Biological incising of lodgepole pine and white spruce lumber with Dichomitus squalens

Abstract

Deep penetration into wood is necessary for wood preservatives to provide long-term durability and for some wood modification agents to enhance wood properties. Bioincising was investigated as a means to enhance chemical penetration. Candidate fungi were screened for bioincising on pine and spruce samples. Dichomitus squalens dramatically improved wood permeability. Full preservative penetration was reached in spruce samples exposed to D. squalens isolate 78A for 6 weeks. No loss in compression stiffness was detected in small-scale bioincised samples. Optimum growth conditions, inoculation methods, and the practicality of bioincising were investigated on full size lumber. The optimal temperature for bioincising with D. squalens was around 30 °C. Bioincising was most effective using grain or liquid inoculum. Using liquid inoculum, spruce samples exposed for 6 weeks reached an average penetration of 10 mm through the heartwood face and 22 mm through the edge; and using grain inoculum average penetration was 10 mm through the heartwood face and 25 mm through the edge. On full-size lumber, bioincising was highly variable. Less than 50% of the bioincised samples achieved a minimum preservative uptake of 200 kg/m3. However, samples that met a minimum uptake of 200 kg/m3 of preservative and achieved 5 mm penetration on both edge and heartwood faces were within an acceptable range for strength loss, comparable to mechanical incising. The biggest barrier to commercialization of bioincising is the difficulty in achieving consistent fungal colonization of commercial size wood using a simple application method and the high variability in success.