Armillaria sinapina (Bérubé and Dessureault)
(=NABS V) (NABS stands for "North American Biological Species")
Armillaria gallica Marxmüller and Romagnesi
(=Armillaria bulbosa (Barla) Kile and Watling; =NABS VII)
Armillaria cepistipes Velanovsky
Armillaria nabsnona Volk and Burdsall
Hosts: The Armillaria species listed above have been found on living broadleaved trees and as saprophytes on stumps of these trees after felling. Occasionally, A. sinapina has been found on stumps of conifers. These Armillaria species are weakly pathogenic on living broadleaved trees and do not kill healthy conifers.
Armillaria sinapina: 49°N to approximately 57°N (widespread and common).
Armillaria gallica: southern Vancouver Island (Garry oak habitat)
Armillaria cepistipes: collections from Hope and Stewart, B.C.
Armillaria nabsnona: coastal and southwestern B.C.
Identification: Of the above-listed species only A. sinapina and A. nabsnona (the latter only in SW B.C.) will be encountered in commercial coniferous forests. The ranges of A. ostoyae and A. sinapina overlap south of approximately 52-53 °N in B.C. It is difficult to distinguish between A. ostoyae and A. sinapina in a colonized stump because both produce white mycelial fans in the bark and cambial zone. However, A. sinapina produces an extensive network of monopodially-branched rhizomorphs while A. ostoyae produces small amounts of dichotomously-branched ones. In addition, the sporophores of A. sinapina are usually darker in colour, smaller, and more numerous than those of A. ostoyae.
On broadleaved trees where the disease is advanced, top growth and the number and size of leaves may be reduced, particularly when the trees are stressed by other predisposing agents. Decay is white to yellow in colour and has a watersoaked appearance.
In mixed coniferous/broadleaved stands, the presence of diseased conifers indicates that A. ostoyae is present, whereas colonized stumps or diseased broadleaved trees suggests A. sinapina but does not exclude A. ostoyae.
Damage: The damage caused by these weakly pathogenic Armillaria species on broadleaved trees is minor. The fungi appear to spread slowly in diseased trees that are often stressed by another agent. Where A. ostoyae and a weakly pathogenic species occur together in a managed commercial forest, the latter may reduce the damage caused by A. ostoyae by colonizing root systems, thereby denying them to A. ostoyae.
Remarks: Damage that may be caused by weakly-pathogenic Armillaria species can be reduced by maintaining a high level of tree vigour. In urban situations where broadleaved trees are damaged or killed, they should be replaced by a suitable conifer species.
Microscopic Characteristics: Basidiospores hyaline, dextrinoid, weakly cyanophilic, thin to moderately thick-walled, smooth or slightly verruculose or rugulose with broad, blunt usually prominent apiculus, lacking germ pore. Spore print white to cream colour, darkening on drying and in herbarium material. Growth in culture slow, mat cream-yellow or brown, hyphae simple septate, some with characteristic minute hairlike projections on side walls, laccase positive. Rhizomorphs present in older cultures. Nobles (1965): 2 6 10 16 20 32 37 39 47 54 55 (code for A. mellea).
Morrison, D. J., D. Chu, and A. L. S. Johnson. 1985. Species of Armillaria in British Columbia. Can. J. Plant Pathol. 7:242-246.
Morrison, D. J., G. W. Wallis, and L. C. Weir. 1988. Control of Armillaria and Phellinus root diseases: 20-year results from the Skimikin stump removal experiment. Can. For. Serv., Rep. No. BC-X-302.
Morrison, D., H. Merler, and D. Norris. 1992. Detection, recognition, and the management of Armillaria and Phellinus root diseases in the southern interior of British Columbia. Can. For. Serv., B.C. Min. For., FRDA Rep. No. 179.
Shaw, C. G. III and G. A. Kile. 1991. Armillaria Root Disease. USDA For. Serv. Agric. Hdbk. No. 691.