Copper continues to be an important fungicide in wood preservation. It is the primary component of the preservatives that have replaced chromated copper arsenate for treated wood in residential construction in North America. However, a co-biocide is normally needed to protect against copper tolerant organisms. Previous work has shown that the spores of at least one copper tolerant fungus, Oligoporus placentus, were not very tolerant of copper. This explained the unexpectedly good performance of copper-only preservatives when just exposed to spores and not exposed to mycelium of such fungi. This work was designed to determine if the same was true of another copper-tolerant fungus that produces basidiospores in agar culture. An agar medium bio-assay was used to assess inhibition of basidiospore germination and mycelial growth of Fomitopsis palustris (Berk. et Curt) with O. placentus (Fr.) Gilb. & Ryvarden, as a known reference. The spores of F. palustris and O. placentus had the same copper sensitivity. The basidiospores were sensitive to copper concentrations between 20 and 50 times lower than their corresponding mycelium. These data confirm that spores of copper tolerant fungi are not very tolerant of copper.

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