Hardwood Stem Decays

Ganoderma applanatum (Pers.) Pat.

Current Status: In 2022, Ganoderma applanatum was detected ten times during ground detection surveys and 24 research grade observations were contributed through iNaturalist. The conk was especially abundant on western hemlock along the Carlanna Lake Trail in Ketchikan. Ganoderma applanatum is likely a species complex, found on both hardwoods and conifers in coastal Alaska

Hosts: Mainly hardwoods; but sometimes western and mountain hemlock, and white and Sitka spruce. Identification: Perennial, woody, fan- or shelf-shaped conk. Usually occurs as a saprobe on decaying logs and stumps. Occasionally found as a heart rot on wounds of living trees. Top: dull, dusty brown to grey-brown with concentric ridges. Bottom: white pore surface that immediately browns when touched. Interior: dark brown to cinnamon. Damage: Spongy mottled white rot of sapwood and heartwood. Remarks: Known as the artist’s conk because the fresh pore surface bruises dark brown when touched or scratched. Intricate etchings can be preserved for years if properly dried.

Fomitopsis betulina (Bull.) B.K. Cui, M.L.. Han & Y.C. Dai (=Piptoporus betulinum)

Hosts: Birch. Identification: Annual, leathery, shelving, light and corky conk. An extremely common saprobe of dead trees, also occurring on dead portions of live trees. Top: whitish to tan to mousy-brown, smooth or somewhat scaly. Lower margin of the cap incurving and projecting below the pore surface. Bottom: white pore layer when fresh, becoming yellowish to tan and slightly tooth-like when older. Interior: thick, white, firm, spongy when fresh and separates easily from the pore layer. Becomes corky with age. Damage: Yellowish brown cubical rot of sapwood and heartwood. Advanced decay is very light weight and crumbles easily. Remarks: Used as a bandage to prevent bleeding and infection in traditional medicine and has anti-inflammatory properties. Also called the Razor Strop fungus as barbers used the flesh to sharpen their razors.

Inonotus obliquus (Ach. ex Pers.)

Current Status: Inonotus obliquus, also known as Chaga, is widespread in Interior and Southcentral Alaska on birch and has been mapped from the Kenai Peninsula north to the Brooks Range, and east to the Canadian border. In 2022, this disease was not recorded by FHP staff during ground detection surveys, but 17 research grade observations were recorded in iNaturalist in Interior and Southcentral Alaska. Observations were made around Fairbanks, Talkeetna, Anchorage, the Kenai Peninsula, and along the south end of Lake Clark. As a true stem decay, this fungus does not require a wound as an infection court, nor does it invade dead trees. Diplodia gall appears superficially similar but occurs on aspen rather than birch.

Hosts: Birch. Identification: Annual, leathery, shelving, light and corky conk. An extremely common saprobe of dead trees, also occurring on dead portions of live trees. Top: whitish to tan to mousy-brown, smooth or somewhat scaly. Lower margin of the cap incurving and projecting below the pore surface. Bottom: white pore layer when fresh, becoming yellowish to tan and slightly tooth-like when older. Interior: thick, white, firm, spongy when fresh and separates easily from the pore layer. Becomes corky with age. Damage: Yellowish brown cubical rot of sapwood and heartwood. Advanced decay is very light weight and crumbles easily. Remarks: Used as a bandage to prevent bleeding and infection in traditional medicine and has anti-inflammatory properties. Also called the Razor Strop fungus as barbers used the flesh to sharpen their razors.

Phellinus tremulae (Bondartsev) Bondartsev & P.N. Borisov

Current Status: In 2022, seven new observations of P. tremulae were recorded by FHP staff in Interior Alaska near Fairbanks and in Southcentral Alaska on the Kenai Peninsula, and one additional research grade observation was contributed via iNaturalist near Fox. This fungus occurs throughout the range of aspen in Alaska and is considered the most important decay pathogen of aspen species in the Northern Hemisphere. Phellinus tremulae appears identical to Phellinus spp. on birch but only occurs on aspen.

Hosts: Trembling aspen (P. tremulae) and possibly balsam poplar. Identification: Perennial, woody, vaguely hoof-shaped conk. Occurs on live trees but can persist as a saprobe years after trees die. Top: dark brown to greyish-black to black, many small cracks. Bottom: convex, light brown with tiny circular pores. Interior: rusty-brown with numerous white flecks. Damage: Initial decay is yellowish to yellowish-white, surrounded by a distinct dark zone line. Advanced decay is spongy or punky with numerous irregular, black zone lines. The presence of conks indicates considerable heart rot. Remarks: Used to make punk ash. Phellinus igniarius is very common on live birch and looks identical to P. tremulae on aspen. Phellinus tremulae is the most important heart rot organism of aspen; in its commercial range in the Lower 48, it is reported to cause more volume loss than any other disease of aspen.

Phellinus igniarius (L.) Quél.

Current Status: There were 29 observations of Phellinus igniarius sensu lato recorded by FHP staff in 2022. This included detections from thinleaf alder (1), red alder (15), Sitka alder (4), Alaska paper birch (2), paper birch (1), balsam poplar (1), Scouler’s willow (1), and coastal willow species (5). Thirteen research grade observations were made in iNaturalist, mostly on birch, with two notable finds on willow in western Alaska near Bethel and one on red alder on Prince of Wales Island. Conks from the genus Phellinus were first noted on red alder in Southeast Alaska last year and preliminarily identified based on PCR sequencing of the ITS region as P. lundellii, though sequencing multiple regions of DNA will be needed to confirm. We have also collected resupinate conks (growing flat against the stem) and apparently saprophytic conks from dead red alder stems for molecular identification.

Forest Health Protection has initiated a project with Research Plant Pathologist Dr. Mee-Sook Kim (USDA Forest Service Pacific Northwest Research Station) to explore the diversity of Phellinus species that occur on birch, willow, and alder in Alaska through molecular identification. Recent phylogenetic work indicates that there are eight species of Phellinus that cause white trunk rot of hardwoods in North America: P. alni, P. arctostaphyli, P. nigricans, P. laevigatus, P. lundellii, P. populicola, P. tremulae, and P. tuberculosus (Brazee 2015, http://dx.doi.org/10.3390/f6114191). Phellinus igniarius is notably absent from this list, yet it has long been considered a key white rot of northern hardwoods. The 2015 phylogenetic study identified Phellinus nigricans on dwarf and paper birch and Phellinus alni on alder in Alaska. Phellinus igniarius sensu lato (how we will refer to this species complex until we have more complete information) is widespread and common in Alaska on both live and dead birch trees and occurs less frequently on alder and willow species.

Hosts: Birch (P. igniarius). Identification: Perennial, woody, vaguely hoof-shaped conk. Occurs on live trees but can persist as a saprobe years after trees die. Top: dark brown to greyish-black to black, many small cracks. Bottom: convex, light brown with tiny circular pores. Interior: rusty-brown with numerous white flecks. Damage: Initial decay is yellowish to yellowish-white, surrounded by a distinct dark zone line. Advanced decay is spongy or punky with numerous irregular, black zone lines. The presence of conks indicates considerable heart rot. Remarks: Used to make punk ash. P. igniarius is very common on live birch and looks identical to P. tremulae on aspen. Phellinus tremulae is the most important heart rot organism of aspen; in its commercial range in the Lower 48, it is reported to cause more volume loss than any other disease of aspen.

Fomes fomentarius (L.) Fr.