Drywood Termite Detection & Treatment
Spring time, especially a warm, sunny day following rain, is the optimal time for termite swarming behavior and, at least for brief moments during the day, a chance to see live termites and perhaps a specific location where they are emerging from in the home. Since most soil around a home has buried cellulose debris (roots, stumps, or fence posts), finding swarming termites in your yard doesn’t necessarily mean your house has termites.
During a structural inspection for drywood termites, inspectors look for feeding damage, shed wings, fecal pellets, and kickout holes, i.e. small holes (less than 2mm in diameter) through which termites push fecal pellets out of the wood. However, it is not possible to determine, from fecal pellets alone, whether the infestation is currently active or how extensively the infestation extends throughout the wooden piece or structure. The final confirmation of drywood termite pellet identification from other wood destroying pests or wood debris may require help from an expert. Cleaning up the fecal pellets around a kickout hole and checking a few days later to see if new pellets have appeared can help to determine if an infestation is active (as building vibrations and movement may also cause some pellets to appear).
Only a full inspection from a certified inspector can determine if you have an infestation and the most appropriate treatment. Below are some of the potential treatment options:
There are many localized treatment methods available that include both chemical and nonchemical options. For liquid and dust insecticides to be effective, termites must make contact with them or ingest them. Localized treatments should be applied only by licensed applicators. Home-use products are not effective.
Wood injection or "drill-and-treat" applications have been used since the 1920s to treat drywood termite infestations which are accessible and detectable. An insecticide is injected into small holes drilled through any wood surface into termite galleries delivering the treatment directly to the pest population. This is the simplest and most direct method of treatment. The amount of drilling required and the effectiveness of this treatment depends on the chemical used and the nature of the infestation. Most chemicals will remain active in the wood after treatment to thwart resurgent colonies.
Spray and foam applications of products containing boron salts are applied to raw, uncoated wood surfaces. Because penetration depths of borate solutions and depth of drywood termite galleries vary, injection into existing infestations should also be performed.
Microwave energy, applied to relatively small sections of infested wood, kills termites by heating them. Thermocouples should be inserted into treated members to insure that adequate microwave energy is delivered. Microwave equipment is not designed to treat areas where access is limited.
The probe of a hand-held "gun" is passed slowly over the infested wood surface and inserted directly into pellet "kick-out" holes. The high voltage and low current energy emitted by the probe electrocutes termites in the immediate application area. There is no way to measure a lethal dose at a given location in wood with this device. In some cases, holes must be drilled into wood and wires inserted to improve penetration.
This method allows for absolute removal of a drywood termite infestation if it is isolated to a wood member which can be detached relatively easily, as for example, a door. Make certain that there are no galleries leading to adjacent wood members, otherwise, they will also require treatment or removal.
Sulfuryl fluoride kills drywood termites within several days. A monitored fumigation, which involves installing gas monitoring lines inside the structure undergoing treatment, has the highest rate of treatment success. Nonmonitored fumigation may not have enough gas concentration to kill infestations, and failures may occur. The advantage of fumigation over localized treatment is that it should eliminate infestations hidden from view. It will also be necessary for the occupants, pets, and plants to vacate the structure for several days (depending on volume of structure and amount of gas injected) while it is being fumigated and then aerated.
Heat is a nonchemical option for whole-structure treatment. 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 using chemicals and the relatively short period of time the structure must be vacated—hours instead of days, as with fumigation. The major drawbacks of heat treatments include the difficulty in raising the internal core temperature of large infested structural beams (could take many hours or days depending on wood volume treated) and the potential for heat sinks, areas within the structure that are difficult to heat such as wood on concrete or tile. The ability of these heating devices to rid all infestations from large structures with many layers of wall coverings still remains unclear. Other issues to consider include damage to heat-sensitive items in homes, including plastics (e.g. electrical outlet covers) and cable wiring.
Heat treatments are used to eradicate drywood termites from portions of a house such as an attic, porch, or bedroom, or from an individual apartment or condominium unit inside a multi-family dwelling. Heat sensitive articles are removed and the infested area is cordoned off with polyethylene or vinyl sheets. Temperature probes are placed in the hardest-to-heat locations and heat is applied with a high-output propane heater. After a lethal target temperature is achieved, the area can be cooled quickly for immediate reoccupation. If a heat liable material cannot be removed, it must be thoroughly protected with insulating blankets.
Excessive cold is primarily used for treating wall voids or similar small enclosures in a structure. Liquid nitrogen is pumped into these voids until the temperature drops to a level lethal to drywood termites. Temperature probes should be used to insure that lethal temperatures are attained. During treatment the area must be monitored for safe oxygen levels.