Control of the subterranean termite consists primarily of destroying the tubes and then preventing the termites from reaching the foundation by physical and/or chemical barriers. Fumigation is never used as a control. |
The subterranean and the drywood termites. Wood is their food source. Both can do great damage to the structural timbers in a residence but the two have different methods of attack. Although the focus of this article is on the drywood termite, familiarity with the subterranean termite is needed.
Once they are positively detected, several methods of control are available. Fumigation has been the primary method. The structure is tented or "bagged" and chemicals are released inside. After 24 hours the structure is allowed to air out.
ALTERNATIVE METHODS OF CONTROLLING DRYWOOD TERMITES
The primary methods of control are of three types: 1) killing termites harbored in wood; 2) physical and chemical barriers and 3) removal of infested wood.
Methods used to control (kill) termites in existing structures. Heat
Termites can only survive in a narrow range of temperatures. They are protected from wide variations while inside their micro-habitats. Methods have been developed that heat the infested wood above the level in which the termites can survive. The structure may be "bagged" or tented, or an individual room sealed off. In order to be effective the lethal temperatures must be maintained long enough to kill the insects. The method relies on the use of propane burners to heat the air that is then blown into the structure. The goal is to heat the structure so that the temperature inside the infested wood is heated to 120 degrees and maintained for at least 30 minutes. Usually the structure must be heated to 170-180 degrees from several hours up to a day to ensure reaching the optimum temperature inside the wood where the termites are hidden. Cold
Chilling, the reverse of heat, is used as a method to kill drywood termites. Cold, by its very nature, is limited in usage to small areas. Liquid nitrogen is used to lower the temperatures to 20 degrees below zero long enough to kill the termites inside the wood. The liquid nitrogen is pumped into the infested areas, turns into a gas, and chilling the surrounding area. This method of treatment does not release any gases not already found in the atmosphere. The wood must be chilled to -20 degrees for thirty minutes to kill the termites. The area to be treated may be covered with insulating mats to increase efficiency. Many of the concerns regarding the effectiveness of cold are similar to those listed for heat fumigation. Efficacy in pest control of drywood termites is directly related to finding the nests or colonies.
Factors to be considered when treating wood with borate include the wood species, age of the tree when cut for lumber, location of the board within the tree, geographic location of the tree, humidity, moisture content of the wood to be treated as the drier wood accepts more borate but the moist wood allows the borate to penetrate deeper and surface texture. Repeated aqueous solutions mean more loading of borate in the wood and deeper penetration.
Borate treatments differ in the type of construction used in the structure. Slab structures, sealed walls, hidden sill plates or studs, all affect the course of treatment. The most effective treatments are noted in areas with large amounts of bare wood, such as attics, garages, crawl spaces and unfinished basements. The applicators must treat not only the areas of suspected termite infestations but surrounding areas as well to prevent termite migrations. The more surface area treated, the greater control and the increased possibility of prevention.
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