Chinch Bugs vs. Fertilizer Burn in St. Augustine Grass

Sudden Brown Patches

New homeowner with established St. Augustine on sandy‑clay soil near water. Fertilized 3 weeks ago (minor burn). Now large brown patches, brown spots on blades. Neighbor suggests scalping.

Prime Suspect: Chinch Bugs

St. Augustine is the only warm‑season grass plagued by chinch bugs. Drought‑stressed turf attracts them. High nitrogen makes grass extra tasty. Damage appears 2 weeks after feeding begins—so it will look worse before improving.

Action Plan

1. Water deeply weekly (or more if needed); let dry between cycles.
2. STOP fertilizing.
3. DO NOT apply insecticide—it kills beneficial predators (big‑eyed bugs, earwigs, ants, nematodes).
4. Mow at 3″, cut to 2″; leave clippings.
5. Monitor: damage will seem to spread for ~2 weeks, then stall as predators catch up.

Healthy soil microbes break down thatch naturally; chemicals disrupt this cycle.