Drywood Termites

Drywood termites cause damage throughout Southern California. Unlike subterranean termites, drywood termites require no contact with soil; as their common name implies, the attack dry wood. Attics and other relatively inaccessible locations in the upper parts of structures are common areas of drywood termite infestation. These termites also carry out their work completely inside the wood often the only evidence of their presence is a few small holes through which they push frass (fecal material and undecomposed wood formed into tiny, football-shaped pellets) out of the galleries. Piles of these pellets accumulate beneath such "kick-out" holes. Because they can reinfest dry wood, it is impossible to predict with certainty that other and as yet undetected colonies are not present. For this reason, "bagging" (enclosing the entire structure in a vapor-proof mem- brane) and fumigation of the entire structure with toxic gas is the advisable control. Treatment of individua- al colonies with a toxic dust or liquid is sometimes rec- commended, but there is considerable risk with this approach because the extent of the infestation is unknown. If individual colonies are treated, regular surveillance of the entire structure should be maintained, and if additional colonies are found fumigation probably will be necessary. Unfortunately, there is no residual effect of the fumigation treatment and, immediately following removal of the bag, the structure is again susceptible to new infestations. For new construction in areas of high incidence of drywood termites, one would be well advised to use structural members which have been pressure-treated with an insecticidal preservative, and to treat voids and inaccessible attic areas with sportive dust.

Subterranean Termites

Subterranean termites occur throughout California. They build their nests in the soil, and normally require continuous contact with soil to derive moisture for survival. Occasionally, they build their nest in above-ground parts of a structure without maintaining soil contact, but there must be a continuous supply of water. such as a leaky pipe, for this to occur. When wood is in contact with soil, termites can borrow from the soil directly into the wood. Foundation cracks, voids, hollow cement blocks and unbonded stucco may also provide hidden access to the structure for subterranean termites. If a barrier such as a concrete foundation exists between soil and wood, subterranean termites build earthen tubes over the barrier to bridge it. Once in contact with wood, the termites start boring and feeding inside them. The earthen tubes, however, are easily detected in such exposed areas: if they are broken and not rebuilt, the termites in the structure above will no longer be able to reach the nest in the soil and will die. Subterranean termite excavations galleries in the structure (usually discovered by the failure or move- mint of a wood member) normally will have soil particles associated with them.

The usual control for a subterranean termite infestation is to break all tubes between soil and wood, remove all direct contact between the wood structure and the soil (where subterranean termites can enter without detection) and treat the soil surface beneath the structure, but especially at the base of all foundation and pier perimeters, with an insecticide barrier which will pre- vent termites in the nest from returning through the solid to rebuild their tubes. If allowed to continue, a subterranean termite infestation can completely destroy the structural integrity of an entire building in several years. This occurs most often in homes which are not inspected for many years.