The Naval Research Laboratory is evaluating the non-rubber-producing portion of guayule (Parthenium argentatum) resin as a protectant for wood in terrestrial and marine service. This study phase, in collaboration with the universities of Arizona and Mississippi State, evaluates the resin's fungicidal worth. Resin-impregnated pine sapwood was exposed to brown rot fungi (Gloeophyllum trabeum, Antrodia carbonica, Formitopsis cajanderi, Lentinus ponderosa), white rot fungi (Dichomitus squalens, Trametes versicolor, Ganoderma sp.), and a natural inoculum of soft rot fungi from unsterile soil. The exposures for the brown and white rot fungi lasted 20 weeks, using malt agar chambers inoculated 2 weeks prior to the introduction of the treated wood; the soft rot exposure lasted 12 weeks and included treated birch specimens. Weight loss data showed a definite inhibition of decay of the treated wood by the brown and white rot fungi, however there was some decay caused by Lentinus ponderosa (closely related to creosote-tolerant Lentinus lepideus) and by Antrodia carbonica, a common utility pole fungus. None of the resin-impregnated pine or birch specimens were attacked by the soft rot fungi, even those specimens containing the lowest of the three resin concentrations in the wood. In both sets of exposures all of the controls were decayed.

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