Brown Patches in St. Augustine: Sprinkler or Disease?

St. Augustine is the most common lawn grass in many neighborhoods north of Houston. It handles heat and some shade, but it browns for several different reasons. Adding water fixes some of them and makes others worse.

Sprinkler coverage problems

Signs: brown stripes along driveways and sidewalks, brown areas between heads, rings around a head, one zone browning as a whole.

Why: broken, buried or tilted heads, clogged nozzles, mismatched nozzles, heads spaced too far apart, low pressure on an overloaded zone.

Check: run the zone and watch. Do a can test. See how long to run sprinklers.

Fix: repair and match heads, clean nozzles, fix pressure.

Fungal disease

Signs: circular or irregular patches that can grow, often with a yellowish or orange edge, usually in spring and fall when nights are cool and the lawn stays wet. Leaf blades may pull easily from the runner.

Why: prolonged leaf wetness, overwatering, evening watering, poor drainage and heavy nitrogen at the wrong time.

Fix: water early in the morning only, cut back on water, improve drainage, avoid heavy fertilizer in cool wet weather. Fungicides help in some cases. The Texas A&M AgriLife Extension turf program has good guidance.

A brick house under very tall pines, with a shaded lawn and pine needles on the roof and beds — Shade and constant moisture under trees make St. Augustine more prone to fungus.

Chinch bugs

Signs: yellowing then browning patches in hot, dry weather, often starting in the sunniest spots near pavement. The patch spreads outward. Small insects at the soil line.

Why: chinch bugs feed on St. Augustine, especially stressed turf.

Fix: identify first, then treat according to label directions. Even watering helps reduce stress.

Grubs

Signs: turf that pulls up like a loose carpet because the roots are gone.

Fix: identify and treat as recommended.

Shade decline

Signs: thin, weak grass under trees that gets worse each year.

Why: too little light, often with too much water.

Fix: less water on shade zones, more light, or a different groundcover. See pine trees and sprinkler lines.

The common thread

Overwatering makes fungus and shade decline worse. Underwatering in hot spots invites chinch bugs. Even coverage and the right amount of water reduce all of these.