Fungi that cause sapstain in Canadian softwoods

The Canadian forest products industry suffers considerable losses due to discoloration caused by sapstain fungi. Although studied for a number of years, the identity, biology, and ecology of these fungi are still only partly understood. To determine which fungi caused stain problems, a detailed survey was conducted at seven selected sawmills across Canada. In summer 1997, fresh logs and lumber were set aside in the mills 1 month prior to sampling for fungi. We excluded bark-beetle-attacked wood and our logs remained free from their attack during storage. Five commercially important softwood species, Abies balsamea (L.) Mill., Picea mariana (Mill.) B.S.P., Picea glauca (Moench) Voss, Pinus contorta Dougl., andPinus banksiana Lamb., were included in the studies. A total of 1863 isolates were isolated from stained and adjacent areas on test wood, and were identified based on their morphological and physiological characteristics and mating compatibility to 13 different species representing five genera. The most commonly encountered genus, Ophiostoma (97%), was represented by nine species. A more diverse range of fungi was found in logs than in lumber; some species were more frequently isolated from one type of substrate and rarely (or not at all) from the other. No fungal species occurred exclusively in a particular region or wood substrate.