First Report of Inonotus tomentosus, the Cause of Tomentosus Root Disease, from the Yukon Territory

Abstract

During forest pest surveys in the Watson Lake area (60°N 129°W) of the Yukon Territory (YT), sporocarps, tentatively identified as Inonotus tomentosus (Fr.:Fr.) S. Teng, were observed in association with old mortality (25+ years) and root rot of old (200 to 275 years) white spruce (Picea glauca (Moench) Voss) growing in riparian zones. I. tomentosus primarily attacks spruce throughout North America (1). Cultures from collected sporocarps and from a decayed root of a living tree produced chlamydospore-like hyphal swellings typical of I. tomentosus(2). Although three of the collected sporocarps were bracketlike, none bore hooked hymenial setae, typical of I. circinatus (Fr.) R. L. Gilbertson. All sporocarps collected possessed straight setal hyphae and were confirmed as I. tomentosus (1). These specimens are filed at the Pacific Forestry Centre herbarium as DAVFP 25375 and DAVFP 25376. This is the first western Canadian report of this major conifer root disease north of about 55°N latitude. Sporocarps have been collected at about the same latitude as Watson Lake, but from 21° farther west, near Fairbanks and Anchorage, AK (L. Trummer, USDA For. Serv. Anchorage, AK, personal communication). For several years, other stump and root decay samples have been collected in the YT as far west as Haines Junction (about halfway between Anchorage and Watson Lake), but the pathogen has never been successfully cultured nor sporocarps collected. Because the decay pattern can be confused with that caused by Phellinus pini (Thore:Fr.) A. Ames, and other diagnostic features were lacking, there has been a reluctance to accept that I. tomentosus is present in the YT. However, it seems likely that I. tomentosus is much more widespread north of 55°N in western Canada than has previously been recognized. References: (1) R. L. Gilbertson and L. Ryvarden. North Am. Polypores. Fungiflora 1:403, 1986. (2) R. S. Hunt. Can. J. Plant Pathol. 19:307, 1997.