Upon seeing the first ant enter my home in mid to late spring, I immediately take action. My first move is sprinkle sage in all window seals and doorways. Ants despise the aromatic spice, and usually will not enter if it is present. Some people even grow it around their houses, or in a kitchen window seal garden to keep ants from coming in.
So why do ants not seem to like the herb sage?
I believe ants dislike sage because it confuses them for some reason. Upon finding a large group of them on the kitchen counter, I immediately sprinkled sage right where they were congregating. The result looked like mass confusion.
Perhaps this is because a part of ant’s communication with one another is through the use of pheromones trails that other ants can follow. It could be that the strong scent of sage disturbs these chemical trails, and thwarts their intended mission, leaving them confused as to were to go. That is certainly what it looks like, at any rate.
Various ways to use boric acid in conjunction with sage
My second line of defense, to be sure none of the pesky little buggers are still in the house, is to lightly dust, particularly in the kitchens and bathrooms (where they seem to head), with a very fine mist of boric acid. Many people make the mistake of putting out lines of boric acid around floorboards and molding.
This must be done in a very fine mist instead, for otherwise the ants will see it, and simply avoid it. However, if they do not see it, and walk through it, they take this deadly poison (to them, at least) back to their colony, where it hopefully prevents the rest of the colony from an attempted invasion!
Most people suggest making ant bait, by mixing boric acid with sugar or peanut butter, or some such, which does work quite well, if the ants take the mixture back to their queen. I have mixed it with cola of some type before, and that works on the few that are in the house. It seems to give them a fatal case of indigestion.
Still, I have found this to be unnecessary, as long as I have the sage sprinkled about doors and windows properly. You can also sprinkle it around the outside perimeter of your house, and though it takes a good deal of sage, this is very effective.
Additional sources : Over 20 years of study and experimentation with herbs, and common daily household usage.