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.

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