Crabgrass is one of the most common and frustrating summer annual weeds in St Augustine grass lawns. It germinates in spring when soil temperatures warm, spreads rapidly through seed, and dies at the first frost, leaving bare patches behind. Because St Augustine grass is sensitive to many herbicides, product selection matters more than in other turf species.
Choosing the best herbicide for crabgrass in St Augustine grass requires attention to crop safety, application timing, and whether the product is pre-emergent or post-emergent. Pre-emergent herbicides prevent crabgrass seed from germinating in spring, while post-emergent products kill existing plants after they emerge. Combining both approaches delivers the most reliable season-long control.
Some broadleaf herbicides that are safe on Bermuda grass and fescue will injure St Augustine grass, so labels must be checked carefully. The products in this guide are selected for their tolerance on St Augustine grass and their effectiveness on crabgrass at the labeled rate and stage.
In this guide, we review the best herbicides for crabgrass in St Augustine grass by examining pre-emergent and post-emergent options, application timing, and safe-use practices for long-term control.
Best Herbicide For Crabgrass In St Augustine Grass: Top 15 Options
1. Prodiamine 65 WDG Herbicide – Best Pre-Emergent Herbicide For Crabgrass In St Augustine Grass
Prodiamine 65 WDG Herbicide is the best pre-emergent herbicide for crabgrass in St Augustine grass because it forms a soil barrier that stops crabgrass seed from germinating without harming the turf. It is absorbed by emerging shoots and roots and disrupts cell division. It is highly effective when applied in early spring before soil temperatures reach 55 degrees Fahrenheit.
- Crabgrass Control
- Pre-emergent and broadleaf weed control
This prodiamine product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to four months of residual control from a single application. It does not control emerged crabgrass.
Because it is a Group 3 herbicide, it is a useful rotation partner with Group 1 and Group 15 products. Apply at the full labeled rate for consistent results.
- Prevents crabgrass germination
- Safe for St Augustine grass
- Long soil residual
- Reduces post-emergent applications
- Works in lawns and sports fields
- Different mode of action
- Trusted by turf managers
- No post-emergent activity
- Requires soil moisture
- Carryover risk in some rotations
2. Dithiopyr 2L Herbicide – Best Pre-Emergent Herbicide For Crabgrass In St Augustine Grass Lawns
Dithiopyr 2L Herbicide is the best pre-emergent herbicide for crabgrass in St Augustine grass lawns because it delivers both pre-emergent and early post-emergent activity on young crabgrass seedlings. It is absorbed by roots and shoots and disrupts cell division. It is highly effective when applied in early spring before crabgrass germinates.
- Effective Against: Annual grasses and broadleaf weeds
- Provides early post-emergent crabgrass control
This dithiopyr product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to four months of residual control and can kill very small crabgrass that has already emerged. It is not effective on mature crabgrass.
Because it is a Group 3 herbicide, it is a useful rotation partner with Group 1 and Group 15 products. Apply at the full labeled rate for consistent results.
- Pre and early post-emergent activity
- Safe for St Augustine grass
- Long soil residual
- Kills small emerged crabgrass
- Works in lawns and sports fields
- Different mode of action
- Trusted by turf managers
- Weak on mature crabgrass
- Requires soil moisture
- Carryover risk in some rotations
3. Atrazine 4L Herbicide – Best Herbicide For Crabgrass In St Augustine Grass And Centipede Grass
Atrazine 4L Herbicide is the best herbicide for crabgrass in St Augustine grass and centipede grass because it provides both pre-emergent and post-emergent activity on crabgrass and many broadleaf weeds. It is absorbed through roots and leaves and inhibits photosynthesis in susceptible plants. It is highly effective when applied in spring and early summer.
- Kills many broadleaf weeds
- Also used in centipede grass
This atrazine product is labeled for St Augustine grass, centipede grass, and some other warm-season turfgrasses and works best when applied before crabgrass germination or to young, actively growing plants. It has significant soil residual activity that keeps working for weeks after application. It is a restricted-use product in some states.
Because it is a Group 5 herbicide, it should be rotated with products from other groups to slow resistance. Apply according to the label for consistent results.
- Pre and post-emergent activity
- Safe for St Augustine grass
- Controls crabgrass and broadleaf weeds
- Long soil residual
- Reduces repeat applications
- Trusted by turf managers
- Different mode of action
- Restricted-use in some areas
- Groundwater concerns
- Long soil residual
4. Dimension 2EW Herbicide – Best Pre-Emergent Herbicide For Crabgrass In St Augustine Grass And Bermuda Grass
Dimension 2EW Herbicide is the best pre-emergent herbicide for crabgrass in St Augustine grass and Bermuda grass because it delivers consistent control across warm-season turf species. It is absorbed by emerging shoots and roots and disrupts cell division. It is highly effective when applied in early spring before crabgrass germinates.
- Dimension specialty herbicide is the only preemergence herbicide that offers excellent early postemergence control of crabgrass
- t offers exceptional turf and ornamental safety on both established cool- and warm-season turfgrasses, as well as on more than 440 ornamental plants.
This dithiopyr product is labeled for St Augustine grass, Bermuda grass, and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to four months of residual control and can kill small crabgrass that has emerged. It is not effective on mature plants.
Because it is a Group 3 herbicide, it is a useful rotation partner with Group 1 and Group 15 products. Apply at the full labeled rate for consistent results.
- Pre and early post-emergent activity
- Safe for St Augustine grass
- Long soil residual
- Kills small emerged crabgrass
- Works in lawns and sports fields
- Different mode of action
- Trusted by turf managers
- Weak on mature crabgrass
- Requires soil moisture
- Carryover risk in some rotations
5. Pendulum 2G Herbicide – Best Granular Pre-Emergent Herbicide For Crabgrass In St Augustine Grass
Pendulum 2G Herbicide is the best granular pre-emergent herbicide for crabgrass in St Augustine grass because it delivers consistent control through a spreader application. It contains pendimethalin and is absorbed by emerging shoots and roots. It is highly effective when applied in early spring before crabgrass germinates.
- Delivers unbeatable overall preemergent control of troublesome weeds, including crabgrass, goosegrass, oxalis, henbit, spurge and nearly 40 other broadleaf and grassy species.
- Controls weeds as they germinate.
This pendimethalin product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to four months of residual control and is easy to apply with a broadcast spreader. It does not control emerged crabgrass.
Because it is a Group 3 herbicide, it is a useful rotation partner with Group 1 and Group 15 products. Apply at the full labeled rate for consistent results.
- Granular formula
- Safe for St Augustine grass
- Long soil residual
- Easy to apply
- Reduces post-emergent applications
- Different mode of action
- Trusted by turf managers
- No post-emergent activity
- Requires soil moisture
- Carryover risk in some rotations
6. Barricade 4FL Herbicide – Best Liquid Pre-Emergent Herbicide For Crabgrass In St Augustine Grass
Barricade 4FL Herbicide is the best liquid pre-emergent herbicide for crabgrass in St Augustine grass because it delivers consistent control through a sprayable formula. It contains prodiamine and is absorbed by emerging shoots and roots. It is highly effective when applied in early spring before crabgrass germinates.
- PREVENT WEED DEVELOPMENT: Barricade 4FL controls the growth and development of weeds before they germinate. Barricade 4FL will not control weeds after they have germinated. This product is labeled for use in a broad range of areas such as vegetation sites, turf species, weed control, grass, broadleaf weeds, established turfgrasses, lawns, sod nurseries, and Christmas tree farms.
- LONG-LASTING PREEMERGENCE WEED PREVENTION: Take action before unsightly vegetation infiltrates your landscaped lawn with our pre-emergent concentrate. One application can prevent weeds season long when used as directed. You can apply this selective weed spray solution several months before germination and expect it to work well into the peak season.
This prodiamine product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to four months of residual control and is easy to apply with a backpack or boom sprayer. It does not control emerged crabgrass.
Because it is a Group 3 herbicide, it is a useful rotation partner with Group 1 and Group 15 products. Apply at the full labeled rate for consistent results.
- Liquid formula
- Safe for St Augustine grass
- Long soil residual
- Uniform coverage
- Reduces post-emergent applications
- Different mode of action
- Trusted by turf managers
- No post-emergent activity
- Requires soil moisture
- Carryover risk in some rotations
7. MSMA Herbicide – Best Post-Emergent Herbicide For Crabgrass In St Augustine Grass
MSMA Herbicide is the best post-emergent herbicide for crabgrass in St Augustine grass because it selectively kills emerged crabgrass without harming the turf when applied at the labeled rate. It is absorbed through leaves and translocated to growing points. It is highly effective on young crabgrass in warm-season turf.
- Monosodium acid Methanearsonate MSMA 48.3%
- MSMA can be used on Cotton, Golf courses, Sod Farms, and highway rights of way for weed control.
This MSMA product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to young, actively growing crabgrass before it tillers. It requires good spray coverage for effective control. It is restricted in some states and may not be available in all areas.
Because it is a Group 17 herbicide, it should be rotated with products from other groups to slow resistance. Apply according to the label for consistent results.
- Post-emergent crabgrass control
- Safe for St Augustine grass
- Fast-acting formula
- Absorbed and translocated
- Effective on young weeds
- Trusted by turf managers
- Widely used in southern turf
- Restricted in some states
- Requires good coverage
- Best on small weeds only
8. Quinclorac 75 DF Herbicide – Best Selective Post-Emergent Herbicide For Crabgrass In St Augustine Grass
Quinclorac 75 DF Herbicide is the best selective post-emergent herbicide for crabgrass in St Augustine grass because it controls emerged crabgrass without harming the turf when applied according to the label. It is absorbed through leaves and roots and disrupts cell division. It is highly effective on young crabgrass in warm-season turf.
- Water-Based Formulation: Experience the power of our unique water-based formulation that ensures superior control and faster plant uptake, delivering results you can see quickly
- Extended Residual Control: Enjoy up to 30 days of residual control, keeping your turfgrass free from troublesome weeds for longer periods and reducing the need for frequent applications; Rainfast in less than an hour
This quinclorac product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to young, actively growing crabgrass before it tillers. It requires a surfactant for best absorption and works well in tank mixes with other herbicides. It is not effective on mature crabgrass.
Because it is a Group 4 herbicide, it is a useful rotation partner with Group 3 and Group 17 products. Apply at the full labeled rate for consistent results.
- Post-emergent crabgrass control
- Safe for St Augustine grass
- Absorbed through leaves and roots
- Tank-mix flexibility
- Different mode of action
- Trusted by turf managers
- Widely used in southern turf
- Weak on mature crabgrass
- Requires surfactant
- Some soil residual
9. Drive XLR8 Herbicide – Best Fast-Acting Post-Emergent Herbicide For Crabgrass In St Augustine Grass
Drive XLR8 Herbicide is the best fast-acting post-emergent herbicide for crabgrass in St Augustine grass because it delivers visible results within days of application. It contains quinclorac and is absorbed through leaves and roots. It is highly effective on young crabgrass in warm-season turf.
- Water-Based Formulation: Experience the power of our unique water-based formulation that ensures superior control and faster plant uptake, delivering results you can see quickly
- Extended Residual Control: Enjoy up to 30 days of residual control, keeping your turfgrass free from troublesome weeds for longer periods and reducing the need for frequent applications; Rainfast in less than an hour
This quinclorac product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to young, actively growing crabgrass before it tillers. It requires a methylated seed oil surfactant for best absorption and works well in tank mixes. It is not effective on mature crabgrass.
Because it is a Group 4 herbicide, it is a useful rotation partner with Group 3 and Group 17 products. Apply at the full labeled rate for consistent results.
- Fast-acting formula
- Safe for St Augustine grass
- Absorbed through leaves and roots
- Visible results in days
- Different mode of action
- Trusted by turf managers
- Widely used in southern turf
- Weak on mature crabgrass
- Requires MSO surfactant
- Some soil residual
10. Sedgehammer Herbicide – Best Herbicide For Crabgrass In St Augustine Grass And Nutsedge
Sedgehammer Herbicide is the best herbicide for crabgrass in St Augustine grass and nutsedge because it controls both weed types without harming the turf. It contains halosulfuron and is absorbed through leaves and roots. It is highly effective on yellow nutsedge and provides suppression of crabgrass in warm-season turf.
- ELITE WEED DEFENSE - Sedgehammer + offers unparalleled defense against nutsedge & up to 25 additional challenging weeds. Crafted for the discerning homeowner for small-scale use, this nutsedge weed killer quickly transforms your landscape into a verdant sanctuary
- PROUDLY MADE WITHOUT COMPROMISE- Sedgehammer herbicides, embodying the pinnacle of premium quality that every yard deserves
This halosulfuron product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to actively growing weeds. It requires a non-ionic surfactant for best absorption and controls a broad spectrum of sedges. It provides suppression, not full control, of crabgrass.
Because it is a Group 2 herbicide, it is a useful rotation partner with Group 3 and Group 4 products. Apply at the full labeled rate for consistent results.
- Controls nutsedge and crabgrass
- Safe for St Augustine grass
- Absorbed and translocated
- Different mode of action
- Widely available
- Trusted by turf managers
- Works in lawns and sports fields
- Suppression only for crabgrass
- Requires surfactant
- Some soil residual
11. Celsius WG Herbicide – Best Herbicide For Crabgrass And Broadleaf Weeds In St Augustine Grass
Celsius WG Herbicide is the best herbicide for crabgrass and broadleaf weeds in St Augustine grass because it controls both weed types without harming the turf. It contains a combination of active ingredients and is absorbed through leaves and roots. It is highly effective on crabgrass, clover, and dollarweed in warm-season turf.
- Date stamped on packaging is the Manufacturing Date, NOT an expiration date.
This combination product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to young, actively growing weeds. It controls a broad spectrum of broadleaf weeds and provides suppression of crabgrass. It requires a surfactant for best absorption.
Because it contains two modes of action, it slows resistance and broadens the weed spectrum. Apply according to the label for consistent results.
- Controls crabgrass and broadleaf weeds
- Safe for St Augustine grass
- Multiple modes of action
- Tank-mix flexibility
- Different mode of action
- Trusted by turf managers
- Widely used in southern turf
- Suppression only for mature crabgrass
- Requires surfactant
- Some soil residual
12. Blindside Herbicide – Best Herbicide For Crabgrass And Sedges In St Augustine Grass
Blindside Herbicide is the best herbicide for crabgrass and sedges in St Augustine grass because it controls both weed types through a single application. It contains a combination of active ingredients and is absorbed through leaves and roots. It is highly effective on crabgrass, kyllinga, and nutsedge in warm-season turf.
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This combination product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to actively growing weeds. It controls a broad spectrum of broadleaf weeds, sedges, and provides suppression of crabgrass. It requires a surfactant for best absorption.
Because it contains two modes of action, it slows resistance and broadens the weed spectrum. Apply according to the label for consistent results.
- Controls crabgrass and sedges
- Safe for St Augustine grass
- Multiple modes of action
- Tank-mix flexibility
- Different mode of action
- Trusted by turf managers
- Widely used in southern turf
- Suppression only for mature crabgrass
- Requires surfactant
- Some soil residual
13. Solitare Herbicide – Best Herbicide For Crabgrass And Broadleaf Weeds In St Augustine Grass Lawns
Solitare Herbicide is the best herbicide for crabgrass and broadleaf weeds in St Augustine grass lawns because it combines two modes of action for broad-spectrum control. It is absorbed through leaves and roots and controls crabgrass, clover, and dollarweed. It is highly effective when applied to young, actively growing weeds.
- Kills most varieties of crabgrass
- Visible results in as little as two days
This combination product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to young, actively growing weeds. It controls a broad spectrum of broadleaf weeds and provides suppression of crabgrass. It requires a surfactant for best absorption.
Because it contains two modes of action, it slows resistance and broadens the weed spectrum. Apply according to the label for consistent results.
- Controls crabgrass and broadleaf weeds
- Safe for St Augustine grass
- Multiple modes of action
- Tank-mix flexibility
- Different mode of action
- Trusted by turf managers
- Widely used in southern turf
- Suppression only for mature crabgrass
- Requires surfactant
- Some soil residual
14. Certainty Herbicide – Best Herbicide For Crabgrass And Kyllinga In St Augustine Grass
Certainty Herbicide is the best herbicide for crabgrass and kyllinga in St Augustine grass because it controls both weed types without harming the turf. It contains sulfosulfuron and is absorbed through leaves and roots. It is highly effective on kyllinga, nutsedge, and provides suppression of crabgrass in warm-season turf.
- Certainty Turf Herbicide is a selective, post-emergent herbicide that controls labeled weeds in residential and commercial turf.
- Combined with a non-ionic surfactant, Certainty Turf Herbicide attacks nutsedge through broadcast applications or spot treatments.
This sulfosulfuron product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied to actively growing weeds. It controls a broad spectrum of sedges and provides suppression of crabgrass. It requires a surfactant for best absorption.
Because it is a Group 2 herbicide, it is a useful rotation partner with Group 3 and Group 4 products. Apply at the full labeled rate for consistent results.
- Controls kyllinga and crabgrass
- Safe for St Augustine grass
- Absorbed and translocated
- Different mode of action
- Widely available
- Trusted by turf managers
- Works in lawns and sports fields
- Suppression only for crabgrass
- Requires surfactant
- Some soil residual
15. Specticle Flo Herbicide – Best Long-Residual Herbicide For Crabgrass In St Augustine Grass
Specticle Flo Herbicide is the best long-residual herbicide for crabgrass in St Augustine grass because it prevents crabgrass germination for up to eight months with a single application. It contains indaziflam and is absorbed by emerging shoots and roots. It is highly effective when applied in early spring before crabgrass germinates.
- Use with most pesticides to improve results
This indaziflam product is labeled for St Augustine grass and other warm-season turfgrasses and works best when applied before crabgrass germination with adequate soil moisture. It provides up to eight months of residual control, the longest of any pre-emergent on the market. It does not control emerged crabgrass.
Because it is a Group 29 herbicide, it is a useful rotation partner with Group 3 and Group 15 products. Apply at the full labeled rate for consistent results.
- Longest soil residual
- Safe for St Augustine grass
- Prevents crabgrass germination
- Reduces repeat applications
- Low use rates
- Different mode of action
- Trusted by turf managers
- No post-emergent activity
- Requires soil moisture
- Carryover risk in some rotations
7 Tips For Controlling Crabgrass In St Augustine Grass
- Apply pre-emergent in early spring: Prodiamine, dithiopyr, and pendimethalin work best when applied before soil temperatures reach 55 degrees Fahrenheit and crabgrass begins to germinate.
- Time post-emergent applications to young weeds: Quinclorac and MSMA work best on young crabgrass before it tillers. Mature plants are difficult to control.
- Check the label for St Augustine grass tolerance: Some herbicides safe on Bermuda grass will injure St Augustine grass. Always confirm turf tolerance before spraying.
- Water in pre-emergent herbicides: Prodiamine, dithiopyr, and pendimethalin need moisture to activate and form an effective soil barrier.
- Mow at the correct height: St Augustine grass should be mowed at 3 to 4 inches to shade the soil and reduce crabgrass germination.
- Fertilize and water properly: A thick, healthy lawn naturally outcompetes crabgrass. Maintain fertility and irrigation for best results.
- Rotate modes of action: Using the same herbicide group repeatedly selects for resistant weeds. Rotate between Group 2, Group 3, Group 4, Group 5, and Group 29 products.
Best Herbicide For Crabgrass In St Augustine Grass Frequently Asked Questions
1. What is the best herbicide for crabgrass in St Augustine grass?
Prodiamine 65 WDG Herbicide is the best pre-emergent herbicide for crabgrass in St Augustine grass because it prevents germination for up to four months without harming the turf. Quinclorac 75 DF Herbicide is the best post-emergent option for emerged crabgrass.
2. Will 2,4-D kill crabgrass in St Augustine grass?
No, 2,4-D does not control crabgrass because it is a broadleaf herbicide. Crabgrass is a grass species and requires grass-selective herbicides like quinclorac or pre-emergent products like prodiamine.
3. When should I apply pre-emergent for crabgrass in St Augustine grass?
Apply pre-emergent herbicide in early spring when soil temperatures are approaching 55 degrees Fahrenheit, before crabgrass seed germinates. In southern states, this is usually between late February and mid-March.
4. What kills crabgrass in St Augustine grass without harming the turf?
Quinclorac 75 DF Herbicide and MSMA Herbicide control emerged crabgrass without harming St Augustine grass when applied according to the label. Prodiamine and dithiopyr prevent germination without harming the turf.
5. Does crabgrass come back after spraying?
Crabgrass can regrow from the seed bank after post-emergent treatment. Pre-emergent herbicides and improved turf density help prevent regrowth the following season.
6. Can I use Roundup on crabgrass in St Augustine grass?
No, Roundup is non-selective and will kill St Augustine grass along with the crabgrass. Use selective herbicides labeled for St Augustine grass instead.
7. What is the best time to kill crabgrass in St Augustine grass?
The best time to kill crabgrass is in early summer when plants are young and actively growing. Pre-emergent products go down in early spring before germination for the most reliable season-long control.
Conclusion
Prodiamine 65 WDG Herbicide is the best pre-emergent herbicide for crabgrass in St Augustine grass because it prevents germination for up to four months without harming the turf. Dithiopyr 2L Herbicide, Atrazine 4L Herbicide, Dimension 2EW Herbicide, and Pendulum 2G Herbicide follow closely as proven options for early-season control.
For post-emergent control, MSMA Herbicide, Quinclorac 75 DF Herbicide, and Drive XLR8 Herbicide deliver reliable results on young crabgrass. Sedgehammer Herbicide, Celsius WG Herbicide, Blindside Herbicide, Solitare Herbicide, and Certainty Herbicide provide dual-purpose control on crabgrass and other warm-season weeds. Specticle Flo Herbicide delivers the longest residual pre-emergent control on the market.
Effective crabgrass control in St Augustine grass requires matching the product to the timing, checking turf tolerance on the label, and combining pre-emergent and post-emergent treatments. Rotating modes of action prevents resistance and keeps products effective over time.
Start your crabgrass control program this spring, choose the right product for your lawn, and plan for follow-up treatments each year. Consistent effort delivers a clean St Augustine lawn and long-term control.