Brown Patch Fungus in New Orleans Lawns: What It Looks Like and Whether the Grass Comes Back

At TurnKey Lawn Care lawn disease control is part of the seasonal care we provide across the metro. If you’d like a second set of eyes on a spreading ring, ask for a free estimate and we’ll tell you whether it’s fungus, insects or water.

Below: how to recognize it, why the weather in spring and fall sets it off, what makes it worse, how it’s managed, and what to expect as the grass recovers.

Brown patch or large patch: the same problem

What brown patch looks like on St. Augustine

LSU describes the symptoms as large circular or irregular patches of yellow to brown turf. On St. Augustine, the leading edge of the patch has a yellowish cast. Centipede grass shows a reddish edge instead. The patches can be small at first and, as LSU puts it, become quite large if not treated. The center sometimes starts to green up while the edge keeps advancing, which gives the patch its ring shape. The quickest test is a gentle tug. LSU explains that the fungus causes a rot at the base of the leaf sheaths, so leaves separate from the crown and pull off the stem easily. You’ll often see a dark, water-soaked area where the leaf meets the runner. Signs that point toward brown patch rather than something else:

• The patch appeared in spring or fall, not in the hottest, driest part of summer
• It’s round or roughly round, with a yellow edge and sometimes a recovering center
• Leaves slide off the runner with a light pull, showing a dark, rotted base
• It started near a fence, hedge or tree line, or in a low spot that stays wet

Brown patch compared with other lawn problems

Several problems turn St. Augustine yellow and brown. Our page on why a lawn gets brown patches covers the full list, and this table sets out the most common confusions.

Clue	Brown patch	Chinch bugs	Drought stress
Season	Spring and fall	Hot, dry mid-to-late summer	Dry spells, usually summer
Where	Shaded, sheltered or low wet spots	Full sun near pavement	Whole sunny area at once
Shape	Circular or irregular, yellow edge	Irregular, spreading outward	Broad, uneven dulling
Tug test	Leaves pull off a rotted base	Blades dry, runners anchored	Blades folded but firmly attached

A soapy-water flush at the edge of a patch rules chinch bugs in or out. If nothing comes up and the leaves slide off a rotted base, fungus is the likely answer.

Why spring and fall set it off

Temperature is the trigger. LSU reports that large patch develops rapidly when nighttime temperatures range from 60 to 75 degrees Fahrenheit and daytime temperatures don’t exceed 85 to 90 degrees. In the New Orleans area, that window tends to open in the fall as nights cool down and again in spring before summer heat settles in. Add a stretch of rain or heavy dew and the grass stays wet long enough for the fungus to move. An LSU AgCenter article on fall brown patch adds a detail anyone with a fenced yard will recognize. The disease tends to develop first in areas surrounded by trees, shrubs and fences, which reduce air movement and slow the drying of the grass.

What makes brown patch worse

LSU names a set of conditions that promote the disease. Most of them are things a homeowner can change.

How brown patch is managed

Management works best as a combination of changing conditions and, where the disease is active, fungicide. Here is the order we’d work through it in:

1. Confirm the cause. Tug-test the leaves at the yellow edge and run a soapy-water flush to rule out chinch bugs before treating anything.
2. Move watering to early morning. Water only when the lawn needs it, and let rain count toward the week’s total.
3. Hold off on heavy nitrogen. Follow a soil test, and stay at or under 1 pound of nitrogen per 1,000 square feet per application.
4. Open up the air. Trim back shrubs crowding the lawn and reduce excess thatch when the grass is actively growing.
5. Treat when disease is present. LSU’s fall article recommends at least two fungicide applications when disease is present, the first in mid- to late September and the second in mid- to late October.

That LSU article names several fungicide active ingredients used for brown patch, including myclobutanil, propiconazole, thiophanate-methyl and triadimefon. Product choice, rate and interval come from the label, which has to be followed exactly. Formulation matters too. LSU notes that a sprayed fungicide should be allowed to dry before more water is applied, while a granular product must be watered in to activate it. Many homeowners hand this part off, especially when a patch keeps spreading through a wet October. We handle fungicide timing as part of our seasonal lawn care program, alongside the watering and feeding changes that keep it from coming back.

A prevention checklist before the fall window opens

Brown patch comes back to the same yards because the same conditions come back every year. The weeks before nights cool into the 60s and low 70s are the time to set the lawn up so it dries quickly and isn’t pushed into soft growth.

• Switch any irrigation timer from evening to early morning, and cut back run times once regular rain returns
• Skip the heavy late-summer nitrogen push, and use a soil test to decide what the lawn needs
• Trim shrubs and low limbs that trap still air over the lawn along fences and beds
• Walk the yard after a heavy storm and note which spots hold water, because those are the first places to watch
• Keep mowing at the right height for St. Augustine instead of scalping it before winter

If the same corner of the yard gets large patch every year and stays wet for days after rain, the long-term fix is often drainage rather than more fungicide. Our drainage solutions for wet yards cover the options, from regrading a low spot to adding a drain.

Will the grass come back after brown patch

Usually, yes. LSU explains that the pathogen doesn’t usually kill the grass. It rots the base of the leaf sheaths so the leaves separate from the crown, and the runners themselves often survive. That’s why a patch can look dreadful in November and fill back in once the weather turns and the lawn dries out. Recovery is faster when the conditions that fed the disease are corrected, because the same patch will reappear next season if they aren’t. Areas that stay bare after the lawn is actively growing again may need help from the edges, from plugs or from sod. Weeds move into thin turf quickly, which LSU also notes, so a thin patch left alone often becomes a weed patch.

Frequently asked questions