Crabgrass in St. Augustine and Centipede: Your Options Are Limited
The most important fact on this page: the standard crabgrass rescue product (quinclorac, sold as Drive XLR8 or as generic Quinclorac 75 DF and 1.5 L — will damage or kill St. Augustine and centipede lawns. Every lawn forum has posts from homeowners who grabbed a bottle of Drive, sprayed their St. Aug or centipede lawn, and destroyed it. The product works exactly as intended. It just isn’t labeled safe for your grass type, and the damage is real.
If you came here from the main crabgrass rescue article, you already saw the warning. This article is the full version of what your options actually are: what might work, what won’t, and what the most practical path forward looks like for most St. Augustine and centipede lawns with a crabgrass problem.
The short answer: for a serious infestation this season, accept some crabgrass, protect the lawn from further damage, and invest in pre-emergent prevention for next year. That’s not a satisfying answer, but it’s the honest one.
Why the Options Are So Limited
Most broadleaf herbicides are off the table for St. Augustine and centipede because both grasses are sensitive to many of the common active ingredients. Quinclorac is the clearest example, but the problem is broader: many combination products (weed and feed, combo concentrates) contain ingredients that are harmful to these grasses.
St. Augustine and centipede are also slow-recovering grasses. A chemical injury that a bermuda lawn shrugs off in two weeks can take a St. Augustine lawn most of the season to recover from. Or it doesn’t fully recover, leaving thin spots that the crabgrass (or something worse) colonizes the following year.
The risk-reward calculation changes when the “rescue” product has a meaningful chance of causing damage that’s harder to fix than the original weed problem.
What Might Work: Sethoxydim (Centipede Only)
Sethoxydim is a grass-specific herbicide. It kills actively growing annual and perennial grasses and is labeled for use over centipede turf. It’s sold as Segment II and under other names.
On centipede: Sethoxydim can control crabgrass, but results are slower and less reliable than quinclorac on tolerant grasses. It works best on small, actively growing crabgrass under warm conditions. Centipede is listed as tolerant, but “tolerant” in this context means it won’t be killed at label rates. It doesn’t mean zero visible stress. Apply in mild conditions, follow the label rate exactly, and don’t spray stressed centipede (drought-stressed, disease-stressed, or freshly scalped).
On St. Augustine: Sethoxydim is generally not recommended for St. Augustinegrass. The tolerance data is inconsistent and the label language varies. Do not apply sethoxydim to St. Augustine without reading the current specific product label carefully and confirming the listing. When in doubt, don’t.
Surfactant with sethoxydim: Like quinclorac, sethoxydim benefits from a surfactant (the labels specify the methylated seed oil type). The Segment II label specifies the adjuvant requirements. Follow them.
What Might Work: Fluazifop
Fluazifop (sold as Fusilade II and generics) is another grass-specific herbicide sometimes mentioned for crabgrass control in St. Augustine and centipede lawns.
The honest assessment: fluazifop’s label for use over St. Augustine and centipede as a primary use case is complicated, and label language changes. Before purchasing fluazifop for this purpose, read the current label for the specific product you’re buying and verify that your grass type is listed as tolerant. Do not rely on forum posts or older articles. Herbicide labels are legal documents and they get revised. The label you hold in your hand is the one that governs.
Even if labeled, fluazifop has similar limitations as sethoxydim: slower and less reliable than quinclorac on the grasses that tolerate it, and not a slam-dunk rescue on a heavy infestation.
What Works for Small Infestations: Hand-Pulling
For 10 or 20 individual crabgrass plants in a lawn that’s otherwise in reasonable shape, hand-pulling is genuinely the right answer. It’s not a satisfying solution, but it works, it costs nothing, and it causes no chemical risk to the lawn.
Pull the plants before they set seed: mid-summer, before the seedheads emerge in late summer. Get as much of the root system as you can, though crabgrass is an annual so the root doesn’t need to regrow from year to year. What matters is pulling before the plant drops seeds.
For a heavy, widespread infestation, hand-pulling isn’t realistic. That’s where you need to be honest with yourself about this year versus next year.
The Practical Path for Heavy Infestations: Accept and Prevent
If you have a significant crabgrass problem across a meaningful portion of your St. Augustine or centipede lawn, the most practical path is:
- Accept that you’re not going to kill all of it this season without risking real damage to the lawn.
- Protect the existing turf: mow at the right height, water appropriately, don’t stress it further.
- Run an aggressive pre-emergent program starting in late winter next year.
This isn’t giving up. It’s recognizing that the chemical options for St. Augustine and centipede are limited enough that the best ROI for your lawn is investing in prevention rather than chasing a rescue that may cause as many problems as it solves.
What Actually Works: Pre-Emergent Prevention
Pre-emergent herbicides prevent crabgrass seed from germinating. They don’t kill existing plants. They block the next generation. For St. Augustine and centipede owners, this is where the real leverage is.
Prodiamine is labeled safe for both St. Augustine and centipede at appropriate rates. Applied at the right time, before soil temperatures hit 55°F at the surface in late winter, prodiamine blocks the majority of the season’s crabgrass germination before it starts.
A split-rate prodiamine program in late winter, applied at soil-temp trigger timing, prevents 80 to 90% of the year’s crabgrass for roughly $5 to $15 in chemical per application on a home-sized lawn. That’s cheaper than any rescue option, and it doesn’t carry the risk of damaging the lawn.
Prevention Product Picks — 3 Tiers
These are pre-emergent options, not rescue. None of these kill crabgrass that’s already growing. They prevent next year’s generation from germinating.
Tier 1 — Cheapest (~$5–10 per application on 5,000 sq ft)
Quali-Pro Prodiamine 65 WDG or equivalent generic. Dry flowable, mixed with water in a tank sprayer. Rate for pre-emergent crabgrass prevention on St. Augustine and centipede: 0.37 oz per 1,000 sq ft. Apply when soil temperatures are approaching 50°F at the surface in late winter, before the 55°F germination trigger.
A 5 lb bag is a multi-year supply for most home lawns. Per-application cost for 5,000 sq ft is approximately $5 to $10 in chemical.
Tier 2 — Easy Measure (~$10–20 per application on 5,000 sq ft)
Generic Prodiamine 4 L liquid
The liquid formulation of prodiamine. Easier to measure for smaller lawns or spot treatments: fl oz marks, no scale. Application rate is roughly 0.5 fl oz per 1,000 sq ft at the standard pre-emergent rate. Slightly higher per-application cost than the dry flowable, but simpler to use.
Tier 3 — Combo Option (~$15–30 per application on 5,000 sq ft)
Dithiopyr (Dimension) 2EW liquid
Dithiopyr has a unique advantage: at early post-emergent timing (when crabgrass has just germinated, at the 1-tiller stage), it can kill crabgrass that has already emerged. This gives it a slightly wider window than prodiamine, which is strictly pre-emergent. Dithiopyr is labeled safe on St. Augustine and centipede.
The catch: dithiopyr’s post-emergent window is very early. It loses effectiveness quickly once plants reach 2 or more tillers. Think of it as prodiamine with a small post-emergent bonus, not a rescue product. It does not replace a true post-emergent rescue for established plants.
Rate and timing are on the label. Follow them. A quart bottle is a multi-season supply.
The Program That Actually Works
Late January to mid-February (soil temps approaching 50°F): Apply prodiamine at 0.37 oz per 1,000 sq ft. This is the primary prevention application.
Late April (optional split-rate): A second prodiamine application at the same rate extends the residual into summer and catches late-germinating crabgrass and goosegrass.
If a few plants escape: Hand-pull before they set seed. On centipede only, sethoxydim is an option for small escapes after confirming the label. Accept a handful of plants; don’t risk a wholesale herbicide application to the whole lawn chasing a few survivors.
Invest in lawn density year-round: Thick St. Augustine or centipede turf physically shades the soil and reduces crabgrass germination. Mow at the upper end of the recommended height range, fertilize on the right schedule for your grass type, and fill any thin or bare spots with sod plugs before crabgrass colonizes them. A thin lawn is a crabgrass nursery.
For More on These Grasses
- St. Augustinegrass guide — mowing heights, fertilizer timing, cultural practices that keep the lawn dense
- Centipedegrass guide — low-input management and why over-fertilizing centipede causes more problems than crabgrass
- Main crabgrass rescue article — identification, why pre-emergent is the real answer, and the options for tolerant grass types
Products Mentioned in This Article
- Quali-Pro Prodiamine 65 WDG, 5 lb — ~$80, years of pre-emergent — Amazon
- Dimension 2EW (dithiopyr), 64 oz — ~$142 — Amazon
- Monterey Grass Getter (sethoxydim) — ~$40 — Amazon
- MSO surfactant, 32 oz — ~$20 — Amazon
More retailer options will be added as we partner with additional suppliers.
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