The label is the law. Read your product's label before you mix or apply; the rates here come from the labels listed under Sources.
- Active ingredient
- Acephate (CAS 30560-19-1)
- Chemical class
- Organophosphate; IRAC Group 1B acetylcholinesterase inhibitors.[2]
- Mode of action
- IRAC Group 1B: Acetylcholinesterase (AChE) inhibitors: organophosphates[2]
- Signal word
- Ortho Orthene Fire Ant Killer II: Caution[1]
Mound treatments versus baits
University of Kentucky entomologists list acephate among the dusts for direct mound treatment, alongside liquid drenches and broadcast insecticides. They prefer baits, which workers carry in to feed the colony, because the effect is specific to ants and leaves less residue, though baits take longer.[3]
Where it is used
Sprinkle the dry powder over the mound without disturbing it, and don't water it in.[1]
Apply when ants are active. In prolonged hot, dry weather the ants are deep in the nest and treatments may fail; don't apply in heavy dew or just before rain.[1]
Treat new mounds as they appear and repeat if ants come back. The label claims existing mounds die within 3 to 7 days.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| Ortho Orthene Fire Ant Killer II[1] | The Scotts Company | 239-2632 | 50.0% | dry powder (mound treatment) | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| Ortho Orthene Fire Ant Killer II | Individual mounds in home lawns and around flowers, shrubs and trees | Fire ants, red harvester ants | 1–9 teaspoons per mound[1] 1 teaspoon for mounds under 4 inches across, 4 teaspoons for 4 to 12 inches, and 3 tablespoons (9 teaspoons) for mounds over 12 inches. |
How to apply it, step by step
1. Protective gear
- Wear a long-sleeved shirt, long pants, shoes, socks and waterproof gloves when handling it, and wash the outside of the gloves before taking them off.[1]
- Keep it out of your eyes and off your clothing, and wash your hands before eating, drinking or using the toilet.[1]
2. Before you spray
- Don't apply it in a way that will contact people or pets, and keep it away from water; it is toxic to birds.[1]
3. Mixing
- Nothing to mix: sprinkle the dry powder straight from the container.[1]
4. Applying
- Sprinkle 1 teaspoon over mounds under 4 inches across, 4 teaspoons for mounds 4 to 12 inches, and 3 tablespoons for larger mounds, trying not to disturb the mound.[1]
- Apply while the ants are active; in long hot, dry spells the ants may be too deep in the nest for it to work. Don't water it in, and treat new mounds as they appear.[1]
5. After you spray
- Watch for new mounds and treat each one as it appears, using the same per-mound amounts.[1]
First aid
- If swallowed, call a poison control center or doctor immediately, have the person sip a glass of water if able, and don't induce vomiting unless told to; in the eyes, rinse slowly and gently with water for 15 to 20 minutes.[1]
Storage, spills and disposal
- Keep it in the original container in a cool, dry, preferably locked place.[1]
- Put an empty container in the trash or recycling; for a partly full one, call your local solid waste agency, and never pour it down a drain.[1]
From the safety data sheet
- The product is a white to off-white powder with a sulfurous odor, and the SDS uses the signal word Warning: harmful if swallowed and causes eye irritation.[4]
- Avoid breathing the dust and avoid contact with eyes, skin and clothing; fine dust clouds may form explosive mixtures with air.[4]
- If it gets in the eyes, flush them with plenty of water for at least 10 minutes, lifting the eyelids and removing contact lenses, and get medical attention if irritation persists.[4]
- If swallowed, rinse the mouth with water and give small sips of water to a conscious person; don't induce vomiting unless medical staff tell you to, and get medical attention.[4]
- Clean up spills without making dust, ideally with a HEPA-filter vacuum rather than dry sweeping, put the material in a labeled container, and keep it out of drains and waterways.[4]
Safety and environmental hazards
People
Signal word CAUTION: harmful if swallowed and causes moderate eye irritation. Wear long sleeves, long pants, shoes, socks and waterproof gloves. The label's note to physicians identifies it as a cholinesterase inhibitor, with atropine as the antidote.[1]
Pets
Don't apply it in a way that contacts people or pets, and keep them out of the treated area until the dust has settled.[1]
Bees and pollinators
The label's environmental warning is for birds and water: it is toxic to birds, and spills should be covered or worked into the soil.[1]
Fish and water
Don't apply directly to water or let it reach storm drains, ditches or gutters; apply in calm weather with no rain forecast for 24 hours.[1]
Common questions
- How much Orthene per fire ant mound?
- 1 teaspoon for mounds under 4 inches, 4 teaspoons for 4 to 12 inches, and 3 tablespoons for larger mounds.[1]
- Should I water in acephate fire ant killer?
- No. The label says do not water it in, and not to apply before rain.[1]
- When can kids and pets go back on the lawn?
- After the dust has settled, per the label's re-entry statement.[1]
Sources
- U.S. EPA Pesticide Product Label System, “Ortho Orthene Fire Ant Killer II label, EPA Reg. No. 239-2632 (EPA-stamped, June 27, 2016).” www3.epa.gov/pesticides/chem_search/ppls/000239-02632-20160627.pdf (accessed 2026-10-06)
- Insecticide Resistance Action Committee, “IRAC Mode of Action Classification Scheme, Version 11.5 (Feb. 2026).” irac-online.org/documents/moa-classification/ (accessed 2026-10-06)
- University of Kentucky Entomology, “ENTFACT-469: Imported Fire Ants in Kentucky.” entomology.mgcafe.uky.edu/ef469 (accessed 2026-10-06)
- The Ortho Group, “ORTHO ORTHENE FIRE ANT KILLER 1 Safety Data Sheet (The Ortho Group, version 1.3, revised March 13, 2023; EPA Reg. No. 239-2632, the label on this page; copy hosted by the City of Savannah, Georgia).” savannahga.gov/DocumentCenter/View/34412/SDS (accessed 2026-10-17)