How to Get Rid of Ants, and Why Spraying Makes It Worse

The short answer

Put slow-acting bait on the ant trail and leave it alone. Do not spray the trail with a contact killer. That is the whole pitch. Spraying the foragers you can see kills them and leaves the colony, the brood, and the queens intact, and in some species a stressed colony splits into subcolonies that start fresh trails in other rooms. That is why a can of spray seems to work for a day and then the kitchen is worse. University of California IPM is direct: baits are “the only type of insecticide recommended in most situations” because “the pesticide must be slow-acting so workers won’t be killed before they get back to the nest,” and that is how the toxin reaches the workers that stay home and the queens that lay the eggs.

For a typical small-ant problem (Argentine, odorous house, pavement) pick up a borate gel or liquid bait station. Refillable stations are mid-tier pricing, disposable ones are budget. Place the bait on the trail, not where you think the ants ought to go.

Which bait, where it goes

Sweet-feeders, which is most household ants year-round, take sugar-based gel or borate-in-sugar-water bait. If sweet bait is being ignored for several days, switch to a protein or peanut-oil bait - pharaoh and thief ants “prefer protein or greasy baits year-round,” and Argentine ants swing toward protein in spring.

• Liquid borate bait stations (refillable). UC IPM says liquid borate baits at 0.5 to 1% borate in sugar water solution, in refillable stations, “are best for severe Argentine ant infestations”. Note the word severe: this is the answer to a trail that will not quit, not the opening move. Best in kitchens and baths where you can keep an eye on them. Replace the bait when it is empty.
• Pre-filled gel or granule stations (disposable). Easier cleanup, less precise placement. Fine for a one-off job.
• Protein or grease bait. Use when sweet bait is going untouched.

Set bait across the trail where the ants enter the room (under the door, along the baseboard, beside the window), not in the middle of the counter. Replace every one to two weeks until the trail dies.

What “identification-lite” buys you

You do not need an entomologist. Three things change what to do:

• Tiny ants (about 1/8 inch, dull brown, sweet-feeding). Almost always Argentine or a similar small household ant. Sweet bait, repeat.
• Larger ants (1/4 to 1/2 inch long, black or red-and-black, shiny). Carpenter ant territory. They excavate damp or rotting wood to nest, and Penn State Extension says it is “unlikely that the satellite colony can be eliminated without the use of one or more of the materials applied by professional pest management companies.” See “When to call a pro.”
• Trail fragments into multiple trails after you sprayed. That is budding. Maryland Extension flags pharaoh ants specifically: their large colonies “can fragment into subcolonies when stressed by repellent insecticides.” Stop spraying, switch to bait only, and reset the clock. The spray is what made it worse.

The mistake almost everyone makes

Three mistakes, all from the same reflex to act fast:

• Spraying the trail. Kills foragers only, leaves the colony and queens. UC IPM is blunt: spraying “won’t provide permanent control, because it kills only foraging ants without killing the colony and the queens.”
• Wiping the trail the moment bait goes down. You want those same ants to walk into the bait. Wipe the counter, leave the trail. Maryland Extension: “don’t clean around bait stations - this discourages ants from feeding.”
• Switching bait daily because “nothing is happening.” Bait works in days, not hours. Give it a week.

What actually ends it: sanitation and exclusion

Bait clears the ants inside. It does not stop the next wave. UC IPM and Maryland Extension both put sanitation first:

• Cut off food and water. Airtight containers, no dirty dishes overnight, fix any drip under sinks or at the fridge.
• Trim back the outside route. Mulch, firewood, and dense vegetation held against the foundation are a covered highway in. Pull them back. Caulk obvious entry points where pipes and wires come through walls.
• Wipe the trail only after a week of baiting, not before. The trail is how the workers find the bait.

Do that and the bait becomes a one-time cleanup, not a monthly ritual.

When to call a pro

If the ants are 1/4 to 1/2 inch long and black or red-and-black, tell a licensed pest professional you suspect carpenter ants. Penn State notes satellite colonies “must be destroyed, or the ants will reappear in a few days or weeks,” and the bait and spray available to a homeowner are usually not enough. Same answer if you see piles of coarse sawdust-like frass near baseboards or window frames (the satellite-nest tell), if baiting and sanitation have not reduced the trail after three to four weeks, if ants are active in multiple rooms at once (often a pharaoh-ant budding problem), or if there is a large mound outdoors at the foundation. A pro can identify the species, treat satellite nests in wall voids, and place tamper-resistant bait where pets and children cannot reach it.