A technique is described for determining the efficacy of soluble, diffusible preservative plugs for eradicating decay in joinery. It uses blocks of Scots pine sapwood or heartwood adjusted to known moisture contents prior to the establishment of the test fungus Coniophora puteana, from a single longitudinal dowel and the subsequent introduction of the preservative plugs. Prevention of decay, eradication of the test fungus and movement of the preservative were monitored after exposure periods of up to 24 weeks. Movement of boron from borate-based plugs along the grain varied with moisture content and was largely independent of sapwood or heartwood or the type of preservative plug used; movement across the grain was more restricted. The zones protected from decay varied with moisture content and in sapwood were approximately 30 mm along the grain at 25% moisture content and over 100 mm at 50% moisture content; the protected zones in heartwood were somewhat greater than in sapwood. Generally the fungus was eradicated from the zones protected from decay but sometimes live fungus was still present; the long term significance of this needs further study.

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