If you've noticed black ants in or around your house, there is a good chance they are carpenter ants. Carpenter ants are typically between 1/4-inch and 1/2-inch long and make their nests in hollowed out areas of trees. If a carpenter ant colony makes its nest in a tree close to your home, you can expect to see the ants scurrying around on your floor. The ants will make satellite colonies around your home to supplement the main nest in the tree. The best way to get rid of the ants is to locate the nest and use pesticides to kill the colony.
Find the ant nest. Squirt some honey on the back of two or three index cards. Place the index cards outside where you have seen heavy ant activity. The ants will feed on the honey and then take it back to their tree nest. Follow the trail of ants to the tree in which they have made their nest.
Cut any branches from the tree that are touching your home. The ants use the branches as bridges to your house. They will use them as escape routes once you begin treating the tree. Use pruning shears to cut the branches back several feet from your house.
Place ant bait traps around the tree. The ants will feed on the poison bait and take it back to the colony inside the tree. The bait will kill many of the ants in the nest. Bait traps are unlikely to kill the entire colony, so use the traps as supplements to treating the nest in the tree itself.
Spray the area around the tree with a garden hose. Carpenter ants follow the scent of pheromones. If you wash away the scent trails, it will confuse the ants. This is especially useful if the ants have been traveling from the tree nest into your home. The ants will want to leave the nest once you treat the tree, but they will have difficulty finding their way back into your home without the scent trail. Spray all of the soil between the tree and your home to wash away the scent trails.
Dust the tree with a pesticide powder, such as Sevin Dust. Look for hollow cavities inside the tree and apply generous amounts of the powder. Boric acid also works well for treating the tree nest, and it is sometimes available in squeeze bottles that allow you to squirt the powder directly into small holes. Spread a generous amount of the powder around the base of the tree so any ants leaving the nest will become coated with the pesticide.
Spray the tree with liquid pesticide. Liquid pesticides do not last as long as powder, but can soak into the tree and kill ants further inside the tree. You can drill several holes into the tree and spray the pesticide directly into the holes. Try to drill into dead, crumbling areas of the tree and not into the healthy, firmer areas.