Onnia tomentosa

Onnia tomentosa is a species of fungus in the family Hymenochaetaceae commonly known as the woolly velvet polypore. It is frequently found in coniferous forests at higher altitudes, often growing in large groups, rather rare at lower altitudes. It is a plant pathogen, and causes tomentosus root rot, primarily in spruce.[1] It was formerly known as Inonotus tomentosum (Fr.) Teng until molecular phylogenetic analysis led to major revisions in the classification of the Hymenochaetaceae.[2]

Onnia tomentosa
Scientific classification
Kingdom:
Fungi
Division:
Basidiomycota
Class:
Agaricomycetes
Order:
Hymenochaetales
Family:
Hymenochaetaceae
Genus:
Onnia
Species:
O. tomentosa
Binomial name
Onnia tomentosa
(Fr.) P.Karst. (1889)
Synonyms
  • Polyporus tomentosus Fr. (1821)

Description
Onnia tomentosa, Albu Parish, Estonia.

The cap is flat when young, with a blunt, rounded and yellowish-white margin, later with a slightly depressed centre and contoured in a wave pattern towards the rim, which has a rather sharp edge when old. It is covered in felt that is grey when young and rusty brown when old, up to 10 cm (3.9 in) in diameter. The stem is short and thick, dark brown to almost black. The flesh is hard and fibrous, and ochre brown under the cap surface.

Most commercially important conifers in Canada, including white spruce, are attacked by Inonotus tomentosus (Fr.) Teng also known as Onnia tomentosa (Whitney 1978).[3] This fungus produces a white pocket rot commonly called Tomentosus root rot in both roots and butts of naturally seeded or planted conifers. White spruce and black spruce were found to be the 2 most susceptible species in an inoculation test in Saskatchewan (Whitney 1964),[4] and high losses to root rot, in large part due to I. tomentosus, affected white spruce plantations at Grand-Mère QC (Lachance 1978).[5] In white spruce plantations, mortality in groups of 2 or 3 trees usually occurs at about age 30–35 years (Whitney 1977),[6] but younger trees can also be killed (Whitney 1993).[7] Occasional trees as young as 10 years of age are infected (Whitney and Timmer 1983).[8] Seventeen white spruce plantations 43–58 years old in Ontario incurred an average of 0.7% mortality annually over a 6-year study period (Whitney 1993).[7] Average accumulated mortality of dominant and codominant trees was 10.3% for all plantations in that study. Tomentosus root rot was found in more than half the stumps after clearcutting in a plantation at Searchmont, Ontario, but decay and stain had not yet reached stump height (Whitney 1962).[9]

Similar species

Coltricia perennis is similar, but has a weakly circularly zoned, bare cap. The flesh of the cap is stained uniformly.

References
  1. Ryvarden, Leif; Gilbertson, Robert L. (1986). North American Polypores. Oslo, Norway: Fungiflora. ISBN 0-945345-06-2.
  2. Wagner, T Fischer M. (2002). "Proceedings towards a natural classification of the worldwide taxa Phellinus s.l. and Inonotus s.l., and phylogenetic relationships of allied genera". Mycologia. 94 (6): 998–1016. doi:10.2307/3761866. JSTOR 3761866. PMID 21156572.
  3. Whitney, R.D. 1978. Polyporus tomentosus root and butt rot of trees in Canada. p. 283–297 in Dimitri, L. (Ed.), Proc. 5th Internat. IUFRO Conf. on Problems of root and butt rot in conifers, Aug. 1978, Kassell. Germany.
  4. Whitney, R.D. 1964. Inoculation of eight Saskatchewan trees with Polyporus tomentosus. Can. Dep. For., Ottawa ON, Bi-mo. Res. Notes 28(4):24.
  5. Lachance, D. 1978. The effect of decay on growth rate in a white spruce plantation. For. Chron. 54(1):20–23.
  6. Whitney, R.D. 1977. Polyporus tomentosus root rot of conifers. Can. Dep. Environ., Can. For. Serv., Ottawa ON, For. Tech. Rep. 18. 12 p.
  7. Whitney, R.D. 1993. Damage by Tomentosus root rot in white spruce plantations in Ontario, and the effects of thinning on the disease. For. Chron. 69(4):44.
  8. Whitney, R.D.; Timmer, V.R. 1983. Chlorosis in planted white spruce at Limestone Lake, Ontario. Can. Dep. Environ., Can. For. Serv., Sault Ste. Marie ON, Inf. Rep. O-X-346. 16 p.
  9. Whitney R.D. (1962). "Polyporus tomentosus Fr. as a major factor in stand-opening disease of white spruce". Can. J. Bot. 40: 1631–1658. doi:10.1139/b62-158.
  • E. Garnweidner. Mushrooms and Toadstools of Britain and Europe. Collins. 1994.
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