Brown Patches in Your Lawn: 6 Causes and How to Tell Them Apart
Brown spots can mean fungus, grubs, chinch bugs, dog urine, drought or a dull mower blade. Here is how to tell which one you have before you treat it.
A brown patch is a symptom, not a diagnosis. The same dead-looking spot can come from a fungus, an insect, a dog, the weather or your mower, and each one needs a different fix. Treating the wrong cause wastes money and can make things worse: fungicide does nothing for grubs, and extra water feeds most lawn diseases.
Start by looking closely at three things: the shape of the patch, the grass blades themselves, and what is under the turf.
1. Drought stress or summer dormancy
What it looks like: Large, irregular areas that fade from green to blue-gray to straw-colored. Slopes, south-facing spots and areas near pavement go first. Footprints stay visible long after you walk across it.
How to confirm: Push a screwdriver into the soil. If it is hard to push in, the soil is dry. Dormant grass crowns are still alive, so pull a few blades: the base should be firm, not mushy or rotted.
Fix: Water deeply and less often (see our lawn watering guide). Dormant cool-season grass usually greens up again when temperatures drop and rain returns.
2. Brown patch and other fungal disease
What it looks like: Roughly circular patches, often from a few inches to several feet wide, that appear during hot, humid weather. On tall fescue and ryegrass, brown patch often shows a darker “smoke ring” border early in the morning. Individual blades may have tan lesions with a dark brown edge.
How to confirm: Look at single blades, not the whole patch. Lesions or spots on the blades point to disease. Wet nights, evening watering and heavy nitrogen in summer make it more likely.
Fix: Water only in the early morning so blades dry quickly, avoid high-nitrogen fertilizer in hot weather, and improve air flow. Fungicides can help in severe cases, but get the disease identified first because different fungi respond to different products.
3. Grubs
What it looks like: Irregular brown areas, usually late summer to early fall, where the turf feels spongy. Birds, skunks or raccoons digging in the lawn are a strong clue.
How to confirm: Grab the brown grass and pull. If it rolls back like a loose carpet with few roots attached, look in the top inch or two of soil for white, C-shaped larvae. Cut a one-foot-square flap of turf in a few places and count what you find.
Fix: A few grubs per square foot is often tolerable. Larger numbers may justify treatment, timed to the life stage of the grubs in your area. Reseed or patch the damaged area once they are under control.
4. Chinch bugs
What it looks like: Yellowing patches that turn brown and spread outward in hot, sunny, dry areas. Very common in St. Augustine lawns, and also seen in other grasses. Easy to mistake for drought, but watering does not bring it back.
How to confirm: Look at the edge of the patch, where yellow grass meets green, and part the grass at soil level. Chinch bugs are tiny (a few millimeters) black insects with white wing markings. The classic test: push a can with both ends removed into the soil, fill it with water, and watch for bugs floating up.
Fix: Treat the active edge, not the dead center. Avoid over-fertilizing with fast-release nitrogen, which encourages them.
5. Dog urine
What it looks like: Small round spots, usually under a foot across, with a dead brown center and a ring of extra-green grass around it. The green ring comes from the nitrogen in urine, which acts like a heavy dose of fertilizer.
How to confirm: The pattern matches where your dog goes, and the grass pulls up with roots attached (unlike grubs).
Fix: Water the spot right after your dog uses it to dilute the nitrogen. Rake out dead grass and reseed.
6. Mower damage and scalping
What it looks like: Brown or white-tipped grass across the whole lawn after mowing, or scalped spots on high points and bumps.
How to confirm: Look at blade tips up close. A sharp blade makes a clean cut. A dull blade tears the grass and leaves ragged, frayed ends that brown within a day or two.
Fix: Sharpen the blade, raise the mowing height, and never remove more than one third of the blade length in a single mow.
Quick comparison
| Cause | Typical shape | Key test |
|---|---|---|
| Drought / dormancy | Large, irregular | Hard, dry soil; crowns still firm |
| Fungal disease | Circular, sometimes ringed | Lesions on individual blades |
| Grubs | Irregular, spongy | Turf rolls back; white C-shaped larvae |
| Chinch bugs | Spreading, in sunny spots | Bugs at the green-yellow edge |
| Dog urine | Small, round, green ring | Matches pet’s spot; roots intact |
| Mower damage | Whole lawn or high spots | Ragged, torn blade tips |
When in doubt, diagnose before you treat
If the patch does not clearly match one pattern, take a close-up photo of the blades at the edge of the patch and note the recent weather. Those two things narrow the list down faster than anything else.