Carpenter ants, termites and other critters that break down old wood are vital parts of the environment, but around the home they can be pests. A carpenter ant infestation in a nearby tree can bring trails of ants foraging into your house, and can lead to satellite colonies taking up residence in your walls.
Find the carpenter ant colony. Look for a small pile of sawdust next to an opening in an old, dead or dying tree. You can also watch carpenter ants and try to follow their trail back to the carpenter colony. If you opt to track them, you may have to hunt them after midnight with a flashlight because this is when they are most active.
Apply a dust insecticide such as rotenone to the entrance of the colony. The package the dust insecticide came in should have directions about how much to use and whether or not to reapply it.
Apply a transfer liquid insecticide in an outdoor area the ants will walk over if you suspect there are multiple carpenter colonies or are unable to locate the carpenter ant colony. A transfer liquid insecticide is an insecticide that does not kill the insects immediately, allowing them to transfer it to the rest of the colony, killing many more carpenter ants in the process. Pour the liquid over an area of ground you have seen the carpenter ants walking on so that they will track it back to the colony.
Dig out dead tree stumps and trees and remove rotting wood from around your house. This will decrease the chance of carpenter ant reinfestation.