Hunt and Etheridge 1995 True Heart Rots of Pacific Region

ISBN 0-662-23897-4 Cat. No. Fo 29-6/55-1995E 55 FOREST True heart-rots of the Pacific region Pest By R.S. Hunt and D.E. Etheridge LEAFLET Pacific Forestry Centre Introduction ➀ Decay caused by root-, butt- and trunk-rotting fungi (Basidiomycetes) is responsible for an estimated annual loss of timber in British Columbia that exceeds 10 million cubic metres (14). Obviously, accumulated decay vol- umes are staggering. The bulk of this volume loss is due to heart-rot in trunks of living trees. Among the most destructive of the heart-rots in British Columbia ➁ forests are those caused by true heart-rotting fungi. These are so- named because the characteristic decay is usually confined to the true heartwood. They are the only species that consistently produce fruiting bodies on living trees. They may also produce sterile structures known as “punk knots” or “swollen knots.” Unlike other Figs. 1 and 2. Potential infection courts of Echinodontium tinctorium on living branches heart-rotting fungi, these species of western hemlock. Fig. 1. Recently dead, adaxial branchlets, about 1 mm in diameter, never occur as primary invaders of on a 10-year-old branch. Fig. 2. Stubs of branchlets on a 50-year-old branch (see slash and dead material, or cause above), recently broken off close to the basal callus (arrows), provide actual entry points. damage to timber in service, although they may continue to develop in fresh- ly cut logs in the forest for varying scars, are therefore unlikely to prevent gus (Echinodontium tinctorium (Ell. & periods. They also differ in their mode infection by these fungi. Ev.) Ell. & Ev.) and the ring scale fun- of attack, since mechanical injuries do gus (Phellinus pini (Thore: Fr.) A. not appear to be the principal infection Only the true heart-rots will be Ames) on conifers, the false tinder fungi courts for these species. Control mea- dealt with in this leaflet. There are four (P. tremulae (Bond.) Bond. & Poriss. in sures designed to reduce wounding of species of true heart-rotting fungi in Bond.) on aspen, and P. igniarius trees, or as protective treatments to British Columbia: the Indian paint fun- (L.:Fr.) Quél. on other hardwoods. Natural Resources Ressources naturelles Canada Canada Canadian Forest Service canadien Service des forêts Hosts and distribution (Populus trichocarpa Torr. & Gray), maple (Acer spp.), Pacific dogwood Echinodontium tinctorium, confined to (Cornus nuttalli Andub.), and willow western North America, is common on (Salix spp.) (16). Phellinus tremulae true firs (Abies spp.) and hemlock is a species recently segregated from (Tsuga spp.), and occasionally occurs P. igniarius. Its only host in North on Douglas-fir [Pseudotsuga menziesii America is aspen (P. tremuloides (Mirb.) Franco], western redcedar Michx.), in which it is the most impor- (Thuja plicata D. Don), and spruce tant decay fungus. There have been (Picea spp.). True firs are highly sus- no systematic studies in this province ceptible throughout most of their range on site relationships and distribution in British Columbia, while western hem- for these fungi. Phellinus tremulae lock [Tsuga heterophylla (Raf.) Sarg.] damage can be severe, particularly in suffers moderate to severe levels of stands over 30 years of age. This dis- attack in specific habitats, principally in ease may vary considerably from one interior forests, at higher elevations on stand to another, with decay lowest in the coast (18), and on below-average more thrifty trees, perhaps as a result sites (9). It has not been reported on of interclonal variations (13, 15, 20). the Queen Charlotte Islands (8). Life history of the Phellinus pini has a wide distribution in the North Temperate Zone, and Indian paint fungus is one of the most common heart-rotting fungi in British Columbia. It is Of the true heart-rotting fungi, only the reported on all conifers except life history of Echinodontium tinctori- Chamaecyparis nootkatensis (D. Don) um has been studied in detail. Enough Spach, Juniperus scopulorum Sarg. information about the infection pro- and Taxus brevifolia Nutt. (16), but it cess is now available to question the is noted on these genera elsewhere long-held belief that these fungi enter (7). It occurs frequently on mature the heartwood through old, dead Fig. 3. Echinodontium tinctorium fruiting pines (Pinus spp.), western hemlock, branch stubs. For example, in western bodies on a living western hemlock tree the spruces, western larch [Larix occi- hemlock, infection courts of the Indian dentalis Nutt.], Douglas-fir, and western redcedar. Generally, true firs are much less susceptible to Phellinus pini than other hosts, but amabilis fir in the Kitimat region appears to be an exception (10). Phellinus pini probably causes more cull in Yukon spruce than any other agent. No systematic attempt has been made to correlate the occurrence of this fungus with forest type or site. There is evidence, however, of local variations: in British Columbia, infections tend to occur at younger ages more frequently on above-average sites (11). Phellinus igniarius attacks a vari- ety of broadleaf species throughout the northern hemisphere. In British Columbia, it causes moderate damage to birch (Betula papyrifera Marsh.), and has been reported on alder (Alnus rubra Bong.), apple Fig. 4. Bracket-like fruiting bodies of Phellinus pini (Malus sp.), arbutus (Arbutus menziesii Pursh), black cottonwood 2 The fruit body, or conk, is perennial, and may function for 12 or more years. One or two spore layers may be formed each year. Basidiospores are released into the air throughout the year during periods of rain, and especially in late fall and early spring when rain follows below-freezing temperatures. Phellinus pini is believed to have a similar life history (11). Since there is less decay due to P. tremulae in aspen when the lower branches of trees are removed (15) and P. tremulae can be isolated from small twigs (12), it may have a similar life history also. Fig. 5. Perennial hoof-shaped fruiting body of Echinodontium tinctorium, showing fissured Recognition upper surface and coarsely spined undersurface The fruit body paint fungus are almost certainly con- “resting spores.” The quiescent period The most conspicuous and reliable fined to living branches, which may may last for a considerable time – indicators of heart-rot caused by these provide the only route through which from the first appearance of infection fungi are the perennial conks, or fruit- infections reach the heartwood (6). courts on nonvigorous branches ing bodies, that generally form on the (around 40 years of age) until penetra- underside of dead branch stubs of liv- Infection occurs in late fall or tion of the trunk occurs (which may ing trees (Figs. 3 and 4). Recognition early spring when a single spore not be for another 100 years). of the common conks is also the best comes in contact with a suitable infec- Conditions associated with death and way to identify the causal organisms. tion court. These courts consist of the breakage of old, infected branches very small stubs that remain on main appear to be the major factor causing The conks of E. tinctorium are branches when dead adaxial twigs1, reactivation of these infections and hard, woody, hoof-shaped structures, about 1 mm in diameter (Figs. 1 and 2), penetration of the trunk. The fungus ranging in width from a few centime- are broken off – usually during winter enters the trunk heartwood via the tres to 30 cm. The upper surface is storms. Larger wounds are unsuitable encased branch base, eventually dull black, rough, and cracked; the infection courts. These small wounds combining with infections from neigh- undersurface is greyish, and thickly heal quickly on vigorously growing boring branches to produce a continu- set with hard, course spines (Fig. 5). trees, and are not available as infec- ous column of rot. The interior, or context, is rust-red or tion courts during the following fall brick-red, which is also the color of the spore cast. On suppressed trees, The typical decay develops when advanced stage of decay. The conks however, such wounds may take the fungus attacks the spring wood of are formed on the underside of dead years to heal, and could be infection the annual rings, causing the wood to branch stubs and may be quite abun- courts for many spore casts. separate into flakes, and finally pro- dant (Fig. 3), although not every Infections enter the heartwood of the ducing a yellow or brown stringy mass decayed tree bears conks. main branch through the secondary separated by layers of sound wood. branch traces, and become localized After a variable number of years, dur- The conks of Phellinus pini may in tissues around the pith until condi- ing which the mycelium of the fungus vary in structure from thin shell-shaped tions favour further development. A exists vegetatively, accompanied by to bracket-like and hoof-shaped (Figs. branch may contain 20 or more of extensive decay development, hyphae 4 and 6). They range in width from these semi-quiescent infections, which concentrate at branch stubs or at 2 cm to more than 30 cm. The upper are characterized by large numbers of wound faces and begin forming fruit surface is dull, greyish or brownish bodies. The appearance of fruit bodies black, and rough with concentric fur- at these points is the probable origin of rows parallel to the lighter brown mar- 1 adaxial twigs = small secondary branch- the belief that this fungus infects trees gin. Young and actively growing conks lets growing from the upper surface of through branch stubs and wounds. are zoned (Fig. 6) with a brownish the main branch. tinge and a light-brown margin that is velvety and light gold-brown.

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