The susceptibility of wood to filamentous fungi (mould) attack is determine mainly by laboratory methods with descriptive grading of fungal growth on the surface of the wood specimens. It is a lot of different grading scale of fungi growth, but determination of the size of fungi growth is many times not easy, not clear and often difficult. Although the filamentous fungi are not included to microorganisms which cause very strong damage of lignocellulosic materials, mainly disfiguring them but not effecting in short time on their strength properties. They may however cause even soft rot of lignocellulosic materials if they have good thermal and moisture conditions for their growth for an enough long time. Moulds even in short period may dropping the value of lignocellulosic materials. Moreover the growth of filamentous fungi on any kind of materials always creates environmental and health hazard. The quantification and objectification of size of the fungi growth is necessary for easier and more comparable assessment of the susceptibility of wood and wood based-materials to the fungi. In these studies, we tried to evaluate susceptibility of wood to the filamentous fungi not only by standard visual grading of mould fungi growth on wood surface, but also by instrumental measurement the surface of wood samples covered by fungi and by determination ergosterol content in wood resulting from the fungi growth. The samples as discs of 50 mm diameter of Scots pine sapwood, natural or treated with a model wood preservative, were exposed separately to the two mixtures of filamentous fungi: Aspergillus niger, Paecilomyces variotii, Trichoderma viride, Alternaria alternata and Penicillium funiculosum = Mixture S or Aspergillus niger, Paecilomyces variotii, Trichoderma viride and Ophiostoma piliferum = Mixture E. The test confirmed applicability of wooden discs of 50 mm diameter to such a tests.The use of both instrumental method of fungi growth measurement gave very clear defined results with good differentiation between efficacy of different retention of wood preservative and control wood but in both cases not fully compatible with the results of the visual evaluation of fungal growth by standard, conventional descriptive scale.

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