Herpotrichia juniperi (Duby) Petr.
(= Herpotrichia nigra R. Hartig)
Neopeckia coulteri (Peck) Sacc. in Peck
(=Herpotrichia coulteri (Peck) Bose)
Ascomycotina, Dothideales, Pleosporaceae
Hosts: Herpotrichia juniperi is found only on conifers. In B.C., it has been reported on amabilis and subalpine fir, yellow cedar, juniper, Engelmann, Sitka, and white spruce, lodgepole pine, yew, and mountain and western hemlock. Elsewhere in North America it has also been reported on grand fir, incense-cedar, mountain heather, Douglas-fir, western white pine,and western redcedar. Neopeckia coulteri is generally found only on pines. In B.C., on lodgepole and white-bark pine. Elsewhere in North America, on Engelmann spruce and western white pine.
Distribution: These fungi are widely distributed throughout the range of their hosts in B.C., particularly at higher altitudes.
Identification: These diseases are readily identified by the brown, felt-like masses of mycelium that cover twigs and branches (Figs. 52a, 52b). Fungal growth is prolific on branches that are buried under snow. As the snow melts, and felts are exposed, fungal development ceases. Under the snow, the mycelium is grey in colour. Freshly exposed felts are dark brown-black, weathering to grey-brown. Spherical black fruiting bodies develop on and in mycelial mats the second year after formation, but are very difficult to see. The macroscopic signs and symptoms of both diseases are very similar; the two are differentiated by host preference and microscopic features.
Microscopic Characteristics: Herpotrichia juniperi: Pseudothecia dark brown, globose, partially hidden in a felt-like subiculum of dark brown hyphae, 200-450 µm diameter, with a definite apical pore, wall of polygonal cells 20-40 µm thick, covered with brown, septate hyphae. Asci cylindrical to subclavate, 8-spored, bitunicate, 115-190 x 12-18 µm. Ascospores uniseriate or obliquely biseriate, hyaline and 1-septate at first, becoming brown and 3-4 septate, elliptical, constricted at median septum, with a mucous sheath, 25-34 x 8-12 µm. Pseudoparaphyses filiform, hyaline.
Herpotrichia coulteri: Pseudothecia dark brown, globose, single or in small groups, formed on a subiculum of felty brown hyphae, 250-500 µm diameter, with a distinctly papillate pore, wall of thick-walled pseudoparenchyma, covered by brown hyphae. Asci cylindrical, short-stalked, 8-spored, bitunicate, 140-210 x 14-20 µm. Ascospores monostichous, elliptical, dark brown, 1-septate, constricted, with a dark epispore, 10-28 x 7-10 µm. Pseudoparaphyses hyaline, filiform, sparsely branched.
Damage: Branch dieback or death occurs on seedlings and the lower branches of larger trees. Although rarely a problem in natural forests, this disease can cause significant loss in bareroot nurseries and young plantations where sufficient snow is present.
Remarks: Another "snow mould" that occurs on true firs and Douglas-fir is Phacidium abietis (Dearn.) Reid & Cain, but it does not invade branches or cause dieback.
Sims, H. R. 1967. On the ecology of Herpotrichia nigra. Mycologia 59:902-909.
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Figure 52a: Brown felt-like mycelial masses characteristic of Herpotrichia juniperi covering needles and branches of spruce.