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White Trunk Rot of Conifers
Phellinus hartigii (Allesch. & Schnabl.) Bondartsev
(= Fomes hartigii Allesch. & Schnabl.)
(= Fomes robustus P. Karst.)
(=Phellinus robustus (P. Karst.) Bourd. & Galzin)
Basidiomycotina, Aphyllophorales, Polyporaceae
Hosts: In B.C., Phellinus hartigii has been reported on western hemlock, amabilis and subalpine fir, and Douglas-fir. In Oregon it has been found on yew.
Distribution: This fungus is widely distributed throughout the range of its hosts in B.C.
Identification: The fruiting bodies are perennial and vary in shape. When formed on the stem, they are hoof-shaped (triangular in longitudinal outline with upper and lower surfaces at angles of 45°), and 5-15 cm wide (Fig. 18a). The upper surface is dark brown to black while the lower surface is brown and poroid. When formed on the lower surface of branches, fruiting bodies are generally resupinate (Fig. 18b). The pores of all fruiting bodies are small (5-7 per mm) and circular in outline.
The decay sometimes occurs as a sector of infected wood extending in from the sapwood. The rot is often found in association with wounds or dead branches and with dwarf mistletoe infections that have killed part of the cambium. Early stages of decay appear as a straw-coloured to purple stain that may be irregular in shape. In the late stages, the wood has a bleached appearance with occasional light brown areas or streaks (Fig. 18c). Zone lines are usually numerous in the decayed wood.
Microscopic Characteristics: Hyphae in the context of the fruiting body thick-walled, aseptate, or rarely simple septate. Setae lacking. Basidiospores globose to subglobose, hyaline, smooth, slightly thick-walled, IKI-, 6-7.5 x 5-6.5 µm. Growth in culture slow, mat white, cream-umber, reverse brown, laccase positive. Stalpers: 1 3 4 (9) (10) (11) (13) 17 21 (22) (25) (30) (34) 35 38 (46) 48 50 52 53 (54) 57 67 80 82 83 90.
Damage: Trees damaged by white trunk rot are prone to wind damage, usually breaking within 6 m of the ground. Decay is usually localized to tissues near the point of infection, but spreads 1-2 m up and down from each fruiting body.
Remarks: The taxonomy of this fungus has been complicated by its morphological variation on different hosts. As a result, many names have been applied to the organism. In the past, many P. hartigii specimens were named Fomes or Phellinus robustus, a name that is now restricted to a related fungus on hardwoods. Another fungus, Poria tsugina (Murrill) Sacc. & Trott., now recognized as Phellinus punctatus (Fr.) Pilát, has resupinate fruiting bodies that are sometimes confused with those of P. hartigii.
References:
Bondartsev, A. S. 1953. The Polyporaceae of the European USSR and the Caucasus. Akad. Nauk SSSR, Moscow.
Gilbertson, R. L. and L. Ryvarden. 1987. North American Polypores. 2:575. Fungiflora, Oslo.
Figures
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Figure 18a: Fruiting bodies of Phellinus hartigii on a stem of western hemlock.
Figure 18b: Fruiting bodies of Phellinus hartigii on a branch stub of western hemlock.
Figure 18c: Decay caused by P. hartigii in a cross-section of a western hemlock branch.