Forest Insect & Disease Leaflet 52 Revised April 2010 U.S. Department of Agriculture • Forest Service Decays of White, Grand, and Red Firs Katy M. Mallams1, Kristen L. Chadwick2, and Peter A. Angwin3 White fir (Abies concolor), grand fir (Abies grandis), and red fir (California and Shasta red fir, Abies magnifica and Abies magnifica var. shastensis) are ecologically and economically important conifer species in moist forests in many areas of western North America. White fir is the most widespread of the three species. Two varieties of white fir are recognized: Rocky Mountain white fir (Abies concolor var. concolor) in southeastern Idaho through central Colorado to Figure 1. Fallen grand fir exposing rust-red northern Mexico, and California white stringy rot and hollow caused by Indian paint fir (Abies concolor var. lowiana) in fungus. western Oregon and northwestern California, central Oregon, and the Many fungi invade and decompose Sierra Nevada. Grand fir inhabits wood in tree stems (Figure 1). stream bottoms, valleys, and lower- Some species are restricted to either elevation mountain slopes in the heartwood or sapwood, while some Pacific Northwest, and northern Idaho species decay both heartwood and and Montana west of the Continental sapwood. True heart-rot fungi infect Divide. Red fir dominates large areas only living trees and are confined of cool, moist forest above 5000 feet to the heartwood. They do not in the Sierra Nevada of California. need natural openings or wounds Shasta red fir occurs in similar to penetrate the bark, but can infect environments in the northwestern through living, undamaged branches Coast Ranges of California and the and stems. True heart-rot fungi are southern Cascade Mountains in not primary colonizers of dead wood, California and Oregon. although some species continue to Plant Pathologists, USDA Forest Service, Forest Health Protection - Pacific Northwest Region (1Central Point, OR; 2Sandy, OR) and Pacific Southwest Region ( 3Redding, CA) develop in the wood for a short time understory vegetation. Decayed wood after trees die. Many decay fungi added to the forest floor contributes require openings in the bark for to the physical structure, nutrient entry. True firs do not have a primary composition, and moisture-holding resin system, so exposed wood is capacity of the soil. It provides food highly susceptible to fungal infection. and micro-habitats for a myriad of Openings can result from wounds decomposer organisms. caused by fire, weather, animals, humans, or from natural causes such as branch stubs, open knots, dwarf mistletoe cankers, and dead branches. Wounds can also exacerbate dormant infections. Decay fungi that commonly occur only in the base and roots of trees are known as butt rots. Some of these fungi also cause root diseases. Still other fungi primarily decay wood in dead trees or in dead portions of living trees. Some species Figure 2. Bushy-tailed woodrat in a hollow continue to decay logs and lumber in grand fir. service. Some also decay wood and roots on the forest floor and in the soil. Hollows in trees and logs resulting from the action of certain decay fungi Vegetation Dynamics and are critical components of habitat for many wildlife species. Woodpeckers, Ecological Role black bears, American martens, Vaux’s In general, decay is most prevalent swifts, bats, flying squirrels, and in older, larger trees, due at least bushy-tailed woodrats are among the in part to accumulation of wounds species using hollow trees for dens, and an increase in the proportion of roosts, nests, and foraging sites (Figure heartwood over time. Decay fungi that 2). Fungi that decay heartwood in become abundant in old forests may living trees are very important in the be important as disturbance agents formation of hollow trees and logs. that initiate and sustain small canopy Such decay is compartmentalized gaps. This is especially true in areas within the cylinder of heartwood where large-scale disturbances such as that was present when the tree was windstorms or fires are infrequent. In wounded. Hollows occur in the these situations, breakage associated advanced stages of decay when the with decay may be one of the main cylinder of heartwood is weakened to means by which large trees are the point that it collapses inside the brought down, creating small gaps. tree. White, grand, and red firs are In these gaps regeneration of shade- important contributors to hollow-tree tolerant tree species can occur, and habitat caused by decay fungi. Hollow shrub and herbaceous vegetation can chambers in large-diameter trees are develop. Structural complexity of the most useful to wildlife. Because it forest is increased by the presence of takes many decades for large trees down wood, tree regeneration, and with advanced decay to develop, 2 large hollow trees are found primarily rot or brown rot. Distinguishing be- in late-successional and old-growth tween white and brown rot can aid in stands. identifying the causal fungus and the effects of decay on wood structure and Impact and Identification use. White rots are caused by fungi that produce enzymes that decay both Fungi cause significant amounts of the cellulose and lignin in wood. The decay in white, grand, and red firs, re- decayed material may form pockets sulting in loss of merchantable timber, and is often pulpy, fibrous, laminated, reduction in wood quality, windthrow, or stringy. It is usually white, tan, and breakage. Decay is generally more or brownish. In advanced stages the extensive in white fir and grand fir than wood may be completely destroyed, in red fir. Trees with decay in recre- leaving a hollow tree or log. Pulp ation areas and other developed sites yields from wood containing white can be extremely dangerous as they are rot are reduced, but pulp quality is not more prone to failure than sound trees. greatly affected. Most of the common Decay fungi play very important roles decay fungi affecting white, grand, in the ecosystem by creating structural and red firs are white rots. Brown rots diversity, returning nutrients to the soil, destroy cellulose and leave the lignin, and providing crucial wildlife habitat. Young, uninjured fir trees are normally resulting in a column filled with a dry, free from decay, but wounded fir trees brown, crumbly mass. The decayed and fir trees over 140 years old often material is fragile and often disinte- have significant decay. grates into small cubes (Figure 3). Wood colonized by brown-rot fungi, Decay can be difficult to identify in the even in the earliest visible stages of early stages. Incipient decay caused by decay, is greatly reduced in strength some fungi may cause color changes and of little use in service. Since the in wood, but other changes are more cellulose fibers are destroyed, wood cryptic. Fruiting bodies (conks) are affected by brown rot has little value usually good indicators of decay, but for pulp. frequently are not present. Conks vary from fleshy mushrooms to woody shelf- like structures. They can be annual or perennial. Some decay fungi continue to produce conks on down trees or stored logs. Table 1 summarizes the physical characteristics of the common decay fungi affecting white, grand, and red firs. Armillaria species and Hetero- basidion occidentale, fungi that cause root disease in true firs as well as butt Figure 3. Advanced brown cubical decay rot, are covered in Forest Insect and caused by velvet-top fungus. Disease Leaflet (FIDL) 78, Armillaria Root Disease, and FIDL 172, Annosus In the absence of fruiting bodies or Root Disease of Western Conifers. visible decay in true firs, symptoms Decay fungi also differ according to such as fire scars, wounds, dead the type of rot they cause: either white tops, broken or bayonet tops, dwarf 3 Table 1. Characteristics of common decay fungi affecting white, grand, and red firs NAME OF ROT CAUSAL FUNGUS PART OF TREE FIELD ID DECAY DECAY FRUITING BODY Current name DECAYED TYPE (Proposed name) Common name Rust-Red Stringy Rot Echinodontium tinctorium Heartwood, middle to Conks, rusty knots, Rusty red, soft and stringy, separates at annual Perennial conk, often under tree limbs; top black, upper stem older trees White rings rough, cracked; bottom toothed, gray; interior bright Indian paint fungus brick-red Red Ring Rot, or Phellinus pini Heartwood, Conks, punk knots, Pocket rot, spindle shaped pockets, firm wood Perennial conk; top dark brown to black, White Speck (Porodaedalea pini) throughout stem swollen knots White in between concentrically furrowed, scalloped margin; bottom brown, irregular pores Ring scale fungus Red Ring Rot Canker Phellinus cancriformans Heartwood, lower to Conks, sunken cankers Pocket rot, spindle shaped pockets, firm wood Perennial conk; top dark brown to black; bottom (Porodaedalea cancriformans) middle stem White in between brown, irregular pores, occur in dense clusters in sunken cankers Butterfly conk Schweinitzii Root and Phaeolus schweinitzii Heartwood, roots Conks at tree base or Light to dark brown cubes with resinous white Annual but persistent conk, round with sunken center, Butt Rot, or Brown and butt on ground near base, Brown fungal tissue in cracks short stalk; top velvety, yellow to reddish-brown Cubical Butt Rot Velvet top or Cow-pie fungus swollen butts when new, brittle, dark brown when old; bottom green to brown pores 4 Mottled Rot Pholiota adiposa and Pholiota Heartwood, lower to Mushrooms, hollow Honey colored with brown streaks, wood Gilled mushroom, appears in fall in groups from limonella