your shoes or clothes

Follow directions closely to reduce risk.

If you decide to use a fungicide to treat lawn disease(s) yourself, choose products that highlight use for lawn areas

White boxes highlighting lawn diseases on fungicide products

Weston Miller, Oregon State University

The white box on this example fungicide product states “CURES & PREVENTS Common Lawn Diseases.” The text in the other white box states that the product controls brown patch, dollar spot, rusts, summer patch, anthracnose, and other listed diseases.

Application Tips

  • Read and understand the DIRECTIONS FOR USE section of the product label before using.
  • Once a fungal disease establishes on a lawn, fungicides don’t work to eliminate it.
  • If chemical treatment is needed, begin fungicide applications before symptoms develop.
  • Don’t repeatedly use a single fungicide. This may enable pathogens to develop resistance.
  • Alternate fungicides from different groups with different modes of action. Switching the type of ingredient used reduces the build-up of resistant lawn diseases.

Recommended: Hire a Professional

  • If you determine that a fungicide could help your situation, we recommend hiring a licensed landscape company with an Integrated Pest Management specialist on staff.
  • They have the skills to diagnose the problem and determine a course of action. They know how and when to apply fungicides to get rid of lawn diseases effectively.

If Using Fungicides, Protect Yourself & Reduce Risks

Chemical Method: Use with Caution
Family and pet on lawn

Fly View Productions, iStock

Why is It Important to Read Fungicide Labels?

  • They have detailed information on how to use the product correctly and legally.
  • They contain information on potential hazards of the product.
  • They provide instructions you should follow for poisonings and spills.
  • Following label instructions helps you to minimize the risks and maximize the benefits.

Key Fungicide Safety Tips

  • Read the entire label front to back.
  • Follow the instructions.
  • Review the instructions even for brands you know.
  • Only apply the product where the label says it may be applied.
  • Be precise in your application. More is not better.

The Label is the Law

ALWAYS read the label before using fungicide products. The label is a legal document that provides information on how to safely use the fungicide. This helps avoid harm to human health and the environment. Using a fungicide in off-label ways is illegal. It can result in legal enforcement actions.

READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.

  • Labels are different for every product and they often change over time.
  • Use a magnifying glass.
  • Pay attention to CAUTION, WARNING, and DANGER statements.
  • Pay attention to the PRECAUTIONARY STATEMENTS.
  • The law states you must read and follow fungicide instructions.

Protect Yourself
Eye, skin, & lung irritants

  • Wear gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
  • Avoid contact with eyes, skin, or clothing.
  • Wash hands after mixing or applying, and before eating or smoking.
  • Never spray directly overhead. Pay attention to wind conditions.

Protect Children & Pets
Children and pets are at risk if they eat or touch the plant before fungicides dry.

  • Keep them away during and after applying fungicides (read label for how long).
  • Remove toys and pet dishes from yard before applying.
  • Don’t track fungicide products into home on shoes or clothes.

Protect Pollinators

  • Apply early morning or evening when bees are less active.
  • Avoid spraying flowering plants, if possible.
  • Don’t spray on bees or insects.

Storage & Disposal

  • Store out of the reach of children and pets.
  • Store in a cool and dry place.
  • Never pour down any drain.
  • If you mix too much, apply it rather than storing it.
  • Don’t put fungicide containers in the trash unless instructed by the label.
  • Take unused fungicides to a hazardous waste facility.

Call  1-800-CLEANUP (1-800-253-2687) to find out where to dispose of pesticides.

For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call  503-234-3000, email   or visit Metro’s website  

More about:

About Using Pesticides on School Grounds in Oregon

If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management  (Oregon Department of Agriculture).


The National Pesticide Information Center (NPIC)  can answer questions about pest control chemicals.
 1-800-858-7378 or  

Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.

Your local Extension Specialist in Oregon  and other states  can suggest other methods.


Prevent Diseases in Lawns

Lush green lawn

Yarygin, iStock

Grow a Healthy Lawn
  • Maintain the right growing conditions needed for strong, healthy turfgrasses. Healthy lawns resist disease problems.
  • Lawns change over time. After you’ve sown lawn seed or laid sod, a mixture of desired turfgrasses and broadleaf weeds, grassy weeds, and moss will evolve.
  • Soil drainage, soil fertility, sunlight, water stress, and how the lawn is cared for and used will all influence how your lawn looks over time.
  • Set realistic expectations for your lawn. Match the lawn standards you want to maintain with the right maintenance schedule.
  • If the quality of your lawn doesn’t match your standards, consider a lawn renovation.
  • For more information, see Prevent Lawn Problems.

Content provided by editor Weston Miller and writer Signe Danler. Pesticide safety information edited by Kaci Buhl.

 Reviewed by OSU Department of Horticulture.

Photo of Weston Miller

Weston Miller

Project Founder and Content Writer

Weston Miller served as Community and Urban Horticulture faculty for Oregon State University Extension Service for Clackamas, Multnomah, and Washington Counties. Weston is an author for content for this website. He developed funding partnerships with Portland area agencies to initiate and build out the Solve Pest Problems website focused on this goals:

Signe Danler

Signe Danler (Editor/Writer)

Signe supports the OSU Extension Master Gardener Program by producing educational content for online Master Gardener training courses, and teaching and managing the OSU-Extension online Home Horticulture courses. She also designs residential and commercial landscapes, specializing in regenerative gardening and landscaping practices.

Photo of Kaci Buhl

Kaci Buhl

At the state level, I lead the Pesticide Safety Education Program (PSEP). The program hosts live recertification events around the state, serving over 1,000 licensed pesticide applicators each year. We also produce web-based training modules and license-preparation study manuals. Special training for unlicensed pesticide applicators is also available through a grant from the USDA Specialty Crop Block Grant Program. The PSEP at OSU works closely with the Oregon Department of Agriculture's Pesticides Division.