Start with the pattern, grass identity and timing. Brown color is a symptom; brown patch is also the name of a disease. Several causes can overlap, and not every discoloration requires a treatment.
Match the pattern to the next check
This is an investigation checklist, not a disease-identification key. Several rows may fit the same patch.
| Pattern or detail | Check next | Useful follow-up |
|---|---|---|
| Dry strip beside sprinkler coverage | Collect water at the strip and the healthy area during the same run; inspect soil moisture. | Measure irrigation delivery. |
| Repeated path to a gate or play area | Compare traffic, roots and soil resistance at similar moisture. | Separate compaction from drainage. |
| Lines matching application or mowing passes | Record dates, material, settings and cut height; inspect individual leaf tips. | Check spreading technique or review mowing. |
| Thinning under trees or persistent wetness | Record sunlight and where water arrives; compare a surviving patch. | Check shade or trace water movement. |
| Leaf lesions, poor roots or an expanding boundary | Save close photographs, grass identity and progression; arrange local diagnosis if uncertain. | Record suspected grub evidence; do not infer a pesticide need from color or a single insect. |
References: Maryland Extension’s diagnostic tables and Clemson’s brown patch and large patch guidance. Their disease and seasonal guidance is regional; use your local service for an uncertain identification.
Record the pattern and timeline
Take a wide photograph showing the patch beside paths, trees and irrigation, then a close view of the healthy-to-damaged edge and individual leaves with an object for scale. Save the date, grass or cultivar if known, recent rain, mowing changes and product applications. Photograph the same boundary again to track change.
Compare one suspected cause at a time
Use a nearby healthy area as a comparison. If the shape follows irrigation, measure the water delivered at both locations. If it follows traffic or application passes, check the matching history. These observations guide the investigation; they do not prove a disease, insect or nutrient deficiency.
Ask for help when the evidence is unclear
For expanding damage, uncertain identification or recurring failure, contact a local Extension office or plant clinic. Ask about its photo and sample requirements before collecting material. Keep leaves, roots and the care history available; choose a treatment only after the cause and grass-specific response are supported.
Brown patch and large patch: compare the right clues
Both are named turf diseases. Their names are sometimes used loosely, so give a diagnostic service the grass identity, weather and tissue symptoms rather than reporting only “brown circles.” Clemson’s South Carolina guidance and UF/IFAS’s Florida guide provide these distinctions.
| What to record | Brown patch on cool-season turf | Large patch on warm-season turf |
|---|---|---|
| Common hosts in these references | Tall fescue, perennial ryegrass and Kentucky bluegrass, among others. | Centipedegrass, zoysiagrass and St. Augustinegrass. |
| Timing and wetness | Clemson describes activity during late spring and summer, with prolonged leaf wetness; warm winter periods can also allow it. | Clemson describes fall and spring activity. UF/IFAS describes Florida occurrence mainly November–May under cooler, persistently wet conditions. |
| Where to inspect and photograph | Leaf blades may have irregular pale-tan lesions bordered in dark brown. Not every affected cool-season grass shows distinct lesions. | Look at the leaf base and sheath near the soil. Basal rot and leaves detaching can be clues; UF/IFAS notes that herbicide injury can also let St. Augustine leaves detach. |
Clemson HGIC 2150: Brown patch and large patch (updated August 21, 2025) · UF/IFAS LH044: Large patch. These are regional examples, not a diagnosis for an unidentified lawn. A ring, a tug on a leaf or a season label alone cannot select the cause or treatment.
Will a fungicide make the brown grass green again?
UF/IFAS explains that large-patch recovery depends on new grass growth; a fungicide does not itself produce that growth. After confirmation, discuss the lawn’s condition and a suitable management plan with local Extension. A product mentioned in a reference is not automatically labeled for your grass, site and use.
Use the four-photo checklist and clinic handoff record. Keep the exact recent herbicide, fertilizer and irrigation history with the photographs.
Open the printable diagnosis worksheet and field record
Turn the pattern into a useful check
Each row suggests something to investigate. Several causes can overlap, so these patterns must not be used as a definitive identification key.
Download the printable worksheet One page · PDF · print or fill in a compatible PDF app
| What you see | A useful comparison | Evidence to keep |
|---|---|---|
| Lines matching mower or spreader passes | Look at cut height, wheel tracks and the recent application path. | Wide photo, equipment settings and product dates. |
| A dry strip at the edge of a sprinkler zone | Measure coverage there and in a healthy area during the same run. | Individual catch-cup depths and a zone sketch. |
| Thinning on a route to a gate | Compare roots and soil condition with nearby unused turf. | Traffic pattern, moisture and repeat photographs. |
| A patch expanding beyond an obvious use pattern | Inspect leaves and roots; check local disease and insect guidance. | Dated boundary photos, close-ups and grass identity. |
| Poor growth in a shaded or persistently wet corner | Compare light and water movement with a healthy patch. | Light observations, rain dates and how long water remains. |
- Take three photo scales
Capture the whole setting, the healthy-to-damaged edge and close leaf details with an object for scale.
- Write the timeline
Include the first symptom date and the treatments or weather changes that came before it.
- Send evidence before shopping
Ask the local clinic which sample and records it needs; choose treatment after the cause is narrowed down.
“Brown patch” is both a casual description of discolored turf and the name of a particular disease. Seeing a brown patch does not establish that disease, and a fungicide will not repair a sprinkler gap or worn walking route.
Your field record
Copy these headings into a notebook or a note on your phone, then keep the before-and-after observations together.
- Grass and cultivar if known
- First symptom date and whether it is spreading
- Photos of setting, edge and leaves
- Rain, irrigation and mowing changes
- Product names, amounts and dates
Common questions
Should I spray fungicide as soon as I see brown grass?
Choose treatment from a supported diagnosis. Brown areas can result from several unrelated causes, and the correct action depends on the problem and turf species.
Can I diagnose the lawn from a single phone photo?
A photo can help narrow possibilities, but often cannot establish the cause. Add a wide view, close details, grass identity, progression and a care history; a clinic may also need a sample.
What to send to a plant clinic
Ask the receiving service for its instructions first. Keep the grass identity, a dated wide view, edge and leaf photos, recent applications and watering history together. Describe observations rather than naming an unconfirmed disease.
If the clinic asks for a physical turf sample
Clemson’s clinic requests recently affected turf that includes the boundary between damaged and healthy grass, with roots and soil attached. A fully dead center alone may be unhelpful. It advises prompt submission without adding water or wet paper towels. Clemson Plant and Pest Diagnostic Clinic: Submission guidelines.
Ask your receiving service for its current sample size, permitted material, packaging, shipping and fee instructions before cutting or mailing anything. Include the completed form and sample ID. A wide photo and a soil fertility sample are not substitutes for the plant material a disease clinic requests.
Illustrative example: a dry strip that matches a sprinkler boundary suggests measuring coverage. Lower collected depth there would support investigating delivery, but would not exclude another cause. This is an example of reasoning, not a completed lawn trial.
Once the cause is understood, choose seed, sod or plugs suited to your grass. Buying a repair material before fixing the growing conditions can repeat the failure.
What if the clinic report finds no disease?
A report finding no pathogen in the submitted sample is not proof that every part of the lawn is disease-free. Kentucky’s March 2026 diagnostic fact sheet explains two possibilities: inadequate material, or a problem caused by environmental or cultural conditions rather than an infectious disease. Ask the diagnostician what the result supports and whether other tissue, photographs or site history would help. University of Kentucky: Diagnosis of “No Disease,” March 2026.
Confirm the service, not just the sample address
A photograph suggesting application injury does not identify a chemical residue. Missouri’s clinic, for example, does not test pesticide residues or other contaminants; plant-nutrient, soil and nematode work use other services. This is a service-scope example, not a rule for every clinic. Before collecting another sample, ask which question the receiving lab can answer, what material it needs and whether separate testing is necessary. Missouri Plant Diagnostic Clinic: Service scope, undated.
Keep the report with the clinic handoff record. Describe observed changes instead of substituting a disease name for the evidence.
Do not treat every brown area as fungus, drought or grubs based on color alone.