Investigating the Efficacy of Established Chemical Wood Modifications on Large-Diameter Pine: Durability Against Basidiomycetes

In Germany, <i>Pinus sylvestris</i> is a dominant tree species, and many trees with large diameters are not utilised due to difficulties with processing. However, older pines have larger volumes of sapwood, and boards with a high sapwood content can be produced. The durability of boards from large-diameter (>50 cm) <i>P. sylvestris</i> trees, treated with furfurylation, acetylation, DMDHEU (1.3-dimethylol-4.5-dihydroxyethyleneurea), and SorCA (Sorbitol/Citric Acid), was assessed. The samples were taken from different sections along the longitudinal axis and the cross-section. The durability was tested against <i>Coniophora puteana</i>, <i>Rhodonia placenta</i>, and <i>Trametes versicolor</i>, according to the EN 113-2 standard. All treatments had a median mass loss < 5%, so classed as "highly durable" (Durability Class 1) against all fungi. DMDHEU had a large deviation in mass loss against <i>Coniophora puteana</i> and could potentially be classified as "moderately durable" (Durability Class 3), if based on the mean mass loss. The inner part of the end section had a higher mass loss, indicating that there was poorer retention of the treatment at this location. Overall, chemical modifications on large-diameter pine trees were effective at increasing durability. Utilising large-diameter pine trees can help to make use of regional resources and potentially reduce reliance on imported timber. With favourable mechanical properties and easy-to-treat sapwood, large-diameter <i>P. sylvestris</i> trees could be used for commercial treatments.