Herbicide · reference
MSMA 6 Plus
An organic-arsenical post-emergent grass herbicide — the old-school knockout for crabgrass, dallisgrass, sandbur, and nutsedge that resist gentler chemistry. It works, but it is an arsenic compound whose lawn use has been heavily restricted by the EPA — this is the most tightly-regulated bottle on the shelf, and the one to reach for last.
- Maker
- Drexel Chemical Company
- Active
- Monosodium acid methanearsonate (MSMA), 47.6% — 6 lb/gal ("6 Plus"); with surfactant
- MoA group
- WSSA Group 17 (organic arsenical — was Group 22/Z)
- EPA reg
- 19713-42
- Net contents
- 2.5 gallons
- Signal
- caution
✍ On the jug — Dan's note"2 fluid oz per gallon · 70°F · No fescue on Bermuda-lawn use · 2021" Read off the jug, not the label rate — verify against the booklet before mixing.
01Usage
What it's for and where it goes.
- Targets: Crabgrass, dallisgrass, sandbur, nutsedge, bahiagrass and other tough grasses.
- Where (label): Cotton, sod farms, golf courses, and highway rights-of-way — not general residential lawns. On turf it's for bermudagrass; the handwritten note warns "no fescue" and Bermuda-only — MSMA injures cool-season grasses.
- Rate: Your note reads ~2 fl oz/gal at ~70 °F. Label rate varies by site.
- Built-in surfactant ("Plus") — no separate wetter needed.
02Efficacy
How well it actually works.
- Very strong on grassy weeds that shrug off selective herbicides — historically the dallisgrass/sandbur standard.
- Needs warm, actively-growing weeds; slow, visible over 1–2 weeks. Often needs a repeat.
03Best at killing
What it's genuinely strongest on in real use.
- The tough grasses nothing else touches — MSMA's historical claim to fame is dallisgrass, sandbur, and hard crabgrass in warm-season turf, plus some nutsedge. It is the old dallisgrass standard because selective herbicides simply do not control it; on a Bermuda or Zoysia lawn it "will absolutely obliterate dallisgrass" per practitioner accounts. Needs warm, actively-growing weeds and often a repeat.
- Bermuda-only on lawns — it injures cool-season grasses (see below).
04Dangers
What it can hurt — read this before you reach for it.
- Organic arsenical — contains arsenic. This is the headline. EPA has phased MSMA out of most turf/residential use over groundwater and arsenic concerns; remaining uses are narrow and regulated. Treat it as a legacy, restricted product and check your state's current rules before any use.
- Not selective on cool-season turf — kills/injures fescue, bluegrass, rye. Bermuda-only on lawns.
- Toxic; avoid skin/eye contact and inhalation. Keep far from water — arsenic mobility is the environmental concern.
05🐾 Dogs & re-entry
Pet safety — toxicity and how long until a dog can be back on it.
🐾 Pet safety — read before you let the dog out
- Toxicity — the standout on this shelf: MSMA is an organic arsenical (contains arsenic), which is why the EPA phased it out of most turf/residential use. Dogs ingesting it can show vomiting, diarrhea, drooling, lethargy, and (arsenic's target) kidney effects (Thurston County HHW, MSMA; a documented overdose case: Ratnapalan et al., J Med Toxicol 2013).
- When safe again — sourced: the MSMA 6 Plus label sets a 12-hour Restricted-Entry Interval ("Do not enter or allow worker entry into treated areas during the REI of 12 hours" — Drexel MSMA 6 Plus label). Given the arsenic, be conservative: keep dogs off until fully dry, watered-in, and at least the 12h REI — and do not let a dog dig or graze treated turf.
General guidance. Confirm the label's re-entry interval and ask your vet; when unsure keep dogs off until fully dry.
06Storage
How to keep it, and keep it separate.
- Original container, tightly closed, cool/dry, away from children, food, feed, and any water source.
- Given the regulatory status, don't acquire more — use up or dispose of via hazardous-waste channels, not down a drain.
landscape.gf.cx · chemicals · msma-6-plus · filed 2026-07-23 · read off the label — verify every rate against the booklet