Subterranean termites are the most important insect pest of wood in the United States. Living in large underground colonies, termites may attack any wood in contact with the soil and may even construct protective shelter tubes over nonwood materials to attack wood above ground. Most damage in the United States is caused by termites in the genus Reticulitermes, but an invasive termite, the Formosan subterranean termite (Coptotermes), causes extensive damage in some areas. Termites occur in all 50 States except Alaska but are most common in the Southern States. Termites prefer warm, moist environments, and home builders and homeowners often unwittingly increase the likelihood of termite infestations in homes and other structures by creating such environments. Termite prevention begins with good building practices, which vary depending on the type of structure and how the structure is to be landscaped and decorated. The use of soil-applied insecticides during construction is the most widely employed method of preventing termites and has a long history of success. Use of pressure-treated lumber is another successful practice, but termites may tunnel over treated wood to reach untreated wood elsewhere. Control of termites in existing structures involves periodic inspections for termite activity, remedial insecticide treatments, or use of insecticidal bait technology.