Recovering from Herbicide Damage on St. Augustine Grass

Diagnosing Weed-and-Feed Injury

St. Augustine is sensitive to many broadleaf herbicides (especially 2,4-D and dicamba). Symptoms: browning, yellowing, stunting within days of application.

Three Common Causes

1. Product not labeled for St. Augustine: Check label—many say "Do not use on St. Augustine."
2. Over-application: Exceeding coverage rate (e.g., 5,000 sq ft bottle used on 2,000 sq ft).
3. High temperature volatility: Above 85°F, herbicides vaporize and damage non-target plants.

Immediate Recovery Steps

• Water heavily (1 inch daily for 3–5 days) to dilute chemical in root zone.
• Do not fertilize or apply more chemicals.
• Mow high (3.5–4 inches) to maximize photosynthesis.
• Wait 2–4 weeks. If crowns are alive, new growth will emerge.

When to Reseed or Resod

If no recovery after 4 weeks, or if roots are dead (tug test), remove dead sod and replant. Use the same variety for seamless blend.

Prevention for Future

Use spot-treatment with a St. Augustine-safe product (e.g., atrazine-based) or hand-pull weeds. Apply pre-emergent in February (e.g., prodiamine) to prevent weeds without post-emergent risk.