Heart Rot of Jack Pine in Ontario. IV. Heartwood-inhabiting Fungi, Their Entry and Interactions within Living Trees

Abstract

The five most common stem-inhabiting fungi of jack pine (Pinusbanksiana Lamb.) in Ontario were inoculated into the stems of living trees that were roughly 40 years old. Their natural occurrence in branch stubs and at various heights in the stems of these trees was also studied. From these results, and from those that were obtained from older trees in earlier studies, conclusions which concern the occurrence, importance, and apparent avenues of entry of these fungi are presented. Some of the trees were inoculated with one of the Ascomycetes, which was followed 1 year later by one of the Basidiomycetes. The interactions of the fungi in vivo did not always correspond with those observed in vitro; however, they do explain many of the observed relationships between the occurrence of these fungi in living jack pine and other factors. Fomespini (Brot. ex Fr.) Karst., the Basidiomycete that is responsible for most of the trunk rot of jack pine in Ontario, was not affected in living tree stems by the presence of the Ascomycetes that frequently colonize this tissue. On the other hand, Peniophorapseudo-pini Weres. and Gibson, the Basidiomycete that is responsible for about one quarter of the red trunk stain in this species, was almost completely inhibited in living trees by the presence of Ascocorynesarcoides (Jacq. ex Gray) Groves and Wilson, which would explain many of the unusual patterns of occurrence of P. pseudo-pini in living jack pine.