2009 Forest Health Protection and State Forestry Organizations 11.4 WEB July 2010 Management Guide for Laminated Root Rot Susan K. Hagle USDA Forest Service Phellinus sulphurascens (Pilat) [formerly Phellinus weirii (Murr.) Gilb. Douglas-fir form] Topics Introduction 1 Nomenclature 2 Ecology 2 Hosts: Primarily Two distinct biological species of this fungus Impact 6 Douglas-fir occur in western North America; and grand fir one primarily on Douglas-fir and true firs Mortality rates 7 (discussed here), All conifers may be and the other, on western redcedar (see Site factors 8 infected Chapter 13.5; Cedar Laminated Butt Rot). Assessing severity 9 Management 10 considerations A serious disease in northern Idaho and western Montana. Regeneration 11 systems This fungus kills trees in expected to have better survival on expanding patches in forests. These infested sites. Thinning 12 patches can be from a few trees to Laminated root rot is estimated Prescribed fire 14 many acres in size. Trees of all ages to infest at least 739,000 acres in Fertilization 14 are killed as their roots are Idaho and Montana. Mortality destroyed by the fungus. Many also centers occupy over 15,000 acres of Biological control 14 die through wind-throw following federal, state and private forestland Stump removal 15 decay of support roots. The fungus on and near the Idaho Panhandle, Chemical control 15 spreads underground through tree Clearwater, Lolo, Kootenai and root systems and survives for many northwestern Bitterroot National Other reading 16 decades in dead roots and stumps. Forests in Idaho and Montana. It is Field Guide Laminated root rot should be rarely seen south of the Salmon Management Guide considered a “disease of the site”. River in Idaho. Douglas-fir and Index That is, established mycelia of this grand fir forests on warm, moist site fungus are essentially permanent, so types are most damaged. the best course is to minimize losses Key Points by managing tree species that can be Manage for pines, larch, and cedar. Precommercial thinning may OVERVIEW OF improve growth and LAMINATED ROOT ROT MANAGEMENT survival of pines and larch 1. Favor resistant species. Especially pines and western larch. Thinning for bark 2. Thin early and avoid partial harvests. Precommercially thin beetle control may favoring root disease resistant species. result in increased 3. Avoid commercial thinning that will leave susceptible mortality if crop trees. Mortality rates of susceptible leave-trees are likely laminated root rot to remain high, or increase following thinning. is present. Page 2 Back to menu Laminated Root Rot 11.4 Nomenclature of Phellinus sulphurascens The name Phellinus Banik and others (1993) found sulphurascens was officially Douglas-fir isolates to be distinct Laminated root assigned to the Douglas-fir/ true fir from the cedar form in ELISA rot in Western form of Phellinus weirii by Larsen (seriological) tests. They also North America and others in 1994. But at least as demonstrated that the Douglas-fir by far back as 1954 the two distinct form is serologically related to Thies and forms of Phellinus weirii, one Siberian isolates of P. Sturrock, 1995 found primarily on Douglas-fir and sulphurascens. It is more closely the other in western redcedar, were related to the Asian P. This useful recognized (Buckland 1954). The sulphurascens than to cedar form publication provides name change will reduce the isolates of P. weirii. They excellent confusion that has resulted from concluded that the Douglas-fir form photographs and using the same name for two is probably conspecific with P. summarizes the dissimilar fungus species, with sulphurascens. Based on results relevant information different hosts, and vastly different from monocaryon matings, Larsen for the identification and management disease management methods. and others (1994) also concluded of this disease. Larsen and Lombard initially that the correct name for the proposed separation of the cedar Douglas-fir form is Phellinus form from the Douglas-fir form sulphurascens Pilat. They also into two distinct species in 1989. described the hyphal system of They found significant differences both Douglas-fir and cedar forms in cultural characteristics, length of as being monomitic. A monomitic setal hyphae, basidiospore hyphal system is the principle germinating characteristics and criterion that separates the genus host specificity. Cedar and Douglas Inonotus from Phellinus. Therefore Phellinus -fir forms are distinctly intersterile the correct generic placement of sulphurascens groups in culture (Angwin and both P. weirii and P. sulphurascens Hansen 1988). Despite finding is Inonotus. Pathogen of nearly complete genetic isolation of Beginning in 2007 Sturrock and conifers in the Douglas-fir and cedar forms associates adopted the use of northern Angwin (1989) recommended Phellinus sulphurascens to refer to hemisphere. considering them to be intersterility the Douglas-fir form (Sturrock and Annual groups rather than distinct species. others 2007, Lim and others 2008). sporophore Intersterility observed in cultures This is the binomial I will use in was confirmed by Bae and others the present document. Douglas-fir and (1994) in naturally-occurring grand fir are the populations. most important hosts. Ecology of laminated root rot in forest ecosystems Does not mate with Phellinus Life Cycle summer or fall. The simple, single weirii. Phellinus sulphurascens begins -celled spores are produced en life, like most fungi, as a spore. masse within pores of the Monomitic The mostly annual, crust-like sporophore. They are wind or hyphal system sporophores typically form on the water-dispersed; rarely landing on suggests genus name Inonotus. moist underside of downed logs. a substrate that is suitable for their The sporophore matures in late survival. 11.4 Back to menu Laminated Root Rot Page 3 Moisture is required for Oregon was estimated by Dickman germination. The mycelium that is and Cook (1989) to be at least 460 subsequently produced must years old. Laminated root establish on suitable wood and Saprophytic and parasitic rot is commonly repel competitors or perish. Most existence found in the perish. Phellinus sulphurascens has same trees and been reported to live even the same Persistent and expanding saprophytically in the roots and roots with other mycelial clones lower stem of fallen trees or in root diseases New myclia from germinating individual cut stumps for as long such as spores probably join with, and as 50 years (Hansen 1976, 1979a). Armillaria, exchange nuclei (conjugate) with Hyphae penetrate the wood, other mycelia to become Annosus, and causing a ‘white rot” type of decay Tomentosus root heterokaryotic. These mycelia may in which both cellulose and lignin diseases. have ecological advantages over are degraded. Dead wood utilized those grown from a single spore by P. sulphurascens also may be Angwin and Hansen (1993). Even from tree and woody-shrub species so, life is precarious for the new that were resistant when they are heterokaryote and few will live to alive. establish as a clone. The mycelium spreads from There is little genetic variation woody substrates to the roots of within established clones, live trees through direct root indicating that they start from contact with infected wood. Mycelium— single basidiospores and do not Infection intensity may increase Plural: Mycelia mate with or combine genetic The vegetative (non- with each generation (Tkacz and fruiting) part of a fungus material with new spores or Hansen 1982). In northern Rocky consisting of a mass of colonies (Bae and others 1994). Mountain forests, Douglas-fir and branching, thread-like Vegetative incompatability among grand fir are particularly hyphae. clones effectively prevents susceptible to infection. Once Monomitic— initiation of new infections in established on a root of a live tree, a fungus that has only areas occupied by established the fungus invades and kills the one kind of hyphae, clones (Bae and others 1994). This cambium of the root and the generative hyphae. means that established clones decays the dead root tissues. The effectively block invasion by new Heterokaryotic— mycelium may eventually travel cells having two distinct clones of P. sulphurascens. It up the root to colonize the root nuclei. Generally appears that once a clone is collar, and girdle the tree. produced by conjugation established on a site, it may of two different mycelia. survive for centuries by utilizing Aggregated and dispersed Homokaryotic— both living hosts and dead infections in stands cells having one substrates. Generation after Laminated root rot occurs in nucleus. Homokaryotic mycelia generally result generation of trees serve as hosts complex patterns in forest stands, for the same clone on a site. from germination of with many or most of the infected sexually produced Because clones within trees bearing no above-ground spores, such as those infection centers are genetically symptoms of infection. Distinct from sporophores. distinct from one another, the infection centers are easily approximate extent and age of detected as aggregations of dead clones associated with some and diseased trees. Much of the infection centers have been infection in a stand will be within determined. For example, a clone and adjacent to these infection in a mountain hemlock forest in centers. Page 4 Back to menu Laminated Root Rot 11.4 Infected trees also are found The most significant effect of dispersed throughout stands in fire may be the opportunity it locations having no apparent provides for less-susceptible tree relationship to infection centers species to establish. Pines and larch (Thies and Nelson 1997, Thies and are sometimes able to survive fires Sturrock 1995). Thies and Nelson that kill Douglas-fir and grand fir, (1997) reported that infection rates and to take advantage of fire- at considerable distance from produced openings to regenerate. infection centers were as high as Historically, fires probably played they were at the edges of infection an important role in reducing EXPANSION RATES centers, near confirmed inoculum laminated root rot by favoring sources.