Resistance of borate-treated lumber to subterranean termites under protected, above-ground conditions

IRG/WP 00-30239

K Tsunoda, A Adachi, T Yoshimura, A Byrne, P I Morris, J K Grace

An experiment to simulate the dodai (sill plate) of the Japanese houses was conducted at the termite field test site of Wood Research Institute in Kagoshima, Japan where two economically important subterranean termite species [Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe)] are established. DOT(disodium octaborate tetrahydrate)-treated hem-fir samples [Tsuga heterophylla (Raf.) Sarg. and Abies amabilis (Dougl.) Forbes] in a dimension of 105 x 105 x 400 mm3 were placed on concrete blocks 19 cm above ground surface. The test samples were prepared from sound wood samples pressure treated to supply 10 replicates of shell-treated materials at target levels of 2% BAE and 3% BAE. The subsequent diffusion storage produced another set of through-treated samples at the same target levels. Feeder stakes within the block hollows extended into the soil to facilitate the access of the termites to the wood samples. The assembled sets were covered with plastic boxes to protect the samples from the weather. Samples were visually inspected for termite attack and decay and rated according to AWPA standards. After 4 years' exposure, borate-treated samples (2% BAE shell, 3% BAE shell, 2% BAE through and 3% BAE through treatments) were free from termite attack, while one replicate each of 2% BAE with DDAC (didecyldimethylammonium chloride) and CCA 4.0 kg/m3 treatments, the latter included as a reference preservative, were slightly attacked. Untreated hem-fir and hinoki (Chamaecyparis obtusa Endl.) controls were slightly to heavily attacked during the same test period. No sign of decay was found on any sample, although moisture contents were well above fiber saturation points in some samples.


Conference: 00-05-14/19 Kona, Hawaii, USA

Download document (227 kb)
free for the members of IRG. Available if purchased.

Purchase this document