False Tinder Conk/Punk Ash

Phellinus igniarius (L.) Quél.
Phellinus tremulae (Bondartsev) Bondartsev & P.N. Borisov

Host(s) in Alaska:

Alaska paper birch (Betula neoalaskana) for P. igniarius
Trembling aspen (Populus tremuloides) for P. tremulae

Habitat(s): boles, branches

Current Status & Distribution in Alaska (2021 Update)

Phellinus igniarius was recorded at six new locations in 2021; several trees were found at two Southcentral locations on the Kenai Peninsula near Moose Pass and four Interior locations near Fairbanks. Up to 15 infected trees were found at one location near Fairbanks, although most sites have smaller numbers. Nineteen research grade observations were made in iNaturalist, with two notable finds in Southeast near Skagway and in Southwest near Dillingham where we had not previously recorded this disease. This disease is extremely widespread and common in Alaska on both live and dead birch trees (see Map). Although reported on many hardwood species elsewhere, in Alaska we have only observed it on birch, alder, and willow species. This fungus is known as an important white rot of hardwoods in the cooler regions of northern temperate forests. 

Eleven new observations of P. tremulae were recorded in the Interior and Southcentral near Fairbanks, Anchorage, and on the Kenai Peninsula near Moose Pass by FHP staff. Five research grade observations were made through iNaturalist in 2021 near Anchorage, on the Kenai Peninsula, and near Fairbanks. We have mapped a total of 41 observations of P. tremulae although it is common and occurs throughout the range of aspen (see Map). This fungus is considered the most important decay pathogen of aspen species in the Northern Hemisphere. P. tremulae appears identical to its close relative P. igniarius but only occurs on aspen. 

The trunk rot disease caused by both fungi is extremely widespread and common in Alaska on both birch and aspen.

Historic Activity

Phellinus tremulae is considered the most important decay pathogen of aspen species in the Northern Hemisphere and is reported to cause more volume loss than any other aspen disease. Although P. igniarius has been reported on many hardwood species elsewhere, in Alaska it is primarily observed on birch, and rarely on alder and willow species.

The conks of both P. tremulae and P. igniarius are used to make punk ash, a tobacco additive and medicine derived from burnt conks. Ethnobotanical and traditional uses of the fungus are described on this 2005 webpage by Pleninger and Volk.

Symptoms, Biology, & Impacts

Phellinus tremulae only occurs on aspen, although the conk appears identical to P. igniarius. The conks of both species are perennial, woody, and vaguely hoof shaped. They occur on live trees but can persist saprophytically for years after a tree dies. The top of most conks are dark brown to greyish-black to black and slightly glossy with many small cracks. The bottom is convex and light brown with tiny circular pores. On the inside, conks are rusty-brown with numerous white flecks.

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.

Survey Method

This disease is surveyed through informal ground observations and boreal forest monitoring plots.

Detection Maps

False tinder conk (Phellinus igniarius and Phellinus tremulae) detection locations in Alaska based on plot data and informal geo-referenced observations as of 2021. Modeled aspen and birch distribution was developed by the Forest Health Assessment and Applied Sciences Team (FHAAST; formerly FHTET) in 2011 (240m-resolution, presence based on dominant tree species by tree diameter).

Resources and Links

Hebertson, L. 2005. Guide for the Management of Aspen Heart Rot. USDA-FS Regions 1 and 4. 6pp. Available here.

Worral, J. and M. L. Fairweather. 2005. Decay and Discoloration of Aspen. USDS-FS Forest Insect and Disease Leaflet FS-R6-RO-FIDL#149. 7pp. Available here.

Content prepared by Lori Winton, PhD Forest Pathologist, Forest Health Protection, loretta.winton@usda.gov.

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