Decay fungi can be categorized according to the type of rot produced: soft, white or brown.
Soft rots are caused by Ascomycetes and are facilitated by enzymes that adhere to the hyphal cell
wall, therefore decay does not occur in advance of the fungus.
White rots are caused by Basidiomycetes. These fungi are able to breakdown cellulose and lignin.
The cellulases produced are primarily exocellulases, and operate in advance of the fungus.
Brown rots are caused by Basidiomycetes. These fungi can only break down cellulose, but the
cellulase enzymes produced are both exo- and endocellulases. Decay and strength loss occurs
quickly and operates in advance of the fungus.
Decay fungi can also be categorized according to the means of entering the host, and where the
fungus operates. Three general categories are recognized: true heartrots, wound-entry heartrots,
and sapwood rots.
True Heartrots: These fungi exist in the heartwood, do not require a wound to enter the tree, and
consistently produce fruiting bodies on living trees.
- Echinodontium tinctorium Indian Paint Fungus
- Host: true firs, hemlocks, occasionally on D-fir, cedar, and spruce.
Damage: cause a stringy yellow rot. Infection thought to occur through small branchlets,
then is radially overgrown until it can access the heartwood. This can take 40 years or
Conks: have teeth, not pores on the fertile layer, have a bright orange context, and are
dark black/brown with a rough outer surface. Typically grow from branch stubs.
- Phellinus pini Red Ring Rot
- Host: widely distributed, wide host range, most frequent on hemlock, spruces, larch,
Douglas-fir and cedar.
Damage: causes a white pocket rot, is a major cull agent because of its wide distribution.
Unknown mode of entry.
Conk: has a yellowish fertile layer, large pores, rough, ridged
- Phellinus ignarius, Phellinus tremulae False Tinder Fungus
- Host: ignarius is found on birch, tremulae on aspen
Damage: may cause more loss than any other decay fungus on hardwoods.
Conk: is black with a rough surface and brown fertile layer.
Wound Entry Heartrots: These fungi invade the heartwood through a wound, such as scars,
frost cracks, broken tops, cankers, etc.
- Fomes officinalis Quinine Conk
- Host: wide range of conifers, especially Larch, spruce and Douglas-fir
Damage: brown cubical heartrot, continuing decay of dead trees.
This fungus has been
known since antiquity as the source of agaricin, a medicine used
to treat diseases such as tuberculosis. Also produces quinine,
used to treat malaria.
- Fomes fomentarius White Spongy trunk Rot
- Host: primarily Birch however also reported on alder, balsam poplar and cottonwood in British
Damage: causes a white rot in both sapwood and heartwood. Decay is caused in
both living and dead trees.
Conks: are perennial, woody or leathery and usually hoof shaped. The upper surface is grey to
brown or black and forms a smooth crust. The lower pale brown surface is porous and concave. These
conks are found on standing living or dead trees and on slash.
- Fomitopsis pinicola Red
Ring Conk, brown
- Host: many conifers, usually a saprot but can become a heartrot.
Damage: causes brown crumbly rot, very common on dead trees, a scavenger kind of fungus. Prolific fruiting.
- Ganoderma applanatum White Mottled Rot
- Host: commonly deciduous trees but also found on coniferous species. In B. C.: maple, alder,
birch, beech, poplar, willow, amabilis and grand fir, white and Sitka spruce, Scots pine, Douglas-fir,
mountain and western hemlock, and western redcedar.
Damage: important decay of dead trees but may enter wounds of live trees causing extensive
Sapwood Rots: These fungi attack dead wood primarily, such as sapwood that has been killed by cankers, or dead trees.
- Cryptoporus volvatus gray sap rot, pocket fungus
- Host: primarily Douglas-fir killed by fire or beetles
Damage: very common on dead Douglas-fir. Conks are annual, leathery and pouch-like. Decay is a brown rot.
- Gloeophyllum sepiarium
- Host: most conifers, several deciduous species, associated with fire-killed trees and slash
Damage: brown cubical sap rot, conk has gill-like structures, is annual, leathery and upper surface is zoned and rough.
- Hirschioporus abietinus
- Host: many conifers, primarily a saprot, sometimes causes a heart rot in living trees
Damage: causes a white pitted saprot, conks are small, leathery, produced on dead trees, upper surface zoned, light gray.