Resistance of borax–copper treated wood in aboveground exposure to attack by Formosan subterranean termites

Abstract

The spread of Formosan subterranean termites (FSTs) in the southern United States has increased public interest in finding a preservative treatment to protect framing lumber from termite attack. This study evaluated the use of a borax-based preservative to protect wood from FST attack. Southern Pine and Douglas-fir specimens were pressure-treated with three concentrations of a borax–copper (BC) preservative composed of 93% borax (sodium tetraborate decahydrate) and 7% technical copper hydroxide. Untreated specimens and specimens pressure-treated with disodium octaborate tetrahydrate (DOT) were included for comparison. The specimens were exposed above ground, protected from the weather, at an active FST exposure site in Hilo, Hawaii. Specimens were rated for extent of termite attack after 6, 12, and 24 months of exposure. The BC treatments provided good protection of Southern Pine, but protection of Douglas-fir was variable at all BC retentions evaluated. The variability in protection for Douglas-fir was attributed to lower retentions and uneven distribution of preservative within the specimens. Average damage ratings of BC-treated Southern Pine were slightly better (less damage) than those of DOT-treated Southern Pine at equivalent B2O3 retentions, suggesting that either the presence of low levels of copper or the form of the borate in the BC treatment influenced efficacy. The results of this study indicate that borax-based treatments can provide adequate protection against FST in wood species or wood products that allow uniform distribution of preservative.

Citation

Lebow, Stan; Woodward, Bessie; Crawford, Douglas; Abbott, William. 2005. Resistance of borax–copper treated wood in aboveground exposure to attack by Formosan subterranean termites. Res. Note FPL-RN-0295. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 4 p.