I spray apple cider vinegar full strength along baseboard and door sill as well as on my counter tops. Kills the ants and won't harm you. It lingers quite a while to keep them away.
Be aware that borax is a poison, and is not a relatively harmless substance just because you find it in the laundry room. You may poison something else with this as well. This is not to tell you not to use, just to say that it isn't that much more environmentally friendly than a pesticide you might purchase. You might also kill some bees or "friendly" insects like ladybugs, and you would not want it anywhere near food or where your pets might walk in it.
I use the little ant traps that look like little tin cans. I believe they also have a substance that the ants take back to the hill. Diatomaceous earth which is sold under a variety of names is a substance made from petrified seashells that will shred the ant's exoskeletons. Not a comfortable experience, I am sure, but it is non-toxic to pets and people.
If you want to kill them in the hill, the best pesticide I have used is the Raid spray foam. It is a bit pricey, but VERY effective. It, of course, is a poison.
A little line of talcom powder does it. Across the doorstep and along the walls where they are coming in. They won't cross it and it is harmless to everything.
I put borax and sugar in the blender to make a light powder. I place a teaspoon of this on every ant hill, where ever I see a line of ants, and about every eighteen inches all around the foundation of our house. Our neighborhood has been over run with ants. It has taken me about 4-5 years of doing this several times every summer.
The ants started thinning out after a couple of years, and this spring was the first time no ants came into our home (so far, I have not put any out). I have seen some ants in the yard though, and plan on putting some in the yard before they make it to the house.
No other method has worked for me. If you want immediate response, this is not the method for you - but I'd still use it along with any other method you choose. One note: the sugar actually attracts the ants, so don't be surprised to see lots more when you first put it out.
As soon as you see the first ant, put out a mixure of borax and sugar with enough water to make it liquid. I use an old can lid and put it down where I have seen the first ant. They will flock to the sugar, borax, water mix. Allow them to eat/drink their fill. In about three days you will not see anymore as they take this back to the nest and it will kill those in the nest, too.
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