Warm-season grass
St. Augustine Grass: Brown Patches
Worried about brown patches on your St. Augustine grass lawn? Round, spreading, or random — what brown patches are telling you. This guide takes the general diagnosis and tunes it for St. Augustine grass — the signs to look for, what to do first, and how a warm-season lawn recovers — kept safety-first, with the product label as the final word.
What this means for St. Augustine grass
St. Augustine grass: The shade-tolerant choice for the Deep South and coast. As a warm-season grass at its peak in summer, when it browns or thins the cause is usually a specific pest, disease, or drought — not the grass simply giving out. Distinct patches, rather than even browning, usually mean one specific cause — fungus, grubs, chinch bugs, a pet, or fertilizer burn — and the shape and location are what narrow it down. Identifying the actual culprit is the whole game: fix that and a healthy stand normally bounces back. Worth knowing about St. Augustine grass generally: spreads quickly by stolons to fill in.
How to tell on a St. Augustine grass lawn
- Roughly circular patches that appear overnight in hot, humid weather point to fungal disease.
- Spongy patches that lift like loose carpet point to grubs chewing the roots.
- Spreading yellow-to-brown patches in the hottest, sunniest, driest spots point to chinch bugs.
- Small, sharply defined dead spots ringed by lush green point to dog urine or a spill.
- Straight brown or yellow striping in the pattern of your spreader passes, right after a feeding, points to fertilizer burn — water the area deeply to flush the excess salts past the roots.
What to do
- Step 1
Read the pattern before you treat
Note the shape (circular vs. irregular), where the patches are (shade and damp vs. hot and dry), and when they showed up. That pattern is most of the diagnosis — and it decides whether the answer is water, a pest treatment, a fungicide, or just reseeding a spot.
- Step 2
Rule out the easy causes first
Confirm it isn't simple drought (browns evenly, perks up with water), scalping (worst on bumps after mowing), or pet spots (small, sharp-edged) before assuming a pest or disease that needs a product.
- Step 3
Confirm the culprit, then treat the spot
Tug-test a patch edge for grubs, part the grass for chinch bugs, and look for the ring and timing of disease. Treat only what you've confirmed, and treat the affected area rather than the whole lawn.
Always read and follow the product label — it is the legal authority on rates, timing, and safety. These windows are regional estimates, not a prescription; defer to the label and your local extension office.
Not sure it's Brown Patches?
The same look on St. Augustine grass can have different causes. Answer a few quick questions in the free diagnosis tool and it narrows what your St. Augustine grass lawn is actually showing — and the fix for each — no signup required.
Diagnose my lawnHow St. Augustine grass recovers
St. Augustine grass spreads and self-repairs, so once the cause is handled, small thinned or damaged areas usually fill back in on their own with steady watering and time — you rarely need to reseed. One thing working in St. Augustine grass's favor: best shade tolerance of the warm-season grasses. Once the treatment matches the actual cause, the patch itself typically fills back in without needing a full reseed.
Safety first on St. Augustine grass
Several weed killers that are fine on other lawns will damage St. Augustine — confirm the label lists it by name before spraying. Keep nitrogen at or below ~1 lb per 1,000 sq ft per feeding. Treating the wrong cause is the real risk here — a fungicide on grub damage, or an insecticide on fertilizer burn, does nothing but adds cost and risk. And more generally, St. Augustine grass has this going for it: thrives in heat, humidity, and coastal conditions. Always read and follow the product label — it is the legal authority on rates, timing, and safety. These windows are regional estimates, not a prescription; defer to the label and your local extension office.
Preventing it next season
Water deeply in the early morning (not the late afternoon or evening), keep the mower blade sharp and the height up, and avoid heavy summer nitrogen — the conditions that prevent disease and stress are the same ones that grow a thick lawn.