Do bark beetles facilitate the establishment of rot fungi in Norway spruce?

Bark beetles, mycelia and wood were sampled from the vicinity of insect galleries in the bark of Picea abies high stumps of four different age classes in southeastern Sweden. Molecular methods were used for fungal species identification. From 203 samples a total of 21 fungal taxa were found, including 12 ascomycetes and 9 basidiomycetes. Of the filamentous fungal species, 50 % were found both in bark and bark beetles, and 37 % were found in bark, wood and bark beetles. Yeasts dominated in stumps that were 1-yr old and in control samples without insect activity. In 2- and 3-yr-old stumps, filamentous ascomycetes were present but also common wood decay basidiomycetes such as Stereum sanguinolentum, Phlebiopsis gigantea, Trichaptum abietinum and Fomitopsis pinicola were found as mycelia associated with insect galleries and on bark beetles. The results indicate that insect facilitation of the establishment of wood decay fungi cannot be neglected.