Root-rotting fungi in white spruce, black spruce, and balsam fir in northern Ontario

Abstract

Fungi associated with root rot in living trees were isolated and identified from 521 white spruce (Piceaglauca (Moench) Voss), 1342 black spruce (Piceamariana (Mill.) B.S.P.), and 1383 balsam fir (Abiesbalsamea (L.) Mill.) ranging in age from 26 to 208 years (at a 30-cm height), in 165 stands across northern Ontario. Trees were pulled out with the winch of a skidder, root decays and stains were measured, and cultures were made from root and butt sections. Armillaria spp., considered in this study to be mostly Armillariaostoyae (Romagn.) Herink, was the most frequently isolated fungus, occurring in 32, 34, and 46% of white spruce, black spruce, and balsam fir, respectively. Inonotustomentosus (Fr.:Fr.) S. Teng, Scytinostromagalactinum (Fr.) Donk, and Coniophoraputeana (Schumach.:Fr.) P. Karst. were next in frequency, in that order. An additional 26 Basidiomycetes were associated with lesser amounts of root rot in the three species. Armillariaostoyae infected, and remained mostly below ground in all three species, averaging less than 0.3 m in height up the stem in living trees, while most of the other major fungi advanced more than 0.5 m up the stem in average infected trees. The frequency of A. ostoyae in white spruce and black spruce increased with tree age to about 90 and 130 years, respectively, then leveled off, probably because of diseased trees falling from the stand. An age relationship was not found with this fungus in balsam fir. The other fungi generally increased in frequency of occurrence with tree age. The only major fungus that attacked living tissues (sapwood) exclusively to any extent was A. ostoyae. Some less frequent fungi such as Resiniciumbicolor (Albertini & Schwein.:Fr.) Parmasto and Serpulahimantioides (Fr.:Fr.) P. Karst. indicated pathogenicity by attacking sapwood initially. Armillariaostoyae infected significantly higher numbers of black spruce and balsam fir growing on dryer sites (soil moisture regimes (SMR) 1–3) than on wet sites (SMR 5–7). The only other fungus apparently related to moisture regime was unknown F, which infected black spruce more on wet than on dry sites. Significantly higher proportions of root and buttwood of all three species were infected with A. ostoyae and I. tomentosus in northwestern Ontario than in northeastern Ontario. Heavy to severe root rot caused tree height or diameter growth reductions when trees were infected by either A. ostoyae or I. tomentosus. An Ascomycete, Ascocorynesarcoides (Jacq.) Groves & D.E. Wilson, was associated with pink or faint brown stains, often near bark seams, in white spruce and black spruce. It was isolated from roots of 20 and 28% of these species, respectively.