Smooth & Large Crabgrass (Digitaria ischaemum / Digitaria sanguinalis): Identification & Selective Herbicide Matrix
Quick Agronomic Summary
Quinclorac (0.75 lb ai/A) and Mesotrione (5–8 fl oz/A) effectively eliminate post-emergent Crabgrass in cool-season turf when applied between 60°F and 85°F.
- Diagnostic Marker 1: Light apple-green coarse blades growing in a prostrate star-like rosette
- Diagnostic Marker 2: Membranous, tall jagged ligule with sparse hairs at the collar region
- Diagnostic Marker 3: Finger-like seedheads (3 to 5 spikes) emerging in mid-to-late summer
What herbicide kills Crabgrass without hurting lawn grass?
Quinclorac (0.75 lb ai/A) and Mesotrione (5–8 fl oz/A) effectively eliminate post-emergent Crabgrass in cool-season turf when applied between 60°F and 85°F.
For early 1–3 leaf stages and mature 2–4 tiller plants, Quinclorac paired with a methylated seed oil (MSO) surfactant provides rapid systemic control within 7 to 14 days. In St. Augustine and Centipede lawns where Quinclorac causes severe chlorosis, Atrazine or Mesotrione (for Centipede only) must be used instead.
When is the best time to spray Crabgrass?
Apply pre-emergent Prodiamine or Dithiopyr when 4-inch soil temperatures reach 50°F–55°F for three consecutive days, and spray post-emergent herbicides in late spring when seedlings have 2 to 3 leaves.
Post-emergent applications are most effective when Crabgrass is actively growing in moist soil and air temperatures remain below 85°F. Spraying mature multi-tiller plants in late August during drought stress significantly reduces herbicide translocation.
EPA-Registered Herbicides Labeled for Smooth & Large Crabgrass
The table below compares all selective herbicides in our database that control Smooth & Large Crabgrass, including active ingredient groups, application temperature limits (°F), and surfactant requirements.
| Brand Name & EPA Reg. | Active Ingredient & WSSA Group | Temp Window (°F) | Surfactant & Mixing Protocol | Where to Buy |
|---|---|---|---|---|
| Tenacity EPA Reg. 100-1267 |
Mesotrione 40% Group 27 (HPPD Inhibitor) |
55°F – 85°F Rainfast: 6h |
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. | Check Price at DoMyOwn View on Amazon |
| Drive XLR8 EPA Reg. 7969-272 |
Quinclorac 18.92% Group 4 (Synthetic Auxin / Quinoline Carboxylic Acid) |
60°F – 85°F Rainfast: 1h |
Requires Methylated Seed Oil (MSO) surfactant at 1.5 tbsp (0.75 fl oz) per gallon of water for effective cuticle penetration on multi-tiller crabgrass. | 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 |
| Acclaim Extra EPA Reg. 432-950 |
Fenoxaprop-p-ethyl 6.59% Group 1 (ACCase Inhibitor) |
60°F – 85°F Rainfast: 1h |
Add Non-Ionic Surfactant (NIS) at 0.5 tsp per gallon only when targeting mature multi-tiller Goosegrass or Japanese Stiltgrass. Never tank-mix with 2,4-D (causes antagonism). | Check Price at DoMyOwn View on Amazon |
| Pylex Herbicide EPA Reg. 7969-327 |
Topramezone 29.7% Group 27 (HPPD Inhibitor / Pyrazolone) |
55°F – 85°F Rainfast: 1h |
Must be applied with Methylated Seed Oil (MSO) at 1 to 1.5 tsp per gallon of water. Tank-mixing with Triclopyr Ester reduces white bleaching and speeds up Bermudagrass and Goosegrass mortality. | 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 |
Turfgrass Compatibility Matrix for Smooth & Large Crabgrass Herbicides
Always verify that your chosen herbicide is safe for your specific lawn grass before broadcast spraying:
| Herbicide | KBG | Tall Fescue | Ryegrass | Bermuda | St. Aug | Zoysia | Centipede | Bahia |
|---|---|---|---|---|---|---|---|---|
| Tenacity | SAFE | SAFE | SAFE | AVOID ACTIVELY GROWING | SOD PRODUCTION ONLY | DAMAGE RISK | SAFE | AVOID |
| Drive XLR8 | SAFE | SAFE | SAFE | SAFE | AVOID | SAFE | AVOID | AVOID |
| Hi-Yield Atrazine Weed Killer | AVOID | AVOID | AVOID | DORMANT ONLY | SAFE | SAFE | SAFE | AVOID |
| Acclaim Extra | SAFE | SAFE | SAFE | AVOID | AVOID | SAFE | AVOID | AVOID |
| Pylex Herbicide | SAFE | SAFE | SAFE | AVOID | AVOID | DAMAGE RISK | SAFE | AVOID |
| Barricade 4FL (Prodiamine 65 WDG) | SAFE | SAFE | SAFE | SAFE | SAFE | SAFE | SAFE | SAFE |
How to Distinguish Smooth & Large Crabgrass from Lookalike Weeds
| Lookalike Species | Key Botanical & Diagnostic Difference |
|---|---|
| Dallisgrass | Dallisgrass is a clumping perennial with black, caterpillar-like seedhead dots and no hairs at the auricles, whereas Crabgrass is an annual with finger-like smooth spikes. |
| Goosegrass | Goosegrass has a distinctive silvery-white flattened center core and zipper-like seedheads, thriving in heavily compacted soil. |