Long-term performance of fused borate rods for limiting internal decay in Douglas-fir utility poles.

The ability of boron to diffuse from fused boron rods into surrounding wood was investigated on pentachlorophenol-treated Douglas-fir poles. Boron readily diffused into the wood surrounding the treatment holes and was present at protective levels in most poles within 1 year after application. The protected zone was generally confined to the treatment zone. Effective levels of boron were still present in this zone 15 years after treatment. Attempts to correlate the presence of decay fungi with residual boron levels indicated that these fungi were sometimes present in zones with boron at the lower threshold level of 0.5 kg m-3 boric acid equivalent (BAE), but most of the isolations could be explained by localized variations in distribution. Boron rods provided excellent long term protection against internal decay in Douglas-fir poles. [ABSTRACT FROM AUTHOR]