Boric acid is a slow-acting insecticide. It works on the insects through their digestive system, so the insects have to eat it in order for it to work.
Many people apply boric acid powder in areas where they have been seeing Argentine ants. The people are often disappointed because the ants keep coming back. The reason for this is that the Argentine ant colony has thousands of members, but only a small number of workers are sent out to look for food at a time.
If the foraging workers do not come back, the colony sends out another group. In the meantime, there are many queens in the colony. The queens are constantly producing eggs to replace any workers that die.
A more effective way to deliver boric acid to Argentine ants is in ant bait. Ant bait is made from a food that the ants will accept. The bait has a small amount of boric acid mixed into it. The workers take the bait back to the nest and share it with all of the other ants.
The first step in controlling Argentine ants is to inspect carefully. Follow the trails of workers to find the nests. Argentine ants often make satellite nests, so it is important to find as many of their locations as possible. Put the ant bait beside the trails so the workers can find it easily. Make sure that children and pets cannot reach the ant bait.
Because the Argentine ant colonies are very large, it is important to use plenty of ant bait. If any of the queens survive the treatment, they will produce enough eggs that the ant population will be back to the original size in a short time.
After all of the ant activity has ceased, boric acid dust can be applied into the weep holes and the voids of exterior walls. This can help prevent future Argentine ants from entering the home. Put firewood up on a rack and store it away from the foundation. Rake mulch and dead leaves away from the foundation to make a clear space that is 12″ to 24″ wide. This will help discourage Argentine ants from nesting next to the foundation and entering the home.