Brown Patch in St. Augustine Lawns: How to Identify and Treat It in Louisiana
Brown Patch in St. Augustine Lawns: How to Identify and Treat It in Louisiana
Brown patch is a fungal disease that appears in St. Augustine lawns as roughly circular patches of tan or straw-coloured grass, usually one to several feet across, that expand outward while the centre sometimes recovers. In South Louisiana it shows up when nights cool into the 60s with heavy dew — typically October through November, and again in spring. The grass pulls away easily at the base with rotted, dark leaf sheaths, and the roots stay firmly attached.
By Alice Lily · Lawn Care Lafayette LA · Published 14 September 2026
What Does Brown Patch Look Like?
The classic sign is shape. Brown patch forms circular or arcing patches with a relatively defined edge, and as the patch grows the interior can green up again, producing a ring. That pattern is the single most reliable way to distinguish it from drought stress or insect damage, which tend to be irregular and diffuse.
The second confirmation is the tug test. Take hold of a few blades at the edge of a patch and pull gently. With brown patch, the leaf comes away from the runner easily and the base of the sheath is dark, soft and rotted — the fungus attacks the leaf sheath rather than the root. The runner and roots themselves stay anchored in the soil. If the entire plant lifts away with no root resistance at all, you are looking at a different problem, most likely take-all root rot or insect damage rather than brown patch.
On heavy dew mornings you may also see a faint grey-white edge at the boundary of an active patch. That is the fungus actively growing, and it disappears once the dew burns off.
Brown Patch vs. Other Common Lafayette Lawn Problems
Most misdiagnosis in Acadiana comes from treating a fungal problem as a watering problem, or the reverse. This is what separates them.
Why Does Brown Patch Happen in Louisiana Lawns?
The fungus responsible — Rhizoctonia solani — is present in virtually all Louisiana soil already. It does not arrive from somewhere; it becomes active when conditions favour it. Three things trigger that in Acadiana.
- Extended leaf wetness. Warm days, cool nights and heavy dew mean grass blades stay wet for long stretches. That is the primary driver, and it is exactly what October and November deliver here.
- Excess nitrogen at the wrong time. Heavy nitrogen feeding late in the season pushes soft, lush growth right as disease pressure peaks. This is the most common self-inflicted cause we see, and the most avoidable.
- Poor drainage and air movement. Acadiana’s clay holds water, and yards that stay damp with little air circulation keep leaf surfaces wet far longer than they should be.
How Do You Treat Brown Patch?
Treatment is mostly about removing the conditions that keep the fungus active, with fungicide reserved for cases that are actively spreading. Cultural changes do the majority of the work, and they are what stop it recurring next season.
Water in the early morning, not the evening. Watering between roughly 4am and 8am lets the sun dry the blades within a couple of hours. Evening watering adds hours of leaf wetness to a night that already brings dew, which is close to ideal conditions for the fungus.
Stop nitrogen once the disease is active. Feeding a lawn showing brown patch accelerates it. Hold off until the lawn has recovered and conditions have changed.
Do not cut it short. St. Augustine belongs at 3 to 4 inches, and a stressed lawn needs that leaf area to recover. Bag the clippings while the disease is active rather than mulching them back onto the lawn, and clean the mower deck afterwards.
Improve drainage where the patches keep returning. If the same low area develops brown patch every autumn, the underlying issue is that the ground there stays wet. Correcting the drainage solves it permanently in a way that repeat fungicide applications will not.
Where a patch is expanding quickly, a labelled fungicide can halt it — but timing and rotation matter, and a fungicide applied to a lawn that is still being watered at night will simply be overwhelmed again.
Will the Grass Grow Back?
Usually, yes. Brown patch attacks leaf tissue rather than killing the runners and roots outright, so an affected area typically recovers once conditions change — though recovery may not be visible until the lawn resumes active growth in spring.
That delay causes a lot of unnecessary worry each winter. A patch that browns out in November and still looks bare in January is not necessarily dead; warm-season grass is dormant and simply is not growing. The honest test comes in March and April, when the surrounding lawn greens up. If the patch stays bare into late spring while everything around it fills in, then the runners did die and the area will need overseeding or plugging to close.
Preventing It Next Season
Brown patch is far easier to prevent than to cure, and prevention is a calendar problem more than a product problem.
Shift the bulk of nitrogen feeding earlier in the growing season so the lawn is not pushing soft growth into autumn. Move irrigation to early morning permanently, not just while symptoms show. Keep the mowing height up. Relieve compaction so water moves down through the soil instead of sitting at the surface. And where shade and poor air movement combine — common beneath the mature live oaks on older Lafayette and Carencro streets — selective canopy thinning improves both light and airflow at once.
Most lawns that get brown patch badly get it every year, because the conditions causing it are structural rather than random. Fixing the structure is what breaks the cycle.
Brown Patch FAQ
When is brown patch season in Louisiana?
Primarily autumn, from roughly October into November as nights cool into the 60s with heavy dew, and again in spring during the transition out of dormancy. Peak summer heat generally suppresses it.
Is brown patch the same as large patch?
They are caused by the same fungus. The name large patch is commonly used when it affects warm-season grasses such as St. Augustine and Zoysia, which is what we deal with in Louisiana.
Can brown patch spread to the rest of my lawn?
Yes. Patches expand outward while conditions remain favourable, and mowing across an active patch can move the fungus. Bag clippings and clean the deck while the disease is active.
Should I water more if my grass is turning brown?
Not if it is brown patch — extra water makes it worse. Confirm the cause first. Drought stress follows high ground and leaves footprints visible in the turf; brown patch forms defined circular patches and the blades pull free from rotted sheaths.
Does brown patch mean my lawn will die?
Rarely. It damages leaf tissue rather than killing runners and roots, so most lawns recover. Persistent bare areas into late spring, once the rest of the lawn has greened up, indicate that patch needs reseeding or plugging.
Not Sure What’s Killing Your Lawn?
Send a photo or describe what you’re seeing and we’ll tell you what it is — brown patch, insects, drainage, or something else. Serving Lafayette, Broussard, Youngsville, Carencro, Scott and Milton.
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