Brown circles in St. Augustine? It’s probably large patch.

You notice it in the fall or early spring: a ring of yellow-orange grass, sometimes a few feet across, sometimes the size of a car. The middle may start to green up while the edge keeps spreading. If you have St. Augustine, Zoysia or Centipede, this is almost always large patch, a fungus that loves exactly the weather we get this time of year.

How to know it’s large patch

Walk to the orange edge of the ring and do the tug test. Grab a few blades and pull gently. If they slide right out and the bottom of the stem is dark brown and slimy, the fungus has rotted the leaf sheath. Healthy grass won’t pull free that easily.

• Rings or patches, often with an orange or yellow border
• Shows up when soil temperature is roughly 50–70°F — spring and fall
• Worse after rain, heavy dew or evening watering
• Often starts in low spots, near downspouts or where water sits

What to stop doing tonight

1. Stop evening watering. Water only early in the morning so the grass dries before dark. If it’s been raining, turn the system off entirely.
2. Hold the nitrogen. Feeding a lawn that has large patch in cool weather feeds the fungus. Skip fall fertilizer on affected areas.
3. Don’t spread it. Mow the affected area last and bag the clippings, or rinse the mower deck afterward.

What to put down this weekend

A fungicide labeled for large patch (look for azoxystrobin, propiconazole, flutolanil or thiophanate-methyl on the label) stops the spread. It will not make the brown grass green again — that only happens when the grass grows back.

For the best result, treat when you first see the ring, and treat again in about 30 days if the weather stays cool and wet. Always follow the label rate for your square footage.

How long until it grows back

Warm-season grass doesn’t repair itself in cool weather. A ring that shows up in October usually stays brown until the lawn is actively growing again in late spring. That’s normal. The goal right now is to stop it from getting bigger.

Keep it from coming back

• Fix drainage in the spots where it starts — extend downspouts, fill low areas
• Apply a preventive fungicide in fall when soil temperatures drop toward 70°F, if you’ve had it before
• Keep mowing at the right height (3–4 inches for most St. Augustine) and never scalp it heading into fall
• Thatch over half an inch holds moisture — dethatch in late spring if you have it