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Remarks (public):For a complete description including images see 
Remarks (internal):The disease is most important in Britain, as the cause of deaths in pole crops aged 20-30 years, but can kill trees between 15 and 60 years of age. Control is achieved by avoidance of fires on site which are hot enough to affect the soil.
Description type:Non-original description 
Description:Rhizina undulata Fr., Systema mycologicum 2: 33, 1822.
= Rhizina inflata (Schäff.) Quel., 1886.
Hymenophore flat, convex or undulating, often irregularly lobed, dark brown or black with paler margins, the hymenophore often extending to several cm diam., 1-2 mm thick; flesh reddish-brown, tough, fibrous, under surface pale ochraceous, bearing numerous cylindrical branched whitish root-like structures. Asci operculate, 350-450 x 10-14 µm, with 8 monostichous or obliquely monostichous ascospores. Ascospores non-septate, fusiform, 24-40 x 9-11 µm with a hyaline apiculus at each end; some spores are slightly roughened but this does not appear to be a consistent feature. Paraphyses stiff, hair-like, brown, 4 µm diam.; interspersed between the asci and extending beyond, the swollen tips forming a protective surface covered with an amorphous brown crust. Germination of ascospores isolated on to PDA is greatly stimulated by a short period of heat treatment (35-45°C) and then incubation at 22°C (Jalaluddin, 1967); growth is then rapid, producing abundant yellowish-white mycelium composed of hyphae 3-4 µm wide and presenting a woolly appearance as the culture gradually turns orange brown. Conidia and chlamydospores not were observed but swollen hyphae up to 14 µm diam. develop after a few days.
Hosts: On Larix decidua, L. leptolepis, Picea abies, P. sitchensis, Pinus contorta, P. nigra, P. maritima, P. sylvestris, P. elliottii var. elliottii, P. patula, P. pinaster, P. strobus, Pseudotsuga menziesii, Tsuga mertensiana, T. heterophylla, Abies alba among softwoods, and Castanea sativa, a hardwood.
Disease: Group dying of conifers. The disease is characterized by the death of seedlings or plantation trees in groups, which are always found around old fire sites. The roots of infected trees are covered with white or yellowish mycelial strands and fruit bodies of the fungus are formed on the litter at the base of diseased trees during wet weather.
Geographical distribution: Europe (Belgium, Britain, Bulgaria, Finland, France, Germany, Netherlands, Poland, Republic of Ireland, Sweden, USSR (Lithuania & Latvia SSR)); Africa (Rhodesia, Ngwane (formerly Swaziland), South Africa); USA (Pacific N.W., Minn., Calif., Md, NY); Canada (BC).
Physiological specialization: None known.
Transmission: By ascospores through the soil, after they have been activated by exposure to temperatures of 35-45°C in the neighbourhood of pine roots.
Literature: Murray & Young, For. Rec. 46, 19 pp., 1961; Jalaluddin, Trans. Br. mycol. Soc. 50: 449-472, 1967; Gremmen, Ber. BosbProefstn, Dorschk. 26, 1962.

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