Many insects can be controlled in this manner and it is a very surgical and self contained method of treatment using very little insecticide. Pests such as gypsy moths and emerald ash borers can be eliminated this way.
This treatment is performed by carefully drilling into the base of the tree, capping the hole with a capsule, and then finally putting the material into the capsule through the use of a specialized injection tool. The material is then distributed throughout the entire canopy by the tree itself!
One huge benefit of this type of treatment is the very low amount of insecticide that is needed for the service.