This study evaluated the relative ability of three types of wood preservatives to inhibit attack by Formosan subterranean termites (FST) (Coptotermes formosanus Shiraki) and native subterranean termites (Reticulitermes spp.). The study also evaluated the roles of preservative retention and penetration in preventing termite damage. Sections of boards from six wood species within the Spruce-Pine-Fir species group were pressure-treated with one of four concentrations of a borax-copper (BC) preservative composed of 93% borax (sodium tetraborate decahydrate) and 7% technical copper hydroxide or one concentration of disodium octaborate tetrahydrate (DOT) or chromated copper arsenate (CCA). Specimens were cut after treatment, exposing untreated end-grain in specimens not completely penetrated by preservative. The specimens were exposed above-ground, protected from the weather, at a site with populations of both native and FST near Lake Charles, Louisiana. Specimens were rated for extent of termite attack after 6, 12, and 24 months of exposure. Attack by FST was more severe than that by native termites for all preservative treatments, although this difference was less obvious at higher preservative retentions. For all treatments, termites preferred to attack the center of the end-grain of the specimens where preservative was either absent or at a lower concentration. However, CCA, which had the lowest overall penetration, was more effective than either borate preservative in preventing attack, whereas some DOT- and BC-treated specimens suffered attack even with what appeared to be complete boron penetration. These results indicate that the efficacy of shell treatments in preventing termite attack is a function of the type of preservative. The BC wood preservative protected wood from both native and Formosan termite attack at B2O3 concentrations equivalent to or lower than that of DOT treatments
