Selective Herbicides Safe for St. Augustinegrass Lawns (2026 EPA Label Guide)
Agronomic Safety Summary for St. Augustinegrass
St. Augustinegrass requires specialized southern herbicides: Celsius WG (up to 95°F), Hi-Yield Atrazine (50°F–85°F), Certainty (Sulfosulfuron), SedgeHammer+, and Image (Imazaquin).
St. Augustine is highly sensitive to standard retail weed killers: NEVER broadcast Quinclorac (Drive XLR8), 2,4-D ester (SpeedZone), Triclopyr (TZone SE), or Fenoxaprop (Acclaim Extra), as they cause severe stolon necrosis.
1. Herbicides Labeled SAFE for Broadcast Application on St. Augustinegrass
| Brand Name & EPA Reg. | Active Ingredient & Group | Safe Temp Range (°F) | Surfactant & Mixing Notes | Where to Buy |
|---|---|---|---|---|
| SedgeHammer+ EPA Reg. 81880-24-10163 |
Halosulfuron-methyl 5% Group 2 (ALS Inhibitor / Sulfonylurea) |
60°F – 90°F Rainfast: 4h |
SedgeHammer+ single-scoop pouches already contain a built-in non-ionic surfactant. If using bulk SedgeHammer 75WG, add 2 tsp NIS per gallon. | Check Price at DoMyOwn View on Amazon |
| Celsius WG EPA Reg. 432-1507 |
Thiencarbazone-methyl 8.7%, Iodosulfuron-methyl-sodium 1.9%, Dicamba 57.4% Group 2 + Group 4 (ALS Inhibitors + Benzoic Acid Auxin) |
65°F – 95°F Rainfast: 4h |
Apply with Non-Ionic Surfactant (NIS) at 1 tsp per gallon of water. Specifically engineered not to stunt warm-season turf during summer heat up to 95°F. | Check Price at DoMyOwn View on Amazon |
| Certainty Turf Herbicide EPA Reg. 59639-138 |
Sulfosulfuron 75% Group 2 (ALS Inhibitor / Sulfonylurea) |
60°F – 90°F Rainfast: 3h |
Mandatory Non-Ionic Surfactant (NIS) at 1 tsp (0.25% v/v) per gallon of water. Frequently tank-mixed with Celsius WG for complete southern weed control. | Check Price at DoMyOwn View on Amazon |
| Image Kills Nutsedge EPA Reg. 228-719 |
Imazaquin 3.3% Group 2 (ALS Inhibitor / Imidazolinone) |
65°F – 90°F Rainfast: 6h |
Ready-to-mix liquid formulation contains surfactant; additional NIS is not required for standard broadcast or spot treatments. | Check Price at DoMyOwn View on Amazon |
| Hi-Yield Atrazine Weed Killer EPA Reg. 34911-15-7401 |
Atrazine 40.8% Group 5 (Photosystem II Inhibitor / Triazine) |
50°F – 85°F Rainfast: 6h |
Do NOT add surfactant when spraying actively growing St. Augustine or Centipede above 80°F to avoid foliar yellowing. Irrigate lightly within 48 hours for root uptake. | Check Price at DoMyOwn View on Amazon |
| Barricade 4FL (Prodiamine 65 WDG) EPA Reg. 100-1139 |
Prodiamine 40.7% (or 65% WDG) Group 3 (Microtubule Assembly Inhibitor / Dinitroaniline) |
45°F – 90°F Rainfast: 0h |
Pre-emergent soil barrier: do NOT use foliar surfactant. Must be watered in with 0.5 inches of irrigation or rainfall within 14 days of application to activate. | Check Price at DoMyOwn View on Amazon |
2. Conditional / Restricted Herbicides for St. Augustinegrass (Use With Caution)
| Herbicide | Active Ingredient | Restriction Status | Agronomic Note |
|---|---|---|---|
| Tenacity | Mesotrione 40% | SOD PRODUCTION ONLY | Always apply with Non-Ionic Surfactant (NIS) at 1 tsp (5 mL) per gallon of water for post-emergent applications. Causes temporary white bleaching on susceptible weeds and turf tips. |
3. Herbicides to AVOID on St. Augustinegrass (High Risk of Lawn Death)
Do Not Broadcast Spray These Active Ingredients on St. Augustinegrass
- Drive XLR8 (Quinclorac 18.92%): Labeled
AVOIDon St. Augustinegrass due to severe foliar chlorosis, stolon stunting, or permanent turf loss. - SpeedZone Lawn Weed Killer (2,4-D 28.57%, Mecoprop-p 5.88%, Dicamba 1.71%, Carfentrazone-ethyl 0.62%): Labeled
AVOIDon St. Augustinegrass due to severe foliar chlorosis, stolon stunting, or permanent turf loss. - TZone SE (Triclopyr 7.72%, 2,4-D 29.36%, Dicamba 2.22%, Sulfentrazone 0.66%): Labeled
AVOIDon St. Augustinegrass due to severe foliar chlorosis, stolon stunting, or permanent turf loss. - Acclaim Extra (Fenoxaprop-p-ethyl 6.59%): Labeled
AVOIDon St. Augustinegrass due to severe foliar chlorosis, stolon stunting, or permanent turf loss. - Pylex Herbicide (Topramezone 29.7%): Labeled
AVOIDon St. Augustinegrass due to severe foliar chlorosis, stolon stunting, or permanent turf loss.