Summer Patch Disease: How It Differs From Brown Patch in Texas Lawns

When circular brown patches appear in a North Texas lawn during the heat of summer, most homeowners reach for the same diagnosis: brown patch. It’s the most notorious lawn fungus in Texas, and for good reason — it genuinely is widespread. But there’s another disease that mimics it closely and gets misidentified constantly: summer patch. Treating summer patch the same way you treat brown patch is a recipe for wasted money and a lawn that keeps declining. Knowing the difference is critical.

At Hamann Lawn Care & Weed Control, we’ve been diagnosing and treating lawn diseases in the Arlington and DFW area since 2006. We see summer patch confused with brown patch every season, and the confusion is understandable because both produce roughly circular dead zones in turf. But once you understand what’s actually happening beneath the surface, the diseases are not alike at all.

Two Completely Different Fungi

The most fundamental difference between summer patch and brown patch is the pathogen responsible for each.Brown patch is caused by Rhizoctonia solani, a soil-borne fungus that primarily attacks leaf blades and leaf sheaths. It is a foliar disease — the damage happens above the soil line.Summer patch, by contrast, is caused by Magnaporthe poae, a fungus that infects and destroys the root system, crowns, and lower stems of grass plants. It is a root disease. That distinction drives every difference in how each disease looks, when it appears, and how it should be treated.

When Each Disease Strikes in DFW

Timing is one of the clearest diagnostic clues available to North Texas homeowners. Brown patch in our region is most active when nighttime temperatures are above 70°F and humidity is high, combined with daytime temperatures in the 80s and 90s. In DFW that typically means active brown patch from May through September, with the most aggressive outbreaks during stretches of warm nights and afternoon thunderstorms.

Summer patch has a deceptive timeline. The infection actually begins in late spring, often in April and May, when soil temperatures reach 65 to 70°F. Magnaporthe poaeinvades roots during that cooler window before the heat fully arrives. The visible symptoms, however, don’t appear until mid-summer when heat and drought stress push the weakened, already-infected root system past its limit. This lag means a lawn that looks fine in May may suddenly collapse in July or August — and the homeowner has no idea the infection began months earlier. By the time they’re looking at the damage, the active root infection has often already subsided.

Which Grasses Are Affected

Another key difference lies in host susceptibility. Brown patch has an extremely broad host range and attacks St. Augustine, bermuda, zoysia, tall fescue, and most other warm- and cool-season grasses common in North Texas. Summer patch is more selective:

• Kentucky bluegrass is the primary and most severely affected host, though this grass is uncommon in DFW landscapes.
• Fine fescues (hard fescue, chewings fescue, creeping red fescue) are highly susceptible. These are sometimes used in shadier parts of DFW lawns or in overseeding mixes.
• Bermudagrass can be affected by Magnaporthespecies, and what is sometimes called “summer patch” in bermuda may involve related pathogens attacking the crown and root zone under similar heat conditions.
• Annual bluegrass (Poa annua), a common winter weed in DFW turf, is also a known host.

Notably, St. Augustine — the most popular lawn grass in North Texas — is less commonly targeted by classic summer patch (Magnaporthe poae) and is more typically affected by take-all root rot when root diseases are the concern. If you have a St. Augustine lawn with circular summer decline, brown patch or take-all root rot are more likely culprits than summer patch specifically.

Reading the Symptoms: What to Look For

Visual symptoms of both diseases overlap enough to cause confusion, but there are distinguishing features if you look carefully.

Brown patch symptoms:Patches are circular to semi-circular, often with a darker, water-soaked ring at the advancing edge (called a “smoke ring”) that is most visible in early morning when dew is present. The interior of the patch tends to recover or at least stay alive while the perimeter continues to spread. Individual blades show lesions with tan centers and brown borders. Because the disease attacks leaf tissue, recovery can happen relatively quickly once conditions improve and fungicide is applied.

Summer patch symptoms:Patches are also roughly circular but tend to be slightly smaller and more distinct, often with a ring of bronze or reddish-tan grass surrounding a center that may actually look greener (the classic “frog-eye” pattern). The outer ring dies from the outside in as roots fail to support the canopy. Pull affected grass by hand — if it comes up easily with dark brown or black, rotted roots and crowns, summer patch is very likely. The roots are destroyed at the crown level, which is why the grass cannot recover even if you water more.

• Smoke ring visible in morning dew → points to brown patch
• Grass pulls up easily with blackened, mushy roots → points to summer patch
• Frog-eye pattern with green center and bronze ring → classic summer patch indicator
• Individual leaf blade lesions with tan centers → consistent with brown patch

Treatment Differences: Why It Matters

Because brown patch is a foliar disease and summer patch is a root disease, they respond to different fungicide classes and application timing.

Brown patch responds well to contact and systemic fungicides applied when the disease is active. Azoxystrobin (a strobilurin) and propiconazole (a DMI/triazole) are commonly used and effective when applied at the first sign of leaf lesions or as a preventive application in late spring. Repeat applications every 14 to 28 days during the active season control the spread.

Summer patch requires preventive fungicide applicationbefore symptoms appear, because by the time patches are visible the root damage is done. The window for effective fungicide application is late spring — when soil temperatures are between 65 and 70°F at a 2-inch depth, typically April to May in DFW. DMI fungicides (triazoles like propiconazole, tebuconazole, or myclobutanil) are the most effective chemistry for summer patch because they move into the plant systemically and protect root tissue. Strobilurins alone are less effective against Magnaporthe poae at the root zone.

If you’re already seeing summer patch damage in July, fungicide applications at that point will not restore dead root systems but can protect adjacent healthy turf from further infection for the remainder of the season. Recovery requires the remaining live plants to fill in through tillering and stolons, which takes time and proper cultural support.

Cultural Practices That Reduce Both Diseases

Regardless of which disease is present, certain cultural practices reduce vulnerability significantly:

• Avoid overwatering and evening irrigation— both diseases thrive in wet conditions, especially overnight. Water in the early morning so turf dries before nightfall.
• Reduce thatch — thick thatch harbors Magnaporthe poae and other pathogens and reduces fungicide penetration to the root zone. Dethatch bermuda and zoysia annually.
• Mow at the correct height— scalping or mowing too short stresses roots and makes summer patch much more severe. Keep bermuda at 1 to 1.5 inches and St. Augustine at 3 to 4 inches.
• Avoid high-nitrogen fertilizer in late spring— excessive nitrogen promotes lush, disease-susceptible growth right when summer patch infection is beginning underground.
• Improve soil drainage— compacted, poorly draining areas are where both diseases concentrate. Core aeration in spring helps drainage and reduces the conditions summer patch needs to infect roots.

Getting the Right Diagnosis Saves Time and Money

Misdiagnosing summer patch as brown patch means applying fungicide at the wrong time, with the wrong active ingredient, against damage that has already occurred underground. It’s one of the most common and expensive mistakes we see in DFW lawns every summer. A professional evaluation in spring — before symptoms appear — is the most effective way to get ahead of summer patch if your lawn has a history of circular summer decline.

Our team at Hamann Lawn Care & Weed Control has served Arlington and the greater DFW area since 2006. We diagnose lawn disease and fungus problems on-site and build treatment programs timed to actual soil temperatures and DFW weather patterns, not generic calendar schedules. If your lawn develops mysterious patches every summer, let us take a look before you spend another season guessing.

Also worth reading: our post on necrotic ring spot disease in DFW lawns covers another root-infecting patch disease that is frequently confused with both summer patch and brown patch, with its own distinct diagnosis and treatment path.