Atropellis piniphila (Weir) Lohman & Cash
Ascomycotina, Helotiales, Helotiaceae
Hosts:Atropellis piniphila is found only on pine. In B.C., it has been reported on lodgepole and ponderosa pine. Elsewhere in North America it has also been found on jack, loblolly, shortleaf, Virginia, and whitebark pines.
Distribution: Atropellis canker is common throughout the southern two thirds of the province, but has not been reported north of a line extending from Hazelton to Fort St. John.
Identification:Perennial cankers form on branches and stems of lodgepole pine causing resinosis, distortion in growth, and a blue-black stain of the sapwood and heartwood (Figs. 39a, 39b). Infection generally occurs through undamaged bark near branch nodes on stems 15-30 years old. Cankers, which are usually centered around a branch stub, increase in size by approximately 5 cm in length and 0.6 cm in circumference annually, and can reach 3 m in length. Two types of fruiting bodies, pycnidia and apothecia are often present. Pycnidia usually appear on young cankers, before apothecia, are globose, 0.6-1.6 mm across when wet, and produce conidia in a creamy mucilaginous mass when wet. Apothecia are stalked, black saucer-like structures, 0.6-4.5 mm in diameter, which form singly or in groups in the center of the canker and are present throughout the year (Figs. 39c, 39d). Ascospores are produced by apothecia and are disseminated by wind for distances up to 100 m.
Although other stem disorders result in resinous cankers, A. piniphila is readily distinguished by the blue-black staining of the sapwood (and to a lesser extent, the heartwood) underlying the canker (39d, 39e). The sapwood at the leading edge of the canker is stained a reddish-brown colour.
Microscopic Characteristics: Apothecial tissue colours 5% KOH bluish-green. Hymenium purplish in cross section. Asci clavate, 8-spored, IKI-, 90-160 x 10-15 µm. Ascospores ellipsoid-fuscoid, hyaline, 0-1 septate, 16-28 x 4-7 µm. Paraphyses filiform, septate, branched. Conidiophores verticulate, 30-65 µm long, terminating in a phialide, 30-40 µm long. Conidia rod-shaped, nonseptate, hyaline, 4-8 x 1-1.7 µm.
Damage: Damage occurs as mortality, growth reduction, and reduction of value for both chips and finished wood products. The high resin content also interferes with penetration by wood preservatives. Mortality occurs when stems are girdled by large or multiple cankers, and may be severe in dense stands, particularly those growing on dry sites.
Remarks: Trees less than 15 yrs old are resistant to infection. In older trees, most infections occur on tissues that are 10-30 yrs old at the time of infection. Virtually no infections occur on tissues less than 5 yrs or greater than 40 yrs old. High levels of infection have been observed after fire in lodgepole pine regeneration that are infected by diseased residual trees not killed in the fire. A closely related fungus, Atropellis pinicola Zeller & Good. is less commonly found in B.C. This fungus attacks branches of western white pine, and occasionally, lodgepole pine.
References:
Baranyay, J. A., T. Szabo, and K. Hunt. 1973. Effect of Atropellis canker on growth and utilization of lodgepole pine. Can. For. Serv., Inf. Rep. BC-X-86.
Hopkins, J. C. 1963. Atropellis canker of lodgepole pine: etiology, symptoms, and canker development rates. Can. J. Bot. 41:1536-1545.
Hopkins, J. C. and B. Callan. 1991. Atropellis canker. Can. For. Serv., Forest Pest Leaf. No. 25. Victoria, B.C.
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Figure 39a: Cankers caused by Atropellis piniphila on lodgepole pine.
Figure 39b: Cankers caused by Atropellis piniphila on lodgepole pine.
Figure 39c: Canker on young lodgepole pine showing apothecia and blue stain in sapwood.
Figure 39d: Atropellis apothecia.
Figure 39e: Blue staining of sapwood that follows annual growth rings.