Watering gaps
Dry spots often line up with gaps in sprinkler coverage. Set a few empty cans around the lawn, run the sprinklers and compare how much water each one catches. Adjust or fix heads that miss. Watering deeply and less often is better than short daily cycles.
Fungus
Circular patches, sometimes with a darker or smoky edge, can be a fungal disease. Fungus likes warm, humid weather and wet grass overnight. Water early in the morning, avoid too much fertilizer in hot weather, and ask a pro about a fungicide.
Grubs and insects
If brown grass pulls up easily with few roots, grubs may be eating them. Peel back a section of turf and look for C-shaped white larvae. In some grasses, chinch bugs cause spreading dry patches in sunny spots. Treatment depends on the pest and the season.
Other common causes
- Dog urine: a brown spot with a dark green ring around it.
- Dull mower blades: tips torn and brown instead of cleanly cut.
- Buried debris or rock under a patch that dries out first.
- Mowing too short, which stresses the grass.