BLUE-STAIN FUNGI ASSOCIATED WITH TOMICUS-PINIPERDA IN SWEDEN AND PRELIMINARY-OBSERVATIONS ON THEIR PATHOGENICITY

Mass attacks by Tomicus piniperda were induced in young Scots pines of varying vitality by baiting the trees with split, fresh pine bolts. Trees were felled at different times to determine the development of blue-staining of sapwood. Fungi were isolated from samples of inner bark and blue-stained sapwood in connection with galleries of T piniperda. Samples were also taken from beetle-attacked pine timber. In addition, 4 stem-pruned trees were inoculated with the 2 most important species isolated from trees attacked by T piniperda. Three species of fungi were rather frequently isolated, Hormonema dematioides, Leptographium wingfieldii and Ophiostoma minus. The latter 2 species were most active in invading the sapwood. Blue-staining of sapwood occurred rather late in the season, 1-2 months after attack. One tree in each pair of trees inoculated with L wingfieldii and O minus were dying when harvested more than 4 months after mass inoculation. Thus, these fungi may play a role in overcoming the resistance of trees under beetle attack.