The most effective way to kill ants is with bait, not spray. Baits work slowly on purpose: foraging ants carry poisoned food back to the colony, where it spreads to the queen and the rest of the nest. Sprays kill the ants you can see but leave thousands more breeding behind the walls. Choosing the right product depends on the type of ant, where they are, and whether you have pets or small children in the house.
Why Bait Works Better Than Spray
When you spray a line of ants on your kitchen counter, you’re killing maybe 10% of the colony. The queen keeps laying eggs, and new foragers replace the dead ones within days. Bait takes a completely different approach. The active ingredient is mixed into something sweet or oily that ants want to eat. They carry it home, feed it to nestmates and larvae, and the poison spreads through the colony from the inside out.
This process isn’t instant. Bait manufacturers note it can take days to weeks for ants to completely disappear from an area. That delay is a feature. If the poison killed too fast, the forager would die before making it back to the nest, and you’d be right back where you started. The goal is colony elimination, not just killing the scouts in your kitchen.
Store-Bought Baits and What’s in Them
Most commercial ant baits use one of a few active ingredients. Boric acid (borax) works as a stomach poison, disrupting the ant’s digestive system. Fipronil and indoxacarb target the nervous system, causing paralysis and death. All three are designed to act slowly enough that ants survive the trip back to the colony before symptoms set in.
Gel baits and liquid bait stations are the two most common formats. Liquid baits work especially well for the small, sweet-seeking ants (often called sugar ants) that invade kitchens. Gel baits can be applied in cracks, behind appliances, and along baseboards where ants travel. For the best results, place baits directly on or very near the ant trails you’ve already spotted. Resist the urge to kill the ants you see traveling to the bait. Those are your delivery system.
Homemade Borax Bait
If you’d rather mix your own, a simple borax and sugar solution is one of the most reliable DIY options. The University of Hawaiʻi’s College of Tropical Agriculture recommends this recipe:
- 1 teaspoon boric acid powder
- 3 tablespoons white table sugar
- Warm distilled or bottled water, filled to 1¾ cups
Stir until the sugar and boric acid dissolve completely. Soak cotton balls in the solution and place them near ant trails, or pour small amounts into shallow lids. The low concentration of boric acid (under 1%) is key. Too much borax and the ants die before reaching the colony. Too little and it won’t kill them at all. This recipe hits the sweet spot where ants feed freely and carry the poison home.
One important note: use distilled or bottled water, not tap. Minerals in tap water can affect the solution. Replace the cotton balls every few days, since the sugar water will dry out or grow mold.
Matching the Bait to the Ant
Not all ants want the same food, and using the wrong bait is a common reason people think baiting doesn’t work. The tiny ants raiding your sugar bowl are typically attracted to sweet, liquid baits. Carpenter ants, the larger black ants that nest in damp or damaged wood, have broader tastes. UC Integrated Pest Management recommends first attracting carpenter ants to a nontoxic food like a sugar-milk solution or even sliced crickets. Once they’re feeding reliably, swap in a toxic bait. This two-step process helps you confirm the ants will actually eat what you’re offering before you commit to a product.
If you’re not sure which species you’re dealing with, put out both a sweet bait and a protein or grease-based bait near the trail. Whichever one the ants flock to tells you what they’re craving, and that’s the format to stick with.
Diatomaceous Earth for Contact Killing
Food-grade diatomaceous earth (DE) kills ants through a mechanical process rather than a chemical one. The powder is made of fossilized algae with microscopic sharp edges. When ants crawl through it, those edges cut into their exoskeleton, causing them to lose moisture rapidly and die from dehydration.
To use it effectively, sprinkle a thin, even layer along ant trails, around entry points like baseboards and windowsills, and near any nests you can find outdoors. A light dusting works better than a thick pile. Ants will walk around a visible mound of powder, but they’ll cross a thin layer without detecting it. Outdoors, apply it around garden beds, the base of plants, and patio edges.
The main limitation is moisture. DE loses its effectiveness when wet and needs to be reapplied after rain or watering. Indoors, vacuum up the old layer and reapply every few days until ant activity stops. Unlike bait, DE only kills ants that physically contact it. It won’t eliminate a colony on its own, but it’s useful as a chemical-free barrier at entry points while baits do the deeper work.
Safety Around Pets and Children
Most household ant baits contain very low concentrations of active ingredients, and small, incidental exposures are rarely dangerous for dogs or cats. Borax-based baits are relatively safe in small amounts, though large ingestions can cause stomach upset and, in rare cases, kidney problems. Fipronil-based baits are formulated at doses too low to affect most dogs and cats, but rabbits are extremely sensitive to fipronil, and any exposure should be treated as an emergency.
Cats deserve special attention. Pyrethroid-based sprays, which include ingredients like permethrin and bifenthrin, can cause serious neurological symptoms in cats even at small doses. If you have cats, avoid pyrethroid-containing products entirely. Cats can also be exposed indirectly by walking across treated surfaces and then grooming their paws.
Dogs are the bigger concern with bait stations simply because they’re less picky eaters. The sweet taste that attracts ants also attracts dogs, and chewing on the plastic casing creates a choking or obstruction risk on top of any chemical exposure. Place bait stations in spots your dog physically cannot reach: behind heavy appliances, on high ledges, inside cabinets, or beneath furniture with clearance too low for a snout. Store unused products in a locked cabinet.
Sealing Entry Points to Prevent Return
Killing the current colony solves the immediate problem, but ants from neighboring colonies will find the same entry points if you leave them open. Walk the perimeter of your home and look for gaps around doors, windows, and the foundation. Seal cracks with caulk, paying special attention to where utility pipes and wires enter the house. These are highways for ants.
Indoors, clean up the invisible trails ants leave behind. Foraging ants deposit chemical scent trails that guide other workers to food sources. Wiping down surfaces with soapy water or a vinegar solution disrupts those trails and makes your home less attractive to new scouts. Keep food in sealed containers, clean up crumbs promptly, and fix any leaky pipes. Ants need water as much as food, and a dripping faucet under the sink is an open invitation.
For longer-term perimeter defense, barrier sprays applied around your home’s foundation, doors, and windows create a chemical boundary that repels or kills ants before they get inside. These products typically last several weeks before needing reapplication, and they work well as a complement to indoor baiting rather than a replacement for it.