United States

Department of

Agriculture

Forest Service

Alaska

Region

State and

Private

Forestry

Forest 

Health 

Protection

2009
2

Cover photos clockwise from top:

 Spruce bark beetle damage (inset spruce bark beetle)

 Chicken of the woods conks

 Hemlock fluting and wood decay

 Wood wasp
3

Edward Holsten, U.S. Forest Service Entomologist (retired)

Paul Hennon, U.S. Forest Service Pathologist

Lori Trummer, U.S. Forest Service Pathologist

James Kruse, U.S. Forest Service Entomologist

Mark Schultz, U.S. Forest Service Entomologist

John Lundquist, U.S. Forest Service Entomologist

Insects and

Diseases of

Alaskan Forests

Publication Number R10–TP–140
4

Acknowledgments

The authors thank Tom Laurent, Richard Werner, and John Hard, retired U.S. 

Forest Service Pathologist and Entomologists, respectively, who were instrumental in 

developing previous editions of this handbook. We thank Courtney Danley, biological 

technician, U.S. Forest Service Juneau, for her efforts in obtaining new insect photos. 

We also appreciate the technical assistance of Ken Zogas, biological technician, 

U.S. Forest Service Anchorage, and Roger Burnside, Entomologist, Division of 

Forestry, State of Alaska, as well as the enthusiasm and professionalism of the Alaska 

Cooperative Extension IPM Technicians. This handbook would not have been possible 

without the hard work and dedication of David Allen, graphic designer, Public Affairs 

Office, Chugach National Forest, Anchorage, Alaska.

Photographs and other illustrations were obtained, as credited in the Appendix, from 

individuals and from the files of the State of Alaska, Canadian Forestry Service, the 

U.S. Forest Service, and other sources as cited. 

Preface

The U.S. Forest Service publication, Identification of Destructive Alaska Forest 

Insects (91), dealt mainly with the damaging forest insects of Southeastern Alaska. 

Insects and Diseases of Alaskan Forests (137, 138) included disease agents and were 

a logical statewide expansion of Hard’s (1967) earlier insect work. Since then, our 

information on forest insects and diseases of Alaska has increased tremendously (279). 

In April 2001, a substantially revised and expanded Insects and Diseases of Alaskan 

Forests was printed (141). The popularity of the handbook and the need for minor 

revisions has resulted in this 2009 reprint. 

This handbook is divided into insect and disease sections, each with its own 

illustrations, and host index. Literature cited, glossary, and a general index follow at the 

end of the book. 

Handbook Organization

Not every insect or disease in Alaska is covered in this handbook. Some are omitted 

because of limited distribution or minor importance, and others are awaiting more 

comprehensive surveys and information on their economic or ecological importance. 

Few chemical suppression measures are included for the organisms covered in 

this manual because many new control measures are quickly outdated or discarded 

with new advances, recognition of environmental hazards, or lack of benefit/cost 

effectiveness. Please refer to the nearest office of the Alaska Cooperative Extension 

Service or State and Private Forestry, U.S. Forest Service for information concerning 

specific control measures.

A discussion of the forests of Alaska and invasive pests follows the introduction. 

A short description of insects and diseases affecting general parts of a plant follows 

next and directs the reader to the appropriate insect or disease section. For each insect 

or disease, a summary of its hosts, distribution, identification, damage, remarks, and 

references are provided. A specific index of insect or disease by host plant follows each 

respective section. The handbook concludes with a glossary, bibliography, appendix for 

submitting insects or diseases for identification, photography and illustration credits, 

and finally a general index. 
5

Table of Contents

Introduction........................................................................................................10

Forests of Alaska................................................................................................11

Alaska Land Cover Map...................................................................................13

Invasive Pests......................................................................................................14

Guide to the Forest Pests..................................................................................17

Forest Defoliators...............................................................................................21

Western Black‐Headed Budworm..............................................................24

Spruce Budworm.........................................................................................26

Large Aspen Tortrix.....................................................................................28

Leaf Rollers..................................................................................................30

Western Hemlock Looper...........................................................................32

Spear‐Marked Black Moth..........................................................................34

Green‐Striped Forest Looper......................................................................36

Saddle‐Backed Looper................................................................................37

Mourning Cloak Butterfly...........................................................................38

Hawkmoth....................................................................................................39

Rusty Tussock Moth....................................................................................40

Spotted Tussock Moth.................................................................................41

Leaf Blotch Miner.......................................................................................42

Willow Leaf Miner......................................................................................43

Birch Leaf Miners........................................................................................45

Hemlock Sawfly ..........................................................................................46

Larch Sawfly................................................................................................48

Striped Alder Sawfly ...................................................................................50

Alder Woolly Sawfly...................................................................................51

Leaf Beetles..................................................................................................52

Bud and Shoot Insects.......................................................................................53

Spruce Bud Midge.......................................................................................54

Spruce and Larch Budmoth.........................................................................55

Sap‐Sucking Insects and Mites........................................................................56

Spruce Aphid................................................................................................57
6

Giant Conifer Aphids..................................................................................59

Spruce Gall Aphids......................................................................................60

Woolly Adelgids..........................................................................................62

Spruce Bud Scale.........................................................................................64

Birch Aphid..................................................................................................65

Hardwood Gall Insects................................................................................66

Spittlebug .....................................................................................................68

Spider Mites.................................................................................................69

Eriophyid Mites...........................................................................................70

Bark Beetles........................................................................................................71

Spruce Beetle ...............................................................................................73

Eastern Larch Beetle ...................................................................................77

Engravers......................................................................................................78

Hemlock Hylesinus.....................................................................................81

Cedar Bark Beetle........................................................................................82

Four‐Eyed Bark Beetle................................................................................83

Dryocoetes...................................................................................................84

Willow Bark Beetle .....................................................................................85

Wood Borers.......................................................................................................86

Round‐Headed Borers or Long‐Horned Beetles....................................... 87

White-Spotted Sawyer ................................................................................88

Xylotrechus...................................................................................................89

Other Alaska Cerambycidae .......................................................................90

Metallic or Flat‐Headed Wood Borers.......................................................91

Flat‐Headed Fir Borer.................................................................................92

Bronze Birch Borer .....................................................................................93

Other Alaska Buprestidae............................................................................94

Ambrosia Beetles.........................................................................................95

Ambrosia Beetles Trypodendron.................................................................96

Clearwing Birch Borer................................................................................97

Ghost Moths.................................................................................................99

Wood Wasps...............................................................................................101

Horntails.....................................................................................................102

Cone and Seed Insects.....................................................................................103
7

Spruce Coneworm.....................................................................................104

Spruce Seed Moth .....................................................................................105

Spruce Cone‐Axis and Gall Midges.........................................................106

Spruce Cone Maggot.................................................................................107

Yellow-cedar Gall Midge..........................................................................108

Insect Pests of Wood Products.......................................................................109

Carpenter Ants...........................................................................................110

Carpenter Bees...........................................................................................112

Powder Post Beetles..................................................................................113

Parts of an Insect.............................................................................................115

Index to Insects by Host Plants.....................................................................116

Diseases..............................................................................................................123

Foliar Diseases..................................................................................................125

Spruce Needle Rust...................................................................................125

Hemlock Needle Rust ...............................................................................128

Hardwood Leaf Rust .................................................................................129

Cedar Leaf Blight ......................................................................................130

Spruce Needle Blight.................................................................................131

Shoot Diseases..................................................................................................134

Sirococcus Shoot Blight............................................................................134

Yellow-cedar Shoot Blight........................................................................136

Shepherd’s Crook ......................................................................................137

Stem and Branch Diseases.............................................................................138

Hemlock Dwarf Mistletoe ........................................................................138

Spruce Broom Rust ...................................................................................142

Western Gall Rust......................................................................................144

Cankers of Spruce and Hemlock..............................................................146

Cankers of Hardwoods..............................................................................148

Rough Bark of Alder.................................................................................151

Root Diseases....................................................................................................152

Annosus Root Disease...............................................................................152

Armillaria Root Disease............................................................................155

Tomentosus Root Rot.................................................................................157
8

Wood Decays and Stains.................................................................................159

Pini Conk or Red Ring Rot.......................................................................160

Pinicola Conk or Red Belt Fungus...........................................................163

Chicken of the Woods or Sulfur Fungus..................................................165

Velvet Top Fungus.....................................................................................167

Artist’s Conk..............................................................................................169

Lacquer Conk or Varnish Conk ................................................................170

Indian Paint Fungus...................................................................................171

Quinine Conk.............................................................................................172

Hartig’s Conk.............................................................................................173

Borealis Conk ............................................................................................174

Purple Conk ...............................................................................................175

Yellow Cap Fungus or Scaly Cap Mushroom.........................................176

Coniophora Brown Rot.............................................................................177

Redcedar White Ring Rot.........................................................................179

Yellow Ring Rot ........................................................................................180

Cedar Brown Cubical Pocket Rot.............................................................181

Oyster Mushroom......................................................................................182

Coral Fungus..............................................................................................183

Tinder Conk ...............................................................................................184

False Tinder Conk......................................................................................185

Cinder Conk...............................................................................................187

Birch Conk.................................................................................................188

Rainbow Conk...........................................................................................189

Blue Stain...................................................................................................190

Black Stain of Yellow-cedar Heartwood..................................................191

Noninfectious Disorders.................................................................................192

Yellow-cedar Decline ................................................................................193

Hemlock Fluting........................................................................................195

Burls...........................................................................................................197

Animal Damage.........................................................................................199

Other Abiotic Disorders............................................................................201

Index to Pathogens by Host Plants...............................................................206

Glossary.............................................................................................................212
9

Literature Cited...............................................................................................217

Appendix...........................................................................................................236

Submitting Insects and Diseases for Identification............................236

Photography and Illustration Credits..................................................238

General Index...................................................................................................240
10

Introduction

 The sciences of forest entomology and pathology or the study of forest insects 

and diseases are relatively new to Alaska. Even though insect and disease surveys 

have been undertaken for over eight decades, some pests have only recently been 

identified. Alaska’s forests are important in terms of wood production, wildlife 

habitat, and recreation. Forest resource management cannot be practical in Alaska 

until forests are adequately protected from insect, disease, and fire losses. Forest 

managers should be able to determine which pests are detrimental and which are 

not to forest resource management. Likewise, private land managers and hom‐

eowners should learn to identify pests that invade and attack their trees and shrubs.

 We must not underestimate the effects of forest pests whose damage can occur 

during every stage of forest growth. Nationally, insects kill twice as much timber as 

do disease-causing organisms, and seven times the amount killed by fire. But, on 

an annual basis, the loss of potential growth and decay caused by disease exceeds 

the more spectacular damage caused by fire and insects. There was the risk of 

forest insect and disease mortality on 23.5 million hectares of forested land in the 

United States in 2006 (249). The annual volume and monetary loss attributed to 

insects and diseases are unknown in Alaska.

 Some documented insect outbreaks in Alaska include 4 million hectares of 

Sitka spruce–western hemlock forests of southeast Alaska defoliated by larvae of 

the black-headed budworm in 1953, 1.6 million hectares of western hemlock in 

southeast Alaska defoliated by hemlock sawfly larvae in 1953, 200,000 hectares 

of white spruce infested by the spruce beetle in the Copper River drainage in 1959 

and one million hectares in 1975 defoliated by larvae of the spear-marked black 

moth in interior Alaska. Spruce beetles infested more than 1.3 million hectares of 

Alaska spruce forests from 1990–99.

 Unlike some of the spectacular insect outbreaks, tree diseases are often chronic 

and pervasive in the forests of Alaska. They may often go unnoticed, yet diseases 

can cause fundamental ecosystem change and huge economic loss to timber 

resources. Heart rot fungi cause substantial defect; nearly 1

/

3

 of the gross volume of 

live trees in old-growth coastal forests is decayed. Dwarf mistletoe causes growth 

loss and tree mortality but also contributes to wildlife habitat in hemlock forests. 

Over 200,000 hectares of yellow-cedar forests have high concentrations of dead 

trees caused by yellow-cedar decline. Root diseases and heart rot fungi cause 

substantial growth loss and mortality of spruce and hardwoods.

 While insect and disease agents can cause substantial impacts, not all are 

negative. Ecologically, these agents alter forest structure and composition, and 

are essential to nutrient cycling, habitat diversity, forest succession, and carbon 

sequestration. With such a range of potential impacts, wise decisions for insects 

and diseases can be made when they are based on the best information.
11

Forests of Alaska

The forests of Alaska stretch thousands of kilometers and encompass 51.4 

million hectares. The three major forested zones in the state are the coastal rain 

forests of Southeast Alaska, transitional forests of South-central, and the boreal 

forests of the Interior. 

The temperate rain forests of Southeast Alaska are dominated by western 

hemlock and Sitka spruce, but Alaska yellow-cedar, western redcedar, shore 

pine and mountain hemlock are also important components. Wind is the major 

agent of large-scale disturbance in Southeast Alaska causing uprooting and 

bole breakage. The most susceptible forest type is mature spruce-hemlock 

on productive, wind-exposed sites. Bole breakage is common in decadent 

old growth forests. Uprooting also occurs, resulting in soil churning, which 

expedites nutrient cycling and increases soil permeability. Even-aged forests 

develop following large-scale catastrophic wind events. Old-growth forest 

structure develops in storm-protected landscapes. In these areas, small gapforming events dominate. 

South-central Alaska is a transition zone between the coastal marine climate of 

Southeast and the continental climate of the Interior. Forest vegetation is com‐

prised mainly of white spruce, black spruce, paper birch, trembling aspen, and 

cottonwood. In the most southern areas of this zone, western hemlock, moun‐

tain hemlock, and Sitka spruce grow on favorable sites. In locations where 

Sitka spruce and white spruce overlap, the Lutz spruce hybrid is common. Fire 

is a factor in the forested landscapes of South-central, but these fires are mostly 

2.471 acres equal one hectare; 5 board feet equal one cubic foot; and 35.32 cubic feet equal one 

cubic meter.

Figure 1. Old-growth 

spruce hemlock forests of 

Southeast Alaska.
12

the result of human activity as lightning strikes are uncommon in this region. 

Major disturbances affecting forests in the past century have been human 

activity and spruce beetle caused mortality. Earthquakes, volcanic eruptions, 

and flooding following storm events have also left significant signatures on the 

landscape.

The boreal forests of Interior Alaska are comprised of white spruce, black 

spruce, eastern larch, paper birch, trembling aspen and cottonwood. Distribu‐

tion of forested areas across the landscape is determined by fire history, slope, 

aspect, and the presence or absence of permafrost. Fire is the major distur‐

bance agent; lightning strikes are very common north of the Alaska Range. 

Tree species in the Interior are susceptible to damage by fire, and all are fireadapted, to some degree. 

Figure 3. The boreal forest of Interior Alaska is a mosaic 

of spruce, aspen, and birch.

Figure 2. Mixed hardwood and spruce forests are 

prevalent in South-central Alaska.
13Map courtesy of Alaska Department of Natural Resources, Division of Forestry

Figure 4. Alaska land cover type map.
14

Invasive Pests

Invasive pests (introduced non-indigenous plants, animals, and microbes) are 

among the most serious threats to biological diversity in the forest ecosystems 

of the United States. Likewise, the movement of native insects and pathogens 

from one area of the United States to another where they do not naturally 

occur is also problematic. It has been estimated that 10.8% of the plants and 

3.5% of the invertebrates in the United States are established exotics (38). It 

has also been estimated that, of the $97 billion in losses from invasive pests 

during 1906–1991, $92 billion was from insects (179). Recent estimates 

suggest potential losses to the U.S. from forest insects and forest pathogens 

exceeds $4.2 billion annually (187).

Introduced insects and pathogens can create enormous ecological damage for 

several reasons. First, native vegetation is not equipped with genetic resistance 

to these introduced organisms because they did not co-evolve together. Native 

trees have had time to develop levels of resistance to organisms that they have 

been exposed to and this limits the virulence of attack. Lacking any genetic 

resistance, native trees can be overwhelmed by these newly introduced organ‐

isms. Second, some of the introduced insects and pathogens are mortality 

agents to trees. As tree killers, they are disturbance agents and can severely 

modify the forested landscape. Third, insects and pathogens are highly mobile 

and are not limited to transportation corridors. They can essentially march 

across host types and invade some of our most pristine natural areas. Alaska 

has few tree species, and we cannot afford to lose any one of them. 

Because North America contains many plant genera common to Eurasia and 

east-central Asia, we can expect, and have seen, cross-regional exchanges of 

plant-feeding organisms. Likewise, given increasing global markets, techno‐

logical advances in transportation, and mobility of humans, rates of introduc‐

tions will continue to increase. For example, in a ten year period, the U.S. 

Agricultural Plant Health Inspection Service (APHIS) intercepted insects on 

various wood products on nearly 5,900 occasions. Since 1985, there has been 

a steady increase in the number of 

insect interceptions on wood prod‐

ucts from China at U.S. ports. The 

volume of commodities imported 

annually from China with associated 

wood crating, dunnage, and pallets 

is estimated to be in the millions of 

shipments.

It has been estimated that of 70 major 

pests of U.S. forests, 19 (27%) were Figure 5. European gypsy moth larva.
15

introduced. Some of the more important include: chestnut blight; Dutch elm 

disease; white pine blister rust; gypsy moth; and recently, sudden oak death, 

the Asian long-horned beetle and the emerald ash borer. The latter two insects 

probably traveled to the United States inside solid wood packing material 

from China or Japan. These beetles have been intercepted at ports, found in 

warehouses, and found in various cities throughout in the United States. The 

pathogens came primarily on living plants.

In Alaska few invasive species have been introduced and established into 

our forested ecosystems. The movement of insects, diseases, and plants into 

Alaska from the Lower 48 is more of a problem. For example, ornamental 

mountain ash (Sorbus spp.) is established in Southeast Alaska; black knot 

(Apiosporina morbosum), a disease of ornamental trees, such as chokecherry 

and Mayday, was introduced on imported plant material. The western tent 

caterpillar (Malacosoma californicum) 

is repeatedly intercepted in Anchorage 

on nursery stock used as out-plantings. 

Adult European gypsy moths (Lymantria 

dispar) have been caught in pheromone 

traps on several occasions in Alaska. It 

is believed, however, that this potentially 

devastating forest pest is not established. 

Likewise, the Sitka spruce weevil 

(Pissodes strobi), a serious insect pest 

of young spruce throughout the Pacific 

Northwest and British Columbia has been introduced into the Anchorage Bowl 

on at least three occasions. It appears that this weevil can complete its life 

cycle in South-central Alaska. Whether this insect is established is not known.

The amber-marked birch leaf miner (Profenusa thomsoni) is one exotic 

invasive that we were unable to prevent from establishing in the state. This leaf 

mining sawfly originated from Europe, entered eastern North America around 

1900, spread westward, and eventually reached Alaska probably through 

Haines in the mid-1990s. From 1996, when it was first discovered in Anchor‐

age, to now, the amber-marked birch leaf miner has spread across the entire 

Matanuska-Susitna Valley, Fairbanks, Haines, Skagway, and a large part of 

the Kenai Peninsula. This insect pest will likely continue to spread throughout 

Alaska’s South-central and Interior birch forests.

White pine blister rust was found in Ketchikan in 2004 on an ornamental white 

pine tree. It may have been introduced with the planting of the pine, or more 

likely was brought in when infected ornamental gooseberry was planted in 

the same yard. Fortunately, the pathogen is not capable of spreading beyond 

ornamental plants because it requires the white pine host and these trees are 

Figure 6. Black knot.
16

not native in Alaska. It does, however, illustrate the pathways of introduction 

of insects and pathogens by the trade of ornamental plants. 

We can expect increased introductions of non-native species as well as 

accidental introductions of native species of the U.S. from one part of the 

country to another due to expansion of world trade. Another concern is the 

movement of insects, plants, and microbes from the continental U.S. into 

Alaska’s forested ecosystems in light of climate change and increased com‐

merce. Weather records from the Kenai Peninsula in South-central Alaska, 

have indicated that annual temperatures have increased by 3–5° F in the last 

forty years. Such a warming trend could increase the probability that insects 

accidentally introduced into Alaska can become 

established. Most introduced insects, plants and 

microbes arrive without corresponding parasites 

and predators. Likewise, trees and shrubs native 

to Alaska have not evolved defensive systems to 

minimize damage from these introduced pests. 

Consequently, if established, introduced pests 

can explode in population numbers and poten‐

tially bring about widespread ecological change 

to our forested ecosystems.

It is inevitable that we are going to see more 

and more introduced pests coming into Alaska. If we are not prepared to 

expend efforts to safeguard our ecosystems, Alaska will be poorer in terms of 

resources and biological diversity. USDA APHIS, State of Alaska Division of 

Agriculture and Forestry, Alaska Cooperative Extension (ACE), and the U.S. 

Forest Service, Forest Health Protection (FHP) already have small programs 

to detect these introductions. Inadequate funding and support, however, have 

limited the scope and implementation of these programs. Alaska residents, 

resource professionals and land managers need to “keep a sharp eye out” for 

potential introduced pests, learn to distinguish them from our native species, 

and quickly contact ACE, APHIS, or the Division of Agriculture, their local 

Cooperative Extension office if any are found. If introduced pests are quickly 

identified, the probability of successful eradication is increased. 

Forest management can help ensure fewer deleterious effects if insects or 

pathogens are introduced. Managing forests for species diversity is insurance 

against complete destruction of the forest. Insects and pathogens are typically 

host-specific and will only attack a narrow group of related hosts. Thus, by 

creating forests with a mixed tree species composition, some forest trees will 

remain even in the worst case scenario of an introduced insect or pathogen. 

References: 38, 179, 187, 207, 254

Figure 7. Adult Asian longhorned beetle.
17

Guide to the Forest Pests

Damage confined to Leaves, Buds, and Shoots:

Defoliating Insects. Affected needles with a reddish cast, insects or 

signs of their feeding present. Needles and buds are partially or totally 

consumed. Caterpillar or beetle‐like insects usually present on foliage in 

early spring or summer. Leaves chewed, mined, skeletonized or webbed. 

Viewed from a distance, affected trees have a brownish or yellowish 

cast................................................................................................................21

Bud and Shoot Insects. Malformed, enlarged buds on young-growth 

spruce; commonly encountered on terminal buds of branches. In some 

cases, multiple leaders result.....................................................................53

Sap-Sucking Insects and Mites. Curled or discolored foliage. Whole 

insects or their cast skins small (1–2 mm long); cottony tufts, galls, and 

honeydew sometimes present................................................................56

Galls caused by Insects. Abnormal, misshapen, swollen or spherical 

growth on needles or leaves, or in the bark or twigs. Insect larvae or frass 

present inside the galls...........................................................................66, 70

Shoot Diseases. Shoots are stunted, malformed or killed. Fruiting bodies may 

be present...............................................................................................134–137

Foliage Diseases (including needles). Foliage yellowing, brown, or 

spotted (insects largely absent); orange, yellow, or black pustules or other 

fungal fruiting bodies present. Some fruiting bodies are very small......125

Needle Rusts, leaf rusts. Fruiting bodies on foliage are orange, 

sometimes yellow or brown and dry; large branch brooms may or may 

not be present................................................................125, 128, 129, 142

Abiotic Disorders. Foliage or buds yellowing, browning, or dying after 

exposure to early or late frosts, air pollutants, drought, flood damage, 

or the yellow-cedar decline; entire crown may show signs of stress or 

die; cause of the damage may not be apparent but signs of insect or 

disease agents are generally absent..........................................................201

Damage primarily on Cones and Seeds:

Galls caused by Insects. Abnormal, misshapen, swollen, or spherical 

growth in the cones or seeds. Insect larvae or frass present inside the 

galls..................................................................................................66, 106, 108

Moths and Midges. External evidence of insect activity is difficult to 

see. Galleries are small in diameter and are commonly found within the 

cone axis, cone scales, and seeds. Boring dust is reddish to light brown 

and fine................................................................................................104–108
18

Figure 8. Parts of trees commonly 

affected by forest pests.

Figure 9. Specific parts of a tree 

affected by forest pests.
19

Damage confined to Branches and Stems:

Witches’ Brooms. On hemlock; large or small brooms or swellings 

commonly on branches, less commonly on stems; needles retained on 

live brooms; small yellow or red leafless plant may be present on affected 

tissue (Hemlock Dwarf Mistletoe)...........................................................138

On spruce; large or small brooms, current year’s needles may appear 

orange, yellowish, or pale green; fruiting bodies of fungi may be present 

on needles; broom needles are shed in fall and broom appears dead until 

spring (Spruce Broom Rust).....................................................................142

Galls Caused By Diseases. Round, woody galls on branches or stem of 

pine. Insects generally not present in the galls. (Gall Rust)....................144

Cankers or Animal Damage. Large patches of dead bark on live trees, 

sometimes exposing wood; often on main tree bole; fruiting bodies of 

fungi may be present....................................................................146, 148, 199

Wood Decay and Stain. Wood is hollow, pitted, spongy, breaks into 

crumbly pieces, or is stained in color. Fruiting bodies of fungi may 

be present. Older trees, or those physically injured in the past usually 

affected.......................................................................................................159

Bark Beetles. Insect activity characterized by boring dust and resin on 

bark and around base of trees. Galleries commonly found under bark 

and usually less than 0.6 cm in width, at times into the sapwood, rarely 

penetrating the wood. Boring dust reddish to light brown and fine.........71

Wood Borers. Larval borings are usually granular. Galleries penetrate 

into the sapwood and, at times, into heartwood of weakened or recently 

killed trees or logs.......................................................................................86 

Abiotic Disorders. Deeply incised vertical grooves or ridges on live 

hemlock trees (Hemlock Fluting); globe-shaped, large, woody growths 

or swellings on branches or stems of spruce and various hardwoods 

(Burls)....................................................................................................195, 197

Damage confined to Roots and Lower Stem 

Root Diseases. Entire crown shows signs of stress (yellowing foliage, 

needle or leaf loss, stress cone crop) or dies as a unit; wood or root tissues 

are killed or decayed and may have fungal structures; fruiting bodies of 

fungi may be present at base of tree or on the ground nearby; trees may 

die standing, snap at the lower bole, or uproot with a characteristic small 

root ball and extensive decay in the broken stubs of primary roots; fallen 

trees in disease centers tend to lie in a random pattern......................152–158
20

Windthrow. Individual or patches of trees exhibit stem breakage or 

uprooting with a large soil plate and primary roots attached; fallen trees 

typically lie parallel to one another in a similar direction as the wind 

storm; signs of disease agents may be present.........................................204

Abiotic Disorders. Dead and dying trees found in small or large groups, 

not usually solitary trees. Entire crown of tree shows signs of stress and 

dies as a unit as in root diseases. Fruiting bodies of pathogenic fungi 

usually absent, but weakly pathogenic and saprophytic fungi (those 

restricted to dead tissues) and secondary insects may be present. Death 

of coarse and fine roots precedes crown symptoms. Necrotic lesions 

may spread from dead roots vertically up the main bole (Yellow-cedar 

decline).......................................................................................................193

Damage confined to Wood Products on Land.

Carpenter Ants and Bees. Galleries in soft or moist wood of 

buildings.................................................................................................110, 112

Powder Post Beetles. Small holes in finished wood products...............113

Decays and Stains. Wood is hollow, pitted, spongy, breaks into crumbly 

pieces, or is stained in color. Fruiting bodies of fungi may be present..159
21

Forest Defoliators

Defoliator insects eat the leaves or needles of forest trees and shrubs. Defolia‐

tors are found throughout Alaska and on all tree types. Bark beetles are often 

considered the more significant disturbance agents in boreal Alaska (due to 

the high potential for causing tree mortality). Even so, defoliators can have a 

significant affect on both coniferous and deciduous trees, and can cause tree 

mortality with several seasons of defoliation. In maritime ecosystems where 

conifers dominate, such as Prince William Sound and Southeast Alaska, defo‐

liators tend to be the more significant agents of change. If complete defoliation 

of a conifer occurs before midsummer, the trees will not have formed buds for 

the following year and the tree could be killed. 

In a defoliator outbreak where insect populations are at epidemic levels, vast 

acreages can be affected. During an outbreak, nearly every tree can be affected 

to varying degrees. This defoliation often results in a variety of biological and 

ecological impacts, but there are socioeconomic impacts as well. Some of the 

impacts associated with a defoliator infestation include, but are not limited to: 

Impacts on wildlife habitat. Wildlife may be positively or negatively affected 

by defoliator outbreaks. Larvae are a necessary food source to fledgling chicks, 

but bird habitat may be negatively affected by the decrease in cover. Con‐

versely, predatory birds may benefit from the cover change. The added light to 

the forest floor will result in an increased ground cover of herbaceous plants, 

benefiting browse animals such as deer. Spruce budworm defoliation can kill 

the tops of a spruce tree and eliminate its ability to produce cones. Thus squir‐

rels, white-winged crossbills, etc. and their predators may be greatly reduced 

in these forested areas.

Impacts on aquatic systems. Aquatic systems may also be positively or 

negatively affected. Nutrient cycling is accelerated as foliage and insect waste 

enters the aquatic system. Larvae may drop into streams and can serve as a 

food source for fish. In addition, the loss of overstory cover can increase sun‐

light exposure to the stream, affecting the aquatic environment.

Economic concerns. Heavy defoliation will decrease the growth rate of trees 

resulting in the delayed harvesting of merchantable trees. In addition to growth 

loss, repeated and or heavy defoliation events can cause top kill and, in some 

cases, tree death.

Aesthetics and recreation. The visual impact of a defoliated stand in the 

midst of an outbreak can be quite alarming and often will lose attractiveness 

for recreation. Large numbers of larvae can be a nuisance in picnic grounds 

and campgrounds. Dead tops and dead trees pose a hazard in recreational 

areas. However, the effect is often short term, and the following year, scenic 

quality usually returns to “normal.” 

Forest Defoliators
22

Figure 10. Defoliators: A. Sawfly larva (Hymenoptera); B. Looper (Lepidoptera: 

Geometridae), C. Budworm (Lepidoptera: Tortricidae).

Defoliator outbreaks tend to be cyclic and closely tied to climatic conditions. 

The synchronization of larval emergence and tree bud break is closely related 

to population increases. The better the synchronization of insect and host 

throughout larval development, the more likely that an epidemic will occur. 

The effects of defoliation, however, can be viewed positively. The opening 

of the forest canopy allows greater light penetration to the ground level. This 

increased light results in new seedlings and increased ground cover of herba‐

ceous plants and more rapid soil nutrient recycling. These changes can result 

in greater forest and browse production through increased plant growth. 

All species of trees are not equally susceptible to damage from defoliation 

(85). Hardwood species are more resilient. These species can usually with‐

stand several years of defoliation with little tree mortality because hardwoods 

store large food supplies and may refoliate in the same year. Conifers are more 

likely to die after complete and repeated defoliation. 

In this text, defoliators are grouped by their feeding habits:

• Leaf Chewers, that consume all leaf tissues (succulent tissues, veins, and 

midrib). They are the most damaging defoliators.

Forest Defoliators
23

• Leaf Miners, that feed upon the succulent tissues while tunneling between 

the upper and the lower epidermal layers of the leaf. 

• Skeletonizers, that eat all the leaf tissue except for the veins and midrib.

• Sap-Suckers, that feed on needle sap. 

The most important tree-defoliating pests are sawflies (Hymenoptera suborder 

Symphyta: Tenthredinidae, Diprionidae), leaf beetles (Coleoptera: Chryso‐

melidae), caterpillars (Lepidoptera: Tortricidae, Geometridae, Nymphalidae, 

Sphingidae, Lymantriidae, Arctiidae, Noctuidae, Gracillariidae, and Lyonetidae), 

and aphids (Homoptera: Aphididae).

Forest Defoliators
24

Western Black-headed Budworm

Lepidoptera: Tortricidae

Acleris gloverana (Walsingham)

Hosts: Western hemlock, mountain hemlock, Sitka, Lutz and white spruce.

Distribution: Throughout maritime forests of Southeast Alaska, South-central, 

and Southwest Alaska. It is also found throughout British Columbia and south 

to California.

Identification: The larval head is black during the first four larval stages and 

tan-orange in the last stage. During early development stages, budworm larvae 

are cream-colored. Their body color changes to green as they develop. Mature 

larvae are 17 mm long. Pupae are green or brown and are approximately 7 

mm long. Adults are small brownish gray moths with variable brown, black, 

orange, and white markings. Eggs are yellow, flat, and are laid singly on the 

underside of host needles. 

Damage: The western black-headed budworm is one of the most destructive 

forest insects in coastal Southeast Alaska. An outbreak in the late 1940s to 

mid-1950s affected host trees on almost every forested hectare in Southeast 

Alaska. Localized outbreaks have occurred sporadically since then. Larval 

feeding strips host foliage and can bring about a reduction in growth, top kill, 

and at times, tree mortality.

Remarks: Western black-headed budworms overwinter in the egg stage on 

host foliage. The eggs hatch in June and feeding begins. Budworm and hem‐

Figure 11. Hemlock defoliation, Calder Bay, Southeast Alaska.

Forest Defoliators
25

lock life cycles are closely synchronized; young larvae feed within the protec‐

tion of unopened hemlock buds. As the shoots begin to elongate the larvae 

feed on the new needles. Larvae usually confine their feeding to new growth. 

In large concentrations, larger larvae will feed on older needles, thus bringing 

about complete defoliation. 

Each mature larva ties live and cut needles together and pupates within this 

shelter. Adults emerge in late August through October. Mated females lay 

flat, yellow eggs singly on the underside of host needles. Mean fecundity of a 

population is 80 eggs per female (205).

Budworm populations are characterized by sporadic spectacular increases in 

number followed two to three years later by equally rapid declines. Only 16 

species of budworm parasites and predators have been identified in Alaska 

compared to 48 species in coastal British Columbia (234). Adverse weather 

may be an important controlling factor for Southeast Alaska budworm popula‐

tions. 

To date, no suppression actions have been taken as budworm populations 

disappear as rapidly as they appear. However, the budworm is a definite threat 

to young stands.

References: 3, 9, 73, 91, 94, 153, 203–205, 234, 259

Figure 12. Western black-headed 

budworm larva, A. gloverana.

Figure 13. Western 

black-headed budworm 

adult, A. gloverana.

Forest Defoliators
26

Spruce Budworm

Lepidoptera: Tortricidae

Choristoneura fumiferana (Clemens), C. orae Freeman and C. 

biennis Freeman

Hosts: Sitka, white, and Lutz spruce.

Distribution: Throughout Alaska. Populations of C. fumiferana are found in 

vicinity of Fairbanks and east; C. orae populations are found from Fairbanks 

south into South-central Alaska. These species may hybridize in Lutz spruce 

stands. The species can only be told apart reliably by mtDNA sequences.

Identification: Mature larvae are approximately 3.2 cm long, with brownish 

head, green to orange body, and prominent ivory-colored spots. Adults are pre‐

dominantly gray-brown moths and have a wingspread of 22 to 28 mm. Eggs 

Figure 14. Spruce budworm larva, 

Choristoneura spp.

Figure 15. Adult spruce budworm.

Forest Defoliators
27

are light green and are laid in shingle-like masses on the underside of needles. 

Damage: Larvae destroy buds, host foliage, cones and seeds. Reduction in 

radial growth is evident during severe infestations and top-kill is common. 

Remarks: Similar to A. gloverana in biology. However, the spruce budworm 

over-winters as larvae in silken shelters beneath bark scales and old male flow‐

ers. Larvae enter and feed upon buds in May or June, then attack new foliage. 

An extensive outbreak of C. fumiferana occurred in the early 1990s and lasted 

for about five years. More than 50,000 hectares of white spruce were heav‐

ily defoliated along the Tanana and Yukon Rivers as far west as Ruby. Spruce 

coneworm (Dioryctria reniculelloides) populations simultaneously increased 

resulting in heavy defoliation as well as a widespread reduction in cone and 

seed production. Heavy top-kill is associated with outbreaks, resulting in 

reduction of cone-feeding vertebrates and eventual predisposition to bark 

beetle attack.

References: 73, 93

Forest Defoliators
28

Large Aspen Tortrix

Lepidoptera: Tortricidae

Choristoneura conflictana (Walker)

Host: Aspen.

Distribution: Principally in Interior and in South-central Alaska. This insect 

was first recorded from Alaska in 1966 when it reached outbreak conditions on 

more than 2,023 hectares of aspen near Fairbanks. 

Identification: Larvae are gray-green to black with dark head capsules. The 

forewings of the moths are gray with brownish markings. Green eggs are 

deposited in masses.

Figure 16. Large aspen tortrix 

larva, C. conflictana. Note the 

parasitic fly maggot feeding on 

the larva.

Figure 17. Large aspen tortrix 

adult, C. conflictana.

Forest Defoliators
29

Damage: Larvae skeletonize both upper and lower leaf surfaces. 

Remarks: Eggs are deposited on upper leaf surfaces. First instars are active 

until mid-August, and feed gregariously within rolled leaves where they 

skeletonize both the upper and lower leaf surfaces. The larvae then migrate 

to protected areas, spin a shelter, molt to second instar, and overwinter. The 

overwintered larvae become active during the first two weeks of the following 

May and mine into buds. Complete destruction of leaves can occur before bud 

burst. Larger larvae feed in the open. Pupae are formed within rolled leaves of 

the host plant and understory vegetation. The adults are active from late June 

to July. 

As with many defoliators, large aspen tortrix populations rapidly increase 

to epidemic levels. Aspen stands are usually completely denuded for two 

consecutive years. Populations then subside. Large aspen tortrix populations 

require a pure diet of aspen to maintain outbreak levels. Complete stripping 

of aspen foliage before the last instar will reduce population numbers due to 

widespread starvation. Tortrix larvae cannot survive the two or more weeks 

required by aspen to refoliate and thus are forced to feed on plants that do not 

provide proper nutrition for larval development and egg production. 

Weather, starvation, and parasitism are most effective in reducing C. conflictana populations. 

References: 11, 13, 14, 17

Forest Defoliators
30

Leaf Rollers

Lepidoptera: Tortricidae

Epinotia solandriana (L.)

Hosts: Typically Alaska birch and alder; can be found on willow, aspen, and 

black cottonwood. 

Distribution: Recurring problem in South-central, Interior, and Southeast 

Alaska.

Identification: First instar larvae are pale-green. Later instars are a blue-gray 

turning to a pale yellow-cream prior to pupation. Pupae are brownish and are 

approximately 8.0 mm long and 2.5 mm wide. Adult moths vary in forewing 

pattern. The most common pattern (approximately 65 percent) is one of 

subdued grays and browns. Wingspan ranges from 1.5 to 2.0 cm. Eggs are 

approximately 0.96 mm long by 0.71 mm wide, oval in shape and a reddishorange.

Figure 18. Mature birch leaf

roller larva.

Figure 19. Birch leaf roller adult.

Forest Defoliators
31

Figure 20. Birch leaf roller damage, Epinotia solandriana.

Damage: Larvae roll leaves that are skeletonized, curl, brown and drop prema‐

turely. Branch dieback and tree mortality sometimes occurs. 

Remarks: Birch leaf rollers have one generation per year in Alaska, and 

overwinter in the egg stage. Larvae hatch in mid-May to early June and begin 

feeding in buds and later in leaf rolls. Last instars vacate leaf rolls and pupate 

in fragile cocoons between the humus layer and the mineral soil. The adults 

emerge from late July through August. After mating, eggs are laid singly on 

previous year’s twigs, usually on the roughened bud stalks.

Birch leaf rollers are the most common leaf rollers on birch. However, other 

genera, including Clepsis, are commonly associated with birch. Drastic and 

repeated defoliation by these insects results in minor growth reduction and 

occasional branch dieback. Large populations of leaf rollers are reduced by 

adverse weather, parasites, predators, and disease. 

References: 142, 169

Forest Defoliators
32

Western Hemlock Looper

Lepidoptera: Geometridae

Lambdina fiscellaria lugubrosa (Hulst)

Hosts: Sitka spruce (preferred host in Alaska), western hemlock, western 

redcedar, and Alaska yellow-cedar. 

Distribution: The only recorded looper outbreak in Alaska occurred from 

1965 to 1966 about 30 km southeast of Wrangell where approximately 200 

hectares of Sitka spruce were heavily defoliated. 

Identification: Mature larvae are 2.8–3.2 cm long and brownish gray with 

various patterns of lines, stripes, and spots giving them a mottled appearance. 

Pupae are approximately 1.3 cm long, mottled greenish brown. Adults are light 

buff with a wingspan of 3–5 cm. Forewings are marked with two wavy lines 

Figure 21. Western hemlock looper larva.

Figure 22. Western hemlock looper adult.

Forest Defoliators
33

and hind wings with one wavy line. Eggs are minute (about 0.6 mm long) and 

grayish green.

Damage: This insect tends to kill many needles because it is an inefficient 

feeder. Severe defoliation causes reduction in tree growth, and at times, tree 

mortality. 

Remarks: Eggs are deposited on the upper bole and branches and understory 

shrubbery where they overwinter. The larvae are loopers, and hatch in late 

spring and early summer and begin feeding on young needles in the crown. 

Later in the larval development old foliage is eaten. Often only a few bites are 

taken out of each needle. 

Mature larvae pupate in the forest litter or in bark crevices. The pupal period 

is approximately two weeks. Adults emerge in late fall to mate and lay eggs. 

There is one generation per year. 

Outbreaks build up rapidly and generally last for three years. A single com‐

plete defoliation at midsummer can cause tree mortality. Some trees can with‐

stand 50 percent defoliation and even 75 percent defoliation is not fatal unless 

other insects such as bark beetles subsequently attack the trees. 

The most important natural controls are a viral disease and heavy rains during 

fall moth dispersal. Eight species of parasites have been reared from looper 

pupae.

References: 3, 41, 91, 93, 153, 235, 236

Forest Defoliators
34

Spear-Marked Black Moth

Lepidoptera: Geometridae

Rheumaptera hastata (L.)

Hosts: Alaska paper and Kenai birch, alder, and willow. 

Distribution: South-central and Interior Alaska. From 1974–75, epidemic 

populations of the spear-marked black moth infested 1.1 million hectares of 

paper birch in Interior Alaska. 

Identification: Newly hatched looper larvae are 2.5 mm long and have gray‐

ish-green bodies and light-brown heads. Mature larvae are about l6 mm long 

and have black bodies with a whitish pink spot on the side of each body seg‐

ment and dark brown heads. Pupae are shiny brown and about 11.0 mm long 

and 3.5 mm wide.

Adults are black moths with white markings on the wings, approximately 

Figure 23. Spear-marked black moth 

larva.

Figure 24. Spear-marked black moth 

adult.

Forest Defoliators
35

Figure 25. Birch 

defoliation caused by 

spear-marked black moth.

9–11.5 mm long with a wingspread of 26–30.5 mm. Similar species also 

found in Alaska: Rheumaptera subhastata.

Damage: Webbed leaves are heavily skeletonized. Severe defoliation by 

early August results in a temporary reduction in radial and terminal growth. 

Branch dieback is quite common. Repeated severe defoliation can result in tree 

mortality. 

Remarks: There is one generation per year. Clusters of eggs are deposited 

from mid-June to early July on upper leaf surfaces or in folds of leaves that 

have been rolled by leaf rollers. Emerging larvae feed gregariously on upper 

leaf surfaces between two leaves that have been webbed together. Damage 

is often inconspicuous due to the larval behavior of webbing leaves together. 

Third and fourth instars web one or two leaves together and feed singly. Defo‐

liation becomes readily apparent by early August. 

Last instars drop to the forest floor, pupate and overwinter in forest litter. Adult 

moths emerge from early June to July. Following emergence, large groups of 

adults seek moisture. 

Parasites, predators, disease, and weather are responsible for population 

declines. During the 1975–76 spear-marked black moth outbreak, parasitism 

accounted for a 16 and 30 percent reduction of R. hastata larval and 55 and 90 

percent reduction in pupal populations, respectively. Disease contributed to a 

95 percent reduction in third and fourth instar populations in 1975. 

References: 91, 260, 262, 263

Forest Defoliators
36

Green-Striped Forest Looper

Lepidoptera: Geometridae

Melanolophia imitata (Walker)

Hosts: Western hemlock (preferred host), western redcedar and Alaska 

yellow- cedar.

Distribution: Southeast Alaska.

Identification: Mature green-striped forest looper larvae are deep apple green 

with white and yellow-green lateral stripes. The head is pale green. Adults are 

mottled gray-brown moths with a wingspan of 25–40 mm.

Damage: Needle chewing can cause top kill and rarely tree mortality.

Remarks: Not well known in Alaska. However, in British Columbia, this 

looper overwinters as a pupa in the duff layer. Adults emerge, mate and 

oviposit from mid-May to mid-June. Eggs are deposited on tree branches 

and trunks. Larvae feed on all foliage, but one year old foliage is preferred. 

Feeding is heaviest in the upper crown. Mature larvae drop to the ground and 

pupate in late summer.

References: 73, 93, 130

Figure 26. Green-striped 

forest looper larva.

Figure 27. Green-striped forest looper adult.

Forest Defoliators
37

Saddle-Backed Looper

Lepidoptera: Geometridae

Ectropis crepuscularia (Denis & Schiffermuller)

Hosts: Western hemlock (preferred host), western redcedar and Alaska 

yellow- cedar.

Distribution: Southeast Alaska.

Identification: Mature larvae are loopers with brownish and reddish diamondshaped marks on the back. The mottled, light-gray moth has a wingspan of 30 

mm.

Damage: Needle chewing can cause top kill and rarely tree mortality. This 

looper is commonly found in association with the hemlock sawfly. In 1969, 

this looper caused moderate to severe defoliation, and some mortality of west‐

ern hemlock on 100 hectares near Ketchikan.

Remarks: Biology is not well known in Alaska. However, in British Colum‐

bia, the moths emerge in May and lay eggs. Recently emerged larvae feed first 

on the ground cover and understory, later moving up into trees. Mature larvae 

drop to the ground in August where they pupate and overwinter.

References: 73, 93, 172

Figure 28. Saddle-backed looper larva.

Forest Defoliators
38

Mourning Cloak Butterfly

Lepidoptera: Nymphalidae

Nymphalis antiopa (L.)

Hosts: Willows (preferred host), poplars, and other hardwoods

Distribution: Throughout Alaska but more prevalent in the South-central and 

Interior portions of the state.

Identification: Mature larvae are 2.0 to 3.0 cm long and are blackish with 

red and white dots and are conspicuously spinney. Pupae are 2.0 to 3.0 cm 

long and are attached to twigs by silk threads and hang downward. Adults 

are brownish-black butterflies with yellow wing edges and a row of blue dots 

lining the inner edge of the yellow bands. Wingspread is 50 to 70 mm. A simi‐

lar species, the Compton’s tortoiseshell (Nymphalis vaualbum), has become 

common in the Interior. Larvae are brown and spined, adults are similar in size 

to N. antiopa but brown with a conspicuous white square marking on the hind 

wing.

Damage: Severe defoliation can result in a temporary reduction in radial and 

terminal growth. Shrub and tree mortality is rare.

Remarks: In northern latitudes, there is one generation a year. Adult but‐

terflies emerge in late summer and overwinter. In early spring, orange-brown 

eggs are deposited in masses on limbs and twigs. Larvae feed in groups from 

the leaf margin inwards. Leaves may be silk-spun together. Pupae are formed 

in June or July. Control is seldom necessary.

References: 5, 73

Figure 29. Mourning cloak larva. Figure 30. Mourning cloak adult.

Forest Defoliators
39

Hawkmoth

Lepidoptera: Sphingidae

Hyles galii (Rottenburg)

Hosts: Fireweed and other perennials

Distribution: Throughout Alaska

Identification: Larvae, often called hornworms, are quite large, (8 cm long), 

green or black in color with a red head and pale spots on the body. A con‐

spicuous horn or spine-like process occurs on the dorsal surface of the eighth 

abdominal segment. The adult hawkmoth or sphinx moth is a good flyer with 

a pale band down the middle of the forewing and a red band on the hind wing. 

Wing span is approximately 6 cm. Pupae are brown, 2–3 cm long.

Damage: Complete defoliation of fireweed and other perennials can occur.

Remarks: These moths are strong flyers with a very rapid wing beat; most are 

active at dusk. Moths feed like hummingbirds, hovering in front of a flower 

and extending their proboscis into it. Adults are seen from May to August. 

Larvae feed on fireweed until late fall then over winter as a pupa in the leaf 

litter. This hawkmoth is also known as the bedstraw hawkmoth as it feeds 

upon bedstraw (Galium spp.) across boreal and montane North America from 

the east coast to Colorado and California, north to Canada and Alaska.

References: 28, 247

Figure 31. Hawkmoth larva. Figure 32. Hawkmoth adult.

Forest Defoliators
40

Rusty Tussock Moth

Lepidoptera: Lymantriidae

Orgyia antigua (L.)

Hosts: Conifers, hardwoods and shrubs.

Distribution: Throughout South-central, Southwest, and Interior Alaska.

Identification: The dark hairy caterpillar is about 2.8 cm long with four 

yellow “tussocks” of hair along the back, two tufts of dark hair near the head 

and one more at the rear. The adult male is an erratic-flying rusty-brown moth 

with a white dot and a light brown band on each forewing. The female is sed‐

entary, wingless, and about 12 mm long.

Damage: The caterpillars consume the leaves of trees and shrubs. When larval 

populations are high, large areas can be defoliated.

Remarks: The caterpillars hatch from overwintering eggs in the spring and 

feed on whatever suitable host is available. Pupation occurs in August with the 

adults emerging several weeks later. Eggs are laid on host material prior to the 

winter months. There is one generation per year.

References: 73, 207

Figure 33. Rusty tussock moth larva.

Figure 34. Rusty tussock moth adult.

Forest Defoliators
41

Spotted Tussock Moth 

Lepidoptera: Arctiidae

Lophocampa maculata (Harris)

Hosts: Blueberry and Sitka alder.

Distribution: Southeast Alaska.

Identification: Larvae are thickly covered with tufts of black and bright 

yellow to whitish hairs, and have a row of short tufts (some think these look 

like tussocks) down the middle of the dorsum. Full-grown larvae (also known 

as woolly bears) are about 30-mm long and dull black above. Pupae are within 

hairy cocoons. The adult moth is pale yellow with long brown-spotted fore‐

wings and has a wingspread of 37 to 50 mm.

Damage: Moderate to heavy defoliation of alder and blueberry is sporadic. 

Larvae are solitary feeders except during outbreaks.

Remarks: This moth is in the tiger moth family not the tussock moth family: 

Lymantriidae. The tussock hairs of Lymantriidae moths can be irritating to 

the skin, but not so for Arctiidae moth hairs. Moderate to heavy defoliation of 

alder and blueberry was observed during the summers of 1997 and 1998 from 

Wrangell Island south to Ketchikan. There is probably one generation with the 

pupa overwintering in a cocoon in the leaf litter. Adults emerge the following 

spring, mate, and deposit eggs. The larval stages found during the summer 

months.

References: 245, 247

Figure 35. Spotted tussock moth 

caterpillar.

Figure 36. Spotted tussock moth adult.

Forest Defoliators
42

Leaf Blotch Miner

Lepidoptera: Gracillariidae, Lyonetidae

Phyllocnistis populiella (Chambers), Phyllonorycter nipigon 

(Freeman), Lyonetia alniella (Chambers), and Lyonetia saliciella 

Busck

Hosts: Aspen, balsam poplar, black cottonwood, birch, and alder. 

Distribution: South-central, Southeast, and Interior Alaska.

Identification: Larvae are minute (approximately 5 mm long), white, very 

flat, and are found within meandering mines. Adults are minute moths with 

lanceolate wings. 

Damage: Meandering mines produced in epidermal layers on underside of 

leaves. Such mining reduces the photosynthetic area of the affected leaves. 

Heavy repeated attacks could reduce tree growth and cause branch dieback.

Remarks: Winter is spent as adults under bark scales of conifers and hard‐

wood trees. Adults emerge early June and deposit eggs singly on the leaf edge 

then slightly fold the leaf edge to form a protective covering for the egg until 

larval emergence. The newly hatched larvae bore and feed between epidermal 

leaf tissues. After the fourth instar, pupation occurs within the leaf mines. 

Adult emergence occurs prior to or sometimes after the leaves drop in late 

August and early September.

References: 11, 28, 65, 73, 153

Figure 37. Larval galleries of the aspen 

leaf miner, Phyllocnistis populiella.

Figure 38. Leaf blotch miner on 

cottonwood, Lyonetia sp.

Forest Defoliators
43

Willow Leaf Miner

Lepidoptera: Gracillariidae

Micrurapteryx salicifoliella (Chambers)

Hosts: Most species of willow with the exception of felt leaf willow, Salix 

alaxensis.

Distribution: Interior Alaska; predominantly in the upper Yukon River Flats 

area.

Identification: Later instars are pale yellowish in color and are approximately 

4.4–6.5 mm long. Mandibles have four distal teeth. Adults are small (wing‐

spans of 10.5–11.2 mm) grayish moths with mottled areas of dark and lighter 

areas on the forewings, emerge in August. Antennae are about as long as 

forewings. Eggs (pale green in color, 0.4 by 0.3 mm) are laid solitarily on the 

undersides of leaves. 

Damage: Most leaf mining Gracillariidae create necrotic blotches, either on 

the upper surface (as does M. salicifoliella) or on the lower surface. Willows 

can be completely defoliated for many consecutive years. Mortality as a result 

of heavy defoliation has been observed. Most willows, however, respond well 

(resprout) to disturbances whether insect induced, fire, or flooding. The long 

Figure 39. Willow leaf miner damage along Yukon River.

Forest Defoliators
44

term nutritional effect on large herbivores such as moose is unknown but war‐

rants investigation.

Remarks: Fourth and fifth instar larvae create necrotic, reddish blotches that 

often cover the entire upper leaf surface. Mature larvae exit through slits made 

on the undersides of leaves and spin silken coverings on the leaf surface before 

pupating. Adults emerge in late July and August and over-winter in that stage. 

Ten species of willow have been observed infested with the exception of felt 

leaf willow (S. alaxensis). Felt leaf willow is probably not infested due to its 

protective felt-like mat of hairs that prevent attachment of eggs to the leaf 

epidermis. A willow leaf miner outbreak infested hundreds of thousands of 

hectares in drainages of the Yukon and Kuskokwim Rivers from 1991–1999.

Forest Defoliators
45

Birch Leaf Miners 

Hymenoptera: Tenthredinidae

Profenusa thomsoni (Konow), Fenusa pumilla Leach, Heterarthrus 

nemoratus Klug 

Hosts: Native and exotic birch species, alder.

Distribution: One or more of these sawfly species has been associated with 

premature browning and early defoliation of birch trees in the Anchorage 

Bowl, the Fairbanks area, Haines, Skagway, and along roads on the Kenai 

Peninsula as far south as Soldotna. The most abundant species is the ambermarked birch leaf miner, P. thomsoni, but much about the roles, relative 

impacts, and distributions of the other two leaf miner species is unknown.

Identification: Full grown P. thomsoni larvae are flattened, about 6 mm long, 

white to pale green, and marked with black spots. Adult sawflies are about 

3 to 5 mm long and look like black flies with smoky wings and yellow legs. 

Males are extremely rare. Females reproduce parthenogenetically. Leaf mining 

sawfly larvae look similar to other leaf mining caterpillars.

Damage: The larvae of these leaf-mining sawflies eat the chlorophyll of a 

leaf between the epidermis layers, causing leaves to die, trees to defoliate, and 

trees across entire urban landscapes to turn brown. Affected trees are obvious 

and homeowners commonly enquire about this condition. Severity is unevenly 

distributed across urban areas. Impacts to urban trees include decreased aes‐

thetic values and cost of applying relatively expensive pesticides. Thousands of 

dollars each year are spent on using pesticides to suppress miner populations. 

Remarks: The amber-marked birch leaf miner is considered an important 

exotic invasive insect in Alaska. This insect was introduced to the east coast of 

North America from Europe in the early 1900s, spreading westward through 

Canada, to Alaska around 1990. It was first reported from Haines, Alaska in 

1992, and was probably present there since at 

least 1989.

Damage is usually apparent beginning in midsummer. Heavy defoliation can occur during 

a warm and dry spring/summer. Eggs are 

deposited on the leaves and emerging larvae 

immediately enter the leaf. Mature larvae drop 

to the ground to overwinter. Larvae pupate and 

adults, the overwintering stage, emerge the fol‐

lowing spring. There is probably one genera‐

tion per year.

References: 73

Figure 40. Birch leaf miner 

larvae inside a leaf.

Forest Defoliators
46

Hemlock Sawfly

Hymenoptera: Diprionidae

Neodiprion tsugae (Middleton)

Hosts: Primary host is western hemlock, secondary host is mountain hemlock. 

Distribution: Hemlock sawflies occur throughout Southeast Alaska. However, 

sawflies are more abundant and outbreaks are longer lasting in southern South‐

east Alaska where widespread damage is usually confined to the area south of 

Frederick Sound and west of Clarence Strait, the warmest areas in Southeast 

Alaska. The largest and earliest recorded outbreak occurred in 1952–3 on two 

million hectares from Frederick Sound to the south end of Prince of Wales 

Island. 

Identification: Newly emerged larvae are nearly all black, but later instars 

turn dark green. When larvae are nearly full grown, longitudinal stripes appear. 

Larvae of all instars have black head capsules. Mature larvae are 15–20 mm 

long. Adult sawflies are small, thick-waist wasps about 5–8 mm long. Females 

are larger than males, have serrated antennae, and are olive green, whereas 

males are black and have plumed antennae. 

Damage: Larvae feed on old foliage resulting in a reduction in host radial 

growth. Some top-kill is evident. 

Figure 41. Hemlock sawfly larva.

Figure 42. Hemlock sawfly adult.

Forest Defoliators
47

Remarks: Adults emerge and are active in September and October. Sawflies 

normally overwinter as eggs on host foliage, but will rarely overwinter in 

cocoons in forest litter. Eggs are deposited singly in characteristic pockets cut 

into edges of hemlock needles. Eggs hatch in June and larvae feed gregari‐

ously on old foliage. Larvae pupate in capsule-like cocoons on foliage or in 

litter during August and September.

Most sawfly outbreaks do not cause tree mortality, but some trees are topkilled and radial growth is temporarily reduced. Tree mortality becomes more 

apparent when sawfly and black-headed budworm populations coincide. 

This is due to the feeding habits of the two defoliators: the budworm feeds 

on current year’s foliage, whereas sawflies consume old foliage, thus causing 

complete defoliation. Many female sawfly larvae cannot successfully complete 

development on the current year’s foliage alone. 

Natural controls usually reduce epidemic sawfly populations within a few 

years. Wetter than normal summers help reduce sawfly populations by 

favoring conditions for fungal growth. Fungi readily infect and kill sawfly 

larvae under warm, damp conditions. Likewise, low summer temperatures 

help reduce sawfly populations. The apparent widespread collapse of sawfly 

populations in Southeast Alaska in l974 was associated with lower than normal 

1973 temperatures. Low temperatures delay sawfly development and reduce 

the opportunities for successful oviposition. Starvation and poor nutrition 

brought about by a depletion of host foliage contribute to population collapse 

by reducing sawfly health (increasing effectiveness of fungal infection) and 

fecundity (the number of eggs laid). 

References: 92, 93, 95, 96

Forest Defoliators
48

Larch Sawfly

Hymenoptera: Tenthredinidae

Pristiphora erichsonii (Hartig)

Hosts: Eastern larch (tamarack) and ornamental Siberian larch

Distribution: Interior Alaska; South-central Alaska.

Identification: Late instars have shiny black heads with bodies that are gray 

green along the back and a whitish colored underside. Tough, papery cocoons 

are brown in color and approximately 13 mm long. Adult females are 10 mm 

long with black antennae and black bodies. The abdomen of females has a 

broad orange band and tapers sharply towards the rear. Males have yellow 

antennae and an orange abdominal band, but the abdomen is cylindrical and 

rounded at the rear. Eggs are translucent and about 1.5 mm long.

Damage: Sawfly larvae eat the needles on the older parts of twigs. Heavy 

defoliation may cause a significant loss in growth. Larch growing on poor 

sites that have been defoliated for consecutive years may die outright, or are 

predisposed to attack by the larch beetle. Siberian larches withstand consecu‐

tive years of defoliation better than native larch.

Figure 43. Larch sawfly larvae.

Forest Defoliators
49

Remarks: Larch sawfly was present in detectable numbers by the mid-1960s. 

Significant larch sawfly defoliation was not observed in Alaska until the mid1990s. Large outbreaks (>150,000 hectares) developed in Interior Alaska and 

lasted for more than five consecutive years. Scattered larch mortality was espe‐

cially apparent on poorer sites. Adults emerge in early to late spring. Less than 

2 percent are males. Reproduction is largely parthenogenic. Each female lays 

20–200 eggs, depositing them under the bark of current year twigs. Recently 

emerged larvae move back to the foliage on older twigs and generally feed 

in groups. Mature larvae drop to the ground, enter the duff, and spin cocoons 

where they spend the winter.

Larch sawflies were introduced into South-central Alaska (Mat-Su Valley and 

Anchorage Bowl) in 1999 on Siberian larch, a common and highly desirable 

ornamental.

References: 58, 73, 246, 247

Forest Defoliators
50

Striped Alder Sawfly

Hymenoptera: Tenthredinidae

Hemichroa crocea (Geoffroy)

Hosts: Alder. 

Distribution: Southeast, Interior, and South-central Alaska 

Identification: Larvae are gregarious and chew holes through the leaf from 

the underside. When disturbed while feeding, larvae often assume a fishhook 

posture with the posterior end curled under and upward. Full grown larvae 

are 20 mm long with a black head and a yellow-amber body marked by dark 

brown lateral stripes. Eggs are laid in a row on the underside of the leaf petiole.

Damage: Repeated defoliation can cause some host growth reduction. 

Remarks: Biology is not well known in Alaska. In British Columbia there are 

two generations per year.

References: 73, 81, 93

Figure 44. Striped alder sawfly larvae.

Forest Defoliators
51

Alder Woolly Sawfly

Hymenoptera: Tenthredinidae

Eriocampa ovata (L.)

Hosts: Sitka, red and thinleaf alder

Distribution: Southeast and South-central Alaska

Identification: Little is known of the life stages other than all instars are cov‐

ered with a white woolly secretion, except the last instar.

Damage: Larvae skeletonize all leaves on alders. Damage is mostly cosmetic.

Remarks: Biology is not well known in Alaska. This is a European spe‐

cies that is now established from British Columbia to Alaska. Larvae feed 

throughout the summer months and overwinter as pre-pupae in cocoons in the 

soil. Adults emerge the following spring. There is probably no more than one 

generation per year in Alaska. Eggs are laid on underside of the leaf along the 

midrib. Larvae feed on the undersurface of the leaf.

References: 73, 246

Figure 45. Alder woolly 

sawfly larvae.

Figure 46. Alder woolly sawfly adult.

Forest Defoliators
52

Leaf Beetles

Coleoptera: Chrysomelidae 

Chrysomela walshi Brown, C. falsa Brown, C. interrupta (F.), 

Phratora sp., and Macrohaltica bimarginata (Say)

Hosts: Balsam poplar, black cottonwood, aspen, birch, alder, and willow. 

Distribution: Throughout Alaska.

Identification: Newly hatched larvae are flattened, dark grubs with welldeveloped legs. Adults are variously colored, either brown, green, reddish 

brown, yellowish green, and with or without black spots. They are approxi‐

mately 0.5 cm long and oval. The eggs are yellowish red. 

Damage: Adults feed on tender shoots. Larvae first skeletonize and later chew 

holes in the leaves. On cottonwoods, damage is usually most severe near the 

top of the tree.

Remarks: Leaf beetles overwinter as adults in leaf litter. Adult leaf beetles 

become active in early spring and feed on tender shoots. Eggs are deposited on 

the upper and undersurface of leaves. Newly emerged larvae feed gregariously 

during the first three instars. Larvae have been found quite late in the summer 

on alder and may do substantial feeding just prior to leaf fall. There is probably 

one generation per year in Alaska. 

References: 138

Figure 47. Leaf beetle larvae. Figure 48. Leaf beetle adult.

Forest Defoliators
53

Bud and Shoot Insects 

Bud and shoot insects are part of a larger group of insects that feed on meri‐

stematic tissue. Bud and shoot insects seldom kill a tree, but their damage can 

reduce the rate of terminal growth or cause deformities that affect the growth 

and merchantable value of timber and ornamentals. Fortunately, there are few 

bud and shoot insects attacking Alaska trees.

Figure 49. Spruce bud midge damage.

Bud and Shoot Insects
54

Spruce Bud Midge

Diptera: Cecidomyiidae

Rhabdophaga swainei Felt

Hosts: White, Lutz, black, and possibly Sitka spruce.

Distribution: Recurrent problem in South-central, Interior, and possibly 

Southeast Alaska.

Identification: Full grown larvae are pale pink, 1.5 to 2.2 mm long and 0.5 

to 1.0 mm wide. Pupae are 1.5 to 2.5 mm long and are enclosed in a deli‐

cate, transparent case. The adult is a small (2.5 mm) reddish-brown midge. 

The female has a reddish-brown thorax, but its abdomen and ovipositor are 

bright orange-red. The pale orange-pink eggs are 0.4 to 0.5 mm long and oval 

shaped.

Damage: The attacked bud becomes rosette-like due to drying and recurving 

of the bud scales. These galls are most numerous on the sunny sides and tops 

of open-grown spruce, which are from 1.5 to 3 m tall. Galls are commonly 

formed on the terminal buds of branches. The attacked bud is killed; elonga‐

tion of lateral buds the following year causes bushy growth. When the terminal 

shoot is attacked, a crook develops. In some cases multiple leaders result.

Remarks: The biology of the spruce bud midge is not fully understood in 

Alaska but is believed to be similar to that in Canada. Eggs are deposited 

between the young needles of developing shoots in early May. Newly hatched 

larvae burrow into the soft tissue of the developing bud. The insect overwinters 

in the larval stage. By the following May, pupae are formed and the galled bud 

becomes rosette-like. Adults emerge from mid-May. There appears to be one 

generation per year.

References: 36, 73

Figure 50. Spruce bud midge larva.

Bud and Shoot Insects
55

Spruce and Larch Budmoth

Lepidoptera: Tortricidae

Zeiraphera canadensis Mutuura & Freeman, Z. confusana 

Ferris & Kruse, Z. fortunana (Kearfott), Z. griseana (Hubner), Z. 

improbana (Walker), and Z. vancouverana McDunnough.

Hosts: White and Sitka spruce and eastern larch (tamarack). 

Distribution: South-central, Southeast, and Interior Alaska, Kodiak and Afog‐

nak Islands, Prince William Sound, and Yakutat Forelands. 

Identification: Larvae are 10–20 mm long, pale brown to greenish gray and 

the head and pronotum are yellowish-brown. Adults are small, grayish to 

brownish moths, with a wingspread of about 14 mm. Identification to species 

needs to be done by specialists.

Damage: New buds are mined by developing larvae. 

Remarks: In 1976, the larch budmoth was responsible for the defoliation 

of 239,000 hectares of larch in Interior Alaska. The trees did not die because 

defoliation occurred in the spring and the infested larch refoliated soon 

after. The larch budmoth overwinters as eggs under bark scales of twigs and 

branches of tamarack trees. Newly emerged larvae feed within a webbed tube 

constructed from several newly formed needles. Fourth and fifth instars live in 

lightly spun silken shelters along the branch axis and travel along the branch 

feeding on new and old needles. Larvae drop to the ground on silken threads 

and pupate in the forest litter. Females emerge and deposit eggs in late July. 

There is one generation per year.

References: 42, 43, 73, 142, 262

Figure 52. Spruce/larch budmoth adult.

Figure 51. Spruce and larch budmoth 

larvae.

Bud and Shoot Insects
56

Sap-Sucking Insects and Mites

Sap-sucking insects and mites are more important pests in orchards, gardens, 

or to shade trees than they are in the forest. Hosts are injured in two ways: (1) 

Directly by sapping the host of part of its food supply and water, producing 

necrotic spots in host tissue, and (2) Indirectly by introducing plant diseases.

The mouthparts of these insects and mites are formed into beak-like structures 

that are used to pierce host tissues and suck the sap. Damage by sap-sucking 

insects is often mistakenly regarded as disease caused. A few of the sap-suck‐

ing insects are able to kill their hosts outright, but damage usually results in 

reduced growth rates and a general weakened condition. Trees injured by 

these insects may succumb to secondary insects or fungal diseases. Signs of 

sap-sucking insect damage consist of enlarged growths or galls, leaf curling, 

bleaching, or yellowing of foliage. Conifers are more severely injured than 

hardwoods. 

In Alaska, there are several sap-sucking insects that cause noticeable damage 

to trees and shrubs. These pests can cause appreciable problems to urban 

woodlands and parks. Use of a hand-lens will help in detection and identifica‐

tion, as these organisms are quite small.

Figure 53. Aphids: A. adult; B. nymph; C. Woolly aphid nymph.

Sap-Sucking Insects and Mites
57

Spruce Aphid

Homoptera: Aphididae

Elatobium abietinum Walker

Hosts: Feed on most species of spruce, but are most damaging to Sitka spruce.

Distribution: Spruce aphid populations have infested several areas in South‐

east Alaska and occasionally Kodiak Island causing severe defoliation and lim‐

ited tree mortality. Serious damage has sporadically occurred near Sitka where 

many trees have been killed. The more severely defoliated trees were weak‐

ened and attacked by bark beetles that had built up in adjacent windthrows. 

In recent years, the needle aphid has been a recurring urban problem around 

Sitka, Craig, Juneau and Ketchikan.

Identification: Nymphs are oval, green and wingless, approximately 0.5–1.4 

mm long. Adult aphids may be either wingless or winged. Wingless adults are 

about 1.5 mm long, oval, green, with a yellow-green head and dull red eyes. 

Winged adults are bright green with translucent legs. The transparent wings 

are longer than the body that is approximately 1.0–1.8 mm long. In most of 

Europe and Alaska, female aphids parthenogenetically (reproduction without 

fertilization) give birth to live young (viviparous). Eggs have not been found in 

Alaska, so the life cycle continues without males or fertilized females (anholo‐

cyclic). 

Figure 54. Spruce aphid damage on Sitka spruce, Sitka, Alaska.

Sap-Sucking Insects and Mites
58

Damage: Partial or complete defoliation and occasional tree mortality. Spruce 

occurring along tidewater areas that are in “fringe areas” or in other “stressed” 

locations (urban plantings) are susceptible to aphid damage.

Remarks: This insect was introduced from Europe into the North American 

Pacific Northwest in the early 1910s. Spruce aphids are abundant and most 

damaging in early spring and again in fall. Some limited feeding can occur in 

summer and winter. Population increases in spring and fall are due to a variety 

of factors. An increase in soluble nitrogen in spruce foliage at these times 

favors aphid increases. At bud break, around the first week of June, nitrogen 

levels drop and is followed by a decrease in aphid reproduction. Likewise, 

mild winter temperatures, minimums that do not go below about 0°F, contrib‐

ute to aphid buildups. Epidemic aphid populations will usually remain high 

for only a few years, and then collapse to previous low levels. Factors causing 

declines include intraspecific competition for food and low winter tempera‐

tures. Temperatures well below freezing, when overwintering aphids are 

emerging en masse, and snowfall (snowfall protects overwintering adults from 

freezing) are the most important controlling factors. Since the 1970s, aphid 

defoliation has occurred on thousands of hectares per year except for a few 

years when late winter temperatures were limiting emerging aphids.

Control of spruce aphids on ornamentals can be done with commercially avail‐

able insecticides labeled for aphid control.

References: 18, 46, 51, 93, 133, 156

Figure 55. Spruce aphids.

Sap-Sucking Insects and Mites
59

Giant Conifer Aphids

Homoptera: Aphididae

Cinara nigripes Bradley and C. piceae (Panzer)

Hosts: White and Sitka spruce.

Distribution: Throughout Alaska.

Identification: These aphids have long legs. The giant conifer aphid on white 

spruce is believed to be Cinara nigripes. This aphid is black with a body 

length of approximately 5 mm. The species on Sitka spruce is believed to be 

Cinara piceae, brown colored with a body length of 3.4 mm long. Sometimes 

they are lightly covered with a powdery wax. The eggs are blackish, laid singly 

or in rows on the needles.

Damage: Large aphid populations can cause yellowing of the foliage and 

reduce tree growth, especially on young trees. Black sooty mold, growing on 

the honeydew exuded by the aphids, is common.

Remarks: The life cycle of these aphids is complex; up to six generations a 

year can occur in Canada. All species overwinter in the egg stage. Most Cinara 

feed gregariously and are usually attended by ants that feed on the honeydew. 

Males occur in the fall generation.

Control is seldom necessary. However, contact insecticides may be used on 

heavily infested, ornamental spruce.

References: 24, 73, 195

Figure 56. Giant conifer aphids.

Sap-Sucking Insects and Mites
60

Spruce Gall Aphids

Homoptera: Adelgidae

Adelges abietis (L.), Pineus similis (Gillette), and A. cooleyi 

(Gillette)

Hosts: Sitka, white, and Lutz spruce.

Distribution: Throughout Southeast, South-central, and Interior Alaska.

Identification: The galls are light green to dark purple while developing in 

the first year but become reddish brown the second year after the aphids have 

vacated the galls. Galls range in length from 1 to 5 cm long. Adults are oval, 

reddish brown, and 1 mm long. Nymphs are oval, reddish to yellowish brown 

and sometimes covered with a white woolly material.

Damage: These aphids cause the tree to form conspicuous cone shaped galls 

on spruce twigs. Repeated attacks by the insect can result in dead twigs and a 

ragged appearance of the foliage.

Remarks: The life history of gall aphids on spruce is not well known in 

Alaska. Both the ragged spruce gall aphid Pineus similis and the eastern 

spruce gall aphid Adelges abietis are believed to be the causal agents in white 

spruce. Both these aphids have no alternate hosts and can have two generations 

per year. In Sitka spruce the Cooley gall aphid Adelges cooleyi is believed to 

cause the characteristic galls. Eggs are laid by the overwintering aphids in 

May. The eggs give rise to three types of aphids, two of which cause galls to 

form. The galls increase in size during the summer until they open, releas‐

Figure 57. Spruce gall aphid damage on white spruce.

Sap-Sucking Insects and Mites
61

Figure 58. Galls from the ragged spruce gall aphid, Pineus similis.

ing the winged adults. These adults lay eggs in July, which produce the new 

overwintering generation.

Removing and burning green galls is an efficient control for high value trees 

if done before aphid adult emergence in the summer. A systemic insecticide 

applied as the buds begin to swell in the spring can provide control.

References: 42, 45, 73, 132, 153, 195

Sap-Sucking Insects and Mites
62

Woolly Adelgids

Homoptera: Adelgidae

Adelges tsugae Annand, Pineus similis (Gillette), and A. cooleyi 

(Gillette)

Hosts: Western hemlock, Sitka, white, and Lutz spruce. Also has been identi‐

fied on transplanted Douglas-fir in Sitka, Alaska in 1990.

Distribution: Throughout Alaska.

Identification: Young aphids are broadly ovoid, 0.3 mm to 0.6 mm long; yel‐

lowish-brown. Later stages are dark brown to black, covered with white, waxy 

wool.

Damage: Woolly tufts on needles and twigs. Woolly aphids are of little conse‐

quence in the forest but large populations can seriously weaken and sometimes 

kill ornamental trees. Infested foliage becomes yellowish-brown. After severe 

infestations, the foliage may turn brown and fall from the branches.

Figure 59. Woolly aphids on white spruce.

Sap-Sucking Insects and Mites
63

Remarks: The hemlock woolly adelgid, Adelges tsugae, has a one-year 

life cycle and feeds only on hemlock. Populations probably consist only of 

females that are able to reproduce asexually.

The biology of woolly adelgids on spruce is not fully understood in Alaska. 

The aphids are believed to be either the ragged spruce gall aphid (P. similis) 

or the eastern spruce gall aphid (A. abietis). Immature stages of these aphids 

produce waxy wool. There is the possibility that a monotypic population of A. 

coolleyi is responsible for the waxy wool on spruce. Asexual populations of 

this aphid live on spruce year around producing woolly tufts but not galls.

If chemical control is necessary, strict attention to timing of spray applications 

is essential. In general, chemical control is more effective when directed at the 

immature stages, particularly in the spring. Both systemic and contact insecti‐

cides can provide control.

References: 45, 73, 132, 153

Sap-Sucking Insects and Mites
64

Spruce Bud Scale

Homoptera: Coccidae

Physokermes piceae (Schrank)

Hosts: White, Lutz, and possibly Sitka spruce

Distribution: Bud scale insects have only been collected from the Anchorage 

area. However, they probably occur in Interior Alaska as well.

Identification: The mature bud scale, which is frequently mistaken for a bud, 

is yellowish to reddish brown, semi-globular, and about 1.5 to 3 mm long and 

3 mm in diameter. The female adult scales very closely resemble spruce buds 

and consequently, often go unnoticed. 

Damage: Urban ornamental trees are more commonly infested than those in 

forested settings. Heavily infested trees are weakened which causes needle 

loss. Lower branches may be killed. Sooty mold, growing on the honeydew 

exuded from the scales, is common.

Remarks: The biology is not well known in Alaska. There is one generation a 

year in Canada and the Lake States. Immature individuals overwinter in clus‐

ters around terminal buds. They resume feeding in the spring and mature in 

early summer. Eggs are laid under the adult female scale. The young crawlers 

move to the tips of twigs where they feed until late fall.

When control is necessary, a systemic insecticide applied in early August or a 

contact insecticide applied from late June to late July should prove effective.

References: 73, 195, 275

Figure 60. Spruce bud scales.

Sap-Sucking Insects and Mites
65

Birch Aphid

Homoptera: Aphididae

Euceraphis betulae (Koch.)

Hosts: Alaska birch.

Distribution: Large aphid populations on Alaska birch causes concern in 

Interior and South-central Alaska. Browning of birch foliage covered more 

than 50,000 hectares near Chickaloon and along the Matanuska River in the 

mid-1970s. The next summer, various species of aphids were present in high 

numbers in mixed hardwood/spruce stands covering nearly 120,000 hectares 

near Palmer urban areas. Aphid defoliation was responsible for large amounts 

of honeydew, leaf-curling and browning on ornamental birch in both cities. 

Identification: Small, greenish brown aphids; both winged and wingless 

forms may be present. 

Damage: Leaf-curling and browning.

Remarks: The lifecycle is not well documented in Alaska. Other aphids, such 

as Ericosoma sp. and Mordwilkoja sp. generally cause some leaf-curling, 

browning, and some limited dieback on aspen and spruce throughout Interior 

Alaska. They are commonly encountered in the field although their damage is 

of minor concern.

References: 9, 11, 142

Figure 61. Birch aphids. Figure 62. Birch aphid damage.

Sap-Sucking Insects and Mites
66

Hardwood Gall Insects

Diptera: Cecidomyiidae

Rhabdophaga rosaria (H. Loew), R. strobiloides Walsh.

Hymenoptera: Tenthredinidae 

Pontania s-pomum (Walsh)

Hosts: Willow spp., aspen, cottonwood.

Distribution: Throughout Alaska.

Identification: A variety of minute insects are involved, from small fly mag‐

gots to wasps. Galling is a response by the host to insect feeding.

Figure 63. Willow rose gall. Figure 64. Willow gall wasp.

Figure 65. Pine cone gall on 

willow, Rhabdophaga sp.

Sap-Sucking Insects and Mites
67

Damage: Galling can result in limited growth reduction. The appearance of 

galled leaves is an aesthetics concern of some homeowners.

Remarks: The life cycles of these insects are complex and not well known 

in Alaska. Control is seldom necessary. Early spring applications of systemic 

insecticides provide adequate control.

References: 5, 37, 40

Sap-Sucking Insects and Mites
68

Spittlebug

Homoptera: Cercopidae

Aphrophora sp.

Hosts: Sitka spruce seedlings, hardwoods, and ground vegetation.

Distribution: Southeast and South-central Alaska. 

Identification: Both the adult and nymph feed on plant fluids; only nymphs 

make spittlemass that serves as a protective covering. Young nymphs are red 

and black; older nymphs are brown. Adults are brown to black and similar to 

nymphs but with wings. Eggs are teardrop in shape. 

Damage: Dead tops, flagged branches, wavy and slanted stems, shortened 

stem and branch internodes. 

Remarks: Biology is poorly known in Alaska. 

References: 46, 275

Figure 66. Spittle mass with spittle bug nymph.

Sap-Sucking Insects and Mites
69

Spider Mites: Acarina

Acari: Tetranychidae

Oligonychus ununguis (Jacobi), Tetranychus urticae Koch 

Hosts: Conifers. 

Distribution: Throughout Alaska; prevalent in urban areas. 

Identification: Adults are 0.5 mm long with a globular body, four pairs of 

legs, and no antennae. The spider-like adults are greenish to reddish-brown. 

Nymphs are similar to adults but have only three pairs of legs. 

Damage: Fading (brown) host foliage falls prematurely.

Remarks: Biology of the red spider mite is unknown in Alaska. Generally 

spider mites overwinter as eggs or adults. There are many generations per year. 

Females can lay from two to four dozen eggs. The presence of mites can be 

detected by webbing on the foliage that contains considerable debris. Adults, 

due to their small size, can be detected with a hand lens.

References: 3, 275

Figure 67. Spider mite damage.

Sap-Sucking Insects and Mites
70

Eriophyid Mites

Acariformes: Eriophyidae

Eriophyes spp.

Hosts: Willow, alder, mountain ash, and birch.

Distribution: Throughout Alaska.

Identification: Eriophyid mites are very small (200 microns) and observation 

requires a hand lens or microscope. Unlike the familiar form of spider mites, 

eriophyid mites are elongated, worm-like, and have only two pairs of legs 

instead of the usual four pairs.

Damage: Eriophyid mite feeding causes plant abnormalities such as galls and 

felt-like mats. Most damage is primarily cosmetic as eriophyid mite feeding 

induces leaf edge rolling, or causes the leaf surface to blister. Growth of the 

host may be reduced if the tree is heavily infested for many years.

Remarks: The life cycle is fairly simple. Within a growing season, the mites 

develop through four stages: egg, first nymph, second nymph, and adult, which 

is the overwintering stage. Eriophyid mites travel between hosts by air cur‐

rents, or by hitching rides on insects or birds.

References: 20, 73, 207

Figure 68. Eriophyid mite damage.

Sap-Sucking Insects and Mites
71

Bark Beetles

Bark beetles are common in Alaska where more than 50 different species are 

known to occur (76). Only a few of these are actually pests of forest trees. In 

fact, most bark beetles are usually positive components of the ecosystem, 

where they help break down woody debris, catalyze nutrient cycling, create 

structural diversity in otherwise continuous forest stands, enhance aesthetic 

values of the forest, and provide other important ecosystem services. 

Sometimes, however, beetles kill living trees and cause socioeconomic or eco‐

logical damage or both. Some beetle-caused impacts include: 1. Loss of mer‐

chantable value of killed trees, 2. Long-term stand conversion, 3. Positive and 

negative impacts to wildlife habitat, 4. Impacts to scenic quality, 5. Increased 

fire hazard, 6. Impact to fisheries, 7. Impact to watersheds, and others. 

As a group, certain traits and habits are common to all Alaska’s bark beetles:

• Adults excavate egg galleries in bark phloem.

• Most bark beetles prefer weakened host material. 

• All bark beetle life stages are spent in the phloem, inner bark and bark, 

except when adults fly to new hosts. 

Bark beetles prefer to breed in weakened host material. However, with 

abundant host material and during favorable climatic periods for beetle 

development, populations may build rapidly, reaching levels high enough to 

overwhelm tree defenses and infest and successfully colonize neighboring 

healthy trees. Bark beetles disrupt downward translocation of food by girdling 

the phloem. 

Some of the bark beetles, notably those of the genus Dendroctonus, have a 

symbiotic relationship with blue-stain fungi. Blue-stain fungi can completely 

penetrate the sapwood within a year, occluding the outer conducting tissues in 

the xylem, and halting upward water translocation. This action in combination 

with bark beetle feeding presumably causes the death of a host tree.

Crowns of heavily infested trees turn from green to yellow to reddish brown. 

This color change may occur from one to two years after being attacked, 

depending on temperature, moisture, and beetle density. Inspection of infested 

boles might show globules of resin, holes in the bark surface, and reddish 

boring dust in bark crevices and/or at the base of the tree. The removal of bark 

from infested trees will reveal two types of galleries. Egg galleries created by 

adult beetles that are more or less uniform in width. Larval galleries created 

by feeding larvae that gradually increase in width as the larvae grow in size, 

and originate at right angles from the egg gallery. Differing gallery patterns are 

often used to distinguish among the different bark beetles species.

References: 77

Bark Beetles
72

Figure 69. Spruce beetle galleries.

Figure 70. Spruce beetle life stages: A. adult; B. pupa; C. larva.

Bark Beetles
73

Spruce Beetle

Coleoptera: Curculionidae, Scolytinae

Dendroctonus rufipennis (Kirby)

Hosts: Lutz, white, Sitka, and at times, black spruce. 

Distribution: Wherever spruce is present, especially in South-central Alaska.

Identification: Adult spruce beetles are dark brown to black, cylindrical in 

shape, approximately 5 mm long and 3 mm wide. The larvae are stout, white, 

legless grubs, 6 mm long at maturity. The pupae are white, soft-bodied, and 

adult shaped. 

Damage: Kills standing trees.

Remarks: The spruce beetle generally has a two-year life cycle, but this can 

be shortened to one-year if climatic conditions (warm and dry spring and 

summer) are favorable and there is an abundance of suitable host material. 

Adult and larval activity begins in May when daytime temperatures under 

bark reach 6.7° C (47° F) (263). Adult beetles disperse in late May and early 

June when daytime ambient temperatures reach 16° C (62° F) and above . 

Dispersing adults can fly as far as 11 kilometers nonstop, but dispersal distance 

is usually much shorter than this. Females are initially attracted to windthrow 

and other downed material and initiate attack; males arrive later.

Spruce beetles prefer to attack on the sides and bottoms of downed host mate‐

rial. Attacking female beetles release pheromones that attract other male and 

female beetles. The monogamous females deposit approximately 80 eggs in 

niches along the sides of the vertical egg gallery in standing trees. Egg galler‐

ies are packed with frass and boring material, and often have a fan shape. Most 

eggs hatch by August. 

Figure 71. Spruce beetle adult, lateral view.

Bark Beetles
74

Spruce beetles typically overwinter as larvae during the first year, and pupate 

the following summer. Pupation lasts 10–15 days. Most newly formed adults 

migrate to, and overwinter under the bark in the snow-covered base of the 

trees in which they developed. During the cold of winter, the snow that covers 

the base of infested trees insulates the beetle’s domain. The following spring 

(approximately two years after attack) adults emerge from the tree and attack 

new host material. 

Most D. rufipennis outbreaks in standing timber have originated in 

windthrown trees or large diameter logging residue. In the Rocky Mountains, 

and probably Alaska also, host susceptibility decreases in the following order: 

(1) large diameter trees along creek bottoms, (2) trees in better stands on 

benches, (3) trees in poorer sites on ridges and benches, (4) stand mixtures of 

spruce and other species, and (5) stands of immature trees. 

References: 7, 74, 87, 93, 140, 189–192, 198, 261, 264, 266, 267, 277

Figure 72. Spruce beetle larvae.

Bark Beetles
75

Figure 74. Spruce beetle boring material (frass) at the base of an 

attacked tree.

Figure 73. White spruce killed by the spruce beetle.

Bark Beetles
76

Figure 75. Unacceptable right-of-way cleanup.

Figure 76. Acceptable right-of-way cleanup.

Bark Beetles
77

Eastern Larch Beetle

Coleoptera: Curculionidae, Scolytinae

Dendroctonus simplex LeConte.

Hosts: Tamarack (Eastern larch) 

Distribution: Interior Alaska. Historically, larch beetle infestations have 

been reported across the entire range of tamarack in Alaska. Outbreaks have 

exceeded 215,000 hectares. 

Identification: Adults and larvae are very similar to the spruce beetle (see 

figure 71) although somewhat smaller. Adults are reddish brown to black.

Damage: Attacks weakened tamarack and subsequently causes host mortality. 

Remarks: Adults are active from the last week of May through the second 

week of July. Pitch tubes occur rarely on infested tamarack because of the 

host’s weakened condition at the time of attack. Trees can be weakened by 

successive years of larch sawfly defoliation, drought, or smoke damage from 

frequent wildfires in the black spruce wetlands where tamarack is most com‐

monly found.

Egg galleries are vertical and approximately 20–25 cm in length. Larval tun‐

nels occur in groups of 3–6 or more and do not cross. Larch beetles usually 

overwinter as adults under host bark at the base of the tree and emerge in the 

spring. 

References: 9, 10, 142, 277

Bark Beetles
78

Engravers

Coleoptera: Curculionidae, Scolytinae

Ips perturbatus (Eichhoff), I. tridens (Mannerheim), I. borealis 

Swaine, I. concinnus (Mannerheim), I. pini (Say), and I. latidens 

(LeConte) spp.

Hosts: White, black, Lutz, and Sitka spruce. 

Distribution: Throughout Alaska, but more prevalent in the Interior. These 

beetles are known for their opportunistic use of trees damaged by fire, drought, 

flooding, and human development activities that alter forest stands.

Identification: Adults are small (0.3–0.6 cm long), cylindrical, reddish brown, 

and black beetles. The head is not visible when the insect is viewed from 

above. A distinguishing feature of all Ips is a pronounced declivity (concave 

area) on the posterior end, which is margined with three or four pairs of toothlike spines. 

Larvae are segmented, soft-bodied, whitish, elongate cylindrical, legless grubs. 

Head color is tan, and the thoracic segment is enlarged. 

Damage: Cause mortality to saplings, pole-sized, and mature trees. 

Remarks: Several engraver species live in Alaska. Most are similar in size, 

coloration, and habits. The first evidence of Ips attack is the presence of fine, 

yellow-red boring dust in bark crevices. Unlike spruce beetle damage/injury, 

pitch-tubes of Ips are rarely formed in response to Ips infestations. Adults 

disperse to new host material as early as mid-April. Preferred host material 

Figure 77. Ips adult, lateral view.

Bark Beetles
79

Figure 78. Engraver frass.

includes freshly cut logs, and tops of weakened trees. Dispersal is temperaturedependent, and can occur from early May through early August, depending on 

the species.

Ips are polygamous. Males Ips initiate tree attacks, after which male and 

female adults aggregate in response to pheromones (and some host chemicals) 

in the initial galleries. Engravers and spruce beetles commonly occur at the 

same site, but the former prefer sunnier and drier host material.

After boring into the bark, males construct an enlarged chamber called a 

nuptial chamber in the inner bark adjacent to the entrance hole. Adults females 

construct egg galleries which radiate from the nuptial chambers. In contrast to 

those produced by spruce beetles, Ips egg galleries are kept clear of frass and 

boring dust. 

Figure 79. Engraver galleries.

Bark Beetles
80

Preventive measures are the best suppression measure for Ips buildup. By 

preventing slash accumulation or by burning infested Ips material or scatter‐

ing slash in very sunny locations help reduce engraver buildup. Direct control 

operations generally are not used against Ips as outbreaks develop and disap‐

pear rapidly, usually within three years.

References: 3, 16, 31, 73, 78, 79, 86, 91, 134–136

Bark Beetles
81

Hemlock Hylesinus

Coleooptera: Curculionidae, Scolytinae

Pseudohylesinus tsugae (Swaine)

Hosts: Western hemlock. 

Distribution: Southern Alaska, especially the Southeast portion of the state. 

Identification: Adult beetles are stout, oval bark beetles 3.2 to 4.5 mm long 

and reddish brown.

Damage/Injury: Larval galleries reduce host tree vigor. 

Remarks: The hemlock hylesinus breeds in felled or weakened western 

hemlock and can sometimes kill healthy trees. Before infesting slash, female 

beetles make short feeding galleries on live trees, but abandon these galleries 

within one or two weeks. This phenomenon has been observed in numerous 

thinned stands on Prince of Wales Island. Egg galleries of this beetle are simi‐

lar to those made by Scolytus spp.

References: 73, 91, 153

Figure 80. Hemlock hylesinus gallery.

Bark Beetles
82

Cedar Bark Beetle

Coleoptera: Curculionidae. Scolytinae

Phloeosinus cupressi Hopkins, P. punctatus LeConte, and P. 

sequoiae Hopkins.

Hosts: Western redcedar and Alaska yellow-cedar. 

Distribution: Southeast Alaska. 

Identification: Adults are commonly reddish to dark brown and approxi‐

mately 2 to 4 mm in length. The head is visible from above; antennal clubs are 

conical, and the eyes are deeply notched. 

Damage: Weakened standing trees may be killed in rare cases.

Injury: Feeding adults cause twig and branch dieback. In rare cases, weak‐

ened hosts are killed.

Remarks: Phloeosinus spp. is composed of a group of 25 species in the U.S. 

and Canada often referred to as the cedar bark beetles. Members of this group 

are rarely aggressive enough to kill healthy trees. Attacks usually occur on 

stressed or recently dead trees, and on debris from harvested or pruned trees. 

Newly emerged adults feed on twigs, sometimes causing flagging in the crown 

of infested trees. Phloeosinus cupressi, the cedar bark beetle, only infests large 

branches and main boles of Alaska yellow-cedar in advanced stages of decline. 

Infested trees become susceptible to the stem rot fungus Coryneum cardinale, which is often found fruiting on infested trees. Phloeosinus punctata, 

the western cedar bark beetle, has been reported in Alaska only a few times. 

The host is western redcedar. P. punctuata is considered to be of relatively 

low significance, causing little damage or concern. Adults are 2 to 3 mm long 

with reddish brown elytra and a black shiny body. Phloeosinus sequoiae, the 

redwood bark beetle, infests both western redcedar and Alaska yellow-cedar. 

Host mortality has sometimes occurred. Infestations have been correlated to 

poor sites. Apparently, P. sequoiae is more aggressive, and adults much larger, 

than the other Alaskan Phloeosinus species. 

References: 3, 53, 55, 73, 93, 105, 153, 252

Bark Beetles
83

Four-Eyed Bark Beetle

Coleoptera: Curculionidae, Scolytinae

Polygraphus rufipennis (Kirby)

Hosts: Sitka, white, Lutz, and black spruce and lodgepole pine. 

Distribution: Throughout Alaska wherever suitable hosts are found. 

Identification: Adult beetles are stout, cylindrical, approximately 2 to 3 mm 

long, and reddish brown to black. The two compound eyes are each restricted 

giving the impression of four eyes. 

Damage: Often found feeding beneath the bark in dry and small branches of 

stressed or dead trees. The four-eyed bark beetles are not important pests in 

Alaska. 

Remarks: P. rufipennis adults actively disperse in search of downed logs or 

dead trees from June to early July, taking flight whenever temperatures exceed 

16° C (61° F). Females select the host. Mating takes place in a nuptial chamber 

in the inner bark. Females excavate egg galleries and lay approximately twenty 

eggs, then emerge and initiate a second or third egg gallery in the same or a 

different host. Egg galleries are usually full of frass. One generation occurs 

each year. Breeding adults overwinter and resume breeding the following 

spring, which is rare among bark beetles. 

References: 16, 53, 78, 79

Bark Beetles
84

Coleoptera: Curculionidae, Scolytinae

Dryocoetes confusus Swaine, D. affaber (Mannerheim), D. 

autographus (Ratzeburg), D. caryi Hopkins

Hosts: Subalpine fir, Sitka spruce, white spruce, Lutz spruce, western hem‐

lock, and lodgepole pine. 

Distribution: Throughout Alaska wherever susceptible host material is found. 

Identification: Adults are 2.5 to 5.0 mm long, blackish with a distinguishable 

tuft of “hair” on the head.

Damage: These beetles cause little or no economic impact. Larval galleries 

are found under the bark of dead and weakened host material. 

Remarks: Biology of these species is poorly known in Alaska. However, 

biological information from Canada and the contiguous United States indicate 

that beetles disperse to new host material during July. Dryocoetes spp. is usu‐

ally found with dead, stressed, or downed trees. They are polygamous, usually 

three or four females associated with one male that initiates attack. Egg galler‐

ies are irregular in shape. Eggs are laid in niches cut into the gallery wall and 

are covered with frass. Larval galleries twist and cross frequently showing little 

orientation with respect to the wood grain. There is one generation per year. 

References: 16, 31

Figure 81. Dryocoetes adult, lateral view.

Bark Beetles
85

Willow Bark Beetle

Coleoptera: Curculionidae, Scolytinae

Trypophloeus striatulus (Mann.)

Hosts: Primarily felt leaf willow.

Distribution: Interior Alaska.

Identification: Adult beetles are brown to black in color and about 2.0 mm 

long with scaly elytra, especially toward the rear. Larvae have three instars. 

The third instar is snow white, approximately 3.0 mm long. Eggs are translu‐

cent white, oblong, and 0.7 x 0.4 mm. Pupae are white and eyes and mandibles 

turn blackish-brown when mature.

Damage: Adults attack the larger stems and trunks of decadent, overmature 

willow. Stems are re-attacked many times over a number of years resulting in 

stem death.

Remarks: New adults appear in August, probing the host bark for a site to 

bore a chamber in which they spend the winter. Adults emerge from overwin‐

tering sites in the spring and construct a brood chamber under the bark where 

they mate and construct an egg gallery. Emerging adults usually do not dis‐

perse far, preferring to re-attack the same stem for several generations, thereby 

conserving a limited resource. 

References: 31, 72, 73

Figure 82. Infested willow stem with adult 

entrance and exit holes.

Figure 83. Willow bark beetle eggs and 

gallery.

Bark Beetles
86

Wood Borers

This group consists of several orders (Lepidoptera, Hymenoptera, and Cole‐

optera) and families which bore into the sapwood and, at times, the heartwood 

of weakened, recently felled or dead hardwoods and conifers. Included here 

are the long-horned beetles or round-headed borers (Coleoptera: Cerambyci‐

dae), flat-headed or metallic woodborers (Coleoptera: Buprestidae), horntails 

(Hymenoptera: Siricidae), ambrosia beetles (Coleoptera: Curculionidae), the 

ghost moths (Lepidoptera: Hepialidae), and pitch moths (Lepidoptera: Sesii‐

dae). Most of these borers normally attack only freshly cut, injured, dying, 

or recently dead hosts. However, under certain circumstances, they can cause 

substantial economic losses in the form of wood degrade and volume loss. 

Figure 84. Wood borer 

larvae: A. round-headed borer 

(Cerambycidae); B. flat-headed 

borer (Buprestidae).

Wood Borers
87

Round-headed Borers or Long-horned Beetles 

Coleoptera: Cerambycidae

The larvae of this group of insects live as borers in the tissues of trees and 

other woody plants and are at times serious pests. Smaller trees are sometimes 

girdled and killed. The sapwood and heartwood of larger trees are riddled 

and weakened and become susceptible to wind breakage or death. Roundheaded borers reduce both grade and volume in logs and pulpwood and also 

introduce stain-causing fungi that degrade lumber values. Adults may emerge 

from bark beetle-killed timber used as house logs after the log house has been 

constructed.

Those round-headed borers that require moist, sometimes decayed dead wood 

are generally beneficial. They are considered the most prominent insects 

involved with decomposition of slash, stumps, and dead and dying trees in 

north temperate forests. 

Round-headed borer larvae are characterized by a whitish-elongate-robust to 

slender body. They are soft, fleshy, and cylindrical to somewhat flattened in 

shape, with the head slightly flattened. Adult beetles are cylindrical, oblongelongate to somewhat flattened, sometimes brightly colored. The antennae 

are long and slender, usually 11-segmented, and as long as or longer than the 

body. Some species make squeaking noises when disturbed, and the larvae of 

the “sawyers” produce a loud noise while boring.

Wood Borers
88

White-spotted Sawyer

Coleoptera: Cerambycidae

Monochamus scutellatus (Say)

Hosts: White, Lutz and occasionally, black spruce. 

Distribution: Inland forests of Interior and South-central Alaska. 

Identification: Full grown larvae are approximately 50 mm long, whitish, 

elongate and cylindrical with a soft, legless body, and dark brown mandibles. 

The head is slightly flattened. Adults are stout, dull black beetles, 2.5 cm long 

with gray-white markings on wing covers; tooth-like projections on sides of 

prothorax. Female antennae are longer than its body; male bodies are larger 

and stouter than the female with antennae over twice as long as its body.

Damage: The larvae bore into dead or dying trees and often introduce wood 

rotting fungi. Adults sometimes feed on the bark of branches and the foliage. 

Flagging of lateral twigs and foliage occurs when wood borer populations are 

high, e.g. during harvest operations and on the fringes of burned areas. Flag‐

ging is the result of adult maturation feeding.

Remarks: Sawyer beetles are strong fliers and can travel several kilometers. 

The beetles need to feed on twigs of healthy trees in order to mature and breed. 

This so-called maturation feeding causes minor damage to the twigs. Female 

sawyers emerge in early June to mid-August and deposit eggs under the bark 

scales of dying trees. Newly developed larvae feed in the cambium and heavily 

scour the sapwood surface. Coarse, splintery larval frass, characteristic of cer‐

ambycids, is usually present on or in infested material. Larvae tunnel into and 

overwinter in the sapwood. The second year is spent in the larval stage with 

pupation and adult emergence occurring the following spring. 

References: 53, 73, 79, 91, 175

Figure 85. White-spotted sawyer.

Wood Borers
89

Coleoptera: Cerambycidae

Xylotrechus undulatus (Say)

Hosts: White and Lutz spruce. 

Distribution: Interior and South-central Alaska. 

Identification: Adults are stout and cylindrical from 12–19 mm long with 

antennae only slightly longer than combined length of head and thorax. Wing 

covers are black and sharply outlined with white crescent shaped markings. 

Damage: The larvae bore into dead or dying trees and often introduce wood 

rotting fungi. 

Remarks: The biology is not well known in Alaska. 

References: 73, 79

Figure 86. Xylotrechus adult.

Wood Borers
90

Other Alaska Cerambycidae:

Acmaeops p. proteus (Kby.)

Phymatodes dimidiatus (Kby.)

Pogonocherus mixtus Hald.

Pogonocherus penicillatus LeC.

Arhopalus productus (LeC.)

Elaphidion sp.

Neacanthocinus pusillus (Kby.)

Pachyta lamed (LeC.)

Gnathacmaeops pratensis (Laich.)

Grammoptera subargentata (Kby.)

Neoclytus m. muricatulus (Kby.)

Callidium cicatricosum Mann.

Judolia m. montivagans (Cooper)

Pronocera c. collaris (Kby.)

Tetropium cinnamopterum parvulum (Csy.)

Tetropium velutinum LeC.

Hosts: White, Sitka, Lutz, and black spruces. 

Distribution: Throughout Alaska.

Remarks: The biologies are not well known in Alaska.

References: 77, 78

Wood Borers
91

Metallic or Flat-Headed Wood Borers 

Coleoptera: Buprestidae

Unlike the cerambycids, the buprestids almost never develop in decayed wood; 

they are restricted to recently weakened or killed material. The buprestids are 

destructive in that they sometimes kill living trees and often reduce the value 

of lumber through their attacks. The winding larval galleries, present in the 

sapwood and heartwood, are characteristically tightly packed with boring 

material. 

Adults are flattened, frequently brightly colored, iridescent beetles with short 

antennae. Females oviposit in bark crevices, and developing larvae construct 

long, winding, oval galleries in the bark and/or the wood. Adults of many spe‐

cies can successfully attack and develop in pitchy fire scars on living trees and 

in trees weakened by root decay, or in unseasoned lumber, milled wood, wood 

placed in storage, and wood in use. Buprestid larvae are easily recognized by a 

greatly expanded head and thorax and a long, slender abdomen. 

The prevention of fire scars and other injuries to standing trees and the prompt 

utilization of diseased and felled trees can greatly reduce buprestid damage.

Figure 87. Flat-headed fir borer gallery 

characteristically packed with boring 

material.

Wood Borers
92

Flat-Headed Fir Borer

Coleoptera: Buprestidae

Melanophila drummondi (Kirby)

Hosts: Western hemlock. 

Distribution: This borer has caused severe, but localized, damage on western 

hemlock in Southeast Alaska. In the late 1960s, periodic flooding of western 

hemlock stands on the Salmon River near Hyder brought about a general 

decline in stand health. Samples taken at tree diameter contained as many as 

twelve larvae per 90 cm2

 of bark surface. Salvage logging was employed as a 

suppression measure. 

Identification: Adults are approximately 1.3 cm long and are metallic bronze 

or black with an iridescent sheen. Larvae are creamy white grubs with thorax 

and head greatly expanded and abdomen long and slender. Buprestid galleries 

differ from those of round-headed borers by being packed tightly with fine, 

dark excrement and wood particles. 

Damage: Attacks damaged or weakened trees. 

Remarks: Little is known concerning the biology of this insect in Alaska. 

Investigations into the host selection behavior of M. drummondi have dem‐

onstrated that adults are attracted to acetone and to a variety of substances 

associated with conifers including terpenes, scolytid pheromones and ethanol. 

M. drummondi overwinters in the larval stage within the host bark.

References: 43, 91, 209

Figure 88. Adult Melanophila 

drummondi.

Wood Borers
93

Bronze Birch Borer

Coleoptera: Buprestidae

Agrilus anxius Gory

Hosts: Aspen and Alaska birch. 

Distribution: Interior Alaska. 

Identification: Adults are olivaceous brown-black, approximately 1.3 cm 

long. Larval galleries are winding, about 6 mm wide and always tightly packed 

with boring dust. 

Damage: Attacks confined to individual ornamental trees, trees in open stands 

or exposed branches in fully stocked and stagnating stands; repeated attacks 

can reduce host tree vigor until death. 

Remarks: Adults emerge in late spring and summer and select sunny portions 

of trees for egg laying. Eggs are deposited on the bark surface of branches and 

upper parts of trees, especially those on poor sites. Larvae leave the phloem 

region at intervals and bore into the sapwood to molt. Larvae pupate in the host 

bark in autumn. Adults may feed, upon emergence, on host foliage. There is 

only one generation per year in over mature, slow growing trees.

Silvicultural measures are the most practical to suppress A. anxius infesta‐

tions. The best way to avoid attack is to maintain stands as healthy as possible. 

If birch regeneration is considered, only good sites should be utilized. Care 

should be taken not to leave host material directly exposed to the sun, as A. 

anxius prefers sunny locations for oviposition sites. To avoid vulnerability 

to exposure, stands should be clearcut or by cutting in groups, maintaining 

adequate shading for the remaining trees. 

References: 3, 86, 142, 257

Figure 89. Stem swellings, an 

indication of bronze birch borer 

activity.

Wood Borers
94

Other Alaska Buprestidae

Melanophila fulvoguttata (Harris)

Chrysobothris trinervia (Kby.)

Buprestis nuttalli (Kby.)

Hosts: White spruce. 

Distribution: Interior Alaska. 

References: 79

Figure 90. Flat-headed borer, Chrysobothris trinervia.

Figure 91. Melanophila fulvoguttata adult.

Wood Borers
95

Ambrosia Beetles

Ambrosia beetles are important pests of forest products because they riddle 

the sapwood and heartwood of unseasoned logs and poles. The entrance holes 

and small larval galleries are inoculated with dark brown or black stain fungi. 

Ambrosia beetles do not feed directly on the host tree, but obtain nutrients that 

have already been processed by the introduced fungi. Each ambrosia beetle 

species has a close symbiotic relation with a specific wood staining fungus. 

The beetles have specialized structures, mycangia, used for transporting the 

fungus from one host to another. 

The living requirements are very exacting for ambrosia beetles; unseasoned 

wood is suitable for attack whereas dried seasoned lumber is immune to 

attack. Damage is usually greatest where mild winters allow favorable tem‐

peratures and moisture conditions for extended periods of beetle activity. 

Suppression of ambrosia beetles is a matter of prevention. Logs, which are 

cut in the summer or fall, should be removed from the woods as quickly as 

possible and either placed in fresh water or processed at the mill. Prompt use 

of timber is about the only satisfactory solution for preventing ambrosia beetle 

damage.

Figure 92. Ambrosia beetle adult. Figure 93. Ambrosia beetle gallery; note 

staining.

Wood Borers
96

Ambrosia Beetles

Coleoptera: Curculionidae, Scolytinae

Trypodendron lineatum (Olivier), T. betulae Swaine

T. retusum (LeConte)

Hosts: Western hemlock, Sitka, Lutz and white spruce, yellow-cedar, birch, 

and aspen, depending on ambrosia beetle species. 

Distribution: Southeast, South-central, and Interior Alaska. 

Identification: Adults are small, stubby, dark beetles with a smooth, shiny 

body often with lighter colored longitudinal stripes. 

Damage: Sapwood and heartwood of unseasoned logs and poles are riddled 

with larval galleries. Symbiotic fungi produce a brown to black stain in and 

around the larval galleries. Fortunately, most of the damage is confined to 

the sapwood, but galleries may extend into the heartwood. Ambrosia beetle 

damage is difficult to eliminate because populations breed in stumps, fallen 

trees, and trees whose tops are broken from ice and snow. 

Remarks: T. lineatum adults overwinter in the litter on the forest floor. In the 

spring females select host material and initiate boring. Additional attacks are 

promoted by an aggregating pheromone. Galleries penetrate directly into the 

wood a short distance before branching into one of three egg galleries where 

adults then lay eggs. After the eggs hatch, the larvae enlarge these niches into 

larval cradles, and feed on ambrosia fungi introduced by the parent adults. In 

late summer, the brood matures, and adults emerge and disperse to hibernation 

sites in the litter on the forest floor. When they emerge and attack in the spring, 

striped ambrosia beetles show the strongest preference for logs cut in the 

previous fall and winter (Oct. through Feb.). Research conducted in Washing‐

ton indicates buildup of ethanol in freshly cut trees in the winter makes them 

highly attractive to ambrosia beetles. In Southeast Alaska, material felled after 

March will probably not be attacked that year, but will be susceptible to infes‐

tation in the following year if it is still on the ground.

References: 31, 41, 53, 79, 91, 93

Wood Borers
97

Clearwing Birch Borer

Lepidoptera: Sesiidae

Synanthedon culiciformis (L.)

Hosts: Birch

Distribution: South-central and Interior Alaska

Identification: Adult borers are day-flying moths which mimic bees and 

wasps in their coloration. They have narrow interlocking wings that are usu‐

ally transparent and un-scaled. Larvae are naked and ivory white, except for 

brownish markings on the thorax.

Damage: Damage to infested trees occurs in several ways. First, the destruc‐

tion of phloem by larval feeding can seriously reduce the tree’s ability to trans‐

port nutrients. Second, the tree becomes stressed and is more susceptible to 

additional insect and disease attacks. Wounds that are infested and re-infested 

do not heal, and provide entries for decay-causing fungi. Trees that have been 

infested for consecutive years are quite susceptible to stem breakage.

Figure 94. Clearwing birch borer larva.

Wood Borers
98

Figure 95. Clearwing birch borer adult.

Remarks: Adult clearwing borers fly in late spring through midsummer and 

are most active during the warmer daylight hours. Clearwing moths rarely 

injure healthy trees. When birch, however, is used as landscape trees, envi‐

ronmental stress factors such as soil compaction, moisture deficiency, and 

wounding can weaken them. Such trees are more susceptible to borer attack. 

Adults are attracted to fresh wounds near the base of the tree. Eggs are laid 

singly near these wounds. Young larvae immediately bore through the bark 

and begin feeding on the phloem tissue. Larvae continue feeding throughout 

the summer and hibernate beneath the bark through the winter. The following 

spring, larvae transform into adult moths. Wounded areas can be re-infested in 

successive years resulting in almost complete girdling of the tree.

References: 73, 139, 207

Wood Borers
99

Ghost Moths

Lepidoptera: Hepialidae

Sthenopsis quadriguttatus Grote

Hosts: Black cottonwood, alder, aspen and willow.

Distribution: Throughout South-central and Southeast Alaska, less common 

in the Interior.

Identification: The adult moth is very large (35–100 mm wingspan), brown‐

ish tan, and heavy bodied. Forewings are mottled with tan, brown, and orange, 

with one or two silver spots at base of cell. Adults are in flight from late-June 

to mid-August. Moths fly at dusk, swiftly and close to the ground. Eggs are 

smooth and unornamented. 

Figure 96. Ghost moth larva.

Figure 97. Ghost moth adult.

Wood Borers
100

Larvae are unornamented, cream colored with a reddish brown head and at 

maturity reach a size of 57 mm long. 

Damage: Ghost moths have only been found to attack small diameter (<8 cm) 

shrubs and regeneration. Larval burrowing in the basal area of the tree trunk 

and lower roots causes heavy decline in tree growth and usually results in 

death of the host.

Remarks: One-half to 2 hectare areas of cottonwood and alder mortality have 

been observed in riparian zones bordering the Lowe River near Valdez. Almost 

every small tree and shrub has been killed by larval mining of the phloem and 

xylem. Larvae burrow in the xylem along the long axis, usually into the center 

of the roots. Pupation occurs within the larval galleries. Larvae take 1 to 2 

years to develop.

References: 73, 229

Wood Borers
101

Wood Wasps 

Hymenoptera: Siricidae

Wood boring wasps or horntails are responsible for more damage than is 

usually ascribed to them. Wood wasps are especially abundant in fire killed 

forests. Trees killed by spring fires are more susceptible to attack. These borers 

may continue to work in sawed lumber taken from infested logs. Kiln drying 

usually kills larvae in sawed material. Fresh water treatments of saw logs and 

prompt utilization of are the best ways to prevent damage. 

Figure 98. Wood wasp ovipositing in white spruce, 

Urocerus gigas flavicornis.

Wood Borers
102

Horntails

Hymenoptera: Siricidae

Urocerus gigas flavicornis (F.), Sirex juvencus (L.), S. cyaneus F.,

Xeris spectrum (L.)

Hosts: Sitka, white, Lutz and black spruce, firs, and yellow-cedar (S. juvencus). 

Distribution: Throughout Alaska. 

Identification: The most common siricid, Urocerus, is a menacing looking, 

but stingless, thick-bodied, black and yellow wasp (Fig. 98). The female bears 

a hornlike ovipositor sheath projecting beyond the abdomen. The female 

inserts her ovipositor through the bark and deposits from one to three eggs. 

The larvae are white, legless grubs, cylindrical in form with a dark spine on the 

end of the abdomen. 

Damage: Attacks weakened or fire damaged trees, downed timber, or saw 

logs.

Remarks: Larvae construct round galleries in cross section, which penetrate 

into the wood. The galleries increase in size as the larvae mature. Horntail 

larvae consume wood that passes through their digestive tract and is packed 

tightly behind them. As with most siricid species, the larvae require from one 

to two seasons to complete development. The larvae construct pupal chambers 

in the outside layers of the sapwood. Pupal chambers are usually constructed 

on the upper side of logs. 

References: 73, 79, 85, 153

Figure 99. Horntail larva.

Wood Borers
103

Cone and Seed Insects

Cone and seed insects are relatively unimportant economically in a natural 

forest. The amount of seed produced by forest trees under natural conditions 

usually far exceeds the number of seeds destroyed by these insects. When 

good seed years occur in succession, cone and seed insects may build up to 

exceptionally high numbers. Consequently, the seed crop produced the second 

year may be almost completely destroyed (86, 153). In some seasons, insects 

and red squirrels may destroy all the spruce seed in certain localities. 

Destruction of forest seeds may be caused by insects that feed on buds, flow‐

ers, or immature cones, as well as by insects that actually destroy seeds. In 

many cases, the cones show no outward sign of damage, but the seeds may 

be infested. Many of the insects (budworms and coneworms) that feed upon 

buds and green tips also attack immature cones indirectly. The most injurious 

groups of cone and seed insects in Alaska are the seed moths and coneworms 

(Lepidoptera), seed worms and midges (Diptera), and true bugs (Hemiptera). 

In Alaska, the true bugs feed exclusively on birch, alder, and aspen seeds. The 

other species feed on spruce and hemlock cones and seeds. 

To date, few seed and cone insects have been associated with Alaska coni‐

fers, particularly in Southeast and South-central Alaska although Dioryctria

reniculelloides are known to attack Sitka, white and Lutz spruce cones heavily 

during good cone crop years.

Seven species of insects injurious to white spruce cones and seeds near Fair‐

banks were identified: Spruce Coneworm, Dioryctria reniculelloides; Spruce 

seed chalcid, Megastigmus piceae Felt; Spruce cone-axis midge, Dasineura 

rachiphaga Tripp; Gall midge, Phytophaga carpophaga Tripp; and cone mag‐

gots, Hylemia sp.

Cone and Seed Insects
104

Spruce Coneworm

Lepidoptera: Pyralidae

Dioryctria reniculelloides Mutuura and Munroe

Hosts: White, Lutz, and Sitka Spruce

Distribution: Principally in Interior and South-central Alaska.

Identification: The forewings of adults are bluish gray with zigzag darker 

cross markings. The hindwings are dusky white with darker borders. Adult 

wingspan is about 25 mm. Eggs are creamy white, turning cinnamon before 

hatching and are 1.0 by 0.7 mm. Mature larvae are 17 to 20 mm long, naked, 

and greenish red to amber brown above and light colored below.

Damage: First instars mine one or two needles. Larger larvae mine and attack 

spruce cones. Up to 100% cone mortality can occur. They also mine expand‐

ing buds and shoots. Infested cones and surrounding shoots are enveloped in 

coarse frass and webbing; severely infested cones are hollowed out. Damage 

can be confused with the spruce budworm and many times both insects are 

present on the same host during outbreak conditions.

Remarks: There is usually one generation per year. Eggs are deposited in 

bark cracks and fissures of stems, and on twigs and needles. In the early 

1990s, a defoliator outbreak was aerially detected along the Tanana and Yukon 

Rivers from Fairbanks to Ruby and encompassed more than 75,000 hectares. 

This outbreak was originally attributed to defoliation by the eastern spruce 

budworm, Choristoneura fumiferana. It was later determined that at least 50% 

of the damage was do to D. reniculelloides.

References: 73, 243, 246

Figure 100. Spruce coneworm larva.

Cone and Seed Insects
105

Spruce Seed Moth

Lepidoptera: Tortricidae

Cydia youngana (Kearfott)

Hosts: Sitka, Lutz, and white spruce, western hemlock. 

Distribution: Distributed throughout Alaska. Damage to spruce cones can 

exceed 300 percent. 

Identification: Adult insects are small, inconspicuous moths. Last instars are 

about 1.4 cm long. 

Damage: Larvae bore into the cone scales and feed from seed to seed. 

Remarks: Adults emerge from infested cones from May to June and oviposit 

on young cones. The eggs hatch about mid-June and each young larva crawls 

to the base of a cone scale to enter a seed. The larvae develop through four 

instars, feeding from seed to seed. Frass is packed in the tip of the gallery and 

in the mined seed. Usually only one larva reaches maturity in a single cone. 

An exit hole is made near the base of the cone, attended by a short, silk tube 

leading to the outside between the cone scales. This tube, which is made just 

before pupation in the fall, is diagnostic for this insect and is the only evidence 

of cone attack. The last instar overwinters in the cone. Pupation occurs the 

following May. There is usually one generation per year, but generations may 

overlap. 

References: 9, 103, 104, 275

Figure 101. Spruce seed moth larva.

Cone and Seed Insects
106

Spruce Cone-Axis and Gall Midges

Diptera: Cecidomyiidae

Dasineura rachiphaga Tripp, D. canadensis Felt

Hosts: White and Lutz spruce. 

Distribution: South-central and Interior Alaska. 

Identification: Adults are small, dark midges approximately 3 mm long. The 

mature larva is yellow. 

Damage: Larvae burrow in and around the cone-axis and indirectly damage 

the seed. 

Remarks: Little information concerning these species has been collected in 

Alaska. In British Columbia, D. rachiphaga is probably the most abundant 

insect in white spruce cones. The larvae burrow in and around the cone-axis. 

Since the larvae do not feed on or adjacent to the seeds, they do not damage 

them directly. D. canadensis is usually secondary in importance. Each larva 

creates a small gall in cone scales. This species causes little, if any damage to 

spruce seed. 

References: 104, 258

Cone and Seed Insects
107

Spruce Cone Maggot

Diptera: Anthomyiidae

Hylemia sp.

Hosts: Mountain hemlock, Sitka, white, Lutz, and black spruce. 

Distribution: Throughout Alaska. 

Identification: Adult flies are shiny black and approximately 6 mm long. The 

larvae (maggots) are white, about 8 mm long, having two large, black hooks 

on the head. 

Damage: Larvae consume seed. 

Remarks: Adults emerge from pupal overwintering sites in forest litter. Eggs 

are deposited between cone scales and maggots tunnel about the radius, eating 

through the scale bases and consuming the seed. After three weeks of feeding, 

the larvae emerge from the cone and drop to the ground where they overwinter 

as pupae. 

There is very little evidence of damage on infested cones. Usually one maggot 

completes development in each infested cone and may destroy up to 50 per‐

cent of the seed. 

References: 104, 153, 258

Figure 102. Spruce cone maggot damage.

Cone and Seed Insects
108

Yellow-cedar Gall Midge

Diptera: Cecidomyiidae

Chamaediplosis nootkatensis Gagne and Duncan

Hosts: Yellow-cedar 

Distribution: Southeast Alaska. 

Identification: Adults are small dark midges. The mature larva is orange. 

Damage: Larvae burrow in the tips of branches. Small galls are formed; each 

gall contains one larva, but sometimes two, or rarely three. 

Remarks: As for the spruce gall midge, little is known about the yellow-cedar 

gall midge. Infested trees are usually trees that have been planted in residential 

settings or seed orchards. Only a small percentage of the buds are affected. 

Damage is usually restricted to low elevations. 

References: 103, 258

Cone and Seed Insects
109

Insect Pests of Wood Products

To date, there have been few problems with insect pests of wood products in 

Alaska. In the southern latitudes wood products insects cause tremendous 

losses. It has been estimated that the loss from these insects is about 1–5 

percent of the annual cut. However, climatic conditions effectively bar many 

of these wood destroyers from the more northerly latitudes. Only 13 species 

of insects have been associated with wood products in Alaska, and few have 

caused structural damage to wooden buildings. Some woodborers have previ‐

ously been discussed, others are described below.

Insects of wood products either attack moist or dry seasoned wood (85). Those 

insects that attack moist, seasoned wood are usually symbiotically associated 

with protozoa, fungi, and bacteria that aid the insects in the digestion of cel‐

lulose and lignin. 

Some of these insects do not obtain their food from the wood. They tunnel into 

the wood to secure a sheltered base for foraging expeditions and a nursery for 

the young. Those insects attacking dry, seasoned wood also live in a symbiotic 

relationship with other microorganisms. These insects can breed successfully 

in wood with water content as low as six percent. 

The suppression of insects injurious to forest products is largely a matter of 

damage prevention. Kiln dried lumber is more or less resistant to insect attack, 

but a few species attack kiln dried material.

Figure 103. Carpenter ants: A. worker; B. king.

Insect Pests of Wood Products
110

Carpenter Ants

Hymenoptera: Formicidae

Camponotus herculeanus (L.)

Hosts: White and Lutz spruce.

Distribution: Throughout Alaska.

Identification: Ants have elbowed antennae, large heads with constrictions 

between the thorax and head, and the thorax and abdomen. When wings are 

present, they are translucent with prominent venation. The adult carpenter 

ant is shiny black and large. There are three labor castes: (1) queens, 15–20 

mm long; (2) kings, 10 mm long; and (3) workers, 6–10 mm long, which are 

sexually imperfect females. Only the queens and kings have wings. The egg is 

elongate, translucent white, and gourd-shaped. The pupae are creamy-white in 

papery, light brown cocoons.

Damage: In the northern temperate zones, carpenter ants can cause extensive 

structural damage to buildings. These ants build their nests in several types of 

wood. They attack moist heartwood of living trees, or they hollow out logs, 

house timbers, structural wood or other soft, wood materials that are wet or 

moist. In Alaska, carpenter ants damage standing white spruce and house 

logs. Carpenter ants tunnel into wood for shelter and brood rearing, but do not 

eat the wood. They forage from these shelters and consume both animal and 

vegetable material. 

Figure 104. Carpenter ant worker.

Insect Pests of Wood Products
111

Remarks: Males and females swarm and mate in May and June. After this 

mating flight, females either reestablish an old colony or establish a new nest. 

The young queen seeks out a small cavity in a tree or timber. She seals herself 

in, deposits her eggs, and does not feed until her first brood is mature. The 

young workers feed the queen and cut parallel, concentric galleries in a vertical 

direction throughout the wood.

The presence of carpenter ants can be detected by piles of “sawdust” at the 

base of posts, along sills, or elsewhere. Unused nest openings are sometimes 

sealed with plugs of wood. Carpenter ants do their greatest economic damage 

to houses where wood timbers are in contact with the ground. Prevention is the 

best control. Moist wood is attractive; so measures to prevent wood in struc‐

tures from becoming wet are very important. Building sites and adjacent areas 

should be cleared of stumps and partially decomposed logs. Buildings should 

be placed on concrete or masonry foundations or on treated timbers. This 

will greatly reduce attack by carpenter ants. Lumber and debris in basements 

is attractive to carpenter ants and may provide nesting sites. Badly damaged 

timbers may need replacement. Suppression measures may need to be taken if 

ants are foraging, especially during the winter months, within a house, or other 

structure.

References: 86, 197

Figure 105. Carpenter ant damage.

Insect Pests of Wood Products
112

Carpenter Bees

Hymenoptera: Xylocopidae

Xylocopa sp.

Hosts: White, Lutz, and black spruce. 

Distribution: South-central and Interior Alaska.

Identification: Carpenter bee adults are 1.5–2.5 cm long, robust, and resemble 

bumblebees. Females are greenish-black; males are often yellow with pale 

hairs. Larvae are typical hymenopteran grubs; legless, head globular with 

small mouthparts, and thoracic segments smaller than those of the abdomen. 

Pupae are robust, pale, and always found inside silken, leathery cocoons.

Damage: Carpenter bees, like the carpenter ants, cause structural weakening 

in house timbers where their galleries are concentrated. Carpenter bees have 

been reported to attack and burrow into wood houses and other wood struc‐

tures in Alaska. Often, carpenter bees merely take over the galleries of other 

wood-boring insects. 

Remarks: Adults emerge in the spring, and after mating, the females disperse 

and burrow into wood that is not eaten, but discarded. Eggs are deposited and 

larvae are fed pollen and nectar collected by the adults. Tunnels penetrate 

inwards for a few centimeters or so and then turn and parallel with the wood 

grain. Galleries are divided into individual cells, about 2 cm long, by means 

of cross walls that consist of cemented, compacted, chewed wood. There is 

one larva per cell. New adults escape through entrance holes constructed by 

parents. There is usually one generation per year.

Controls are seldom needed, but coating the wood with varnish or paint is 

effective in preventing attacks.

References: 3, 73

Figure 106. Carpenter bee: A. adult; B. chambered 

galleries.

Insect Pests of Wood Products
113

Powder Post Beetles

Coleoptera: Lyctidae

Lyctus cavicollis LeConte

Hosts: Sapwood of seasoned hardwoods with moisture content between 6 and 

30 percent.

Distribution: Throughout Alaska.

Identification: Beetles are 0.6 cm long, with a flattened, elongated body, and 

are brown to black. Larvae are small, whitish, cylindrical grubs with three-seg‐

mented pairs of thoracic legs.

Damage: Lyctus are the most injurious of the powder post beetles in North 

America. Severely infested wood is reduced nearly to powder, but remains 

somewhat covered by nearly intact but, holey, exterior shell. Furniture and 

hardwood lumber dealers often discover these pests. Axe and shovel handles 

may be destroyed, and infested hardwood flooring may be installed without 

knowledge of the beetles’ presence. When adults emerge, the wood exhibits 

numerous small, round exit holes. In Alaska, museum displays of wooden 

snowshoes and other wood products have been infested by powder post 

beetles.

Figure 107. Adult 

powder post beetle.

Insect Pests of Wood Products
114

Remarks: Mated females deposit eggs in wood pores approximately 0.3 cm 

deep, and new larvae bore through the wood in all directions. Overwintering 

larvae pupate at the end of larval galleries. Adults emerge through round, 0.2 

cm exit holes. There is usually one generation per year, but two years or more 

maybe required to complete development under unfavorable conditions. 

Preventive measures are the best control. Protecting susceptible wood by paint‐

ing with linseed oil, varnish, or paint effectively prevents oviposition. Stored 

heartwood and sapwood lumber should be separated where possible, and 

inspected frequently. Infestations can be detected by the small quantities of 

fine boring dust on and in the vicinity of the infested material. 

References: 3, 73, 86

Insect Pests of Wood Products
115

Parts of an Insect

Figure 108. External insect morphology: A. side view of a bark 

beetle with wings and wing covers removed; B. dorsal view. Legend: 

a. head, b. compound eye, c. antenna, d. mouthparts, e. pronotum, f. 

femur, g. tibia, h. tarsus, i. spiracles, j. elytra (wing covers), and k. 

membranous wings.
116

Index to Insects by Host 

Plants

Alder (Alnus spp.)

 Defoliators

Leaf Rollers (Epinotia solandriana)......................................................................30

Western Hemlock Looper (Lambdina fiscellaria lugubrosa)..............................32

Spear-Marked Black Moth (Rheumaptera hastata).............................................34

Spotted Tussock Moth (Lophocampa maculata).................................................41

Leaf Blotch Miner (Phyllonorycter nipigon)........................................................42

Striped Alder Sawfly (Hemichroa crocea)............................................................50

Alder Woolly Sawfly (Eriocampa ovata)..........................................................51

Leaf Beetles (Chrysomela sp.)...........................................................................52

 Wood Borers

Ghost Moths (Sthenopsis sp.).................................................................................99

Aspen, Quaking (Populus tremuloides Michx.)

 Defoliators

Large Aspen Tortrix (Choristoneura conflictana)................................................28

Leaf Rollers (Epinotia solandriana)......................................................................30

Aspen Leaf Miner (Phyllocnistis populiella)........................................................42

Leaf Blotch Miner (Phyllonorycter nipigon)........................................................42

Leaf Beetles (Chrysomela sp.)...............................................................................52

 Sap Sucking Insects

Spruce Gall Aphids (Adelges sp. and Pineus sp.)..................................................60

Eriophyid Mites.....................................................................................................70

 Wood Borers

Bronze Birch Borer (Agrilus anxius).....................................................................93

Ambrosia beetle (Trypodendron retusum)............................................................96

Birch, Alaska (Betula neoalaskana Sargent)

 Defoliators

Leaf Rollers (Epinotia solandriana)......................................................................30

Spear-Marked Black Moth (Rheumaptera hastata).............................................34

Birch Leaf Miner (Profenusa thomsoni, Fenusa pusilla,

 Heterarthrus nemoratus).................................................................................45

Leaf Beetles (Chrysomela sp.)...............................................................................52
117

 Sap Sucking Insects

Birch Aphid (Euceraphis betulae).........................................................................65

 Wood Borers

Bronze Birch Borer (Agrilus anxius).....................................................................93

Ambrosia beetles (Trypodendron betulae)............................................................96

Clearwing Birch Borer (Synanthedon culiciformis).......................................97

 Wood Products Insects 

Carpenter Ants (Camponotus herculeanus)........................................................110

Cedar, Yellow- (Chamaecyparis nootkatensis (D. Don) Spach)

 Defoliators

Western Hemlock Looper (Lambdina fiscellaria lugubrosa)..............................32

Green-Striped Forest Looper (Melanolophia imitata).........................................36

Saddle-Backed Looper (Ectropis crepuscularia).................................................37

 Bark Beetles

Cedar Bark Beetle (Phloeosinus cupressi, P. sequoiae).......................................82

 Wood Borers

Ambrosia Beetles (Trypodendron lineatum)........................................................96

Horntail (Sirex juvencus).....................................................................................102

 Seed and Cone Insects

Yellow-cedar Gall Midge (Chamaediplosis sp.)................................................108

Cedar, Western Red (Thuja plicata Donn)

 Defoliators

Western Hemlock Looper (Lambdina fiscellaria lugubrosa)..............................32

Green-Striped Forest Looper (Melanolophia imitata).........................................36

Saddle-Backed Looper (Ectropis crepuscularia).................................................37

 Bark Beetles

Cedar Bark Beetle (Phloeosinus cupressi, P. sequoiae).......................................82

Cottonwood, Black (Populus trichocarpa Torr. & Gray)

 Defoliators

Leaf Roller (Epinotia solandriana).......................................................................30

Leaf Blotch Miner (Lyonetia sp.)...........................................................................42

Leaf Beetles (Chrysomela sp.)...............................................................................52

 Wood Borers

Ghost Moths (Sthenopsis sp.).................................................................................99

Fir, Subalpine (Abies lasiocarpa (Hook.) Nutt.)

 Bark Beetles

Dryocoetes sp........................................................................................................84
118

Hemlock, Mountain (Tsuga mertensiana (Bong.) Carr.)

 Defoliators

Black-headed Budworm (Acleris gloverana).......................................................24

Hemlock Sawfly (Neodiprion tsugae)..................................................................46

 Seed and Cone Insects

Spruce Cone Maggot (Hylemia sp.)....................................................................107

Hemlock, Western (Tsuga heterophylla (Raf.) Sarg.)

 Defoliators

Black-Headed Budworm (Acleris gloverana)......................................................24

Western Hemlock Looper (Lambdina fiscellaria lugubrosa)..............................32

Green-Striped Forest Looper (Melanolophia imitata).........................................36

Saddle-Backed Looper (Ectropis crepuscularia).................................................37

Hemlock Sawfly (Neodiprion tsugae)...................................................................46

 Sap Sucking Insects

Hemlock Woolly Aphid (Adelges tsugae).............................................................62

 Bark Beetles

Hemlock Hylesinus (Pseudohylesinus tsugae)....................................................81

Dryocoetes sp........................................................................................................84

 Wood Borers

White-Spotted Sawyer (Monochamus scutellatus)..............................................88

Flat-Headed Fir Borer (Melanophila drummondi)...............................................92

Ambrosia Beetles (Trypodendron lineatum)........................................................96

 Seed and Cone Insects

Spruce Seed Moth (Cydia youngana).................................................................105

Larch, Eastern (Tamarack) (Larix laricina (DuRoi) K. Koch)

 Defoliators

Larch Sawfly (Pristiphora erichsonii)...................................................................48

 Bud and Shoot Insects

Larch Budmoth (Zeiraphera sp.)...........................................................................55

 Bark Beetles

Larch Beetle (Dendroctonus simplex)...................................................................77

Pine, Lodgepole (Pinus contorta Dougl.)

 Bark Beetles

Engraver (Ips pini)..................................................................................................78

Four-Eyed Bark Beetle (Polygraphus sp.).............................................................83

Dryocoetes sp........................................................................................................84
119

Poplar, Balsam (Populus balsamifera L.)

 Defoliators

Aspen Leaf Miner (Phyllocnistis populiella)........................................................42

Leaf Blotch Miner (Phyllonorcyter nipigon & Lyonetia sp.)...............................42

Leaf Beetles (Chrysomela sp.)...............................................................................52

Spruce, Black (Picea mariana (Mill.) B.S.P.)

 Bud and Shoot Insects

Spruce Bud Midge (Rhabdophaga sp.)................................................................54

 Bark Beetles

Spruce Beetle (Dendroctonus rufipennis).............................................................73

Engravers (Ips sp.)..................................................................................................78

Four-Eyed Bark Beetles (Polygraphus sp.)...........................................................83

 Wood Borers

White-Spotted Sawyer (Monochamus scutellatus)..............................................88

 Seed and Cone Insects

Spruce Cone Maggot (Hylemia sp.)..............................................................107

 Wood Products Pests

Carpenter Bees (Xylocopa sp.).............................................................................112

Spruce, Sitka (Picea sitchensis (Bong.) Carr.)

 Defoliators

Black-Headed Budworm (Acleris gloverana)......................................................24

Spruce Budworm (Choristoneura sp.)..................................................................26

Western Hemlock Looper (Lambdina fiscellaria lugubrosa)..............................32

 Bud and Shoot Insects

Spruce Bud Midge (Rhabdophaga swainei).......................................................54

Spruce Budmoth (Zeiraphera sp.).........................................................................55

 Sap Sucking Insects

Spruce Aphid (Elatobium abietinum)...................................................................57

Giant Conifer Aphid (Cinara sp.)...........................................................................59

Spruce Gall Aphid (Adelges sp. & Pineus sp.)......................................................60

Woolly Aphid (Adelges sp. & Pineus sp.)..............................................................62

Spruce Bud Scale (Physokermes piceae)..............................................................64

Spittlebug (Aphrophora sp.)..................................................................................68

 Bark Beetles

Spruce Beetle (Dendroctonus rufipennis).............................................................73

Engravers (Ips sp.)..................................................................................................78

Four-Eyed Bark Beetles (Polygraphus sp.)...........................................................83

Dryocoetes sp........................................................................................................84
120

 Wood Borers

Ambrosia Beetles (Trypodendron lineatum)........................................................96

 Seed and Cone Insects

Spruce Seed Moth (Cydia youngana)................................................................105

Spruce Cone Maggot (Hylemia sp.)...................................................................107

Spruce, White (Picea glauca (Moench) Voss)

 Defoliators

Western Black-Headed Budworm (Acleris gloverana)......................................24

Spruce Budworm (Choristoneura sp.).................................................................26

 Bud and Shoot Insects

Spruce Bud Midge (Rhabdophaga swainei)........................................................54

Spruce Budmoth (Zeiraphera sp.).........................................................................55

 Sap Sucking Insects

Spruce Aphid (Elatobium abietinum)....................................................................57

Giant Conifer Aphid (Cinara sp.)...........................................................................59

Spruce Gall Aphids (Adelges sp., Pineus sp.).......................................................60

Woolly Aphid (Adelges sp., Pineus sp.)................................................................62

Spruce Bud Scale (Physokermes piceae).............................................................64

 Bark Beetles

Spruce Beetle (Dendroctonus rufipennis)............................................................73

Engravers (Ips sp.)..................................................................................................78

Four-Eyed Bark Beetles (Polygraphus sp.)..........................................................83

Dryocoetes sp........................................................................................................84

 Wood Borers

White-Spotted Sawyer (Monochamus scutellatus).............................................88

Xylotrechus undulatus.........................................................................................89

Flat-Headed Woodborers (Melanophila fulvoguttata, Chrysobothris

 trinervia & Buprestis nuttalli)..........................................................................94

Ambrosia Beetle (Trypodendron lineatum)..........................................................96

Horntail (Urocerus gigas flavicornis, Sirex cyaneus, Xeris spectrum)............102

 Cone and Seed Insects

Spruce Coneworm (Dioryctria reniculelloides)................................................104

Spruce Seed Moth (Cydia youngana)................................................................105

Spruce Cone-Axis Midge (Dasineura rachiphaga).........................................106

Spruce Cone Gall Midge (Dasineura canadensis)...........................................106

Spruce Cone Maggot (Hylemia sp.)...................................................................107

 Wood Products Insects

Carpenter Ants (Camponotus herculeanus).......................................................110

Carpenter Bees (Xylocopa sp.).............................................................................112
121

Spruce, Lutz (Picea x lutzii Little)

 Defoliators

Black-Headed Budworm (Acleris gloverana)......................................................24

Spruce Budworm (Choristoneura sp.).................................................................26

 Bud and Shoot Insects

Spruce Bud Midge (Rhabdophaga sp.)................................................................54

Spruce Budmoth (Zeiraphera sp.)........................................................................55

 Sap Sucking Insects

Spruce Aphid (Elatobium abietinum)...................................................................57

Giant Conifer Aphid (Cinara sp.)...........................................................................59

Spruce Gall Aphids (Adelges sp. & Pineus sp.).....................................................60

Spruce Bud Scale (Physokermes piceae).............................................................64

 Bark Beetles

Spruce Beetle (Dendroctonus rufipennis)............................................................73

Engravers (Ips sp.).................................................................................................78

Four-Eyed Bark Beetles (Polygraphus sp.)..........................................................83

Dryocoetes sp.......................................................................................................84

 Wood Borers

White-Spotted Sawyer (Monochamus scutellatus).............................................88

Xylotrechus undulatus..........................................................................................89

Flat-Headed Woodborers (Melanophila fulvoguttata, Chrysobothris

 trinervia & Buprestis nuttalli)..........................................................................94

Ambrosia Beetle (Trypodendron lineatum).........................................................96

Horntail (Urocerus gigas flavicornis, Sirex cyaneus, & Xeris spectrum)......102

 Cone and Seed Insects

Spruce Coneworm (Dioryctria reniculelloides)................................................104

Spruce Seed Moth (Cydia youngana)................................................................105

Spruce Cone-Axis Midge (Dasineura rachiphaga)..........................................106

Spruce Cone Gall Midge (Dasineura canadensis)...........................................106

Spruce Cone Maggot (Hylemia sp.)...................................................................107

 Wood Products Insects

Carpenter Ants (Camponotus herculeanus).......................................................110

Carpenter Bees (Xylocopa sp.)............................................................................112

Willow (Salix sp.)

 Defoliators

Spear-Marked Black Moth (Rheumaptera hastata)............................................34

Mourning Cloak (Nymphalis antiopa).................................................................38

Willow Leaf Miner (Micrurapteryx salicifoliella).............................................43

Leaf Beetles (Chrysomela sp.)........................................................................52
122

 Bark Beetles

Willow Bark Beetle (Trypophloeus striatulus)...................................................85

 Wood Borers

Ghost Moths (Sthenopsis sp.)...........................................................................99
123

Diseases

Tree Diseases

Tree diseases in Alaskan forests can fundamentally change the ecosystem 

and lead to huge economic loss to the timber resource. But unlike typically 

dramatic insect outbreaks, diseases are often chronic and insidious and may go 

unnoticed. 

Most of the countless disease agents in Alaskan forests are fungi, and most of 

those do not seriously threaten the life of the tree or cause significant changes 

to the ecosystem. Diseases of leaves and needles are a good example; they dis‐

color trees but the attacks generally do not continue for long and infected trees 

usually recover. This type of disease is often only a problem if the appearance 

of the tree is important.

The tree diseases of greatest concern in Alaska are internal wood decays of live 

trees (heart rot, stem decay fungi), hemlock dwarf mistletoe and several root 

diseases. These are among the diseases that can kill trees or greatly influence 

tree growth, wood production, and ecological processes.

The amount of disease is usually related to the age of trees or the forest in 

general. Young forests that regenerate after clearcutting or natural disturbance 

generally are not seriously affected by disease although some pathogens, such 

as the needle fungi and root diseases mentioned above, may be present. But 

as forests age several diseases, particularly the heart rots, become much more 

abundant. These diseases progress slowly until they eventually begin to alter 

forest dynamics. In some cases diseases such as heart rots and root diseases 

influence stand development or plant succession by selectively killing trees or 

tree species. 

Without disturbance from logging or natural causes such as fire or wind‐

storms, forests can develop to an old-growth stage. Disease can help maintain 

old growth by killing trees in a scattered manner rather than catastrophically 

disturbing forests. Such is the case in Southeast Alaska, where large old trees 

are often killed by heart rots and dwarf mistletoe. The death of these dominant 

trees creates an opening in the forest, a “canopy gap,” where new trees can 

regenerate. 

A healthy forest is one that meets the goals of resource managers, which could 

mean very little or very abundant disease, depending on the management goals 

for that forest. Forests managed for wildlife habitat and resources other than 

wood can benefit from heart rot and dwarf mistletoe, diseases that contribute to 

structural and biological diversity. Where timber production is favored, these 
124

same diseases are detrimental to the timber resource and usually do not help 

meet management goals. Moderate disease levels may be the goal for forests 

managed to meet multiple resource objectives. Most tree diseases respond in a 

predictable way to harvest treatments and can be managed to particular levels 

with confidence.

Other Agents

The severe decline of yellow-cedar in Southeast Alaska does not appear to be 

caused by any biological agent, which means it may not be considered a true 

forest disease. Still, the effect on the ecosystems can be considerable, particu‐

larly changes in forest composition and plant succession that are a result of 

yellow-cedar mortality.

Animal damage is also a factor in the condition of Alaskan forests. By remov‐

ing the bark during feeding, porcupines can create large wounds, top kill, 

or completely kill trees. In several places in Southeast Alaska, brown bears 

frequently wound the lower bole of yellow-cedar trees, producing infection 

courts for wood decay fungi.

Other non-disease factors, such as hemlock fluting and injury from weather 

events, are also described.
125

Spruce Needle Rust

Chrysomyxa ledicola Lagerh.

Hosts: Sitka, white, and black spruce and Labrador tea

Distribution: Throughout Alaska on spruce where the ranges of spruce and 

Labrador tea (Ledum spp.) coincide.

Identification: A heterocyclic rust with one stage of its life cycle on spruce 

and the other on Labrador tea (Ledum spp.). Spores produced on Labrador tea 

infect current-year’s spruce needles. Pustules produced by the rust fungus are 

orange or yellow with dry spore deposits. The rust disease occurs on spruce 

only on boggy sites where the alternate hosts are found, but can occur solely 

Figure 109. Spruce needle rust.

Foliar Diseases
126

on Labrador tea outside the range of spruce. Spruce trees have a distinct 

orange tinge when the rust is fruiting on the needles in summer.

The closely related C. weirii Jacks. is microcyclic (no alternate host) and 

causes chlorotic (yellowing) bands on one-year-old needles of Sitka spruce 

where it fruits in early spring. This rust fungus is less damaging and conspicu‐

ous than C. ledicola. 

Injury: Causes a premature defoliation that could influence tree growth. Little 

damage usually occurs unless the tree is infected for several consecutive years. 

Remarks: Removal of alternate hosts in the vicinity of spruce or spraying 

with fungicides in the spring can reduce infestation to some extent but this is 

not often economically justified except for high value trees where appearance 

is important. Spruce nurseries should not be established in boggy areas with a 

history of spruce needle rust.

References: 29, 71, 126, 232, 244, 278

Figure 110. Spruce needle rust with current year’s needles 

infected.

Foliar Diseases
127

Figure 111. Labrador tea is 

the alternate host for spruce 

needle rust.

Figure 112. The closely-related 

Chrysomyxa weirii on one 

year old spruce needles.

Figure 113. Close-up of 

Chrysomyxa ledicola on an 

infected needle.

Foliar Diseases
128

Hemlock Needle Rust

Naohidemyces vaccinii (Wint.) Sato, Katsuy et Hiratsuka

(=Pucciniastrum vaccinii (Rab.) Joerst.)

(=Uraecium holwayi)

Hosts: Western hemlock and blueberry species.

Distribution: Southeast Alaska.

Identification: A heterocyclic rust with one stage on hemlock needles (rarely 

on cones) and the other stage on several species of blueberry (Vaccinium spp.). 

Another needle rust of western and mountain hemlocks, Melampsora epitea f. 

sp. tsugae, is also present in Alaska. Its alternate host is willow.

Current-year hemlock needles become infected from spores produced in 

pustules on blueberry leaf. Orange or yellow pustules form on the underside of 

hemlock needles. Infected needles turn yellow, but hemlocks are not usually 

heavily infected, thus branches have a scattering of yellow needles with most 

needles remaining uninfected and green. 

Injury: Infected needles turn yellow and die, but the incidence of the disease 

on hemlock needles is usually low. Infected needles are shed prematurely. 

Injury to infected trees is negligible, perhaps slightly reducing growth. 

Remarks: The generally low occurrence of this rust is surprising given the 

great abundance to western hemlock and blueberries in coastal Alaska. Control 

is not usually warranted, as injury to trees is typically very minor.

References: 1, 199, 232, 278

Figure 114. Hemlock needle rust on 

western hemlock. Figure 115. Pustules of the rust fungus 

on the underside of infected needles.

Foliar Diseases
129

Hardwood Leaf Rust

Melampsora epitea Thuem, M. medusae Thuem

Melampsoridium betulinum Kleb

Hosts: On willow: several races of M. epitea (alternative hosts: hemlock and 

true firs); on aspen and cottonwood: M. medusae (alternative hosts: true fir, 

spruce, hemlock, and pine); on birch: Melampsoridium betulinum.

Distribution: Hosts range in Alaska.

Identification: These rust fungi appear as orange or yellow spots on the upper 

or lower surfaces of live hardwood leaves. Some of these rust fungi alternate 

between hardwood and conifer hosts to complete the life cycle. Rust spores 

produced on hardwood leaves can alternate to either hardwoods or conifers , 

while rust spores produced on conifers can only infect the hardwood host. The 

rust fungi that do not require an alternative host can overwinter in buds and 

readily reinfect hardwood trees in successive years. 

Injury: Damage can be more important on conifer host. Hosts are not usually 

killed by leaf rust infestations, but trees may be prematurely defoliated or 

growth may be slowed if trees are heavily infected. Infected ornamental plants 

may become less attractive. 

Remarks: Each of these rust fungi infects a small range of hardwood hosts; 

therefore, planting resistant species or varieties on highly valued sites known 

to have rust problems can minimize losses.

References: 29, 71, 278

Figure 116. Rust pustules of Melampsora epitea.

Foliar Diseases
130

Cedar Leaf Blight

Didymascella thujina (Durand) Maire

(= Keithia thujina Durand)

Host: Western redcedar.

Distribution: Host range in Southeast Alaska.

Identification: The fungus produces small dark brown fruiting structures on 

the upper side of cedar foliage. Usually one to three spherical or oval structures 

are formed just under the epidermis. At maturity in summer, a flap of epider‐

mis is pushed aside when conditions are moist and the spores are forcibly 

ejected into the air. After spore discharge, the fruiting structure falls out and 

leaves a black cavity or hole in a dead brown foliage scale resembling an “exit 

hole” from insect feeding. Foliage on cedars severely infected first appears 

reddish and later gray.

Injury: Seedlings can be killed by the fungus. Older trees often have the lower 

crowns heavily infected, resulting in growth loss and a reduction of vigor. 

Remarks: This disease is very common on western redcedar in the forest and 

in ornamental trees, but does not cause mortality. Control is not necessary in 

the forest but may be accomplished by the use of fungicides in nurseries or for 

ornamental trees.

References: 4, 29, 71, 126

Figure 117. Scattered infection of cedar leaf blight on western 

redcedar.

Foliar Diseases
131

Spruce Needle Blight

Lirula macrospora (Hartig) Darker

Lophodermium picea (Fckl.) V. Hohn

Rhizosphaera pini (Corda) Maubl.

Hosts: Sitka, white, and black spruce.

Distribution: Host ranges in Alaska.

Identification: These three diseases occur on the needles of spruce. Fruiting 

bodies are small, black and elliptical for Lophodermium, black and elongated 

for Lirula, and microscopic and emerging from stoma for Rhizosphaera. All 

three occur along the underside of diseased needles.

Symptoms appear in needles one year old or older. Lirula actually makes its 

infection in spring on new needles as they emerge during bud break, but the 

infected needles do not show any symptoms for one year. For Lirula, infected 

needles turn a reddish-brown color in the spring one year after infection and 

become tan in color two years after infection. The elongated black fruiting 

body appears on the underside of these two-year-old tan needles and opens 

in spring to release its spores to infect new needles. Lophodermium may 

also infect new needles, but symptoms typically appear in older groups of 

adjacent needles. Infection could be systemic in twig tissue. Rhizosphaera is 

Figure 118. Spruce needle blight, Lirula macrospora, on Sitka spruce.

Foliar Diseases
132

Figure 119. Fruiting bodies of Lirula macrospora on twoyear-old spruce needles.

Figure 120. Lophodermium picea on spruce needles.

Foliar Diseases
133

less common than the other two pathogens and can only be identified using a 

microscope because the clear, bubble-like fruiting bodies are so small.

Injury: Fungi, such as these needle blight species, are not damaging to spruce 

trees unless there are several successive years of attack. Lirula is the most 

commonly observed of the three needle diseases. Outbreaks are triggered by 

weather patterns that usually do not repeat several years in a row; therefore, 

epidemic levels of these fungi do not typically occur. Given the microscopic 

shape of spores (extremely elongated), dispersal of Lirula and Lophodermium

spores may be by rain splash. Also, infections often take place in the lower, 

less important, portion of the crown. Infected trees are often localized; a few 

trees in an area may be heavily attacked while other nearby trees are nearly 

uninfected, suggesting a genetic disease resistance in spruce. 

Remarks: Lirula is the most common of these needle blight fungi, frequently 

attacking spruce in young-growth forests of coastal Alaska. Control is not usu‐

ally necessary, but fungicides have been shown to be effective if applied during 

or just after bud break when new needles are being exposed and the fungus is 

sporulating.

References: 29, 71, 107, 111, 126, 232

Figure 121. Rhizosphaera pini on older needles of Sitka spruce.

Foliar Diseases
134

Sirococcus Shoot Blight

Sirococcus tsugae (Rossman, Castlebury, D.F. Farr & Stanosz)

(=Sirococcus strobilinus (Dearn.) Petr.)

Hosts: Western hemlock, mountain hemlock, and occasionally Sitka spruce

Distribution: Southeast Alaska

Identification: This is a fungal disease of young lateral or terminal shoots. 

Initial infection occurs on juvenile needles, later growing into the developing 

shoots. Small cankers sometimes appear and stem growth is retarded on one 

side of the shoot causing it to bend into a characteristic hook shape. Death of 

the shoot or terminal leader follows and small black circular fruiting bodies 

Figure 122. Numerous dead shoots of western hemlock caused by 

Sirococcus tsugae.

Shoot Diseases
135

appear. Mature spores are disseminated by the splashing of water drops. 

Microscopically, the spores are distinctive in having a slight constriction at 

the single septum (crosswall). Development of the fungus is favored by high 

atmospheric moisture, mild temperatures, and low light intensities—conditions 

typical of dense young growth forests in Southeast Alaska.

Injury: Sirococcus causes a wilting and dieback of the shoot tips and occa‐

sionally seedling and sapling mortality. Mature trees suffer little damage. 

Growth reduction may occur on heavily infected trees. Ornamental mountain 

hemlock trees are often heavily infected and can die.

Remarks: The new species name, Sirococcus tsugae, is now formally 

described and applies to the species found in Alaska. The type specimen was 

collected from a mountain hemlock tree in the Mendenhall Valley near Juneau. 

Thinning may be the best management of the disease in younger stands since 

it changes high humidity levels that favor the pathogen; control is unnecessary 

in older stands. Fungicides are available for control in nurseries or for orna‐

mental trees. 

References: 69–71, 185, 196, 220, 232, 253, 274

Shoot Diseases
136

Yellow-cedar Shoot Blight

Apostrasseria sp.

Host: Yellow-cedar

Distribution: Southeast Alaska

Identification: Infection by this fungus causes dieback of branches or the 

terminal leader. The small black fruiting bodies of the causal fungus can be 

found in spring when infection has just killed shoot tissues. The disease is 

restricted to seedlings and saplings of yellow-cedar and has not been found in 

mature trees.

Injury: Shoots of seedlings and saplings are killed by Apostrasseria. Small 

seedlings are often killed by this pathogen. Infection of larger seedlings or sap‐

lings is serious when terminal leaders are killed; this can result in yellow-cedar 

not being competitive with surrounding vegetation. Injury may appear similar 

to spring frost damage.

Remarks: This fungus may limit the success of yellow-cedar regeneration, 

whether seedlings establish naturally or are planted. Browsing by deer and 

spring frost injury are generally more substantial threats, however. 

References: 106

Figure 123. Yellow-cedar shoot 

blight.

Shoot Diseases
137

Shepherd’s Crook 

Venturia macularis (Fr.:Fr.) E.Müller & Arx., V. populina (Vuill.) 

Frabic.

Host: On aspen: V. macularis; on balsam poplar: V. populina.

Distribution: Hosts range in Alaska.

Identification: Angular black spots are formed on leaves and twigs in spring 

and early summer. Infected leaves curl, turn black and die. The adjoining twigs 

then become withered, blackened and hooked at the tip. New shoots may be 

killed as they start to grow. Wet or damp weather favor these fungi, which 

remain dormant during hot dry summers. Trees with insect injury are more 

susceptible to infection.

Injury: V. macularis primarily causes stunting and malformation of terminal 

shoots of aspen seedlings and saplings. V. populina infects terminal and lateral 

shoots of balsam poplar. Mature trees suffer little damage. 

Remarks: Where practical, blighted twigs may be pruned on ornamental trees 

to help improve their appearance and reduce future infection. 

References: 34, 49, 71, 126, 128, 129

Figure 124. Sheperd’s crook on 

aspen.

Shoot Diseases
138

Hemlock Dwarf Mistletoe 

Arceuthobium tsugense (Rosendhal) G.N. Jones

Hosts: Western hemlock, Sitka spruce (uncommon), mountain hemlock (rare)

Distribution: Southeast Alaska, south of Haines

Identification: Dwarf mistletoe is caused by a small seed bearing plant. Only 

one species of dwarf mistletoe occurs in Alaska. The parasitic plants are small, 

leafless, and yellow-green or sometimes other colors. They are incapable of 

producing enough food for their own support and exist only as a parasite (i.e., 

obligate parasite) growing in twigs, branches, and boles of living trees. The 

“roots” of the dwarf mistletoe plant are endophytic (growing inside live plant 

tissues) and occur as feeding structures in the cambial area and sapwood of 

swollen tree tissues. The short aerial shoots (about 5 to 13 cm tall) are pro‐

duced solely for the purpose of reproduction. Female and male flowers occur 

on different dwarf mistletoe plants.

Sticky mistletoe seeds are forcibly discharged (up to 30 ft) from female plants 

in late summer or early autumn. Seeds that hit and attach to hemlock foliage or 

twigs over winter as seeds. Seeds removed from branches during winter may 

significantly reduce infection rates in Alaska. The next spring, seeds germinate 

and penetrate young twig tissue with an infection peg to begin infection. Twig 

swelling is the first symptom of mistletoe infection, and generally appears two 

years after infection. After 3 to 4 years, dwarf mistletoe shoots may emerge 

from the enlarged swelling and produce either male or female flowers. Female 

flowers are pollinated and produce the single-seeded fruits after another year 

Figure 125. A female plant of 

hemlock dwarf mistletoe with 

mature fruits.

Stem and Branch Diseases
139

to complete the life cycle. Inoculation studies in Alaska suggest that the life 

cycle may take longer to complete here than for the same disease further south. 

Endophytic roots (inside hemlock tissue) of dwarf mistletoe plants are viable 

for many years and may produce large swellings and many successive years 

of aerial shoots. Aerial shoots, flowers, and fruits occur on infections with 

adequate light, usually occuring high in tree crowns where they cannot be 

readily observed.

Figure 126. Western hemlock tree 

severely infected with hemlock dwarf 

mistletoe.

Figure 127. Swelling and aerial shoots of hemlock dwarf mistletoe 

on a small branch.

Stem and Branch Diseases
140

Injury: Dwarf mistletoe interferes with tree hormones causing increased 

growth in the hemlock tissues that are infected. Infections result in branch 

or twig swellings, large disfiguring burls on main bole infections, and most 

noticeably, witches’ brooms–portions of tree crowns with branch prolifera‐

tions. Witches’ brooms and swellings can adversely affect height and diam‐

eter growth, and also reduce tree vigor, which can make infected trees more 

susceptible to insects and other diseases. The degree of growth loss is directly 

correlated to the intensity of infection (the number and size of infections). 

Lightly infected trees have no measurable growth loss, but severely infected 

trees lose about 40% of their potential growth. Severely infected trees may 

die. Bole infections may reduce wood quality and frequently provide infection 

courts for wood decay, leading to significant heart rot.

Remarks: Hemlock dwarf mistletoe is one of the most important diseases 

of western hemlock in Alaska, infesting an estimated 405,000 hectares of 

forest land. It is more common at low elevations, another indication that snow 

may limit reproduction, overwintering of seeds, or infection. The disease is 

favored by small-scale disturbance (gap formation) that occurs in old-growth 

forests where mistletoe seeds can infect new trees that regenerate in small 

gaps. Clearcut logging of infected stands serves as a form of disease control. 

As an obligate parasite, dwarf mistletoe is killed and will not reproduce on 

hemlock slash or downed logs. Infected residual old-growth trees (left after 

logging), advanced regeneration, and old-growth trees on the perimeters of 

harvest units are sources of inoculum for spread to young-growth forests. But 

the disease generally does not flourish in even-aged forests because trees grow 

too rapidly in height and the parasite cannot spread vertically as fast. Dwarf 

Figure 128. Young broom of hemlock dwarf mistletoe.

Stem and Branch Diseases
141

mistletoe often will eventually die out as stands grow beyond 40 years of age 

or so. Partial harvests of old, infected hemlock forests can lead to varying 

amounts of dwarf mistletoe, with the amount dependent upon the number of 

large hemlocks that remain, their infection level, and their spatial distribution. 

Moderate mistletoe levels may be desirable where management objectives 

include sustaining wildlife habitat, however, little is know about actual wildlife 

use of dwarf mistletoe brooms in Alaska. 

Large or dead mistletoe brooms could be removed from infected trees in 

recreation areas to prevent injury or property losses because these brooms 

sometimes break out of trees during winter.

Reference: 1, 52, 100, 101, 121, 143, 160, 177, 212, 213, 219, 225–227, 232, 

256

Figure 129. Large brooms caused by 

hemlock dwarf mistletoe.

Figure 130. Large burl on western 

hemlock caused by an old bole infection 

of hemlock dwarf mistletoe.

Figure 131. Dead western hemlock tree 

with numerous hemlock dwarf mistletoe 

infections. Tree death resulted in a 

canopy gap.

Stem and Branch Diseases
142

Spruce Broom Rust 

Chrysomyxa arctostaphyli Diet.

Hosts: White, Sitka, and black spruce

Distribution: Across Alaska where the range of spruce and bearberry (Arctostaphylos uva-ursi (L.) Spreng.) coincide. Sitka spruce is not affected through‐

out most of Southeast Alaska, but populations have been found on Kuiu Island 

and in Glacier Bay.

Identification: Spruce trees infected by the rust fungus develop dense 

perennial witches brooms. In summer, spores are produced on current year’s 

needles giving the brooms an orange or yellowish coloration. The needles are 

shed in the fall and the brooms appear dead until spring. The fungus causes a 

purple-brown leaf spot on the alternate host, bearberry. The rust fungus cannot 

Figure 132. Perennial broom on white spruce caused by spruce 

broom rust.

Stem and Branch Diseases
143

complete a life cycle unless both host types (spruce and bearberry) are present. 

Spores produced on the bearberry infect spruce. 

Injury: Loss of height and diameter growth, bole deformation, and mortality 

are associated with the presence of the fungus on spruce. Rust brooms can 

serve as entrance courts for decay fungi such as Phellinus pini.

Remarks: Brooms by this rust fungus may be confused with brooms caused 

by hemlock dwarf mistletoe. Where practical, pruning of brooms on ornamen‐

tals and on trees in recreation areas can reduce losses and hazards. Ecologi‐

cally, large brooms on spruce provide important winter denning and nesting 

sites for wildlife, particularly flying squirrels in Interior Alaska. 

References: 1, 29, 71, 126, 176, 278

Figure 133. Chrysomyxa arctostaphyli

sporulating on the needles of a live broom. 

Stem and Branch Diseases
144

Western Gall Rust

Peridermium harknessii J. P. Moore

(= Endocronartium harknessii (J. P. Moore) Y. Hirat.)

Host: Shore pine

Distribution: Nearly all shore pine stands throughout Southeast Alaska.

Identification: A rust fungus that can infect directly from pine-to-pine without 

an alternate host. As with other rusts, the fungus is an obligate parasite and 

depends on a living host for its survival. Infection causes typically globose 

galls, sometimes hemispherical or pyriform in shape, on the branches and 

main stem of shore pine. In spring when the fungus is fruiting, the bright 

orange spores give the galls a distinctive orange coloration. Airborne spores 

infect nearby pines on young tissue. 

Injury: Galls are produced when the pathogen controls the tree’s growth hor‐

mones, causing extra tissue growth at the point of infection. The disease can 

cause growth loss and stem deformation of infected trees. The rust galls are 

often colonized by an opportunistic fungus, Nectria macrospora. This fungus 

produces tiny, red, spherical fruiting bodies. It kills the gall, which in turn kills 

the branch outwardly from the gall. Infection by gall rust and this secondary 

pathogen on the main stem can kill the top of the tree in this way. Thus, upon 

finding dead branches (or a dead top) on shore pine, look carefully and you 

will usually find a gall that has been killed in this manner. Pines with numer‐

ous reddish or brown branches are a common sight in Alaska. 

Remarks: Western gall rust is the most commonly observed disease of pine 

in Alaska. Faster growing trees are more susceptible than slow-growing or sup‐

pressed trees. Many galls may represent infections from the same year, indicat‐

ing ideal weather conditions for sporulation and infection during the spring 

Figure 134. Western gall rust sporulating on shore pine.

Stem and Branch Diseases
145

of that particular year (i.e., “wave year”). Control is possible by removing 

infected trees, especially those with main stem galls. Infected branches could 

be pruned from ornamental pines before or after they are colonized by Nectria. 

References: 2, 29, 33, 109, 126, 278

Figure 135. Dead top of shore 

pine caused by secondary infection 

of western gall rust by Nectria 

macrospora.

Stem and Branch Diseases
146

Cankers of Spruce and Hemlock

Discocainia treleasii (Sacc. in Sacc., Peck, and Trel.) J. Reid & 

Funk, Botryosphaeria picea (Funk), Xenomeris abietis (Barr)

and Aleurodiscus sp.

Hosts: Discocainia treleasii, Botryosphaeria picea, and Aleurodiscus sp. all 

cause branch or stem cankers on Sitka spruce. Xenomeris abietis and Discocainia treleasii are two fungi that cause cankers on western hemlock.

Distribution: Hosts range in Alaska.

Identification: Cankers can occur on branches or main stems. They often 

appear as swollen, sunken, resinosus, or callusing. Cankers are caused by the 

fungi listed above, but the same symptoms are sometimes caused by animal 

feeding, mechanical damage, or extreme weather. The only way to determine 

if fungi are responsible for causing cankers is to collect and identify their small 

fruiting bodies found on or adjacent to damaged tissue.

Injury: Many cankers on spruce and hemlock eventually heal and are not very 

damaging unless they are numerous, are located on the main stem, or occur 

on seedlings. Cankers on main stems of trees create an open infection court 

for decay fungi to cause heart rot, but this appears uncommon for conifers in 

Alaska.

Remarks: Most canker diseases of conifers in Alaska are typically minor dis‐

eases that do not need control. Several heart rot fungi (Phellinus hartigii and 

P. pini) can act as canker fungi by killing the cambium and sapwood of living 

trees. This can result in dead portions of the main stem and resemble a canker 

disease. An apparent canker disease on Sitka spruce that does not produce 

fruiting bodies and is of unknown cause is visible in areas around Juneau in 

late summer. Trees have scattered dying (yellow) branches in their crowns, but 

the situation does not progress to the point of affecting tree health. 

A canker disease of western hemlock, known as “hemlock canker” is peri‐

odically found causing lesions, callusing cankers, dead branches, or outright 

mortality on hemlocks near roads in several areas of Southeast Alaska. Road 

dust may aggrevate this problem, but the disease is sometime observed away 

from dusty roads. Lower branches of large hemlocks near roads are killed and 

small to medium-sized hemlocks can be killed. The actual role that dust plays 

in branch or tree mortality has not been determined. 

References: 70, 126, 232

Stem and Branch Diseases
147

Figure 136. Hemlock canker disease found along 

roads in Southeast Alaska.

Stem and Branch Diseases
148

Cankers of Hardwoods 

Ceratocystis fimbriata Ell. & Halst 

Cryptosphaeria lignyota (Fr.: Fr.) Auersw (=Cryptosphaeria populina 

(Pers.:Fr.) Sacc.)

Cytospora chrysosperma Pers. ex. Fr.

Encoelia pruinosa (Ell.& Ev.) Torkelson & Eckblad (=Cenangium 

singulare (Rehm.) Davidson and Cash)

Nectria galligena Bres. in Strass.

Valsa melanodiscus G.H. Otth (anamorph Cytospora umbrina)

Hosts: On alder: V. melanodiscus; on aspen: E. pruinosa, C. fimbriata, C. 

lignyota, C. chrysosperma; on balsam poplar: E. pruinosa, C. lignyota, C. 

chrysosperma; on cottonwood: C. lignyota, C. chrysosperma; on paper birch: 

N. galligena, on willow: C. chrysosperma.

Distribution: Host range in Alaska.

Identification: Infection biology and identifying features of mature cankers 

differ among these fungi. Perennial cankers develop on the main stem or 

branches, although the canker form varies from subtle, diffuse, and elongated 

to distinctly target shaped with flaring bark. E. pruinosa produces elongated 

sooty black cankers, often over 10 feet in length, and frequently mistaken for 

fire scars. Cankers produced by C. lignyota are long, narrow, spiraling snakelike around the tree, with a black stringy inner bark. Infection by C. fimbriata

and N. galligena results in target-shaped cankers with prominent concentric 

rings, callus folds, and flaring dead bark and are commonly initiated at dead 

Figure 137. Cryptosphaeria lignyota on 

aspen.

Stem and Branch Diseases
149

branches or twigs. Stem cankers caused by C. chrysosperma appear as subtle 

sunken bark areas, with a slight target shape, typically originating at the base 

of dead twigs. V. melanodiscus produces diffuse cankers that are elongated 

areas of sunken bark, irregular in outline. 

Injury: E. pruinosa is considered the most lethal canker pathogen of aspen, 

capable of girdling and killing a tree in as few as 3 years. V. melanodiscus is 

a primary cause of mortality of alder in Alaska, particularly riparian thin‐

leaf alder, Alnus tenuifolia. Stain, decay, and mortality are associated with 

infection by C. lignyota, with wounded trees of all ages potentially attacked. 

Damage from C. fimbriata and N. galligena consists mainly of trunk defor‐

mity; mortality is uncommon as tree diameter growth generally exceeds canker 

enlargement. Canker infection also can result in premature stem breakage. 

Remarks: With the exception of V. melanodiscus, infection by these fungi 

occurs primarily through wounds on stressed trees. Control is possible through 

prevention of wounds, pruning out branch cankers, maintaining vigorous 

stands, and shortened harvest rotations. V. melanodiscus, however, typically 

infects alders without wounds. Trees with large C. lignyota cankers probably 

have associated decay and should be carefully evaluated for stability in recre‐

ation areas. The term “diamond willow” refers to distinctly shaped depressions 

of willow stems caused by the canker fungus C. chrysosperma. “Diamond 

willow” is sought after by wood carvers who prize the reddish diamond 

shaped depressions that develop after fungal infection.

References: 1, 27, 30, 34, 35, 50, 70, 89, 126–129, 146, 155, 230, 276

Figure 138. A large Nectria 

galligena canker on paper birch.

Figure 139. Sooty bark canker, 

Encoelia pruinosa on aspen. 

Stem and Branch Diseases
150

Figure 142. Ceratocystis fimbriata on 

aspen.

Figure 141. Aspen stand severely infected 

with Ceratocystis fimbriata.

Figure 143. Cytospora canker on aspen.

Figure 140. Long diffuse Valsa 

melanodiscus canker on alder.

Stem and Branch Diseases
151

Rough Bark of Alder

Didymosphaeria oregonensis (Goodd.)

Hosts: Red alder and Sitka alder

Distribution: Throughout the range of alder hosts in Alaska

Identification: Roughened bark in distinct horizontal bands on branch or main 

stem of alder trees. These bands encircle the branch or stem and are somewhat 

swollen. Moss is often abundant in these zones. The tiny (1-mm diam.) fruiting 

bodies of the causal fungus can be found in these bands. Ascospores are green‐

ish in color.

Injury: Although the infection encircles the branch or main stem, there is 

little physiological injury to infected trees. The periderm and outer bark are 

disrupted, but the transporting phloem tissue is apparently not harmed. The 

disease appears to be more common on younger trees. Alder trees do not die 

from these infections.

Remarks: This disease is a curiosity because of its unusual appearance, but it 

causes little harm to infected alder trees.

References: 1, 70, 84

Figure 144. Rough bark of alder caused by the 

fungus Didymosphaeria oregonensis.

Stem and Branch Diseases
152

Annosus Root Disease

Heterobasidion annosum (Fr.) Bref. (=Fomes annosus Fr.)

Hosts: Western hemlock, Sitka spruce

Distribution: Southeast Alaska, possible elsewhere in Alaska.

Identification: Conks are uncommon; often hidden by litter at the base of 

infected trees or in hollow logs or stumps. Conks are perennial, irregular in 

outline, shelf or crust-like, woody or leathery. Upper surface concentrically 

ringed dark brown to black. Lower surface is white to tan with angular-shaped 

pores and a sterile margin (no pores). Pores are larger and more angularshaped than those of Fomitopsis pinicola, a similar appearing, but much more 

abundant conk in Alaska. Contex (interior) white or cream-colored. The lower 

surface has a reflective sheen when moved about under direct light. This 

fungus also has an asexual spore stage, but it is nearly microscopic and not 

normally observed.

Wood with incipient decay is pinkish to dull violet but the color varies some‐

what with host species. Incipient decay remains hard and firm. Sometimes the 

perimeter of the stained region is outlined by a dark line. Decayed wood has 

small elongated pockets with or without small black flecks in the white fiber 

filling the pockets. The white pockets eventually coalesce leaving a spongy 

white mass with black flecks. In the final stage, only a hollow in the roots or 

butt is left.

Figure 145. Annosus root disease.

Root Diseases
153

Injury: Annosus root and butt rot is a major disease in many forests of the 

temperate world, usually becoming more destructive as forest management 

intensifies. In Southeast Alaska, it occurs as a root and butt rot of old-growth 

trees, particularly in western hemlock. Losses are due to butt rot (i.e., cull) and 

tree mortality by uprooting and bole breakage induced by wood decay in roots 

and the lower bole.

Remarks: The role of H. annosum as a root disease in young growth hem‐

lock–spruce stands appears minimal but it is a potentially important disease. 

There are two distinct genetic forms of the fungus in western North America. 

The form found in Alaska, is the less aggressive form. It causes wood decay 

of live trees but not a lethal root disease. In old-growth forests of Southeast 

Alaska, H. annosum is the third most important cause of heart rot of west‐

ern hemlock. This estimate comes from the Kimmey (1956) study of heart 

rot and is based on the appearance of decayed woood in dissected trees, and 

did not involve confirmation by culturing fungi or modern genetic tools. In 

other regions, thinning increases the incidence and damage of this fungus. 

Airborne spores, either basidiospores from conks or the asexual spores can 

infect retained trees through wounds made during thinning; however, stumps 

Figure 146. White rot caused by Heterobasidion annosum.

Root Diseases
154

are often the primary source of infection for adjacent live trees in some forest 

ecosystems. Spores of H. annosum germinate on the surface of freshly cut 

stumps, colonize the stump’s root system, and then attack and the roots of an 

adjacent live tree. Research suggests that the infection of thinning stumps by 

H. annosum in this manner is rare and colonization of wounds on trees is also 

fairly infrequent in Southeast Alaska; thus, the disease poses little threat to 

young-growth management.

References: 1, 12, 29, 57, 62, 63, 114, 126, 143, 157, 158, 182, 183, 211, 214, 

215, 232

Figure 147. Conk of Heterobasidion annosum.

Root Diseases
155

Armillaria Root Disease

Honey Mushroom or Shoe String Root Rot 

Armillaria spp.

Hosts: All tree species in Alaska.

Distribution: Hosts range in Alaska.

Identification: A honey-colored mushroom occurring in clusters at the base of 

infected trees and stumps in late summer or autumn. Mushrooms sometimes 

have dark brown scales on top. The white gills are attached to both stalk and 

cap, and a ring may occur around the stem, a short way below the gills. Con‐

siderable variation exists among different mushroom collections. Rhizomorphs 

and mycelial fans are generally used to identify Armillaria since they are more 

abundant than mushrooms and occur year-round.

In the incipient (early) stage of decay, the wood appears faintly water soaked, 

then changes to a light brownish color. In the advanced stage of decay, the 

wood is light yellow or white, soft and spongy (stringy in conifers) with many 

fine black zone lines. There may be white fan shaped mycelial felts between 

the bark and wood, or black shoestring like rhizomorphs between the bark and 

wood and on the surface of the roots or in the soil. In conifers there may be an 

abnormal resin flow from the root collar of infected trees. Hardwood trees may 

exhibit “collar crack,” longitudinal cracks that appear at the root collar and 

extend a distance up the stem. 

Injury: Armillaria causes growth loss, butt and root rot, and mortality. Armillaria can quickly colonize root systems of recently dead or dying trees. In 

Figure 148. Gilled mushrooms of Armillaria sinapina.

Root Diseases
156

most environments, the fungus rarely kills trees that are not under some sort 

of stress. For example, Armillaria occurs on the roots and root collars of about 

one half of trees dying from yellow-cedar decline. It is not the primary cause 

of tree mortality, but probably speeds the process of tree death. Armillaria also 

occurs as an important heart rot fungus of conifers in Southeast Alaska where 

it is a leading cause of the wood decay of live trees, especially of western 

hemlock and, to a lesser extent, Sitka spruce.

Remarks: Armillaria has many roles in forests. Its rhizomorphs are common 

in woody debris and soil duff, where the fungus often occurs as a decomposer 

of woody debris. Thus, it is important as a nutrient recycler of many of the 

wood plant species in Alaska. Different species of Armillaria vary greatly in 

their aggressiveness. Generally, Armillaria species in Alaska tend to be the 

unaggressive wood decomposers or that are involved in tree death only when 

trees are already suffering some form of stress. Decaying wood by Armillaria

occasionally glows in the dark, a process known as bioluminescence. 

References: 1, 29, 34, 60, 62, 66, 126, 143, 157, 158, 183, 210, 211, 215, 216, 

218, 232, 255

Figure 149. Rhizomorphs 

(shoestring-like structures) 

under the bark of dying or 

dead trees are diagnostic of 

Armillaria.

Figure 150. Amillaria fans exposed beneath cedar 

bark.

Root Diseases
157

Tomentosus Root Rot

Inonotus tomentosus (Fr.:Fr) S. Teng

Hosts: Spruce, lodgepole pine; rarely larch 

Distribution: Host range in South-central and Interior Alaska. Sitka spruce is 

not affected throughout most of Southeast Alaska, but populations have been 

found near Skagway.

Identification: Annual fruiting bodies are produced in the fall, developing 

on the ground near the base of infected trees. Fruiting bodies are leathery and 

small (usually less than 4 inches in diameter) with a central stalk. The upper 

surface is tan to rust-brown and velvety. The lower surface is cream to yellowbrown with small round pores that extend part way down the stalk. 

The early stage of root decay is characterized by a red-brown to pink stain in 

the heartwood. Wood with advanced decay contains elongated spindle shaped 

pits, with poorly defined margins, separated by red-brown firm wood. The 

cross section of infected roots with advanced decay appears honeycombed. 

Stump surfaces of infected trees often exhibit stain and honeycombing. 

Injury: Damage includes outright mortality, butt decay of up to one third 

of the gross volume, premature uprooting from loss of structural roots, and 

growth reduction. Host trees are susceptible to infection at any age. The fungus 

efficiently spreads through root contacts between infected and healthy roots, 

thus diseased trees occur in groups and mortality results in stand openings. 

Following death of an infected tree, the fungus may remain alive for decades. 

Spruce trees planted or growing within active tomentosus root rot centers 

become infected through root contact with diseased stumps/roots and may be 

Figure 151. Extensive root rot caused by Inonotus tomentosus.

Root Diseases
158

killed outright. 

Remarks: Avoid planting spruce trees in root disease centers as infected 

stumps and roots serve as inoculum sources for succeeding generations of 

spruce trees. Losses can be mitigated by establishing less susceptible spe‐

cies (e.g. hardwoods) on infected sites, and planting susceptible species (e.g. 

spruce) at least 3 meters from known inoculum sources. Lodgepole pine, 

Pinus contorta, though not a native tree in Alaska, is occasionally planted in 

South-central and Interior, is susceptible to tomentosus root rot, and should 

not be planted in root rot centers. Thinning infected stands may increase the 

incidence and damage of this root disease. Careful diagnosis through root 

inspection is important because advanced decay can be mistaken for other 

pocket rots, particularly Phellinus pini. 

References: 1, 19, 83, 90, 144, 163–168, 206, 270–273

Figure 152. Honeycombed 

advanced decay of spruce roots.

Figure 153. Leathery annual 

fruiting bodies of Inonotus 

tomentosus.

Root Diseases
159

Wood Decays and Stains

Wood decay causes the greatest disease-related loss of timber volume to live 

trees in Alaska. The effects are particularly acute in old-growth forests in 

coastal Alaska where, on average, 31% of the volume of live trees is defective. 

Along with the direct cause of wood volume loss, decay fungi also increase 

logging and milling costs and complicate management by introducing errors 

in yield and cruise computations. On the other hand, wood decay is critically 

important to the normal functioning of forest ecosystems and has key roles in 

nutrient cycling, soil development, small-scale disturbance, wildlife habitat, 

and biological diversity. For example, the spruce beetle mortality of millions 

of spruce trees annually on the Kenai Peninsula through the 1990s precipitated 

research on the fate and decomposition of these dead trees.

Many decay fungi listed here cause heart rot of living trees, others decay the 

wood of dead trees, and some grow on both live and dead trees. Most of these 

decays do not actually interfere with the normal growth of live trees. They can 

affect tree structure, however, and contribute to wind-breakage and windthrow. 

Other specialized fungi (e.g. Phellinus and P. pini) may attack the sapwood 

and cambium of live trees after existing as a heart rot fungus. Many of the 

fungi that are normally found on dead trees can grow on live trees that have 

large stem wounds or broken tops (e.g., Fomitopsis pinicola). Root rot fungi 

also cause wood decay, particularly in the lower bole. Several common root 

diseases in Alaska are discussed in the previous root disease section.

The management of decay fungi on live trees is generally simple because 

decay levels are so highly correlated with tree age and tree injuries. These 

disease levels can be reduced greatly by limiting tree age (e.g., managing on 

shorter rotations) and reducing tree wounds during treatments. In multiple 

resource management where the beneficial roles of wood decay need to be 

maintained, decay levels of trees can be manipulated by creating forests with 

mixtures of tree ages and influencing the amount of tree injuries. Thus, tree 

injuries from logging wounds, animal feeding, or weather events can have ben‐

eficial ecological effects. 

Each wood decay fungus decomposes wood in one of two ways: by white 

rot where cellulose and lignin are degraded, or by brown rot where cellulose 

is consumed but lignin is left largely intact. These two modes of wood decay 

have different outcomes affecting such things as habitat for wildlife and carbon 

sequestration. Some wood decay fungi produce mushrooms or other fruiting 

bodies that may be considered to be edible. Be absolutely certain about the 

identity of any fungus that you pick for consumption. Call the Poison Center 

(907-563-3393) for emergencies or more information.

References: 66, 97, 110, 116, 157

Wood Decays and Stains
160

Pini Conk or Red Ring Rot 

Phellinus pini (Thore : Fr.) Pilat (=Fomes pini Thore : Fr.)

Hosts: Western and mountain hemlock, Sitka, white, and black spruce, west‐

ern redcedar, and lodgepole pine.

Distribution: Host ranges in Alaska.

Identification: The perennial conk is common on live trees. The conk is 

woody and typically shelf-shaped with a sharp edge. The upper surface is 

dark brown, hairy (when young), with concentric ridges and a narrow velvety, 

light brown to golden margin. Lower surface is dark brown with pores that 

are variable in size and shape. Conk interior is stratified, yellow brown when 

young and dark brown when old. Blind conks or punk knots (swollen knots 

filled with golden-brown mycelium) are common. The early stage of decay 

Figure 154. Phellinus pini conk 

on hemlock.

Figure 155. Conks of Phellinus 

chrysoloma (P. cancriformans).

Wood Decays and Stains
161

Figure 156. Resinous punk knots 

(blind conks) of Phellinus pini.

Figure 157. White pocket rot and punk knots caused by Phellinus pini.

Wood Decays and Stains
162

appears as a discoloration of the heartwood. In white spruce, the discoloration 

is light purplish to gray, later changing to reddish brown. In western redcedar 

the discoloration is a narrow bluish to reddish brown band along the margins 

of the more advanced decay. The advanced decay consists of elongated spindle 

shaped pockets or cavities parallel to the grain and sometimes separated by 

apparently sound wood that may be resin soaked. Decay pockets may be 

empty or filled with a mass of white fibers. Fine black to brown zone lines 

may be present.

Injury: This fungus causes a white pocket rot that can extend the entire length 

of the tree bole. It is particularly common on mountain hemlock wherever the 

tree grows in Alaska, but western hemlock is also commonly infected. The 

fungus infects and decays the heartwood of living trees, but does not continue 

decaying dead trees long after they die. In living trees, P. pini can grow into 

sapwood after decaying heartwood and thereby kill trees. A closely related 

species, Phellinus chrysoloma (P. cancriformans (M. Lars. et al.) M. Lars & 

Lomb.), can cause cankers or dead portions of the bole in addition to exten‐

sive heartwood decay. Sporophores of P. chrysoloma are smaller and closely 

stacked on top of one another. 

Remarks: As with other heart rot fungi, this disease can be managed by 

harvesting trees of susceptible species before they reach old age. Live, infected 

trees may serve as valuable habitat for cavity nesting animals. 

References: 1, 12, 22, 29, 60, 64, 66, 82, 83, 90, 110, 126, 157, 182, 183, 240

Figure 158. White pocket rot caused by Phellinus pini.

Wood Decays and Stains
163

Pinicola Conk or Red Belt Fungus

Fomitopsis pinicola (Swartz ex Fr.) Karst

(=Fomes pinicola (Swartz ex. Fr.)

Hosts: Sitka, white, and black spruce; western and mountain hemlock; lodge‐

pole pine; and occasionally western redcedar and birch.

Distribution: Throughout Alaska.

Identification: Fruiting bodies very abundant, perennial, hard, woody, flat 

to hoof-shaped. Upper surface zoned, smooth, gray to black, usually with a 

reddish band near the margin. Lower surface creamy white with minute pores. 

Contex (tissue inside) layered and light buff in color.

Wood in the incipient stage of decay is stained a light brown or yellow brown. 

Wood in the typical advanced stage of decay is reddish or yellow brown, cubi‐

cal, and crumbly. Conspicuous mycelial felts often form in the cracks in the 

decayed wood.

Injury: F. pinicola causes a brown cubical decay of both live and dead trees. 

Infection of live trees probably occurs through wounds. Fruiting bodies on 

live trees are often found on these large wounds. By causing loss of structural 

support in the decay of live trees, heart rot fungi such as F. pinicola contribute 

to trees dying when their boles collapse or break. 

Remarks: This is the most commonly seen conk in the conifer forests of 

Alaska. It is relatively common on wounded live trees, but is very abundant 

on the wood of dead conifer trees whether standing or down. Thus, the fungus 

is remarkably important as a decomposer in conifer forests where it converts 

Figure 159. Pinicola conks on dead 

hemlock.

Wood Decays and Stains
164

wood to a stable structure known as partially modified lignin. Given the 

enormous inputs of this material, it is undoubtedly important in soil formation 

in coastal forests. In live trees of Southeast Alaska, F. pinicola causes more 

decay than all other fungi combined for Sitka spruce and is the third leading 

decay for western hemlock. Timber in service is susceptible to decay from this 

fungus. Management of F. pinicola is by limiting tree age (short timber rota‐

tions), controlling the wounding live trees, and the prompt salvaging of dead 

trees.

References: 1, 12, 22, 29, 60, 62, 63, 66, 83, 90, 110, 116, 126, 143, 158, 183, 

222

Figure 160. Two pinicola conks, one showing the “red belt” on the 

upper surface. Genetic control of color variation is not understood.

Figure 161. Brown cubical 

rot and white mycelial felts of 

Fomitopsis pinicola.

Wood Decays and Stains
165

Chicken of the Woods or Sulfur Fungus

Laetiporus sulphureus (Bull. ex Fr.) Bond. et Sing.

(=Polyporus sulphureus Bull. ex Fr.)

Hosts: Sitka spruce, hemlock, cottonwood, and poplar

Distribution: Hosts range in coastal Alaska

Identification: The fruiting body of this fungus is annual and emerges during 

the mushroom season in Alaska (e.g., August in many areas). Upper surface 

lemon yellow to orange. Lower surface sulfur yellow with small pores often in 

clusters. Contex (tissue inside) yellow, broad, watery and soft when fresh. The 

annual conk turns white when it dies and often falls to the ground. This dead, 

white stage is the way it is found during most of the year.

Injury: Incipient wood decay is a brown to reddish brown discoloration. 

Wood with advanced decay is dark reddish brown, cubical, brittle, and crum‐

bly. In longitudinal section, the wood sometimes has a rippled look. Thick 

mycelial felts usually occur in the cracks. This decay closely resembles other 

Figure 162. Fruiting bodies 

of chicken of the woods.

Wood Decays and Stains
166

brown rot decay caused by Fomitopsis officinalis but the mycelial felts are not 

bitter to the taste.

Remarks: This fungus causes a brown cubical rot of live and dead trees. 

Timber losses can be managed by using shorter rotations and controlling the 

wounding of live trees. Trees with fruiting bodies are potentially hazardous 

around homes or recreation areas and should be evaluated for removal. The 

fruiting body is edible when fresh, hence the name chicken of the woods. Be 

absolutely certain of the identity of any mushroom or fungus that you consume 

and do not select old fruiting bodies.

References: 1, 12, 22, 29, 63, 66, 83, 110, 126, 157, 182, 183

Figure 163. Remnants of old conks of Laetiporus 

sulphureus.

Wood Decays and Stains
167

Velvet Top Fungus

Phaeolus schweinitzii (Fr.) Pat. (=Polyporus schweinitzii Fr.)

Hosts: Sitka spruce, white spruce, and western hemlock.

Distribution: Southeast and South-central Alaska

Identification: Fruiting bodies normally occurs on the lower bole or arise 

from the soil near the base of the tree where they are decaying wood in roots. 

Fruiting bodies are bracket-like when occurring on the bole and circular, 

stalked, and with a sunken center when arising from the soil. Although large, 

fruiting bodies are annual. They are dark brown, with yellow brown margin, 

hairy, soft and spongy when fresh, brittle and dark brown when dead. The 

undersurface has large irregularly shaped pores and is greenish turning deep 

red brown if bruised when fresh.

Wood with incipient decay is light reddish brown or yellowish brown. 

Advanced decay is red- to yellow-brown, cubical, brittle, and crumbly and 

has a turpentine odor. Thin resinous mycelial felts may occur in the cracks of 

decayed wood.

Injury: The fungus causes a brown cubical butt rot of conifers. Mature trees 

with this heart rot sometimes die through collapse or breaking of the bole due 

to loss of structural support. Thus, P. schweinitzii is an important agent in tree 

mortality or small-scale disturbance in old forests.The role of this fungus in 

causing a root disease on young trees is unknown in Alaska but it does not 

appear to be significant; elsewhere in the world it can be destructive to youngFigure 164. Phaeolus schweinitzi on a hemlock.

Wood Decays and Stains
168

growth stands. 

Remarks: Effects of this heart rot fungus can be managed by preventing 

injury to trees and by reducing rotation length. Fruiting bodies on or near the 

base of trees indicate a potentially hazardous condition near homes or in recre‐

ation areas; infected trees should be evaluated for removal.

References: 1, 12, 29, 63, 66, 83, 90, 110, 126, 157, 182, 183

Figure 165. Older fruiting 

body of velvet top fungus.

Wood Decays and Stains
169

Artist’s Conk 

Ganoderma applanatum (Pers.: Wallr.) Pat.

Hosts: Commonly on hardwoods including paper birch, aspen, cottonwood, 

alder, willow; also found on western and mountain hemlock, white and Sitka 

spruce. 

Distribution: Host range in Alaska.

Identification: The perennial conk is woody and shelf-like. The upper surface 

is smooth, concentrically ridged, tan gray to grayish black, often covered with 

a tan dusting of spores. The margin, when fresh, is typically white. The under 

surface is white when fresh, turning yellowish with age, with small round 

pores. When fresh, the underside turns brown immediately when scratched 

or marked, hence the common name of the “artist’s conk.” The interior of the 

conk is dark reddish brown, layered, with tubes in older layers sometimes 

overgrown with white mycelium.

The early stage of decay, in most host species, is characterized by bleached 

areas encircled by a dark brown stain. In western hemlock, the areas are violet 

to lilac. In the advanced stage, the wood is whitish to cream, mottled, soft and 

spongy, and usually with fine black zone lines.

Injury: This fungus causes a white mottled heart rot of living and dead trees. 

Infection of living trees apparently occurs through wounds and broken tops. G. 

applanatum also attacks timber in use. 

Remarks: Management of this fungus can be achieved through removal of 

infected trees and wound prevention on residual trees. Trees with G. applanatum conks have extensive associated decay and, in recreation areas, should be 

carefully evaluated for stability. 

References: 1, 29, 34, 60, 83, 126, 182, 183

Figure 166. Artist’s conk on paper birch. This 

fungus also invades conifers.

Figure 167. Ganoderma conk 

on alder.

Wood Decays and Stains
170

Lacquer Conk or Varnish Conk 

Ganoderma tsugae Murr. (=Ganoderma oregonense Murr.)

Host: Western hemlock

Distribution: Southeast Alaska

Identification: Upper surface of fruiting body is distinctly varnish- or lacquerlike, and shiny reddish brown. Lower surface is white. Conks may be several 

centimeters to half a meter wide and are attached by a lateral stalk. 

Decayed wood is wet, spongy, straw-colored or white, and may have large 

black spots scattered throughtout. Red-brown zones may be present in decayed 

wood.

Injury: This fungus is not known to grow on live trees. 

Remarks: G. tsugae is not common. Conks have an unusual appearance and 

are generally found on large, old stumps or logs that have been down for a 

considerable number of years. 

References: 29, 83, 126, 182, 183

Figure 168. Lacquer conk on an old 

hemlock log.

Figure 169. Young lacquer conk.

Wood Decays and Stains
171

Indian Paint Fungus 

Echinodontium tinctorium (Ell.& Ev.) Ell. & Ev.)

Hosts: Mountain hemlock, perhaps western hemlock

Distribution: Northern Southeast Alaska near Haines and Skagway; and 

South-central Alaska within the limits of mountain hemlock’s range.

Identification: Hard, woody hoof-shaped conks grow on or under branch 

stubs. The upper surface is dull black, rough and cracked, the undersurface 

consists of coarse grey teeth or spines, the context is brick red to bright orange 

and is diagnostic.

The early stage of decay appears as a light brown stain in the heartwood. In 

the advanced decay stage, heartwood is reduced to a rust-red or brown, stringy, 

fibrous mass. 

Injury: This fungus causes a brown stringy heart rot of live hemlocks. The 

presence of fruiting bodies on live trees indicates substantial heartwood decay. 

Remarks: Infection of hemlocks occurs through small dead branchlets, often 

while trees are small and suppressed. Significant decay develops later, after 

infected trees are stressed through wounding or other factors. Volume losses 

may be reduced by shortening harvest rotations. Trees with conks have exten‐

sive associated decay and, in recreation areas, should be carefully evaluated for 

removal.

References: 1, 29, 64, 66, 83, 126, 182, 183

Figure 170. Echinodontium tinctorium

on mountain hemlock.

Figure 171. Distinctive spines and 

orange color inside an Indian Paint conk.

Wood Decays and Stains
172

Quinine Conk

Fomitopsis officinalis (Vill.:Fr.) Bond & Sing.

(=Fomes officinalis Vill.:Fr.) 

(=F. laricis (Jacq.)Murr.)

Hosts: Sitka spruce, shore pine, hemlocks.

Distribution: Host range in Alaska.

Identification: Fruiting bodies are variable in size; sometimes huge; hoofshaped to long and cylindrical. Upper surface zoned, white, and turning gray, 

brown, or sometimes greenish when colonized by algae. Lower surface white 

with small regular pores. Context white, soft, cheesy, then becoming chalky 

with age. The conk has a bitter taste.

Wood in the incipient stage has a light yellowish, reddish discoloration. The 

advanced stage of decay appears as brown cubes that are easily crumbled and 

there are thick, bitter tasting mycelial felts in the shrinkage cracks.

Injury: The fungus causes a brown cubical rot. A single conk on the bole 

indicates substantial decay and loss of commercial wood value. 

Remarks: As with other heart rot fungi, shortened rotations may serve to 

reduce timber losses in forests. Trees with conks in recreation areas are poten‐

tially hazardous because of the large amount of decay indicated by each conk. 

Historically, fruiting bodies of this fungus were collected, carved into figures, 

and placed on the graves of Tlingit shamen. 

References: 1, 26, 29, 83, 90, 126, 182

Figure 172. Quinine conk.

Wood Decays and Stains
173

Hartig’s Conk

Phellinus (Allesch. & Schnabl) Bond.

(=Fomes hartigii (Allesch. & Schnabl) Bres.)

(=Polyporus hartigii (Allesch. & Schnabl.0

Host: Western and mountain hemlock.

Distribution: Host range in Alaska.

Identification: Brown perennial fruiting usually located on the underside of 

limbs or branch stubs, but sometimes occurring directly on the bole. Upper 

surface dark brown to black and cracked. Under surface rusty brown to brown 

with very small regular pores. Tissue inside conk is yellow- to rusty-brown 

with streaks of white mycelium.

Incipient decay appears as a brown to purple discoloration in irregular patches. 

Advanced decay has a light bleached look and appears laminated on radial 

sections because of differential decay of spring and summerwood. There are 

light buff to brown horizontal streaks on tangential sections. Brown zone lines 

are common.

Injury: This fungus causes a white rot of sapwood and heartwood of living 

trees. Decay is usually confined to the side of truck where infection occurred 

and normally extends only a few feet above and below the conk. Decay of the 

sapwood causes a sunken canker where the side of a tree is killed. 

Remarks: Management can influence the abundance and effects of this 

fungus by altering the length of timber rotations. This fungus is sometimes 

confused with and referred to as Phellinus robustus. Hartig’s conk is named 

after Robert Hartig, a 19th Century German forest scientist who is generally 

regarded as the father of forest pathology.

References: 1, 22, 29, 60, 82, 83, 110, 126, 157, 182, 183

Figure 173. Hartig’s conk on a dwarf 

mistletoe broom.

Wood Decays and Stains
174

Borealis Conk

Climacocystis borealis (Fr.) Kotl. & Pouz.

(=Polyporus borealis Fr.)

Host: Sitka spruce, western hemlock and mountain hemlock.

Distribution: Southeast Alaska.

Identification: Fruiting body annual, shelving, white, fleshy. Upper surface 

shaggy, lower surface with large pores, interior tissue is white.

Decayed wood is a yellowish white and shows white flecks in cross section. 

Tangential and radial faces have white patches around small pinholes and 

cross-grain white streaks. Thoroughly decayed wood fractures in a cubical 

pattern.

Injury: This fungus causes a white mottled wood rot of living trees and con‐

tinues decay in wood of dead trees. 

Remarks: As with other decay fungi, managers can reduce losses of the 

timber resource by using shorter rotations. 

References: 29, 63, 83, 126, 182, 183

Figure 174. Borealis conks on a log end.

Wood Decays and Stains
175

Purple Conk

Trichaptum abietinus (Dicks:Fr.) Ryvarden

(=Hirschioporus abietinus (Dicks.:Fr.) Donk

(=Polyporus abietinus (Dicks.:Fr.) Donk)

Hosts: Sitka and white spruce; western hemlock

Distribution: Host range in Alaska.

Identification: Fruiting body is annual, small, thin, shelving, and sometimes 

crustlike. Upper surface is hairy, zoned, and gray, may become greenish with 

age and algae. Lower surface is purplish when young, turning brown with age. 

Pores vary from regular to irregular in shape and are conspicuous.

Decayed wood in the incipient stage has a faint yellowish to tan color. The 

wood becomes honeycombed with small pockets in the advanced stage of 

decay. The pockets are filled with whitish fibers initially but become empty 

later as the wood becomes spongy or corky.

Injury: This fungus is restricted to dead trees and does not harm live trees.

Remarks: The fungus causes a white pocket rot of dead coniferous sapwood. 

Both woody debris in forests and wood in use are attacked. Dry and well-ven‐

tilated conditions reduce incidence of the fungus on wood in use.

References: 1, 12, 29, 60, 83, 126, 182

Figure 175. Upper surface of 

Trichaptum abietinum conks.

Figure 176. Violet colored lower surface 

of the purple conk.

Wood Decays and Stains
176

Yellow Cap Fungus or Scaly Cap Mushroom 

Pholiota spp.

Host: Spruce, hemlock, cottonwood, birch, aspen

Distribution: Host range in Alaska.

Identification: Fruiting body is an annual mushroom, typically produced in 

clusters. The upper surface of the mushroom cap is yellow-brown and usually 

scaly and/or sticky. Young specimens may be flagrantly scaly while older 

specimens may become sticky and lose their scales. Gills on the lower surface 

are yellow at first, later turning brown. The stem (i.e. stipe) may or may not 

have a ring and may be scaly. Mushrooms may develop at the base of the tree 

or on the stem, particularly at wounds.

Incipient wood decay appears as light yellowish areas in the heartwood. Wood 

with advanced decay is yellow-white with yellow or yellow-brown streaks. 

Thin strands of yellow-brown mycelium, occur along the grain. If the strands 

of mycelium are pulled from the wood, irregular channels, resembling insect 

tunnels, remain.

Injury: Pholiota species cause a white rot of wood in live trees, typically 

invading through wounds. Mushrooms on a living tree indicate extensive 

decay. Some species are root rot fungi while others cause stem decay. 

Remarks: There are many species of Pholiota found in Alaska, only some are 

capable of decaying live trees. For exact determination of any specific speci‐

men, a key for Pholiota must be used. Managers can reduce effects of wood 

decay fungi by limiting tree ages through shorter rotations and by reducing 

trunk wounds. 

References: 1, 12, 29, 126, 145, 224, 251

Figure 177. Pholiota mushrooms on 

aspen.

Wood Decays and Stains
177

Coniophora Brown Rot

Coniophora arida (Fr.) Karst, C. olivacea (Fr.:Fr.) Karst

C. puteana (Schum.:Fr.) Karst

Hosts: Spruce, hemlock, and occasionally hardwoods.

Distribution: Hosts range in Alaska.

Identification: The fruiting bodies are annual flattened, crust-like, principally 

olive or very light brown in the center and white towards the margins, lack‐

ing pores, gills, or teeth. Fruiting bodies are uncommon and difficult to find 

because they occur in a live tree within decay columns or on the lower side of 

downed logs.

Wood in the advanced decay stage becomes uniformly cubical with frequent 

longitudinal cracks. Decayed wood varies from purple brown to light or dark 

brown. A thin brown mycelium may develop on cube faces and within the 

longitudinal cracks of the wood.

Injury: These fungi cause a brown cubical heart rot of live trees typically 

Figure 178. Brown cubical rot of white spruce caused by 

Coniophora spp.

Wood Decays and Stains
178

invading thru wounds. Presence of a fruiting body indicates considerable 

decay. These fungi are particularly common in mature white spruce stands in 

Interior Alaska.

Remarks: As with other heart rot fungi, shortened rotations will help reduce 

timber losses from these pathogens. Live trees with extensive decay may pro‐

vide important habitat for cavity nesting birds and mammals.

References: 183, 251

Figure 179. Crust-like fruiting body of Coniophora puteana.

Wood Decays and Stains
179

Redcedar White Ring Rot

Ceriporiopsis rivulosa (Berk. & Curt.) Gilbn. & Ryv.

(=Poria rivulosa (Berke and Curt.) Cooke)

(=P. albipellucida Baxt.)

Host: Western redcedar.

Distribution: Southeast Alaska, south of Sumner Straits.

Identification: Fruiting bodies are annual, white, thin, and crustlike with 

pores. Margins are thin and appear water soaked. Fruiting bodies are rare.

The incipient stage of decay is an irregular or crescent-shaped yellowish to 

brownish discoloration sometimes surrounded by a blue to red zone. In the 

advanced stage, the decayed wood is crumbly, white or yellowish with radial 

cracks, small pockets, and laminations.

Injury: This fungus is the leading causes of heart rot in living western redce‐

dar trees. It causes a white rot. 

Remarks: Mature western redcedar trees frequently have a considerable 

amount of internal wood decay. Along with the two white rot decays men‐

tioned here (Ceriporiopsis rivulosa and Phellinus weirii), the brown rot fungus 

Postia sericeomollis (=Poria asiatica) contributes to this decay. External indi‐

cators of decay are often not helpful in allowing forest workers to judge decay 

levels and none of these fungi produces a common or conspicuous fruiting 

body. Management of decay levels can be achieved by limiting tree age where 

that is desirable.

References: 1, 29, 32, 83

Figure 180. White rot of western redcedar caused by Ceriporiopsis 

rivulosa.

Wood Decays and Stains
180

Yellow Ring Rot

Phellinus weirii (Murr.) Gilbn. (=Poria weirii Murr.)

Host: Western redcedar

Distribution: Southeast Alaska, south of Sumner Straits.

Identification: Fruiting bodies are uncommon and difficult to find because 

they occur on the bottom of down logs, along root crotches, or inside decay 

columns. Fruiting bodies are dark brown or yellow brown perennial layers. 

The layers crack with age. Conk margins are buff to white when fresh. Context 

is layered and brown. 

The incipient stage of decay is yellow to reddish brown and often crescent 

shaped or irregular in cross section. In the advanced stage of decay, the wood 

is yellow or light colored, stringy, with small pockets. The decayed wood 

separates (i.e., delaminates) at the annual rings with brown mycelium forming 

between the resulting laminations and in the pockets. 

Injury: This fungus causes a white rot of the roots and lower bole of western 

redcedar. The incidence and amount of decay are associated with tree age. 

Remarks: Management can reduce timber loss by using shorter rotations 

for western redcedar. Another form of this fungus, which may be classified 

taxonomically as a separate species, causes a serious root disease of many spe‐

cies of conifer in forests of western North America. This form is not present in 

Alaska, however.

References: 1, 12, 29, 32, 63, 82, 83, 90, 126, 157, 183

Figure 181. Laminated decay of western 

redcedar caused by Phellinus weirii.

Figure 182. Crust-like fruiting body of 

Phellinus weirii.

Wood Decays and Stains
181

Cedar Brown Cubical Pocket Rot

Postia sericeomollis (Romell) Julich (=Oligoporus sericeomollis, 

Poria asiatica)

Hosts: Mainly western redcedar, but also yellow-cedar and other conifers

Distribution: Southeast Alaska

Identification: Fruiting bodies are white, annual, and about 6 inches wide. 

They are rarely encountered, but may be found on dead trees. Typically, there 

are no outward signs that trees are infected. 

Early or incipient decay is tan to yellow brown. Decay typically occurs in dis‐

crete pockets with apparently unaffected surrounding wood. But these pockets 

of decay can coalesce, leading to larger areas of decay. Advanced wood decay 

is brown, brittle, and breaks apart in cubical chunks. 

Injury: This is the most common brown rot of western redcedar. 

Remarks: Western redcedar has a surprising level of heart rot for a tree spe‐

cies that produces such decay resistant wood. This is one of three fungi able 

to overcome cedar heart wood chemistry and cause extensive decay. In Idaho, 

birds are known to use decayed pockets by this fungus in live redcedar trees as 

nesting habitat.

References: 1, 29, 32

Figure 183. Cedar pocket rot.

Wood Decays and Stains
182

Oyster Mushroom

Pleurotus ostreatus (Jacq.:Fr.) Kumm.

Hosts: Alder, aspen, cottonwood, birch

Distribution: Host range in Alaska.

Identification: Fruiting body is a fleshy annual mushroom that grows in clus‐

ters. Upper surface is smooth, white, or grayish. Lower surface has prominent 

gills that extend onto the stalk.

Early decay of heartwood and sapwood is characterized by a brown discol‐

oration. Advanced wood decay is white and flaky, with black flecks scattered 

throughout. 

Injury: This fungus causes a white flaky rot of hardwoods; both sapwood and 

heartwood are decayed.

Remarks: Sporophores on logs indicate substantial wood decay. This species 

of mushroom is edible, but be absolutely certain about the identity of any 

mushroom that you consume. For specific determinations, a key for the genus 

should be used.

References: 29, 34, 126, 183

Figure 184. Oyster mushroom on aspen.

Wood Decays and Stains
183

Coral Fungus

Hericium abietis (Weir:Hubert) K. Harrison

Hosts: Western hemlock and Sitka spruce.

Distribution: Host range in Alaska.

Identification: Fruiting bodies are annual, soft, fleshy, white, coral-like and 

composed of many hanging spines. Fruiting bodies are found usually in the 

fall on the sides and ends of down logs or logs in decks and on scars on stand‐

ing trees. The size of fruiting bodies is quite variable with some approaching 1 

meter in diameter.

The early stages of decay appear in the heartwood as a yellowish to brown 

stain, which later changes to long spindle-shaped yellow spots. In the 

advanced stage of decay, the wood is riddled with long spindle-shaped pockets 

that may or may not contain a yellowish mycelium. In this stage, the wood is 

very splintery, fibrous, and has a honeycombed appearance in cross-section.

Injury: This fungus causes a white rot that affects the bole of either living or 

dead trees. 

Remarks: Managers can reduce decay levels in forests by controlling the 

wounding of living trees, scheduling the early harvest of damaged trees, and 

limiting tree ages. The fruiting body of this fungus is edible, but be certain 

about the identity of any fungus that you consume. There are other closely 

related species on both hardwoods and conifers (i.e., coral fungi), thus, the use 

of detailed keys and guides are recommended for precise species identifica‐

tion. 

References: 12, 29, 90, 126, 183

Figure 185. Coral fungus.

Wood Decays and Stains
184

Tinder Conk

Fomes fomentarius (L:Fr.) Kichx.

Host: Paper birch

Distribution: Throughout the range of birch in Alaska.

Identification: The perennial conk is woody and distinctly hoof-shaped with a 

concentrically zoned, smooth, gray or gray-brown to black upper surface. The 

lower surface is brown with small regular pores; conk interior has dark brown 

tubes that are somewhat stratified and partially filled with or incrusted with 

white mycelium. 

In the early stage, decayed wood is brownish and firm while in the later stage it 

is soft, spongy, yellow white, with narrow brown to black zone lines and small 

radial cracks.

Injury: This fungus causes a white rot of both sapwood and heartwood in 

living and dead trees. Presence of a conk indicates little usable heartwood. 

Remarks: Infection occurs through wounds. The conk is common on dead 

trees or dead portions of live trees. Some control of this fungus may be 

achieved by removal of infected trees bearing conks, minimizing damage to 

live trees, and shortened rotations. Traditionally, the fungus has been used as 

fire starting material and, as early as the fifth century B.C., Hippocrates wrote 

about its use for medicinal purposes. 

References: 1, 29, 83, 126, 182, 208

Figure 186. Tinder conk on 

paper birch.

Wood Decays and Stains
185

False Tinder Conk

Phellinus igniarius (L.:Fr.) Quel. (=Fomes igniarius L.:Fr.)

P. tremulae (Bord.) Bond et Boriss

Hosts: P. igniarius on paper birch,alder, and other hardwoods ; P. tremulae on 

aspen and cottonwood.

Distribution: Host range in Alaska.

Identification: The fruiting bodies are similar for these Phellinus species. 

Conks are perennial, hoof-shaped, with an upper surface that is zoned, greyish 

black to black, becoming cracked and cinder-like with age. Lower surface is 

brown with small circular pores. Context layered and rusty brown with many 

tubes in older layers filled with white mycelium. The upper and lower surfaces 

of P. tremulae conks are at angles of about 45° from horizontal, whereas the 

lower surface of P. igniarius conks are close to horizontal. 

Wood in the incipient decay stage is yellowish white or with white spots, 

streaks, or large areas of heartwood surrounded by a yellowish green to brown‐

ish black zone. In the typical decay stage, the wood is lightweight, soft, and 

whitish with fine black zone lines throughout.

Injury: These fungi cause a white trunk rot. Presence of a conk indicates 

considerable decay. 

Remarks: Infection by these fungi is typically through dead branch stubs or 

wounds. Volume losses increase with tree age, thus removal of infected trees, 

Figure 187. Phellinus igniarius conk on paper birch.

Wood Decays and Stains
186

prevention of wounding of uninfected trees, and shortened rotations help 

reduce timber losses from these pathogens. Trees with conks could be hazard‐

ous and should be carefully evaluated in recreation areas and near homes.

References: 1, 29, 34, 82, 83, 126, 128, 180, 182, 194

Figure 188. Phellinus tremulae on aspen.

Wood Decays and Stains
187

Cinder Conk

Inonotus obliquus (Pers.:Fr.) Pilat (=Poria obliqua (Pers.:Fr.) Karst.)

Host: Paper birch, rarely on cottonwood.

Distribution: Hosts range in Alaska.

Identification: Perennial sterile conks are the most conspicuous sign of infec‐

tion by this fungus. The sterile conk is a cinder-like mass of fungal tissue with 

a rough, black exterior. The interior tissue is yellow-brown to rust brown with 

a punky texture. Inconspicuous, short-lived fertile conks may break through 

the bark after the tree dies. The fertile conk is thin, resupinate (flattened), with 

a gray to red-brown pore surface. The fertile fruiting body quickly deteriorates 

and is usually difficult to find. 

Incipient decay appears as yellowish white streaks and spots in the wood. 

Wood in advanced decay is white, soft, with fine black zone lines throughout, 

and a mottled appearance on radial surfaces.

Injury: The fungus causes a white trunk rot similar to that caused by Phellinus igniarius. Presence of a conk indicates substantial decay.

Remarks: Infection by this fungus occurs commonly through wounds and 

dead branches. Volume losses from this pathogen may be reduced through 

removal of infected trees, preventing wounds, and shortened rotations. Trees 

with conks could be hazardous and should be carefully evaluated in recreation 

areas. Historically, the fungus has been used as fire starting material and for 

medicinal purposes.

References: 1, 12, 25, 29, 83, 126, 151, 182, 183, 223, 238

Figure 189. Sterile conk of Inonotus 

obliquus on paper birch.

Figure 190. Young cinder conk on birch.

Wood Decays and Stains
188

Birch Conk 

Piptoporus betulinus (Bull.:Fr.) Karst.

(=Polyporus betulinus Bull.:Fr.)

Host: Paper birch.

Distribution: Host range in Alaska.

Identification: Fruiting body is annual, leathery, shelving with or without a 

short lateral stalk. Conks have a distinctive thickened margin, incurved, pro‐

jecting below the lower surface. The upper surface ranges from mouse-colored 

to whitish, yellow-brown or brown. Upper surface may be smooth or broken 

up to give a pitted or scaly appearance. Lower surface is white at first then 

turning yellowish or tan and with thick-walled pores. Interior tissue is firm, 

white, and corky in texture with a distinct pore layer that readily peels off in 

fresh specimens.

Initially both sapwood and heartwood decay is light yellowish-brown, crack‐

ing into cubes with thin white mycelial felts in the cracks. In advanced stages 

the wood is reduced to a fine crumbly mass.

Injury: The fungus causes a brown cubical rot of dead trees and dead portions 

of living trees. After colonization of dead tissues, the fungus may occassion‐

ally spread a short distance into the main stem of living trees. 

Remarks: This fungus was carried on the wrist of Otzi, the 5,000 year old 

man whose body was recovered from ice in Italy in 1991. Historians speculate 

that he consumed the fungus to treat intestinal parasitoids.

References: 1, 12, 29, 83, 126, 182, 184

Figure 191. Piptoporus betulinus conk.

Wood Decays and Stains
189

Rainbow Conk 

Trametes versicolor (L.:Fr.) Pilat. (=Polyporus versicolor L.:Fr.)

Hosts: Hardwoods, occasionally on conifers.

Distribution: Hosts range in Alaska.

Identification: The fruiting body is annual, thin, tough, and leathery. Upper 

surface is hairy and with multicolored zones or bands that vary from white or 

greyish to brownish, blackish, or purple. Lower surface is white with small 

pores. Conk interior is white. 

The early stages of decay are unnoticeable. Wood with advanced decay is 

uniformly white, soft, brittle, and much reduced in weight.

Injury: The fungus causes a white spongy rot of dead hardwood trees, slash, 

stored logs, and wood in service. 

Remarks: Clean, dry and well-aerated conditions or treatment with a preser‐

vative will control the fungus on wood in service.

References: 12, 29, 83, 126, 182

Figure 192. Rainbow conk.

Wood Decays and Stains
190

Blue Stain

Leptographium abietinum (Peck) Wingfl.

Hosts: White, and Sitka spruce, Lutz spruce; likely on black spruce

Distribution: Hosts range in Alaska. 

Identification: Infection results in a grayish, dark blue, or blackish discolor‐

ation of the sapwood. In cross section the discoloration typically appears as 

streaks, irregular areas, or wedge-shaped sectors. Stain patterns occur because 

of colonization of both tracheids and rays in the sapwood. 

Injury: Sapwood discoloration is the principle injury. If conditions remain 

favorable for the fungus, the entire sapwood may become blue-stained. Patho‐

genicity tests suggest that L. abietinum is saprophytic or only weakly patho‐

genic to the host. 

Remarks: Most wood properties are not significantly altered by blue stain 

fungi, thus the wood may be used for many purposes provided the discol‐

oration itself is not objectionable. Since conditions favoring blue stain also 

favor rot development by wood decay fungi, stained wood should be care‐

fully examined for indications of decay. In Alaska, this fungus is commonly 

associated with spruce beetle (D. rufipennis) galleries, however the symbiotic 

association between the beetle and the blue stain fungus is poorly understood.

References: 29, 98, 188, 228, 265

Figure 193. Blue stain of white spruce sapwood.

Wood Decays and Stains
191

Black Stain of Yellow-cedar Heartwood

Sporidesmium sp., Phialophora melinii (Nannfeldt) Conant.

Hosts: Yellow-cedar

Distribution: Southeast Alaska

Identification: Stained patterns in yellow-cedar heartwood are dark colored, 

usually black with a bluish-greenish color. In cross section they appear as arcs 

with a width of about 1-inch. In longitudinal section, they are elongated verti‐

cally. A wood decay is associated with some stained patterns and insect gal‐

leries. Corpses of woodwasp larvae (Sirex sp.), which are believed to transmit 

the fungus to cedar trees, may be found. Tiny wounds are also associated with 

many of the stain pattern.

Injury: The stain can represent a serious reduction in the value of infected 

wood but, unless the associated wood decay is present, the stain may not influ‐

ence the strength of wood. Black stain in heartwood appears to have little to no 

influence on the physiology of the tree. 

Remarks: Sporidesmium, Phialophora melinii, and other fungi have all been 

isolated from stained wood. Sporidesmium is the most consistently isolated 

and its color when grown in culture looks very similar to the green-blue-black 

color of stained wood. Research on the identity of these fungi continues. 

These fungi infect the wood when it is sapwood. As the infected sapwood 

is converted to heartwood, the stain occurs there and is overgrown by new 

sapwood. The causal fungus eventually dies, but the stain persists in the heart‐

wood in crescent shapes with widths equal to the sapwood width (i.e., about 

1 inch). There is some evidence that the stain fungus is vectored to trees by 

woodwasps. The small wounds and insect galleries in stain patterns appear to 

represent feeding by these insects. 

References: 106, 173, 246

Figure 194. Black stain of 

yellow-cedar heartwood.

Wood Decays and Stains
192

Figure 195. Yellow-cedar decline.

Noninfectious Disorders

Disease-like processes which are not caused by living agents (pathogens) and 

which are noninfectious are referred to as abiotic disorders. These problems 

may be caused by many different nonparasitic factors in the environment, such 

as weather, air pollution, deficiencies or excesses of soil minerals, and misuse 

of chemicals. We include animal damage to trees in this section even though 

the causal agent (i.e., the animal) is biotic. In many instances the symptoms of 

abiotic disorders closely resemble those of some parasitic diseases making it 

difficult to determine the cause. Many of the noninfectious injuries serve as an 

entry way for pathogens, such as those that cause cankers and wood decay.

In this section, we have also included forest tree problems (i.e. yellow-cedar 

decline) which are widespread and probably caused by changing climate 

conditions.

Noninfectious Disorders
193

Yellow-Cedar Decline

Affected Trees: Yellow-cedar, also known as Alaska-cedar or Alaska yellowcedar

Distribution: On about 200,000 hectares throughout Southeast Alaska from 

northwestern Chichagof Island to Portland Canal, and also extending about 

161 kilometers south into north coastal British Columbia. 

Identification: Trees are dead or dying in small patches of less than one hect‐

are to expansive areas stretching for several kilometers. Mortality is usually 

associated with boggy (muskeg) conditions. Affected stands have a mixture 

of trees that died long ago, died more recently, are currently dying, and appear 

relatively healthy. On average two thirds of the mature yellow-cedar is dead 

and standing in declining forests. Yellow-cedars that have been dead for up to 

100 years (when the problem began) are often still standing but their bark and 

limbs and all sapwood have deteriorated away. Affected cedars die quickly, 

with their entire compliment of foliage turning red and then brown over 2 or 

3 years, or die slowly (e.g., 15 or more years) with crown slowly thinning and 

terminal foliage the last to die. Cedars with thin or off-green crowns frequently 

have vertical lesions of dead cambium on the lower bole. 

Injury: Yellow-cedar decline appears to represent a form of freezing injury, 

most likely to superficial roots that are forced to grow close to the soil surface 

because of saturated soils (i.e., in boggy and semi-boggy conditions). These 

areas also exibit rapid temperature changes due to less canopy cover. Yellowcedars are cold hardy in fall and early winter, but they deharden in late winter 

and early spring and are then vulnerable to freezing injury. The health of 

yellow-cedar forests is highly associated with snow patterns: forests are dead 

and dying where snow does not protect roots from late winter-early spring 

freezing but forests appear healthy at higher elevations and areas close to the 

mainland in Southeast Alaska where snow persists through March or April. 

Yellow-cedar trees also appear healthy where the mix with western hemlock 

and other tree species on well-drained soils. The organisms (i.e., fungi, insects, 

and nematodes) that are associated with dying cedars lack the capability of 

killing a healthy, unstressed tree. Phloeosinus bark beetles, Armillaria spp., 

and other fungi that are frequently found on dying or recently dead trees have 

been shown to not be the primary cause of tree death. 

Remarks: The early onset of the problem in about 1880 to 1900 in remote, 

relatively pristine sites suggests that yellow-cedar decline may have been initi‐

ated as a natural process at the end of the Little Ice Age. The problem acceler‐

ated in the later half of the 1900s, apparently the result of less snow, extended 

growing season in the spring, and periodic cold events. Death of overstory 

yellow-cedar trees results in plant succession that favors other conifer tree 

Noninfectious Disorders
194

species. Because of the remarkable decay resistance of yellow-cedar wood, the 

recovery of wood from dead yellow-cedars often produces a valuable product. 

Yellow-cedar is a high elevation tree throughout most of its natural range. It 

is no longer adapted to low elevation, wet, open areas with today’s climate. 

Forest management of this valuable tree species can continue with planting 

and thinning in areas where snow persists into spring or on better drained soils 

where roots can grow more deeply. 

References: 48, 88, 108, 112, 113, 115, 116, 118–120, 123–125, 150, 221

Figure 196. A tree that died from yellow-cedar decline.

Noninfectious Disorders
195

Hemlock Fluting

Affected Trees: Western hemlock.

Distribution: Southeast Alaska, most commonly within close proximity to 

beaches.

Identification: Main stems of western hemlock have deeply incised vertical 

grooves and ridges. Grooves appear to originate at dead branches and extend 

vertically down the stem. The occurrence of fluting all the way up boles to the 

live crown of trees distinguishes bole fluting from other characteristics such as 

a flared root collar. Disturbances, rapid growth, and coarse branching of young 

western hemlock are factors that seem to trigger bole fluting.

Injury: Technically, trees are not injured by bole fluting, and fluting may 

contribute to their survival by making them more windfirm. Fluting can 

significantly reduce the economic value of logs because of bark inclusions and 

irregular grain. 

The degree to which hemlock trees are fluted varies with tree age. Fluting can 

begin when trees are about 10 years old and intensify while trees are growing 

rapidly. Flutes generally initiates below branches that decline in growth from 

shading. Flutes from vertically aligned branches coalesce and produce long 

grooves that spiral downward.

With time, as dead branches deteriorate and the bole overgrows the branch 

Figure 197. Hemlock fluting.

Noninfectious Disorders
196

stub, the tree can develop a round bole to the point where flutes are no longer 

visible. These trees may have bark trapped in the internal wood, however.

Remarks: By creating conditions that trigger fluting, thinning western hem‐

lock stands on sites where fluting has been a problem in the past will likely 

exacerbate the problem. Planting or favoring Sitka spruce and other species 

during thinning can help reduce losses. 

References: 147–150

Figure 198. Log end showing deep incisions of hemlock fluting as 

well as hollow caused by heart rot.

Noninfectious Disorders
197

Burls 

Affected Trees: Sitka and white spruce; various hardwoods 

Distribution: Hosts range 

Identification: These globe-shaped, large, woody swellings or growths are 

quite striking and have long been phenomena of interest on plants. Burls occur 

on branches or stems of trees either singly or in groups and may be locally 

abundant. These woody growths apparently originate at a single cell or small 

group of cells near the pith in the first year of growth, and enlarge throughout 

the life of the tree. Burls of spruce can reach enormous proportions, frequently 

larger than the diameter of the stem. Buds or sprouts may develop on the 

surface of a burl. 

Injury: Trees with burls appear to grow normally, with the stem bark gener‐

ally the same color and texture as that of the burled area. Wood from burls is 

usually sound, lacking stain or decay. Recent research suggests that aspen trees 

with woody black stem galls tend to have less stem decay than those lacking 

galls. Research continues on identifying and characterizing inhibitory com‐

pounds produced by the microflora in the galls. 

Remarks: The cause of burls in spruce has not been proven. Possible factors 

include injury from freezing temperatures, mutation, or genetic predisposition 

to burl formation in response to unknown environmental factors. Genetics are 

Figure 199. Large burls on Sitka spruce.

Noninfectious Disorders
198

suspected to be involved as spruce burls tend to be found in patches within a 

localized area or watershed. Large burls on aspen can be induced by the poplar 

budgall mite and are characterized by red mite-containing tissues on the sur‐

face. Other burls of aspen, those that are generally globose with a rough, black, 

fissured surface, have an unknown cause. Burl formation on paper birch and 

other hardwoods is unexplained. Burls on hemlock can be induced by hemlock 

dwarf mistletoe stem infections. The highly figured wood of cut burls is prized 

by fine woodworkers. Alaskans use burled trees as signposts and for a variety 

of home decorative purposes. At the end of the 1,000–mile Iditarod sled dog 

race, mushers and their teams pass under a quentesentially Alaskan burled arch 

in Nome. 

References: 29, 39, 268, 269

Noninfectious Disorders
199

Animal Damage 

Affected Trees: All tree species in Alaska.

Distribution: Throughout tree range in Alaska.

Identification: Severed stems, stripped bark, scratched bark, holes in the 

bark, clipped buds, twigs, and cones, seed and seedling destruction. Most 

injury occurs as a result of the direct feeding by animals, an exception being 

bears sometimes scratching trees. Brown and black bear, moose, porcupine, 

sapsucker (birds), vole, shrew, snowshoe hare, squirrel, and deer cause most of 

the injury in Alaska.

Animal feeding that results in the bark of live trees being removed usually 

leaves teeth marks or grooves on exposed wood. The width of these teeth 

marks can give an indication of which animal is responsible. Grazing by ani‐

mals such as moose, deer, and snowshoe hare leave plants with the appearance 

that lateral and terminal branches been clipped off. 

Injury: The actual injury to plants by animal feeding is quite variable. Seri‐

ous injury occurs when bark is removed from large areas, grazing removes a 

significant amount of the photosynthetic tissues, or seedlings are destroyed. 

Porcupines and bears cause significant damage to trees by creating large bole 

scars or by feeding on the entire circumference the bole. Large wounds are 

colonized by wood decay fungi and complete girdling of stems causes top kill 

or entire tree death. Snowshoe hare feeding can result in death of the terminal 

branch and subsequent decay of the stem.

Remarks: Porcupines damage high value trees, such as crop trees left after 

thinning in Southeast Alaska. In winter, they climb to feed on the inner bark 

along the bole of young trees and feed at the base of large trees (usually 

western hemlock in the latter case). Removing damaged trees before signifi‐

cant decay develops, or favoring species, such as cedars, that pocupines do not 

Figure 200. Large wound at the base of a 

Sitka spruce caused by porcupine feeding.

Noninfectious Disorders
200

prefer, will reduce losses.

Brown bears cause extensive wounding to the boles of yellow-cedar. More 

than one half of the yellow-cedar trees are scarred in some stands on Baranof 

and Chichagof Islands in Southeast Alaska. Scars occur on the lower boles, but 

the entire bole is rarely girdled. They appear as old callusing wounds or fresh 

with detached bark and teeth marks in exposed wood made when brown bears 

pulled bark away. Obvious signs of feeding are not evident on scars; the reason 

that bears scar cedars is not known. 

References: 23, 34, 61, 117, 170, 171, 240, 241

Figure 201. Yellow-cedar tree 

wounded by a brown bear. Note the 

teeth marks in the exposed wood.

Figure 202. Girdling of paper birch 

caused by feeding of red squirrels.

Noninfectious Disorders
201

Other Abiotic Disorders

Winter Drying (Red Belt) and Needle Discoloration

Drought-like conditions in the winter are the cause of winter drying and much 

of the needle discoloration seen in spring. Sudden warm spells or warm winds 

that occur during the winter may cause a marked increase in transpiration, 

killing foliage and buds. If the soil is frozen when this occurs, water is not 

available to replace that which has transpired. Under these circumstances the 

tree reacts as it would in a period of drought and injury is expressed by brown‐

ing and dying of the foliage when warm weather comes in the spring. If the 

warm wind occurs high along the side of the valley the damage is displayed 

as a sharply defined reddish belt of affected trees, thus the common name 

for this phenomena is “red belt.” Fortunately, affected trees are usually not 

permanently damaged. This injury may be difficult to distinguish from direct 

freezing injury to tissues.

Purple to red needle discoloration of conifers is often noticed in spring on 

exposed trees in urban environments. Typically these trees have suffered from 

winter needle dessication. Foliage within unopened buds at the time of warm 

winter winds is usually unaffected and foliage on the sides of trees facing the 

Figure 203. Red belt (winter drying).

Noninfectious Disorders
202

winds will display the greatest damage. Discolored needles could be caused 

by many biotic and abiotic factors including drought, misapplied chemicals, 

infection by needle fungi, root disease agents, and planting trees that are 

poorly adapted trees to Alaskan conditions. Proper diagnosis for the cause 

and control of needle discoloration requires careful observation for signs and 

symptoms of fungal infection (i.e fruiting bodies on the underside of needles 

or on twigs). Without signs of biotic agents, the damage is typically attributed 

to abiotic influences. 

Drought 

Drought conditions occur whenever soil moisture drops below the level 

required by trees. Chronic injury results from long-term exposure to low 

water supplies and is expressed by growth loss and increased susceptibil‐

ity to parasitic fungi and insects. Chronic injury can be difficult to diagnose. 

Acute injury occurs when an extreme water deficiency occurs and is expressed 

by significant growth loss or death. Symptoms of drought damage include 

wilting, discoloration of foliage, premature leaf fall, death of tree from top of 

crown down and outside of crown in. The roots are usually the last portion to 

die. Symptoms can be similar to trees suffering root disease, except roots die 

before the foliage for trees with root disease.

Freezing Injury 

Death of foliage, buds and twigs, leading to a growth loss and a general weak‐

ening of the tree, may occur as the result of either an early (fall) or late (spring) 

frost. Injury in mid-winter is less frequent because tissues are often resistant 

to temperatures below record lows and dehardening is governed largely by 

photoperiod (i.e., daylength). Early frost injury takes place before the trees 

are hardened for the winter, but this form of damage is not as common as late 

Figure 204. Modest 

and severely drought 

stressed alder 

foliage.

Noninfectious Disorders
203

Figure 205. Freezing injury of spruce.

Figure 207. Frost damage on the tips 

of Sitka spruce foliage.

Figure 206. Yellow-cedar seedling with 

frost damage.

winter or spring damage. Spring frosts causing foliar injury are particularly 

common in conifers. Needles in exposed areas or on one side of the tree are 

killed when they experience warm weather, deharden and lose cold tolerance, 

and are then injured during subsequent cold weather. Young, newer foliage 

(e.g., produce the prior year) is often more vulnerable to this injury than older 

foliage. The actual damage is a result of intercellular and/or intracellular 

formation of ice crystals that cause cellular deformation and death. Injury can 

be sudden and acute, perhaps occurring during one day at dusk during a rapid 

transition from the warmth of day to the cold of night. 

Noninfectious Disorders
204

Windthrow

Single trees or patches of trees are uprooted with full root plates or broken off 

at the bole as the result of strong winds. Windthrown trees in patches often lie 

parallel to one another in the same direction as the windstorm. Old-growth 

hemlock-spruce forests in Southeast Alaska are particularly susceptible, 

where damage most commonly occurs in the fall or winter months. Heavy 

rains which saturate soils accompany gale-force southerly winds contribute to 

windthrow at that time. Many of the patches of windthrown trees that are now 

visible resulted from one storm on November 28, 1968. Storms in the 1880s 

gave rise to many even-aged forests in Southeast Alaska. Most windthrow is 

not associated with human activity, but patches of windthrown trees on the 

perimeters of clearcutting units are common, particularly on the leeward side 

or in V-shaped or square corners of clearcuts. In Southeast Alaska, windthrow 

is commonly associated with south-facing slopes, productive soils, and low 

elevations—all conditions which support tall old-growth trees. Root and stem 

rot increases the incidence of wind damage. During strong winds, trees with 

stem decay tend to snap while trees with root disease tend to uproot with only 

a minor complement of roots attached.

Sulfur Dioxide Emissions

Emissions of chemical pollutants in the form of gases from industrial plants, 

including SO2

, can damage trees. Chronic injury, which results from continued 

low level emissions of noxious gases, is expressed as a general yellowing of 

trees and growth loss. On conifers, the internodes and terminals are shorter and 

the needles are smaller with a shorter life and retention. On broad-leaved trees, 

the leaves are discolored with irregular flecks and patches before becoming 

entirely yellowish. Acute injury occurs when a tree is exposed to high concen‐

Figure 208. Windthrow.

Noninfectious Disorders
205

Figure 209. Damage to western hemlock 

foliage by sulfur dioxide emissions.

trations of noxious gases. Needles on conifers with acute injury first appear 

water-colored then turn tan or reddish-brown as the tissue dies. Either the 

entire needle or just the distal portion may be affected. On broad-leaved trees 

the leaf margins are affected first then the tissue between the veins. In many 

instances all of the leaf tissue with the exception of the veins may be killed. 

References: 1, 29, 99, 126, 143, 161, 178

Noninfectious Disorders
206

Index to Pathogens by Host 

Plants

Alder (Alnus spp.)

 Diseases

Valsa canker (Valsa melanodiscus)..................................................................148 

Rough bark of alder (Didymosphaeria oregonensis).....................................151

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Artist’s conk (Ganoderma applanatum).........................................................169

Oyster mushroom (Pleurotus ostreatus).........................................................182

False tinder conk (Phellinus igniarius)............................................................185

Rainbow Conk (Trametes versicolor).............................................................189

Aspen, Quaking (Populus tremuloides Michx.)

 Diseases

Hardwood leaf rust (Melampsora medusae)..................................................129

Shepherd’s crook disease (Venturia macularis).............................................137

Cytospora canker (Cytospora chrysosperma)................................................148

Sooty bark canker (Encoelia pruinosa)...........................................................148

Ceratocystis canker (Ceratocystis fimbriata).................................................148

Cryptosphaeria canker (Cryptosphaeria lignyota)........................................148

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Artist’s conk (Ganoderma applanatum).........................................................169

Yellow cap mushroom (Pholiota spp.)............................................................176

Oyster mushroom (Pleurotus ostreatus).........................................................182

False tinder conk (Phellinus tremulae)............................................................185

Rainbow Conk (Trametes Versicolor).............................................................189

Birch, Paper (Betula papyrifera Marsh.)

 Diseases

Leaf Rust (Melampsoridium betulinum)........................................................129

Nectria Canker (Nectria galligena).................................................................148

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Pinicola conk (Fomitopsis pinicola)................................................................163

Artist’s conk (Ganoderma applanatum).........................................................169
207

Yellow cap mushroom (Pholiotaspp.)............................................................176

Oyster mushroom (Pleurotus ostreatus).........................................................182

Tinder conk (Fomes fomentarius)....................................................................184

False tinder conk (Phellinus igniarus).............................................................185

Cinder conk (Inonotus obliquus).....................................................................187

Birch conk (Piptoporus betulinus)..................................................................188

Rainbow conk (Trametes versicolor)..............................................................189

Cedar, Yellow- (Chamaecyparis nootkatensis (D. Don) Spach.)

 Diseases

Yellow-cedar shoot blight (Apostrasseria sp.)...................................136

Yellow-cedar decline .......................................................................................193

 Decays and Stains

Armillaria root disease (Armillaria spp.)........................................................155

Black stain of yellow-cedar heartwood ..........................................................191

Cedar, Western Red (Thuja plicata Donn)

 Diseases

Cedar leaf blight (Didymascella thujina)........................................................130

 Decays

Armillaria root disease (Armillaria spp.) ........................................................155

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)...............................................................163

Redcedar white ring rot (Ceriporiopsis rivulosa)...........................................179

Yellow ring rot (Phellinus weirii)....................................................................180

Cedar Brown Cubical Pocket Rot (Postia sericeomollis)................181

Cottonwood, black (Populus trichocarpa Torr. & Gray)

 Diseases

Hardwood leaf rust (Melampsora medusae)..................................................129

Cytospora canker (Cytospora chrysosperma)................................................148

Cryptosphaeria canker (Cryptosphaeria lignyota)........................................148

 Decays

Chicken of the woods (Laetiporus sulphureus)..............................................165

Artist’s conk (Ganoderma applanatum).........................................................169

Yellow cap mushroom (Pholiota spp.)............................................................176

Oyster mushroom (Pleurotus ostreatus).........................................................182

False tinder fungus (Phellinus tremulae)........................................................185

Cinder conk (Inonotus obliquus).....................................................................187

Rainbow conk (Trametes versicolor)..............................................................189
208

Hemlock, Mountain (Tsuga mertensiana (Bong.) Carr.)

 Diseases

Hemlock needle rust (Melampsora epitea f. sp. tsugae)................................128

Sirococcus shoot blight (Sirococcus tsugae)..................................................134

Hemlock dwarf mistletoe (Arceuthobium tsugense)......................................138

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Chicken of the woods (Laetiporus sulphureus)..............................................165

Indian paint fungus (Echinodontium tinctorium)...........................................171

Hartig’s conk (Phellinus hartigii)....................................................................173

Borealis conk (Climacocystis borealis)...........................................................174

Coniophora brown rot (Coniophora spp.)......................................................177

Hemlock, Western (Tsuga heterophylla (Raf.) Sarg.)

 Diseases

Hemlock needle rust (Naohidemyces vaccinii)..............................................128

Sirococcus shoot blight (Sirococcus tsugae)..................................................134

Hemlock dwarf mistletoe (Arceuthobium tsugense)......................................138

Hemlock cankers (Xenomeris abietis, Discocainia treleasii).......................146

Fluting of hemlock...........................................................................................195

 Decays

Annosus root and butt rot (Heterobasidion annosum)...................................152

Armillaria root disease (Armillaria spp.)........................................................155

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Chicken of the woods (Laetiporus sulphureus)..............................................165

Velvet top fungus (Phaeolus schweinitzii)......................................................167

Artist’s conk (Ganoderma applanatum).........................................................169

Lacquer conk (Ganoderma tsugae)................................................................170

Borealis conk (Climacocystis borealis)...........................................................174

Quinine conk (Fomitopsis officinalis).............................................................172

Hartig’s conk (Phellinus hartigii)....................................................................173

Purple conk (Trichaptum abietinus)................................................................175

Yellow cap mushroom (Pholiota spp.)............................................................176

Coniophora brown rot (Coniophora spp.)......................................................177

Coral fungus (Hericium abietis)......................................................................183
209

Pine, Shore (Pinus contorta Dougl.)

 Diseases

Western gall rust (Peridermium harknessii )...................................................144

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Quinine conk (Fomitopsis officinalis).............................................................172

Poplar, Balsam (Populus balsamifera L.)

 Diseases

Hardwood leaf rust (Melampsora spp.)..........................................................129

Shepherd’s crook (Venturia populina)............................................................137

Cytospora canker (Cytospora chrysosperma)................................................148

Cryptosphaeria canker (Cryptosphaeria lignyota)........................................148

Sooty bark canker (Encoelia pruinosa)...........................................................148

 Decays

Armillaria root disease (Armillaria spp.)........................................................155

Rainbow conk (Trametes versicolor)..............................................................189

Spruce, Black (Picea mariana (Mill.) B.S.P.)

 Diseases

Spruce needle rust (Chrysomyxa ledicola).....................................................125

Spruce needle blight (Lirula macrospora, Lophodermium picea, 

 Rhizosphaera pini)..............................................................................131

Spruce broom rust (Chrysomyxa arctostaphyli).............................................142

 Decays and Stains

Tomentosus root rot (Inonotus tomentosus)....................................................157

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Coniophora brown rot (Coniophora spp.)......................................................177

Blue stain (Leptographium abietinum)...........................................................190

Spruce, Sitka (Picea sitchensis (Bong) Carr.)

 Diseases

Spruce needle rust (Chrysomyxa ledicola)....................................................125

Spruce needle blight (Lirula macrospora, Lophodermium picea, 

 Rhizosphaera pini)..............................................................................131

Sirococcus shoot blight (Sirococcus tsugae)..................................................134

Hemlock dwarf mistletoe (Arceuthobium tsugense)......................................138

Spruce broom rust (Chrysomyxa arctostaphyli).............................................142
210

Cankers of spruce (Discocainia treleasii, Botryosphaeria picea, 

 Aleurodiscus sp.)...............................................................................146

 Decays and Stains

Annosus root and butt rot (Heterobasidium annosum)..................................152

Armillaria root disease (Armillaria spp.)........................................................155

Tomentosus root rot (Inonotus tomentosus)....................................................157

Pini conk (Phellinus pini).................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Chicken of the woods (Laetiporus sulphureus)..............................................165

Velvet top fungus (Phaeolus schweinitzii)......................................................167

Artist’s conk (Ganoderma applanatum)........................................................169

Quinine fungus (Fomitopsis officinalis)..........................................................172

Borealis conk (Climacocystis borealis)...........................................................174

Purple conk (Trichaptum abietinus)................................................................175

Yellow cap mushroom (Pholiota spp.)............................................................176

Coniophora brown rot (Coniophora spp.)......................................................177

Coral fungus (Hericium abietis)......................................................................183

Blue stain (Leptographium abietinum)...........................................................190

Spruce, White (Picea glauca (Moench) Voss)

 Diseases

Spruce needle rust (Chrysomyxa ledicola).....................................................125

Spruce needle blight (Lirula macrospora, Rhizosphaera pini, 

 Lophodermium picea)...........................................................................131

Spruce broom rust (Chrysomyxa arctostaphyli).............................................142

 Decays and Stains

Armillaria root disease (Armillaria spp.)........................................................155

Tomentosus root rot (Inonotus tomentosus)....................................................157

Pini conk (Phellinus pini)................................................................................160

Pinicola conk (Fomitopsis pinicola)................................................................163

Velvet top fungus (Phaeolus schweinitzii)......................................................167

Artist’s conk (Ganoderma applanatum )........................................................169

Quinine fungus (Fomitopsis officinalis ).........................................................172

Purple conk (Trichaptum abietinus)................................................................175

Yellow cap mushroom (Pholiota spp.)............................................................176

Coniophora brown rot (Coniophora spp.)......................................................177

Blue stain (Leptographium abietinum)...........................................................190
211

Willow (Salix spp.)

 Diseases

Hardwood leaf rust (Melampsora epitea).......................................................129

Cytospora canker (Cytospora chrysosperma)................................................148

 Decays

Artist’s conk (Ganoderma applanatum )........................................................169

False tinder fungus (Phellinus igniarius)........................................................185
212

Glossary

Abdomen: Posterior part of the insect’s main body divisions.

Abiotic disorder: Interference of the normal functioning of a plant that is 

caused by some non-living factor (e.g., weather) and not by an organism 

(pathogen or insect); symptoms may be similar to true disease. Weak patho‐

gens may be present.

Adult: Full‐grown, sexually mature insect; usually with wings in contrast to 

larvae which lack wings. 

Alternate host: One of the two dissimilar plants infected by a heterocyclic 

fungus, i.e., some rust fungi.

Arthropod: Largest phylum in the animal kingdom including insects, crabs, 

spiders, etc. 

Blind conk: An overgrown knot filled with old conk material or the beginning 

of a new conk, also called punk knot, reliable indicator of the presence of some 

wood decay fungi, i.e., Phellinus pini.

Brown Rot: Brownish, dry, crumbly decay of wood, caused by fungi 

decomposing cellulose and leaving the lignin in a modified state; may occur in 

areas surrounded by sound wood. Decayed wood typically brakes into cubical 

shapes.

Boring‐dust: Reddish‐brown to tan, pulverized bark excavated by the adult 

bark beetle as it bores through the outer bark; often found in small piles in bark 

crevices and around base of tree.

Callus: Healing tissue of trees on branches, boles, or roots that attempt to 

grow over scars or wounds.

Cambium: Layer of cells between xylem and bark, forms additional xylem 

and phloem elements.

Canker: Localized, dead, sometimes sunken, portion of the cambium and 

bark of branches or the bole of a tree, often caused by a pathogen. Many layers 

of dead callus folds surround some cankers as the tree repeatedly attempts to 

heal the dead portion, only to have the pathogen kill the callus folds.

Chlorosis: (adj. chlorotic) An unseasonable yellowing of the foliage, may 

occur in bands on needles.

Conk: Fruiting body of a wood‐attacking fungus, often hoof or brack‐

et‐shaped and perennial, although some are annual; other than a mushroom.

Context: Interior tissue of a fruiting body.
213

Cornicle: Dorsal tubular processes on the posterior portion of the abdomen; 

common on aphids. 

Cortex: Rind or outer layer.

Crop tree: Tree left after thinning, often because of superior quality or species 

and lacking defect or disease.

Decay: Rot, destruction or decomposition of plant material by fungi, typi‐

cally separated into brown or white rot depending on the wood compounds 

consumed. 

Dioecious: Male flowers and female flowers on different individual plants, as 

in hemlock dwarf mistletoe.

Disease: A disturbance of a plant caused by a pathogen (not an insect) that 

interferes with the plant’s normal growth, structure, or reproduction. See also 

abiotic disorder.

Endemic: typical, non-epidemic population

Endophytic: An organism living within tissues of a live plant.

Epidemic: Large scale temporary increase in an insect or disease population.

Fecundity: Ability to produce young.

Flag: Dying or recently dead branch contrasting in color with the normal 

green color of a living tree.

Frass: Solid insect excrement, usually in small pellets; many times mixed 

with boring dust.

Fruiting Body: A general term for any fungal spore‐producing structure. See 

also conk or mushroom.

Fungus: (plural = fungi) An organism incapable of producing its own food 

supply by photosynthesis, usually having microscopic thread‐like feeding 

structures (hyphae) and reproductive spores. Most tree diseases, especially of 

conifers, are caused by fungi.

Galls: An abnormal growth of plant tissue, stimulated by insect or fungal 

activity.

Genus: A group of closely related species. Similar genera are grouped in a 

family.

Girdle: The act of damaging the cambium completely around the circumfer‐

ence of the stem, root or branch, typically causing death of the tree or tissue 

beyond the point of girdling.

Gregariously: Insects tending to feed or remain in groups.

Grub: Thick‐bodied larva, usually sluggish, good fishing bait.
214

Heartwood: Central mass of tissue in tree trunks, with no living cells and no 

longer functioning in water conduction; contributes to mechanical support. 

Heart Rot: Decay, typically caused by fungi, that is characteristically con‐

fined to the heartwood

Heterocyclic: Fungi that requires two different hosts to complete their life‐

cycle; i.e., some rust fungi.

Honeydew: Sugary liquid excretion of aphids or scale insects.

Instar: The stage of an insect between successive molts.

Lanceolate: Spear‐shaped, tapering at each end.

Larva: Immature form of an insect such as a caterpillar, grub, or maggot.

Molt: Process of shedding the exo‐skeleton, the insect “skin.”

Monogamous: Mating with only one individual.

Mushroom: Fleshy fruiting body of a fungus, may have gills or pores.

Mycangia: Structure found on some insects used for the transportation of 

symbiotic fungi from one host to another.

Mycelium: (hyphae) The vegetative feeding structure of a fungus.

Mycelial Fan: a fan shaped mycelial mat forming under the bark and wood of 

roots or lower trunks; often associated with Armillaria spp.

Mychorrhizae: Association between plant rootlets and specialized fungi that 

are beneficial to their tree associate by assisting in nutrient and water uptake.

Necrotic: Dead plant cells or tissues.

Nuptial Chamber: Mating site.

Nymph: Immature form of an insect resembling the adult except for incom‐

plete wing development.

Obligate Parasite: An organism capable of existing only as a parasite on a 

live host.

Oviposit: Lay or deposit eggs.

Ovipositor: Egg‐laying apparatus.

Parasite: An organism living in or on, and getting its food from, a live host. 

May be harmful (i.e., pathogen) or beneficial (e.g., mycorrhizae)

Parthenogenetic: Reproducing by eggs that develop without being fertilized.

Pathogen: An organism or virus capable of causing disease on a host. Most 

pathogens of forest trees are fungi.

Perennial: Lasting for several years or more.
215

Perfect Stage: The stage of the life cycle of a fungus where spores are formed 

during sexual reproduction (meiosis).

Pheromone: Chemicals which are produced by one individual to affect or 

alter the behavior of another individual of the same species.

Phloem: Vascular tissue that conducts synthesized foods through the plant, 

located adjacent to the outside of the cambium in trees, essentially the inner 

bark.

Pitch‐Tubes: A tubular mass of cream colored resin mixed with bark, wood 

borings, and insect excrement that forms on the surface of the bark at beetle 

entrance holes.

Plumed: Feather‐like.

Polygamous: Mating with several individuals

Pronotum: The dorsal plate of the prothorax.

Prothorax: The anterior of the three thoracic segments. 

Pupa: Inactive stage of an insect; transitional stage from larva to adult.

Radial Growth: One‐half the diameter growth of a tree.

Rain forest: Forest in which factors other than fire are the main catastrophic 

disturbance forces.

Rhizomorph: a cord‐like structure of some fungi, i.e., Armillaria spp., com‐

posed of white hyphae and often covered by a black rind.

Rot: deterioration of organic material through the enzymatic activity of micro‐

organisms; decay.

Rust: A disease caused by one of the rust fungi, highly specialized pathogens 

that are obligate parasites, frequently require two different types of hosts to 

complete their life cycles (heterocyclic), and produce orange, yellow, or brown 

spores.

Saprophyte: An organism living in and getting its food from dead organic 

material.

Sapwood: Outer region of xylem of tree trunks, containing some living cells 

and functioning in water conduction, food storage and mechanical support.

Serrate: Saw‐toothed edge.

Slash: Debris such as logs, bark, branches left after cutting timber.

Spore: A microscopic reproductive body of a fungus used for dissemination.

Sporophore: Fruiting body of a fungus that produces spores (i.e., mushroom 

or conk).

Stomata: Breathing pore in the epidermis (outer layer) of a plant.
216

Sub‐cortical: Below the bark.

Symbiotic: An intimate association between two species which benefits both.

Systemic: Throughout the plant host tissues, usually surviving from year to 

year.

Terminal Growth: Height growth of a tree.

Terpenes: Unsaturated hydrocarbons occurring in plant oils and resins, 

common in conifers.

Thorax: The body region of an insect behind the head, which bears the legs 

and wings.

White Rot: White to tan decayed wood, caused by fungi decomposing both 

lignin and cellulose; may occur in areas surrounded by sound wood. Decayed 

wood is often fibrous or spongy in texture, and may contain distinctive pock‐

ets. In advanced stage, may create a large hollow in a tree.

Windthrown: Trees uprooted by wind. The term sometimes is applied to 

trees whose stems are snapped by the wind.

Witches’ Brooms: Abnormal proliferations of shoots or branches caused by a 

pathogen (e.g., from dwarf mistletoe).

Xylem: Vascular tissue that conducts water and mineral salts, taken in by 

roots, throughout the plant, essentially the woody part of the stem or trunk. 

Zone Line: Black to brown lines in decaying wood formed by fungi.
217

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Appendix

Submitting Insects and Diseases for 

Identification

People interested in obtaining positive identification of insect and disease 

specimens should submit samples to specialists. The following procedures for 

the collection and shipment of specimens should be followed.

Specimen Collection:

• Adequate material should be collected. Collect both healthy and injured 

material. 

• Adequate Information: The value of an insect or disease specimen 

depends on the information regarding its collection. 

• Where the specimen was collected; nearest post office or town, eleva‐

tion, aspect.

• When the specimen was collected.

• Who collected the specimen.

• Host description (age, species, and general appearance).

• General condition of the surrounding area (fire, blowdown, logging, and 

so forth).

• Personal opinion of the problem: the collector’s opinion can be very 

helpful.

Shipment of Specimens:

• General: Pack specimens in such a manner that breakage will be mini‐

mal.

• Insects: Specimens sent through the mail should be packed to withstand 

rough treatment.

• Larvae and other soft‐bodied insects should be shipped in small 

screw‐top vials or bottles containing at least 70 percent isopropyl (rub‐

bing) alcohol. Make certain that the bottles are sealed well. Include in 

each vial adequate information, or a code, relating the sample to the 

written description and information. Labels inserted in the vial should 

be written on with pencil or India ink. Do not use ballpoint pen.

• Pupae and hard‐bodied insects can be shipped either in alcohol or in 

small boxes. Specimens should be placed between layers of tissue paper 

in the shipping boxes. Pack carefully and make certain that there is 
237

very little movement of material within the box. Do not pack insects in 

cotton. 

• Adult moths, butterflies and fragile insects should be folded between 

paper before packing in the tissue paper. 

• Conks or mushrooms: ship immediately or air‐dry thoroughly, then ship.

• Needle Diseases: Do not ship in plastic bags. Sprinkle lightly with water 

before wrapping in newspaper.

Shipping:

• Ship as quickly as possible. If samples can’t be shipped as soon as pos‐

sible, store them in a refrigerator.

• Include address inside shipping carton.

• Mark “Fragile: Insect—Disease Specimens Enclosed” and “For Scien‐

tific Purposes Only—No Commercial Value.”

• Specimens from Alaska should be sent to:

 Anchorage:

 Forest Health Protection

State and Private Forestry, U.S. Forest Service

3301 “C” Street, Suite 202 

Anchorage, AK 99503–3956

 Juneau:

 Forest Health Protection

State and Private Forestry, U.S. Forest Service

2770 Sherwood Lane, Suite 2A

Juneau, AK 99801–8545

Fairbanks:

 Forest Health Protection

State and Private Forestry, U.S. Forest Service

3700 Airport Way

Fairbanks, AK 99709
238

Photography and Illustration 

Credits

Figures 1–3, 6, 11, 14–18, 20, 23, 25, 26, 31–33, 37–39, 42, 44, 45, 47–50, 52, 

54, 55, 57, 59–65, 67, 68, 72–76, 78, 80, 86–88, 90, 92–95, 98, 99, 101, 

102, 105, 109–115, 117–119, 121–124, 126–131, 133–142, 144, 148, 150, 

152–156, 158–171, 173, 174, 177–179, 182–191, 193–209: U.S. Forest 

Service photographs and illustrations, Alaska Region.

Figure 4: Courtesy of Alaska Department of Natural Resources, Division of 

Forestry

Figures 5, 43: Douce, G.K. and others. 1999. Forest Pest of North America. 

Integrated Pest Management Photo CD Series. Bugwood and the 

University of Georgia Cooperative Extension Service.

Figure 7: Courtesy of U.S. Forest Service, Washington D.C., photo files.

Figures 8, 9, 84: Scratchboards and figures adapted from: Rose, A.H. and O.H. 

Lindquist. 1973. Insects of Eastern Pines. Dept. of the Environment, Can. 

For. Serv. Pub. No. 1313, 128 p.

Figures 10, 106: Scratchboards adapted from: Borror, D.J. and D.M. DeLong. 

1964. An Introduction to the Study of Insects. Holt, Reinhard, Winston, 

N.Y. 819p.

Figures 12, 28, 100, 151: Courtesy of Canadian Forestry Service, Victoria, 

B.C.

Figures 13, 19: Courtesy of Eric LaGasa, WA State Dept. of Ag.

Figures 21, 22, 56, 58: Courtesy of the Great Lakes Forest Research Center, 

Sault Ste. Marie, Ontario.

Figures 24, 30, 34: Courtesy of Mary Hopson, www.turtlepuddle.org.

Figures 27, 35, 36: Courtesy of John Davis, bugguide.net.

Figure 29: Courtesy of Mike Conti, UAF Cooperative Extension Service.

Figures 40, 89: Courtesy of Dr. Warren Johnson, Cornell Univ., Ithaca, N.Y.

Figure 41: Courtesy of U.S. Forest Service—Alaska Archive, Bugwood.org.

Figures 46, 91: Courtesy of Michael Rasy, UAF Cooperative Extension 

Service.

Figure 51: Courtesy of Connecticut Agricultural Experiment Station Archive, 

Connecticut Agricultural Experiment Station, Bugwood.org.

Figure 53: Scratchboard adapted from: Borror, D.J. and R.E. White. 1970. A 

Field Guide to the Insects of North America North of Mexico. Peterson 

Field Guide Series. 404 p.
239

Figures 66, 104: Courtesy of Clemson University—USDA Cooperative 

Extension Slide Series, Bugwood.org.

Figures 69, 70: Scratchboard adapted from: Grant, T. and C.B. Cottrell. 1964. 

Spruce Beetle in British Columbia. For. Pest Leafl. No. 13, For. Res. Ctr., 

Can. For. Serv., Victoria, B.C., 7 p.

Figures 71, 81: Courtesy of Steve Valley, Oregon Department of Agriculture.

Figure 77: University of Georgia, Athens, GA.

Figure 79: Courtesy of Milan Zubrick, Forest Research Institute—Slovakia, 

Bugwood.org.

Figures 82, 83: Courtesy of Mal Furniss, University of Idaho, Moscow, ID.

Figure 85: Courtesy of Whitney Cranshaw, Colorado State University, 

Bugwood.org.

Figures 96, 97: Solomon, J.D. 1995. Guide to Insect Borers in North American 

Broadleaf Trees and Shrubs. U.S. Forest Service Agric. Handbook AH706. 735 p.

Figure 103: Scratchboard adapted from: Ruppel, D.H. 1974. Carpenter Ants. 

For. Pest Leafl. No. 58, For. Res. Ctr., Can. For. Serv., Victoria, B.C. 7 p.

Figures 107, 108: Scratchboards adapted from: Anderson, R.F. 1966. Forest 

and Shade Tree Entomology. J. Wiley and Sons, Inc., N.Y. 428 p.

Figure 116: Courtesy of Malcolm Storey, www.bioimages.org.uk.

Figure 120: Courtesy of Petr Kapitola, State Phytosanitary Administration, 

Bugwood.org.

Figure 125: Courtesy of Robert H. Armstrong, Juneau, AK.

Figure 132: Courtesy of Hillary Hennon, Juneau, AK.

Figure 143: Courtesy of Rocky Mountain Research Station/Forest Pathology 

Archive, U.S. Forest Service, Bugwood.org.

Figures 145, 149: Courtesy of Charles Shaw III, U.S. Forest Service, 

Prineville, OR.

Figures 146, 147, 172: Courtesy of U.S. Forest Service, Region 6, Forest 

Health Protection Archives.

Figure 157: Courtesy of Robert Ott, Bennington,VT.

Figures 175, 176: Courtesy of Joseph LaForest, University of Georgia, 

Bugwood.org.

Figures 180, 181: Courtesy of Eric Allen, Canadian Forest Service, Pacific 

Forestry Centre, Victoria, B.C.

Figure 192: Courtesy of Joseph O’Brien, U.S. Forest Sevice, Bugwood.org.
240

Acarina, 69

Acariformes, 70

Acleris gloverana, 24

Acmaeops p. proteus, 90

Adelges

abietis, 60, 63

cooleyi, 60, 62

tsugae, 62, 63

Adelgidae, 60, 62

Agrilus anxius, 93

Air pollution, 192

Alder 

striped alder sawfly, 50 

woolly sawfly, 51

rough bark of, 151

Aleurodiscus sp., 146

Ambrosia beetles, 86, 95, 96

Animal damage, 124, 192, 199

Annosus root disease, 152

Anthomyiidae, 107

Ants, carpenter, 109–112

Aphid(s), 57-65 

birch, 65

gall, 60, 61, 63

giant conifer, 59

spruce, 57, 58

spruce gall, 60, 61

woolly, 62

Aphididae, 23, 57, 59, 65

Aphrophora sp., 68

Apiosporina morbosum, 15

Apostrasseria sp., 136

Arceuthobium tsugense, 138

Arctiidae, 23, 41

Arhopalus productus, 90

Armillaria root disease, 155

Armillaria spp., 155, 156, 193

Artist’s conk, 169

Aspen leaf miner, 42

Bears, damage by, 124, 199, 200

Bee, carpenter, 112

Beetle(s) 

ambrosia, 86, 95, 96, 

leaf, 23, 52 

long-horned, 15, 16, 86, 87

powder post, 113

Beetles, bark, 71–85

 cedar bark, 82, 156

Dryocoetes sp., 84

engraver, 78–80

four-eyed, 83

hemlock hylesinus, 81

infestation, 21, 27, 62, 77, 78, 82, 93, 96, 

114, 126, 129

larch, eastern, 48, 77

spruce, 73–76

willow bark, 86

Birch aphid, 65

Birch conk, 188

Birch leaf miner, 45

Black knot, 15

Black sooty mold, 59

Black stain, 95, 96

Black stain, yellow-cedar heartwood, 191

Black stem gall, 197

Black-headed budworm, 10, 24, 47

Blight 

Cedar leaf, 130

Sirococcus shoot, 134

Spruce needle, 131

Yellow-cedar shoot, 136

Blue stain, 190

Boreal forests, 11, 12

Borealis conk, 174

Borer

bronze birch, 93

clearwing birch, 97, 98

fir, flat-headed, 91, 92

flat‐headed or metallic, 86, 91, 92, 

round-headed or long-horned beetle,

 15, 16, 86, 87, 92

Botryosphaeria picea, 146

Bronze birch borer, 93, 94

Broom, witches’, 140

Brown cubical rot, 164, 166, 172, 177, 188

Bud and shoot insects, 53–55

Budmoth

larch, 55

spruce, 55

Budworm,

black‐headed, 10, 24, 47

GENERAL INDEX

This index provides access to information in the manual. 
241

spruce, 26, 27, 104

Buprestidae, 86, 91–94, 

Buprestis nuttalli, 94

Burls, 140, 141, 197, 198

Butterfly, mourning cloak, 38

Callidium cicatricosum, 90

Camponotus herculeanus, 110

Cankers,

Spruce and hemlock, 146

Hardwoods, 148

Carpenter ants, 20, 109–112

Carpenter bees, 112

Cecidomyiidae, 54, 66, 106, 108

Cedar bark beetle, 82

Cedar leaf blight, 130

Cedar, yellow- decline, 156, 192, 193 

Cedar, yellow-gall midge, 108

Cenangium singulare, 148

Cerambycidae, 86–90

Ceratocystis fimbriata, 148, 150

Cercopidae, 68

Ceriporiopsis rivulosa, 179

Chamaediplosis nootkatensis, 108

Chicken of the woods, 165, 166

Choristoneura

biennis, 26

conflictana, 28

fumiferana, 26, 104

orae, 26

Chrysobothris trinervia, 94

Chrysomela

falsa, 52

interrupta, 52

walshi, 52

Chrysomyxa

arctostaphyli, 142, 143

ledicola, 125–127

weirii, 126, 127

Cinara sp., 59

Cinder conk, 187

Clearwing birch borer, 97, 98

Climacocystis borealis, 174

Climatic conditions, 22, 73, 109

Coccidae, 64

Coleoptera, 23, 52, 73, 77, 78, 82–85, 

87–89, 91–93, 96, 113

Cone and seed insects, 103–108

Cone-axis, spruce, 103, 106

Cone maggot, spruce, 103, 107

Coneworm, spruce, 27, 103, 104

Coniophora brown rot, 177

Coniophora

arida, 177

olivacea, 177

puteana, 177

Controls, 33, 47, 112, 144

preventive measures, 80, 114

Coral fungus, 183

Cottonwood leaf beetle, 52

Cryptosphaeria populina, 148

Curculionidae, 73–85, 96

Cydia youngana, 105

Cytospora chrysosperma, 148

Dasineura

canadensis, 106

rachiphaga, 103, 106

Defoliators, 21–52

Dendroctonus sp. 71

rufipennis, 71, 73

simplex, 77

Diamond willow, 149

Didymascella thujina, 130

Didymosphaeria oregonensis, 151

Dioryctria reniculelloides, 27, 103, 104

Diprionidae, 23, 46

Diptera, 54, 66, 103, 106–108

Discocainia treleasii, 146

Disease (general discussion), 123–124

Drought, 77, 78, 201, 202

Dryocoetes sp., 84

Dwarf mistletoe, 10, 123, 138–143, 173, 

198

Eastern larch beetle, 77

Echinodontium tinctorium, 171

Ectropis crepuscularia, 37

Elaphidion sp., 90

Elatobium abietinum, 57

Encoelia pruinosa, 148, 149

Endocronartium harknessii, 144

Engraver, 78, 79,80

Epinotia solandriana, 30, 31

Ericosoma sp., 65

Eriocampa ovata, 51

Eriophyes spp., 70

Eriophyid mites, 70

Eriophyidae, 70

Euceraphis betulae, 65

False tinder conk, 185

Fenusa pusilla, 45

Fire, 11, 12, 39, 43, 71, 91, 77, 78, 101,102 

123, 148, 184, 187
242

Flat-headed fir borer, 91, 92

Fluting, hemlock, 195, 196

Foliar diseases, 125–133

Fomitopsis

officinalis, 166, 172

pinicola, 152, 159, 163, 164

Fomes

annosus, 152

fomentarius, 184

hartigii, 173

igniarius, 185

laricis, 172

officinalis, 172

pini, 160

pinicola, 163

Forest dynamics, 123

Forests of Alaska, 11

Formicidae, 110

Four-eyed bark beetle, 83

Frost injury, 136, 202

Gall(s) 

aphid, spruce, 60. 63

hardwood, insects, 66

rust, western, 144, 145

midges, spruce, 106

midge, yellow-cedar, 108

Ganoderma

applanatum, 169

tsugae, 170

oregonense, 170

Geometridae, 22, 23, 32, 34, 36, 37

Ghost moths, 86, 99, 100

Giant conifer aphid, 59

Gnathacmaeops pratensis, 90

Gracillariidae, 23, 42, 43

Grammoptera subargentata, 90

Green-striped forest looper, 36

Guide to Forest Pests, 17

Gypsy moth, 14, 15

Hardwood 

cankers, 148

gall insects, 66

leaf rusts, 129

Hartig’s conk, 173

Hawkmoth, 39

Heart rot, 123, 140, 146, 153, 156, 159, 162, 

163, 167–169, 171, 172, 177–179, 196

Hemichroa crocea, 50

Hemlock 

canker, 146, 147

dwarf mistletoe, 10, 123, 138–143, 173, 

198

fluting, 195, 196

hylesinus, 81

looper, Western, 32

needle rust, 128

sawfly, 10, 37, 46

Hepialidae, 86, 90

Hericium abietis, 183

Heterobasidion annosum, 152–154

Hirschioporus abietinus, 175

Homoptera, 23, 57, 59, 60, 62, 64, 65, 68

Honey mushroom, 155

Horntail, 86, 101–103

Hylemia sp., 103, 107

Hyles gallii, 39

Hylesinus, hemlock, 81

Hymenoptera, 22, 23, 45, 46, 48, 50, 51, 66, 

86, 101, 102, 110, 112

Indian paint fungus, 171

Insect pests of wood products, 109–114

Invasive pests, 14–16

Inonotus

obliquus, 187

tomentosus, 157, 158

Ips 78–80, 203

borealis, 78

concinnus, 78

perturbatus, 78

pini, 78

tridens, 78

Judolia m. montivagans, 90

Keithia thujina, 130

Laetiporus sulphureus, 165

Lacquer conk, 170

Lambdina fiscellaria lugubrosa, 32

Larch 

beetle, eastern, 77

budmoth, 55

sawfly, 48, 49, 77

Large aspen tortrix, 28, 29

Leaf beetles, 23, 52

Leaf blotch miners, 42

Leaf miner, aspen, 42

Leaf miner, birch, 45

Leaf miner, willow, 43, 44

Leaf rollers, 30, 31, 35

Lepidoptera, 22–24, 26, 28, 30, 32, 34, 

36–43, 55, 86, 97, 99, 103–105

Leptographium abietinum, 190

Lirula macrospora, 190
243

Logging

as control, 74

salvage, 92

Looper,

green‐striped forest, 36

saddle-backed, 37

western hemlock, 32

Lophocampa maculata, 41

Lophodermium picea, 131, 132

Lyctidae, 113

Lyctus sp., 113

Lymantria dispar, 15

Lymantriidae, 23, 41

Lyonetia sp., 42

Lyonetidae, 23, 42

Macrohaltica bimarginata, 52

Maggots, spruce cone, 107

Malacosoma californicum, 15

Management, forest, 16, 153, 194

Melampsora

epitea, 128, 129

medusae, 129

Melampsoridium betulinum, 129

Melanophila

fulvoguttata, 94

drummondi, 92

Melanolophia imitata, 36

Micrurapteryx salicifoliella, 43

Midge(s) 

spruce bud, 53, 54

spruce gall, 108

yellow-cedar gall, 108

Mistletoe, hemlock dwarf, 10, 123, 

138–143, 173, 198

Mites, 56, 69, 70

Eriophyid, 70

spider, 69, 70

Monochamus scutellatus, 88, 89

Mordwilkoja sp., 65

Moth(s)

ghost, 86, 99, 100

rusty tussock, 40

spear‐marked black, 10, 34, 35

spotted tussock, 41

spruce seed, 105

Mourning cloak butterfly, 38

Naohidemyces vaccinii, 128

Neacanthocinus pusillus, 90

Nectria sp., 145

galligena, 148, 149

macrospora, 144, 145

Needle-miner, spruce, 40

Neoclytus m. muricatulus, 90

Neodiprion tsugae, 46

Noninfectious disorders, 192–205

Nymphalidae, 23, 38

Nymphalis antiopa, 38

Oligonychus ununguis, 69

Orgyia antigua, 40

Outbreaks, spruce beetle, 74, 80

Oyster mushroom, 182

Pachyta lamed, 90

Parasites and predators, 16, 25

Parasitic plants, 138

Peridermium harknessii, 144

Phaeolus schweinitzii, 167

Phellinus

chrysoloma, 160, 162

hartigii, 146, 159, 173 

igniarius, 185, 187

pini, 143, 158, 160–162

robustus, 173

tremulae, 185, 187

weirii, 179, 180

Pheromones, 73, 79, 93

aggregating, 96

Phialophora melinii, 191

Phloeosinus sp., 82, 193

cupressi, 82

 punctata, 82

sequoiae, 82

Pholiota spp., 176

Phratora sp., 52

Phyllocnistis populiella, 42

Phyllonorycter nipigon, 42

Phymatodes dimidiatus, 90

Physokermes piceae, 64

Pineus similis, 60–62

Pinicola conk, 163, 164

Pini conk, 160

Piptoporus betulinus, 188

Pissodes strobi, 15

Pleurotus ostreatus, 182

Pogonocherus

mixtus, 90

penicillatus, 90

Polygraphus sp., 83

 rufipennis, 83

Polyporus
244

abietinus, 175

betulinus, 188

borealis , 174

hartigii, 173

schweinitzii, 167

sulphureus, 165

versicolor, 189

Pontania s-pomum, 66

Porcupine damage, 124, 199

Poria 

albipellucida, 179

asiatica, 179, 181

obliqua, 187

rivulosa, 179

weirii, 180

Postia sericeomollis, 179, 181

Powder post beetle, 113

Prevention measures, 91, 95, 109, 111, 149, 

169, 186

Pristiphora erichsonii, 48

Pronocera c. collaris, 90

Pseudohylesinus tsugae, 81

Pucciniastrum vaccinii, 128

Punk knots, 160, 161

Purple conk, 175

Quinine conk, 172

Rainbow conk, 189

Red belt, 201

Red belt fungus, 163

Red ring rot, 160

Redcedar white ring rot, 179

Rhabdophaga sp., 54, 66

 canadensis, 106

 rachiphaga, 106

 rosaria, 66

 swainei, 54

Rheumaptera hastata, 34

Rhizomorphs, 155, 156

Rhizosphaera pini, 131, 133

Root diseases, 152–158

Annosus, 152, 153

Armillaria, 155, 156, 193

Tomentosus, 157, 158

Rot

brown cubical, 163, 164, 166, 167, 172, 

177, 181

red ring, 160

shoe string root, 155

Tomentosus root, 157, 158

 white pocket, 161, 162, 175

 white, 153, 159, 173, 176, 179, 180, 

183, 184

 white spongy, 189

 white trunk, 185, 187 

yellow ring, 180

Round-headed borers, 86, 87, 92

Rough bark of alder, 151

Rust diseases,

spruce broom, 142

spruce needle, 125, 126

hemlock needle, 128

hardwood leaf, 129

western gall, 144, 145

Rusty tussock moth, 40

Saddle-backed looper, 37

Salvage logging, 92

Sap-sucking insects and mites, 56–70

Sawfly

hemlock, 10, 37, 46

larch, 48, 49, 77

striped alder, 50

woolly sawfly, 51

Sawyer, white-spotted, 88

Scale, spruce bud, 64

Sesiidae, 86, 97

Shepherd’s crook disease, 137

Shoe string root rot, 155

Shoot diseases, 134–137

Sirex juvencus, 102

Siricidae, 86, 101, 102

Sirococcus shoot blight, 134

Sirococcus strobilinus, 134

Sitka spruce weevil, 15

Soil moisture, 202

Sooty bark canker, 148, 149

Spear-marked black moth, 10, 34, 35

Sphingidae, 23, 39

Spider mites, 69, 70

Spittlebug, 68

Sporidesmium sp., 191

Spotted tussock moth, 41

Spruce 

aphid, 57, 58

bark beetle, 73–76

beetle outbreaks, 73–76

broom rust, 142

bud midge, 35, 54

bud scale, 64

budmoth, 55
245

budworm, 21, 26, 27, 104

canker, 146

cone-axis, 103, 106

cone maggot, 107

coneworm, 27, 103, 104

gall aphids, 60, 61, 63

gall midges, 108

needle blight, 131

needle rust, 125–127

seed moth, 105

Stain, black of Yellow-cedar, 191

Stain, blue, 190

Stain-causing fungi, 87

Stem and branch diseases, 138–151

Sthenopsis sp., 99

Striped alder sawfly, 50

Sulphur fungus, 165

Sulfur dioxide emissions, 204, 205

Synanthedon culiciformis, 97

Symbiotic relationship, 71, 109

Temperate rain forests, 11

Tenthredinidae, 23, 45, 48, 50, 51, 66

Tetranychus urticae, 69

Tetropium

cinnamopterum parvulum, 90

velutinum, 90

Tinder conk, 184

Tomentosus root rot, 157, 158

Tortricidae, 22–24, 26, 28, 30, 55, 105

Tortrix, large aspen, 28, 29

Trametes versicolor, 189

Trichaptum abietinus, 175

Trypodendron

betulae, 96

lineatum, 96

retusum, 96

Trypophloeus striatulus, 85

Uraecium holwayi, 128

Urocerus gigas flavicornis, 101, 102

Varnish conk, 170

Velvet top fungus, 167, 168

Venturia

macularis, 137

populina, 137

Wasps, wood, 101

Weather, 15, 25, 29, 31, 35, 124, 133, 137, 

144, 146, 159, 192, 201, 203

Western gall rust, 144, 145

Western hemlock looper, 32

Western tent caterpillar, 15

White pocket rot, 161, 162, 175

White rot, 153, 159, 173, 176, 179, 180, 

183, 184

White spongy rot, 189

White trunk rot, 185, 187 

White-spotted sawyer, 88

Willow bark beetle, 85

Willow leaf miner, 43

Wind, 11, 87, 123, 159, 201, 202, 204

Windthrow, 57, 73, 74, 159, 204

Winter drying, 201

Wood borers, 86–102

Wood decays and stains, 159–191

Wood wasps, 101

Woolly aphids, 42, 56, 60, 62

Woolly bears, 41

Woolly sawfly, alder, 51

Xenomeris abietis, 146

Xeris spectrum, 102

Xylocopa sp., 112

Xylocopidae, 112

Xylotrechus undulatus, 89

Yellow cap fungus, 176

Yellow-cedar decline, 10, 156, 192–194

Yellow-cedar gall midge, 108

Yellow-cedar shoot blight, 136

Yellow ring rot, 180

Zeiraphera sp., 55

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