Those circular brown spots in your lawn are usually not from lack of water. This guide will help you accurately identify brown patch disease in North Texas lawns.
This is one of the most common fungal issues we see in Collin County, including neighborhoods across Plano and Frisco, especially near Legacy West and Stonebriar.
So what is brown patch disease?
Without getting too technical, it’s a lawn fungus called Rhizoctonia solani. It tends to show up when conditions are right and can spread fast if it is mistaken for drought stress or another common lawn problem.
If you’ve been adjusting your sprinklers, second-guessing your water schedule, and watching the patches get bigger, then this guide will help you figure out what’s really going on.
We’ll walk through how to identify brown patch disease, what causes it, and what to do once you know that’s the problem.
No guesswork. Just a clear path forward from the team at CitiTurf.
At CitiTurf, we see brown patch most often in St. Augustine lawns during humid stretches of spring and fall in North Texas.
What Is Brown Patch Disease?
So what exactly is brown patch disease?
Brown patch disease is a fungal lawn disease caused by Rhizoctonia solani, a pathogen that lives in the soil year-round.
When conditions line up, the fungus activates and attacks the leaf blades of your grass:
- Warm temperatures
- High humidity
- Too much moisture
The worst part?
Most homeowners don’t even realize the fungus is likely already in their soil. It doesn’t blow in from somewhere else. It sits dormant, waiting for the right mix of heat and moisture.
In North Texas, those conditions show up reliably every year, usually in late spring and again in early fall.
The good news is that brown patch disease typically damages leaf blades and sheaths, not the roots. That means your lawn can usually recover, especially with the right response.
According to Texas A&M AgriLife Extension, brown patch is the most widespread fungal disease in Texas lawns, hitting St. Augustine and tall fescue hardest.
What Brown Patch Looks Like in a Lawn
Knowing what brown patch looks like is the first step toward fixing it.
Here’s what to look for:
Visual signs of brown patch in your lawn:
- Circular patches — Irregular to roughly circular areas of brown or yellowing grass, ranging from a few inches to several feet across.
- “Smoke ring” border — A dark, grayish-purple ring along the outer edge of the patch, most visible in the early morning when dew is present. This is the active edge where the fungus is spreading.
- Leaf blade lesions — Individual grass blades develop tan or brown spots with darker borders. Early on, they may look water-soaked at first.
- Easy pull test — Grass blades pull away easily from the runner because the fungus weakens the leaf sheath.
- Thinning canopy — The grass within the patch looks thin or matted, but the stolons and roots underneath are still intact.
Brown Patch Lawn Disease Identification Chart
| Feature | What You’ll See |
| Patch shape | Circular to irregular, 6 inches to 3+ feet |
| Patch color | Yellow-brown to tan |
| Border | Dark “smoke ring” (most visible in early morning) |
| Leaf lesions | Tan spots with dark brown edges |
| Timing (North Texas) | Late spring and early fall |
| Grass types affected | St. Augustine, tall fescue, Bermuda (less common) |
| Root damage | Minimal — roots usually survive |
This pattern (circular patches with a visible smoke ring) is the fastest way to identify brown patch disease in North Texas lawns.
Brown Patch in St. Augustine Grass
If you have St. Augustine grass — and a lot of homeowners in Plano, Frisco, Allen, and McKinney do — this is where you need to pay close attention. We see this most often in established neighborhoods near Watters Creek, Craig Ranch, and Eldorado Parkway.
St. Augustine is one of the most susceptible grass types to brown patch lawn disease. Its thick, broad blades hold moisture longer, creating ideal conditions for fungus to develop. On top of that, the dense canopy limits airflow at the soil level, trapping humidity right where the disease starts.
In North Texas, brown patch in St. Augustine typically shows up in two key windows:
- Late April through June — when nighttime temperatures consistently reach 65°F or higher and spring rains keep the lawn damp.
- September through November — when warm days, cooler nights, and fall moisture create a second wave.
The good news is that brown patch usually affects the leaf blades and sheaths, not the stolons or roots. That means St. Augustine can recover once conditions improve or treatment is applied.
However, repeated infections year after year can weaken the turf, leading to thinning and a less resilient lawn over time.
In our experience, St. Augustine lawns with dense shade, frequent irrigation, or poor airflow tend to show symptoms first.
Brown Patch vs Other Lawn Problems
This is where a lot of homeowners get tripped up. Brown spots can come from several different issues, and treating the wrong one wastes time and money.
Here’s how brown patch disease symptoms compare to other common North Texas lawn problems:
| Problem | What It Looks Like | Key Difference from Brown Patch |
| Drought stress | Uniform browning; grass doesn’t spring back when stepped on | No circular pattern, no smoke ring, and the lawn is affected evenly |
| Chinch bugs | Yellow-to-brown patches, often starting along sunny edges | Damage spreads outward from edges, not in circles; insects may be visible at the soil line |
| Grub damage | Brown patches that lift like loose carpet | Sod peels up easily because roots are eaten; brown patch doesn’t destroy roots |
| Take-all root rot | Yellow-brown patches with thinning turf | Roots appear dark and rotted; develops over months, not weeks |
| Dog urine | Small brown spots with a bright green ring | Much smaller patches with a distinct green halo and random placement |
If you’re still not sure what you’re dealing with, look for the “smoke ring.”
Check your lawn early in the morning when dew is still on the grass. That dark, grayish border around the patch is one of the clearest signs of active brown patch fungus.
Causes That Trigger Brown Patch Fungus
Remember, the fungus is already in your soil. The real question is: what activates it?
Here are the main triggers in North Texas:
Temperature and Humidity
Brown patch fungus becomes active when nighttime temperatures stay above 65°F and daytime highs range from 80–95°F. Pair that with humidity above 80%, and conditions are ideal.
In Collin County, this usually happens between May and September. In some years, it can stretch into April and October.
Overwatering and Poor Drainage
This is the biggest trigger.
Watering too often, watering in the evening, or having low spots that stay saturated keeps grass wet for too long. That extended moisture is exactly what the fungus needs to spread.
Research shows that leaf wetness lasting more than 10 hours significantly increases the risk of brown patch.
Excessive Nitrogen Fertilization
Too much nitrogen, especially at the wrong time, pushes fast, lush growth that’s more vulnerable to disease.
Heavy spring fertilization on St. Augustine is one of the most common mistakes we see. It may look great at first, but it often sets the stage for brown patch just a few weeks later.
Thatch Buildup
A thatch layer thicker than about ½ inch traps moisture at the soil surface, creating the perfect environment for fungus to thrive.
Regular aeration and proper lawn care help keep thatch under control.
Poor Air Circulation
Lawns surrounded by fences, dense landscaping, or heavy tree cover don’t dry out properly.
These shaded, enclosed areas are often the first places brown patch shows up — and the last places it goes away.
This is especially common in neighborhoods with mature trees and dense landscaping, like those around Arbor Hills Nature Preserve or older Plano communities.
Quick Checklist to Confirm Brown Patch
Before you call a professional, run through this quick checklist:
- Circular or roughly circular brown patches in the lawn?
- Dark “smoke ring” border visible in the early morning?
- Individual grass blades show tan lesions with dark brown edges?
- Grass blades pull easily from the stolon?
- Nighttime temperatures have been above 65°F recently?
- Lawn has stayed wet for extended periods (rain, irrigation, poor drainage)?
- Patches appeared quickly — within days, not gradually over weeks?
If you checked three or more, you’re very likely dealing with brown patch.
At this point, it’s time to take action before it spreads further.
What to Do After You’ve Identified Brown Patch
Okay, so you’re pretty sure it’s brown patch. Now what?
The key is confirming the cause before treating it, since brown patch is often confused with drought stress, grub damage, or take-all root rot.
Step 1: Adjust your watering
Water early in the morning (before 8 AM) so the grass has time to dry during the day. If you’ve been watering daily, scale it back.
Most North Texas lawns need about 1 to 1.5 inches of water per week, split across 2–3 watering days — not every night.
Step 2: Pause fertilization
If you’ve been applying nitrogen, stop for now. Fertilizing during an active outbreak can accelerate growth and make the fungus spread faster.
Step 3: Improve air circulation
Trim back low-hanging branches and dense shrubs around affected areas. The faster your lawn dries out, the harder it is for the fungus to continue spreading.
Step 4: Get a professional diagnosis and treatment plan
At this point, you’re dealing with an active fungal disease, not just a lawn care issue.
A targeted fungicide application can stop the spread and protect healthy turf. At CitiTurf, our technicians identify the specific conditions causing the outbreak on your property and build a treatment plan around that — not a one-size-fits-all approach. We also treat related issues like take-all root rot and dollar spot.
