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.

The NEBIE plot network: Highlights of long-term scientific studies

“…were by far the most common pathogens associated with most of the tree disease and mortality observed on all sites, and often were isolated with other known root disease and decay fungi from the same diseased root. Data from the Sioux Lookout site supported observations by Whitney (1995) that A. ostoyae is the primary Armillaria species causing root disease in pure conifer stands. Interestingly, A. sinapina, which was almost absent in the pure conifer stand, played a significant role as a root disease pathogen of both conifers and hardwoods on the boreal mixedwood (Timmins and Kapuskasing) and boreal hardwood (Thunder Bay) sites (Fig.…”

Comparison of Armillaria root disease on burned and unburned, harvested sites in Ontario

“…An average of 46% of 1383 living balsam fir, mostly under 150 years of age, and without obvious crown symptoms of disease, had ARD. Thirty nine percent of living, healthyappearing balsam fir 21-30 years of age were attacked by this disease (Whitney 1995), confirming further that young natural seeded balsam fir are attacked.…”

“…In the same study 86, 77 and 73% of unhealthy jack pine, black spruce and white spruce, respectively, were infected with the fungus. Detailed studies of the roots of older conifers, 26-208 years of age in Northern Ontario, showed balsam fir to be even more heavily attacked by ARD than either white spruce or black spruce (Whitney 1995). An average of 46% of 1383 living balsam fir, mostly under 150 years of age, and without obvious crown symptoms of disease, had ARD.…”

Snag characteristics and cavity-nesting birds in the unmanaged post-fire northeastern Canadian boreal forest

“…In turn, this could affect snag production since balsam fir is more vulnerable than black spruce to wood decay and spruce budworm (Choristoneura fumiferana (Clem. )), an important defoliation insect causing much mortality in boreal forests of eastern Canada (Whitney 1995, Hennigar et al 2008). …”