The fastest way to kill ants in your house is with bait, not spray. Spraying kills the ants you can see, but the colony (often thousands strong) keeps sending more. Bait works because foraging ants carry poisoned food back to the nest, where it spreads to the rest of the colony and eventually reaches the queen. Once she dies, the colony collapses. Getting there takes a bit of strategy, starting with figuring out what kind of ants you’re dealing with.
Identify the Ants First
Not all house ants eat the same thing, and using the wrong bait means they’ll walk right past it. The most common indoor species and their food preferences break down like this:
- Odorous house ants are about 1/8 inch long, dark brown to black, and smell like rotten coconut when crushed. They prefer sweets but occasionally go for protein.
- Pavement ants are slightly larger (3/16 inch), dark brown to black with two visible bumps between the thorax and abdomen. They eat sweets, proteins, and grease, making them relatively easy to bait.
- Pharaoh ants are tiny (1/16 inch) and yellow to orange. They favor fats and proteins over sugar. These ants are notorious in apartments and warm buildings, and spraying them can cause the colony to split into multiple new colonies, making the problem worse.
- Argentine ants are about 1/8 inch, dull brown, and form long, visible trails. They prefer sweets.
- Carpenter ants are the giants of the group, ranging from 1/4 to 1/2 inch, black or red-and-black. They don’t eat wood but excavate it to build nests, which means they can cause structural damage. They need a different approach (covered below).
If you’re seeing tiny ants trailing to something sweet on your counter, you’re likely dealing with odorous house ants or Argentine ants. If the ants are drawn to greasy food or pet food, pavement ants or pharaoh ants are more probable. Matching the bait to the diet is the single biggest factor in whether your approach works.
Why Bait Works Better Than Spray
When you spray a line of ants, you kill those individuals, but the queen is still laying eggs deep in the nest. The colony replaces its losses and sends out new foragers, often within days. Bait takes a completely different approach. A worker ant eats the bait, then carries it back to the nest and shares it mouth-to-mouth with other ants, a feeding behavior called trophallaxis. The poison is slow-acting enough that the forager makes several trips before dying, typically within about 48 hours. During that window, the bait spreads through the colony until it reaches the queen.
This is why you’ll actually see more ants at first after putting out bait. That’s a good sign. It means the foragers have found it and are recruiting others. Resist the urge to spray them or wipe up the trail. Let them feed and carry the bait home. Colony elimination can take anywhere from a few days to a couple of weeks depending on colony size.
Choosing and Placing Bait
Commercial bait stations are the easiest option. Liquid baits (gel or syrup in a small plastic station) work well for sugar-feeding ants. Protein and grease baits come in granular or solid form and are better for pharaoh ants or pavement ants. If the ants ignore your bait for more than a day or two, switch to the other type. Ant dietary preferences shift seasonally, so what worked last summer may not work now.
Place bait stations directly along the ant trails you’ve observed, especially near where the trail enters your home. Good spots include along baseboards, under sinks, behind appliances, and near cracks in the wall. Don’t clean up the scent trail before placing bait. The ants are following that chemical path, and you want them to find the bait along it. Put out multiple stations rather than one. More access points mean faster colony uptake.
DIY Boric Acid Bait
You can make an effective sugar bait at home using boric acid powder. The University of Hawai’i’s tested recipe calls for 1 teaspoon of boric acid powder and 3 tablespoons of white sugar dissolved in about 1 3/4 cups of warm distilled or bottled water (tap water can contain minerals that reduce effectiveness). Soak cotton balls in the solution and place them in shallow containers near ant trails.
The key with DIY bait is keeping the boric acid concentration low enough that ants survive long enough to share it. Too much boric acid kills foragers on the spot, turning your bait into an expensive spray. This recipe gets the ratio right. Be patient with it. The University of Hawai’i recommends allowing ants to feed at bait stations for up to one or even two months for full colony elimination.
Dealing With Carpenter Ants
Carpenter ants require a more aggressive response than typical sugar ants because they damage the wood in your home. They don’t eat wood like termites do. Instead, they hollow out cavities to build nests, preferring water-damaged or damp wood in crawl spaces, attics, and walls. The telltale sign is small piles of fine sawdust (frass) near baseboards, window frames, or wooden structures.
If you’re finding large black ants and sawdust piles, the priority is locating the nest. Check areas with moisture problems: around leaking pipes, in water-damaged walls, near poorly ventilated crawl spaces. Woodpiles stored against the house are common nest sites.
Surface sprays alone won’t solve a carpenter ant problem. Oregon State University recommends hiring a professional pest control service for carpenter ants or any wood-destroying insect, because the nest often needs to be located within wall voids or structural wood. Professionals typically treat the foundation and surrounding soil with insecticides or use specialized baits to reach the colony. On your end, the critical steps are fixing leaks, replacing damaged wood, ensuring no wood contacts soil directly, sealing exterior entry points, and moving firewood piles away from the house.
Safety Around Pets and Children
Most commercial ant baits contain very low concentrations of active ingredients, but placement matters. Bait stations should go in spots pets and toddlers can’t reach: behind heavy appliances, on high ledges, inside cabinets, or under furniture that’s flush to the wall.
Boron-based baits (borax, boric acid) are relatively low-risk for dogs and cats in small amounts, though large ingestions can cause stomach upset and, rarely, kidney problems. Fipronil-based baits contain a neurotoxin, but the amount in household ant baits is generally too low to harm dogs or cats. Rabbits, however, are extremely sensitive to fipronil, and any exposure should be treated as serious.
If you have cats, avoid pyrethroid-based sprays and products (common active ingredients include bifenthrin, permethrin, and tetramethrin). Cats are highly sensitive to pyrethroids and can become seriously ill from small exposures. Dogs tolerate pyrethroids better, but concentrated products that require dilution before use are still a concern. Beyond the poison itself, dogs sometimes chew and swallow bait station packaging, which can cause intestinal blockages. Enclosed bait stations designed to resist tampering are worth the extra cost in homes with pets.
Keeping Ants From Coming Back
Killing the current colony solves today’s problem. Keeping ants out long-term requires two things: cutting off entry points and removing what attracted them in the first place.
Ants enter through remarkably small gaps. Inspect your home for cracks in walls and foundations, gaps around windows and doors, openings where pipes and cables pass through exterior walls, and spaces around vents and air conditioning units. Areas near faucets and plumbing penetrations are especially common entry points because ants are drawn to moisture. Use silicone or acrylic latex caulk for cracks around windows, doors, and foundations. Expandable foam sealant works for larger gaps around utility lines. Fine mesh screens over vents keep ants out while maintaining airflow, and weatherstripping around doors and windows closes the gaps that caulk can’t reach.
Inside, the basics matter more than any product you can buy. Store food in sealed containers, wipe down counters and stovetops after cooking, clean up pet food bowls rather than leaving them out overnight, and take out garbage regularly. Fix dripping faucets and eliminate standing water, since many ant species are as attracted to moisture as they are to food. A clean, dry home with sealed entry points gives ants very little reason to come inside, and if a scout does find its way in, there’s nothing worth reporting back to the colony about.