Hardwood Stem Decays

Ganoderma applanatum (Pers.) Pat.

Current Status: Of 13 observations of Ganoderma applanatum made during ground detection surveys in 2023, seven were on western hemlock and two on red alder in Southeast Alaska, while the remaining observations were on balsam poplar and Alaska birch in Southcentral and Interior Alaska. Twenty-seven research grade observations were contributed through iNaturalist from the same general locations but also near Talkeetna and the Kenai Peninsula. Ganoderma applanatum is likely a species complex, found on both hardwoods and conifers in coastal Alaska. On hardwoods in Southeast Alaska, the conk tends to be thinner and has a paler upper surface without the abundant dusting of brown spores.

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 throughout Interior and Southcentral Alaska and has been mapped on birch from the Kenai Peninsula north to the Brooks Range, and east to the Canadian border. In 2023, this disease was recorded at four locations during ground detection surveys near Fairbanks and Clear in the Interior, and near Anchorage and on the Kenai Wildlife Refuge in Southcentral Alaska. Fourteen research grade observations were recorded via iNaturalist in Fairbanks, Denali Park, Talkeetna, Wasilla, Palmer, and the greater Anchorage area in Interior and Southcentral Alaska, as well as near Skagway, where we had not previously documented the disease. 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: Sixteen new observations of Phellinus tremulae were recorded by FHP staff in Interior Alaska near Fairbanks, Donnelly, Healy, and along the Steese Highway north of Twin Buttes, and in Southcentral Alaska in Anchorage and on the Kenai National Wildlife Refuge. One additional research grade observation was contributed via iNaturalist near Anchorage. This fungus is common 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 other Phellinus spp. on birch but only occurs on aspen and rarely balsam poplar.

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: Forest Health Protection is continuing 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. 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, alder, and willow species. There were 59 observations of Phellinus igniarius sensu lato recorded by FHP staff in 2023. This included detections on Alaska paper birch (46), red alder (5), Siberian alder (2) thinleaf alder (2), Sitka alder (1), and coastal willow species (3). Several specimens including conks were sent to the Kim lab for further DNA analyses. Twenty research grade observations were made in iNaturalist, the bulk on birch in Southcentral Alaska between Anchorage and Palmer, but also Soldotna, Talkeetna, and north to Denali Park, and one observation in Southeast Alaska on red alder near Juneau.  

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.

Cureent Status: In 2023, Fomes fomentarius was mapped at 31 locations from the Ray Mountains east to Circle and south to the Alaska Range in the Interior and around Anchorage and Kenai Lake in Southcentral Alaska. There were 69 research grade observations made via iNaturalist between Haines and Skagway in Southeast Alaska; Anchorage, Palmer, Talkeetna, and Soldotna in Southcentral Alaska; along Lake Clark and Naknek Lake on the Alaska Peninsula; and near Denali Park and Fairbanks in the Interior. This disease is widespread on birch in Alaska.