All drywood termite control methods can be categorized as either whole-structure or localized. A whole-structure treatment is defined as the simultaneous treatment of all infestations, accessible and inaccessible, in a structure. A localized or spot treatment is more restrictive, often applied to a single board or small group of boards. |
Whole-structure treatments have an advantage over spot treatments in that they can eliminate all infestations, even hidden ones. With the uncertainty of current detection methods, particularly when drywall or other wall coverings conceal infestations, there is always some doubt as to the extent of dry-wood termite colony boundaries within homes. Consequently one can never be sure that all infestations have been treated when applying spot treatments.
Fumigants (sulfuryl fluoride) treat all infestations simultaneously and have high levels of efficacy if correctly applied. Sulfuryl fluoride kills drywood termites in about 3 days. A monitored fumigation, which involves installing gas monitoring lines inside the structure undergoing treatment, has the highest rate of treatment success.
Heat is a nonchemical option for whole-structure treatments. Excessive heat kills drywood termites by disrupting cellular membranes and denaturing enzymes needed for their survival. The treatment process involves heating all wood in the structure to a minimum of 120°F and holding this temperature for at least 33 minutes. The benefit of heat treatment is the ability to treat the entire structure without the use of chemicals and the relatively short period of time the structure must be vacated (hours instead of days, as with the use of fumigants). An additional advantage is that portions of large structures can be treated separately, which is very useful in apartments and condominiums. The major drawbacks of heat treatments include the difficulty in raising the internal core temperature of large structural beams that are infested and heat sinks, which are areas within the structure that are difficult to heat, such as wood on concrete or tile. As more powerful and efficient heaters are developed, larger homes can be efficiently treated with heat.
Localized or Spot Treatments
There are many localized/spot treatment methods available that include both chemical and nonchemical options. The chemical options include aerosol pyrethrum and aerosol and liquid pyrethroids (cyfluthrin, permethrin, bifenthrin), liquid imidacloprid, liquid nitrogen, and liquid and dust formulations of disodium octaborate tetrahydrate. Chemicals that have been phased out of commercial use include organophosphates, carbamates, silica-gel, and dri-die. For liquid and dust insecticides to be effective, termites must touch or ingest them. Spot treatments should be applied only by licensed applicators. Home use products are not effective.
High voltage electricity, or electrocution, is another nonchemical option for controlling drywood termites. The device currently marketed uses high voltage (90,000 volts) but low current (less than 0.5 amps). Death to drywood termites occurs by electric shock, although delayed mortality may also occur from the destruction of intestinal protozoa. The advantage of electrocution is that the equipment is portable. The limitations include detection accuracy and the possible reduced efficacy from the interfering actions of common building materials, for example metal, concrete, and glass. If drill holes are used to enhance the flow of current into wood, damage occurs to wall coverings, walls, and structural wood members.
Wood replacement is another remedial treatment option. However, similar to other spot treatments, its effectiveness is highly dependent on detection accuracy and extent and location of the infestation, and it may be expensive to accomplish.
When planning treatment for drywood termites, consider whether the whole structure is to be treated or just localized areas. Localized/spot treatment methods make it more difficult to ensure complete control because of the difficulty in determining the extent of a drywood termite infestation.
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