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Grassy Weed · Perennial · Southern & Transition Zone

Dallisgrass Control Guide

Paspalum dilatatum

Dallisgrass is the southern lawn weed that lawn-care veterans remember controlling easily with MSMA — and that newer homeowners struggle with because MSMA has been off the residential market since 2013. Modern control is harder, more species-dependent, and varies dramatically by what kind of lawn you have. Bermuda and zoysia lawns have selective options; St. Augustine and cool-season lawns essentially don't. Knowing your lawn species determines what works.

Mature dallisgrass clump growing through a southern bermuda grass lawn, the coarse upright weed standing visibly taller than surrounding short bermuda turf
Dallisgrass clump in a southern bermuda lawn — coarse upright growth from a central crown, standing visibly taller than the surrounding turf.
Anton Schwarz, Resident Lawn Types Expert

★ Author

Anton Schwarz, Resident Lawn Types Expert

"June 11th, 2024, I walked a TifTuf bermuda lawn in Fort Worth where the homeowner had been spot-spraying glyphosate on dallisgrass clumps for three years and ending up with dead bermuda rings around each clump. He didn\'t know about Revolver Q (foramsulfuron) — which is selective in bermuda and kills dallisgrass without damaging the surrounding turf. We applied it to twelve clumps on June 18th. Three weeks later all twelve were dead, the bermuda was intact, and the lawn looked uniform for the first time in years. The right product exists for warm-season lawns. The wrong assumption that glyphosate is the only option costs years of damaged turf."

Quick Stats

Control difficulty:
Very Hard
Primary control:
Glyphosate spot-treatment for cool-season; foramsulfuron (Revolver) or sulfentrazone-based options for bermuda/zoysia
Secondary control:
Pre-emergent (indaziflam) for seedling prevention
Time to control:
14-21 days visible decline; 28-42 days for full clump kill
Two-year kill rate:
60-80% with one spring + one fall application over 2 years; reseed bare spots

How to Identify Dallisgrass

Macro close-up of a dallisgrass seed head showing the alternating spike-like racemes on a tall central stalk with characteristic black-haired seeds
Dallisgrass seed head ID: 3-7 spike-like racemes alternating along a central stalk, with characteristic black hairs on the seeds — diagnostic when viewed up close.

Dallisgrass has three signature features that separate it from crabgrass, quackgrass, and other look-alikes:

  • Tall coarse upright clumps growing 12-30 inches if unmowed, from a distinct central crown. Even at typical mowing heights (2-3 inches), the clumps stand visibly taller than surrounding turf with coarser blade texture. Blade color is medium green, slightly lighter than mature bermuda or zoysia.
  • Distinctive seed head with 3-7 spike-like racemes alternating along a central stalk, rising 24-60 inches above the foliage. The individual seeds have characteristic black hairs — diagnostic feature when viewed up close. Seed heads emerge throughout summer (June-September) and require frequent mowing to suppress.
  • Thick fibrous root crown — pull a mature dallisgrass clump and you\'ll find a dense, knotted base 2-4 inches across at soil surface. The crown is the species\' overwintering structure and the target for any effective control program.

Growth pattern: dallisgrass spreads primarily by seed (each plant produces 1,500-3,000 seeds per season) and secondarily by short rhizomes that extend the crown laterally 6-12 inches per year. Mature clumps form expanding circles that crowd out desirable turf and produce visible non-uniformity in the lawn. The species tolerates close mowing well — it survives golf course rough management at 1.5-2 inch heights — and is one of the most heat-tolerant grassy weeds in the South.

The MSMA Era and What Replaced It

From the 1960s through 2013, MSMA (monosodium methanearsonate) was the standard dallisgrass control across the Southeast and southern transition zone. MSMA was a selective post-emergent that killed dallisgrass in bermuda and zoysia lawns at rates the desirable warm-season grasses tolerated. A homeowner could buy MSMA at most southern garden centers, spot-spray dallisgrass clumps two or three times per summer, and achieve excellent control.

EPA phased out MSMA from residential use in 2013 due to arsenic contamination concerns — the active ingredient is an organic arsenical that breaks down to inorganic arsenic in soil and water. Limited use continued for golf courses and sod farms under restricted-use registration in some states, but homeowner-grade MSMA disappeared from retail shelves.

Modern replacements depend heavily on the lawn species:

  • Bermuda and zoysia lawns: foramsulfuron (Revolver Q) is the closest functional replacement. Selective post-emergent that kills dallisgrass without damaging bermuda or most zoysia cultivars. Sulfentrazone-containing combinations (Echelon) and fluazifop (Fusilade II, where labeled) are secondary options.
  • St. Augustine lawns: no selective option works without damaging St. Augustine. Glyphosate spot-treatment with plug-replanting is the protocol.
  • Centipede lawns: very limited options; primarily glyphosate spot-treatment.
  • Cool-season lawns (KBG, tall fescue, fine fescue, perennial ryegrass): no selective option. Glyphosate spot-treatment plus fall reseeding.

The Bermuda / Zoysia Protocol

For bermuda and zoysia lawns, the modern dallisgrass control program:

  1. Identification confirmed: verify the weed is dallisgrass (not crabgrass, not quackgrass, not nimblewill). Misidentification leads to product mismatch.
  2. Spring spot-treatment with foramsulfuron (Revolver Q): apply between May 1 and June 30 when dallisgrass is actively growing and air temperatures are 70-90°F. Spot-spray each clump to wet leaf coverage. Add non-ionic surfactant per label.
  3. Second application 21-28 days later: treat any surviving clumps and any new seedlings that emerged after the first treatment.
  4. Late-winter pre-emergent (February-March): apply indaziflam (Specticle FLO) at the label rate to prevent germination of seedbank seedlings the next spring. Indaziflam provides longer residual control than prodiamine or pendimethalin.
  5. Repeat next season: dallisgrass eradication is a 2-3 year program. Expect 60-80% reduction year 1, additional 20-30% year 2, near-clean appearance by year 3.

Cost: Revolver Q is professional-grade and runs $80-150 per acre-treatment equivalent. For typical residential lawns with 5-20 dallisgrass clumps, expect total seasonal cost of $40-100 plus pre-emergent.

The St. Augustine and Cool-Season Reality

For St. Augustine, centipede, and cool-season lawns, dallisgrass control becomes a surgical glyphosate operation:

  • Foam wand applicator (Smucker QuickWipe or similar) loaded with 41% glyphosate. Apply directly to dallisgrass leaves with minimal contact to surrounding turf.
  • Glove-of-death technique: chemical-resistant glove over cotton glove, dipped in glyphosate solution, wiped onto each dallisgrass leaf. Maximum precision; tedious for many clumps.
  • Cardboard shield with pump sprayer: shield surrounding desirable turf, spray clump directly.

Accept that a 3-6 inch ring of surrounding turf will die with each treatment. For St. Augustine lawns, plug-replant the bare spots with St. Augustine plugs in the same growing season. For cool-season lawns, reseed the kill spots in September during the fall overseeding window.

Why Dallisgrass Keeps Coming Back

Three reasons account for chronic dallisgrass recurrence:

  • Soil seedbank: dallisgrass seed persists 4-7 years in soil. Even after killing all visible plants, new seedlings emerge for multiple seasons.
  • Continuous introduction: dallisgrass seed disperses via wind, water runoff, mower equipment, and contaminated mulch/topsoil. New introductions occur even after eradication of existing populations.
  • Incomplete kill: the thick fibrous crown survives single-application herbicide treatments. Multi-application programs (2-3 treatments per season) are necessary for true crown kill.

Combined with pre-emergent application and competitive turf management (proper bermuda or zoysia care to maintain canopy density), the multi-year program transitions a heavily infested lawn to clean appearance within 2-3 seasons.

Frequently Asked Questions

Why is dallisgrass so hard to kill?

Three reasons. (1) It's a perennial with a thick fibrous root crown that survives most contact herbicides — only translocated herbicides reach the crown for true kill. (2) It produces seed prolifically from tall seed heads (24-60 inches) that mowing partially but not fully removes. (3) The historical control product (MSMA) was withdrawn from residential use by EPA in 2013, leaving only marginal selective options for cool-season lawns. Warm-season lawns have better options (foramsulfuron, sulfentrazone-based combinations), but residential cool-season lawns rely on glyphosate spot-treatment.

How do I tell dallisgrass from crabgrass?

Three differences. (1) Lifecycle: dallisgrass is a perennial that returns from the same crown each year; crabgrass is a summer annual that dies in fall and regrows from seed each spring. (2) Growth pattern: dallisgrass forms tall coarse clumps (12-30 inches if unmowed) with a distinct central crown; crabgrass spreads in low flat mats with stems radiating outward. (3) Seed head: dallisgrass produces 3-7 spike-like racemes alternating on a central stalk, with characteristic black hairs on the seeds; crabgrass produces 3-7 finger-like radiating spikes from a central point with no hairs. The two get confused because both are unwelcome warm-weather grassy weeds in southern lawns.

What killed dallisgrass before MSMA was banned?

MSMA (monosodium methanearsonate) was the standard dallisgrass control from the 1960s through 2013. It was an organic arsenical that selectively killed dallisgrass in bermuda and zoysia lawns at rates the desirable grass tolerated. The EPA phased out MSMA from residential use in 2013 due to arsenic contamination concerns in soil and water. Limited commercial/golf course use remains under restricted-use registration in some states. Residential homeowners have not been able to legally purchase MSMA since 2013. The product is sometimes mentioned in older lawn-care books and online forums — those recommendations are obsolete.

My bermuda lawn is full of dallisgrass. What's the modern protocol?

For bermuda and zoysia lawns, three product options. (1) Foramsulfuron (Revolver Q) — most effective selective post-emergent for dallisgrass in warm-season turf. Professional-grade product, sometimes available to homeowners through agricultural suppliers. (2) Sulfentrazone + prodiamine (Echelon or similar) — provides post-emergent dallisgrass suppression plus pre-emergent seed prevention. (3) Sequential applications of fluazifop (Fusilade II) — labeled for some warm-season lawns; check tolerance for your specific cultivar. Combined with pre-emergent (indaziflam, Specticle FLO) the following spring, these programs achieve 70-85% control over 2 years.

My St. Augustine lawn has dallisgrass. What works?

St. Augustine lawns have the fewest options because most selective grassy-weed herbicides damage St. Augustine. The realistic protocol: glyphosate spot-treatment using a foam wand applicator, treating each dallisgrass clump individually. Accept that a small ring of surrounding St. Augustine will die — plug-replant the bare spots with St. Augustine plugs in the next growing season. Some homeowners use a 0.5% glyphosate solution applied with a glove-of-death technique (chemical-resistant glove over cotton glove, dipped in solution, wiped directly on dallisgrass leaves) for surgical precision. There is no labeled selective product that reliably kills dallisgrass in St. Augustine.

My cool-season (KBG, tall fescue, fine fescue) lawn has dallisgrass. What works?

Cool-season lawns have similar limited options to St. Augustine — most selective grassy-weed herbicides damage desirable cool-season turf. Protocol: glyphosate spot-treatment in late summer (August-September), reseeding the kill spots in September with the appropriate cool-season grass. Use a foam wand applicator for precision. Dallisgrass is less common in cool-season lawns north of Zone 7 because the species is cold-sensitive — most cool-season dallisgrass problems are in the transition zone (Zone 6b-7b).

Will pre-emergent prevent dallisgrass?

Yes for new seedlings; no for existing established plants. Pre-emergent herbicides (prodiamine, dithiopyr, pendimethalin, indaziflam) prevent dallisgrass seed germination but have zero effect on plants already established from previous seasons. For lawns where you've killed established clumps and want to prevent reinfestation from the soil seedbank, apply pre-emergent in late winter (February-March in Zones 7-9) timed to soil temperatures reaching 55°F. Indaziflam (Specticle FLO) provides longer residual control than older pre-emergents and is the current professional standard for chronic dallisgrass pressure.

Is dallisgrass spreading north as the climate warms?

Yes, gradually. Dallisgrass was historically a Zone 7-10 weed concentrated in the South. Documented populations have expanded into Zone 6b across the past two decades — northern Kentucky, southern Indiana, southern Ohio, southern Pennsylvania. The cold-tolerance limit appears to be around minus 5 to minus 10°F sustained, which northern transition-zone winters are increasingly failing to reach. Homeowners in newly affected regions often misdiagnose dallisgrass as crabgrass or quackgrass because the species is unfamiliar locally. For up-to-date range information, consult your state cooperative extension or USDA PLANTS database.

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