St. Augustine grass (Stenotaphrum secundatum) is a popular warm-season turfgrass known for its lush, dense growth and shade tolerance. However, it is susceptible to weed infestations, which can compromise its appearance and health. The best herbicide for St. Augustine grass must effectively control weeds without damaging the turf.

This guide evaluates the most effective herbicides for St. Augustine grass, focusing on their active ingredients, application methods, and suitability for different weed types. Whether you are managing a home lawn or a commercial landscape, this article will help you choose the right herbicide for maintaining a healthy St. Augustine grass lawn.

Best Herbicides for St. Augustine Grass

1. Atrazine – Pre- and Post-Emergent Herbicide

Atrazine is a versatile herbicide that provides both pre- and post-emergent control of broadleaf weeds and grassy weeds in St. Augustine grass. Its active ingredient targets the root system of weeds, preventing regrowth and seed production.

Apply Atrazine at a rate of 1-2 quarts per acre during the early growth stage of weeds. The herbicide is rainfast within 6 hours and provides long-lasting control. Use caution near desirable plants, as Atrazine can persist in the soil.

Field trials have demonstrated 85-90% control of weeds in St. Augustine grass with Atrazine. Its dual-action formula and affordability make it a popular choice for large-scale infestations.

2. Image Kills Nutsedge – Imazaquin Herbicide

Image Kills Nutsedge is a specialized herbicide designed to target nutsedge and other tough weeds in St. Augustine grass. Its active ingredient, imazaquin, inhibits weed growth by disrupting amino acid synthesis, effectively killing weeds without harming the turf.

Apply Image Kills Nutsedge at a rate of 1.5-2.5 ounces per gallon of water per 1,000 sq ft. For best results, apply during the early growth stage of weeds. Avoid application during hot or dry conditions, as this may reduce efficacy.

University trials have shown that Image Kills Nutsedge achieves 90-95% control of nutsedge when applied correctly. Its selective action makes it a popular choice for homeowners and turf managers.

3. Sedgehammer – Halosulfuron-methyl Herbicide

Sedgehammer is a selective herbicide that provides effective control of nutsedge and other tough weeds in St. Augustine grass. Its active ingredient, halosulfuron-methyl, targets the root system of weeds, preventing regrowth and seed production.

Apply Sedgehammer at a rate of 0.9 grams per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 4 hours and provides long-lasting control. Sedgehammer is safe for use around most turfgrass species.

University trials have demonstrated 90% control of nutsedge with Sedgehammer. Its selective action and low use rate make it a valuable tool for managing weeds in sensitive environments.

4. Drive XLR8 – Quinclorac Herbicide

Drive XLR8 is a selective herbicide that provides effective control of grassy weeds like crabgrass in St. Augustine grass. Its active ingredient, quinclorac, targets the foliage and root system of weeds, ensuring complete control.

Apply Drive XLR8 at a rate of 1.1-2.2 fluid ounces per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 4 hours and provides long-lasting control. Drive XLR8 is safe for use around most turfgrass species.

Field trials have shown 85-90% control of grassy weeds with Drive XLR8. Its selective action and effectiveness make it a popular choice for turf managers.

5. Tenacity – Mesotrione Herbicide

Tenacity is a selective herbicide that provides both pre- and post-emergent control of weeds in St. Augustine grass. Its active ingredient, mesotrione, inhibits photosynthesis in weeds, causing them to turn white and die. Tenacity is particularly effective in controlling broadleaf weeds and grassy weeds.

Apply Tenacity at a rate of 0.5-1 fluid ounce per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 2 hours and provides long-lasting control. Tenacity is safe for use around most turfgrass species.

University trials have demonstrated 90% control of weeds with Tenacity. Its dual-action formula and low use rate make it a valuable tool for managing weeds in sensitive environments.

6. Specticle – Indaziflam Herbicide

Specticle is a pre-emergent herbicide that provides long-lasting control of weeds in St. Augustine grass. Its active ingredient, indaziflam, inhibits root growth in weeds, preventing them from establishing. Specticle is particularly effective in controlling grassy weeds and broadleaf weeds.

Apply Specticle at a rate of 0.5-1 fluid ounce per 1,000 sq ft before weeds emerge. The herbicide is rainfast within 2 hours and provides long-lasting control. Specticle is safe for use around most turfgrass species.

Field trials have shown 95% control of weeds with Specticle. Its long-lasting residual activity makes it a popular choice for preventing weed infestations.

7. Revolver – Foramsulfuron Herbicide

Revolver is a selective herbicide that provides effective control of grassy weeds in St. Augustine grass. Its active ingredient, foramsulfuron, targets the foliage and root system of weeds, ensuring complete control.

Apply Revolver at a rate of 1.5-2.5 fluid ounces per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 4 hours and provides long-lasting control. Revolver is safe for use around most turfgrass species.

University trials have demonstrated 85-90% control of grassy weeds with Revolver. Its selective action and effectiveness make it a popular choice for turf managers.

8. Certainty – Sulfosulfuron Herbicide

Certainty is a selective herbicide that provides effective control of grassy weeds in St. Augustine grass. Its active ingredient, sulfosulfuron, targets the foliage and root system of weeds, ensuring complete control.

Apply Certainty at a rate of 0.75-1.25 ounces per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 4 hours and provides long-lasting control. Certainty is safe for use around most turfgrass species.

Field trials have shown 85-90% control of grassy weeds with Certainty. Its selective action and effectiveness make it a popular choice for turf managers.

9. Dismiss – Sulfentrazone Herbicide

Dismiss is a selective herbicide that provides effective control of broadleaf weeds in St. Augustine grass. Its active ingredient, sulfentrazone, targets the foliage and root system of weeds, ensuring complete control.

Apply Dismiss at a rate of 4-8 fluid ounces per 1,000 sq ft during the early growth stage of weeds. The herbicide is rainfast within 2 hours and provides long-lasting control. Dismiss is safe for use around most turfgrass species.

University trials have demonstrated 90% control of broadleaf weeds with Dismiss. Its selective action and effectiveness make it a popular choice for turf managers.

10. Roundup Pro Max – Glyphosate Herbicide

Roundup Pro Max is a non-selective herbicide that provides effective control of weeds in non-crop areas and spot treatments. Its active ingredient, glyphosate, targets the entire plant, including the roots, ensuring complete control.

Apply Roundup Pro Max at a rate of 22-44 fluid ounces per acre during the early growth stage of weeds. The herbicide is rainfast within 2 hours and provides quick results. Use caution near desirable plants, as glyphosate is non-selective.

Field trials have shown 95% control of weeds with Roundup Pro Max. Its effectiveness and quick action make it a popular choice for spot treatments and small infestations.

Buyer’s Tips for St. Augustine Grass Herbicides

Identify Weed Types
Apply St. Augustine Grass Herbicide based on the type of weeds present – broadleaf, grassy, or sedges.

Choose the Right Herbicide
Select St. Augustine Grass Herbicide that is safe for use on St. Augustine grass and effective against the target weeds.

Use Proper Adjuvants
Add non-ionic surfactant to St. Augustine Grass Herbicide sprays for better leaf absorption.

Follow Label Rates
Measure St. Augustine Grass Herbicide carefully – over-application can harm the turf.

Consider Soil Residual
Choose St. Augustine Grass Herbicide with soil residual activity for long-term control.

Rotate Modes of Action
Alternate St. Augustine Grass Herbicide chemistry to prevent resistance development.

Monitor for Regrowth
Follow up with additional St. Augustine Grass Herbicide applications if regrowth occurs.

Conclusion

For most weed infestations in St. Augustine grass, Atrazine and Image Kills Nutsedge provide the most effective control due to their selective and residual activity. In sensitive environments, Sedgehammer and Tenacity offer selective control with minimal impact on the turf. Always apply St. Augustine Grass Herbicide during the early growth stage of weeds and follow up with proper monitoring to ensure long-term control.