Most ants build nests outdoors in the ground. Workers leave the nest to search for food throughout the landscape and occasionally in homes. Storing food securely and good sanitation helps make homes less attractive to foraging ants. Sealing cracks and openings where ants may enter a home also helps to keep them outdoors.
When ants invade your home wipe them up with soapy water. Look for the place where ants are entering your home and caulk or seal it to keep ants out. If ants continue to enter your home apply an insecticide labeled for ant control outdoors at the spot where they are entering.
Using ant stakes and other bait products is the safest way to control ants outdoors. Baits are formulated as solids or liquids and applied in stations or in the case of granules by broadcasting them. Ants are attracted to the bait and carry small portions of it back to the nest where it is given to other workers, larvae, and reproductive forms. To achieve wide distribution of the bait so the entire colony will be killed, the bait toxicant must be slow acting.
Some examples of toxicants used in ant baits are hydramethylnon, boric acid, and fipronil. Hydramethylnon is photodegradable. If it is broadcast in granular form it should be applied in the evening. Boric acid is most effective at concentrations of 1 percent or lower. Fipronil is a new class of toxicant that is effective against ants at ultra-low doses. For more information, see
UC Pest Notes #7411 Ants, http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7411.html
UC Pest Note #7487 Red Imported Fire Ants, http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7487.html
UC Pest Note #7416 Carpenter Ants at http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7416.html
By V. Lazaneo, Urban Horticulture Advisor, Emeritus, UC Cooperative Extension, August 2012