We report the fifth and sixth years of field study results from a protected above-ground field test in Hawaii simulating the sill plate (dodai) used in conventional Japanese housing construction. Field tests were established in both Hawaii and Japan to examine the efficacy of disodium octaborate tetrahydrate (DOT, 2% and 3% BAE shell and through) wood treatments. In Hawaii, chromated copper arsenate (CCA, 4 kg/m3) and ammoniacal copper zinc arsenate (ACZA, 4 kg/m3) were included in the test, along with untreated western hemlock and Pacific silver fir controls. Both field sites support active Formosan subterranean termites, Coptotermes formosanus Shiraki, although termite pressure is greater in Hawaii due to the uniformly favorable environmental conditions. To date, all wood treatments have performed well, with mean visual damage ratings ranging from 10 (ACZA) to 8.5 (DOT, 2% BAE shell treatment) on the AWPA 10 - 0 scale after six years. This report updates the four-year results previously reported in IRG/WP 01-30265 (Grace et al. 2001).

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