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Lawn fungus: large patch, spring dead spot and leaf diseases

Large patch is a common disease of warm-season lawns in South Carolina, caused by the same fungus that causes brown patch in fescue. It shows up as big circular brown patches at spring green-up, but Clemson says fall is the most important time to treat it.

What does large patch look like?

Large patch shows up as circular patches of thinning, yellow or light brown grass, from a few inches to several feet across. The patches may look yellow or orange, with a smoky brown edge where the fungus is active. The center sometimes recovers, leaving a doughnut shape. Pull on the grass at the edge of a patch: if the blades slip out easily with rotted bases, that points to large patch. Warm-season grasses with large patch rarely show leaf spots.

Which grasses get large patch?

Clemson ranks centipede as the most susceptible, followed by St. Augustine and zoysia. All warm-season grasses grown in South Carolina can get it.

Why treat large patch in the fall if I see it in spring?

The fungus is most active when soil temperatures drop below 70 degrees, which happens in late fall and again in spring. Infections that start in the fall often don't show until the lawn greens up. Clemson says fall is the most important time for fungicide, starting in early October once soil cools to 70 degrees, with a follow-up application in April.

What makes large patch worse?

• Nitrogen fertilizer in early spring before full green-up, or in mid to late fall
• Watering too often, or in the evening. Clemson notes the disease spreads fast with more than 10 hours of continuous leaf wetness and recommends watering early in the morning, about once a week in spring and fall.
• Mowing too low, heavy thatch and poor drainage

What is spring dead spot?

Spring dead spot is a disease of bermuda. It leaves bleached, dead spots about 6 to 12 inches across that stay dead well into warm weather while the rest of the lawn greens up. Like large patch, it becomes active as soils cool below 70 degrees, infects in the fall and shows in spring, so fungicides work best as a fall preventive.

What other lawn diseases does Clemson list for warm-season grass?

Clemson lists several leaf diseases on warm-season grass: gray leaf spot, mainly on St. Augustine in warm, rainy summer weather; dollar spot, silver-dollar-sized straw-colored spots on bermuda and zoysia; and rust, orange pustules on zoysia. Each has different conditions and treatment, so diagnosis comes first.

How does Spring Green treat lawn fungus?

We run two fungus programs. Warm-weather fungus control goes down monthly from April through August. Cool-weather fungus control goes down in September, October and March, which lines up with the fall and spring window Clemson gives for large patch.

Last updated 2026-09-25. Spring Green is owned by Stockton Wells.