Degradation of Wood Preservatives by Fungi

Abstract

Wood-inhabiting fungi, not necessarily responsible for major decay, are shown to be capable of degrading a toxic compound into a less potent form, thus rendering it less effective in protecting wood from decay by less-tolerant basidiomycetous wood-destroyers. Sweetgum or pine sapwood blocks treated with preservatives (ammoniacal copper arsenate, fluor-chrome-arsenate-dinitrophenol, a creosote or pentachlorophenol) were exposed progressively to two different wood-inhabiting fungi with sterilization between the first and second exposure. The fungus in the first exposure was usually an Ascomycete or a Fungi Imperfecti— Chaetomium globosum, Phoma, Orbicula, Graphium, Pestalozzia , or Trichoderma species, isolated from wood below the ground. In one experiment, the fungus in the first exposure was a basidiomycete, Lenzites trabea or Polyporus versicolor . The second fungus, a prominent Basidiomycete— Coniophora puteana, Lentinus lepideus , or Lenzites trabea —was the bioassay fungus, since its purpose was to show whether the first fungus had degraded the preservative. Generally, the treated block, except where exposed to another fungus, remained virtually untouched by the bioassay fungus. Clearly, therefore, the first fungus had rendered the preservative ineffective but without appreciably decaying the wood itself Chemical analyses of treated blocks indicated that in the first exposure the fungi had substantially depleted sodium arsenate and pentachlorophenol.