Fungi colonizing Douglas-fir in cooling towers: Identification and their decay capabilities

This study was performed to identify microfungi isolated from chromated copper arsenate (CCA) treated-Douglas-fir members in cooling towers, and to test for their capacities to cause weight loss, anatomical damage, and strength losses in Douglas-fir and Keruing heartwood. Among 26 fungal species isolated, Acremonium sp., Fusarium spp., Trichoderma spp., Phialophora spp., and Alternaria alternata were most frequently isolated, constituting approximately 75% of all isolates. Half of the fungi, representing about 60% of all isolates, caused soft-rot damage. Microscopic examination revealed that most of the fungi eroded the cell wall (Type 2 damage), and soft-rot types did not differ with wood species. Strength reductions by fungal attack were not significant compared to controls although one fungal species (Monocillium sp. KUC 3016) produced significant strength loss on Douglas-fir, and three species (Gonabotrys simplex, Phialophora mutabilis KUC 3022, and Phialophora mutabilis KUC 3039) caused significant strength loss on Keruing. The results indicate that some soft-rot fungi can affect wood properties significantly, and their potential to affect the service life of wood members in cooling towers must be considered.