Brown patch
Roughly circular brown patches in lawns in hot, humid weather, sometimes with a smoky ring at the edge.
What you'll see
- Round to irregular patches of thin, light brown grass, from a few inches to several feet across.
- A dark, smoky ring at the edge of the patch, easiest to see early in the morning.
- Tan leaf spots with dark borders on tall fescue; the center may recover, leaving a ring.
Why it happens
A soil fungus attacks grass blades in hot, humid weather when leaves stay wet for many hours. Lush growth from too much nitrogen, thick thatch and poor drainage favor it. On warm-season grasses, the same fungus causes large patch in spring and autumn.
How to fix it
- Water early in the morning, and only when the lawn needs it, so the grass dries during the day.
- Mow when the grass is dry, mow diseased areas last and collect the clippings in warm, wet weather.
- Hold off on nitrogen fertilizer while the disease is active.
- For a valuable lawn, a fungicide labeled for brown patch can help; follow the label and keep kids and pets off until it dries.
Keep it from coming back
- Feed cool-season lawns mainly in autumn, not in late spring and summer.
- Core-aerate compacted soil and keep thatch thin.
- Mow at the right height for your grass, such as 2.5 to 3.5 inches (6 to 9 cm) for tall fescue.
Sources
General guidance, not a diagnosis. For valuable, edible or outdoor crops, check with a local extension service or plant expert. Use any product exactly as its label says, and keep children and pets away while it dries.