The ability of boron to diffuse from polyborate and boron/fluoride rods through the heartwood of three eucalypt pole species (blackbutt, red ironbark and spotted gum) was examined. The aim was simply to determine the effects of rod type, wood species and time on the longitudinal diffusion of boron in eucalypt heartwood. Rapid diffusion of boron from polyborate or boron/fluoride preservative rods occurred when rods were placed in the wet heartwood of the three eucalypt species. The diffusion generally increased with time and the level of diffusion was greater in the lower density species (blackbutt and spotted gum) than in red ironbark. The effect of rod type on diffusion was generally statistically insignificant. Hence, after 52 weeks there was no statistically significant difference in the diffusion of boron from the two rod types in any of the 3 pole species tested. The diffusion of boron was greater in pole stubs that contained pockets of decayed wood and this may account for why field data suggests that solid preservative rods are highly effective in controlling internal decay in eucalypt power poles.

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