Fungi colonizing preservative-treated Douglas-fir poles after remedial treatment with fumigants

The microfungi present in transmission poles of preservative-treated Douglas-fir remedially treated with one of four fumigants were determined by removing increment cores 5 and 15 years later and culturing them on nutrient media. The microfungi isolated from the wood were then characterized according to their ability to cause a loss in wood weight, to tolerate conventional wood preservatives, and to tolerate wood fumigants. The wood treated with fumigants 5 years earlier was sparsely colonized, while that treated 15 years earlier was colonized more heavily. In general, many of the same species of microfungi occurred in treated and untreated poles. In both, fungal populations were dominated by Scytalidium and Trichoderma spp. None of the isolates caused losses in wood weight greater than 5%, but several exhibited tolerance to short fumigant exposures. The latter trait may help explain the presence of these fungi in wood still containing measurable levels of fumigant. The presence in fumigant-treated wood of fungi previously shown to be antagonistic toward wood decay fungi may help explain the ability of the four test fumigants to provide long-term protection.Key words: fungi, Scytalidium, Trichoderma, colonization, Douglas-fir.