Termites are invasive pests that cause considerable damage to homes across the country. Termite colonies are difficult to identify because their subterranean behavior shows few above-ground signs of their presence. To combat infestations, known or suspected, several chemical pesticides have been developed in recent years specifically designed to kill termites. The methods of application, as well as active ingredients and chemical reactions that kill termites, vary significantly.
Fipronil is the active ingredient in many liquid termite control products---the most common is Termidor. Fipronil is specially designed by biochemists to disrupt the central nervous system of termites that come in contact with the chemical; fipronil in high concentrations kills termites on contact. It is highly effective as a barrier treatment both during known infestations and as a preventive treatment around homes. Fipronil is dissolved in water and applied underground around the foundations of homes to create a protective barrier against termites.
Imidacloprid is a synthetic insecticide derived from nicotine and is the active ingredient of the underground termite chemical Premis. Imidacloprid is a deadly chemical that works by ingestion or by contact. The chemical binds to nicotinic receptors in the nervous system and causes continual signaling of those receptors, preventing the chemical from being broken down by the hosts immune system. Binding of imadacloprid is an irreversible, fatal process to termites. The chemical is slow acting, which allows termites who come in contact with low concentrations to transfer the toxin to other termites. If the infected termites find their way back to the queen, imidaclorprid will kill the entire colony as well as individuals causing damage to a home.
Hexaflumuron is a termiticide commonly used in termite baiting systems such as Sentricon. As opposed to liquid chemicals, hexaflumuron is an slow acting insect growth inhibitor that disrupts a termite's ability to shed its exoskeleton and continue to grow. Hexaflumuron is specifically designed for termite baiting systems and exploits the social behavior of termite colonies. When termites find the baiting stations, they leave chemical trails that inform other termites where the food source is located. As termites feed on hexaflumuron they are exposed to the chemical and carry it with them back to the colony, spreading the chemical to other termites they come in contact with. Eventually, once enough termites have fed on the chemical bait, the concentrations of hexaflumuron in the colony will be high enough that the queen will also receive the chemical and the colony will die. Because of its passive nature, hexaflumuron is considered a reduced-risk pesticide by the Environmental Protection Agency and is much less toxic to the surrounding environment than liquid pesticides.