Boron treatment methods for lyctid susceptible hardwoods growing in Tasmania
L J Cookson, D Scown, K McCarthy
A survey of existing boron plants that treat to protect hardwoods from attack by lyctids in Australia showed that hot and cold bath, and vacuum pressure impregnation (vpi), were the two most common methods employed. In experimental work, two of the treatment methods, vpi and dip diffusion, were used to treat seasoned and green messmate (Eucalyptus obliqua) and blackwood (Acacia melanoxylon). The treating solution in both cases was Diffusol. For vpi treatment, a solution of 2.5% boric acid equivalent (BAE) was used to treat rough sawn boards with a Bethell schedule. After treatment, boards were strip stacked on a pallet under cover, later cut in half, and the centres sprayed with turmeric reagent to reveal that all sapwood was adequately treated with boron. The solution for dip diffusion contained 12% BAE. Block stacked timber was dipped, wrapped, and stored to allow diffusion of the boron. All green E. obliqua and A. melanoxylon boards were adequately treated after dipping in Diffusol and two, four or six weeks diffusion. Some of the air dried A. melanoxylon boards could not be adequately treated by this method when diffusion periods were just two or four weeks. However, a six week diffusion period allowed full sapwood treatment of all boards.