Brown patches in a lawn can be caused by fungal disease, improper watering, poor drainage, insects, pet urine, mowing stress or seasonal dormancy. The size, shape, location and timing of the damaged areas can help you determine what is affecting your grass.
In the Southeast, warm temperatures, frequent rainfall and high humidity create favorable conditions for several lawn diseases. Large patch, brown patch and dollar spot are among the most common fungal problems, but not every brown area is caused by fungus.
Before applying fertilizer, fungicide or additional water, take a closer look at the symptoms.
What Causes Brown Patches in Grass?
Some of the most common causes include:
- Large patch in warm-season grasses
- Brown patch in cool-season grasses
- Dollar spot
- Too much or too little water
- Poor soil drainage
- Dull mower blades or mowing too low
- Excessive fertilizer
- Pet urine
- Grubs or other insects
- Compacted soil or heavy foot traffic
- Chemical spills or herbicide damage
- Normal warm-season dormancy
The correct treatment depends on the cause. Applying more water or fertilizer without identifying the problem can sometimes make the damage worse.
How to Identify the Cause of Brown Patches
Start by looking at the pattern, size and location of the affected grass.
| What you see | Possible cause |
|---|---|
| Large circular or irregular patches | Large patch or brown patch |
| Small, straw-colored spots that merge together | Dollar spot |
| Damage near sprinkler gaps or hot pavement | Drought or uneven irrigation |
| Bright green growth surrounding a brown center | Pet urine |
| Grass that lifts easily from the soil | Grubs or root damage |
| Brown grass after cold weather | Seasonal dormancy or cold injury |
| Tire-shaped or footpath-shaped damage | Compaction or traffic |
| Ragged, shredded leaf tips | Dull mower blades |
| Consistently wet, thinning grass | Overwatering or poor drainage |
Because several lawn problems can look similar, photographs alone may not provide a definitive diagnosis. A lawn care professional or local Cooperative Extension office may need to examine the grass, roots and surrounding soil.
Large Patch in Warm-Season Grass
Large patch is a fungal disease caused by species of Rhizoctonia. It primarily affects warm-season grasses as their growth slows in the fall or resumes in the spring.
Zoysia and centipede are particularly susceptible. Bermuda may also experience disease-related patching, although its symptoms can be caused by several other environmental and maintenance issues.
What Does Large Patch Look Like?
Large patch usually appears as:
- Circular or irregular patches several feet across
- Yellow, tan or brown grass
- Orange or reddish grass around an actively expanding edge
- Thinning grass that remains attached at the roots
- Patches that return or expand in the same locations
Individual patches may begin relatively small and grow to 20 feet or more under favorable conditions.
Large patch commonly becomes active during cool, wet periods in fall and spring. Symptoms may appear as warm-season grass approaches dormancy and can become visible again during spring green-up.
Brown Patch in Fescue and Other Cool-Season Grasses
Brown patch is another disease associated with Rhizoctonia, but the term is generally used when the disease affects cool-season grasses such as tall fescue.
Unlike large patch, which is most active during cooler transitional weather, brown patch in fescue is usually associated with warm, humid conditions. It can become especially noticeable during periods of hot weather, frequent rainfall, heavy dew and nighttime temperatures above approximately 65°F.
What Does Brown Patch Look Like in Fescue?
Symptoms may include:
- Circular patches ranging from several inches to several feet across
- Tan or brown grass surrounded by darker green grass
- Irregular tan lesions on individual leaves
- A dark or gray “smoke ring” around an active patch early in the morning
- Green grass attempting to grow within damaged areas
The roots and crowns may remain alive even when the leaf blades are damaged. If growing conditions improve, the grass may recover without needing to be replaced.
Dollar Spot
Dollar spot can affect both warm- and cool-season grasses. It initially produces small, sunken areas of tan or straw-colored grass that may be approximately the size of a silver dollar.
When the disease becomes severe, individual spots can merge and create much larger areas of discoloration.
Signs of Dollar Spot
Look for:
- Small, circular spots approximately one to several inches wide
- White, tan or straw-colored grass
- Hourglass-shaped or banded lesions on individual blades
- Fine, white, cobweb-like fungal growth during cool, damp mornings
- Multiple spots merging into irregular patches
Dollar spot is often associated with prolonged leaf moisture, low nitrogen levels, drought stress, compacted soil and excessive thatch.
White growth visible in the morning does not always confirm dollar spot. Other fungal diseases can produce similar growth when grass remains wet.
Could the Brown Grass Be Dormant?
Warm-season grasses such as Bermuda and zoysia naturally turn tan or brown after cold temperatures cause them to enter dormancy.
Dormancy typically affects most or all of the lawn evenly. Fungal disease, irrigation problems and other damage are more likely to produce isolated circles, rings or irregular patches.
A dormant lawn should begin greening as temperatures warm. Areas that remain brown after the surrounding grass has resumed active growth may need closer inspection.
Other Causes of Brown Spots in a Lawn
Improper Watering
Both drought and excessive moisture can cause brown grass. Dry areas are commonly found on slopes, beside pavement or where sprinkler coverage is incomplete. Overwatered areas may feel soft, remain wet for long periods or develop algae and fungal growth.
Check the soil moisture and irrigation coverage before assuming the lawn needs more water.
Poor Drainage and Compacted Soil
Water that collects in low areas keeps the grass wet and limits oxygen around the roots. Compacted soil can also prevent water and nutrients from reaching the root system effectively.
Core aeration and drainage improvements may help, depending on the underlying problem and grass variety.
Mowing Damage
Cutting grass too short removes too much leaf tissue and places additional stress on the plant. Dull mower blades tear rather than cleanly cut the leaves, producing frayed tips that can make an entire lawn appear brown.
Follow the recommended mowing height for your grass variety, keep mower blades sharp and avoid removing more than one-third of the leaf height in a single mowing.
Pet Urine
Pet urine can create small, round brown spots, sometimes surrounded by a ring of dark green grass. The brown center results from concentrated salts and nitrogen, while the surrounding grass benefits from the diluted nutrients.
Insects and Root Damage
Grubs and other insects can damage grass roots and cause wilting or brown areas. Grass with severe root damage may feel loose and lift away from the soil.
Do not apply an insecticide based only on the appearance of brown grass. Confirm that damaging insects are present first.
Fertilizer or Chemical Damage
Excess fertilizer, gasoline, herbicide and other chemical spills can burn the leaves or roots. Damage may follow a spill pattern, wheel track or application path instead of forming a natural-looking circle.
How to Prevent Fungal Lawn Diseases
Good lawn care cannot prevent every disease outbreak, but it can make conditions less favorable for fungal growth.
Water Early in the Morning
Watering shortly before or around sunrise allows irrigation to work with the lawn’s natural dew period. The grass then has time to dry during the day.
Avoid watering in the late afternoon or evening, which can keep leaves wet overnight. Most established lawns perform best with deep, less frequent watering rather than light watering every day.
Learn more about when and how much to water your lawn.
Avoid Excessive Nitrogen
Excess nitrogen can produce tender, fast-growing leaves that are more susceptible to certain diseases. Apply fertilizer according to your grass variety, the season and soil-test recommendations.
For warm-season grasses, avoid late-season nitrogen applications that encourage new growth as the lawn approaches dormancy. See NG Turf’s fertilizing guide for additional information.
Follow the Correct Mowing Height
Mowing at the proper height helps grass maintain the leaf surface and root system it needs to withstand stress. Avoid scalping the lawn and clean mower blades after cutting visibly diseased areas.
Manage Excessive Thatch
A thick thatch layer can hold moisture near the grass and provide favorable conditions for disease. If the thatch layer is greater than approximately one inch, dethatching may be appropriate.
Improve Sunlight and Air Movement
Dense shade, limited airflow and consistently wet soil can increase disease pressure. Where practical, thin tree canopies, prune low branches and correct drainage problems.
How Do You Treat Brown Patches in a Lawn?
The first step is identifying the cause. Brown grass caused by drought, pet urine, insects or mowing damage will not improve with fungicide.
If fungal disease is suspected:
- Reduce unnecessary irrigation and prolonged leaf moisture.
- Pause excessive nitrogen applications.
- Follow the correct mowing height for the grass variety.
- Bag or disperse heavy clumps of wet grass clippings.
- Avoid mowing when the lawn is wet.
- Have the problem professionally diagnosed before applying a fungicide.
Fungicides are most effective when applied at the correct time and for the specific disease present. They help limit fungal activity but do not immediately turn damaged leaves green or restore dead grass.
Some recurring diseases require preventive applications before visible damage becomes severe. Product selection, application timing and label directions are important, so homeowners may benefit from working with a licensed lawn care professional.
Will Brown Grass Grow Back?
Brown grass can recover if the roots, crowns or growing points remain alive. Recovery depends on the cause, grass variety, time of year and severity of the damage.
Fescue may produce new leaves after a moderate brown patch outbreak. Warm-season grass affected by large patch may recover after active growth resumes, but severely damaged or thinned areas can take longer to fill in.
Grass that is dead at the roots may need to be repaired or replaced after the original problem has been corrected.
Frequently Asked Questions
Q: What is the most common cause of brown patches in a lawn?
There is no single cause for every lawn. In the Southeast, fungal diseases, irrigation problems, drought stress, mowing damage, pet urine and seasonal dormancy are all common. The shape and timing of the damage can help narrow down the cause.
Q: Does brown grass always mean the lawn has fungus?
No. Brown grass may result from insufficient water, excessive water, insects, pet urine, compaction, chemical damage, mowing stress or dormancy. Confirm the cause before applying a fungicide.
Q: Should I water brown patches?
Only if the soil is dry and drought stress is the confirmed cause. Adding water to an area affected by fungal disease or poor drainage can make conditions worse.
Q: Can too much fertilizer cause brown patches?
Yes. Excess fertilizer can burn grass or encourage tender growth that is more vulnerable to disease. Base fertilizer applications on the grass variety, season and soil-test results.
Q: Can a lawn recover from brown patch or large patch?
It often can. Fungicides and improved maintenance can limit additional damage, but existing brown leaves will not immediately become green again. Recovery occurs as healthy new growth develops.
Q: When should I call a lawn professional?
Contact a professional when patches are spreading, returning in the same area, affecting a large portion of the lawn or remaining brown after the rest of the grass begins growing. Professional diagnosis is particularly important before applying fungicides or insecticides.
Get Help Identifying Brown Patches in Your Lawn
Brown patches can have several causes, and an accurate diagnosis is essential before treatment begins. NG Turf’s Certified Turfgrass Professionals can help you understand your grass variety, seasonal care requirements and the factors that may be affecting your lawn.
Call 770.832.8608 or email info@NGTurf.com with your lawn care questions.
