Why do I see MORE ants after placing Terro T300?

This is expected and it means the bait is working, not failing. As foragers find the sweet liquid, they recruit nestmates to the food source with a pheromone trail, so you'll typically see a surge in visible activity in the first few days. Terro's own materials describe this pattern directly: ants will come in large numbers at first, then soon disappear as the colony is dosed. Resist the urge to spray or wipe the trail during this stage — that's the single most common way people sabotage the bait, and it's a genuinely counterintuitive instinct worth overriding.

Does Terro T300 actually work?

For sweet-feeding household ants — odorous house, pavement, little black, and Argentine ants — yes, when placed directly on an active trail and left undisturbed. University of California Riverside field-trial research on borate/sucrose baits found roughly an 80% reduction in ant numbers with a properly formulated liquid bait, because the slow-acting borax lets foragers carry it back and share it colony-wide before dying. It does not work on carpenter ants (Terro's own label excludes them) or reliably on ants currently in a grease-feeding phase, so match the product to the ant you actually have.

How long before I see results?

Give it time — this is a colony tool, not a same-day spray. Expect an activity surge in the first few days as ants recruit to the bait, then a decline over the following days as the colony is dosed. Terro's label states complete control may take up to two weeks, and larger or multi-queen colonies can take longer than that. If you switch to a contact spray out of impatience during the surge, you'll likely undo the progress the bait has already made, since foragers killed on contact never make it back to share the dose.

Can I use T300 on carpenter ants?

No — Terro's own label states it is not recommended for carpenter ants, and our research confirms carpenter ants need a different approach entirely. Carpenter ants nest in structural wood, and UNH Extension calls them one of New Hampshire's most troublesome structural pests alongside termites. A sweet liquid bait won't reach or interest a carpenter-ant colony the way it does an odorous house or pavement ant trail. If you're seeing large black ants, especially indoors in winter, treat that as a call-a-pro signal rather than a T300 job.

Is it okay to clean up around the bait stations?

Yes, but be selective about where. Cleaning up crumbs, spilled sugar, and pet food near the stations actually helps, because it removes competing food sources and makes the bait more attractive by comparison. What you should not do is wipe, spray, or clean the trail line itself or the stations directly — that erases the pheromone path ants are following and can stall the whole baiting cycle. Clean around the placement, never on it, while ants are actively feeding.

What if I don't see an ant trail to place bait on?

T300 depends on placing bait where ants are actively foraging, so scattered scout ants without a real trail make it harder to know where to place stations. Start by placing several stations near likely entry points — baseboards, under sinks, door and window frames — and check back in a day; ants find a good food source quickly if they're active nearby. If you still see no uptake after a few days, you may be dealing with a small or dispersed population, or a species this bait's sweet-liquid attractant doesn't appeal to, which is worth a quick call to confirm before assuming the product failed.

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

How to Use Terro Liquid Ant Baits (T300)

Workhorse

Sodium tetraborate decahydrate (borax) 5.40%

Terro's T300 works when you place the pre-filled stations directly on or beside an active ant trail and then leave them alone. The 5.40% borax liquid is slow-acting by design: foragers drink it, carry it home, and share it colony-wide before it kills them, which is why extension research credits properly used borate baits with real colony-level control, including the queen. Expect to see MORE ants at the bait for the first few days — that's recruitment, not failure, and killing or spraying those ants is the single most common way people sabotage the product. It does not work on carpenter ants (Terro's own label says so) or reliably on ants currently feeding on grease and protein, and full control on a large or multi-queen colony can take up to two weeks. If trails persist past that window despite correct, undisturbed placement, the colony is likely bigger than a homeowner-scale liquid bait program can clear.

At a glance

Efficacy: Workhorse
Best job: Delivering a slow-acting borax dose into a sweet-feeding ant colony via the ants' own foraging trail
Format: Pre-filled, sealed liquid bait stations — 6 stations per pack, no mixing (EPA Reg. No. 149-8)
Technique: Easy technique

The honest verdict

Does this product actually work?

The verdict on this product

WorkhorseEasy technique

Workhorse

A genuine workhorse for sweet-feeding household ants — if you can find the trail and resist the urge to spray it.

Placed directly on an active trail and left completely undisturbed, T300 reliably reaches the colony — including the queen — because foragers carry the liquid borax home before it kills them; UC Riverside field-trial data on properly formulated borate/sucrose baits found roughly an 80% reduction in ant numbers. It fails when placed off-trail, when a spray or cleaning disrupts the pheromone trail, on carpenter-ant nests, or on ants currently in a grease-seeking phase. This is a colony tool, not a same-day fix — 'more ants at first' is the bait working, not failing.

Best for

Odorous house, pavement, little black, and Argentine ants trailing indoors or at entry points while the colony is currently favoring sweets.

Skip it for

Carpenter ants (Terro's own label excludes them and directs you to a contact spray instead), grease-phase ants ignoring the sweet liquid, and fire ants (essentially absent from New Hampshire).

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

Pre-filled, sealed liquid bait stations — 6 stations per pack, no mixing (EPA Reg. No. 149-8)

Indoor / outdoor

both

Residual

A station keeps working as long as it stays liquid and ants keep feeding; check and refill or replace before a reservoir runs dry, commonly within a few weeks of active feeding

Target pests

Odorous house ants, Pavement ants, Little black ants, Argentine ants, Ghost ants, Cornfield ants, Acrobat ants, White-footed ants, Crazy ants, Big-headed ants, other sweet-eating household ants

Best job

Delivering a slow-acting borax dose into a sweet-feeding ant colony via the ants' own foraging trail

Active ingredient

Sodium tetraborate decahydrate (borax) (5.40%)

Not for (honest)

Carpenter ants (Terro's own label excludes them), grease/protein-feeding ants that aren't currently interested in sweets, and fire ants — a non-issue in NH anyway

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.

Easy technique~10-20 min to place; results build over days to two weeksTools:The pre-filled stations (no mixing), A flashlight to trace the trail, Nothing else — do not bring a spray bottle or cleaner

T300 is one of the easiest products in this hub to place and one of the easiest to sabotage — nearly every failure traces back to impatience, not the bait itself.

Trace the trail before you place anything
Follow the visible ant line back toward its entry point or the busiest stretch of trail — that's where the station goes, not just 'somewhere near where ants were seen.'
Pro move
Check under sinks, along baseboards, and around window and door frames — trails concentrate at these entry points.
Common mistake
Placing a station in a random corner of the kitchen because that's where an ant was noticed once, rather than on the trail ants are actually using.
Snap the tab and place stations flat, right on the trail
Snap open the stations and lay them flat directly on or immediately beside the active trail, at entry points, and along baseboards.
Pro move
Use all six stations — more placements mean more foragers find bait faster, especially outdoors where several entry points may be active at once.
Common mistake
Using just one station 'to see if it works' — a single placement dramatically slows colony-level uptake.
Remove competing food
Clean up crumbs, spilled sugar, juice, and pet food nearby so the bait is the most attractive food source available.
Caution
Clean around the trail, not on it — wiping the trail line itself erases the pheromone path ants are following.
Do not touch, move, or spray the stations once ants are feeding
Leave placements completely undisturbed while ants are actively feeding. Do not spray insecticide, wipe with cleaner, or vacuum near the trail.
Common mistake
Spraying a contact insecticide on the trail during the first-days surge, thinking more ants means the bait isn't working — this kills foragers before they carry bait home and is the #1 mistake with this product.
Let the surge run its course
Expect noticeably more ants at the bait in the first few days as foragers recruit nestmates to the food source. This is the bait working.
Pro move
Note the date you placed the stations so you judge progress on a realistic 1-2 week timeline instead of a same-day one.
Refill or replace before a station runs dry
Check stations periodically; an empty reservoir stops contributing to the colony dose even if it worked perfectly while full.
Common mistake
Leaving a dried-out station in place for weeks, assuming the job is done, while the colony rebuilds.

Habits that decide it

Do & don't

Place stations directly on or beside the active trail
Use all the stations in the pack, not just one
Remove competing food and moisture near (not on) the trail
Be patient through the first-days activity surge
Keep stations out of reach of pets and children

Don't

Don't spray or wipe the trail — it breaks the pheromone path
Don't kill visible foragers at the bait
Don't expect overnight results
Don't use it on carpenter ants — it's the wrong tool
Don't leave an empty station in place expecting it to keep working

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

An active sweet-ant trail is visible and identifiable
The target is odorous house, pavement, little black, Argentine, or similar sweet-feeding ants
You can tolerate a days-to-two-week timeline without switching to a spray
Multiple stations are placed at real entry points and trail segments

Where it fails

No active trail can be found — only scattered scouts
The trail gets disturbed by cleaning, spraying, or heavy foot traffic
The target is carpenter ants (Terro's own label excludes them)
Ants are in a grease/protein-feeding phase and ignoring the sweet liquid
The colony is very large or has multiple satellite nests beyond homeowner-scale baiting

Don't throw money away

Mistakes that waste the product

Spraying or wiping the trail during the activity surge

Kills foragers before they carry bait back and destroys the pheromone trail the whole strategy depends on.

Fix

Leave the trail and stations completely undisturbed; let the surge run its course.

Placing only one station

Fewer placement points mean fewer foragers encounter the bait, slowing colony-level uptake.

Fix

Deploy all six stations across trail segments and entry points.

Leaving competing food out nearby

Ants will feed on easier food sources instead of the bait, stalling the program.

Fix

Clean crumbs, spills, and pet food around the trail (not on it) so the bait wins the competition.

Expecting results in a day or two

Judging the product on a same-day timeline and abandoning it for a spray misreads how the borax mechanism works.

Fix

Give it up to two weeks, especially for a larger or multi-queen colony.

Using T300 on carpenter ants

Terro's own label excludes carpenter ants — the bait isn't formulated for a structural nest and won't clear it.

Fix

Use a contact product for foragers or, better, call a professional for suspected carpenter-ant activity.

Calibrated expectations

What to expect — and when

Judge this product on colony-level decline over days to two weeks, not on how many ants you see tomorrow.

First few hours to days
Visibly MORE ants at the bait as foragers recruit nestmates — this is the bait working, not a worsening infestation.
Days 3-7
Foraging activity at the bait typically starts to decline as the colony is dosed.
Up to 2 weeks
Terro's own label states complete control 'may take up to two weeks' — larger or multi-queen colonies can take longer.

When results plateau

If sweet-feeding ants keep trailing after two weeks of undisturbed, correctly placed wells, they've likely switched to grease or protein, the placement was bumped or wiped, or the colony is a large multi-satellite or carpenter-ant nest — all past what open homeowner-scale liquid bait can drain.

Know the ceiling

When to stop DIY & call a pro

Open liquid-bait wells work beautifully on a small sweet-feeding trail and poorly once the colony is large, split, or off sugar. These are the honest signals it's time to bridge to a licensed technician:

Trails persist past about 2 weeks of correctly placed, undisturbed baiting
Persistent activity despite correct technique usually means a colony larger than homeowner-scale baiting can clear.
You see large black ants, especially indoors in winter, or hear rustling in walls
Those are carpenter-ant indicators — a structural pest T300 isn't formulated for that needs professional inspection.
Activity reappears at multiple points around the structure
That can signal a large colony or multiple satellite nests beyond a single baiting program.
Trails keep returning at the same interior entry point despite repeated exterior baiting
An unaddressed exterior colony or entry pathway needs targeted, professional treatment to close for good.

When correct, patient baiting still isn't holding the line, Anchor's licensed NH technicians identify the species and the nest and treat the actual source. Free inspection, same-day service across southern and central New Hampshire.

Trails still active after two weeks of correct baiting?

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.

Borax is a low-toxicity active relative to many synthetic insecticides in this hub, but the liquid reservoir isn't harmless if a pet or curious toddler accesses it directly. The practical precaution is placement, not avoidance.

Re-entry: Place and keep stations out of reach of pets and children — under appliances, in cabinet corners, or behind furniture rather than on open floor.

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

Trail timing in New Hampshire

Southern and central New Hampshire's sweet-feeding nuisance ants — odorous house and pavement ants especially — push indoors as trails warm in spring and again as they seek shelter in fall, which is when a trail is easiest to find and bait. Carpenter ants, common in NH's wooded lots, are the one local ant this product explicitly isn't for; if you're seeing large black ants or debris near a nest site, that's Anchor's call, not T300's. Anchor Pest Services serves 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(7)

[1]
EPA Registered Product Label — Terro Ant Killer II / Liquid Ant Baits (T300), EPA Reg. No. 149-8
Verified active (borax 5.40%), sealed pre-filled station format, labeled ant species list, carpenter-ant exclusion
epa_labelverified 2026-07-14
[2]
Klotz, Greenberg & Venn, 'Liquid Boric Acid Bait for Control of the Argentine Ant,' J. Econ. Entomol. 91(4):910-914 (1998)
Field trial finding ~80% reduction in ant numbers with a 0.5% boric acid / 25% sucrose bait
academicverified 2026-07-14
[3]
UC Statewide IPM Program — Ants (Home & Landscape)
Slow-acting bait mechanism, colony/queen-level control vs. forager-only sprays
extensionverified 2026-07-14
[4]
NC State Extension — Tips for Effective Ant Baiting
Patience with slow-acting baits; do not disturb or spray baited ants
extensionverified 2026-07-14
[5]
UNH Cooperative Extension — Carpenter Ants Fact Sheet
Carpenter ants as a NH structural pest requiring a different approach than sweet liquid bait
extensionverified 2026-07-14
[6]
NPIC — Boric Acid General Fact Sheet
Borate mode of action as a stomach poison; efficacy sensitivity to concentration and moisture
npicverified 2026-07-14
[7]
Terro — Liquid Ant Baits (T300) product page
Station format, placement directions, labeled species list (facts only, not the efficacy verdict)
manufacturerverified 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

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Professional Pest Control

When Patient Baiting Still Isn't Enough

Liquid bait genuinely reaches a colony a spray can't — but a large, multi-satellite, or carpenter-ant colony can outgrow what a homeowner-scale program clears. 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 colony/nest treatment, not just more bait
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Keep Exploring

How to Use Terro Liquid Ant Baits (T300)

Does this product actually work?

What it is — and what it's really for

The technique walkthrough

Trace the trail before you place anything

Snap the tab and place stations flat, right on the trail

Remove competing food

Do not touch, move, or spray the stations once ants are feeding

Let the surge run its course

Refill or replace before a station runs dry