Study on the ability of wood-destroying fungi to grow through chemically modified wood

IRG/WP 19-40858

L Emmerich, S Strohbusch, C Brischke, S Bollmus, H Militz

Over the last decades, chemical wood modification technologies were developed to increase the resistance against attack by wood-destroying organisms without using biocides. Most of those technologies are based on an impregnation step initially. In most treated wood products, mainly by using solid wood in thicker dimensions as in posts, poles, sleepers, deckings etc. it is known that wood impregnation fluids are not distributed throughout the whole wood cross diameter, but just form a protected zone (‘shell-treatment’) of some millimetres or centimetres. The depth of the protected zone depends on wood species and treatment process. While ‘shell-treatments’ might be adequate to achieve a sufficient protection against fungal decay by treatment with biocides, the effect on how wood treated by chemical wood modification systems performs with regard to the resistance against wood-destroying organisms, is not yet known. On that basis, this study aimed at examining systematically the ability of wood-destroying fungi to grow through modified wood and degrade an untreated underlaying wood zone. Hence, decay tests were performed with pure cultures of T. versicolor (wr), C. puteana (br) and terrestrial microcosm (TMC) containing soft rot fungi and other soil-inhabiting micro-organisms. The incubation period of segmented specimens of 20 (ax.) x 20 x 45 mm³ (modified mantle, untreated core/dowel) was 16 weeks and tests conducted according to CEN/TS 15083-1 (2005) and CEN/TS 15083-2 (2005). By light microscopy photographs it was shown that both white rot and brown rot and also soft rot fungi can grow through chemically modified wood. The latter was shown independent of the modification agent which was acetic anhydride (acetylation) or 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU), the treatment level and wood species of the modified mantle specimens. Significant mass losses (ML) of untreated wood (dowels), surrounded by a modified wood mantle, indicated that chemical wood modification does neither inhibit fungal growth nor affect the ability to degrade untreated wood substrate.

Keywords: acetylation, chemical wood modification, decay, DMDHEU, durability, fungal growth

Conference: 19-05-12/16 Quebec City, Canada

Download document (1.7 Mb)
free for the members of IRG. Available if purchased.

Purchase this document