Is It a Disease, a Pest, or Just Dry? Telling Them Apart

A brown area in a Florida lawn has four common explanations, they look broadly similar from a standing position, and the treatment for each makes the others worse.

1. Drought or irrigation coverage

Look for: a shape that follows the sprinkler pattern — a wedge, an arc, a strip along a driveway. Grass that is blue-grey before it browns. Footprints that stay visible after you walk across it, because the blades have lost turgor and do not spring back.

Confirm: run a catch-can test on that zone. If the containers there hold less than elsewhere, it is coverage.

2. Chinch bugs

Look for: damage starting in the hottest, driest part of the lawn — along a driveway, next to a south-facing wall — and expanding outward. Grass that does not respond to watering. Yellowing that turns to straw brown.

Confirm: part the grass at the edge of the damage, where green meets brown, and look at the soil surface. Chinch bugs are small and fast. Alternatively push a bottomless coffee can into the turf, fill it with water, and wait — they float.

This is the one most often watered instead of treated, and watering does not touch it.

3. Fungal disease

Look for: roughly circular patches rather than irregular ones. A darker or yellowish edge to the ring. Damage appearing after a period of humidity, heavy rain, or evening watering. Individual blades with lesions rather than being eaten.

Confirm: pull on affected blades. In brown patch the leaf sheath rots and blades pull away easily from the base, which is quite distinctive.

Fertilizing here makes it worse — soft, lush growth is exactly what the fungus wants.

4. Caterpillars — sod webworms and armyworms

Look for: grass that has been eaten rather than killed. Notched, ragged blade edges. A visible line advancing across the lawn. Small green pellets of frass at the soil surface. Moths flying up when you walk across the lawn at dusk.

Confirm: the soap flush — a couple of tablespoons of dish soap in a gallon or two of water poured over a square yard at the edge of the damage. Caterpillars surface within minutes.

Why getting it right matters

Water a chinch bug problem and it spreads. Fertilize a fungal problem and it accelerates. Treat for insects when the issue is coverage and you have spent money and changed nothing.

Ten minutes on hands and knees at the edge of the damage answers it. The edge is where the diagnosis is — the middle is already dead and tells you nothing.