Abstract
Copper-based preservatives remain crucial for protecting timber from fungal decay for wood in direct soil contact, yet the presence of copper tolerant brown-rot fungi poses a risk to long-term service life, especially where treatment penetration is shallow. Fomitopsis ostreiformis is an aggressive brown rot species found across Australian field trials but lacks established copper tolerance thresholds. This study used in vitro petri dish growth assays and soil jar decay tests to assess the copper tolerance of F. ostreiformis. Fungal growth on amended malt extract agar was not inhibited at 1000 ppm of copper. Soil block tests of copper sulphate treated Pinus radiata suggested a copper threshold of approximately 1760 ppm to inhibit this fungus. In the soil jar decay tests, leached samples had lower mass losses than non-leached samples, suggesting that the leaching process potentially improved copper redistribution. These findings highlight the copper tolerance of F. ostreiformis, with implications for the effectiveness of shallow treatments against this fungus. Further tests using copper with a co-biocide are recommended.