Ants in your garden, no problem; ants in your house, big problem. We’ve used this technique in our own homes and found it works every time.
1. Make a solution of 1 percent boric acid (available at any drugstore) and 20 percent sugar by thoroughly dissolving 1 teaspoon of boric acid and 6 tablespoons of sugar in 2 cups of water. Use a clear jar so you can see when all the boric acid crystals are dissolved. Soak cotton balls in this bait solution.
2. Make bait dispensers out of old plastic containers with lids. Punch holes in them so the ants can get inside, then put the soaked cotton balls into the containers and cover them with lids so the bait won’t dry out.
3. Place the bait containers wherever you see ant trails, in or outside the house.
4. Clean the containers and use fresh bait solution at least once a week.
5. Be patient! The key is to get worker ants to continually carry low doses of boric acid back to feed the ants in their nest. Boric acid is mildly repellent to ants, and using a very low dose makes it more likely that surviving ants will continue eating the bait and taking it back to the nest.