There are many insecticides labelled for ant control. Before using an insecticide, always read the label, follow directions and safety precautions. Bait and granular formulations are usually not highly effective against carpenter ants. Dusts, wettable powders, injections, and sprayables are better. It is often best to employ a licensed pest control firm, especially where nests are hard to find.
Some firms attempt to locate the nest or nests and treat only in suspected places.
Others drill and dust potential nesting sites. Most apply a perimeter spray treatment around the house foundation. Avoid simply spraying each month whenever ants are seen. Infestations will continue unless nests are eliminated. Locating the nest is not always easy, but is essential for control.