In this study, efficacy of various combinations of copper sulfate with either boric acid or calcium precipitating agent, NHA-Na (N'-N-(1, 8-naphthalyl) hydroxylamine) was evaluated. Wood specimens were treated with either 1%, 0.5%, or 0.1% concentrations of copper sulfate, boric acid, NHA-Na, copper sulfate + boric acid, or copper sulfate + NHA-Na mixtures. Treated specimens were subjected to laboratory decay resistance tests by using Petri dishes inoculated with Basidiomycetes fungi, Tyromyces palustris and Trametes versicolor for 12 weeks. Increased efficacy of copper sulfate against the brown rot fungus, T. palustris was observed when either boric acid or NHA-Na was added. NHA-Na only treatments at 1% and 0.5% concentration levels were the most effective treatments against the fungi tested. Boric acid treatments were not able to protect wood against decay after leaching because of possible leaching of boron. More detailed studies are in progress by using different fungal species and termites to obtain detailed information on efficacy of copper combinations with various compounds.

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