Subterranean termites make their home in a large community nest in the soil beneath structures where they consume wood as their primary source of food. They cause more than $2 billion in structural damage across the United States each year, according to Texas A & M University. Applying residual chemicals to the soil prior to building can help prevent or limit infestations.
Prior to 1988, the soil around and under homes could be treated with chlorinated hydrocarbons, such as chlordane or heptachlor, that successfully prevented termites for 30 to 40 years. Production and use of chlordane ceased in 1988 in the United States, according to the Centers for Disease Control and Prevention.The use of heptachlor also ceased in 1988 due to its inability to break down in the soil. It was also shown to build up in animal fat. The chemical was banned for use in the United States, except when used to commercially keep fire ants out of transformers.
Prior to building, repellent termiticides (termite-specific insecticides) can successfully be applied to the soil to help prevent subterranean termites from invading the wood of the newly built structure. In many locations of the country, pretreatment of soil is required prior to building. The soil beneath all concrete slabs receive pretreatment. The treatment focuses on treating the soil where horizontal and vertical slabs are placed during the building process. Repellent termiticides are normally made from pyrethroids (insect-killing chemicals).
Solutions for Pre-existing Structures
The soil of pre-existing structures can be treated by applying termiticide in a trench around the exterior of the building's foundation and within the interior of the foundation. Termiticide can also be injected into the soil under slabs using long pipes. Soil around fireplaces, under porches, along patios and beside or beneath concrete walkways should also receive treatment.
Types of Termiticide
Repellent soil termiticide don't actually kill termites. It simply repels termites over a certain time, depending upon the repellent being used. Nonrepellent termiticide kill termites when they tunnel through the dirt containing the pesticide. The termites inadvertently ingest it when they return to their nest and practice communal grooming. Foam repellents are often injected beneath porches into soil pockets. The foam expands to fill the soil pocket with the pesticide that sticks to any termites that come into contact.
Application of soil termiticide treatments are illegal for a homeowner to perform in many states and require a professional pest control operator. Success requires extensive pesticide application equipment, such as drills, pressure-generating pumps, pressure injectors and high-gallon tanks. Application of liquid termiticides to soil within 50 feet of wells, cisterns, streams and bodies of water requires professional handling, according to the Virginia Cooperative Extension. Instead, a professional must remove the soil, apply special termiticides, dry the soil and then reapply. Despite these precautions, the pesticide can still leech out of the soil into surrounding water.