Forest Insect

& Disease

Leaflet 150

Revised April 2009

U.S. Department of Agriculture • Forest Service

Decays of Engelmann Spruce and Subalpine Fir

in the Rocky Mountains

James J. Worrall1 and Karen K. Nakasone2

1

Plant pathologist, USDA Forest Service, Forest Health Management, Rocky Mountain Region, Gunnison, Colorado.

2

Botanist, USDA Forest Service, Northern Research Station, Madison, Wisconsin.

Engelmann spruce (Picea engelmannii) 

– Rocky Mountain subalpine fir (Abies 

bifolia) forests occur along the Rocky 

Mountains from central British Columbia 

and western Alberta southward into Arizona and New Mexico. West of the Rockies, from southwestern Yukon Territory to 

northern California, A. bifolia is replaced 

by A. lasiocarpa. Spruce-fir forests occur 

at elevations of 2,000 to 7,000 feet in the 

north and about 8,000 to 12,000 feet in the 

south. The importance of specific decays 

varies considerably over the range of the 

hosts. This leaflet is primarily based on 

studies of Engelmann spruce and Rocky 

Mountain subalpine fir in the southern 

Rocky Mountain ecoregion (northern New 

Mexico to east-central Wyoming), but 

the information is generally applicable 

throughout the Rocky Mountains of the 

United States.

Wood decay plays a major role in carbon 

cycling, influencing release or sequestration of carbon in forests. Decay in living 

trees provides habitat for animals, even 

after the tree dies and falls to the ground, 

by softening or hollowing the inner wood, 

leaving a relatively hard, protective shell. 

Decay also provides nutrition for fungi, 

insects, and animals that feed on them. 

Decay can lead to mechanical failure of 

live trees, creating hazard to people and 

property in developed forest areas. Decay 

diseases, primarily root and butt rots, also 

cause mortality of standing trees. Finally, 
2

decay can substantially decrease the value 

and usable wood volume of trees harvested 

for wood products. Quantifying this last 

impact for timber management has been 

the goal of most studies that have provided 

detailed information about specific decays, 

but the results of those studies may be useful in understanding the role of decays in 

other processes as well.

Engelmann Spruce

Occurrence of Decays

Average defect attributed to decay 

amounts to 20 percent of the gross 

merchantable board-foot volume of 

spruce in Alberta, 12 percent in the Blue 

Mountains of Oregon and Washington, 

and 15 percent in Colorado. Estimates 

of stand defect due to decay in Colorado 

range from 7 to 26 percent. In spruce, 

certain tree abnormalities are reliable 

indicators of stem decay. One means of 

estimating defect in a stand is based on 

average stand age and the average amount 

of cull associated with indicators. Cull 

deductions as a percentage of gross tree 

volume for three groups of indicators are 

available for two age classes (Table 1).

Fungi Involved

Many fungi cause significant decay of 

mature Engelmann spruce, and there are 

wide variations in their frequency and 

volume of decay caused in infected trees 

(Table 2). The fungi differ also in which 

of two decay types they cause. In white 

rot, fungi progressively destroy all wood 

components, leaving a fibrous or stringy 

residue. In brown rot, fungi rapidly 

depolymerize, then gradually consume 

the cellulose and hemicelluloses, leaving 

a dry, brown, cubical or crumbly mass of 

lignin residues. Both types can occur as 

“pocket rots,” in which the decay occurs 

primarily in discrete ellipsoidal zones 

scattered through the wood. Decay results 

in rapid strength loss of wood in the early 

stages, particularly in the case of brown 

rot. Because brown rot results in lignin 

residues that are recalcitrant to further 

decomposition, it may contribute to more 

storage of carbon in the forest floor than 

does white rot.

Location in the Tree

Stem decays (trunk rots), caused by fungi 

that decay the inner stem wood of living 

Table 1. Average cull deductions of Engelmann spruce trees with indicators as a 

percentage of gross tree volume (Hinds & Hawksworth 1966).

Cull deduction (% of 

gross tree volume in 

board-feet)

Indicators and frequency (%) of associated decay1 Under

250 yr

Over 

250 yr

Punk knots or conks of Porodaedalea pini (100) 68 86

Broken top (75) or dead top with adjacent dead rust brooms 

(67) 21 25

Basal wounds (37), dead rust brooms (32) or dead leader in 

living crown (34), frost cracks (32), forks (all types; 23), trees 

joined at base to one another (47), spike top (30) or trunk 

wounds (23)

8 11

1

Number in parentheses is the percentage of occurrences of the indicator that have decay 

associated with them.
3

trees, account for about three-fourths of 

decay losses in Engelmann spruce. The 

two major fungi are Porodaedalea pini and 

Stereum sanguinolentum; but P. pini is the 

most common and causes the largest decay 

columns. The disease is called red ring 

rot because, at least in pines, there is red 

staining in the early stages and it tends to 

develop along the annual rings. Red ring 

rot is associated with all decay indicators, 

including those found in the basal portion 

of a tree. The typical decay is easily 

recognized by its white pockets and by 

its association with punk knots and conks 

(Figure 1), which can be common on trees 

infected for many years. In spruce, it 

tends to occur most frequently in the lower 

stem and may even progress into the roots. 

Porodaedalea pini may actually be a 

complex of species that will be segregated 

as we learn more about them. 

Although red heart, caused by S. 

sanguinolentum, is not as extensive within 

individual trees as P. pini, it occurs nearly 

as frequently and is also associated with 

most decay indicators. The affected wood 

is firm and reddish brown at first, then 

turns light brown, dry, and friable in the 

advanced stage. White mycelial sheets are 

found in the rotted wood in longitudinal 

section. The thin, leathery, annual fruiting 

bodies are seldom found on living trees. 

Length of rot column and cull caused by 

Laurilia sulcata (Figure 2) are greater than 

those of S. sanguinolentum, but this decay 

Table 2. Major decay fungi of mature Engelmann spruce and average 

measurements of associated decay (Hinds & Hawksworth 1966).

Major decay fungi 1

Percentage 

of all decay 

infections 2

Cull in 

infected 

trees (cubic 

feet)

Length 

of decay 

column 

(feet)

Stem decays

Porodaedalea pini 34 21.2 35

Stereum sanguinolentum 29 5.9 21

Laurilia sulcata 6.7 15.8 24

Veluticeps abietina/fimbriata 0.7 13.9 30

Amylostereum chailletii 2.4 4.3 19

Butt rots 

Phellopilus nigrolimitatus 3.1 14.7 25

Pholiota alnicola 4.3 3.7 8

Coniophora puteana 4.5 3.3 9

Onnia tomentosa/leporina 4.0 3.5 10

Vesiculomyces citrinus 2.6 3.3 8

1

Fungi were included if they caused >0.7% of all decay volume in the study. See Tables 4 

and 5 for synonyms and distinguishing features. Less important fungi included: the trunk 

rotters Antrodia serialis, Gloeophyllum sepiarium, Peniophora septentrionalis, Sistotrema 

raduloides, Phellinidium ferrugineofuscum, and Fomitopsis rosea; and the butt rotters 

Armillaria solidipes, Coniophora olivacea, C. arida, Fomitopsis pinicola, Pholiota sp., P. 

squarrosa, Flammulina velutipes, and Oligoporus balsameus. 

2

Percentage of all decay columns from which each fungus was isolated. Total is less than 

100% because less important fungi are not included in the table
4

occurs less frequently. The yellowish 

white pocket rot could be confused with 

that caused by P. pini. 

The relatively uncommon brown trunk rots 

are usually associated with trunk wounds 

and broken tops. When associated with 

trunk wounds, they cause smaller losses 

and are frequently mixed with white 

rots which progress faster. Veluticeps 

abietina/fimbriata causes the largest decay 

columns among brown-rot fungi in stems. 

Additional fungi cause less important stem 

decays in spruce (Table 2, footnote).

Root and butt rots cause less cull than 

stem decays in spruce, but they more 

frequently cause mortality, either by: a) 

killing roots and the root collar; b) causing 

physiological stress that predisposes the 

tree to bark beetle attack; or c) causing 

breakage of the roots or lower stem. For 

example, Armillaria solidipes, which 

causes little cull, may be the most 

important and widespread cause of 

mortality on both species in many sprucefir forests. 

Phellopilus nigrolimitatus is most 

important as a cause of butt rot. It causes 

a white pocket rot with unusually large 

pockets (Figure 3) and decay columns are 

relatively long. Various trunk wounds 

can be infected by P. nigrolimitatus, and 

it can cause decay throughout the tree. 

Two similar species of Onnia cause root 

and butt rot on both spruce and fir: O. 

tomentosa (Figure 4) and O. leporina. 

They cause a white pocket rot preceded by 

a red stain; the disease is sometimes called 

Figure 1. Porodaedalea pini on Engelmann 

spruce: (A) conk below branch stub; (B) punk 

knot with outer surface shaved to reveal golden 

brown fungal mycelium with embedded resin; 

(C) advanced white pocket rot in longitudinal 

section. Punk knots are branch stubs that have 

become colonized and decayed by the fungus 

from inside the tree, and often do not callus 

over as do normal stubs.

A B

C
5

red root rot. Like Pholiota alnicola, which 

causes a common white stringy rot, they 

gain entrance through roots. Although 

they can cause butt rot up to 8 to 10 feet 

up the stem, their main damage is to the 

roots, predisposing trees to windthrow. 

Most basal rot is associated with old basal 

wounds and frost cracks.

With the exception of Coniophora puteana

and Fomitopsis pinicola, the brown rots 

seldom cause extensive basal decay. 

Coniophora puteana is most frequently 

encountered, but F. pinicola is equally 

important in causing cull where it occurs. 

Because F. pinicola usually attacks dead 

sapwood, it is often associated with large, 

old, basal wounds. Many other fungi 

cause less butt rot in spruce (Table 2, 

footnote).

Subalpine Fir

Occurrence of Decays

Although indicators are useful for 

detecting and estimating amount of 

decay in spruce, fir has no consistent 

Figure 2. Laurilia sulcata: (A) frost crack (indicator of decay); (B) decay with diffuse white pocket 

rot; (C) bottom, conks.

Figure 3. Spruce wood 

decayed by Phellopilus 

nigrolimitatus and 

subsequently weathered. 

Note the large, broad 

pockets separated by 

relatively undecayed wood.

A

B

C
6

external indicators of decay. However, 

the amount of decay in fir generally 

increases with age and tree diameter. A 

major part of the spruce-fir forests in the 

Rocky Mountains consists of old, unevenaged stands with large old trees and an 

understory of younger trees in various 

degrees of suppression. The dominant and 

codominant firs in these stands were often 

suppressed for many years by a spruce 

overstory which has since died. 

Losses from decay range from less than 7 

percent (board-foot basis) in trees under 

10 inches DBH to more than 40 percent in 

trees over 20 inches. Decay in trees larger 

than 9.5 inches DBH averages 35 percent 

of board-foot volume. Decay in trees 

younger than 100 years is negligible, but 

rot increases rapidly with increasing age 

to 35 percent in the 150 to 199 year age 

class. The amount of decay is extremely 

variable in older age classes. While 

broken tops and trunk wounds are usually 

indicative of extensive rot, indicators are 

not consistently useful. 

Fungi Involved

Many of the fungi important in subalpine 

fir also occur on spruce, but their relative 

importance varies and some species are 

different (Table 3). 

Location in the Tree

Stem decays account for about twothirds of the overall decay in subalpine 

fir. Stereum sanguinolentum (Figure 5) is 

by far the most important fungus and is 

responsible for over 75 percent of the stem 

decay volume. Called “red heart” because 

of its marked reddish color, the decay can 

be confused in the field with that caused 

Figure 4. Onnia tomentosa: (A) and (B) mushroom-like conks fruiting from buried roots; (C) cross 

section with typical decay pattern associated with old basal wound. 

A

B C
7

by Amylostereum chailletii. Infection 

occurs mainly through wounds and broken 

branches. Multiple trunk infections 

and extensive mixed decay columns are 

common. Fruiting bodies of the fungus 

are seldom found on living trees, more 

frequently fruiting on downed, dead 

material. When found, they are usually 

located on old scars. Fresh fruiting bodies 

of this fungus redden or “bleed” when 

wounded—hence the common name, “the 

bleeding Stereum.”

Porodaedalea pini is the second most 

important fungus, accounting for about 15 

percent of stem decay volume. Incidence 

of the white stringy trunk rot caused by 

A. chailletii is as common as that of P. 

pini, but losses due to A. chailletii are 

only about 5 percent of the total stem 

decay caused by all fungi. Amylostereum 

chailletii is a symbiont of woodwasps 

(Sirex species) and is injected into the 

wood through the ovipositor along with 

the eggs. 

Although many stem-decay fungi 

can invade the sapwood and even kill 

cambium at times, Fomitiporia hartigii

readily does so. Although it causes little 

cull, this trait may result in some early 

mortality in subalpine fir stands.

Table 3.—Important, identified decay fungi of subalpine fir and associated type 

of decay, frequency of isolation from decay columns, and average cull 

(Hinds et al. 1960)

Major decay fungi 1 Decay type

Frequency 

of isolation 

(%) 2

Cull in infected trees 

(cubic feet)

Stem decays

Stereum sanguinolentum White 37 6.9

Porodaedalea pini White pocket 7.3 6.9

Amylostereum chailletii White 6.7 2.5

Veluticeps abietina/fimbriata Brown pocket 2.4 1.9

Fomitiporia hartigii White 1.8 2.5

Butt rots 

Coniophora puteana Brown 7.3 0.8

Armillaria solidipes White 6.7 0.8

Pholiota squarrosa White 6.1 0.9

Coniophora olivacea Brown 4.9 0.8

Onnia tomentosa/leporina White pocket 3.0 1.1

Phellopilus nigrolimitatus White pocket 0.6 6.0

Oligoporus balsameus Brown 0.6 5.8

1

Fungi were included if they contributed at least 1% of the total volume of decay by all 

identified fungi. See Tables 4 and 5 for synonyms and distinguishing features. Less 

important fungi included the butt rotters Vesiculomyces citrinus, Helicobasidium 

corticioides, Pholiota alnicola, Laurilia sulcata and Coniophora arida.

2

Percentage of all identified decay columns from which each fungus was isolated. Total is 

less than 100% because less important fungi are not included in the table. 
8

Table 4. Major stem-decay fungi of living spruce and fir, selected synonyms, and some distinctive features.

Species Decay type Host 1 Fruitbody and decay features

Amylostereum chailletii

≡ Stereum chailletii

white SF Fruiting: Spreading, may have small cap on upper end, up to 1 mm thick, surface smooth to slightly 

bumpy, waxy, becoming brittle, cinnamon to dark brown, sometimes slightly lilac, with a distinct dark brown margin. Decay: stringy. 

Fomitiporia hartigii

≡ Phellinus hartigii= Fomes robustus var. tsugina (some authors)

≡ Poria tsugina

white F Fruiting: Fruits on the underside of branches and branch crotches. Perennial, spreading, often with 

small cap on upper end; cap surface pale yellow-brown; pore surface gray- to purple-brown; tube layers distinctly stratified and old tubes white within. Decay: uniform white rot. 

Laurilia sulcata

≡ Echinodontium (Stereum) sulcatum

white pocket S(F) Fruiting: Spreading, often with cap on upper end; cap up to 1.5 cm wide, light brown to black, tomentose; 

lower surface smooth to bumpy, pinkish-buff to clay, often with cracks. Decay: yellowish pocket rot. 

Phellinidium ferrugineofuscum

≡ Phellinus (Poria) ferrugineofuscus

white S Fruiting: Annual or biennial, woody, flat and spreading, about 1 cm thick, margin light-colored and soft; 

pore surface purplish brown, pores very fine; flesh yellow-brown, tube layer purplish brown. Decay: typically laminated and often with small longitudinal pits and fine, transversely oriented, whitish streaks; sometimes with scattered black flecks. 

Porodaedalea pini

≡ Phellinus (Fomes) pini

white pocket SF Fruiting: Perennial, woody conks formed at dead branches but may appear anywhere as sapwood is killed; 

cap surface reddish-brown to black, rough, with undulating margin; pore surface and interior golden- to reddish-brown. Decay: initial purplish stain along annual rings; later stage with more or less distinct white pockets and sometimes numerous zone lines; decay pockets up to 2x10 mm but may coalesce. Disease name: red ring rot.

Stereum sanguinolentum

≡ Haematostereum sanguinolentum(bleeding Stereum)

white SF Fruiting: Flat but with cap on upper end, cap projecting up to 15 mm, leathery; surface undulating, finely 

hairy with yellow to red-brown concentric zones; underside smooth, light brown to gray, bruising red. Decay: firm and reddish brown at first, then light brown, dry, and friable with white mycelial sheets in the advanced stage. Disease name: red heart (rot).

Veluticeps abietina

≡ Gloeocystidiellum (Stereum, Columnocystis) 

abietinum

brown pocket SF Fruiting: Annual or rarely perennial, spreading, may have cap on upper end, tough, up to 2 mm thick, 

lower surface smooth to roughened, often cracked, pale yellowish to brownish orange to grayish, often with violaceous tinges when fresh. Rare compared to V. fimbriata in the Rocky Mountains. Decay: see V. fimbriata.

Veluticeps fimbriata

≡ Hymenochaete fimbriata= Stereum rugisporum

brown pocket SF Fruiting: Fruits on scars of living trees but more frequently on dead, downed wood. Usually perennial, 

pileate, effused-reflexed or resupinate; cap surface dark brown to nearly black; underside smooth to warted, often cracked, gray to light brown; interior brown; spores larger than in V. abietina. Decay: 

Incipient stage a wet, brown to black stain in streaks or patches; brown rot develops in pockets surrounded by sound wood; pockets later coalesce; often associated with dark stain, a thin cobweb-like layer of mycelium and odor of apples.

1Letters refer to the usual host: S = spruce; F = fir; host in parentheses indicates occasional occurrence.
9

Table 5. Major fungi causing root and butt rot in spruce and fir, selected synonyms, and some distinctive features.

Species Decay type Host 1 Fruitbody and decay features

Armillaria solidipes

= Armillaria ostoyae= Armillaria mellea (in part)(honey mushroom)

white SF Fruiting: Cap 4-10 cm diam, dark brown with a dense layer of fibrils early, becoming tan to yellowish brown and 

smooth; gills cream then darkening to rose or burgundy; stem 3-50 mm diam, widening before forming a pointed base. Decay: Stringy to spongy, often wet, with occasional zone lines; large mycelial fans under bark and usually fine rhizomorphs attached to roots. Disease name: Armillaria root rot.

Coniophora puteana

= C. cerebella

brown SF Fruiting: Flat, spreading, 0.5-2 mm thick, surface yellow to brown and smooth or bumpy with a wide, creamcolored margin. Decay: thin, pale tan cords and wispy mycelium often scattered in decayed wood. Other species

of Coniophora (C. olivacea and C. arida) may be involved, but they have thinner fruitbodies (up to 0.3 mm thick); microscopic examination is required to distinguish the species. 

Oligoporus balsameus

≡ Polyporus balsameus= P. basilaris

brown F(S) Fruiting: Annual, spreading with small cap or more conk-like, about 1 cm thick, whitish becoming pale brown, 

small pores on underside.

Onnia leporina

= Inonotus (Polyporus) circinatus in 

the sense of earlier authors

= Polyporus dualis

white pocket SF Fruiting: Often fruits on butt of recently killed trees; somewhat larger than O. tomentosa; delicate and quickly 

destroyed by insects. Annual, solitary; cap up to 18 cm diam and 11 cm thick, cinnamon to rusty brown, with or without a short lateral stem. Decay: similar to O. tomentosa. Disease name: red root rot. A similar species, O. 

triqueter, occurs on Pinus and other conifers and has a more southern distribution in North America.

Onnia tomentosa

≡ Inonotus (Polyporus) tomentosus

white pocket SF Fruiting: Annual in groups, leathery; cap up to 11 cm diam and 7 mm thick, finely hairy, yellowish-brown, 

usually with a central to lateral stem arising from roots. Decay: preceded by reddish stain; pockets may become sharply separated by apparently sound wood, may develop zone lines in later stage. Disease name: red root rot or tomentosus root disease.

Phellopilus nigrolimitatus

≡ Phellinus (Fomes) nigrolimitatus

white pocket (large pockets)

S Fruiting: Perennial, spreading, may have small cap; cap surface and margin often soft and spongy, blackish to 

yellowish brown; pore surface cinnamon; flesh up to 10 mm thick with black lines. Decay: initially pale brown 

ellipsoidal pockets that become large (up to about 10x25 mm), rectangular and white, separated by firm wood. Disease name: big white pocket rot

Pholiota alnicola white SF Fruiting: Cap up to 6 cm diam, pale yellow-brown, smooth, sometimes slimy; may have fringe of veil remnants; 

stem up to 1 cm thick, with fine fibrils, pale yellow at top then brown below; gills attached; spore print rust-brown. Decay: stringy. 

Pholiota squarrosa (scaly Pholiota) white F(S) Fruiting: Cap and stem with prominent, erect scales; cap 10 cm diam or larger, pale brownish, may have fringe of 

veil remnants; stem up to 1.5 cm thick; gills attached, pale yellowish to gray, rarely green-tinged, becoming dark brown; spore print cinnamon brown; odor mild or garlic-like. Decay: stringy. 

Vesiculomyces citrinus

≡ Gloeocystidiellum citrinum= G. (Corticium) radiosum

white S(F) Fruiting: Flat and spreading, thin, surface smooth, cream to pale brown with a whitish margin with fine cords or 

fibrils. Decay: yellowish, stringy.

1 Letters refer to the usual host: S = spruce; F = fir; host in parentheses indicates occasional occurrence. 
10

Although root and butt rots account 

for only about one-third of the total decay, 

they are important in subalpine fir stands 

because they lead to mortality and windthrow. Root and butt rots probably cause 

much greater volume losses by causing 

trees to fall over than by decay of wood 

in the butt. Among white-rot fungi, the 

soft, spongy rot of Armillaria solidipes, 

the white pocket rot of Onnia tomentosa, 

and the white stringy rots of Pholiota 

alnicola and P. squarrosa cause about 

half of the butt-rot volume losses. Their 

mushroom-like fruiting bodies are found 

on roots and at tree bases, but are not 

common enough to be useful indicators 

of decay. Vesiculomyces citrinus is the 

most common butt-rot fungus in subalpine 

fir (9.8% of all decay isolations), but 

its yellow stringy rot causes negligible 

amounts of cull.

Three species of Coniophora are the 

principal causes of brown cubical butt rot 

(Figure 6). They gain entrance through 

basal wounds; however, rot columns 

seldom extend more than four feet above 

ground. Coniophora puteana is the most 

common and causes the greatest volume 

loss. Additional fungi cause less important 

decays of fir (Table 3, footnote).

Management

Spruce-fir forests are often the most 

productive forest type in the southern and 

middle Rocky Mountains. They are 

Figure 5. Stereum sanguinolentum: Red heart rot (A) and fruiting bodies (B) on balsam fir.

Figure 6. Coniophora puteana: (A) typical 

advanced brown cubical rot leading to 

mechanical failure; (B) effused fruiting body on 

a piece of slash.

A

A

B

B
11

important for timber, water yields, wildlife 

habitat, recreation, and scenic value. 

Where decay in living trees is consistent 

with management objectives, generally 

no action is needed. Where management 

objectives include reducing the amount of 

decay and promoting tree growth, early 

removal of spruce with known indicators 

of decay, and of fir in the older age classes 

will promote healthy, vigorous trees with 

a greater growth potential. Decay losses 

can be minimized by harvesting younger 

trees: 140 to 150 years for spruce, and 

100 to 125 years for fir. Careful marking 

of individual trees to be cut and close 

supervision of logging operations to 

reduce mechanical injuries will minimize 

points of entry for decay fungi. These 

sanitation and prevention methods are 

important because direct control of decays 

is not possible.

References

Aho, P.E. 1971. Decay of Engelmann 

spruce in the Blue Mountains of Oregon 

and Washington. Res. Pap. PSW-116. 

Portland, OR: USDA Forest Service, 

Pacific Northwest Forest and Range Exp. 

Stn. 16 p.

Etheridge, D.E. 1956. Decay in subalpine 

spruce on the Rocky Mountain forest 

reserve in Alberta. Can. J. Bot. 34: 805-

816.

Hinds, T.E., F.G. Hawksworth, and R.W. 

Davidson. 1960. Decay of subalpine fir 

in Colorado. Station Paper No. 51. Fort 

Collins, CO: USDA Forest Service, Rocky 

Mountain Forest and Range Experiment 

Station. 13 p. 

Hinds, T.E. and F.G. Hawksworth. 

1966. Indicators and associated decay of 

Engelmann spruce in Colorado. Res. Pap. 

RM-25, Fort Collins, CO: USDA Forest 

Service, Rocky Mountain Forest and 

Range Experiment Station. 15 p.

Hornibook, E.M. 1950. Estimating defect 

in mature and overmature stands of three 

Rocky Mountain conifers. J. For. 48: 408-

417.

Worrall, J.J., K.F. Sullivan, T.C. 

Harrington, and J.P. Steimel. 2004. 

Incidence, host relations, and population 

structure of Armillaria ostoyae in 

Colorado campgrounds. Forest Ecology 

and Management 192: 191-206.

Revised April 2009. Original:

Hinds, T.E. 1977. Heart rots of 

Engelmann spruce and subalpine fir in the 

central Rocky Mountains. USDA Forest 

Service. Forest Insect & Disease Leaflet 

150. 8 pp.

Acknowledgments

Manfred Binder and Brenda Callan helped 

sort out the identity and nomenclature of 

some of the fungi. Katharine Sheehan 

updated the original publication for an 

online version in 2002. Helpful reviews 

were provided by Gregg DeNitto, Mary 

Lou Fairweather, Greg Filip, Paul Hennon, 

and Bill Jacobi. Illustration credits: Fig. 

2A and 4C by T.E. Hinds, others by J.J. 

Worrall. 
12

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published by:

USDA Forest Service

Pacific Northwest Region (R6)

Portland, Oregon

FS-R6-RO-FIDL#150/006-2009