The critical moisture and temperature conditions for the growth of some mould fungi and the brown rot fungus Coniophora puteana on wood

The growth of some mould fungi on pine and spruce sapwood was studied in 40 different constant moisture and temperature conditions. The temperature range was between +10 and +40°C and the relative humidities varied from 76 to 100% relative humidity (RH). The incubation time was 12 weeks. The mixed mould inoculation used included typical fungi growing on wood: Aspergillus versicolor, Cladosporium sphaerospermum, Penicillium sp., Aureobasidium pullullans and other fungi, which were collected from the air in the Forest Products Laboratory. The growth of Coniophora puteana was studied at +20°C and the relative humidity range was between 76 and 100% and the incubation time 60 weeks. The studied moulds grew rapidly in higher humidities (RH > 96%). The lowest humidity for growth was 80%, where the growth was very slow and it could be detected only by microscopy. At higher temperatures the growth was faster and the needed relative humidity was lower than it was in lower temperatures. The brown rot fungus Coniophora puteana grew only at 96-100% RH conditions, where the moisture content of wood was over 25 weight%. The growth was very slow at 96% RH, and after one year incubation the weight losses were quite low. The mycelium strands could mainly be clearly detected, but in some cases no mycelium could be detected on the surface of wood, even if weight losses were measured.