Pressure-treated utility poles have given many years of excellent service, but their lifetime is often shortened by internal decay of the untreated heartwood center, particularly in refractory species, such as Douglas-fir. This paper reports the distribution of boron from fused borate rods installed in CCA-treated Douglas-fir transmission poles. The boric acid equivalent was roughly monitored by the curcumin/salicylic acid color test on increment cores removed from poles at 6 and 18 months after installation of fused borate rods. The percent of increment core length showing boron at 18 months was 2.5 times greater than at 6 months. Boron was almost always detected downward from the treatment at a distance of 25 cm (10 inches). Movement of boron upward from treatment holes was not as good, rarely exceeding 5 cm (2 inches). The increment core length showing boron did not always correlate with moisture content but when the moisture content was greater than 40%, the total core length with boron was greater than 80%.

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