Ants are pesky little creatures that seem to infest everything. However, some are beneficial, as they eat other insects, reduce organic matter and keep the soil aerated. In spite of this, ants can injure trees, plants and shrubs, causing them to die. Several methods are available to eliminate ants in trees, including those in pots.
Mix approximately 30 drops of essential peppermint oil into one gallon of water. Add to a sprayer container and completely spray the trees with the mixture. Ants do not like peppermint and will travel on.
Mix one part boric acid to two parts cornmeal or baby powder and sprinkle around the bases of the trees. Ants will not cross the mixture to get to the tree. Keep in mind, though, that they will still travel from electrical wires or limbs from other trees if they are touching each other. Trim the tree away from anything the ants may travel on first.
Spray boiling water on trees to kill ants that are presently there. This method will require additional application of other methods to keep the ants from returning.
Remove a potted tree from the pot and completely wash the root ball and pot free of dirt and ants with the water hose. This needs to be done outside of the yard area to avoid reinfesting the yard. Replant the tree in the pot with new soil.
Apply a thick coating of petroleum jelly around the base of smaller trees. Ants will not travel across the petroleum jelly.
Apply chemical pesticides according to package directions as a last resort. While the natural methods may not be as effective as chemical pesticides, they are much better for the environment.