How do I use Terro Ant Dust (T600) correctly?

First confirm the target area — a crack, wall void, crawl space, or pipe penetration — is dry and likely to stay that way, since moisture ruins the dust almost immediately. Use the shaker canister to apply a thin, barely-visible film, not a visible pile: puff it into voids, behind appliances, and along hidden runways rather than mounding it on open surfaces. Keep it confined to cracks and voids away from living-surface areas and air currents, and only reapply where the film has been disturbed, cleaned off, or gotten wet. The single biggest technique mistake is applying too much — a light film clings to insects and works for months, while a heavy pile is repellent and gets avoided.

Does Terro Ant Dust actually work?

For what it's designed to do, yes, and genuinely well: University of Maine Cooperative Extension guidance confirms that dusts reach deep into cracks, walls, voids, and other spaces that liquid formulations can't stay in, and a thin, dry, undisturbed deltamethrin film keeps killing insects that cross it for a long stretch of time — manufacturer marketing cites up to about 8 months under ideal conditions. Where it falls short is as a standalone fix for a foraging ant colony: it's a repellent contact residual, not a bait ants carry home, so it kills the foragers that walk through it without necessarily reaching the nest.

Why do I still see ants after dusting?

A dust residual kills insects that physically cross the treated film — it doesn't reach a colony nesting somewhere the dust was never placed. If ants keep trailing in a new spot despite correct, dry, undisturbed application elsewhere, that's a sign of an established or satellite colony that a contact residual alone can't finish. Pairing the dust with an actual liquid or gel ant bait (kept in a physically separate zone so the two don't interfere) targets the colony directly, and persistent activity after that combination is a signal to call a professional.

Is a dust really better than a spray for this job?

For dry, undisturbed voids and cracks — yes, genuinely. University extension guidance is explicit that dust formulations disperse into wall voids and inaccessible spaces that sprays and baits can't reach or survive in, and because it stays dry it avoids the UV and rain degradation that shortens an outdoor liquid residual's life. The trade-off is technique difficulty: a dust only works if it stays thin, dry, and undisturbed, which takes more care than pointing a wand at a baseboard, and it offers no advantage in open, exposed, or high-traffic areas where a different format is a better fit.

Can I use it on an active ant trail to speed things up?

Be careful here — dusting directly over a visible, active ant trail isn't the same as baiting it. Like other repellent pyrethroids, a contact dust can scatter foragers away from the treated area rather than letting them carry a toxicant back to the colony, which is the entire mechanism that makes true baiting effective against a hidden nest. If you're also using a liquid or gel ant bait, keep the dust and the bait in physically separate zones of the home rather than layering them on the same trail.

Is it safe to use around my pets?

The main precaution is keeping the dust confined and dry: avoid generating airborne particles during application, keep pets and kids out of the treated void or crack area, and never let dust accumulate on an open, accessible surface. This is a deltamethrin pyrethroid dust, so don't breathe it in and don't apply it where pets dig, chew, or groom themselves nearby. For the full per-species pet-safety verdict on this specific product, see the companion review at /is-pest-control-safe-for-pets/ant-dust-insect-killer-t600-by-terro.

Daniel Brady · NH-Licensed Pesticide Applicator · License #782664

How to Use Ant Dust Insect Killer (T600) by Terro

Workhorse

Deltamethrin 0.05%

Terro Ant Dust (T600) is fundamentally different from the aerosol cans it's often shelved next to: it's a waterproof deltamethrin dust you puff into cracks, voids, and crawl spaces, not a wet spray. Used correctly, it's a genuine workhorse — university extension guidance confirms dusts reach deep into wall voids and other spaces a liquid residual can't stay in, and a thin, dry, undisturbed film keeps killing insects that walk through it for months. The technique that decides success is the opposite of what people assume: a thin, barely-visible film clings to insects and lasts; a thick, visible pile gets avoided and clumps in the first bit of moisture. What it does NOT do is act like a bait that ants carry back to the colony — it's a repellent contact residual, so dusting over an active foraging trail can scatter ants rather than eliminate the nest. Keep it dry, keep it thin, keep it out of living-surface areas, and if an ant trail keeps returning despite correct dry-void treatment, that's your signal the colony itself needs a different approach.

At a glance

Efficacy: Workhorse
Best job: Long-lasting residual protection in dry, undisturbed wall voids, cracks, and crawl spaces that a wet spray can't stay in
Format: Ready-to-use waterproof dust in a shaker canister — this is a DUST, not a wet spray or aerosol, despite living in the same product cluster as one. No mixing.
Technique: Moderate technique

The honest verdict

Does this product actually work?

The verdict on this product

WorkhorseModerate technique

Workhorse

A genuine workhorse for dry voids and crack-and-crevice work — situational, not a cure, if you're counting on it alone to stop a foraging ant colony.

University of Maine Cooperative Extension is explicit that dusts 'disperse deeply into cracks, walls, voids and other inaccessible areas that are not treatable with other formulations,' and Terro's deltamethrin dust genuinely delivers on that in a dry, undisturbed void — that's a real advantage a wet spray's fading residual can't match. But applied over an ant trail or used as a general surface treatment, a repellent contact dust behaves like any pyrethroid: it kills what walks through it and can scatter foragers away from the colony rather than through it. Use it for what dusts do best — deep, dry, out-of-sight placement — and don't expect it to replace baiting for a colony you're trying to eliminate at the source.

Best for

A long-lasting residual in dry wall voids, cracks, crawl spaces, and pipe penetrations that a liquid spray's residual can't match.

Skip it for

Damp basements, open living surfaces, or as your only tool against an established, foraging ant colony — it's a repellent contact insecticide, not a bait.

Read the label first

What it is — and what it's really for

The label is the law. Here's the honest read on the format, the one job it does well, and the job people wrongly buy it for.

Format

Ready-to-use waterproof dust in a shaker canister — this is a DUST, not a wet spray or aerosol, despite living in the same product cluster as one. No mixing.

Indoor / outdoor

both

Residual

Manufacturer marketing claims effectiveness up to about 8 months when the film stays dry and undisturbed; university IPM guidance confirms dusts are the format of choice for undisturbed voids precisely because they don't break down like a wet residual, but any moisture or disturbance shortens that life sharply

Target pests

Ants (including carpenter ants; the label also lists fire ants, which are not a New Hampshire pest), Cockroaches, Boxelder bugs, Crickets, Firebrats, Spiders, Ticks, Wasps, Silverfish

Best job

Long-lasting residual protection in dry, undisturbed wall voids, cracks, and crawl spaces that a wet spray can't stay in

Active ingredient

Deltamethrin (0.05%)

Not for (honest)

Open, exposed, or damp surfaces, and as a standalone fix for a foraging ant colony — it's a repellent contact residual, not a bait ants carry home

The technician's method

The technique walkthrough

Where DIY succeeds or fails is in the placement, patience, and the small pro moves the label never mentions. Follow the label; these are the technique details on top of it.

Moderate technique~15-30 min to apply; insects pick up a lethal dose over hours as they cross the filmTools:The shaker canister (or a hand duster for tighter voids), Gloves, A flashlight to locate crack/void openings

This is a moderate-difficulty product precisely because the instinct to apply 'more' is wrong — the whole technique is a thin, dry, out-of-sight film, not a visible line of powder.

Confirm the target area is dry
Check that the crack, void, or crawl space you're about to treat is dry and likely to stay dry — dust clumps and loses effectiveness the moment it gets wet.
Common mistake
Dusting a damp basement corner or an area exposed to rain or sprinklers — the dust mats down and stops working almost immediately.
Apply a thin, barely-visible film — not a pile
Use the shaker (or a hand duster for precision) to lay down a light dusting into cracks, crevices, voids, and along hidden runways.
Pro move
Less is more: a light film clings to an insect's body as it walks through, which is the entire mechanism. A heavy, visible mound is both wasteful and repellent.
Common mistake
Laying a thick, visible line of dust along a baseboard. Insects detour around visible piles instead of walking through them, and it becomes a mess to clean up.
Puff into voids, not onto open surfaces
Direct the dust into pipe penetrations, under/behind appliances, crawl spaces, and wall voids — the enclosed, undisturbed spaces where the long residual life actually pays off.
Keep it out of living-surface areas and air currents
Confine dust to cracks and voids people and pets don't walk through or breathe near; don't apply where airflow could carry particles into the room.
Caution
Avoid generating airborne dust and don't breathe it in during application.
Leave it undisturbed; reapply only where it's been disturbed or wet
Once placed, leave the film alone. Reapply only to spots that have been cleaned, gotten wet, or visibly thinned — not on a fixed calendar.

Habits that decide it

Do & don't

Apply a thin, barely-visible film into dry voids and cracks.
Confirm the space is dry before dusting and likely to stay that way.
Use a hand duster for precise placement in tight voids.
Reapply only where the film has been disturbed or gotten wet.

Don't

Don't create heavy, visible piles — they repel insects and waste product.
Don't dust damp basements, exposed patios, or open living surfaces.
Don't dust directly over an active ant trail you're trying to bait separately.
Don't let dust become airborne where people or pets breathe.

The honesty moat

Where it works vs. where it fails

No product fixes everything. This is the honest boundary — the situations it genuinely handles, and the ones it simply won't.

Where it works

Dry wall voids, crawl spaces, and pipe/utility penetrations need a long-lasting residual
A crack-and-crevice void is undisturbed enough for a dry film to persist for months
Occasional invaders — spiders, silverfish, crickets — travel through a treatable dry void
You're supplementing (not replacing) a baiting program with dry-void residual protection

Where it fails

The area is damp, exposed to rain, or gets cleaned/disturbed regularly
You're relying on it alone to eliminate a foraging ant colony — it's repellent contact, not a bait ants carry home
You apply it as a thick, visible pile that insects simply avoid
The nest or colony is somewhere the dust was never placed

Don't throw money away

Mistakes that waste the product

Applying a heavy, visible layer instead of a thin film

A thick pile is both wasteful and repellent — insects detour around visible dust instead of walking through the light film that actually kills them.

Fix

Puff a barely-visible dusting; if you can clearly see a line of powder, you've applied too much.

Dusting a damp or exposed area

Moisture clumps the dust and destroys the residual almost immediately, wasting the long-lasting advantage that makes dust worth using in the first place.

Fix

Confine application to dry, undisturbed voids, cracks, and crawl spaces.

Treating the dust like an ant bait ants will carry to the colony

This is a repellent contact residual, not an attractant toxicant — foragers that contact a heavy application can scatter rather than transfer the active back to the nest.

Fix

Use it for dry-void residual protection, and pair it with an actual liquid or gel bait (kept in a separate zone) for colony-level ant control.

Dusting over or near an active bait placement

Like any repellent pyrethroid, it can drive foragers away from a bait you want them to carry back to the colony.

Fix

Keep dust zones and bait zones physically separate.

Calibrated expectations

What to expect — and when

This is a slow-and-steady residual tool, not an instant knockdown — judge it on how long a dry, undisturbed film keeps working, not on how fast ants disappear.

Hours after contact
Insects that walk through the thin film pick up a lethal dose over subsequent hours; manufacturer materials cite maximum visible results within a few days.
First few days
Fewer insects crossing the treated voids and cracks as the film keeps contacting new foragers.
Weeks to months (if kept dry and undisturbed)
The residual can genuinely persist for months in an undisturbed dry void — but a colony nesting elsewhere keeps sending new foragers, so ongoing activity outside the treated zone is expected, not a sign of failure.

When results plateau

Results plateau when the actual nest is outside the treated voids: the dust kills foragers that cross the film, but a repellent contact residual doesn't reach or eliminate a colony the way a transferable bait does — persistent trailing elsewhere is the signal to add baiting or escalate.

Know the ceiling

When to stop DIY & call a pro

A shaker-can dust only reaches the voids you can physically get powder into, and a colony nesting past them stays untouched. These are the honest signals the job has outgrown a shaker canister:

Carpenter-ant activity in structural wood — rustling in walls, frass piles, or winged swarmers indoors
Carpenter ants are among New Hampshire's most troublesome structural pests, and a void dust can't verify or eliminate a nest inside a wall or joist.
An ant trail keeps returning to the same spot despite correct, dry, undisturbed dust placement
Recurring activity points to an established or satellite colony a contact residual can't reach — that needs baiting or professional treatment, not more dust.
The problem area can't realistically be kept dry
Dust loses its core advantage the moment it's wet, so a chronically damp space needs a different tool entirely.
Any suspected termite activity — mud tubes, swarmers, or damaged wood
A consumer dust product is not labeled or capable of addressing a termite colony.

When correctly placed dust isn't holding the line, Anchor's licensed NH technicians identify the actual colony or nest and treat it with targeted professional void, dust, and baiting methods. Free inspection, same-day service across southern and central New Hampshire.

Ant trail keeps coming back despite the dust?

Get a Free inspection (603) 785-0118

Before you treat

Is it safe for pets & kids?

The short version lives here; the full per-species verdict lives on this product's pet-safety page.

This is a deltamethrin pyrethroid dust — avoid generating airborne particles, keep kids and pets out of treated void areas, and never breathe the dust in. Never treat a suspected exposure at home.

Re-entry: Keep children and pets out of dusted areas until the dust has settled and is confined to the treated crack or void.

If there's an exposure, call

ASPCA Animal Poison Control: (888) 426-4435 Pet Poison Helpline: (855) 764-7661 Northern New England Poison Center: (1-800) 222-1222

See the full per-species pet-safety verdict for this product

New Hampshire context

Not a fire-ant product here — carpenter and pavement ants are the NH reality

The T600 label lists fire ants because it's sold nationally, but fire ants are essentially absent from New Hampshire. What southern and central NH homeowners actually deal with are carpenter ants (the state's dominant structural ant, alongside termites) and pavement or odorous house ants foraging indoors. A thin dust film in a dry crawl space or wall void is a genuinely useful tool against these, but rustling in a wall, frass piles, or winged swarmers indoors point to a carpenter-ant nest that dust alone won't finish. Anchor Pest Services treats the actual source across Manchester, Nashua, Concord, and the surrounding towns.

Service area

Southern New Hampshire

Anchor Pest Services · NH license #782664 · NEPMA member · family-owned since 2017.

Common questions

Frequently asked

Sources & further reading(5)

[1]
TERRO — Ant Dust (T600) product page
Verified active (deltamethrin 0.05%), waterproof dust format, listed target pests, up-to-8-months marketing claim (facts only, not the efficacy verdict)
manufacturerverified 2026-07-14
[2]
NPIC — Deltamethrin General Fact Sheet
Deltamethrin pyrethroid class, contact/ingestion mode of action, formulation types including dusts
npicverified 2026-07-14
[3]
University of Maine Cooperative Extension — Pest Management Fact Sheet #5011 (Cockroaches)
Dusts disperse deeply into cracks, walls, voids and inaccessible areas not treatable with other formulations; dusts and baits are most adversely affected by damp conditions
extensionverified 2026-07-14
[4]
UC IPM — Ants (Home & Landscape)
Perimeter/contact insecticide treatments kill only foragers, not the colony or queen
extensionverified 2026-07-14
[5]
UNH Cooperative Extension — Carpenter Ants Fact Sheet
Carpenter ants nest in structural wood — a call-a-pro escalation, not a void-dust target
extensionverified 2026-07-14

Written & reviewed by

Verified

Daniel Brady

NH-Licensed Pesticide Applicator · License #782664 (NHDAMF, RSA 430)

Daniel Brady is the New Hampshire–licensed applicator behind Anchor Pest Services, a family-owned pest control company serving the Manchester area since 2017.

Verify license

Last updated July 2026

Related products in this category

Same shelf, different jobs — the dot shows each product's honest efficacy verdict at a glance.

Ant & Roach Killer Spray by RaidWorkhorse

D-Force Insecticide Aerosol Spray by WaterburyWorkhorse

Phantom Aerosol Insecticide by BASFWorkhorse

Professional Pest Control

When a Void Dust Isn't Enough

A contact dust protects the crack or void you treat, but it can't reach a colony nesting somewhere else. Anchor Pest Services treats the actual source with targeted, licensed methods across southern and central New Hampshire. Family-owned since 2017, NH license #782664.

Get a Free inspection (603) 785-0118

Targeted source treatment, not just void dusting
NH-licensed applicators (#782664)
Free inspection — same-day service across southern NH

NH License #782664 · No obligation · We answer in person

Keep Exploring

How to Use Ant Dust Insect Killer (T600) by Terro

Does this product actually work?

What it is — and what it's really for

The technique walkthrough

Confirm the target area is dry

Apply a thin, barely-visible film — not a pile

Puff into voids, not onto open surfaces

Keep it out of living-surface areas and air currents

Leave it undisturbed; reapply only where it's been disturbed or wet