Effects of Environmental Factors on Decay Rates of Selected White- and Brown-Rot Fungi


  • June Mitsuhashi Gonzalez
  • Jeffrey J. Morrell


Decay, <i>Postia placenta</i>, <i>Gloeophyllum trabeum</i>, <i>Trametes versicolor</i>, Douglas-fir, western hemlock, southern pine, modulus of elasticity, modulus of rupture


Assessing the impact of fungal decay in wood structures poses a major challenge for building inspectors. Although models have been developed to predict degradation rate of building components in varying climatic conditions, most are hampered by the lack of fundamental data on effects of fungal attack on engineering properties. Developing data on degradation rates in differing conditions would help enhance these models. The ability of two brown-rot and one white-rot fungus to degrade wood of three species was assessed in varying temperature and moisture conditions. Modulus of elasticity (MOE) was the most sensitive measure of fungal attack, whereas modulus of rupture (MOR) was affected more slowly. Wood species had no effect on MOR losses, but wood durability did influence fungal effects on MOR. The white-rot fungus caused comparable MOE losses to the brown-rot fungi but had a much decreased effect on MOR. Moisture content, within the range tested, had little influence on decay rates. Fungal effects tended to be slower at the lowest temperature tested (15°C) but differed little between 25 and 35°C. Results suggested that removal of wood that has been wet for some time is advisable if dynamic properties are critical. Results also supported incorporating temperature and time of wetting factors into building models.


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