Mold growth on pine and spruce wood: Dependence on moisture content, anatomical direction, and mold species

Better knowledge about the conditions for mold growth on wood could improve mold growth prediction models, prevent health risks, and increase the durability of wood without any additional biocidal treatment. Mold growth depends on the surrounding condition and the available nutrients. The most effective measure to prevent mold growth in wood-based houses is to keep the indoor relative humidity sufficiently low. We studied the dependence of mold growth on ambient relative humidity (75 - 95 % RH) at 23 °C with respect to the anatomical direction of wood and mold species. The samples were prepared from pine and spruce sapwood. The monitored parameters were the time of germination and the first macroscopic observation. Mold growth started at relative humidity higher than 75 %. Liquid water retarded mold germination. The germination time varied between 7 and 24 days in the absence of liquid water in the samples. The time from the first macroscopic observation ranged from 19 to 31 days under conditions without liquid water. Wetting the samples increased the time required to observe the first fungal growth at the microscopic and macroscopic levels. The use of variable humidity in the range of 75 – 95 % RH extended the time required for germination.