Expanding Circular Yellow or Brown Spots in a Dormant Warm-Season Lawn Can Mean Large Patch Disease, Clemson’s Samantha Brown Warns as Cool, Wet Fall Weather Sets In

Centipedegrass, St. Augustinegrass and zoysiagrass share a fungal disease with a plain name: large patch. Samantha Brown, who writes the Upstate section of Clemson Extension’s November 2026 garden calendar, published Nov. 6, told South Carolina homeowners to watch for it in warm-season turf. Cool, wet fall weather is the perfect storm for it to appear just as the turf is going dormant, the calendar says.

The warning is aimed at the expanding circles that show up in a lawn that is already fading to its winter color. Clemson and North Carolina State Extension publications describe what those circles look like, which grasses suffer most, and why the disease shapes the following spring.

Circles That Keep Growing While the Grass Sleeps

Clemson’s large patch factsheet, written by Joey Williamson of the Home & Garden Information Center, calls it probably the most common and damaging disease of South Carolina warm-season turf. Early on, the circular patches look more yellow or orange. The fungus rots roots, stolons and leaf sheaths, the grass in the patch dies, and the affected area expands outward, sometimes with a smoky brown edge where the fungus is active.

A second Clemson factsheet, on brown patch and large patch, explains that both diseases come from the fungus Rhizoctonia solani, but different strains cause each one. Large patch hits warm-season grasses and is most active in late fall and spring, with most symptoms appearing during spring green-up. It rarely makes leaf spots. Instead, leaf sheaths near the soil surface rot, so leaf blades pull free when gently tugged. St. Augustinegrass in shady, moist areas may thin without forming clear circles.

The size of the damage can surprise a homeowner. Clemson’s zoysiagrass maintenance calendar says the patches can grow to several feet across and that fungicide is needed when the edge of an affected area looks smoky brown and rotted.

Centipede Suffers Most, and Fall Sets Up the Spring

The factsheet ranks the grasses by susceptibility. Centipedegrass is the most susceptible, followed by St. Augustinegrass and then zoysiagrass, while bermudagrass is less severely affected and can outgrow the problem with proper care. North Carolina State Extension’s Disease Management in Landscape Turf, a June 2026 publication by Jim Kerns, Lee Butler and Daniel Freund, lists the same four grasses and says bermudagrass is the least damaged, though the disease can still make it look unsightly after spring green-up.

Clemson’s centipedegrass calendar calls large patch the most common disease in that grass, active during warm, humid spring and fall weather. The calendar makes a point about timing: turf weakened by disease in fall will be slow to recover in spring. That is why the disease is treated as a fall problem even though the worst-looking lawns tend to appear in April and May.

Both universities put the main fungicide window in the early fall. Clemson’s factsheet says to start curative treatments once soil temperatures consistently drop to 70 degrees Fahrenheit for two to three days, with a second application three weeks later. Its table lists Oct. 15 and Nov. 5 for Clemson, Greenville and Rock Hill, and later dates for Columbia, Florence and the coast. The centipedegrass calendar says a preventive treatment may be needed in late September to early October in areas where large patch has been common.

North Carolina State’s publication sets the first application when soil is 75 to 80 degrees in late summer or early fall, with a second within 28 days, and says large patch is easily controlled with two fungicide applications. On spring, the two disagree in emphasis. Clemson lists one spring application when turf begins to green up, while the North Carolina State publication says spring applications have not been shown to be effective in its research and, if needed, would go on when soil is 55 to 60 degrees. Both say granular products need water to work, and the labels set the rules.

What Reduces the Odds Before Another Fall

Clemson’s factsheet says cultural practices may prevent large patch or help control it, but once infection is established, fungicides are likely needed. The practices are specific. Avoid excessive nitrogen in early spring and fall, and skip fertilizer, including winterizers, after Aug. 15 in the Upstate and midstate or after Sept. 1 on the coast. Water no more than once a week in spring and fall, early in the morning. Do not mow too low, prevent thatch buildup and correct poorly drained areas.

The brown patch and large patch factsheet adds that high nitrogen, especially fast-release forms, promotes the lush growth the fungus attacks, and that extended leaf wetness of more than 10 hours favors both diseases. For centipedegrass, it gives a mowing height of 1.5 to 2 inches.

Dormancy brings its own watering rule. The centipedegrass calendar says to water only as needed once the lawn is dormant, and to water if no measurable rain has fallen in three to four weeks, especially before very cold snaps. The zoysiagrass calendar offers the same schedule for that grass. The centipedegrass calendar also suggests potash 4 to 6 weeks before the first frost if a soil test shows low potassium, and no nitrogen in fall.

For a lawn that already shows the circles, the practical sequence is to note where they are now, watch whether they widen through winter, and plan the fall fungicide window ahead of the next season. Clemson’s contact line for lawn disease questions is the Home & Garden Information Center, and the calendar page lists its phone number and email for South Carolina residents.

This article was produced with AI assistance and edited for accuracy against the sources linked above.

Image: Forest and Kim Starr – CC BY 2.0/Wikimedia Commons