Field Guide to 

Insects and 

Diseases of 

Arizona and New 

Mexico Forests

United States 

Department of 

Agriculture

Forest

Service

Southwestern 

Region

MR-R3-16-3
Ips galleries 

and armillaria 

mycelial fans

Piñon ips

Southwestern 

dwarf 

mistletoe 

broom on fire

Pandora moth 

larva

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USDA is an equal opportunity provider and employer.
Field Guide to Insects 

and Diseases of 

Arizona and New 

Mexico Forests

Mary Lou Fairweather, Plant Pathologist

Joel McMillin, Entomologist

Terry Rogers, Entomologist

Dave Conklin, Plant Pathologist

Bobbe Fitzgibbon, Entomologist

USDA Forest Service

Southwestern Region

333 Broadway Blvd., SE

Albuquerque, NM 87102

www.fs.fed.us/r3/resources/health

2006
Acknowledgements

The authors thank all former pathologists and entomologists, 

who either worked on the original insect and disease field guide 

developed in the 1980s, or worked on getting this version started. 

Special thanks to Sandra Roberts, printing specialist and Dan 

Ryerson, GIS specialist for the Southwestern Region in Albuquerque, 

New Mexico.

Photographs and other illustrations were obtained, as 

credited later in this document, from individuals, the files of the 

USDA Forest Service, and other sources as cited.

Preface

This book replaces “Forest Insect and Disease Field Guide” 

(Beatty 1983). Although amendments had been made to the former 

guide, our knowledge of forest insects and diseases has increased and 

some organisms have only recently been identified or found to cause 

significant damage. This new guide is designed to be practical for the 

field. Not every forest insect or disease of the Southwest is covered, 

but we have attempted to include those having significant ecological 

and/or economic impacts on forest resources such as recreation, 

wildlife, wood production, and watershed quality.

This field guide is divided into insect and disease sections, 

each with its own description, illustrations, and host index. Literature 

cited, glossary, and general index are at the end of this field guide.
Table of Contents

Roles of Forest Insects and Pathogens . . . . . . . . . . . . . . . . . . . . . 1

Invasive Pests......................................... 2

Guide to Forest Insects and Diseases . . . . . . . . . . . . . . . . . . . . . . 4

Forest Insect Defoliators................................. 7

Western Spruce Budworm. . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Douglas-fir Tussock Moth. . . . . . . . . . . . . . . . . . . . . . . . . . 11

Pine-feeding Needleminers. . . . . . . . . . . . . . . . . . . . . . . . . 14

White Fir Needleminer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Pandora Moth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Pine Butterfly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Pine Sawflies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Tiger Moth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

New Mexico Fir Looper. . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Nepytia janetae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Fall Webworm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Western Tent Caterpillar. . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Large Aspen Tortrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Alder Flea Beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Sap-Sucking Insects, Gall Formers, and Mites . . . . . . . . . . . . . 37

Aphids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Cooley Spruce Gall Adelgid. . . . . . . . . . . . . . . . . . . . . . . . 40

Spruce Aphid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

Pinyon Needle Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Prescott Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Pine Needle Scale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Ponderosa Pine Resin Midge . . . . . . . . . . . . . . . . . . . . . . . 50

Pinyon Spindle Gall Midge. . . . . . . . . . . . . . . . . . . . . . . . . 52

Spittlebugs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Spider Mites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Bark Beetles........................................ 55

Pine Engravers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Western Pine Beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Mountain Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Roundheaded Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . 67
Southern Pine Beetle and Mexican Pine Beetle. . . . . . . . . . 70

Red Turpentine Beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Spruce Beetle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Douglas-fir Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Western Balsam Bark Beetle . . . . . . . . . . . . . . . . . . . . . . . 79

Fir Engraver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Twig Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Cedar Bark Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Wood Borers........................................ 87

Wood Borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Juniper Borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Cone and Seed Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Cone Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Ponderosa Pine Seedworm. . . . . . . . . . . . . . . . . . . . . . . . . . 97

Pine Seed Chalcid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Pine Coneworm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Bud and Shoot Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Pine Tip Moths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Western Pineshoot Borer. . . . . . . . . . . . . . . . . . . . . . . . . . 103

Pinyon Pitch Nodule Moth. . . . . . . . . . . . . . . . . . . . . . . . 105

Bark Moths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Pitch Moth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Juniper Twig Pruner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Insects of Wood Products.............................. 108

Carpenter Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Termites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Foliar Diseases....................................... 113

Hardwood Leaf Diseases. . . . . . . . . . . . . . . . . . . . . . . . . 113

Black Leaf Spot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Ink Spot Leaf Blight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Melampsora Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Shepherd’s Crook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Sycamore Anthracnose. . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Conifer Needle Diseases. . . . . . . . . . . . . . . . . . . . . . . . . . 120

Lophodermella Needle Cast. . . . . . . . . . . . . . . . . . . . . . . 121

Elytroderma Needle Cast. . . . . . . . . . . . . . . . . . . . . . . . . 123

Red Band Needle Blight. . . . . . . . . . . . . . . . . . . . . . . . . . 125

Rhabdocline Needle Cast. . . . . . . . . . . . . . . . . . . . . . . . . 126

True Fir Needle Cast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

White Pine Needle Cast . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Pinyon Needle Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

Stem Decays and Stains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

Red Ring Rot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Red Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Indian Paint Fungus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Red Belt Fungus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Pouch Fungus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Blue Stain Fungi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

False Tinder Conk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Heart Rots of Oak. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Canker Rot of Oak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Cankers....................................... 147

Black Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Sooty Bark Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Cytospora Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

Cryptosphaeria Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Hypoxylon Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

Atropellis Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Stem and Cone Rusts of Pine........................... 160

White Pine Blister Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Limb Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Western Gall Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

Comandra Blister Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Gymnosporangium Rusts. . . . . . . . . . . . . . . . . . . . . . . . . 169

Fir Broom Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Spruce Broom Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Southwestern Cone Rust. . . . . . . . . . . . . . . . . . . . . . . . . . 175
Mistletoes....................................... 176

Dwarf Mistletoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

True Mistletoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

Root Disease....................................... 189

Armillaria or Shoestring Root Rot. . . . . . . . . . . . . . . . . . 191

Annosus Root Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Tomentosus Root Disease. . . . . . . . . . . . . . . . . . . . . . . . . 196

Schweinitzii Root and Butt Rot. . . . . . . . . . . . . . . . . . . . . 198

Black Stain Root Disease. . . . . . . . . . . . . . . . . . . . . . . . . 200

Ganoderma Root Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Non-infectious Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

Drought. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

Frost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Winter Injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Red Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

Windthrow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Lightning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Salt Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211

Burls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

Animal Damage...................................... 213

Ungulates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Black Bear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Porcupine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

Sapsucker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

Glossary....................................... 218

Photography and Illustration Credits . . . . . . . . . . . . . . . . . . . . 229

Instructions for Submitting Insect and Disease 

Specimens for Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

Selected References................................... 233

Host Index....................................... 247

General Index....................................... 260
1

Roles of Forest 

Insects and Pathogens

Most forest insects and pathogens in the Southwest are 

naturally occurring components of ecosystems and play an important 

role in dynamic processes. They affect short- and long-term 

vegetative structural diversity, provide food and habitat for animals, 

and contribute to biological diversity. These organisms, along with 

fire, are among the major disturbance agents in the Southwest. 

Outbreaks of forest insects and diseases can result in shifts in forest 

composition and structure. The degree of shift depends upon the 

particular insect and/or disease and on the condition of the ecosystem 

affected.

The actions of insects are often easily observed as their 

populations can quickly expand under favorable climatic conditions. 

Some insects are significant natural disturbance agents, capable of 

altering forest succession. For example, bark beetle populations can 

increase dramatically under drought conditions and cause largescale tree mortality. In contrast, indigenous tree pathogens increase 

gradually and their presence and effects may go relatively unnoticed. 

Although most people see dwarf mistletoe in our forests, few realize 

that it is the primary agent of growth loss and will gradually kill 

trees. Insects and pathogens often interact, as is seen when bark 

beetles target diseased trees. 

A key to insect and disease damage is provided in the “Guide 

to Forest Insects and Diseases” section, directing the reader to the 

appropriate insect or disease section. There is also a host index 

in the back of the book. A description for each insect and disease 

includes hosts, damage, symptoms, biology, and effects or impacts. 

References are also provided.

Please refer to your local Forest Service, Forest Health 

zone office, State Forest Health Specialist, Cooperative Extension 

Agent, or State Forester for information concerning specific control 

measures. 

References: 16, 50, 58, 98, 99, 105
2

Invasive Pests

Similar to the rest of the Nation, Arizona and New Mexico’s 

forests and grasslands are threatened by invasions of exotic species 

of insects, disease pathogens, and plants. Over the past 200 years, 

several thousand foreign plant and animal species have been 

introduced in the United States. About one in seven of these species 

has become invasive. 

Two invasive pest species 

that were introduced into the United 

States in the early 1900s have become 

established in forested lands of New 

Mexico and Arizona. White pine 

blister rust, caused by Cronartium

ribicola, was discovered in southern 

New Mexico in 1990, and is now 

found throughout most of the range 

of its host in the Sacramento and 

adjoining White Mountains. Infected 

white pines have also been found in nearby Capitan Mountains and 

Gallinas Peak, New Mexico. In 2005, a population was observed 

on the Gila National Forest, New Mexico, about 3 miles from the 

Arizona border. Based on the apparent age of cankers, the rust first 

became established around 1970 on the west side of the Sacramento 

Mountains, but it is not clear how the fungus was introduced. Over 

time, this disease will have a major impact on white pines in the 

Sacramento Mountains and some other parts of the Southwest.

The second species introduced in the region is spruce 

aphid, Elatobium abietinum. This was first reported in 1976 on an 

ornamental tree in the city of Santa Fe, New Mexico, and in a natural 

forest setting in the late 1980s. Its distribution extends from the San 

Francisco Peaks in northern Arizona, to the Sacramento Mountains 

of southern New Mexico. The damage caused by this insect in the 

Southwest is much greater than that observed elsewhere in the 

Figure 1. Adult spruce aphid
3

United States, 

which may be 

due to variations 

in the insects’ 

behavior. 

Research in 

the Southwest 

found that 

spruce aphid 

populations 

increase in the 

fall, have a 

sexual life cycle, 

and a greater 

cold-hardiness, 

all factors that 

may be contributing to the insect’s success. 

The Animal and Plant Health Inspection Service (APHIS) is 

responsible for regulating the movement of plants and plant materials 

that may carry pest organisms, and for detection and eradication 

of new pest introductions. The USDA Forest Service, the Bureau 

of Indian Affairs, and other Federal land managing agencies are 

responsible for reducing the impact of invasive exotic plants on lands 

they manage. Despite the efforts, we expect increased introductions 

of nonnative 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 and national trade. Early detection and rapid 

response are important to minimizing invasive species establishment 

and subsequent resource damage.

References: 13, 56, 105

Figure 2. White pine blister rust on ribes
4

Guide to Forest Insects and Diseases1

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. ---------------------------------7

Sap-Sucking Insects and Mites. Curled or discolored 

foliage. Whole insects or cast skins and small (1-2 mm long). 

Cottony tufts, galls, and honeydew sometimes present. --------------37

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. ---------------------------------52

Bud and Shoot Insects. Malformed, enlarged buds on 

young growth, commonly encountered on terminal buds of branches. 

In some cases, multiple leaders result. --------------------------------100

Foliar Diseases (including needles). Foliage yellow, brown, 

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

or other fungal fruiting bodies present. Fruiting bodies are very 

small. -----------------------------------------------------------------------113

Abiotic Disorders. Foliage or buds yellowing, browning, or 

dying after exposure to early or late frosts, air pollutants, drought, 

or winter damage; entire crown may show signs of stress or die as a 

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

disease agents are generally absent. -----------------------------------204

1

 Adapted from “Insects and Diseases of Alaskan Forests” (Holsten et al., 

2001)
5

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. -------------------------------------------------------------99

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. ------------------------------------------94

Cone Rust. Enlarged cones on Chihuahua pine, with orange 

spores under papery outer covering. -----------------------------------175

Damage confined to branches and stems:

Witches’ Brooms. Prolific sprouting of adventitious buds on 

branches infected with mistletoe or fungi. 

Needles retained on those caused by dwarf mistletoe. ----177

Needles cast on those caused by fungi, only to reappear the 

next year. ------------------------------------------------------------------123

Cankers and/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. -----------------------147

Strips or sections of bark removed by animals, fungi follow 

wounding. -----------------------------------------------------------------213

Stem Decay. 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. -------------------------------------------------------------------132

Bark Beetles. Insect activity characterized by boring dust 

and/or 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. ------------------------------------------------------55
6

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. ------------------------------87

Abiotic Disorders. Globe-shaped, large, woody growths or 

swellings on branches or stems of ponderosa and various hardwoods 

(burls). ---------------------------------------------------------------------212

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. -----------------------------------------------189

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 of the windstorm; signs of disease agents may be present 

(e.g. root disease). --------------------------------------------------------209

Noninfectious 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 similar to damage by 

root disease. Fruiting bodies of pathogenic fungi usually absent, but 

weakly pathogenic and saprophytic fungi (those restricted to dead 

tissues) and secondary insects may be present. ----------------------204
7

Defoliating insects damage trees by eating leaves or 

needles, removing the photosynthetic tissue critical 

for plant maintenance and growth. A significant loss 

of leaves or needles results in growth loss, increased susceptibility to 

attack by other insects and pathogens, and sometimes tree mortality. 

The impact of defoliation on individual trees is dependent on 

a variety of factors. Tree species vary in their tolerance to defoliation. 

In general, hardwood species can sustain repeated defoliation over 

several years because they store large food supplies and can refoliate 

in the same year. The timing of the defoliation relative to seasonal 

growth phenology is also important. For example, late season 

defoliation of hardwoods has a lower impact than does late season 

defoliation of conifers. A single late season defoliation of pines often 

results in tree mortality. Trees that are healthy and growing vigorously 

will generally survive defoliation better than stressed trees.

Historically, the two most destructive defoliators in the 

Southwestern Region were the western spruce budworm and the 

Douglas-fir tussock moth. Both of these defoliators can cause severe 

growth loss, top-kill, increase susceptibility to bark beetles, and 

cause outright tree mortality. More recently, three other defoliators 

have been causing heavy defoliation in higher elevation forests. 

Beginning in the early 1990s, the exotic spruce aphid and a native 

looper, Nepytia janetae, are causing high levels of mortality in the 

spruce-fir forest type in the White Mountains and Pinaleño Mountains 

of Arizona. A New Mexico fir looper outbreak began in 2002 in the 

Sacramento Mountains of southeastern New Mexico causing elevated 

levels of fir mortality.

Many other defoliating insects that have the potential to cause 

localized problems are not included in this guide. Consult Federal or 

State forest health personnel for assistance on insects not described in 

this guide.

References: 40, 66, 72, 108

Forest Insect Defoliators
8

Western Spruce Budworm

Choristoneura occidentalis (Freeman)

Hosts: Douglas-fir, true firs, and spruce

Symptoms/signs: Adults are a mottled orange brown and 

have a wing span of 22 to 28 mm. Eggs are white to light green in 

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

Newly hatched larvae are cream colored with brown heads. Fullgrown larvae are 25 to 32 mm long with brownish head and body 

and prominent ivory 

colored spots. Pupae 

are 12 to 16 mm long, 

broad at the head and 

tapering toward the tail. 

Signs of feeding include 

current foliage being 

partially or fully chewed 

over the entire tree; 

expanding buds mined 

and evidence of feeding 

on second and third 

year shoots possible; 

and shoots webbed into 

feeding shelters giving 

the tree a reddish-brown 

appearance. 

Biology: Eggs 

are laid in July and 

August and hatch in 

about 10 days. The 

initial larvae do not feed, 

but spin silken shelters 

(hibernacula) under 

Figure 3. Adult western spruce budworm with 

pupal case.

Figure 4. Egg mass of western spruce 

budworm on underside of needle. Note 

shingle-like feature.

Forest Insect Defoliators
9

bark scales or lichens where 

they will hibernate. The 

next spring larvae mine old 

needles until the buds swell 

and then bore into the buds 

and feed on the expanding 

needles. Later they web the 

growing tips together and 

feed on the new needles. The 

larvae pupate in June and 

July. Adults begin to appear 

in July and start egg laying 

for the next generation.

Effects: Defoliation 

by western spruce budworm can cause growth loss after 1 or 

2 years. Repeated heavy defoliation (4 or 5 years) can cause a 

significant decrease in growth, 

tree deformity, top-killing, 

and ultimately tree mortality, 

particularly in seedlings and 

saplings. 

Similar Insects 

and Diseases: The white fir 

needleminer, Epinotia meritana, 

feeds inside the needles of true 

fir. Mined needles are a bleached 

yellowish color and do not 

have a chewed appearance. The 

mature larvae are much smaller 

(8mm) than western spruce 

budworm and yellowish green 

to cream colored. The adult 

Figure 5. Late instar larva of western 

spruce budworm feeding on foliage.

Figure 6. Defoliation of Douglasfir tree caused by western spruce 

budworm.

Forest Insect Defoliators
10

moths have wings that are dusty gray with alternating bands of dark 

scales. Wing spread is 11 mm. Repeated defoliation by white fir 

needleminer can cause branch mortality, deterioration of tree crowns 

and increased susceptibility to fir engraver.

References: 19, 23

Figure 7. Near view of western spruce budworm defoliation 

to Douglas-fir.

Forest Insect Defoliators
11

Douglas-fir Tussock Moth

Orgyia pseudotsugae (McDunnough)

Hosts: Douglas-fir, white fir and spruce

Symptoms/signs: 

The Douglas-fir tussock 

moth caterpillar is grayish 

with brightly colored 

tufts of hair and a shiny 

black head. There are also 

two long horns of black 

hairs behind the head 

and another at the rear of 

the body. Insect feeding 

results in needle damage 

and defoliation, which is 

sometimes followed by 

top-kill. Small cocoons and 

egg mass cases are attached 

to the underside of twigs and 

branches. 

Biology: Eggs hatch 

from mid-May to early June and 

caterpillars feed on the current 

year’s 

developing 

foliage. 

Young 

larvae are 

4 to 7 mm 

long and 

covered 

with long, 

Figure 8. Adult male (left) and female 

(right) Douglas-fir tussock moth.

Figure 9. Adult 

female Douglasfir tussock moth 

on egg mass. Note 

that female moth 

is wingless.

Figure 10. Egg mass and early instar 

larvae of Douglas-fir tussock moth.

Forest Insect Defoliators
12

Forest Insect Defoliators

Figure 11. Late 

instar larva 

of Douglas-fir 

tussock moth.

Figure 12. Douglasfir tussock mothcaused damage to 

ornamental spruce 

in Los Alamos, New 

Mexico.

Figure 13. 

Near view 

of Douglasfir tussock 

moth-caused 

damage.
13

thin body hairs that later develop into tufts. Because the female moth 

is wingless, the primary means of dispersal from tree to tree is by 

windblown larvae. Young larvae congregate on the tops of defoliated 

trees and drop by silken threads that may be over 3 meters long. 

These threads eventually break from the tree and give a ballooning 

effect to the larvae. Mature larvae are about 20 to 30 mm long 

with a gray or brown body and a shiny black head. Two long hair 

pencils project forward from behind the head and another occurs at 

the rear of the body. Four brushes of brown or cream-colored hairs 

and red spots occur on the first four and last abdominal segments. 

Some people develop an itchy rash from exposure to the frequently 

airborne caterpillar hairs. After the caterpillars are about halfgrown, they feed on all age classes of needles throughout the crown. 

Pupation occurs inside a thin, silk cocoon spun on the undersides of 

branches from late July to the end of August. Adults emerge shortly 

afterwards and the flightless female deposits egg masses on twigs 

and branches.

Effects: Severe outbreaks can cause significant mortality of 

both overstory and understory trees relatively quickly (1 or 2 years). 

Top-kill occurs in less severe outbreaks. Bark beetle epidemics can 

occur in tussock moth defoliated areas. 

Similar Insects and Diseases: Early damage and webbing 

in trees may be similar to that caused by western spruce budworm; 

however, the larvae are very distinct.

References: 9, 23, 111 

Forest Insect Defoliators
14

Pine-feeding Needleminers

Coleotechnites spp.

Hosts: Ponderosa pine and piñon

Symptoms/Signs: Adults of pine-feeding needleminers are 

small, narrow-winged, mottled, silvery-gray moths with a wingspan 

of about 10 mm. Eggs are too small, 0.2 mm in diameter, to be 

noticeable. Larvae are brown, 8 mm long when fully developed, 

and usually found mining within current year’s needles. The pupae 

are elongate, 

cylindrical 

black, and 

about 6 mm 

long. Needles 

inhabited 

by third and 

fourth instar 

larvae turn a 

faded yellowbrown in 

color and 

have several 

tiny holes in 

them for frass 

disposal and 

larval exit.

Biology: Adult moths emerge and fly in June and July. Eggs 

are laid inside previously mined needles. Larvae begin hatching 

in July, crawl to and mine into previously uninfested needles and 

overwinter. Pupation occurs in late spring.

Effects: Persistent infestations can cause severe 

discoloration, defoliation, and reduced growth of stems, shoots, and 

needles. 

Forest Insect Defoliators

Figure 14. Silhouette of Coleotechnites larvae feeding 

inside ponderosa pine needle.
15

Similar Insects and Diseases: 

Similar symptoms, i.e., discoloration and 

defoliation, can result from scale insects, 

aphids, and needle cast diseases. However, 

only the needleminers leave telltale holes 

in the mined needles.

References: 23, 96 

Forest Insect Defoliators

Figure 16. Needle damage caused by 

Coleotechnites feeding on ponderosa pine.

Figure 15. Closeup of 

needle damage caused by 

Coleotechnites feeding on 

ponderosa pine.
16

White Fir Needleminer

Epinotia meritana (Heinrich)

Host: White fir

Symptoms/Signs: Larvae mine the needles, resulting in 

bleached-yellow mined needles from late spring to early fall. Mature 

larvae are about 8 mm long, yellowish-green to cream colored, with 

brown to black heads. Pupae are orange to dark brown, about 5.5 

mm in length, and can often be seen protruding from the hole in the 

mined needle prior to emergence. The adults are 11 mm dusty gray 

moths. They can be seen swarming around host trees in late June and 

July.

Biology: The white fir needleminer has one generation 

per year in New Mexico and Arizona. Eggs are deposited, usually 

one egg per needle, in late June and July. Eggs hatch in August and 

September. Young larvae immediately bore into the needle where 

they overwinter. As weather warms in the spring, feeding begins. 

Each larva mines several (five to seven) 1-year-old needles. Two- and 

three-year-old needles are also mined during outbreak conditions. 

Forest Insect Defoliators

Figure 17. Defoliated white fir caused by the white fir needleminer.
17

Two to six needles are usually webbed together and remain on the 

tree for the duration of the summer. Pupation occurs within the last 

mined needle in June or early July. Adult moths emerge in 10 to 14 

days after pupation. Mating occurs within 2 to 3 days of emergence.

Effects: After several consecutive years of heavy defoliation 

a high proportion of limb mortality and widespread tree mortality 

may occur. This can give individual trees or even entire stands a 

silvery appearance. These heavily defoliated stands decline in vigor 

and may be predisposed to attack by fir engraver beetle.

Similar Insects and Diseases: Similar defoliation may be 

caused by western spruce budworm or Douglas-fir tussock moth; 

however, the larvae of white fir needleminer only mine the needles.

References: 23, 109 

Figure 18. Closeup of white fir needleminer defoliation to white fir.

Forest Insect Defoliators
18

Pandora Moth

Coloradia pandora (Blake)

Hosts: Ponderosa pine

Symptoms/Signs: Adult 

pandora moths are very large and 

heavy bodied, about 2.5 to 4.0 cm 

long, with a wingspread of 7 to 11 

cm. The forewings are brownish 

gray and hindwings are light pinkish 

gray, each marked with a black dot 

and a dark wavy line. The males are 

distinguished by having large, feathery antennae. The globular eggs, 

bluish green to bluish gray, are deposited in clusters of 2 to 50. Early 

instar larvae are about 5 mm long. They have shiny black heads and 

black to brownish bodies that are covered with short, dark hairs. 

Fifth instar larvae grow to about 6 to 

8 cm long and are brown to yellowish 

green. Pupae are dark purplish brown, 

2.5 to 3.5 cm long, and have a tough 

shell.

Biology: The pandora moth 

has a 2-year life cycle. Adults emerge 

between 

late July 

and late 

August. 

The moths mate and females deposit their 

eggs within a few days. The egg stage 

lasts at least 40 days and most larvae 

emerge in October. Larvae are gregarious 

and extremely cold hearty. They feed 

in groups on the foliage on warm days 

throughout the winter. Fifth instar larvae 

leave the host trees in late June and enter 

Forest Insect Defoliators

Figure 19. Adult pandora moth.

Figure 21. Late instar 

larva of pandora moth.

Figure 20. Early instar larva 

of pandora moth.
19

the ground where they pupate. 

They remain in the pupal stage 

for the next 12 to 13 months.

Effects: During 

outbreaks, defoliation can be 

severe over large areas. Due to 

the 2-year life cycle, however, 

defoliation occurs only during 

alternate years. Outbreaks 

on the Kaibab Plateau have 

subsided without causing any 

lasting damage. However, 

some growth loss and even mortality can occur especially if trees are 

severely stressed from additional factors such as drought or heavy 

dwarf mistletoe infections.

Similar Insects and Diseases: May be confused with 

sawfly larvae and defoliation. However, sawfly larvae have smooth 

bodies, are smaller, 18 

to 25 mm long, and 

have eight pairs of leglike appendages on the 

abdomen. Defoliation 

caused be sawflies 

usually occurs on an 

individual or small 

group of trees and is 

not widespread like 

that of a pandora moth 

outbreak.

References: 

10, 23, 85 

Forest Insect Defoliators

Figure 22. Pupae of pandora moth.

Figure 23. Defoliation of ponderosa pine 

caused by pandora moth on the Kaibab NF, 

Arizona.
20

Pine Butterfly

Neophasia menapia (Felder and Felder)

Host: Ponderosa pine

Symptoms/signs: Newly 

hatched pine butterfly larvae are 

gregarious feeders on older foliage 

and then move to the new foliage 

as they mature. Mature larvae are 

approximately 2.5 cm long, dark 

green in color and have light green 

heads. The body is covered with 

fine hairs and has two white lateral 

stripes on the side. Adult moths are 

white with black markings.

Biology: Adults fly 

and lay their green eggs from 

August through October. The eggs 

overwinter and the larvae hatch 

the following June or about the 

time new foliage appears. The 

small larvae feed in clusters with 

their black heads 

oriented toward the 

tip of the needle. 

As the larvae 

mature they feed 

singly. They pupate 

in late July for 

approximately 15-

20 days.

Forest Insect Defoliators

Figure 24. Adult pine butterfly.

Figure 25. Larva of pine butterfly.
21

Effects: This insect has 

caused spectacular defoliation in 

the Pacific Northwest, however, 

it causes little defoliation in the 

Southwest.

Similar Insects and 

Diseases: The pine butterfly adult 

resembles the common cabbage 

butterfly. In addition, the young 

larvae feeding in groups may be 

confused with other gregariously 

feeding larvae such as sawflies. 

These would include Neodiprion

spp. and Zadiprion spp. of 

sawflies. Pandora moth is also 

a defoliator of ponderosa pine. 

This insect has a 2-year life cycle. 

Mature larvae are distinctly larger, 

brown to yellowish green in color 

and possess stout, branched spines 

on each body segment.

References: 23 

Forest Insect Defoliators

Figure 26. Pupa of pine butterfly.
22

Pine Sawflies

Neodiprion spp., Zadiprion spp.

Hosts: Ponderosa pine, piñon

Symptoms/signs: Pine 

sawfly larval appearance varies 

by species and by larval instar, 

but most are green or yellowish 

green in color with black, tan or 

orange head capsules. Larvae are 

found in either spring-summer or 

fall-winter feeding gregariously on 

older foliage, consuming only the 

outer needle tissue while leaving the 

central ribs intact. The central ribs 

later turn yellow brown and break 

off. Later 

instar larvae 

feed singly and consume most of the needle. 

Eggs are laid in slits cut in the edge of living 

pine needles. A papery cocoon covers pupae. 

Adults are broad waist wasps. Infested trees 

have sparse foliage and thin crowns.

Effects: Eight species of sawflies 

infest pines in the Southwest, five of those 

are found on ponderosa pine. Different 

species have different preferences for the 

size of host attacked, and location on the 

host where they feed. Pine sawflies in the 

Southwest typically attack open-grown trees 

Forest Insect Defoliators

Figure 27. Adult female pine sawfly 

(Neodiprion spp.) ovipositing on 

ponderosa pine.

Figure 28. Row type egg mass of 

pine sawflies on ponderosa pine.

Figure 29. Late instar 

of Neodiprion gillettei 

feeding on ponderosa 

pine.
23

or areas where pine is growing at a low density. The same trees are 

frequently defoliated year after year. In general, defoliation causes 

slower growth. Repeated defoliation can result in top-kill and tree 

mortality.

Similar Insects and 

Diseases: See pandora moth and 

pine butterfly.

References: 18, 23, 63, 

65, 67, 68, 69 

Note: The taxonomy of 

this group has recently changed. 

The Neodiprion fulviceps

Complex, described in Furniss 

and Carolin, has been split into N. fulviceps and a new species N. 

autumnalis. The life cycle information described for N. fulviceps in 

Furniss and Carolin is now considered that for N. autumnalis.

Forest Insect Defoliators

Figure 30. Late instar larva of 

Zadiprion rohweri feeding on 

piñon pine.

Figure 31. Late instar larvae of 

Zadiprion townsendii feeding on 

ponderosa pine.

Figure 32. Defoliated ponderosa 

pine caused by pine sawflies near 

Flagstaff, Arizona.
24

Tiger Moth

Lophocampa ingens (Edwards)

(=Halisidota ingens)

Hosts: Ponderosa pine, white pines, and piñon 

Symptoms/Signs: Larvae feed on foliage and make large 

silken webs (tents) in the upper branches of host pines. Mature 

caterpillars are about 4 cm long, reddish brown to black in color and 

have tufts of black and yellow hairs on their back. Adult moths have 

dark forewings with large, white splotches and white hindwings.

Biology: The 

tiger moth has one 

generation per year in 

the Southwest. Adult 

moths emerge and 

lay eggs in August. 

During September and 

October caterpillars 

hatch from eggs, 

begin feeding on pine 

needles and producing 

webbing. Larvae 

overwinter in the webs 

in groups. In April and 

May, larvae resume 

feeding and expand 

their webs. At this 

point the insects and 

the webs become very 

noticeable. In June 

pupation occurs. 

Tiger moths 

are also found feeding 

and forming tents on 

Douglas-fir and white 

fir during outbreaks. 

Forest Insect Defoliators

Figure 33. Adult tiger moth.

Figure 34. Larvae of tiger moth.
25

It is believed that populations 

of this insect usually remain at 

low levels due to the action of 

predators, parasites, diseases, 

and cold winters. 

Effects: Larvae feed 

gregariously in webs primarily 

on young piñon and ponderosa 

pine. Although the webs and 

larvae can be very noticeable in 

spring, this insect causes minor 

defoliation. Permanent tree 

injury rarely results from feeding 

that is usually limited to the 

upper foliage. 

Similar Insects and 

Diseases: Tents are similar to 

those formed by tent caterpillars 

such as the western tent 

caterpillar; however, L. ingens is 

the most common moth to make 

large tents on piñon, ponderosa, 

and white pines. Another species of tiger moth, L. argentata 

subalpina feeds primarily on juniper but occasionally on piñon in the 

Rocky Mountain region.

References: 23, 104 

Forest Insect Defoliators

Figure 35. Tents and damage of 

ponderosa pine caused by tiger moth.
26

New Mexico Fir Looper

Galenara consimilus (Heinrich)

Hosts: Douglas-fir and white fir

Symptoms/Signs: Larvae 

feed on the foliage often stripping its 

host of needles. The immature stages 

of this insect have not been described. 

The forewings of the adults are light 

gray overlain with grayish-brown and 

brownish-black scales.

Biology: Little is known 

about the biology of this insect. 

Outbreaks of this occasional pest 

occurred in 1924, 1928, 1951, 1958, 

1974, 1977, and 2002 in New Mexico, the only state in which this 

insect is known to occur. 

Effects: This insect can cause heavy defoliation of Douglasfir and white fir resulting in growth loss and top-kill. Several years of 

heavy defoliation can result in high levels of tree mortality.

References: 23

Figure 36. Larva of New 

Mexico fir looper.

Figure 37. Damage of fir caused by 

New Mexico fir looper.

Figure 38. Near view of 

damage of fir caused by 

New Mexico fir looper.

Forest Insect Defoliators
27

Nepytia janetae 

(Rindge)

Hosts: Engelmann spruce, 

subalpine fir

Symptoms/signs: Larvae of 

this insect feed on foliage, chewing 

needles of all ages. Defoliation can 

be light to heavy. Partially consumed 

needles can be found beneath 

the trees. Mature caterpillars are 

approximately 2.5 cm in length. The 

upper surface of the larva is gray with 

dark brown 

and green 

markings in a 

herringbone 

pattern and 

with irregular 

pale cream 

lateral stripes. 

The head 

capsule is 

mottled with 

a distinct 

black stripe 

above the 

mouthparts. 

These larvae 

can be seen in the foliage, hanging from silken threads, beneath the 

tree on ground or snow and climbing up the bole of the tree. Adults 

are small light gray moths that can be seen flying singly through the 

woods or flying in large numbers around the tops of host trees. Pale 

green pupae or empty pupal cases can be seen on the foliage wrapped 

in webbing. Mummies of parasitized larvae can be seen in the foliage 

attached to needles. 

Forest Insect Defoliators

Figure 39. Adult Nepytia janetae.

Figure 40. Larva (looper) of Nepytia janetae.
28

Biology: N. janetae

has one generation per year. 

Adults appear in late June, 

peak flight is reached in 

early July. Eggs hatch in 

late September. Larvae feed 

throughout the winter and 

spring. Some are present 

in larval form until early 

July. There is considerable 

overlapping of life stages. 

Effects: During 

outbreaks, spruce-fir stands can 

be heavily defoliated resulting 

in growth loss and, with multiple years of defoliation, tree mortality. 

Mortality can be due to defoliation alone 

or due to secondary infestation by spruce 

beetle and western balsam bark beetle. 

This insect caused extensive damage and 

mortality to spruce and subalpine fir in the 

White Mountains and Pinaleño Mountains 

of Arizona in the late 1990s. Associated 

spruce beetle mortality occurred only in the 

Pinaleño Mountains.

Similar Insects and Diseases:

Although there are similar insects in other 

regions (e.g. western hemlock looper and 

western false hemlock looper), none have 

been observed in the Southwest. 

References: 56, 80 

Figure 41. Defoliated fir caused 

by Nepytia janetae in the White 

Mountains, Arizona.

Figure 42. Near view of 

fir defoliated by Nepytia 

janetae in the White 

Mountains, Arizona.

Forest Insect Defoliators
29

Fall Webworm

Hyphantria cunea (Drury)

Hosts: Willow, alder, 

ash, chokeberry, cottonwood and 

madrone

Symptoms/signs: 

Larvae feed on foliage, forming 

large webs in the branches of 

trees. Webs are noticeable in the 

fall when larval feeding takes 

place. There are two races: a 

blackheaded or northern race and 

a redheaded or southern race. 

Larvae of the southern race are 

yellowish-tan with red or orange colored heads and brownish hair 

that arises from reddish-brown tubercles. Larvae of the northern 

race have a black head with a pale yellowish or greenish body that 

has a dark stripe on the back, and long white hairs rising from red 

or black tubercles. 

The black-headed 

race predominates in 

the West. Adults are 

white in color with 

orange markings on 

the body and legs. 

The wings have 

some black spots 

and a wing expanse 

of approximately 30 

mm.

Biology: 

Fall webworm has 

one generation per year. Adults appear and lay eggs in late June and 

early July. The eggs hatch and the small larvae feed on both leaf 

Forest Insect Defoliators

Figure 43. Adult and pupa of fall 

webworm.

Figure 44. Larva of fall webworm.
30

surfaces while larger larvae will consume the whole leaf. Larval 

feeding continues until mid-September. The insect overwinters in the 

pupal stage in a transparent cocoon in the soil, leaf litter, or on tree 

trunks.

Effects: This insect causes minor defoliation in most 

forested situations. It can cause loss of visual quality in ornamental 

plantings.

Similar Insects and Diseases: The western tent caterpillar 

is sometimes confused with the fall webworm, due to both having 

dark heads and dark stripes down their backs. However, western tent 

caterpillars feed in the spring while fall webworm feeds in the fall.

References: 15, 23 

Figure 45. Damage caused by fall webworm.

Forest Insect Defoliators
31

Western Tent Caterpillar

Malacosoma californicum (Packard)

Hosts: Aspen, 

willows, cottonwoods, 

and mountain mahogany

Symptoms/signs: 

Western tent caterpillar is 

an early season defoliator 

with feeding damages 

typically occurring 

between May and June. 

Symptoms include 

moderate to complete 

defoliation of trees; large 

silken tents on branches; 

and presence of larvae in and around the tents. Trees repeatedly 

defoliated will have sparse foliage, minor branch dieback, and in 

some cases, tree mortality. 

Mature larvae are 4 

to 5 cm long and vary widely 

in coloration. Their heads are 

blue to black and body color 

patterns are mixtures of black, 

orange, and blue. Larvae are 

usually quite hairy.

Biology: Larvae 

overwinter as first instars 

inside egg masses glued 

around twigs. Larvae emerge 

from egg masses in spring and construct silken tents on branches 

that are used for shelter and molting during the daytime. At night, 

caterpillars feed outside of the tents. As the larvae mature, they 

disperse and become solitary feeders. Moths emerge from cocoons 

and glue egg masses to live twigs that are less than 2 cm in diameter.

Forest Insect Defoliators

Figure 46. Adult western tent caterpillar and 

egg mass.

Figure 47. Larva of western tent 

caterpillar.
32

Effects: Heavy 

defoliation of aspen for a 

number of years will cause 

growth loss and branch dieback. 

Some mortality may also occur 

during prolonged outbreaks. 

Outbreaks, however, are 

generally short lived, generally 

lasting 2 to 3 years.

Similar Insects and 

Diseases: See fall webworm 

and foliar diseases.

References: 3, 15, 23 

Figure 48. Tents of western tent 

caterpillar on aspen.

Figure 49. Western tent caterpillar larvae and defoliation of 

aspen on the Carson NF, New Mexico.

Forest Insect Defoliators
33

Large Aspen Tortrix

Choristoneura conflictana (Walker)

Host: Aspen

Symptoms/Signs: Presence of 

flat egg masses on the upper surface of 

foliage, partially eaten rolled-up leaves 

in which small, green to black larvae 

are feeding or pupating, incomplete 

defoliation before the buds have 

expanded in the spring. 

Biology: Pale green egg masses 

are laid in large, flat masses on the upper 

surfaces of the foliage in June and July. 

Second-instar larvae overwinter in silken 

hibernacula in bark crevices and other 

out-of-the-way places. The 

small larvae begin to migrate 

up the stems of aspen on 

warm days in early spring. 

The larvae mine the buds, 

sometimes causing complete 

defoliation before the buds 

open. Later stage larvae 

roll the leaves into shelters 

within which they feed 

and eventually pupate. The 

moths have a wingspread of 

25 to 30 mm. The forewing 

Forest Insect Defoliators

Figure 50. Adult large 

aspen tortrix.

Figure 51. Closeup of 

damage caused by large 

aspen tortrix and larva.
34

is grayish with basal, middle, and outer brownish patches. There is 

one generation annually.

Effects: During outbreaks, this insect can completely 

defoliate aspen stands. Outbreaks characteristically last 2 to 3 years 

and can result in growth loss and some twig and branch dieback.

Similar Insects: Larvae and pupae are similar to those of 

the western spruce budworm. However, the larvae of the large aspen 

tortrix are green to grayish-black with a black head capsule while the 

western spruce budworm larvae are white to grayish-tan with a tan 

head capsule and feed on Douglas-fir, true firs, and spruce.

References: 4, 23 

Figure 52. Large aspen tortrix defoliation of aspen in Colorado.

Forest Insect Defoliators
35

Alder Flea Beetle

Altica ambiens (LeConte)

Hosts: Alder

Symptoms/signs: Larvae 

are skeletonizers, meaning that 

they feed on the tissue between 

the veins, but leave the veins 

intact. Adults chew holes in the 

leaves. Adult beetles are dark 

shiny blue, and about 5 mm long. 

The mature larvae are a little 

longer and narrower than the 

adults, brown to black above and 

yellowish below.

Biology: One generation is reported per year. Adults 

hibernate during the winter in duff at the base of trees and in other 

sheltered places. They emerge in early spring to resume feeding. 

Eggs are laid in clusters on 

foliage. Larvae hatch and begin 

feeding within a few days. One 

source reports that larvae mature 

in August; but in the Southwest 

they mature earlier in the season.

Effects: No longterm effects are documented. 

Outbreaks are generally short 

lived and sporadic with heavy 

defoliation. Trees tend to recover 

quickly.

Forest Insect Defoliators

Figure 53. Adult alder flea beetle.

Figure 54. Early instar larvae of 

alder flea beetle on underneath side 

of alder leaf.
36

Similar Insects and Diseases: Although other defoliators 

feed on alder, outbreaks of these other insects have not been 

reported.

References: 23, 45 

Figure 55. Late instar larvae of alder flea 

beetle on defoliated alder leaves.

Figure 56. Defoliation of alder 

caused by alder flea beetle in 

Arizona.

Forest Insect Defoliators
37

The majority of sap-sucking insects are in the orders 

Hemiptera (true bugs) and Homoptera (aphids, 

leaf and plant hoppers, and scales). Most of these 

insects are relatively small in size and injure the host in two ways: 

(1) directly by sucking 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 mistaken as a pathogen 

induced disease. A few of the sap-sucking insects are able to kill their 

hosts outright, but most reduce growth rates and weaken the tree. 

Trees injured by these insects may succumb to secondary insects 

or fungal diseases. Signs of sap-sucking insect injury consist of 

enlarged growths or galls, leaf curling, bleaching, or yellowing of 

foliage. Conifers are more severely injured than hardwoods.

In the Southwest, there are several sap-sucking insects that 

cause noticeable damage to trees and shrubs, but they have not 

affected forests at the landscape scale. Their impacts are typically 

more important to shade trees and ornamentals. However, a spruce 

aphid, Elatobium abietinum, has been severely impacting spruce 

forests and ornamentals in some areas of the Southwest since the 

1990s. 

Use of a hand lens will help in detection and identification, 

as these organisms are quite small.

References: 23, 40 

Sap-Sucking Insects, 

Gall Formers and Mites
38

Aphids

Aphididae, Adelgedae

Hosts: Hardwoods and conifers

Symptoms/signs: The best 

evidence of infestation is the insects 

themselves or shiny leaves from the 

honeydew. Honeydew is a clear, 

sugary, sticky liquid that aphids 

excrete as they feed. It accumulates 

on the foliage, twigs, trunk and 

ground. Honeydew attracts ants, and 

often the presence of ants on a tree 

may indicate that aphids are there. 

It is also a good growth medium for 

sooty mold, which grow on affected 

portions of the tree. Aphids are 

small soft-bodied gregarious insects. 

Adults may be winged or wingless. 

Nymphs are wingless. They vary in 

color by species, but may be nearly 

colorless to green to black.

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 57. Cinara aphids on 

pine host.

Figure 58. 

Eggs of 

aphids on 

pine needle.
39

Biology: Typically aphids produce several generations per 

year, most are parthenogenetic. The last generation is usually sexual, 

and then winter is spent in the egg stage. Different aphids feed on 

different parts of their hosts, including the foliage, twigs, trunk, and 

roots. All aphids have piercing mouthparts that they use to feed on 

sap from their host plants.

Effects: Feeding can result in formation of small necrotic 

spots. Heavy feeding by some species can cause early leaf drop, 

yellowing of foliage, and reduced growth. In general, these insects 

are not considered economically important in forest situations. In 

urban areas, the honeydew can accumulate on walkways and vehicles 

and attract the attention of the public.

Similar Insects and Diseases: Damage caused by aphids 

may resemble that caused by needle midges, other sucking insects, or 

needle diseases.

References: 23 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 59. Aphid damage to conifer host.
40

Cooley Spruce Gall Adelgid

Adelges cooleyi (Gillette)

Hosts: Spruce and Douglas-fir

Symptoms/signs: 

Cone-like galls, 12-75 mm 

long, are formed on spruce 

branch tips as a result of 

feeding by the nymph 

stage of this insect. In late 

spring, galls are light green 

to purplish in color and 

the nymphs may be found 

inside. In late summer and 

fall, galls dry up and open 

and the nymphs emerge, 

flying to Douglas-fir to 

complete the next phase of 

their life cycle. The galls 

may persist on the branches for several years.

On Douglas-fir the insect feeds on the sap of new needles, 

new shoots, and developing cones. Nymphs are oval and black with 

a white waxy fringe. 

Adults are dark brown 

and covered with white, 

wooly wax. Feeding on 

Douglas-fir does not 

cause galls to form but 

rather yellowing and 

twisting of the needles.

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 60. Gall of spruce gall adelgid on 

spruce.

Figure 61. Cross section of gall showing 

nyumphs of spruce gall adelgid on spruce.
41

Biology: The entire life 

cycle requires 2 years. There are 

six stages in addition to the eggs 

and crawlers when both host 

trees are present.

Effects: This insect 

has a very complex life cycle 

involving two hosts, spruce 

and Douglas-fir. On spruce, 

galls are unimportant in forest 

situations. However in nurseries, 

plantations, and on ornamentals, 

galls are a concern since they 

kill branch tips and can stunt and 

deform trees.

On Douglas-fir infested 

needles turn yellow and become 

twisted. Heavy infestations on 

poor sites result in defoliation.

Similar Insects and 

Diseases: Damage on Douglasfir is similar to that caused by 

needle midges or needle cast.

References: 23 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 62. Waxy filaments 

(“cotton”) created by Cooley spruce 

gall adelgid on Douglas-fir branch.
42

Spruce Aphid

Elatobium abietinum (Walker)

Hosts: Engelmann spruce and blue spruce

Symptoms/signs: The spruce aphid is a small green, softbodied insect about 1 to 1.5 mm in size. Both winged and wingless 

forms occur. Spruce aphids feed by inserting their needle-like 

mouthparts into host foliage and sucking the sap from the needles. 

First symptoms 

of feeding are 

yellow patches on 

the needles. If the 

population increases, 

discoloration 

intensifies and 

affected needles 

turn brown and drop 

prematurely.

Biology: 

Like other aphids, 

the spruce aphid 

bears live young with 

females producing 

females. Nymphs mature within 3 weeks. During favorable years, 

large colonies develop during the winter and feed during mild 

periods. Populations reach a low point during the summer and may 

be very difficult to find. In the fall, aphids may reappear and begin 

feeding on the current year’s foliage. Greatest population increases 

generally occur from late winter into early spring in northwestern 

North America and Europe, however, the highest population densities 

in the Southwestern United States occur in the fall.

Effects: Since populations decline prior to needle flush in 

late spring and early summer, the new foliage is unaffected by the 

overwintering population of aphids. Current year’s foliage is not 

affected until aphids begin building up again in the fall. Defoliation 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 63. Adult spruce aphid.
43

is usually partial, but in some outbreaks trees are completely 

defoliated. Heavy defoliation can result in tree mortality, especially 

if trees are also infected with 

dwarf mistletoe. All age 

classes of spruce are infested. 

Outbreaks are sporadic, 

usually short-lived, and 

associated with dry winter 

and spring conditions (i.e. 

outbreaks begin in the fall).

References: 54, 55, 

57, 113 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 64. Spruce aphid 

defoliation of Engelmann 

spruce on the White Mountains, 

Arizona.

Figure 65. Closeup of defoliation caused by spruce aphid.
44

Pinyon Needle Scale

Matsucoccus acalyptus (Herbert)

Host: Piñon

Symptoms/Signs: Pinyon needle 

scale is most easily recognized by finding 

cotton looking egg masses in spring, black 

bean-shaped nymphs in fall, or emerged 

adults in April.

Biology: Adults emerge during 

middle to late April. Adult females are 

wingless and flightless and males are 

winged. After mating, females lay clusters 

of yellow eggs covered with white, cottony 

webbing around the root collar, undersides 

of branches, branch crotches, or crevices 

in rough bark. Sometimes egg masses are 

found several meters away from piñons on 

a rock or log. Crawlers emerge about 5-6 

weeks after eggs are laid. They climb to the 

ends of branches and settle on the previous 

year’s new growth. After inserting their 

piercing sucking mouthparts into a needle, they become immobile. 

The body becomes covered with 

wax and turns black in color. 

This occurs in the Southwest by 

early June. By October, the larva 

resembles a small black bean 1.5 

mm long. They overwinter in 

this stage.

Effects: Infestations 

can cause needles to yellow and 

drop. Repeated attacks cause 

reduced new growth and stunted 

needles. In severe outbreaks, 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 66. Adult pinyon 

needle scales appear like 

small, dark, bean-shaped 

objects on piñon needles.

Figure 67. Pinon needles damaged by 

pinyon needle scale have a chlorotic 

(yellow) appearance.
45

small trees may be killed 

outright and larger trees can be 

predisposed to attack by bark 

beetles.

Similar Insects and 

Diseases: Symptoms of needle 

scale may look similar to 

needle cast caused by fungi, 

but fruiting bodies will be 

embedded in needles rather than 

external. 

References: 8, 23 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 68. Egg masses of pinyon 

needle scale are found at or near 

the base of infected piñon.

Figure 69. Damaged 

piñon caused by 

pinyon needle scale.
46

Prescott Scale

Matsucoccus vexillorum (Morrison)

Host: Ponderosa pine

Symptoms/signs: The most noticeable symptom is the 

appearance of branch flagging in spring. Upon closer inspection old 

egg masses can often be found on flagged twigs, often at branch 

nodes.

Biology: In April and May, flightless but mobile females 

and winged males emerge from overwintering pre-adults. Following 

mating, eggs are laid, often at branch nodes. Eggs are laid in groups, 

covered with a fluffy white wax, which makes them look like tiny 

cotton balls. During May and June first stage larvae, called crawlers, 

settle in temporary feeding spots. The second stage larvae settle in 

permanent feeding locations in July and August. They feed beneath 

scales at the base of needles and in cracks and crevices of twigs, 

particularly around the first and second nodes. During fall the third 

or pre-adult stage develops and then overwinters. The life cycle is 

completed in 1 year.

Affected twigs exhibit lesions, brownish areas in the phloem. 

A fungus, Cenangium spp., is sometimes associated with the lesions.

Apparently 

the principal factor 

in natural control is 

branch dieback. Few 

natural enemies have 

been found outside of 

a species of ladybird 

beetle and a green 

lacewing.

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 70. Waxy filaments (“cotton”) created by 

Prescott scale in Arizona.
47

Effects: 

Branch flagging is 

the most common 

symptom. It occurs 

primarily in younger 

trees, less than 75 

years old and is 

most conspicuous in 

dense stands. Both 

lateral and terminal 

shoots can be 

affected. Mortality 

rates averaged 

1-2 percent in past 

outbreaks.

Similar 

Insects and 

Diseases: Bark 

beetles known 

as twig beetles 

also cause twig dieback in ponderosa pine. However upon close 

inspection one can find the galleries of these insects either in the 

inner bark or the pith of affected branches.

References: 23, 62 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 71. Branch damage (“flagging”) caused by 

Prescott scale in the White Mountains, Arizona.
48

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 72. Seasonal life history of Prescott scale.
49

Pine Needle Scale

Chionaspis pinifoliae (Fitch)

Hosts: Most pines, spruce, Douglas-fir

Symptoms/signs: Damage 

is especially noticeable on 

ornamental pine and spruce trees 

growing along dusty roads. Insects 

feed by sucking sap from needles, 

causing the needles to yellow and 

eventually drop.

Biology: The pine needle 

scale has two generations per year. 

The 3.5 mm long mature female 

scales are most conspicuous. They 

are almost pure white, slender at the 

front with a wider rear end. Males are smaller and slender and rarely 

seen. Twenty to 30 eggs are laid in the fall and winter beneath the 

dead female scale. Eggs hatch in May and the nymphs, or “crawlers”, 

move to new green needles to feed. Nymphs mature by early July, 

adults mate, and new clusters of eggs are laid. Scales of this second 

generation mature by fall and lay the overwintering eggs.

Effects: Heavy infestations over several years can kill young 

trees and severely weaken larger trees, predisposing them to attack by 

other pests.

Similar Insects and 

Diseases: Damage may be similar 

to that caused by other agents that 

discolor needles such as black 

pineleaf scale, pine needle casts, 

winter desiccation, drought, and 

aphids. If scales are present, 

diagnosis is assured.

References: 8, 32

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 73. Closeup of pine 

needle scale.

Figure 74. Ponderosa pine 

branch with pine needle scale.
50

Ponderosa Pine Resin Midge

Cecidomyia piniinopis (Osten Sacken)

Host: Ponderosa pine

Symptoms/signs: 

The first signs of injury are 

noticeable in early summer 

when the new shoots start to 

droop, the foliage turns yellow 

and the shoot dies. Larvae are 

red in color and feed in pits 

under the bark of the current 

year’s shoots, causing twig 

deformities. Adult midges 

are small delicate flies, which 

resemble mosquitoes. They possess long antennae that are beaded in 

appearance along with a much reduced wing venation.

Biology: The ponderosa pine resin midge has one 

generation per year. Larvae overwinter in pits under the bark. In the 

spring, they make their way to the surface where they spin cocoons 

on needles.

Effects: 

Although yellowing 

and shoot death 

can be significant, 

these effects are 

not considered to 

be commercially 

important in most 

situations. 

Figure 75. Closeup of ponderosa pine 

resin midge damage.

Figure 76. Larva and pupa of ponderosa pine 

resin midge.

Sap-Sucking Insects, 

Gall Formers and Mites
51

Similar Insects and Diseases: Twig beetle (Pityophthorus

spp.) feeding may cause similar death of small twigs and branches on 

pines. 

References: 23, 45 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 77. Flagging damage to branches of 

ponderosa pine caused by ponderosa pine resin 

midge.
52

Pinyon Spindle Gall Midge

Pinyinia edulicola (Gagné)

Host: Piñon

Symptoms/Signs: Presence 

of spindle-like swellings at the base of 

needles that are about 1 cm long with 

tiny, orange maggots inside.

Biology: Adults lay eggs on 

needles in late June and early July. 

Larvae hatch soon afterward and mine 

into the current year’s needles near the 

base. The plant forms a gall around the 

feeding larvae. Each gall contains 5 to 40 

small, orange legless maggots. The larvae 

overwinter in the galls and pupate in the 

spring

Effects: This is a common forest insect that rarely causes 

serious damage. However, heavy infestations in urban settings cause 

serious defoliation when needles drop prematurely.

References: 8, 23 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 78. Gall on piñon 

caused by pinyon spindle 

gall midge.

Figure 79. 

Orange-colored 

maggots of pinyon 

spindle gall 

midge.
53

Spittlebugs

Aphrophora spp., Clastoptera spp.

Hosts: Oak, juniper, and southwestern dwarf mistletoe

Symptoms/signs: The most conspicuous evidence of 

infestation is the spittle-like froth that surrounds the feeding nymphs.

Biology: 

Adults usually lay eggs 

just under the bark of 

twigs in summer. Eggs 

overwinter and hatch 

in spring. Nymphs feed 

on twigs and leaves 

and cover themselves 

with spittle. The spittle 

protects nymphs from 

drying and discourages 

natural enemies. Nymphs 

migrate to foliage in 

July and August where 

they transform to adults. 

Nymphs and adults feed on 

the sap of their hosts via 

their piercing mouthparts. 

The main natural controls include hot, dry weather that can desiccate 

the nymphs and a variety of natural enemies including wasp and fly 

parasites, ants, spiders and birds.

Effects: When these insects are abundant, their feeding can 

cause discoloration and sometimes mortality of infested twigs. 

Similar Insects and Diseases: The juniper twig girdler, 

Styloxus bicolor, causes twig dieback and flagging on junipers, but 

may be distinguished from spittlebugs by looking closely at affected 

twigs. The twig girdler bores inside the twigs, leaving them hollow 

inside. 

References: 23 

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 80. “Spit” caused by spittlebug 

nymphs feeding on pine.
54

Spider Mites

Oligonychus spp.

Hosts: Conifers and hardwoods

Symptoms/signs: Spider 

mites suck plant juices with 

needle like mouthparts, which 

cause spotting, yellowing, fading, 

and premature drop of foliage. 

When populations are heavy, 

cast skins, webbed foliage, eggs, 

and other mite activity can be 

found. Adult spider mites are 

tiny greenish to reddish colored 

arachnids with black heads. 

Biology: There can be 

several generations per year. Spider mites have five stages and all but 

the egg stage bear legs.

Effects: Spider mites are mainly an ornamental tree problem 

and often go unnoticed in forested situations. Outbreaks of spider 

mites generally last 1 year and are kept under control by natural 

enemies, such as predatory mites.

Similar Insects and Diseases: Aphid feeding can have 

the same symptoms of yellowing, spotting or fading foliage. Adult 

aphids have winged and wingless individuals. In general, aphids are 

larger in size and have three pairs 

of legs instead of four. 

Leaf injury from 

compounds such as ozone may 

have similar symptoms such as 

yellowing, spotting, or fading.

References: 23, 45

Sap-Sucking Insects, 

Gall Formers and Mites

Figure 81. Adult spider mites.

Figure 82. Damage to juniper 

caused by spider mites.
55

Bark beetles are one of the most destructive insects in 

western coniferous forests. It has been estimated that 

90 percent of insect-caused tree mortality and more 

than 60 percent of the total insect-caused loss of wood growth in the 

United States is due to bark beetles. In the Southwest, bark beetle 

killed trees were scattered over more than 2 million acres between 

2001 and 2003.

The Southwest has a large complex of bark beetles 

composed of many genera and species. Frequently, several species 

are found attacking the same host tree and, therefore, it may be 

difficult to discern what species initiated the attack. Although species 

of Dendroctonus are the most notorious tree killers in the western 

United States, Ips species also play a very important role in pine 

forests of the Southwest.

Bark beetles derive their name from their habit of living 

and mining between the bark and wood of trees and shrubs. Adults 

excavate egg galleries in bark phloem. All bark beetle life stages are 

spent in the phloem, inner bark and bark, except when adults leave 

the tree in which they developed to fly to new host material. Bark 

beetles feed on the phloem during adult and larval stages.

Most bark beetles are considered secondary mortality 

agents because they prefer weakened host material. However, 

during environmental conditions favorable for beetle development, 

populations may build up rapidly and successfully attack healthy 

trees. Most bark beetles have a symbiotic relationship with blue-stain 

fungi. The blue stain fungi can completely penetrate the sapwood 

within a year. The fungi occlude the outer conducting tissues in the 

xylem that halts upward water translocation. This action, plus that of 

the bark beetle feeding, causes the death of a host tree.

Bark beetles produce chemical compounds called 

pheromones that are used to communicate with other beetles. 

Aggregation pheromones cause beetles to congregate in certain 

Bark Beetles
56

Bark Beetles

Figure 83. Bark 

beetle gallery 

patterns (a), 

adult beetles 

(b), and larvae 

(c) compared 

with woodborer 

larvae.

A

B C
57

areas and massattack trees. 

Anti-aggregation 

pheromones 

cause beetles 

to disperse to 

neighboring trees 

or other areas. 

Pheromones 

of many bark 

beetles have 

been identified 

and synthetically 

produced. Both 

aggregation and 

anti-aggregation 

pheromones have 

been effective to 

mitigate impacts 

caused by some 

bark beetles 

in the western 

United States. 

Crowns 

of successfully 

attacked trees 

turn from green 

to yellow to 

reddish brown. 

This color 

Bark Beetles

Figure 84. Life stages of 

bark beetles (adult, pupa, 

larva).

Figure 85. Adult 

Arizona fivespined ips

(top) and western pine 

beetle (bottom). Note 

differences in the elytral 

declivity between the 

species.

Figure 86. Exit holes of bark beetles emerging from 

ponderosa pine.
58

change, an indication of a dying 

tree, may occur from a month to 

more than 2 years after successful 

attack depending on the temperature, 

moisture conditions, and density of 

beetles in the tree. Close inspection 

of infested tree trunks will show 

either small globules of resin, small 

holes through the bark, or reddish 

boring dust in bark crevices and 

around the tree base. The removal of 

bark from infested trees will reveal 

two types of galleries, egg and 

larval. Egg galleries constructed by adult beetles are rather uniform 

in width. Larval galleries depart at right angles from egg galleries 

and increase in size as the young grow.

References: 23, 24, 40, 115 

Bark Beetles

Figure 87. Small rust-colored 

pitch tubes are a sign that trees 

have been attacked by bark 

beetles.

Figure 88. Boring dust in branch crotches, 

bark crevices or around the base of trees 

is a sign that trees have been successfully 

attacked by bark beetles.

Figure 89. Blue stain fungi 

introduced during bark beetle 

attacks on conifers occurs in the 

sapwood.
59

Pine Engravers

Ips spp.

Hosts: Ponderosa pine and piñon

Symptoms/signs: In 

standing trees, fading tops of 

large trees or whole crowns in 

small trees can be indicators 

of Ips infestation. Other 

external evidence consists of 

accumulations of boring dust 

in bark crevices and at the base 

of the tree. Occasionally pitch 

tubes can be found on the trunk. 

Characteristic egg galleries may 

be found under the bark, slightly 

engraving the sapwood, hence the 

common name engraver beetle. 

In slash, look for boring dust and 

galleries.

Adults are small 

cylindrically shaped brown beetles 

a few millimeters in length. They 

possess a pronounced concavity 

at the rear end of the elytra that is 

bordered on either side by three to 

six tooth-like spines. Larvae are 

white, legless grubs.

Bark Beetles

Figure 90. Egg galleries of Ips pini 

on fire-damaged ponderosa pine. 

Note egg galleries radiate outward 

from centralized nuptial chamber.

Figure 91. Overwintering adult 

feeding galleries of Arizona 

fivespined ips on ponderosa pine log.

Figure 92. Adult Arizona fivespined ips 

beetle. Note spines along posterior edge 

of the elytral declivity.
60

Biology: Beetles produce 

2 to 4 generations per year, 

depending on climate, species, 

and elevation. In spring, adult 

beetles emerge from material 

infested the previous fall and 

fly to attack new hosts. Beetles 

prefer fresh debris from logging, 

construction activity or natural 

events, but during outbreaks 

living trees may be attacked. 

Effects: Bark beetles in 

this genus have the potential to 

kill thousands of pine trees during 

short-lived outbreaks in Arizona 

and New Mexico. Pine mortality 

is frequently noticed in drought 

years. Pinyon ips (I. confusus) killed 

millions of drought-stressed piñon 

across the Southwest from 2002 to 

2004. Similarly, the pine engraver 

beetle (I. pini) and the Arizona 

five-spined ips (I. lecontei) killed 

millions of ponderosa pine during the 

same time span throughout Arizona. 

Some outbreaks are associated with 

human activities that create large 

amounts of fresh pine debris or 

that weaken trees. These insects are 

also beneficial, creating snags and 

providing a food source for other 

animals.

Bark Beetles

Figure 93. Frass piles indicating 

Ips attacks on fresh ponderosa pine 

slash.

Figure 94. Ips species typically 

initiate attacks near the top 

of ponderosa pine causing a 

characteristic top-down fading 

pattern.
61

Similar 

Insects and 

Diseases: Other bark 

beetles may be found 

in southwestern 

pines. They may 

be distinguished 

by egg gallery 

characteristics and 

adult appearance. Ips 

egg galleries possess 

a nuptial chamber—

an enlarged excavated 

area—with one 

to many galleries 

radiating from it. 

The egg galleries are 

free of frass. Dendroctonus galleries 

vary by species in shape but lack the 

nuptial chamber and are packed with 

frass. Ips adults display a pronounced 

concavity at the rear end of the elytra, 

which contains three to six spines 

on either side. Dendroctonus adults 

on the other hand have a rounded 

declivity with no spines. Frequently, 

both Dendroctonus and Ips species 

occur within the same tree with Ips

species typically located in the top 

half of the bole and Dendroctonus in 

the bottom half.

References: 24, 48, 52, 61, 75 

Bark Beetles

Figure 95. Stand level ponderosa pine mortality 

caused by Arizona fivespined ips on Prescott NF, 

Arizona.

Figure 96. Initial construction 

of egg galleries by pinyon ips 

on piñon.
62

Bark Beetles

Figure 97. Adult pinyon 

ips feeding colonies are 

frequently found near the 

base of piñon during the fall 

through early spring.

Figure 98. Pitch tubes caused by pinyon ips 

attacks. 

Figure 99. Boring dust in 

bark crevices near base of 

pinyon ips attacked piñon 

(left).

Figure 100. Landscape 

level piñon mortality 

caused by pinyon ips in 

New Mexico (right).
63

Western Pine Beetle

Dendroctonus brevicomis (LeConte)

Host: Ponderosa pine

Symptoms/signs: Larval feeding in the inner bark and 

adult mating and egg laying creates mazelike galleries. Entrance 

holes, reddish dust in bark crevices, and pitch tubes are indicators of 

attack. Exit holes are created when the mature beetle leaves the host. 

Trees, which have been successfully attacked by beetles, are most 

noticeable when the foliage begins to fade from green to yellow to 

red to gray. Also, infested 

trees often exhibit signs 

of woodpecker feeding 

activity in the bottom half 

of the bole. Needles fall 

off approximately 1 year 

after the initial attack.

Biology: Adult 

beetles usually begin 

flight and attack of 

suitable host trees in late 

spring or early summer 

and continue until cold 

weather begins. Females 

produce from one to 

three broods a year. Eggs 

are laid in niches along 

galleries. When the eggs 

hatch, the larvae feed in 

the inner bark working 

away from the egg 

gallery. 

Effects: The 

direct effect of successful 

attack is tree mortality. 

Usually, the beetles breed 

Bark Beetles

Figure 101. Egg gallery of western pine 

beetle on ponderosa pine. Note that 

galleries have a crisscrossing, serpentine 

pattern.

Figure 102. Cross section of bark showing 

western pine beetle larvae in outer bark.

➚
64

in and kill scattered, overmature, slow 

growing, decadent, or diseased trees 

and trees weakened by stand stagnation, 

lightning, fire, or mechanical injury. 

This tree mortality may be considered 

part of the normal ecological process of 

succession during which a forest matures 

and replaces itself. Epidemics can affect 

ponderosa pine ecosystems by reducing 

the density and size distribution of its 

host, and altering species composition 

and stand structure.

Similar Insects and Diseases: 

Other bark beetles attacking ponderosa 

pine. Western pine beetle egg galleries 

can be distinguished from other beetles 

by 

their 

maze-like appearance.

References: 17, 23 

Bark Beetles

Figure 104. Woodpecker activity 

(“flaking off of bark”) on 

ponderosa pine indicating that 

western pine beetle larvae are in 

the outer bark.

Figure 103. Pitch tubes 

indicating western pine 

beetle attack are frequently 

small in size (<1/4 inch, 6.4 

mm).
65

Mountain Pine Beetle

Dendroctonus ponderosae (Hopkins)

Hosts: Ponderosa pine, white pines

Symptoms/signs: External evidence on green infested trees 

consists of pitch tubes. On successfully attacked trees, these are 

small and numerous. Pitch tubes on unsuccessfully attacked trees 

are larger in size (around 2 cm in 

diameter), typically white, and widely 

scattered over the trunk. During 

drought years, infested trees may not 

produce pitch, and external evidence 

consists only of boring dust. These 

are referred to as blind attacks. Later, 

foliage on successfully attacked trees 

fades to yellowish green, to sorrel, red 

and finally brown. Under the bark, egg 

galleries are straight, vertical, 

and packed with boring dust. 

They range from 10 to 122 cm in 

length. Adult beetles are brown 

cylindrically shaped beetles about 

4 to 7.5 mm long. Larvae are small 

white grubs with tan head capsules.

Biology: The beetle 

produces one generation per year. 

Adults begin attacking trees in 

early July and the attack period 

can extend into September. 

Females initiate attacks and release 

pheromones to attract males. 

Beetles create egg galleries in 

the inner bark and females lay 

eggs. In 1 to 2 weeks small larvae 

Bark Beetles

Figure 105. Adult mountain 

pine beetle.

Figure 106. Egg larval galleries 

of mountain pine beetle on limber 

pine. Note that egg galleries have 

an initial “crook” or “j” and then 

run vertically up the bole. Larval 

galleries run perpendicular to egg 

galleries.
66

hatch. Generally they overwinter as small larvae. Larvae resume 

development the following spring and when mature, excavate oval 

cells in which they transform into pupae and then adults. Adults 

then bore out and attack new trees. In the Southwest on ponderosa 

pine, this insect is found primarily on the Kaibab Plateau in northern 

Arizona and in northern New Mexico. It can be found on white pines 

throughout the Southwest.

Effects: The direct effect of successful attack is tree 

mortality. Epidemics can affect ponderosa pine ecosystems by 

reducing the density and size distribution of its host, and altering 

species composition and stand structure.

Similar Insects and Diseases: Several other bark 

beetles may be found in Southwestern ponderosa pine, including 

other Dendroctonus species and engraver beetles. These may 

be distinguished from mountain pine beetle by their egg gallery 

characteristics and adult appearance. Egg galleries of the western 

pine beetle are maze-like, and those of the roundheaded pine beetle 

are vertical and slightly sinuous. Galleries of engraver beetles 

possess a nuptial chamber with one to several galleries radiating out 

from it. Engraver beetle 

egg galleries are free of 

frass. Ips adults display a 

pronounced concavity at the 

rear end of the elytra that 

possesses three to six spines 

on either side. The elytral 

declivity on Dendroctonus 

adults is rounded and does 

not possess any spines.

References: 1, 74 

Bark Beetles

Figure 107. Ponderosa pine mortality 

caused by mountain pine beetle.
67

Roundheaded Pine Beetle

Dendroctonus adjunctus (Blandford)

Host: Ponderosa pine

Symptoms/Signs: 

Reddish brown boring dust 

is present in bark crevices 

and numerous pitch tubes 

are observed on the bark at 

entrance holes. In heavily 

attacked decadent trees, pitch 

tubes are often missing or very 

small. Later, the foliage fades 

from green to yellow or bright 

red, and eventually a dull 

brown. Woodpecker activity 

on the trunk is also a good 

indication that bark beetles 

have attacked the tree.

Biology: Adult 

roundheaded bark beetles 

attack and colonize 

susceptible trees in October 

and November. Females 

initiate the attack producing 

an aggregation pheromone 

drawing large numbers of beetles to the tree. The beetles chew 

through the bark and excavate a chamber in the moist tissue beneath 

the bark. Males enter the chamber and mating occurs. Female beetles 

then excavate horizontal tunnels in the inner bark region for 25 to 50 

mm and then longitudinally with the grain an average distance of 300 

mm. Eggs are laid individually in niches on alternate sides of the egg 

galleries, which are packed with frass. The larvae mine across the 

grain in the inner bark until in the third instar and then bore into the 

outer bark to complete development.

Bark Beetles

Figure 108. Egg gallery of 

roundheaded pine beetle. Note that 

galleries are vertical, but more “snakelike” in appearance than mountain 

pine beetle egg galleries.
68

Effects: Roundheaded pine beetles attack, colonize, 

and kill trees in the southwestern United States and Mexico. 

Periodic outbreaks have killed large numbers of ponderosa pine 

in southern New Mexico 

and southeastern Arizona. 

In 1950, 16,000 pole and 

sawtimber-sized trees were 

infested on 2,500 acres near 

Cloudcroft and 400,000 

pole-sized ponderosa pines 

were killed on 150,000 acres 

from Mayhill to Ruidoso 

in 1971. Similar outbreaks 

occurred during the 1990s in 

the Sacramento Mountains 

in southern New Mexico and 

the Pinaleño Mountains in 

southeast Arizona.

Similar Insects: 

The roundheaded pine 

beetle is similar to other 

Dendroctonus beetles, Ips

beetles, and other members 

of the subfamily Scolytidae. Dendroctonus beetles are distinguished 

from each other mainly by their unique egg galleries and, in the 

case of the Douglas-fir beetle and spruce beetles by the host species 

they attack. Dendroctonus beetles are distinguished from Ips beetles 

by their rounded posterior ends and galleries, which are packed 

with frass. In contrast, the posterior ends of Ips beetles are slightly 

concave with and have several to many small spines and the runways 

(egg galleries) are free of frass. 

References: 8, 23, 60 

Figure 109. Pitch tubes caused by 

roundheaded pine beetle attacks on 

ponderosa pine.

Bark Beetles
69

Bark Beetles

Figure 110. 

Ponderosa pine 

mortality caused 

by roundheaded 

pine beetle in 

the Pinaleño 

Mountains, Arizona.

Figure 111. 

Aerial view of 

ponderosa pine 

mortality caused 

by roundheaded 

pine beetle in 

the Pinaleño 

Mountains, Arizona.
70

Southern Pine Beetle and Mexican Pine Beetle

Dendroctonus frontalis (Zimmerman) 

and Dendroctonus mexicanus (Hopkins)

Hosts: Chihuahua, Apache, ponderosa pines

Symptoms/signs: Presence of reddish brown boring dust 

caught in bark flakes and crevices around tree; numerous pitch tubes 

on the bark at the entry point of the tunnels. In heavily attacked 

decadent trees, pitch tubes are often missing or so small they can 

only be seen up close. Later, the foliage begins to fade, turning 

from green to yellow or bright red, and eventually a dull brown. 

Woodpecker activity on the trunk is also a good indication that bark 

beetles have attacked the tree.

Adults are dark reddish brown, cylindrically shaped beetles 

approximately 

3 mm in length. 

Larvae are white, 

legless grubs. 

The morphology 

of southern 

pine beetle 

and Mexican 

pine beetle are 

very similar 

and, therefore, 

are difficult 

to tell apart. 

Taxonomists use 

the seminal rod of 

male beetles as the distinguishing characteristic.

Biology: Although little is known of the southern pine 

beetle biology in the Southwest, this beetle may have 3 to 11 

generations in the southeastern U.S. depending on latitude, elevation, 

and climate. Both southern pine beetle and Mexican pine beetle 

seem to have only one generation per year in the Southwest. 

Bark Beetles

Figure 112. Egg galleries of southern pine beetle on 

Chihuahua pine. Note that egg galleries are “mazelike” with branching and interconnections. 
71

Adults construct winding galleries in the inner bark, where eggs 

are deposited in individual niches on each side of the galleries. The 

larvae mine for a short distance before boring into the outer bark 

where they pupate. Mexican pine beetle is thought to have a similar 

biology.

Effects: Southern pine beetle and Mexican pine beetle 

killed large numbers of Apache and Chihuahua pines throughout 

1999-2001 in the Chiricahua Mountains of southeastern Arizona. 

Pine mortality ranged from single trees to large groups of more than 

100. Southern pine beetle has been collected from traps in northern 

Arizona.

Similar Insects and Diseases: Southern pine beetle and 

Mexican pine beetle can be distinguished from other pine bark 

beetles by the shape of egg galleries and beetle morphology.

References: 103 

Bark Beetles

Figure 113. Chihuahua pine mortality caused by southern 

pine beetle in Chiricahua Mountains, Arizona.
72

Red Turpentine Beetle

Dendroctonus valens (LeConte)

Hosts: Pines

Symptoms/signs: 

The best indicators of red 

turpentine beetle attack on 

pines are: large pink-white 

pitch tubes on the lower bole; 

accumulations of reddish 

brown sawdust at the base of 

the tree and in bark crevices; 

and accumulations of cream to 

pink colored crystallized resin 

granules at the tree base. The 

egg galleries under the bark 

are fairly wide and linear to 

irregular in shape. Galleries extend downward from the entry hole 7 

cm to 1 m and may even extend into large roots.

Adults are reddish brown, cylindrically shaped beetles 

approximately 8 mm in length. Larvae are white, legless grubs.

Biology: The number of generations varies from 1 to 2 years 

in the coldest portions of its 

range to 2 to 3 generations 

per year in the warmest 

areas. Attacks are made 

in the lower bole of pines. 

Attacks occur throughout 

warm weather but peak by 

midsummer. These beetles 

often attack trees scarred by 

fire.

Effects: Through 

repeated attacks this beetle 

can sometimes kill trees; 

Bark Beetles

Figure 114. Large pitch tubes at 

bases of ponderosa pine indicate red 

turpentine beetle attacks.

Figure 115. Red turpentine beetle 

frequently attacks fire-damaged ponderosa 

pine as indicated by pitch tubes and frass.
73

B

however, more often it 

weakens trees, predisposing 

them to fatal attack by 

other bark beetle species. In 

successful attacks, a patch 

of bark ranging from a few 

square cm to a square m or 

more may be killed. Red turpentine 

beetles frequently colonize firescorched ponderosa pines.

Similar Insects and 

Diseases: This beetle is distinguished 

from other bark beetles by the large 

size of the pitch tubes, galleries and 

the beetle itself.

References: 2, 23, 94 

Bark Beetles

Figure 116. Granola-like 

crystallized resin material can 

occur (a) around bases of pine 

trees attacked by red turpentine 

beetle or (b) even below the soil 

on primary roots.

Figure 117. Egg and 

larval galleries of red 

turpentine beetle. Note 

that larval feeding occurs 

in a gregarious fashion.

A
74

Spruce Beetle

Dendroctonus rufipennis (Kirby)

Hosts: Engelmann 

spruce is principal host, blue 

spruce is an infrequent host

Symptoms/signs: 

External evidence on green 

infested trees consists of entrance 

holes in the bark and occasional 

pitch tubes. However, pitch 

tubes are often indicative of an 

unsuccessful attack. Red boring 

dust from entrance holes usually 

accumulates in bark crevices 

around the bases of infested 

trees. Woodpeckers frequently 

remove large sections of bark 

looking for larvae to feed on. 

About 1 year after attack, needles 

of infested trees usually turn a 

yellowish green and fall, though 

some may remain green until the 

Bark Beetles

Figure 118. Egg and larval 

galleries of spruce beetle. Egg 

galleries are vertical with eggs laid 

on alternate sides 

of the gallery.

Figure 

119. Fading 

Engelmann 

spruce mortality 

caused by 

spruce beetle 

in White 

Mountains, 

Arizona.
75

second year. Needles do not turn a reddish color like those on bark 

beetle infested pines. Under the bark, egg galleries are vertical and 

slightly groove the xylem. Egg galleries range from about 6 to 30 cm 

long. Adult beetles are 

cylindrically shaped and 

4 to 6 mm long. They are 

generally dark brown to 

black with reddish brown 

wing covers; however, 

older adults are usually 

entirely black. Larvae are 

creamy white, cylindrical, 

legless grubs. Larvae 

reach a length of about 6 

mm. Pupae are creamy 

white and similar in size 

to the adult.

Biology: Spruce 

beetles generally produce 

one generation in 2 years; however, generation time can take from 

1 to 3 years. Adults emerge from May through July and begin 

attacking new host trees. Eggs hatch and larvae develop during the 

summer. Broods overwinter as larvae or callow adults and complete 

development to mature adults by the following August. Spruce 

beetle attacks standing trees, windthrown trees, or logging residuals. 

It prefers large diameter, green downed material to standing trees. 

Populations are affected by a number of factors including the number 

of susceptible hosts, natural enemies, and extreme cold.

Effects: The direct effect of spruce beetle attack is tree 

mortality or in some cases strip kill, when only a vertical section 

of the bole is attacked. Strip attacked trees often die in subsequent 

years. Spruce beetle epidemics can have both immediate and longBark Beetles

Figure 120. Engelmann spruce mortality 

caused by spruce beetle on the Pinaleño 

Mountains, Arizona.
76

term effects on spruce-fir forests. The immediate effects include 

changes in stand structure and composition. The longer-term effects 

come from successional changes that result from microclimate 

changes as well. 

Similar Insects and Diseases: The most common 

associates are in the genus Ips. In New Mexico, I. pilifrons sulcifrons

is the most common, while in Arizona, I. pilifrons utahensis is found 

most often. Ips beetles frequently infest the upper (exposed) portion 

of downed material, while spruce beetle favors the shaded material. 

Ips egg galleries differ from those of spruce beetle by containing a 

nuptial chamber and by being free of frass.

References: 41, 86 

Bark Beetles

Figure 121. Flaking of bark caused by 

woodpeckers indicates spruce beetle larvae in 

the outer bark of Engelmann spruce.
77

Douglas-fir Beetle

Dendroctonus pseudotsugae (Hopkins)

Host: Douglas-fir

Symptoms/signs: Reddishorange frass is the first sign that a tree has 

been attacked. At times, the most evident 

sign of attack is the clear resin exuding 

from entrance holes on the upper portions 

of the stem. Pitch flow, however, is not 

always present on successfully attacked 

trees. Needles of successfully attacked 

trees change from green to yellow to 

sorrel to reddish brown in the year 

following attack. Egg galleries run parallel 

to the wood grain and are 20 to 25 cm 

long. Adult beetles are stout, cylindricallyshaped, and 4 to 6 mm long. The head 

and thorax 

are black; the 

wing covers 

reddish brown, 

becoming darker with age.

Biology: The Douglas-fir beetle 

has one generation per year. Although 

adult flight times vary by year, most 

new attacks occur in late spring to early 

summer. Broods develop under the bark 

throughout the summer and early fall. 

Adult, pupal, or larval life stages can 

overwinter. Brood that develops to pupae 

or adults by winter usually emerges 

between April and June. Overwintering 

larvae emerge as adults in summer. A 

small percentage of adults that overwinter 

will re-emerge from the spring-attacked 

Bark Beetles

Figure 122. Egg and 

larval galleries of 

Douglas-fir beetle. Note 

larval galleries occur in 

alternating groups.

Figure 123. Douglas-fir 

beetle caused mortality of 

dwarf mistletoe-infected 

Douglas-fir on the San 

Francisco Peaks, Arizona.
78

trees and attack additional 

trees in the middle of summer. 

Typically, late-season attacks 

account for less than 20 percent 

of all attacks in one season.

Effects: The direct 

effect of successful attack 

is tree mortality. At low or 

endemic levels, the beetle infests 

scattered trees that are infected 

with dwarf mistletoe and/or 

armillaria root disease, injured 

by fire, or stressed by defoliating 

agents. During outbreaks, groups of 100 or more attacked trees are 

common. Douglas-fir beetle epidemics can have both immediate and 

long-term effects on mixed conifer 

forests. Immediate effects include 

changes in stand structure and 

composition. Successional (longterm) changes result from alterations 

in microclimate. 

Similar Insects and 

Diseases: Other bark beetles, 

Scolytus monticolae and Douglasfir pole beetle (Pseudohylesinus 

nebulosus), often occur in large 

branches, boles of pole-sized 

trees and the top of trees killed by 

Douglas-fir beetle. They may be 

separated by gallery patterns and 

characteristics of adult beetles. 

References: 23, 89 

Bark Beetles

Figure 125. Galleries of 

Douglas-fir pole beetle on small 

diameter Douglas-fir. Galleries 

are short, longitudinal and often 

with two branches.

Figure 124. Frass (boring dust) in 

bark crevices, spider webs, or at base 

of Douglas-fir indicates successful 

attack by Douglas-fir beetle.
79

Western Balsam Bark Beetle

Dryocoetes confusus (Swaine)

Host: Subalpine fir (corkbark fir)

Symptoms/signs: Small entrance holes and boring dust 

are usually difficult to detect on green standing trees, but pitch flow 

may be evident. Under the bark, egg galleries lightly etch the surface 

of the wood. Egg galleries radiate from a central nuptial chamber. 

Attacked trees generally turn yellow-red within a year. Needles on a 

beetle-killed fir may remain for more than 4 years. Adults are shiny, 

dark brown, cylindrical beetles about 2 to 5 mm long. The posterior 

end of the elytra is 

abruptly rounded 

with no spines.

Biology: 

Little is published 

on the biology of 

this species. A 1- to 

2-year life cycle 

is indicated. The 

lower to mid bole 

of standing trees 

is usually selected 

for attack. This 

Bark Beetles

Figure 126. Egg gallery of western balsam bark 

beetle on corkbark fir. Egg galleries typically have 

five or more galleries radiating from a nuptial 

chamber.

Figure 127. Adult western balsam 

bark beetle. Note the “crew cut” 

appearance on front of beetle 

heads.
80

species is moderately aggressive 

and capable of killing older and/or 

weakened trees. Occasionally cut 

or fallen trees are attacked.

Effects: The direct 

effect of successful attack is tree 

mortality.

Similar Insects and 

Diseases: Other bark beetles 

attack subalpine fir, including 

species of Scolytus and 

Pseudohylesinus. They may be 

separated by gallery patterns and 

characteristics of adult beetles. 

Western balsam bark beetle 

attacks are frequently associated 

with fir infected by root diseases.

References: 23, 64, 115 

Bark Beetles

Figure 128. Corkbark fir mortality 

caused by western balsam bark 

beetle on the San Francisco Peaks, 

Arizona. 
81

Fir Engraver

Scolytus ventralis (LeConte)

Hosts: True firs

Symptoms/signs: Freshly attacked green trees have tiny 

holes in the bark, reddish-brown boring dust in bark crevices, and 

streams of clear pitch 

exuding from entrance 

holes. Needles change 

from green to yellowgreen to sorrel and then 

red to brown. Larvae, 

pupae, and egg are 

found in the inner bark; 

egg and larval galleries 

deeply score the wood, 

creating characteristic 

horizontal egg galleries 

and vertical larval 

galleries. Adult beetles 

are small, shiny, black 

beetles about 4 mm 

long. The abdomen is 

incurved at the rear.

Biology: In 

warm locations, the 

fir engraver completes 

one generation and a partial second generation each year. In cooler 

sites, the beetle needs 2 years to 

complete its life cycle. Adult flight 

Bark Beetles

Figure 129. Egg and larval galleries of fir 

engraver. Galleries are horizontal with two 

branches radiating out from entrance point.

Figure 130. Adult fir engraver 

beetle. Note the “sawed-off” 

appearance of the beetles’ 

abdomen.
82

occurs throughout the 

summer, but peaks in July 

and August. Fir engravers 

overwinter primarily as 

young or mature larvae. 

In the spring, they feed 

for a short period and 

then construct pupal 

cells at the end of their 

galleries.

Effects: Fir 

engravers are a major 

mortality agent of true 

firs, usually attacking 

pole-sized to sawtimbersized trees. Outbreaks 

often occur during and 

following droughts. 

Root diseases are often 

associated with attacked 

trees. The fir engraver 

can also breed in slash 

and wind-thrown trees. 

Flagging (death of branches) may occur on fir trees that have been 

only partially attacked.

Similar Insects and Diseases: Other bark beetles attack 

subalpine fir, including species of Dryocoetes and Pseudohylesinus. 

They may be separated by gallery patterns and characteristics of 

adult beetles.

References: 3, 19, 23 

Bark Beetles

Figure 131. White fir mortality caused by fir 

engraver on Mormon Mountain, Arizona.
83

Twig Beetles

Pityophthorus spp., 

Pityogenes spp., Pityoborus secundus

Hosts: Ponderosa 

pine, piñon, and other conifers

Symptoms/Signs: 

Trees attacked and colonized 

by twig beetles exhibit fading 

needles on twigs and branches, 

and twig and branch dieback 

throughout the crown. Tan 

sawdust is produced around 

the attack sites. On smaller 

twigs and branches, most of the 

cambium is mined beneath the 

bark. Small, star-shaped egg 

galleries generally occur under 

the bark of the larger branches 

and small trunks.

Biology: Adult twig 

beetles are about 3 mm long 

and dark brown. Most species 

Bark Beetles

Figure 132. Pitch tubes of twig beetles 

on piñon are typically very small (<1/8 

inch).

Figure 133. Damage to 

ends of piñon branches 

caused by twig beetles. 

Very small pitch tubes 

may be present on 

twigs.
84

have a rounded rear end, but a few have a pair of short spines. The 

larvae are fat, white, C-shaped grubs with light brown head capsules 

and feed under the bark. Most species have 2 to 4 generations per 

year, depending on local conditions.

Effects: Typically attacks and kills small twigs and 

branches of drought stressed or otherwise weakened pines and other 

conifers. Although 

twig beetles are 

generally considered of 

secondary importance, 

under favorable 

conditions they may 

develop in sufficiently 

high numbers and 

attack and kill small 

trees. Pityogenes 

carinulatus killed 

thousands of young 

ponderosa pine in 1967 

in New Mexico as a 

result of populations 

increasing in thinning 

and logging slash. Twig beetles infested high numbers of young 

piñon in 2002, 2003, and 2004 across New Mexico and Arizona.

Similar Insects and Diseases: See Ips discussion. Most 

twig beetles have elytral declivity and egg galleries that are 

somewhat similar to Ips; however, twig beetles are smaller in size 

and are typically found in branches and very small diameter trees.

References: 9, 23 

Bark Beetles

Figure 134. Mortality of piñon regeneration 

killed by twig beetles near Los Alamos, NM.
85

Cedar Bark Beetles

Phloeosinus spp.

Hosts: Arizona cypress and junipers

Symptoms/signs: External evidence consists of twig killing 

(called flagging), or whole trees fading. Under the bark, egg galleries 

are simple and longitudinal, 2 to 7 cm 

long, usually engraving the wood rather 

deeply. Egg niches are usually rather large 

and conspicuous. Larval galleries wander 

away from the parent galleries.

Adults are reddish brown to black, 

shiny beetles ranging in size from 2 to 4 

mm long. Larvae are small white grubs, 

with brown head capsules.

Biology: One to one and a half 

generations are produced per year. Attacks 

occur in spring and summer. Adults and 

larvae feed in the inner bark in galleries. 

Newly emerged adults feed on the pith of 

twigs of living trees prior to constructing 

egg galleries. Often twigs are hollowed 

out completely and killed.

Bark Beetles

Figure 135. Egg and 

larval galleries of cedar 

bark beetle. Egg galleries 

have a “thermometer” or 

“centipede” shaped pattern.

Figure 136. Juniper mortality 

caused by cedar bark beetle near 

Flagstaff, Arizona.

Figure 137. Pitch tubes on 

Arizona cypress caused by 

cypress bark beetle near Sedona, 

Arizona. Note that pitch tubes are 

frequently absent.
86

Effects: Main effects on their 

hosts are twig killing or tree mortality; 

however, these insects are not aggressive 

and are generally found attacking trunks, 

tops and limbs of weakened, dying or 

felled trees. Occasionally outbreaks occur. 

Similar Insects and Diseases: 

This is the main bark beetle genus 

attacking cypress and juniper. There are 

some woodboring beetles that attack these 

trees. Bark beetles are distinguished from 

woodborers by the shape and location of 

the galleries and size of the adults and 

larvae. Galleries of woodborers extend 

both in the bark and wood. Woodborer 

larvae and adults are larger than bark 

beetles.

References: 23, 81 

Bark Beetles

Figure 138. Exit holes 

of cypress bark beetle 

on Arizona cypress near 

Sedona, Arizona.

Figure 139. Arizona 

cypress killed by cypress 

bark beetle near Sedona, 

Arizona.

Figure 140. 

Extensive 

mortality 

caused by 

cypress bark 

beetle north 

of Clifton, 

Arizona.
87

This group contains members of several orders 

(Lepidoptera, Hymenoptera, and Coleoptera) that 

bore into the sapwood and sometimes the heartwood 

of weakened, fire-scorched, recently felled, or dead hardwood and 

conifer trees. Descriptions here include the long-horned beetles or 

round-headed borers (Coleoptera: Cerambycidae), the ambrosia 

beetles (Coleoptera: 

Scolytidae), the 

flat-headed or 

metallic woodborers 

(Coleoptera: 

Buprestidae), 

the horntails 

(Hymenoptera: 

Siricidae), and 

clearwinged moths 

(Lepidoptera: 

Aegeriidae). 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.

Reference: 23, 40

Wood Borers

Figure 141. Egg niches of cerambycid wood 

borers are oval shaped pits in the bark with a slit 

in the bottom.

Figure 142. Larva of roundheaded 

wood borer on limber pine attacked by 

mountain pine beetle.
88

Wood Borers

Wood Borers

Roundheaded borers, Cerambydidae

Flatheaded borers, Buprestidae

Hosts: Conifers and hardwoods

Symptoms/signs: Larvae are found under the bark of dead 

and dying trees. These galleries are usually wider than bark beetle 

galleries and vary in diameter as the larva grows, in contrast to 

the egg galleries of bark beetles which have a uniform diameter 

throughout. Roundheaded borer galleries are packed with a coarse 

boring material while flatheaded borer galleries are packed with fine 

boring dust. In many species, larvae complete their development 

in the wood so tunnels extend into sapwood and sometimes the 

heartwood. Adults emerge through large emergence holes in the bark.

Adult roundheaded borers are medium to large sized, oblong 

to cylindrical insects. The antennae are often longer than the body, 

giving them the name “longhorned beetles.” Larvae are relatively 

large, particularly when fully developed, white, cylindrically shaped 

grubs. The heads are slightly larger in diameter than the body.

Adult flatheaded borers are medium to large sized, flattened, 

compact, and often brightly colored beetles. Larvae have a very 

distinctive shape. The first 

body segment behind the 

head is much broader than the 

following body segments and 

has horny plates on the top and 

bottom.

Effects: These insects 

primarily attack weakened, 

dead or dying trees. A few 

species attack and kill 

apparently healthy trees, such 

as the western cedar borer on 

junipers and Agrilus species 

on Populus. They often attack 

Figure 143. Adult longhorned beetles 

(adults of roundheaded wood borers). 

Note that antennae are longer than the 

length of the body.
89

trees already infested with bark beetles and sometimes compete with 

them. Larval mines penetrate both the cambial region as well as the 

wood, sometimes mining it extensively. They are important in the 

process of nutrient cycling by assisting in breaking down woody 

material.

Reference: 23

Wood Borers

Figure 145. Adult 

metallic wood 

borer (flatheaded 

wood borer). Note 

that antennae are 

shorter than the 

body.

Figure 144. Larva 

of flatheaded 

wood borer. Note 

that their flattened 

heads are usually 

broader than the 

body.
90

Juniper Borers

Trachykele blondeli (Marsuel)

Callidium spp

Atimia spp

Chrysobothris spp

Styloxus bicolor (Champlain and Knull)

Hosts: Junipers and Arizona cypress

Symptoms/signs: Exit holes.

Effects: Several roundheaded and flatheaded wood borers 

are aggressive pests in drought-stressed junipers and cypress. 

Damage can be extensive before symptoms are apparent. Usually a 

large portion of the tree or the entire tree dies before the insects’ exit 

holes are noticed.

Biology: Callidium spp. larvae bore beneath the bark 

making very wide tracks that distinctively score the outer sapwood 

much like a router. Older larvae excavate oval tunnels deep in the 

wood and overwinter. Adults emerge throughout the warm months 

of the year. There is one generation per year. Adult beetles are 

rather short-horned for cerambycids and dark blue or black. These 

roundheaded borers leave an oval or rectangular exit hole. 

Atimia spp. are small roundheaded borers about 6.5 mm 

long and generally have 

a 1-year life cycle. These 

longhorned beetles attack 

thin bark portions of 

seriously weakened and 

dead juniper and cypress. 

Trachykele 

blondeli, the western cedar 

borer, is 11 to 17 mm long 

and attacks juniper and 

Arizona cypress. Females 

lay eggs under bark scales 

and branches of living 

Wood Borers

Figure 146. Larval feeding galleries of the 

western cedar borer.
91

trees. Flatheaded larvae 

bore from the branches into 

the main bole. They feed 

primarily in the heartwood 

for several years. Adults 

emerge in the spring, leaving 

oval or rectangular exit 

holes.

Chrysobothris

spp. are flatheaded borers 

of junipers and Arizona 

cypress. They are mediumsized beetles about 11.5 mm 

long. Larvae bore into the bark and outer wood of weakened trees.

The juniper twig pruner, Styloxus bicolor, is a small 

roundheaded borer that mines the small branches and causes twig 

dieback during dry periods.

Similar Insects and Diseases: See cedar bark beetles.

References: 9, 23

Wood Borers

Figure 147. Larval feeding galleries and 

exit holes of the western cedar borer.

Figure 148. Juniper 

damage caused by 

western cedar borer.
92

Ambrosia Beetles

Trypodendron spp, Platypus spp, 

Gnathotrichus spp, Xyleborus spp

Hosts: True fir, spruce, Douglas-fir, pine, aspen, poplar, and 

maple

Symptoms/signs: Entrance holes are small for most species 

(1.5 mm or less) and are marked by piles of white boring dust. 

Gallery patterns vary by species, but all tunnels run perpendicular 

to wood grain. The mines of Platypus species penetrate into the 

heartwood in contrast with most ambrosia beetles in the Scolytidae 

that mine only the sapwood.

Effects:

Weakened, dying, 

recently cut or dead 

trees are attacked. 

Galleries cause defect 

in logs. Some species 

can attack freshly cut 

lumber before it has 

been dried. Populations 

can build up in 

windthrown and firekilled trees, bases of 

trees attacked by bark 

beetles, logging slash, 

and logs in storage. 

These beetles are 

unique among bark beetles in that larvae feed upon a special type of 

fungus, known as the ambrosia fungus, which grows in the galleries. 

Larvae do not feed on wood or phloem as in other bark beetles. 

Biology: Insect appearance varies between beetles. 

Adult Trypodendron, Gnathotrichus, and Xyleborus beetles are 

all dark colored, cylindrically shaped beetles, about 2 to 4.5 mm 

Wood Borers

Figure 149. White boring dust caused by 

ambrosia beetles tunneling in the wood of a 

bark beetle-killed pine.
93

long (depending on the 

species). Larvae are white, 

legless grubs with brown 

head capsules. All three 

genera belong to the family 

Scolytidae. Platypus on the 

other hand belongs to the 

family Platypodidae, which 

is closely related to the 

Scolytidae. Adult Platypus are 

more elongate, cylindrically 

shaped beetles than scolytids.

Similar Insects 

and Diseases: May be 

confused with other bark 

beetles; however, ambrosia 

beetles are the only ones that 

bore straight into the bole 

producing fine, white boring 

dust.

References: 23, 32

Figure 150. Entrance points of adult 

ambrosia beetle. Holes are stained by 

blue stain fungi.

Wood Borers
94

Cone and seed insects, also called conophytes, 

include a variety of moths, flies, bugs, and beetles. 

Destruction of forest seeds may be caused by 

insects that attack the buds, flowers, immature cones, and the seeds 

themselves. Because flower and seed production by forest trees 

varies dramatically from year to year and by location, so do impacts 

caused by cone and seed insects. In general, cone and seed insects 

are relatively unimportant under forest conditions as the amount 

of seed produced by forest trees usually far exceeds the number of 

seeds destroyed by these insects. However, they can have economic 

impacts to seed orchards in which seed production is limited. They 

can also impact natural regeneration of white pines that are being 

severely impacted by white pine blister rust. The most injurious 

groups of cone and seed insects in the Southwest are the seed moths 

and coneworms (Lepidoptera), seed worms and midges (Diptera), 

and cone beetles (Coleoptera). 

References: 5, 23, 36, 47, 87

Cone and Seed Insects
95

Cone Beetles

Conophthorus spp.

Hosts: Pines

Symptoms/signs: 

External evidence consists of 

pitch tubes at the point of entry 

on the cone stalk or the base of 

the cone. Following attack, cones 

turn brown and wither. If beetles 

have emerged, small round exit 

holes may be found on the outside 

of affected cones. Inside, beetles 

leave cones riddled with tunnels 

and frass. Adult beetles are reddish 

brown to black, shiny bark beetles. 

Larvae are small white, legless 

grubs.

Biology: One generation is produced per year. Adult beetles 

bore into the base or stem of immature second-year cones in the 

spring. A gallery is created along the cone axis, with eggs deposited 

along its sides. The creation of the gallery severs the conductive 

tissues of the cone, killing it. Larvae hatch and feed on the scales, 

seeds, and tissues of the cone. The brood complete development 

during the summer within the 

cone, and usually overwinter 

there. Some new adults emerge 

and may bore into shoots or 

conelets and overwinter.

Effects: These beetles 

cause the death of second-year 

cones. The amount of mortality 

is highly variable but in some 

years a large proportion of cones 

may be attacked.

Cone and Seed Insects

Figure 151. Adult boring hole 

indicating attack on ponderosa 

pine cone by Conophthorus cone 

beetles.

Figure 152. Damage to interior 

ponderosa pine cone caused by larva 

(arrow) of cone beetles.

↓
96

Similar Insects and Diseases: This insect is best 

distinguished from other insects that attack developing cones by the 

presence of the pitch tube on the cone base or stem.

References: 23, 36

Figure 153. Life cycle of cone beetles.

Cone and Seed Insects
97

Cone and Seed Insects

Ponderosa Pine Seedworm

Cydia piperana (Kearfott)

Host: Ponderosa pine

Symptoms/signs: There is 

no external evidence of infestation. 

Inside the cones, frass and mining 

can be seen in the cone axis. Seed 

pairs on the same scales can become 

fused together by the silk lined 

tunnels produced by the larvae. 

Often these seeds tend to stick to the 

scales and remain in the cones.

Adult moths have a 

wingspan of 10 to 20 mm. The 

fore wings are metallic gray with 

silver bands. Larvae are 10 to 15 

mm when mature, white to cream 

colored, with a mottled head 

capsule.

Biology: One generation 

is produced annually. Eggs are laid 

at the base of cone scales, on the 

surface of the scale, or on the cone 

stalk. Newly hatched larvae bore 

between the cone scales, enter a seed, consume it, and leave it filled 

with frass. It then moves on to another seed leaving a silk lined trail. 

As the larva matures, it burrows into the cone axis and overwinters. 

In spring, the insect pupates. Following pupation, the adult emerges.

Effects: In some years this insect can consume a large 

proportion of the seed crop.

Similar Insects and Diseases: A number of insects affect 

cones. This insect is distinguished by the presence of the frass packed 

seeds, larvae or mining in the cone axis.

References: 36

Figure 154. Larvae of 

ponderosa pine seedworm.

Figure 155. Damage of ponderosa 

pine seed by ponderosa pine 

seedworm.
98

Pine Seed Chalcid

Megastigmus albifrons (Walker)

Host: Ponderosa pine

Symptoms/signs: Adults are 

antlike in appearance and range in color 

from yellow to black or brown. Females 

have a long, curved ovipositor. The 

larvae are small, white and legless. The 

outer seedcoat develops normally and 

shows no evidence of an oviposited egg. 

When adults emerge they leave a small 

round hole in the seedcoat.

Biology: Adult emergence 

lasts for about a month in spring. Females may mate or reproduce 

parthenogenetically. Eggs are oviposited through the young scales of 

developing cones directly into the seed. Usually one egg is laid per 

seed. The larva matures in the seed, consuming its entire contents. The 

insect overwinters in the seed and pupates in early spring. Some adults 

emerge at this time while others may diapause for up to 3 years.

Effects: Pine seed chalcid can cause a large percentage of 

cull seed in commercial seed production operations. Since it is very 

difficult to distinguish between healthy and inhabited seed, insects are 

unknowingly transported.

Similar Insects and Diseases: There are a variety of 

cone and seed feeding insects in the West. Larvae of the family 

Cecidomyiidae (Diptera) may cause similar reductions in seed 

production; however, the larvae are not voracious feeders and damage 

to cones and conelets results from gall formation on the seed scale 

which prevents seed dispersal. Other species of insects that feed in 

seeds and cones of ponderosa pine in the Southwest include ponderosa 

pine cone beetle (Conophthorus ponderosae), pine coneworm 

(Dioryctria auranticella), and the ponderosa pine seed moth 

(Laspeyresia piperana).

References: 3, 14

Figure 156. Larva and seed 

damage caused by the pine 

seed chalcid.

Cone and Seed Insects
99

Pine Coneworm

Dioryctria auranticella (Groté)

Host: Ponderosa pine

Symptoms/signs: Entire cones are usually killed by pine 

coneworms; partially killed cones become distorted and do not open. 

Larval feeding cavities inside cones are filled with frass and webbing.

Biology: Larvae begin feeding in ponderosa pine cones in 

late spring. They make an entry hole in the basal portion of the cone 

and consume seeds and scale tissues. Mature larvae pupate in the 

cavities in the cones created by feeding activity of the larvae. Adults 

emerge in middle to late summer.

Effects: This obligate seed and cone insect can be 

destructive when populations are high. Up to 80 percent of cones can 

be damaged per year in the Southwest. Coneworms feed on seeds and 

scales from a cavity inside the cone, severely distorting the cone and 

preventing extraction.

Similar Insects and Diseases: There are a variety of cone 

and seed feeding insects in the West. Other species of insects that feed 

in seeds and cones of ponderosa pine in the Southwest include pine 

seed chalcid (Megastigmus albifrons), ponderosa pine cone beetle 

(Conophthorus 

ponderosae), and the 

ponderosa pine seed 

moth (Laspeyresia 

piperana). This 

conophyte is 

distinguished by 

the entry hole in 

the basal portion of 

the cone and larval 

feeding cavities 

filled with frass and 

webbing.

References: 5, 87

Figure 157. Damage to ponderosa pine cone 

caused by larva of the pine coneworm.

Cone and Seed Insects
100

I

njury to buds and shoots may be caused by caterpillars, 

weevils, bark beetles, midges, aphids, or scale insects. 

Some of these insects also feed on other plant parts such 

as foliage, cones, and branches. By far the most frequently observed 

damage to pine shoots is caused by tip moths and shoot borers 

belonging to the order Lepidoptera (moths and butterflies). 

Shoot insects affect trees by damaging terminal or lateral 

shoots. Such damage typically reduces height growth and deforms 

the tree. Forked branches or multiple leaders often result from a 

previous year’s insect damage. Seedlings and saplings are most 

susceptible to damage by shoot insects. Trees above 2 m in height 

rarely sustain significant injury. Young seedlings are often prevented 

from growing taller than herbaceous competitors, resulting in 

mortality.

Most of these shoot insects are important in young, 

intensively managed stands or replanted forested areas. The 

susceptible stage of hosts is predictable and managers can plan 

accordingly to minimize impacts caused by shoot insects.

References: 23, 40, 43, 108

Bud and Shoot Insects
101

Pine Tip Moths

Rhyacionia spp.

Host: Ponderosa pine

Symptoms/signs: Insect appearance varies between species. 

R. bushnelli adults have a wingspread of 10 to 15 mm; forewings 

are mottled yellowish gray 

and reddish brown. Larvae 

are yellowish with black 

heads, and about 9 to 12 

mm long when mature. R. 

neomexicana adults have a 

wingspan of about 0.24 mm. 

Forewings are irregularly 

banded with transverse bars 

of dark gray, blackish and 

brick-red scales on the inner 

two-thirds of the wing. Larvae 

are usually orange in color 

with dark brown to light tan 

head capsules and are about 

12 to 16 mm long when fully 

developed.

Biology: Larvae 

mine inside new shoots in 

spring and early summer, 

killing them. Both lateral and 

terminal shoots are attacked. 

Larvae initially mine needles 

and then bore into the shoot. 

Pitch tents, frass, and silk 

webbing are all signs of tip 

Bud and Shoot Insects

Figure 158. Adult pine tip moth.

Figure 159. Damage of ponderosa pine 

shoot caused by pine tip moths.
102

moth activity. Once in the shoots, larvae feed between the pith and 

the bark, eventually hollowing out the shoot. 

Effects: Larvae mine in the phloem and xylem of lateral 

and sometimes terminal shoots. Small trees, less than 2 m are most 

susceptible. Shoots are killed by the attacks. Repeated attacks slow 

growth and cause crooks, forks, multiple stems, and spike tops. Tip 

moths rarely kill established trees outright, but attacks can affect 

survival of young planted seedlings.

Similar Insects and Diseases: See western pineshoot borer.

References: 23, 43

Figure 160. Closeup of damaged ponderosa pine shoot 

caused by pine tip moths.

Bud and Shoot Insects
103

Western Pineshoot Borer

Eucosma sonomana (Kearfott)

Host: Ponderosa pine

Symptoms/signs: Adults are moths with coppery-red 

forewings marked with two bright gray transverse bands and a 

wingspread of about 

20 mm. External 

symptoms include 

shortened needles and 

stunted terminal growth. 

Following emergence 

of the larvae, exit holes 

can be found near the 

center of the shoot. 

In the year following 

infestation, a distinct 

swelling can be seen 

around the stem, 

near the exit hole. 

Occasionally terminals 

break off where the 

stem is weakened by the 

exit hole.

Biology: Eggs are laid on elongating shoots in spring. The 

larvae feed in the pith of these shoots, vacate in late spring, and drop 

to the ground to pupate. There they remain dormant through the 

winter and hatch as adults the following spring.

Effects: Larvae mine only in the pith of the shoot. Usually 

shoots remain green for at least a year after attack, however, in some 

cases shoots are killed outright. Most often shoots live, but become 

stunted. Frequently, lateral shoots overtop affected shoots and a 

crook or a fork results. The main result of infestation is reduced 

Figure 161. Damaged (top) and undamaged 

(bottom) shoots of ponderosa pine caused 

by western pine shoot borer larvae. Note 

“bottlebrush” appearance of damaged shoot.

Bud and Shoot Insects
104

Bud and Shoot Insects

Figure 162. Larva of the western pine 

shoot borer. Note that larval feeding is 

restricted to the pith region of the shoots.

height growth, about 25 percent of one year’s vertical growth per 

attack. Depending on management objectives, this may or may not 

be important. The insect occurs at low population levels. 

Similar Insects and Diseases: See pine tip moths.

References: 23, 94, 97
105

Bud and Shoot Insects

Pinyon Pitch Nodule Moth

Petrova arizonensis (Heinrich)

Host: Piñon

Symptoms/Signs: Attacks are 

characterized by fading branch tips and 

small nodules of pitch formed at the 

insects feeding sites. The pitch nodules 

are hollow balls of pitch 13 to 25 mm 

long, round, smooth, and light purple to 

red in color. Pitch nodules usually occur at 

the crotch of two or more twigs.

Biology: Small, rusty-brown 

moths emerge through holes in the pitch 

nodule in late June and early July. Eggs 

are laid on the needle sheaths 

of the current year’s foliage. 

Newly hatched larvae feed on 

the young needles before boring 

into the bark at nodes or whorls 

of twigs or branches. Fullgrown larvae are about 13 mm 

long, reddish-yellow in color 

with a black head and a dark 

area behind the head. Pupation 

occurs inside the pitch nodule 

in June. The pupae move just 

below the pitch surface before 

they emerge as adults.

Effects: Attacked 

twigs and branches are killed. 

Leaders are occasionally 

damaged and forked trees may 

result.

References: 9, 23

Figure 163. Damage caused 

by the pitch nodule moth.

Figure 164. Cocoon of pitch nodule 

moth in damaged ponderosa pine 

shoot.
106

Hosts: Piñon, ponderosa pine, and occasionally Douglas-fir 

and true fir

Symptoms/signs: Pitch moth attacks appear as large, ugly 

masses of pitch that form at the 

wound site. Bark moth attacks 

typically produce less pitch.

Effects: Larger branches, 

limbs, and trunks of young trees 

are attacked. Repeated attacks 

can seriously weaken and kill 

branches. The most severe damage 

is to trees under 6 m, especially in 

urban areas. The insects are rarely 

a problem on larger trees or in the 

forest environment.

Biology: Pitch moths require 2 years for one generation 

to mature, overwintering as larvae each winter. Bark moths require 

only 1 year for a generation to mature, overwintering as eggs or 

larvae. Eggs are laid in bark crevices or near mechanical wounds 

on the bark. Newly hatched larvae tunnel under the bark forming 

irregular galleries or elongated gouges in the 

sapwood. Pitch moth larvae feed on pitch the 

tree produces in response to their tunneling. 

Oozing pitch masses 25 to 75 mm in diameter 

cover entry holes and conceal larvae and their 

destructive tunneling. Full-grown larvae are 

15 to 25 mm long, dirty white, yellow, orange, 

green, or light brown. Bark moth larvae feed 

on the inner bark and when full grown, are 

marked with rows of dark spots.

References: 9

Bark Moths 

Dioryctria spp.

Figure 166. Damage 

caused by pitch moth.

Figure 165. Damage to piñon 

caused by bark moths (Dioryctria) 

at Sunset Crater NP, Arizona.

and Pitch Moth

Synanthedon spp.

Bud and Shoot Insects
107

Juniper Twig Pruner

Styloxus bicolor (Champlain and Knull)

Hosts: 

Juniper and Arizona 

cypress

Symptoms/

signs: The juniper 

twig pruner adult 

is 7 to 11 mm long 

and has a reddishorange head and 

brownish to black 

body. Larvae are 

small, white, and 

cylindrical, legless 

grubs. 

Biology: 

The life cycle may take as long 

as 2 years to complete. Eggs are 

laid on branches, often near an 

intersection of twigs, 0.5 m from 

the branch tip. Grubs kill twigs by 

boring through the centers. 

Effects: Juniper twig 

pruner causes twig dieback on 

junipers and cypress growing 

throughout the Southwest.

Similar Insects and 

Diseases: Cedar bark beetles and 

western cedar borer.

References: 9, 42

Bud and Shoot Insects

Figure 168. Closeup of damage 

to juniper shoots caused by the 

juniper twig pruner.

Figure 169. Exit hole of 

juniper twig pruner.

Figure 167. Damage to junipers caused by the 

juniper twig pruner.
108

Avariety of insects attack trees that are recently dead 

or dying. Losses from these insects are about 1 to 

5 percent of the annual timber harvested. Some of 

these insects have previously been discussed (e.g., woodborers and 

ambrosia beetles) and others are described on the following pages.

Insects of wood products can either attack moist or dry 

seasoned wood. Those that attack moist, seasoned wood are usually 

symbiotically associated with protozoa, fungi, and bacteria that aid 

the insects in the digestion of cellulose and lignin. Some of these 

insects will continue to develop in the wood for several years after 

the wood has been dried and manufactured.

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 6 percent.

References: 14, 23

Insects of Wood Products
109

Carpenter Ants

Camponotus spp.

Hosts: Douglas-fir, pine and true fir

Symptoms/signs: Carpenter ants are large in size, about 5-

15 mm long, and black or black and red in color. They tunnel in the 

wood of stumps, logs, dead standing trees, the interior dead sections 

of livings trees, and the wooden portions of buildings. These 

galleries are honeycomb-like in appearance; the walls are sandpaper 

smooth, free of frass, and run across the grain. The wood borings, 

which are coarse and fibrous, are pushed out of the tunnels and may 

accumulate at the base of inhabited trees. 

Biology: Mating 

occurs during mass flights 

in the spring. The female 

then lays eggs, which take 

approximately 2 months 

to become mature larvae. 

The larvae then pupate in 

cells. Each individual will 

emerge as one of three 

possible castes: winged 

males, winged females, 

or workers. Carpenter 

ants do not eat wood but 

excavate galleries for 

nesting purposes. These 

insects are general feeders, 

and will eat animal food 

(such as caterpillars, meat, 

or refuse) and sweets (from 

aphid honeydew, ripe fruit, 

or sap.)

Insects of Wood Products

Figure 170. Boring at base of ponderosa 

pine caused by carpenter ants.
110

Effects: The excavations in wood can be so extensive that 

the structural integrity of the tree is lost, predisposing the tree to 

wind breakage. 

Similar Insects and Diseases: Horntails or “woodwasps” 

(Siricidae) have similar excavations in host trees. The main 

differences being that they actually have the wood borings pass 

through the digestive tract and are packed in the tunnel behind the 

larva. They usually attack fresh logs or newly dead trees. Adults 

are generally thick-waist, wasp-like insects that are metallic blue or 

black in color. Adults emerge in late spring or summer and lay eggs 

in solid wood (conifers or hardwoods) and the life cycle can range 

from 1 to 2 years. Pupal cells are found in the phloem and the exit 

holes from mature adults are round.

References: 14, 23

Figure 171. Cross section of stump with carpenter ant 

galleries.

Insects of Wood Products
111

Termites

Order Isoptera

Hosts: Most tree species

Symptoms/signs: Termite damage is honeycomb in shape 

and follows the grain of wood. There are three types:

Drywood termites. Coarse sand-like fecal pellets found 

outside of finished wood.

Dampwood termites. Typically colonize dead and down 

trees and untreated wood in contact with the ground.

Subterranean termites. Presence of mud shelter tubes on 

wood, walls and tree trunks.

Biology: Termites are eusocial insects that have well 

developed caste systems. Caste consists of primary reproductives, 

supplementary 

reproductives, 

workers, and 

soldiers. Only the 

reproductives have 

wings and they 

form large flight 

swarms outside 

the colony. As 

their name implies, 

workers perform 

most of the work 

for the colony. 

They are generally 

pale in color, lack 

compound eyes, and have small mandibles. Soldiers are sterile 

adults with greatly enlarged and armored heads and mandibles. 

Their sole duty is defense of the colony against invaders. The 

conversion of cellulose to smaller units by protozoa and bacterial 

organisms in the guts of termites allow them to digest cellulose from 

wood and other plants.

Figure 172. Castes (queen, soldier and worker) of 

termites.

Insects of Wood Products
112

Effects: Termites can be extremely destructive to structures 

built out of wood. Even houses with a cement block foundation 

are at risk because subterranean termite tunnels can cross over the 

cement to wood framing. Damp wood termites attack wood that has 

high moisture content and do not require contact with the ground.

Similar Insects and Diseases: Termites are sometimes 

referred to as “white ants”; however they can be differentiated 

from ants by their soft body, light color, straight beadlike antennae, 

and broad connection between the thorax and abdomen. Ants are 

hard bodied, darker in color, elbowed antennae, and have a narrow 

“waist.” 

References: 14, 23

Figure 173. Damage to sign post caused by termites 

in Oak Creek Canyon, Arizona.

Insects of Wood Products
113

Hardwood Leaf Diseases

Leaf diseases in Arizona and New Mexico are most often 

observed on aspen, Arizona sycamore, cottonwood and willow. 

Although clonal susceptibility to foliage pathogens is common for 

aspen and willow; whole areas can become infected during favorable 

moisture periods. Severe infection can cause premature defoliation 

and reduced tree growth. 

Foliar Diseases

Figure 174. Foliar diseases of aspen occur with adequate 

spring moisture.
114

Black Leaf Spot

Marssonina populi (Lib.) Magnus

Hosts: Aspen and cottonwood

Symptoms/signs: Small brownish spots appear on infected 

leaves in late July and early August. The spots later enlarge and turn 

blackish, are of various sizes and irregular in outline, and have a 

yellowish to golden border. Infected leaves are often smaller than 

normal and fall prematurely.

Biology: Primary infection occurs soon after leaves emerge 

in spring, from spores produced on twig lesions or from infected 

fallen leaves. Additional spores are produced on newly infected 

leaves, which initiates the repeating cycle of disease that continues 

with wet weather until leaves fall. Symptoms intensify and seem to 

ascend trees as the season advances. Marssonina populi survives the 

winter as tiny stromata in fallen leaves and twig lesions. 

Effects: Black leaf spot is the most common leaf disease 

of aspen in the West. Severe outbreaks may cause foliar browning 

in midsummer and nearly complete defoliation by early August. 

Regrowth follows in late summer and early autumn, and twig 

dieback may follow in winter because late season shoots lack normal 

cold hardiness. Defoliated trees produce less wood for 1 or more 

years following an outbreak.

Similar Insects and 

Diseases: Several agents can 

cause premature defoliation of 

aspen including aspen tortrix, 

western tent caterpillar, 

melampsora rust, frost, and 

drought. The irregular brown 

to black blotches on leaves 

distinguish black leaf spot 

from the other agents.

References: 38, 92

Figure 175. Black leaf spot of aspen 

caused by Marssonina populi. 

Foliar Diseases
115

Ink Spot Leaf Blight

Ciborinia whetzelii (Seaver) Seaver

Hosts: Aspen and cottonwood 

Symptoms/signs: Ciborinia whetzelii forms brown to black 

spots, or stromata, in blighted leaves. Infected leaves turn brown and 

the ink spots, or sclerotia, begin to drop out leaving a circular hole in 

the dead leaves.

Biology: Ciborinia whetzelii infects young leaves in 

the spring by ascospores produced on fruiting structures that 

overwintered on fallen leaves. Infected leaves begin to die 

midsummer, but defoliation may not take place until autumn.

Effects: Ink spot leaf blight is more severe on smaller aspen 

trees and in the lower crowns 

of larger trees. As with many 

aspen diseases, some clones 

appear to be more susceptible 

than others. 

Similar Insects and 

Diseases: This fungus may 

be confused with Marssonina 

populi; however, C. whetzelii

produces well-defined circular 

and slightly raised fruiting 

structures, while those of M. 

populi are irregularly shaped 

and flattened.

Reference: 38

Foliar Diseases

Figure 176. Black Ciborinia whetzelii

fruiting bodies. 
116

Melampsora Rust

Melampsora spp.

Hosts: Aspen, Douglas-fir, willow, and cottonwood

Symptoms/signs: Powdery yellow to yellow-orange spores 

produced on both sides of leaves or needles.

Biology: The life cycle of many rust fungi are very 

complex. In the early spring, infected dead aspen leaves on the 

ground release basidiospores that can only infect Douglas-fir. A 

different spore produced on Douglas-fir is wind disseminated and 

infects aspen leaves in 

the summer. Yet another 

spore, the golden-yellow 

uridiniospore, appears on 

both sides of infected aspen 

leaves within 2 weeks. 

This is called the repeating 

stage because these spores 

germinate to reinfect 

aspen leaves throughout 

the growing season. An 

overwintering spore is 

produced on the underside of 

infected leaves in late fall. 

Effects: During wet summers this fungus can cause the 

leaves of highly susceptible clones to shrivel and drop prematurely, 

reducing growth. 

Similar Insects and Diseases: Willows are host of several 

species of Melampsora, each which has a different alternate host. 

These species cannot be differentiated morphologically on the 

willow. 

References: 38, 92

Figure 177. Rust pustules of Melampsora 

sp. on aspen leaves. 

Foliar Diseases
117

Foliar Diseases

Shepherd’s Crook

Venturia spp.

Host: Aspen

Symptoms/signs: Curling, blackening and dieback of the 

tips of terminal and lateral shoots on young aspen sprouts.

Biology: Primary infections by Venturia spp. occur in spring 

on leaf blades or petioles and on young stem tissue. Dark brown to 

black lesions expand rapidly, causing leaves and shoots to droop, 

whither, and become brittle. Secondary infections, promoted by wet 

weather, are initiated throughout the period of shoot elongation by 

conidia from newly blighted shoots. New shoots frequently grow 

adjacent to blighted ones and are blighted in turn. Lesions do not 

extend into woody twigs. 

Effects: In wet seasons, Venturia spp. can kill virtually all 

terminal shoots in susceptible aspen stands that are regenerating by 

sprouting. This damage reduces height growth and deforms trees 

by causing a bend in the stem at 

the point where a lateral shoot 

became a new leader following 

death of the terminal shoot. 

Successive leaders may be killed 

during seasons of severe disease. 

Plants less than 3 meters tall 

are at greatest risk, and damage 

becomes negligible as trees attain 

heights greater than 5 meters. 

Similar Insects and 

Diseases: This is the only fungus 

on aspen causing black lesions 

on leaves, petioles and stems, 

which curl and form characteristic 

shepherd’s crooks.

References: 38, 92

Figure 178. Curling and 

blackening of aspen shoots from 

Shepherd’s crook. 
118

Sycamore Anthracnose

Apiognomonia veneta (Sacc. & Speg.) Höhn

Hosts: Arizona 

sycamore

Symptoms/signs: 

Sycamore anthracnose 

has a range of symptoms 

corresponding to the three 

phases of this disease. The 

symptoms include: cankers on 

buds and twigs; shoot blight 

following a period of cold 

spring weather; and leaf blight 

from direct infection of leaves. 

Foliar lesions characteristically 

extend along the veins and involve interveinal tissue. Sometimes 

large irregular marginal lesions develop.

Biology: Apiognomonia veneta enters twigs via petioles 

during the growing season and remain quiescent until host dormancy, 

when it colonizes and kills bark and cambium. In the early spring, 

spores produced in these cankers 

infect new shoots and leaves. 

Shoot blight, the second phase 

of the disease, involves the 

rapid death of expanding shoots 

and leaves. This phase tends 

to develop suddenly during a 

period of cold spring weather. 

The third and final phase of 

sycamore anthracnose is leaf 

blight, which results from direct 

infection of leaves. It starts out 

most severe on low branches, 

Figure 179. Leaf blight caused by 

sycamore anthracnose. 

Figure 180. Chronic infection by 

sycamore anthracnose results in 

repeated dieback of shoots. 

Foliar Diseases
119

Foliar Diseases

and intensifies and spreads upward during wet seasons, causing 

premature leaf drop. Leaves are most susceptible during the first few 

weeks of growth. Hyphae of the fungus often grow down petioles 

into the twigs, setting the stage for the next year’s damage.

Effects: Repeated twig dieback alters the form of sycamores 

in two ways. First, when the terminal twig on a branch is killed and 

a lateral takes over as the new leader. Since infection takes place 

repeatedly during the 

life of a susceptible tree, 

the branch axis changes 

direction again and again, 

and crooked branches 

result. The second altered 

form is the development of 

a cluster of twigs around a 

common point on a branch 

because of the repeated 

killing of terminals. 

Similar Insects 

and Diseases: Sycamore 

anthracnose may 

occasionally be confused with 

injury by late spring frost. 

However, frost damage may 

affect several species in the same 

area and Apiognomonia veneta 

affects only sycamore.

References: 92

Figure 181. Severe defoliation by 

sycamore anthracnose.

Figure 182. Infected trees refoliate 

but branch dieback is evident.
120

Conifer Needle Diseases

Although occasional outbreaks appear quite dramatic, 

long-term damage from conifer needle diseases in the Southwestern 

Region is usually minor. Sporulation, spread, and infection by these 

fungi are frequently restricted to a specific season, depending on the 

pathogen, and successful infection depends on favorable weather 

conditions. Needle diseases are often associated with plantations, 

such as Christmas tree plantations, where genetic variability to 

resistance is limited. 

Figure 183. Conifer needle diseases are 

most noticeable before bud break.

Foliar Diseases
121

Foliar Diseases

Lophodermella Needle Cast

Lophodermella cerina (Darker) Darker

Host: Ponderosa pine

Symptoms/Signs: Lophodermella cerina infects the needles 

of seedlings, saplings, and the lower crown of larger trees. Current 

year needles are infected and turn brown and die by early summer 

of the following year. Following bud break, green current year 

needles and brown previous year needles give the tree a distinctive 

appearance. The brown needles are “cast” prematurely compared to 

normal needle drop. Successive years of infection occur only with 

favorable weather conditions and results in thin crowned trees. 

Biology: Fruiting bodies are short, oval, light brown, and 

easily overlooked. The spores mature after the needles have been 

cast. They infect new needles shortly after bud break. Spores 

germinate and infect needles directly through the epidermis. Infected 

needles extend normally and are usually killed by the fungus before 

the next year’s needles emerge.

Effects: Although rare, growth loss is the primary longterm effect of needle cast. Successive years of infection are usually 

the result 

of repeated 

abnormally 

high rainfall 

in spring 

and early 

summer. 

Figure 184. Lophodermella needle cast on 1-year needles 

before bud break.
122

Though trees can be killed if infection is repeated for several years in 

a row, they are more often predisposed to other pests.

Similar Insects and Diseases: From a distance, trees with 

needle cast symptoms may be mistaken for those affected by winter 

damage, salt damage, or needle miners. On close inspection, needle 

cast needles are completely brown with dark fruiting bodies present. 

Winter damage, salt damage, and needle miner needles often have 

brown needle tips with green bases.

References: 71, 82, 92

Figure 185. Diseased 1-year needles are cast in late 

summer leaving current year and 2-year+ needles. 

Foliar Diseases
123

Foliar Diseases

Elytroderma Needle Cast

Elytroderma deformans (Weir) Darker

Hosts: Ponderosa pine and piñon

Symptoms/Signs: Needles begin to fade in the fall of 

the year of infection, and by late winter are lighter in color than 

uninfected needles. By spring, the infected needles turn straw color 

as the new needles break bud. The fruiting bodies are elongated 

(average 10 mm in length) and black when visible on dead needles. 

Distinctive “witches’ brooms” are formed by the sprouting of 

epicormic buds. Resin cysts can be found in infected twigs.

Biology: Spores initially infect new needles through the 

epidermis following bud break, but infection can continue into the 

fall until temperatures are too low for spore germination and growth. 

There are two types of spores: one spore is spread by water and the 

other is spread by wind. Discharge of spores occurs during and after 

a rainstorm, when 

new needles are 

probably most 

susceptible to 

infection. The 

fungus spreads 

throughout the 

needles and into 

twigs before the 

needles are killed. 

When twigs 

become infected, 

the fungus can 

perennially infect 

needles on the 

same twigs. 

Conditions 

conducive to 

needle infection by spores only have to occur once, after which the 

disease can progress within the infected tree. 

Figure 186. Witches’ broom formed from Elytroderma 

infection. 
124

Effects: Although elytroderma needle cast is known as 

an occasional disease of ponderosa pine in the Southwest, it is 

common in some areas. In mature trees, if less than one-fourth of 

the branches are infected there is little or no effect on the tree, but 

if more branches are infected, needle cast alone can kill a tree or 

predispose it to attack by bark beetles. 

Similar Insects and Diseases: The witches’ brooms 

produced by elytroderma needle cast are similar to those caused by 

dwarf mistletoe, however, the existence of dead second year needles 

are indicative of needle cast and not dwarf mistletoe infection. 

Elytroderma is the only needle cast that is perennial.

References: 11, 82, 83, 92

Figure 187. Cambium of infected branch has pockets of 

dark resin. 

Foliar Diseases
125

Red Band Needle Blight

Mycosphaerella pini Rostr. in Munk

(Scirrhia pini Funk & A.K. Parker)

Dothistroma septospora (Doroguine) Morelet

(D. pini Hulbary)

Hosts: Ponderosa pine and piñon

Symptoms/Signs: Symptoms first appear as yellow or tan 

bands around the needles, which later turn red. Infection of current 

and second year needles is usually in the lower crown of sapling size 

trees. Seedlings and large trees are rarely infected. Newly infected 

needles have green bands that turn red or brown in late summer. 

These needles die from the tips back. Infected second and older year 

needles can be cast the same year they become infected.

Biology: Needles are infected during rainy periods by rainsplashed spores. The number of infection cycles depends on the 

climate. During wet years, several cycles of infection can occur. 

The Dothistroma septospora stage is the asexual, imperfect stage, 

and the one most commonly found.

Effects: Dothistroma 

needle cast has been observed on 

ponderosa, piñon, and Austrian pine 

in New Mexico. It is most often 

associated with offsite planting. 

Several years of severe infection 

results in reduced growth and death 

of infected trees. 

Similar Insects and 

Diseases: Infected trees can look 

like the lower crown was sprayed 

with herbicides. The death of 

needles from the tips to fascicle is 

similar to the affects caused by high 

concentrations of de-icing salts. 

References: 77, 82, 92

Figure 188. Dothistroma blight 

of Austrian pine.

Foliar Diseases
126

Rhabdocline Needle Cast

Rhabdocline spp.

Host: Douglas-fir

Symptoms/signs: Tiny chlorotic spots on one or both 

surfaces of first year and occasionally older needles arise in late 

summer or early autumn. These lesions enlarge and darken to 

purplish brown spots and bands that are conspicuous by late autumn 

to early spring. Numerous lesions coalesce and involve the entire 

needle except for a short basal portion. Discolored foliage is most 

conspicuous the following spring.

Biology: Rhabdocline species produce apothecia May 

through June in needles still attached to the twigs. The apothecia 

appear as swellings up to several millimeters long and open by 

splitting the needle surface, usually near the midrib. Ascospores 

are airborne and penetrate developing needles directly through 

the cuticle. Only one infection period occurs per year, but it may 

Figure 189. Rhabdocline needle cast lesions on 1-year 

Douglas-fir needles.

Foliar Diseases
127

Foliar Diseases

last several weeks. Needle colonization increases during the fall 

as symptoms become apparent. Infected needles drop during the 

winter, making missing foliage the only noticeable sign of disease.

Effects: This is the most important needle disease of 

Douglas-fir. Damage can be severe in Christmas tree plantations 

and ornamental nursery stock. Seedlings infected in nurseries can 

become foci of subsequent damage in plantations. Occasional 

outbreaks in forest stands can appear spectacular, but trees usually 

recover.

Similar Insects and Diseases: The fruiting body of 

Rhabdocline may be confused with secondary fungi.

References: 82, 92

Figure 190. Needle cast due to rhabdocline needle cast. 
128

True Fir Needle Cast

Lirula abietis-concoloris (Mayor ex Dearn.) Darker

Host: White fir

Symptoms/signs: Dark brown or black elongate fruiting 

bodies are found on second year needles. The fruiting bodies extend 

down the center of the lower needle surface for almost the full 

length. 

Biology: Infection begins on young, developing needles 

during periods of rainfall. Fruiting structures mature on these 

needles the following spring and needles turn brown.

Effects: Lirula abietis-concoloris occurs sporadically and 

infects only newly emerged needles. Damage is rare since it takes 

several years of favorable weather for repeated infection to defoliate 

trees and affect growth and vigor.

Similar Insects and Diseases: None.

References: 82, 92

Figure 191. Death of 2-year needles caused by true fir needle 

cast.

Foliar Diseases
129

Foliar Diseases

White Pine Needle Cast

Lophodermella arcuata (Darker) Darker

(Hyphodermella arcuata Darker)

Host: Southwestern white pine

Symptoms/signs: This fungus is identified by the dark 

brown to concolorous, elongate to elliptical, fruiting structures, 

which develop on previous 

year’s dead and dying 

needles.

Biology: Fruiting 

bodies in dead, second year 

needles open by means of a 

longitudinal fissure during 

warm wet weather and release 

colorless spores that have 

sticky, gelatinous sheaths. 

Airborne spores settle and 

penetrate young, developing 

needles. The following 

spring, diseased needles turn 

reddish brown and by July, 

they are straw colored. 

Effects: Lophodermella 

arcuata infects only the current year’s 

needles, and a single attack results in 

only partial defoliation of the host. 

Repeated consecutive infections are 

rare, but can lead to reduced tree 

growth and vigor.

Similar Insects and 

Diseases: This is the only known 

needle cast disease of white pine in 

the Southwest. 

References: 82, 92

Figure 192. Lophodermella arcuata 

cause browning of 2-year needles. 

Figure 193. Black fruiting 

bodies of Lophodermella 

arcuata. 
130

Pinyon Needle Rust

Coleosporium ribicola Arthur (C. jonesii (Peck) Arth.)

Hosts: Piñon; currants and gooseberries (Ribes spp.) are 

alternate hosts. 

Symptoms/Signs: White columnar sacs (aecia) filled with 

orange spores occur on all surfaces of piñon needles in the spring. 

On ribes, uredinia appear as small, round, golden yellow pustules 

during the summer. Telia, which are waxy and darker orange, 

develop in late 

summer on the same 

ribes leaves. 

Biology: 

Piñon needle rust 

must go through five 

spore stages on two 

different hosts to 

complete its one year 

life cycle. Spores 

from ribes leaves 

infect pine needles in 

late summer to early 

fall, where the fungus 

overwinters. Orange 

droplets form on infected needles in early spring and bright orange 

aeciospores by late spring. The latter are wind disseminated and 

infect newly emerged ribes leaves. Urediniospores develop on the 

ribes and multiply during wet periods. Telia develop in late summer 

followed by the final spore stage which infects pine needles. 

Effects: Affected needles drop prematurely. This disease 

is encountered infrequently on piñon, but is very common on Ribes

spp. 

Figure 194. Aecia of Coleosporium ribicola on 

piñon.

Foliar Diseases
131

Similar Diseases: Coleosporium ribicola on ribes can be 

mistaken for other rusts of ribes, such as white pine blister rust, 

Cronartium ribicola. There is another needle rust of piñon in the 

region, Coleosporium crowellii, which is microcyclic, meaning there 

is no alternate host. The fruiting structures are more reddish-orange 

and waxy rather than powdery as in Coleosporium ribicola. 

Reference: 106

Figure 195. Uredinia and telia of Coleosporium 

ribicola on ribes.

Foliar Diseases
132

Decay of wood is caused by fungi that utilize the 

cell wall components of xylem as a source of 

nutrition. These fungi have both beneficial and 

damaging influences on forest stands. In living trees, decay fungi 

break down tissues in branches, roots, and stems of trees. They play 

an irreplaceable role in the earth’s carbon cycle by returning to the 

atmosphere billions of tons of carbon each year and provide valuable 

habitat for many species of wildlife. Although vital to ecosystem 

functioning, decay can render trees useless for wood products and 

create hazard trees in recreation sites. 

Many decay fungi discussed here decay the heartwood of 

living trees, others decay the wood of dead trees, and some grow on 

both live and dead trees. Most decay fungi do not interfere with the 

Stem Decays and Stains

Figure 196. Evidence of decay is marked by fungal conks 

or cavity nesting holes.
133

normal growth of live trees since they stay in the heart or xylem 

wood of the host. However, they can affect tree structure and 

contribute to wind breakage and windthrow as decay progresses. 

There are some decay fungi that cause mortality. These fungi begin 

decaying the host as a heart rot and later move into the sapwood and 

cambium, which cuts off the flow of water and nutrients, girdling the 

tree. Other fungi decay the wood of dead trees and can also decay 

dead sections of live trees, such as a dead top or old wound on the 

bole.

Decay levels in live trees are highly correlated with age. For 

example, high amounts of decay are typically found in sites where 

conifer trees are 150+ years old. Susceptibility to stem decay fungi 

varies with tree species. Some hardwoods—like cottonwood and 

aspen—are the most susceptible to stem decay in the Southwest, and 

Douglas-fir, white fir and spruce are in general more susceptible than 

ponderosa or southwestern white pine. However, susceptibility is 

also dependent on site quality and host genetics; silviculturists have 

observed some 70-year-old ponderosa pine sites with high levels of 

decay. 

Stem Decays and Stains
134

Red Ring Rot

Phellinus pini (Thore.:Fr.) A. Ames

Hosts: Spruce, true fir, Douglas-fir, pine

Symptoms/signs: Phellinus pini produces swollen knots 

where branches were previously shed, irregular bulges with exuding 

resin, and resin flow from knots. It also produces brown fruiting 

bodies at branch bases, branch stubs, knots, wounds, and cracks. 

These fruiting bodies, or conks, are bracket-like with a brownishblack upper surface, concentric furrowed rings and a brown 

undersurface with spores. Punk knots are common in Douglas-fir, 

western larch, pines, and some spruces. A punk knot is a mass of 

tightly packed sterile brown hyphae that extends from a decayed 

branch stub within the trunk to a local swelling on the surface.

Biology: Decay often begins near the junction of heartwood 

and sapwood and may extend into sapwood adjacent to wounds. The 

decay is often confined to the heartwood of mature trees, either in 

one central column or in several discrete columns that extend from 

branch stubs. 

Stem Decays and Stains

Figure 197. Phellinus pini on Engelman spruce. 
135

Stem Decays and Stains

Effects: Phellinus pini is thought to be the most common 

trunk decay fungus of conifers in North America. Decay columns 

commonly extend 10 meters or more, rendering entire trunks useless 

for lumber. Decay is much more extensive in old trees in virgin 

and unmanaged forests than it is in managed forests where trees are 

harvested at relatively young ages.

References: 27, 30, 92

Figure 198. Red ring rot on Douglas-fir.
136

Red Rot

Dichomitus squalens (Karst.) Reid.

(Polyporus anceps Pk.)

Hosts: Ponderosa pine and piñon 

Symptoms/signs: Dichomitus squalens produces a flat 

fruiting body on the underside of dead branches or stems with intact 

bark. The pore surface is white when fresh and ages to yellow. The 

red rot fungus causes a 

white pocket rot. Like 

other wood decays, it 

has two distinct stages: 

incipient and advanced.

The incipient 

stage is characterized 

by a reddish-brown 

discoloration of 

the affected wood, 

unaccompanied by any 

obvious changes in 

structure or strength. 

The advanced stage 

is characterized by 

small, often poorly defined, white pockets in the discolored wood, 

accompanied by progressive changes in structure and reduction 

in strength. As decay progresses, the pockets become more and 

more numerous until they merge and give the affected wood the 

appearance of a fibrous white mass. Eventually, the white lint-like 

material disappears, leaving the bleached, grayish-brown, decayed 

wood in either a stringy or a somewhat amorphous condition.

Both stages of red rot are usually visible in a board sawed 

from a decayed log. At the point where rot started in the trunk 

heartwood, advanced decay often forms a cavity. Extending in both 

directions from this point are more or less continuous columns of 

advanced decay, bordered by incipient decay. 

Figure 199. Red rot fruiting body on the 

underside of a dead ponderosa pine branch.

Stem Decays and Stains
137

Biology: The spores are dispersed by wind, land in cracked 

bark crevices of dead branches, and germinate to colonize the area 

between the bark and wood and eventually the dead wood, provided 

it has intact bark. The red rot fungus fruits abundantly on the lower 

side of decaying dead material in close contact with the ground. The 

flat, white fruiting bodies appear about 4 years after infection and 

then develop annually during the rainy season for about 6 years. 

Effects: Dichomitus 

squalens is the most 

common decay of ponderosa 

pine in the Southwest. It 

is a decayer of slash (a 

saprophyte) as well as a 

heartrot in live trees. It has 

been reported to cause a 

significant amount of cull 

in live trees 150+-years-old 

when grown for timber. As 

with other decay fungi, D. 

squalens provides habitat 

for cavity nesting birds and 

other wildlife. Although 

this fungus is of minor 

occurrence on living trees in 

second growth forests, there 

are reports of extensive decay of young trees (<80 years) in localized 

areas.

Similar Insects and Diseases: Many fungi decay ponderosa 

pine slash, but D. squalens is probably the most common.

References: 27, 29, 51, 92

Stem Decays and Stains

Figure 200. Red rot decay is typically 

associated with old growth ponderosa 

pine.
138

Indian Paint Fungus

Echinodontium tinctorium (Ell. & Ev.) Ell. & Ev.

Hosts: True fir, and occasionally Douglas-fir and spruce

Symptoms/signs: Echinodontium tinctorium produces 

woody, perennial hoof-shaped conks, 4-20 cm in diameter, usually at 

the undersides of branch stubs. These fruiting structures sometimes 

form at wounds or on limbs. The upper surface is dark gray-toblack, rough and cracked. The lower surface is gray-brown to black, 

composed of thick, blunt, tooth-like spines. The interior tissue is 

brick red to rust red, from a pigment that extends into the adjacent 

decayed wood. The common name for Echinodontium tinctorium, 

“Indian paint fungus,” is derived from the Native American’s use of 

conks in the preparation of red paint pigments. 

Biology: The spores of Echinodontium tinctorium are 

dispersed during cool, wet weather in the fall. They remain 

viable during winter, germinating best after a period of freezing 

temperatures. The fungus enters branchlets between 0.5 mm to 1.5 

mm in size 

and spreads 

through the 

pith to the 

main branch. 

Here the 

fungus can 

remain in 

a dormant 

condition 

for 20, 50, 

or even 100 

years. When 

the main 

branch dies 

or breaks off, 

Figure 201. Echinodontium tinctorium conk showing 

orange inner-tissue. 

Stem Decays and Stains
139

the fungus becomes active again, and decay of the heartwood portion 

of the main branch begins, eventually spreading to the main stem of 

the tree. 

Effects: This fungus is the main cause of heart rot and 

volume loss in mature true firs. Conks are reliable indicators of 

defect and are associated with substantial volumes of decay. One 

fruiting body usually indicates that the entire cross section of the log 

is decayed for a distance of 2 m above and 2.5 m below the conk. 

Decay may also be present in trees that do not bear sporophores. 

The rot is most common in the mid-trunk but may also extend into 

the butt or down from the top. In very late stages of decay, the trunk 

may become completely hollow. Infected trees that break or are 

windthrown are important sources of hollow logs for wildlife habitat 

and act as nurse logs for regeneration. 

Similar Insects and Diseases: Advanced stages of decay 

closely resemble equivalent stages of rot associated with Stereum 

sanguinolentum. However, S. sanguinolentum fruiting bodies are 

completely different, as they form thin, crust-like layers with a grey 

to light brown gilled lower surface that turns blood red when bruised.

References: 21, 29, 92, 100

Stem Decays and Stains
140

Red Belt Fungus

Fomitopsis pinicola (Swartz:Fr.) Karst.

(Polyporus pinicola Swartz:Fr.)

Hosts: Many conifers and aspen

Symptoms/signs: F. pinicola forms perennial conks that are 

corky and shelflike. Its characteristic feature is a red-brown band 

near the white to cream colored edge. These fruiting bodies form 

on dead trees and logging slash and not on infected living trees. 

The decay is a brown cubical rot with shrinkage cracks in which 

prominent white sheets of mycelium develop.

Biology: This fungus enters living trees with airborne spores 

colonizing and infecting through wounds and broken tops. It may be 

introduced into dying or dead trees by insects, as it has been isolated 

from Douglas-fir bark beetles captured both in flight and from egg 

galleries.

Effects: F. pinicola is one of the most important brown 

rot pathogens of old-growth western conifers, but it acts slowly 

and is not 

considered a 

major decay 

pathogen 

of secondgrowth 

forests. 

However, it is 

an important 

component 

Figure 202. Fomitopsis pinicola on dead Douglas-fir.

Stem Decays and Stains
141

of the coniferous forest ecosystem because it decays dead trees and 

logging slash and leaves a lignin-rich residue that is very stable and 

is a major component of the organic matter on the forest floor and 

in the upper layers of soil. This residue enhances water holding and 

cation exchange capacities of soil and is a favorable habitat for the 

development of ectomycorrhizae and for nitrogen-fixing bacteria. 

Similar Insects and Diseases: Brown rot caused by F. 

pinicola is difficult to distinguish from that caused by Phaeolus 

schweinitizii, a butt rot of Douglas-fir. Since P. schweinitzii is a 

root and butt rot pathogen, it is found in the lower 3 meters of the 

trunk and in the roots, and it fruits from the roots out through the 

soil of live trees. F. pinicola only fruits on dead wood material so is 

frequently observed on stumps.

References: 27, 29, 92

Stem Decays and Stains
142

Pouch Fungus

Cryptoporus volvatus (Peck) Shear

Hosts: Ponderosa pine and other conifers

Symptoms/signs: C. volvatus produces small, creamcolored to tan, leathery fruiting bodies. The most distinguishing 

feature of C. volvatus is that it has a fungus sheath with a single hole 

covering the lower spore-bearing surface. This is not a heart-rot 

fungus, but causes a grayish white rot of the sapwood of recently 

killed trees. 

Biology: 

Insects enter, 

feed, and then exit 

fruiting bodies of 

the pouch fungus, 

carrying spores 

to infect recently 

killed or dying trees. 

Typically, it occurs 

only on dead trees 

and snags within 1 

to 2 years after the 

tree’s death.

Effects: 

Most commonly found on ponderosa pine in the Southwest, but can 

infect other conifers. This is not an aggressive pathogen, but invades 

a tree within the first 2 years of death. This fungus is very common 

in trees killed by bark beetles.

Similar Insects and Diseases: No other conifer pouch 

fungus has been identified.

References: 7, 27, 29

Figure 203. Cryptoporus volvatus on dead 

ponderosa pine. 

Stem Decays and Stains
143

Blue Stain Fungi

Ophiostoma spp.

Ceratocystis spp.

Hosts: Conifers

Symptoms/signs: Blue-green discoloration of sapwood 

(often in wedge shapes) in recently killed trees. Blue stain fungi 

frequently originate from bark beetle galleries.

Biology: Blue stain fungi are carried by bark beetles and 

other wood inhabiting insects and are associated with tree mortality. 

They are mostly blue-staining and primarily from the genera 

Ophiostoma and Ceratocystis. The spores germinate and produce a 

mycelium (thread-like mass) that colonizes the phloem and sapwood, 

eventually blocking the water-conducting columns of the tree. The 

formation of a wedge-shaped stain is due to movement of hyphae 

along the rays from the outside of a log.

Effects: Stain 

fungi often hasten the death 

of trees attacked by bark 

beetles. The stain may result 

in a reduction in the value of 

timber or timber products by 

discoloring sapwood, but does 

not affect wood strength. 

Similar Insects 

and Diseases: Another 

group of sapstaining fungi 

are wind disseminated, of 

various colors (blue, brown, 

or gray) and are from the 

genera Aureobasidium and 

Alternaria. Black stain fungi, which are closely related to blue stain 

fungi, also block water-conducting columns. However, black stain 

fungi spread to healthy trees by root-to-root contact. 

References: 92, 100

Figure 204. Blue stain fungi invade the 

sapwood.

Stem Decays and Stains
144

False Tinder Conk

Phellinus tremulae (Bondartsev) 

Bondartsev & Boresov in Bondartsev

Host: Aspen

Symptoms/signs: P. tremulae produces woody conks on 

aspen trunks, typically at branch stubs or scars. The conks are hoof 

shaped, brown to black, with a 

rough, cracked upper surface 

and tan to white pore surface. 

The conks are usually attached 

to the host by a granular core 

of tissue that continues into 

the decayed branch within 

the trunk. P. tremulae also 

produces hard, blackish sterile 

masses of mycelium (sterile 

conks) at branch scars, hence 

the name. The yellowish white 

spongy decay caused by this 

fungus is usually confined to a 

central core.

Biology: Airborne 

spores of P. tremulae infect 

fresh branch stubs or wounds. 

The fungus decays the dead 

or injured area and then gains 

entry to the heartwood. 

Effects: P. tremulae

is the most common cause of aspen stem decay in the Southwest. It 

causes less mortality than aspen canker fungi or ganoderma root rot 

but can create hazard trees in recreation sites.

Similar Insects and Diseases: No other fungi with the 

characteristics of the fruiting body are found in aspen.

References: 30, 38, 92

Figure 205. Phellinus tremullae conk 

on aspen. 

Stem Decays and Stains
145

Heart Rots of Oak

Inonotus dryophilus (Berk.) Murr.

Phellinus everhartii (Ell. & Gall.) A. Ames.

Hosts: Oaks

Symptoms/signs: Oaks are host to many heartwood decay 

fungi. Two of the most common are I. dryophilus and P. everhartii. 

The former produces an annual fruiting body that degrades quickly 

following spore dispersal, while the latter produces a perennial 

fruiting body (conk) that 

grows a fresh sporulation 

layer every year. 

Biology: As with 

most decay fungi, branch 

stubs are the most common 

sites of infection, but entry 

also occurs through trunk 

injuries. Both fungi produce 

fruiting bodies on living trees. 

Effects: Both 

fungi are capable of causing 

extensive heartwood decay. 

Similar Insects 

and Diseases: There are 

many other fungi that 

decay the heartwood of 

living oak trees, but these 

are the most common.

References: 29, 

92

Stem Decays and Stains

Figure 206. Inonotus dryophilus on 

Emory oak. 

Figure 207. Heart rot, Phellinus everhartii, 

on gambell oak.
146

Canker Rot of Oak

Inonotus andersonii (Ellis & Everh.) Cerny

Hosts: Oaks

Symptoms/signs: 

I. andersonii produces flat, 

bright yellow to yellowbrown fruiting bodies with 

peg-like outgrowths beneath 

the bark or outermost layers 

of wood. These fruiting 

bodies degrade quickly, 

turning dark dull brown to 

black, as if the wood was 

burned. 

Biology: Branch 

stubs are the most common 

sites of infection, but entry 

also occurs through trunk 

injuries. I. andersonii

first invades heartwood 

causing a white rot, and 

then moves outward, killing 

the sapwood and cambium 

(hence the name, canker 

rot). Trees often break at 

these cankers. 

Effects: I. andersonii is a common decay pathogen of oaks 

throughout the United States, but also causes mortality where decay 

continues out into the cambium, girdling infected trees. 

Similar Insects and Diseases: Old fruiting bodies of I. 

andersonii are black and are often mistaken for fire scars.

References: 29, 92

Figure 208. Inonotus andersonii forms 

bright orange fruiting structures beneath 

the bark of infected trees that blacken with 

age. 

Stem Decays and Stains
147

Canker-causing fungi are common on hardwoods, 

especially aspen. Canker fungi are often the 

primary cause of aspen mortality because aspen 

bark is soft living tissue, extremely susceptible to wounding 

and subsequent infection by canker fungi. Disturbances such as 

selective logging, campsite construction, and recreation abuse can 

increase the incidence of canker diseases. Although the majority of 

canker-causing fungi 

described below occur 

on hardwoods, the 

last fungus discussed 

occurs on conifers. 

Canker-causing stem 

rust fungi are discussed 

in another section, 

“Stem and Cone Rusts 

of Pine.”

Cankers

Figure 209. Canker development in aspen 

begins with discoloration of the bark.
148

Black Canker

Ceratocystis fimbriata Ellis & Halst.

Host: Aspen

Symptoms/signs: Cankers are target shaped with concentric 

ridges of dead callus. Older cankers typically have a central area of 

dead wood surrounded by a series of bark calluses. These callused 

areas may be concentric in outline, but usually are irregularly shaped 

and ragged in appearance 

because of the massive callus 

folds and flaring dead bark. 

Bark and exposed wood 

darken, resulting in a black 

canker.

Biology: 

Ceratocystis fimbriata can 

infect through the epidermis 

of leaf blades, petioles, 

and young stems; but trunk 

wounds are considered to 

be the primary places of 

infection. Several species 

of beetles have been found 

to carry the fungus and 

are believed to vector it. 

Infection first appears as 

a circular necrotic area on 

the trunk around a fresh 

wound or branch junction. 

During cambial growth in 

the spring, the tree forms a callus at the margins of the canker, 

which temporarily walls off infection. The fungus invades the new 

cambium and inner bark during the tree’s next dormant season and 

kills a new zone of tissue. This process is repeated each year until 

Figure 210. Callus folds and flaring 

dead bark caused by Ceratocystis 

fimbriata.

Cankers
149

the canker, consisting of successive rings of dead bark and wood, 

is formed. The fruiting structures, perithecia, are formed in the 

spring along the border of 

the canker on tissues dead 

at least a year. Spores ooze 

from the perithecia in sticky 

masses and are often vectored 

to other wounded trees by 

insects. Boring insects are 

often found in cankered areas. 

There appears to be a genetic 

predisposition to infection, as 

some aspen clones are more 

susceptible to infection than 

others.

Effects: C. fimbriata 

seldom kills large trees since 

trees generally grow faster 

in circumference than black 

cankers enlarge. However, it 

is possible for several cankers 

to coalesce and girdle a tree. 

The greatest damage from this 

disease is stem deformation 

and subsequent decay that can 

result in bole breakage.

Similar Insects and Diseases: Sooty bark (E. pruinosa) 

is also black in color but does not form a target canker like 

Ceratocystis.

References: 38, 39, 44, 92

Cankers

Figure 211. Bark and callus removed to 

expose target canker.
150

Sooty Bark Canker

Encoelia pruinosa (Ellis & Everh.) Torkelson & Eckblad

(Cenagium singulare (Rehm) R.W. Davidson & Cash)

Host: Aspen

Symptoms/signs: Young cankers appear as slightly sunken 

areas with near normal bark color. Dead bark eventually falls off and 

reveals the black, sooty and crumbly inner bark diagnostic for this 

canker. Beneath the inner bark is a distinctive, black, feather-like 

pattern on the wood surface. The perennial cankers form a band of 

light gray bark that remains attached at the margin of each annual 

zone of expansion giving the tree a barber pole appearance. Gray to 

black leathery cup-shaped fruiting bodies develop on the inner bark 

along the canker margin. The wood beneath cankers is light gray.

Biology: The 

fungus infects trees through 

wounds and invades the 

inner bark and cambium. 

Cankers develop rapidly, 

extending as much as 1 

m in length and 0.3 m in 

width in a year, however, 

the mean annual extension 

is about 45 cm vertically 

and 16 cm horizontally. 

The cup-shaped fruiting 

bodies—apothecia—

develop on the surface of 

old dead inner bark and 

open when wet. Spores are 

forcibly ejected and wind 

disseminated when moisture 

and temperature conditions 

are favorable. These spores 

can cause new infections.

Figure 212. Barber pole appearance of 

aspen bole infected with Encoelia pruinosa.

Cankers
151

Effects: Encoelia pruinosa is considered the most lethal 

and aggressive pathogen of aspen in the West because it can kill trees 

of all sizes in 

3 to 10 years; 

some mature 

trees have been 

observed to die 

in 4 to 5 years. 

Sooty bark is 

found mainly 

on the larger 

dominant and 

codominant 

trees older 

than 60 years, 

in the middle 

elevational 

limits of aspen. 

Cankers are 

more common 

in stands 

disturbed by 

partial cutting, 

construction, 

camper damage, or animal damage. 

Similar Insects and Diseases: Cryptosphaeria canker can 

also produce dead inner bark with a soot-like appearance. However, 

Cryptosphaeria produces a long lens-shaped, light-colored area, 

which lacks the barber pole design. 

References: 38, 39, 44, 92

Cankers

Figure 213. Cup-shaped fruiting bodies of sooty bark 

canker.
152

Cytospora Canker

Cytospora chrysosperma (Pers.:Fr.) Fr.

Hosts: Aspen, 

cottonwood, alder and other 

riparian species

Symptoms/signs: 

Young cankers on smooth bark 

appear as brownish-yellow 

sunken areas. They are often 

irregular in outline and range 

from diffuse to slightly targetshaped. Later, the bark often 

splits at canker margins, the 

inner bark turns black, and wood 

beneath the canker is stained 

brown and water soaked. Black, 

pimple-like, asexual fruiting 

bodies (pycnidia) develop 

within a few weeks after death 

of the bark. They extrude spores 

in orange-red tendrils in wet 

weather. Later, black, pimple-like sexual fruiting bodies (perithecia) 

originate beneath the bark, which expel white masses of spores 

during wet weather that collect on the surface of the bark.

Biology: The fungus causing cytospora canker exists in 

two stages, a sexual stage known as Valsa sordida, and an imperfect, 

or asexual, stage called Cytospora chrysosperma. The latter is 

more commonly encountered. The fungus is considered a normal 

inhabitant of aspen bark microflora, which readily enters and 

parasitizes bark that has been injured or weakened by any cause. 

Trunk cankers are formed by a gradual killing of the bark in a more 

or less circular area over a period of several years. Annual canker 

growth can be seen by the slight annual callus formation around the 

Figure 214. An expanding cytospora 

canker.

Cankers
153

perimeter of infection. The fungus fruits readily in the dead outer 

bark; even when typical canker symptoms fail to develop. The 

Cytospora stage forms small black fruiting bodies from which sticky 

spores ooze out in long, coiled, orange-to-dark-red masses called 

spore tendrils. The “Valsa” stage appears as flask-shaped perithecia 

formed beneath and in a circle around the old pycnidia. Some 

ascospores are forcibly discharged from the perithecia; others collect 

around the openings of the perithecia in sticky white masses on the 

dead bark. The diseased inner bark remains attached to the tree for 

2 or 3 years before turning lighter brown in color and falling off in 

large pieces. 

Effects: Cytospora chrysosperma is the most common 

fungus found on aspen throughout its range. It is weakly parasitic 

and normally attacks 

stressed trees. 

Cytospora infection is 

associated with frost 

cracks and sunscald, 

elk feeding wounds, 

tree vigor and damage 

by fire. 

Similar 

Insects and Diseases: 

The orange tendrils or 

spore horns distinguish 

this fungus from all of 

the other aspen canker 

causing fungi.

References: 38, 44, 92

Cankers

Figure 215. Cytospora spore tendrils exuding 

from bark of a dead tree.
154

Cryptosphaeria Canker

Cryptosphaeria lignyota (Fr.:Fr.) Auersw.

Host: Aspen

Symptoms/signs: Young infections and canker margins are 

orange to light brown. The cankers are long (3 meters or more) and 

narrow (2-10 centimeters wide), appearing as grayish depressions in 

the bark, with callus ridges forming at the edge. Dead bark adheres 

to the canker face. Inner bark is black and sooty with obvious 

fibers and small, lightcolored flecks (<2 

mm). Light orange, 

tiny asexual fruiting 

bodies may form near 

the edge of the canker. 

Clusters of black, flaskshaped sexual fruiting 

bodies (perithecia) 

develop beneath bark 

dead for more than 1 

year. Cryptosphaeria 

populina also causes 

stain in the sapwood and 

heartwood and causes a 

yellow-brown, mottled 

decay.

Biology: Spores 

of Cryptosphaeria 

populina are released 

during wet weather and 

infect fresh wounds in 

the inner bark and wood. 

The fungus eventually 

colonizes sapwood and 

Figure 216. Cryptosphaeria colonizes 

sapwood and cambium. 

Cankers
155

heartwood, causing discoloration and decay, before penetrating the 

bark and causing a canker. Brown, mottled decay develops in the 

central part of the column of discolored wood. Mortality occurs not 

from bark necrosis as it may seem, but because the pathogen kills a 

large volume of sapwood. 

Effects: Trees up to 15 centimeters d.b.h. may be killed 

within 3 years, with older trees taking longer to girdle. Branch 

cankers are often found on large trees, where they girdle the branch 

and enlarge onto the trunk. The decay associated with the canker 

predisposes infected trees to wind breakage.

Similar Insects and Diseases: Bark that has been dead for 

more than 1 year from C. lignyota is black, stringy, and sooty-like, 

similar to sooty-bark canker (E. pruinosa). However, they are easy 

to distinguish, because of the lenticular-shaped fruiting structures and 

barber pole design of E. pruinosa, both lacking in a Cryptosphaeria 

canker. 

References: 38, 44, 92

Cankers
156

Hypoxylon Canker

Hypoxylon mamatum (Wahlenberg) J.H. Miller

Host: Aspen

Symptoms/signs: Young infections occur as slightly 

sunken, irregular, yellowish-orange areas around wounds or branch 

stubs. The underside of diseased bark appears laminated or mottled 

black and yellowish white. White mycelial fans form under the bark 

and are most evident at the top and bottom edges of the canker. Gray 

fungal pillars (asexual fruiting bodies) form beneath loose, blistered 

bark. Later, patches of gray-black, crust-like mounds form on the 

wood. These mounds contain perithecia, sexual fruiting bodies. 

The papery outer bark sloughs from older infections, exposing a 

blackened, crumbly inner bark. The cortex in the central portion 

of older cankers cracks in a checkerboard fashion, sloughing off in 

small patches. 

Figure 217. A section of a Hypoxylon canker with cracked and 

blistering bark.

Cankers
157

Biology: In the humid Lake States area, the fungus invades 

the sapwood and trees often die before they are completely girdled 

because sapwood decay beneath a trunk canker predisposes the tree 

to wind breakage. In the arid Southwest, however, breakage is not 

common. Cankers on large trees in the Southwest may attain ages 

of 20 to 50 years before tree death. A live 1 m d.b.h. aspen tree in 

Arizona was observed with a Hypoxylon canker extending from the 

ground to a height of about 12 m, only half-girdling the tree. There 

appears to be a genetic predisposition to infection, because some 

clones are more susceptible to infection than others within the same 

geographic area.

Effects: Hypoxylon canker disease is the most important 

canker disease of aspen in the Lake States region, but of minor 

importance in the Southwest. Hypoxylon canker annually kills an 

estimated 1 to 2 percent of the standing aspen volume in the Lake 

States area. While the disease causes serious mortality in localized 

areas in the Southwest, mortality rates have not been determined. 

Similar Insects and Diseases: It is the checkerboard pattern 

of older infections that distinguishes this canker disease from others 

that occur on aspen.

References: 38, 44, 92

Cankers
158

Atropellis Canker

Atropellis piniphila (Weir) Lohman and Cash

Hosts: Southwestern white pine, limber pine and ponderosa 

pine

Symptoms/signs: Cankers appear as elongated depressions 

covered with bark. Atropellis species produce two kinds of fruit 

bodies, one flask-shaped and one cup-shaped, on killed bark. The 

flask-shaped structure develops first. These are black, about 1 mm 

across, and contain multiple chambers where spores form. The cupshaped structures are black with a brown interior, measuring 2-4 mm 

across when moist. They form on cankers 2 or more years old and 

are present year round. Dark brown mycelium permeates the bark 

and wood, creating a zone of bluish black stain that in cross-section 

is initially wedge shaped, pointing toward the center of the stem, 

Figure 218. Fruiting structures on atropellis canker.

Cankers
159

becoming irregular with age. Species are separated based on spore 

morphology.

Biology: Infection begins in a branch axil on stems 5-30 

years old and so there is typically a branch stub in the center of the 

canker. Some cankers start on internodes, reflecting the ability of 

the fungus to infect wounds or bruised bark as well as apparently 

undamaged bark of young stems. 

Effects: Atropellis canker can be found throughout the 

region but its occurrence is infrequent in natural forest settings. 

Although Atropellis rarely kills trees, there are areas where outbreak 

levels are reached and mortality occurs in young trees. It can 

be damaging in Christmas tree plantations where it causes trunk 

deformities and economic loss. 

Similar Insects and Diseases: Atropellis canker may be 

confused with other canker-causing fungi; however, atropellis is the 

only one that stains the wood.

Reference: 100

Cankers
160

There are several species of stem rust fungi on conifers 

in the Southwest. The rust fungi are unique in many 

respects. Some species of rust fungi are autoecious, 

which means they complete their life cycle on one host. Other 

species are heteroecious, which means they complete their life cycles 

on two entirely unrelated hosts. The most important rust species of 

trees are those that invade the main stem and cause mortality. The 

most destructive stem rust listed below is white pine blister rust, a 

nonnative pathogen 

found in New Mexico.

There is one 

species of cone rust 

in the Southwest and 

it infects Chihuahua 

pines in the southeast 

corner of Arizona.

Figure 219. Branch flagging and top-kill are 

common signs of stem rust infection.

Stem and Cone Rusts of Pine
161

White Pine Blister Rust

Cronartium ribicola J.C. Fisch.

Hosts: Southwestern white pine is the only species currently 

affected in the Southwest; limber pine and bristlecone pine are also 

susceptible. Currants and gooseberries (Ribes spp.) are alternate 

hosts. 

Symptoms/Signs: 

Tapered branch swellings or 

stem swellings (on young 

trees) are an early symptom 

on pine. The characteristic 

white blisters (aecia) appear 

on mature cankers in late 

spring. After the blisters 

disintegrate, cankers 

have a dark, roughened 

appearance. Flagging (i.e. recently 

killed branches with red needles) 

occurs several years after initial 

infection. 

Biology: Spores produced on 

Ribes leaves are wind dispersed and 

infect pine needles. The fungus grows 

into the inner bark, forming a canker 

that eventually girdles the branch or 

stem. Blisters erupt through the bark 

of the canker, releasing the spores that 

infect Ribes. 

Stem and Cone Rusts of Pine

Figure 220. Cronartium ribicola spores 

are discharged from sacs or blisters in the 

spring. 

Figure 221. White pine blister 

rust sporulating on the bole of 

an infected tree.
162

Effects: This 

nonnative disease is one 

of the most damaging tree 

diseases in North America. 

Trees of all sizes can be 

affected, although smaller 

trees are killed more rapidly 

than larger trees. 

Blister rust was 

found near Cloudcroft, New 

Mexico in 1990, and is now 

widespread throughout the 

Sacramento and adjoining 

White Mountains. It is most 

common on moist, mixedconifer sites above 2,450 m. 

The disease has also been 

found in the nearby Capitan 

Mountains, on Gallinas Peak 

Figure 222. White pine blister rust 

cankers eventually girdle infected stems 

and branches. 

Figure 223. 

Cronartium ribicola

on ribes. 

Stem and Cone Rusts of Pine
163

(near Corona, NM), and most recently on the Gila National Forest, 5 

km from the Arizona border. However, it has not yet been found in 

northern New Mexico or in Arizona (as of 2005). 

Similar Diseases: Atropellis canker, which is fairly 

common on white pines in the Southwest, forms slight swellings 

with roughened bark. It produces small black fruiting bodies near 

the canker margin. Dwarf mistletoe causes branch swellings that 

can look remarkably 

similar to blister rust 

cankers. Sunscald and 

mechanical injuries can 

superficially resemble 

blister rust damage. 

Ribes leaves are often 

infected by other rusts, 

such as Coleosporium 

ribicola, that can be 

mistaken for white pine 

blister rust. 

References: 

26, 70, 92

Figure 224. Top-kill and flagging on mature 

white pine.

Stem and Cone Rusts of Pine
164

Limb Rust

Cronartium arizonicum Cummins

Host: Ponderosa pine

Symptoms/Signs: Dead and dying branches, often in the 

middle of the crown, are quite characteristic of this disease. Sporeproducing sacs (aecia) are produced on live infected branches, and 

erupt through the bark in spring to midsummer. Trunks are not 

affected by this disease even though the fungus travels through it to 

get to the branches. 

Biology: Initial infection 

occurs on a needle-bearing twig. The 

fungus grows into the sapwood and 

eventually reaches the main stem. It 

grows up and down the stem, entering 

and killing individual branches. 

Figure 225. Live limbs bearing 

Cronartium arizonicum spore 

sacs in the spring/summer die 

in the fall. 

Figure 226. Limb rust infection 

typically starts mid-crown and 

spreads in both directions. 

Stem and Cone Rusts of Pine
165

Disease from this pathogen results in a progressive invasion and 

killing of branches by the fungal mycelium that is perennial in the 

trunk, but does not injure it. From an initially infected branch, the 

parasite grows into the wood of the trunk and advances upward and 

downward up to 18-21 cm per year in each direction and then out 

into branches where it sporulates. Infected branches typically die the 

following year. 

There are at least three varieties of limb rust in the western 

U.S., collectively known as Peridermium filamentosum. Cronartium 

arizonicum, which uses Indian paintbrush (Castilleja spp.) as an 

alternate host, is the most common variety in Arizona and New 

Mexico. Another variety that spreads directly from pine to pine has 

been detected on the Kaibab Plateau in northern Arizona. 

Effects: Although the disease can be very damaging to 

individual trees, its occurrence in an area is usually low. In Arizona, 

it has been observed throughout the ponderosa pine type, from the 

Coronado National Forest to the North Kaibab Ranger District. 

Similar Diseases: Many agents can cause branch mortality, 

but limb rust is distinctive because of the progressive mortality in the 

center of the crown. 

References: 79, 92, 116

Stem and Cone Rusts of Pine
166

Western Gall Rust

Peridermium harknessii J.P. Moore

Endocronartium harknessii (J.P. Moore) Y. Hiratsuka

Host: Ponderosa pine

Symptoms/Signs: This fungus forms round or pear-shaped 

galls on the main stem or branches, which emit orange spores. There 

is a white-spored race in Arizona and New Mexico that sometimes 

develops elongated galls.

Biology: This disease spreads directly from pine to pine. 

Infection occurs on a needle-bearing twig. The fungus stimulates 

the production of 

xylem, forming 

galls, which 

enlarge over the 

years. Spores 

appear on the 

galls in late 

spring. 

Effects: 

This disease 

is probably 

widespread in 

the region, but at 

very low levels. 

Occasionally 

it has been 

destructive to 

seedlings and saplings, following infrequent “wave years” of new 

infection. Gall rust deforms but seldom kills older trees. 

Similar Diseases: Dwarf mistletoe can cause trunk 

swellings (cankers) that are usually much longer than those produced 

by western gall rust. 

References: 92, 116

Figure 227. White-spored gall rust displaying spore 

sacs and swollen branch. 

Stem and Cone Rusts of Pine
167

Comandra Blister Rust

Cronartium comandrae Peck

Hosts: Ponderosa pine and Mondel pine (Pinus eldarica)

Symptoms/Signs: Symptoms of disease on pine begin with 

slight, spindle-shaped swellings that give rise to pustules that soon 

exude a mass of rust colored spores. On the nonnative Mondel/

Eldarica pine, comandra blister rust causes dieback of branches 

and eventual tree death. On ponderosa pine, its native host, this 

disease is rare but occasionally girdles seedlings and saplings. On 

Comandra pallida, the alternate native host, the rust causes pale 

yellow leaf and stem spots and leaf abscission. 

Biology: The aecial stage develops on pine in late spring 

through early summer and spores disseminate by wind at that time. 

These spores are responsible for the primary infection of the alternate 

host, C. pallida. Rain and cool temperatures favor their germination. 

The next spore stage, the so-called repeating stage, occurs and builds 

up on Comandra, as long as there is wet weather. The final stages 

give rise to basidiospores in late summer, which are wind-dispersed 

to infect pine needles. The fungus grows into the inner bark, forming 

a canker that eventually girdles the branch or stem. 

Effects: Although this disease causes major damage to 

lodgepole pine and sometimes ponderosa pine in northern Colorado 

and Wyoming, it is of 

minor consequence to 

ponderosa pine in Arizona 

and New Mexico. 

However, comandra 

blister rust has done 

considerable damage to 

plantings of Mondel pine 

Stem and Cone Rusts of Pine

Figure 228. Comandra pallida with leaf 

infections. 
168

in the Prescott, Sedona and Payson areas of Arizona. Beginning in 

the late 1970s, Mondel pines were planted widely as a landscape tree 

throughout these areas, until it was realized that comandra blister rust 

impacted their survival. Infected Comandra pallida are typically 

observed near infected Mondel pines.

References: 28, 92, 116

Figure 229. Comandra blister rust swollen canker. 

Stem and Cone Rusts of Pine
169

Gymnosporangium Rusts

Gymnosporangium spp.

Hosts: Junipers and Arizona cypress

Symptoms/Signs: There are eight species of 

Gymnosporangium rusts of juniper in the Southwest and one on 

cypress. Most Southwestern Gymnosporangium spp. alternate 

on serviceberry and/or hawthorn (Rosaceae), but one species (G. 

speciosum) alternates on fendlera and mock orange (Hydrangeaceae). 

On the evergreen host tree, these rusts cause witches’ brooms, galls, 

other branch distortions, and dieback of twigs and branches. Brown 

to orange hornlike or cushionlike projections (telia) are produced 

in the spring; these swell and gelatinize during wet periods and are 

quite spectacular. On alternate hosts, the rust develops colorful spots 

and localized swellings on leaves, fruits, and green twigs, followed 

by casting or distortion and death.

Stem and Cone Rusts of Pine

Figure 230. Gymnosporangium speciosum telia on juniper. 
170

Biology: Some Gymnosporangium species complete their 

life cycles in 1 year, but many require 2 years. Two spore stages 

form in spring through late summer on the alternate host. The 

second spore type is wind disseminated and infects juniper or 

cypress (depending on the rust species). Gymnosporangium species 

overwinter in their evergreen hosts, where they produce telia in 

the spring. The telia produce the final spore stage that infects the 

alternate host. Many of these rust species become perennial in 

juniper or cypress and produce telia annually on galls, swellings, or 

witches’ brooms.

Effects: In the Southwest, these fungi generally cause 

minimal damage to junipers, other than some deformities. Impact on 

the foliage and fruits of the alternate hosts may be more significant in 

years with adequate rainfall. 

Similar Diseases: Witches’ brooms caused by some 

of the juniper rusts could be confused with mistletoe infection. 

Gymnosporangium cupressi affects Arizona cypress in central 

Arizona. 

References: 78, 92, 116

Stem and Cone Rusts of Pine
171

Fir Broom Rust

Melampsorella caryophyllacearum J. Schröt

Hosts: White and subalpine fir

Spruce Broom Rust

Chrysomyxa arctostaphyli Dietel

Hosts: Engelmann and blue spruce

Symptoms/Signs: Both of these diseases appear very 

similar on their 

respective hosts. The 

yellow to pale green 

brooms are dense and 

compact. Stem or 

branch swellings may 

also occur near the 

point of infection. 

Biology: 

Windblown spores 

produced on an 

alternate host are 

needed to start 

new infections on 

trees. Chickweeds 

(Cerastium and 

Stellaria spp.) are 

alternate hosts for 

fir broom rust, 

while bearberry 

or kinnikinnick 

Stem and Cone Rusts of Pine

Figure 232. Expanding 

foliage is pale green.

Figure 231. Yellow to pale-green witches’ brooms 

are conspicuous even at the forest level.
172

(Arctostaphylos uvaursi) is the alternate 

host for spruce 

broom rust. Once a 

tree is infected, the 

fungus stimulates 

bud formation, 

leading to broom 

development. The 

brooms shed their 

needles in the winter 

and grow new ones 

in the spring. 

Effects: 

Broom rusts can be 

found throughout 

much of the 

Southwest on their 

respective hosts. 

They typically occur 

at low levels, but are 

abundant in some 

locations. Infection 

typically results in 

deformity, which is 

most significant on 

young trees. Stem 

infections sometimes 

result in topkill and/or 

stem breakage. 

Figure 233. Foliage yellows in late summer.

Figure 234. Needles die and drop, leaving the 

broom devoid of foliage during winter.

Stem and Cone Rusts of Pine
173

Similar 

Diseases: Broom 

rusts are sometimes 

mistaken for dwarf 

mistletoe witches’ 

brooms. However, 

the former are more 

dense and compact, 

and lack mistletoe 

shoots. Dwarf 

mistletoes of true firs 

and spruces have very 

limited distributions 

in the Southwest. 

References: 

92, 116

Stem and Cone Rusts of Pine

Figure 235. Chickweeds are alternate hosts for 

fir broom rust.

Figure 236. Topkill 

caused by spruce 

broom rust.
174

Stem and Cone Rusts of Pine

Figure 237. Infected needles release spores in mid to 

late summer.

Figure 238. Kinnikinnick is the alternate host to spruce 

broom rust.
175

Stem and Cone Rusts of Pine

Southwestern Cone Rust

Cronartium conigenum Hedgc. & N. Hunt

Host: Chihuahua pine and oak

Symptoms/Signs: This disease produces swollen, deformed 

cones on Chihuahua pine that, when ripe, are loaded with orange 

spores beneath a thick papery outer surface. On oak, this disease 

produces several different spore stages. The type most often 

observed has the appearance of brown to black wool on the lower 

leaf surface.

Biology: This fungus 

produces spores on swollen 

deformed cones (galls) of 

Chihuahua pine in July and 

August, and other spores on the 

undersides of leaves of Mexican 

blue, Dunn, Emory, gray, canyon 

live, netleaf, silverleaf and 

Arizona white oaks throughout 

the summer. Cones become 

infected during their first year 

of development, swell into 

misshapen galls of various sizes, 

produce no seeds and do not 

open. Aecia develop 2 to 3 years 

after infection. Galls die after 

aecial production but remain on 

the trees. Large galls usually kill the branches that bear them. 

Effects: During periods of outbreak brought on by favorable 

weather, cone rust may kill more than 50 percent of the cones on 

groups of trees. This disease also affects other pine species in 

Mexico. 

Similar Diseases: None

References: 92, 116

Figure 239. Swollen Chihuahua 

pine cone infected with C. 

conigenum and sporulating. An 

uninfected cone is on the right.
176

Mistletoes are parasitic plants that slowly weaken 

and eventually kill their host trees. There are two 

types of mistletoe in North America, true mistletoe 

(Phoradendron) and dwarf mistletoe (Arceuthobium). Both are 

parasitic on the stems of woody plants from which they derive water 

and mineral nutrients. True mistletoes produce most of their organic 

nutrients by their 

own photosynthesis 

and are believed to 

obtain little from 

the host. Although 

photosynthetic, 

dwarf mistletoes 

are dependent on 

the host for carbon 

nutrients for growth 

and reproduction. 

Dwarf mistletoes are 

generally considered 

to be more damaging 

than true mistletoes; 

however, host 

mortality associated 

with either type of 

mistletoe infection can 

occur during periods 

of drought when lack 

of stomatal closure of 

leaves of the parasite 

causes fatal water loss 

of the host. 

Mistletoes

Figure 240. Male (above) and female (below) 

A. vaginatum subsp. cryptopodum. 
177

Dwarf Mistletoes

Arceuthobium spp.

Dwarf mistletoes are the most common pathogens in 

Southwestern coniferous forests. They are parasitic, seed-bearing 

plants that depend on their hosts almost completely for water 

and nutrients. Dwarf mistletoes are natural components of many 

forest ecosystems in the West, having co-evolved with their hosts 

for hundreds of thousands of years. There are eight species in the 

region, each typically having one preferred host species. 

Ponderosa pine dwarf mistletoe (generally referred to as 

southwestern dwarf mistletoe to distinguish it from a different 

species affecting ponderosa pine in California and the Northwest; it 

has recently been referred to as pineland dwarf mistletoe by some) 

has long been recognized as the most damaging disease of ponderosa 

pine in the Southwest. It occurs in over one-third of the ponderosa 

pine acreage in the region. Douglas-fir dwarf mistletoe occurs in 

roughly one-half of the mixed conifer acreage in the region. Other 

species of dwarf mistletoe have more limited distributions (see 

table).

Hosts: See table

Symptoms/signs: Aerial shoots of dwarf mistletoe plants 

vary by species in size, color, and pattern of branching. For example, 

southwestern dwarf mistletoe of ponderosa pine are often bright 

orange and conspicuous, and those of Douglas-fir dwarf mistletoe are 

often small and inconspicuous. Host branches and stems are often 

swollen at the site of dwarf mistletoe infections. Witches’ brooms 

develop from either systemic infections or as a result of discrete, 

localized infections. The size and extent of brooms varies among 

dwarf mistletoes and their host. 

Biology: Dwarf mistletoes have separate male and female 

plants. Seeds are produced annually on female plants. These are 

explosively released (typically 1 to 12 meters), and stick to host 

material. Upon germination, dwarf mistletoes produce an endophytic 

Mistletoes
178

system, a specialized rootlike structure that is in contact with the 

phloem and xylem of host trees, from which the parasite obtains 

nutrients and water. Aerial shoots appear 3 to 5 or more years after 

infection; the period before 

shoots are visible is known 

as the latent period. 

Spread of dwarf 

mistletoe occurs both from 

tree to tree and within the 

crowns of individual trees. 

Infections tend to build up 

initially in the lower half 

of a crown and gradually 

spread upward. Lateral 

spread of dwarf mistletoe 

through single-storied stands 

averages about 0.5 meter per 

year. Spread is relatively 

rapid from infected overstory 

trees to nearby regeneration. 

Effects: As 

parasites, dwarf mistletoes 

cause significant changes 

in physiological processes 

and structural characteristics 

of infected trees, resulting in changes in the structure and function of 

forest communities. Tree growth and vigor usually decline when more 

than half the crown is parasitized. Most infected trees can survive for 

several decades; generally smaller trees decline and die more quickly 

than larger ones. Tree mortality in areas with extensive infection is 

often three to four times higher than in uninfested areas. Bark beetles 

frequently attack heavily infected trees, especially during drought.

Mistletoes

Figure 241. Male (above) and female 

(below) Douglas-fir dwarf mistletoe.
179

Extensive 

dwarf mistletoe 

infection greatly 

reduces forest 

productivity. On the 

other hand, infection 

has some benefits 

for wildlife. Large 

witches’ brooms can 

serve as ideal nesting 

platforms for birds and 

small mammals, and 

snags create habitat 

for cavity nesting 

birds. A few species 

(most notably the blue 

grouse) are known to 

eat dwarf mistletoe 

shoots, although none 

depend on it as a 

primary food source.

Similar 

Insects and Diseases: 

Some fungi cause the 

formation of witches’ 

brooms: Broom rusts 

in white fir and spruce; Elytroderma needle cast in ponderosa and 

piñon.

Where brooms are observed, branches should be checked for 

the presence of aerial dwarf mistletoe shoots to distinguish broom 

symptoms caused by other pathogens or physiological disorders.

References: 12, 33, 34, 76, 101

Mistletoes

Figure 243. Apache dwarf mistletoe on 

southwestern white pine (above). 

Figure 242. Spruce dwarf mistletoe. 
180

Mistletoes

Figure 245. Large witches’ 

brooms and dying top on 

severely infected ponderosa 

pine. Figure 246. Witches’ brooms on Douglas-fir 

are often utilized by birds and mammals.

Figure 244. 

Female 

pinyon dwarf 

mistletoe with 

mature fruit. 
181

Principal Hosts and Distribution of 

Dwarf Mistletoes in Arizona and New Mexico

Common 

Name Species Principal Host Distribution

Southwestern 

dwarf mistletoe

Arceuthobium 

vaginatum subsp. 

cryptopodum

(Engelmann) 

Hawksworth & 

Weins 

Ponderosa pine Throughout host type

Douglas-fir 

dwarf mistletoe

Arceuthobium 

douglasii

Engelmann

Douglas-fir Throughout host type

Western spruce 

mistletoe

Arceuthobium 

microcarpum

(Engelmann) 

Hawksworth & 

Weins

Engelmann 

spruce, Blue 

spruce, and 

Bristlecone 

pine 

Limited portions of 

host type, although 

common in eastern 

and central Arizona

Pinyon dwarf 

mistletoe

Arceuthobium 

divaricatum

Engelmann

Piñon Throughout the 

Southwest, except 

southeast Arizona

Apache dwarf 

mistletoe

Arceuthobium 

apachecum

Hawksworth & 

Weins

Southwestern 

white pine

Eastern and 

southeastern Arizona, 

central and southern 

New Mexico

True fir dwarf 

mistletoe

Arceuthobium 

abietinum f. 

sp. concoloris

Engelmann ex 

Munz

White fir North rim of Grand 

Canyon National 

Park, Santa Catalina 

and Chiricahua Mts., 

AZ

Chihuahua pine 

dwarf mistletoe

Arceuthobium 

gillii Hawksworth 

& Weins

Chihuahua 

pine

Mostly southeast 

Arizona, but some in 

central

Blumer’s dwarf 

mistletoe

Arceuthobium 

blumeri A. Nelson

Southwestern 

white pine

Huachuca Mts., 

Arizona

Mistletoes
182

Mistletoes

Figure 249. 

Pinyon dwarf 

mistletoe 

witches’ 

broom.

Figure 247. Dwarf 

mistletoe infected 

spruce.

Figure 248. Witches’ 

broom caused by A. 

gillii. 
183

Mistletoes

Figure 252. Southwestern 

dwarf mistletoe plants and 

witches’ broom on ponderosa 

pine.

Figure 250. Dwarf 

mistletoe infected 

piñon pine with 

declining crown.

Figure 251. Dead piñon with signs of 

severe mistletoe infection.
184

Figure 253. Phoradendron 

coryae in December. 

Figure 254. Phoradendron juniperinum 

with pink ripe berries. 

True Mistletoes

Phoradendron spp.

True mistletoes are 

commonly known as the Christmas 

or leafy mistletoes. There are 

eight species in the Southwest, all 

within the genus Phoradendron. 

Three species occur on hardwoods, 

the other five infect conifers. 

Phoradendron macrophyllum has 

a very broad host range, occurring 

on most riparian tree species, while 

the other true mistletoes are genus 

specific. 

Hosts: See table

Symptoms/signs: True 

mistletoes are flowering plants with thick green stems. Plants are 

often round in form and up to 1 meter in diameter, depending on the 

species. Hardwood true mistletoes have thick green leaves that are 

nearly oval in shape, contrasting with conifer true mistletoes, which 

have small thin leaves or are nearly leafless. The small, sticky, 

berries are white, pink or red 

and are ripe from October 

to January, again depending 

on the species. Evergreen 

clumps of mistletoe 

are readily observed on 

deciduous trees in winter 

when leaves are off the trees. 

Biology: Fruiteating birds distribute the 

seeds in their droppings or 

by wiping their beaks. Some 

Mistletoes
185

bird species swallow the fruit 

whole and disperse the seeds 

to another tree, while other 

bird species pick out the seed, 

leaving it on the host plant, 

and swallow only the pulp.

When the seeds 

germinate a modified root 

penetrates the bark of the 

host and forms a connection 

through which water and 

nutrients pass from the host to the mistletoe. It takes approximately 

2 to 3 years for shoots to develop, following initial infection, and 

another year before the plant is producing berries. 

Effects: Young 

or small trees are seldom 

infected by true mistletoe. 

In nearly all cases, initial 

infection occurs on larger 

or older trees because 

birds prefer to perch in 

the tops of taller trees. 

Severe buildup of mistletoe 

often occurs within an 

infected tree because birds 

are attracted to and may 

spend prolonged periods 

feeding on the mistletoe 

berries. True mistletoes are not aggressive pathogens. They use the 

host xylem as a water source and do not cause mortality until water 

availability to the host is limited. In some hosts, infected portions of 

Mistletoes

Figure 255. True mistletoe on juniper. 

Figure 256. Phoradendron macrophyllum 

on Arizona sycamore. 
186

the tree often exhibit galls on branches or burls in the trunk. On oaks 

and cottonwoods, branch dieback is associated with galls formed by 

the corresponding mistletoe. 

Similar Insects and Diseases: Deformities caused by 

canker and rust fungi can resemble those caused by mistletoe. 

References: 25, 35, 84, 92

Mistletoes

Figure 257. 

Phoradendron 

californicum has red 

berries that ripen in 

winter. 

Figure 258. Desert 

mistletoe plants are 

red when full of fruit. 

Figure 259. True 

mistletoes are easy to 

spot on deciduous trees 

like this mesquite tree.
187

Mistletoes

Principal Hosts and Distribution 

of True Mistletoes in Arizona and New Mexico

Common 

Name Species Name Principal Host Distribution

Bigleaf 

mistletoe

Phoradendron 

macrophyllum

(Engelm.) 

Cockerell 

Most riparian 

hardwood species, 

except oaks

Throughout lower 

elevation riparian 

areas of both 

states

Southwestern 

oak mistletoe

Phoradendron

coryae Trel.

Oak species Throughout live 

oak woodlands 

and lower 

elevation gambel 

oak areas of both 

states

Desert 

mistletoe

Phoradendron

californicum Nutt.

Leguminous trees 

and shrubs (e.g. 

Mesquite (Prosopis

spp.), Acacia 

(Acacia spp.), Palo 

Verde (Cercidium

spp.), and ironwood 

(Olneya spp.)

Throughout the 

ranges of host 

types in Arizona 

and extreme 

southwest corner 

of New Mexico

Figure 260. 

Phoradendron 

densum on 

Arizona 

cypress. 
188

Juniper 

mistletoe

Phoradendron 

juniperinum

Engelmann

All juniper species Throughout 

juniper 

woodlands of 

Arizona and New 

Mexico

Hairy juniper 

mistletoe

Phoradendron 

capitellatum Torr. 

ex Tel.

Utah, alligator and 

red-berry juniper

Southern Arizona 

and southwest 

New Mexico

Texas juniper 

mistletoe

Phoradendron 

hawksworthii

Wiens & CG Shaw

Alligator and oneseed juniperSoutheastern New 

Mexico

Dense 

mistletoe

Phoradendron 

densum Torr. ex 

Tel.

Arizona cypress Central Arizona

White fir true 

mistletoe

Phoradendron 

pauciflorum Torr.

White fir Santa Catalina 

Mountains of 

southeast Arizona

Mistletoes

Figure 261. Phoradendron 

hawksworthii on juniper in 

New Mexico.

Figure 262. Phoradendron 

pauciflorum often kills 

tops of infected white fir.
189

Root disease fungi affect all tree species in the 

Southwestern Region, with Douglas-fir, true firs, 

spruce, and aspen being the most susceptible to 

damage. Susceptibility also varies by tree age, genetics, type of root 

disease pathogen present and site history. 

Root disease or decay fungi spread from roots of diseased 

trees to those of healthy ones. They start in a tree or stump and 

spread slowly outward in all directions, resulting in a slowly 

enlarging group of dying and dead trees. The oldest kills are located 

at the center of infection with a fringe of recently killed and dying 

trees around the outer edge. 

In the Southwest, these 

“centers” of disease are 

small in size, typically less 

than 1 acre.

Root disease is 

referred to as “a disease of 

the site” because the fungi 

colonize dead and dying 

trees and remain in dead 

roots and soils for many 

years. Many of these 

fungi have the ability to 

act as both pathogens in 

live trees and saprophytes in dead wood material. Not only are the 

current trees affected, but also trees that become established in the 

future. Some root disease fungi have been shown to remain alive 

and active in infested sites for more than 50 years.

The aboveground symptoms of trees affected by root disease 

include chlorosis, reduced needle length, progressive thinning 

of foliage, fading crown, reduced tree growth, and death. These 

symptoms are similar to those caused by drought, high water table, 

and bark beetle attack. However, the decline of trees affected 

Root Disease

Figure 263. Fruiting bodies of root disease 

fungi are located at the base or roots of 

infected trees.
190

by root disease usually extends over a period of a few to several 

years and not all trees succumb at the same time. The other causes 

of decline kill trees more 

rapidly, generally in 1 to 2 

years, and a group of trees all 

die at the same time. Bark 

beetles commonly attack trees 

weakened by root disease 

infection.

The incidence of root 

disease often relates to the 

amount of human activity in 

forest sites. Harvesting timber 

from infected stands often 

increases root disease activity. 

In addition, changes in forest 

structure brought about by 

fire suppression and selective 

logging have led to increases 

in tree species more prone to 

root disease.

Root Disease

Figure 265. Root 

disease infected 

trees are susceptible 

to bark beetle 

infestations. 

Figure 264. Root 

disease killed 

saplings associated 

with stumps. 
191

Root Disease

Armillaria or Shoestring Root Rot

Armillaria spp.

Hosts: 

Douglas-fir, spruce, 

ponderosa pine, 

subalpine fir, oak

Symptoms/

signs: The most 

diagnostic trait of 

Armillaria is the 

thick, fan-shaped mat 

of white mycelium in 

the cambium of roots 

and root crown. This 

may be accompanied 

by copious resin flow on bark surfaces, although this trait is not 

common in the Southwest. Other signs of the fungus include 

rhizomorphs, or black shoestring-like structures, on the outside of 

infected roots. The fruiting bodies of 

this fungus are commonly produced in 

clusters but can be found singly. The 

caps are yellow brown to dark tan, 

with small scales on upper surface. 

The stem is stout, tapering upward to a 

ring of tissue just below the cap. The 

decay is light yellow, soft and spongy 

to stringy often containing numerous 

black zone lines.

Biology: Armillaria root decay 

spreads primarily by rhizomorphs and 

root contacts. Armillaria invades the 

bark and cambial region of roots and 

the root collar, killing roots and trees of 

all sizes. Wood decay follows cambial 

attack, and the wood serves as a source 

Figure 266. White mycelial fans are found under 

the bark of infested trees. 

Figure 267. Armillaria 

produces shoestring-like 

rhizomorphs. 
192

of energy necessary for infection 

of new hosts. New infections are 

less common, occurring when 

mushrooms release windborne 

spores that germinate and 

colonize recently killed material. 

As with other root disease fungi, 

Armillaria can persist for decades 

in decaying wood in soil. 

Armillaria often acts in 

conjunction with other secondary 

pests and pathogens. For example, 

Dendroctonus and fir engraver beetles 

may attack trees with this root disease.

Effects: Armillaria is the most 

common root disease in the Southwest 

and may account for up to 80 percent 

of the root disease conifer mortality in 

the region. There are over 10 species of 

Armillaria, some are virulent parasites 

while others are opportunists that act 

selectively on small or weak individuals 

such as those shaded by taller plants, 

defoliated by insects, attacked by other 

fungi, or weakened by drought. 

Similar Insects and Diseases: 

Other fungi such as Fomitopsis pinicola

produce white mycelium beneath the bark of infected stumps, but the 

mycelium is not thick and fan-shaped like that produced by Armillaria

spp.

References: 31, 90, 92, 112, 114

Root Disease

Figure 268. Fruiting bodies of 

Armillaria spp. 

Figure 269. Decay of 

Armillaria is soft and spongy. 
193

Root Disease

Annosus Root Rot

Heterobasidion annosum (Fr.:Fr.) Bref. 

(Fomes annosus (Fr.:Fr.) Cooke) 

Hosts: White fir, subalpine fir, ponderosa pine

Symptoms/signs: Fruiting bodies of annosus are greybrown on the upper surface with an undersurface that is chalky 

white with pores. They are found on the underside of decayed roots 

and slash, inside stumps (common in the Southwest), or under the 

duff at the base of infected stumps and trees (although rare in the 

Southwest). H. annosum leads to crown thinning and mortality or 

windthrow, the latter of 

which can occur before 

aboveground symptoms 

are evident. 

Biology: 

Spores of H. annosum

are produced on 

conks in decayed 

stumps or on roots of 

windthrown trees. The 

most common means 

Figure 270. 

Fruiting bodies 

of H. annosum 

are often flat 

with the pores 

facing down. 

Figure 271. Heterobasidion annosum is commonly found 

on underside of roots and inside stumps. 
194

of initial entry of H. annosum into a site is via airborne spores that 

germinate on freshly cut stumps and basal wounds. Mycelium of 

H. annosum quickly colonizes the stump and grows into its roots. 

Transmission to adjacent trees occurs via root contacts. In live trees, 

the fungus decays woody root systems and then advances to the root 

collar where it may surface to the cambium and kill by girdling as in 

ponderosa pine, or progresses more slowly through roots to the stem 

and causes butt decay as in true fir. 

Although most conifers are susceptible to infection, there 

appear to be two types of annosus in North America, each of 

which has specific host preferences. One type infects true firs, and 

sometimes spruce and Douglas-fir. The other infects ponderosa 

pine but may also infect juniper. Like Armillaria, H. annosum is a 

common decayer of dead woody material as well as a pathogen. 

Root Disease

Figure 272. 

Characteristic 

white pocket rot 

of H. annosum. 
195

Root Disease

Effects: This is one of the most important forest tree 

diseases in temperate zones worldwide. Damage to forests in North 

America has been most severe in the Southeast, where intensive 

forestry has the longest 

history. In the Southwest, 

annosus root disease is the 

second most common root 

disease of conifers. It is 

found most often on true 

firs; however, there are 

areas where it is common 

in ponderosa pine. Infected 

trees are predisposed to attack 

by bark beetles. 

Similar Insects and 

Diseases: The aboveground 

symptoms are similar to those 

caused by other root disease 

fungi. 

References: 29, 53, 

59, 73, 88, 92, 114

Figure 273. Wood discoloration is an 

early sign of annosus decay.
196

Tomentosus Root Disease

Inonotus tomentosus (Fr.) Teng

Hosts: Spruce and Douglas-fir

Symptoms/signs: Fruiting bodies of I. tomentosus most 

commonly develop in August and September. They are small (usually 

less than 10 cm in diameter), mushroom shaped, and have a lower 

pore surface from which the spores are released. Although leathery, 

they are annual. The upper surface is yellow-brown to rust-brown and 

velvety, and becomes dark brown with age. The early stage of decay 

is characterized by a red-brown discoloration in the heartwood of 

roots. The late stage is also reddish brown but appears lighter because 

of numerous 

small elongate 

pockets with 

pointed ends, 

filled with white 

mycelium. This 

type of decay 

is known as a 

white pocket 

rot. The most 

distinctive 

characteristic 

of tomentosus 

rot is that a 

cross section 

of an infected stem in advanced stages of decay has a honeycomb 

appearance. 

Biology: Tomentosus root disease spreads primarily by 

root-to-root contact, however, infection by spores can occur through 

deep wounds in roots. There is no evidence that spores colonize 

stump surfaces as with annosus root disease. Diseased trees occur 

singly or in groups. The fungus spreads both outward in roots and up 

into the butt. Diseased roots have dead, decayed distal portions and 

red-brown, resin-soaked wood extending into the living portion and 

Figure 274. Leathery I. tomentosus fruiting body.

Root Disease
197

Root Disease

the butt. Advanced decay develops slowly and expands to involve 

both deep-lying wood and sapwood near the cambium. Infected trees 

often die standing, but sometimes blow over while alive because of 

advanced decay in major roots or butt. I. tomentosus has been found 

to persist for more than 50 years in decaying wood in soil. 

Effects: Although tomentosus root disease has been 

observed in spruce/fir and transition forests throughout the Southwest, 

there is little information available on the extent and damage from 

this disease. In other parts of the country, blowdown caused by 

tomentosus root disease has initiated spruce beetle (Dendroctonus 

rufipennis) outbreaks but that has not been reported here.

Similar Insects and Diseases: I. tomentosus and I. circinatus

are nearly identical and difficult to differentiate macroscopically. 

Microscopically, I. circinatus can be differentiated from I. tomentosus

based on hooked structures the latter does not produce. I. tomentosus

and I. circinatus

are sometimes 

called false 

velvet-top fungi, 

because of the 

similarity of 

the conks of 

these fungi with 

that produced 

by Phaeolus 

schweinitzii, 

which is the 

real velvet-top 

fungus. 

References: 29, 92, 102, 110

Figure 275. Red-brown discoloration of roots decayed 

by I. tomentosus. 
198

Schweinitzii Root and Butt Rot

Cow Patty, or Velvet Top Fungus

Phaeolus schweinitzii (Fr.:Fr.) Pat.

(Polyporus schweinitzii Fr.:Fr.).

Hosts: Douglas-fir, ponderosa pine, southwestern white 

pine, spruce

Symptoms/signs: Trees infected with P. schweinitzii do 

not typically show outward symptoms, so the presence of disease 

is usually not realized until a tree breaks or is windthrown due to 

loss in structural support. The fruiting bodies of P. schweinitzii

often emerge through soil from decayed roots. They have a velvety 

surface which is yellow to orange at first, then turning brown with 

a yellow margin. It turns a dark red brown upon aging, is crumbly 

and can be mistaken for a cow pie at this point, hence the nickname 

“the cow patty 

fungus.” Incipient 

decay appears as 

a light yellow to 

pale reddish-brown 

color. As the decay 

advances, the color 

intensifies and 

the wood rapidly 

loses strength. In 

advanced stages 

of decay, the wood 

breaks up into 

large cubes that 

are crushed easily, 

Root Disease

Figure 276. Fruiting structures of P. schweinitzii

popping up from decayed roots.
199

Root Disease

and the butt portions 

of infected trees can be 

swollen.

Biology: 

Spores likely initiate 

most P. schweinitzii

infections. P. 

schweinitzii is unusual 

in that the fungus 

establishes itself in 

forest soil and enters 

trees through root tips. 

There is no root-to-root 

spread as used by other 

root disease causing fungi. Decay is confined to the roots and lower 

1-2 m of the butt log, rarely extending much higher. 

Effects: Schweinitzii root and butt rot is a major disease 

of older trees. It causes decay of the roots and lower stem and the 

resulting strength loss predisposes trees to windthrow and breakage. 

Similar Insects and Diseases: The fruiting bodies of I. 

tomentosus and I. circinatus are similar to Phaeolus schweinitzii 

since they are all velvety on top when fresh and have a pore surface 

beneath. However, P. schweinitzii fruiting bodies are larger, greater 

than 15 cm in circumference, while the other two are about 5 cm 

maximum. 

References: 30, 92

Figure 277. Young specimen of P. schweinitzii. 
200

Black Stain Root Disease

Leptographium wageneri (Kendrick) MJ Wingfield

Hosts: Piñon and Douglas-fir

Symptoms/signs: Like other root diseases, black stain 

usually exhibits symptoms of gradual decline before tree death. In 

the early stages of decline, terminal growth is reduced and older 

needles become chlorotic. As the disease progresses, older needles 

are shed prematurely, new needles are somewhat stunted and yellow, 

and reduced internodal growth is evident on lateral branches. Very 

small trees may succumb quickly without exhibiting gradual decline 

symptoms. 

Black stain root disease is distinguished from other root 

diseases by the dark-brown to purple-black discoloration in the 

sapwood of the lower bole and root collar. When observed in cross 

section, the black stain appears in arcs roughly concentric with the 

growth rings. 

Root Disease

Figure 278. Black stain of piñon caused by Leptographium wageneri. 
201

Root Disease

Biology: The Southwestern Region has two physiologically 

and morphologically distinct variants of black stain root disease. 

Leptographium wageneri var. wageneri is pathogenic to piñons and 

L. wageneri var. pseudotsugae (Harrington et Cobb) causes black 

stain in Douglas-fir. Both of these have been found in New Mexico 

but not in Arizona. A third variety L. wageneri var. ponderosum 

infects hard pines in California but has not been found in the 

Southwest. 

Effects: Black stain root disease fungi grow in sapwood and 

plug tracheids, which prevents water transport and causes a wilting 

and rapid tree decline and death. Unlike Armillaria spp. and H. 

annosum, L. wageneri does not cause wood decay and dies with its 

host. 

Black stain root disease affects groups of trees in distinct 

infection centers. Typical infection centers have trees in various 

stages of decline near the perimeter and dead trees in the interior 

where infection originated. 

Similar Insects and Diseases: Blue stain fungi, which are 

often confused with black stain fungi, are usually a lighter color and 

typically are wedge-shaped in cross-section and they can discolor the 

entire sapwood radius. 

References: 37, 92
202

Ganoderma Root Rot

Artist’s Conk

Ganoderma applanatum (Pers.) Pat.

Hosts: Aspen

Symptoms/signs: Infected trees often break or fall before 

death, however, a fruiting body or conk can be found at the base of 

most infected trees. The tough semicircular conk is usually found 

near ground level. It has a brown upper surface with a white rim and 

an undersurface that is white and stains when touched or scratched. 

The latter trait allows for artistic expression that is permanent if the 

conk is allowed to dry. G. applanatum produces advanced whitemottled decay in the large roots and lower parts of the stem.

Biology: G. applanatum infection occurs at wounds and 

the fungus attacks sapwood, heartwood, and cambium. The whiteRoot Disease

Figure 279. Ganoderma applanatum conks are often found at the base of 

infected trees. 
203

Root Disease

mottled rot is usually concentrated in large roots (larger than 5 cm in 

diameter) and basal part of the stem, but can extend up into the trunk 

for a meter or more. The larger roots are believed to act as avenues 

of spread to new hosts. 

Effects: G. applanatum is found in almost all aspen stands 

but is more abundant on moist sites with deep soils. Windthrow is 

common.

Similar Insects and Diseases: Although there are other root 

decay fungi of aspen, G. applanatum is the most prominent and the 

only one that produces a tough woody-conk at ground line in live 

trees in the Southwest.

References: 38, 92

Figure 280. Trees often topple over due to severe decay of major 

roots. 
204

The symptoms of noninfectious, or abiotic, disorders 

closely resemble those of some parasitic diseases 

making it difficult to determine the cause. Some of 

these disorders serve as an entry for pathogens, such as canker and 

wood decay fungi.

Noninfectious Disorders

Figure 281. Aspen stand with mortality caused by frost and drought.
205

Noninfectious Disorders

Drought

Water deficit develops as a normal phenomenon in plants 

when water loss by transpiration exceeds the rate of absorption from 

soil. Chronic injury results from long-term exposure to low water 

supplies (e.g. in areas with poor 

soils) and is expressed by growth 

loss and increased susceptibility 

to parasitic fungi and insects. 

Acute injury occurs under 

extreme water deficiency and is 

expressed by significant growth 

loss or death. Symptoms of 

drought damage include wilting, 

discoloration of foliage and 

premature leaf fall. Progression 

within the crown is from the 

top down and outside in, and 

the roots are usually the last portions 

to die. Symptoms can be similar to 

those of trees suffering from root 

disease, except that with root diseases, 

the roots die before the foliage. In the 

Southwest, drought symptoms have 

been observed in many trees including 

aspen, ponderosa pine, piñon, and 

soapberry.

Winter drought is particularly 

harmful in Southwestern upland 

forests and can render large areas 

vulnerable to bark beetles and 

wildfire. 

References: 82, 92

Figure 282. Western soapberry with 

branch dieback following dry spring.

Figure 283. Aspen branch 

dieback during summer 

drought.
206

Frost

Frost damage of many tree species 

including aspen, locust, spruce, and oak has 

been observed throughout the Southwest. 

The tolerance of foliage and small branches 

to cold temperature depends on their 

“hardiness,” which is closely correlated with 

the time of year and species. Temperatures 

just above freezing and short photoperiods 

induce frost hardiness. The sudden onset 

of below-freezing temperatures (frosts) in 

spring or early autumn can severely damage 

unhardened tissues, killing young shoots and 

leaves or needles. 

As temperatures rise in late winter 

and early spring, plants deacclimate until, by 

the time growth begins, they can no longer tolerate more than a few 

degrees of frost. Leaves and stems killed by spring frost are usually 

small and succulent at the time of injury. More mature leaves and 

stems can tolerate lower temperatures. After thawing, damaged 

tissues at first appear water soaked and soon become shriveled and 

reddish brown, dark brown, 

or black, depending on 

the species. Dead leaves 

and shoots break off or 

abscise during the next 

several weeks. New shoots 

and leaves begin to grow 

almost immediately and 

soon mask the early season 

damage.

References: 82, 

92

Noninfectious Disorders

Figure 284. Aspen 

leaves succumb to June 

frost.

Figure 285. Newest and most sensitive 

growth of fir killed by frost.
207

Noninfectious Disorders

Winter Injury

There are several 

different types of winter 

damage of conifers in the 

Southwest. Water deficit can 

develop in dormant evergreens 

during warm weather in late 

winter or early spring when 

needles transpire water from 

leaves and stems while the 

soil is cold or frozen. Roots 

extract insufficient water 

from cold soil and none 

from frozen soil. Freeze damage occurs when needles no longer have 

enough moisture to survive normal nighttime temperatures. Freeze 

damage can also follow untimely deacclimation from temporary warm 

weather. Ponderosa pine and alligator juniper are the species most 

often observed with damage by these phenomena. Sometimes the 

result is trees that have needles with brown tips and green bases, and 

other times trees may have winter-killed needles that are completely 

brown regardless of age, but the branch and bud tissues are still green 

and viable. In either 

case, trees recover 

during the growing 

season. Occasionally, 

severe freeze damage 

near the upper 

elevational limits of a 

particular tree species 

causes mortality or 

topkill.

References: 

82, 92

Figure 286. Needle bases of 1-year 

needles are green but tips are brown.

Figure 287. Winter injury can be mistaken for 

mortality at a distance.
208

Red Belt

Red belt, another type of winter damage, is named because 

of the appearance of red needled trees distributed in well-defined 

bands varying from less than 20 to as much as 1,000 yards wide on 

slopes and benches. These events are associated with the sudden 

occurrence of warm, dry winds (e.g. Chinook winds) that produce a 

temperature inversion. A relatively thin layer of warm air arrives that 

cannot mix downward and continues to contact side slopes. Trees 

exposed to unseasonably warm air by day receive seasonably cold air 

at night. This alteration of warm and cold air exposure, along with 

the frozen condition of the soil, results in desiccation injury because 

daytime transpiration removes moisture from the needles more 

rapidly than roots in frozen soil can replace it. Later, older needles 

fall off, leaving only current year needles on living branches after 

bud-break.

References: 82, 92

Figure 288. A band of cold air gets trapped at a specific elevation 

around mountains.

Noninfectious Disorders
209

Noninfectious Disorders

Windthrow

Windthrow is most common when soils are shallow and/

or water saturated. Spring is very windy throughout much of the 

Southwest, and is the time when blowdown occurs in many root 

diseased infected areas. Blowdown is also prevalent in winter 

months when trees are loaded with snow. 

More severe windthrow damage takes place with tornadoes 

and microbursts, which occasionally occur in northern Arizona. 

Tornadoes and microbursts both result in windthrown trees lying 

parallel to one another in the same direction as the storm. Tree 

species with shallow root systems (e.g. spruce) are more prone to 

windthrow.

Reference: 107

Figure 289. 

There are 

typically decay 

or soil defects 

associated with 

windthrown 

trees.

Figure 290. Tornadoes 

and microbursts have 

been known to knock 

down a swath of trees.
210

Lightning

Lightning damage is thought to be responsible for 

approximately 2 percent of the annual tree mortality in the region. 

However, many more trees are slightly damaged than are killed 

by lightning. Killed trees are often blown apart at impact or soon 

colonized by bark beetles. 

Damage is in the form of a long 

narrow furrow in which the bark 

and a thin layer of wood are 

blown out. Sometimes, but not 

always, lightning damage can 

result in internal decay that may 

provide cavity-nesting habitat for 

wildlife. 

References: 114

Figure 291. Lightning struck trees 

are often attacked by bark beetles.

Figure 292. Many lightning 

struck trees survive for decades 

and are slowly decayed.

Noninfectious Disorders
211

Noninfectious Disorders

Salt Damage

The uptake of salts by the roots of roadside trees is a 

common problem wherever sodium chloride, calcium chloride, and 

magnesium chloride are applied to de-ice highways in the winter or 

for dust abatement in the summer. Most of the time symptoms are 

insignificant and limited to tip burn, where the bases of the needles 

remain green and trees recover. However, a surprising amount of 

mortality may occur when magnesium chloride or calcium chloride 

is applied for dust abatement during or shortly before heavy 

rainstorms. Salts are 

leached off the road 

in heavy rains and 

travel into drainages 

where subsequent tree 

damage and mortality 

take place.

References: 

6, 82, 92

Figure 293. Salts applied for dust abatement 

cause as much damage as those applied for 

de-icing.

Figure 294. Most tree 

species experience tip 

burn from salt damage.
212

Burls

Burls are large woody, more or less hemispheric, swellings 

on the main stems of trees. Although some stem swellings are the 

result of pathogens, often the cause of burls is unknown. Burls may 

often bear many buds or sprouts. 

References: 92

Figure 295. The cause of burls is often unknown.

Noninfectious Disorders
213

Ungulates

Domestic livestock and wild ungulate browsing can cause 

severe damage to forest regeneration. Aspen forests in particular 

have suffered extreme damage. Rocky mountain elk are considered 

the primary threat to the 

long-term survivability 

of aspen, because they 

impact aspen in so 

many ways. Elk have a 

height advantage over 

other ungulates and are 

able to reach higher in 

the crowns of saplings, 

often snapping the main 

bole and killing it. Elk 

rub antlers on small 

diameter trees (7 to 15 

cm), creating wounds that 

allow entry for canker and wood 

decay fungi. Elk also gnaw or strip 

the bark (a.k.a. barking) of larger 

trees, allowing the entry of insects 

such as the bronze poplar borer. 

References: 38, 91

Animal Damage

Figure 296. Aspen suckers are heavily 

browsed by ungulates, especially elk.

Figure 297. Elk “bark” 

mature trees with their 

teeth.
214

Animal Damage

Figure 298. Elk 

snapped these 

saplings while 

feeding on 

foliage after a 

protective fence 

was removed.

Figure 299. 

Ponderosa 

pine 

browsed by 

ungulates.
215

Black Bear

Ursus americanus

Black bears rip 

wide strips of bark from 

trees, often starting at 

about 1 m from ground 

line. They forage on 

the cambial zone in the 

lower bole by removing 

or peeling the bark with 

their claws and scraping 

the vascular tissue with 

their incisors. Trees are 

often girdled and die 

from one stripping, but 

sometimes survive. The 

wound left in partially 

girdled trees can lead to 

extensive decay. Bears 

also break branches 

on oak trees to access 

acorns.

In the White 

Mountains and Pinaleño 

Mountains of eastern 

Arizona, black bear strip 

the bark of southwestern 

white pine and subalpine 

fir greater than 25 cm in diameter. This activity is so widespread in 

some areas that it is difficult to find a large southwestern white pine 

or subalpine fir that has not been stripped. 

References: 46, 49, 93

Animal Damage

Figure 300. Black bears rip strips of bark 

from trees and feed on the cambium.
216

Porcupine

Although porcupines have a variable diet during the growing 

season, in the winter they chew through the outer bark of branches 

and boles (less than 2 centimeters in diameter) and feed on cambium. 

Coniferous trees are preferred and often girdled. Porcupine injury 

can be locally damaging 

because the animal tends 

to stay in a small area, 

killing the tops of many 

trees. Since porcupine 

populations tend to 

fluctuate, trees often 

form new leaders and 

grow to maturity. 

Figure 301. Porcupine chew through the 

bark and feed on the cambium.

Animal Damage
217

Sapsucker

Sapsuckers are only one of several groups of birds that cause 

tree damage. When feeding they puncture the bark in horizontal 

lines around tree limbs and main stems. These punctures sometimes 

serve as entry points for stain or decay fungi. Sapsuckers feed 

on many species of 

conifers and hardwood 

trees.

Animal Damage

Figure 302. Sapsuckers drill parallel rows of 

holes and feed on sap and insects caught in the 

sap.
218

Glossary

A

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 a biotic disease. 

Aecia: A cuplike structure bearing aeciospores in the rust fungi.

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., rust fungi that use two hosts to 

complete a life cycle. 

Arthropod: Largest phylum in the animal kingdom including 

insects, crabs, spiders, etc. 

B

Basidiospore: Spore formed after sexual recombination has 

occurred.

Biotic: A living organism. 

Blue stain: A bluish to grayish discoloration of sapwood of a killed 

tree caused by fungi that utilize the material without causing 

decay, has no effect on the strength of the wood.

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: Fragments of phloem or wood excavated by adult bark 

beetles as it bores through the outer bark; brown to tan, often 

found in small piles in bark crevices and around the base of 

a tree. 
219

Brood: The offspring or next generation of young hatched from eggs 

laid by one series of parents, and that mature about the same 

time.

C

Callus: Healing tissue of trees on branches, boles, or roots that 

attempts 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. 

Cocoon: A thin covering often largely of silk which an insect larva 

forms about itself and in which it passes the pupal stage.

Conk: Fruiting body of a wood-decay fungus, often hoof or bracketshaped and perennial, although some are annual; other than a 

mushroom. 

Context: Interior tissue of a fruiting body. 

Cornicle: Dorsal tubular processes on the posterior portion of the 

abdomen; common on aphids.

Cortex: Rind or outer layer.

Crawler: The dispersal life stage of aphids and scale insects.

Crop tree: Tree left after thinning, often because of superior quality 

or species and lacking defect or disease. 
220

D

Decay: Rot or destruction and decomposition of plant material by 

fungi; wood decay is typically separated into brown or white 

rot depending on the wood compounds consumed. 

Declivity: A term used to describe the descending distal slope of 

beetle forewings. For example, Ips beetles have spines on 

their elytral declivity, while Dendroctonus species have a 

rounded elytral declivity.

Defoliator: An organism that causes damage to plant foliage.

Diapause: The dormant phase of some insects. Can be either 

facultative or obligatory.

Dioecious: Male flowers and female flowers on different individual 

plants, as in mistletoe. 

Disease: A disturbance of a plant caused by a pathogen (not an 

insect) or environmental condition that interferes with the 

plant’s normal growth, structure, or reproduction. See also 

abiotic disorder. 

E

Egg niche: A small impression or incision created by female bark 

beetle in which an egg is deposited.

Elytra: Hardened forewings of beetles that serve to protect the 

functional posterior wings.

Endemic: Typical, nonepidemic population.

Endophytic: An organism living within tissues of a live plant, as in 

mistletoe.

Epidemic: Large-scale, temporary increase in an insect or disease 

population.
221

F

Fecundity: Ability to produce young.

Flagging: Dying or recently dead branches; 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. Fungi cause decay of plant material. 

G

Gall: An abnormal growth of plant tissue, stimulated by insect or 

fungal activity. 

Gallery: Engraving of cambium or bark caused by bark beetles. 

Beetles create both egg galleries and feeding galleries. 

Design of egg galleries are used to identify beetle species.

Genus: A group of closely related species. Similar genera are 

grouped in a family. 

Girdle: The act of damaging the cambium completely around the 

circumference 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.
222

H

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 confined to the heartwood.

Heterocyclic: Fungi that requires two different hosts to complete 

their life cycle; i.e., some rust fungi.

Hibernacula: Shelters occupied during the winter by dormant 

insects, i.e., spruce budworm larvae overwinter in 

hibernacula.

Honeydew: Sugary liquid excretion of aphids or scale insects.

Host: A plant that is invaded by a parasite and from which the 

parasite obtains its nutrients.

Hypha: (plural=hyphae) a single branch of a mycelium. 

I

Incipient decay: The early stage of decay in which degradation has 

not proceeded far enough to soften the wood or to cause a 

perceptible reduction in hardness. Such strength properties 

as toughness or impact strength are appreciably reduced in 

wood with incipient decay, but the damage is not normally 

visible to the naked eye.

Infection: The establishment of a parasite within a host plant.

Instar: The stage of an insect between successive molts.

L

Lanceolate: Spear-shaped, tapering at each end.
223

Larva: Immature form of an insect such as a caterpillar, grub, or 

maggot.

Lesion: A localized area of discolored, diseased tissue.

Latent infection: The state in which a host is infected with a 

pathogen but does not show any symptoms.

Life cycle: The stage or successive stages in the growth and 

development of an organism that occur between the 

appearance and reappearance of the same stage (e.g., spore) 

of the organism. 

M

Metamorphosis: Change in form and structure between different 

life stages of insects. Some insects have incomplete 

metamorphosis (egg, nymph, adult), while others have 

complete metamorphosis (egg, larva, pupa, adult).

Midge: Tiny two-winged flies.

Molt: Process of shedding the exoskeleton, the insect “skin.”

Monogamous: Mating with only one individual.

Mushroom: Fleshy fruiting body of a fungus that has either 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; associated with Armillaria

spp.

Mychorrhizae: Association between plant rootlets and specialized 

fungi that is beneficial to their tree associate by assisting in 

nutrient and water uptake.
224

N

Necrotic: Dead plant cells or tissues.

Nuptial chamber: Mating site.

Nymph: Immature form of an insect resembling the adult, except for 

incomplete wing development.

O

Obligate parasite: An organism capable of existing only as a 

parasite on a live host.

Overwinter: Term used to describe what life stage an insect passes 

the winter in.

Oviposit: Lay or deposit eggs.

Ovipositor: Egg-laying apparatus.

P

Parasite: An organism living in or on another living organism (host) 

and obtaining its food from the latter. 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. Many pathogens of forest trees are fungi. 

Perennial: Lasting for several years or more. 

Pheromone: Chemicals produced by one individual to affect or 

alter the behavior of another individual of the same species. 

Many bark beetle species produce both aggregation and 

anti-aggregation pheromones, which mediate the colonizing 

behavior of other beetles.
225

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 resin mixed with bark, wood borings, 

and insect excrement that form 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.

Proleg: A fleshy leg that occurs on the abdominal segment of some 

insect larvae but not in the adult.

Prothorax: The anterior of the three thoracic segments.

Punk knot: An overgrown knot filled with old conk material or the 

beginning of a new conk, also called blind conk, reliable 

indicator of the presence of some wood decay fungi, i.e., 

Phellinus pini. 

Pupa: Inactive stage of an insect, a transitional stage from larva to 

adult.

R

Radial growth: One-half the diameter growth of a tree.

Resinosis: Pitch or resin flow of a host tree in response to disease.

Rhizomorph: A specialized form of mycelium produced by certain 

fungi (e.g. Armillaria spp.) consisting of several strands of 

hyphae twisted together so as to be rootlike, and covered 

with a protective sheath. 

Rot: Decay or deterioration of organic material through the 

enzymatic activity of microorganisms. 
226

Rust: A disease caused by one of the rust fungi; highly specialized 

pathogens that are obligate parasites, which frequently 

require two different types of hosts to complete their life 

cycles (heterocyclic), and produce orange, yellow, or brown 

spores. 

S

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. 

Scales: A small thin, plate-like structure found on the wings of 

Lepidoptera.

Serrate: Saw-toothed edge. 

Shootborer: Insects that feed in the pith of shoots.

Sign: The pathogen or its parts or products seen on a host plant.

Slash: Debris such as logs, bark, and branches left after cutting 

timber. 

Spore: The reproductive unit of fungi consisting of one or more 

cells, analogous to the seed of green plants.

Sporophore: Fruiting body of a fungus that produces spores (i.e., 

mushroom or conk). 

Stage: A distinguishable period of growth and development of an 

insect, i.e., the larval stage of an insect.

Stomata: Breathing pore in the epidermis (outer layer) of a plant.

Subcortical: Below the bark.
227

Sunscald: Death of bark due to sudden exposure to sun. This is 

common in mature aspen where neighboring trees have been 

removed.

Symbiotic: An intimate association between two species, which 

benefits both.

Symptom: The external and internal reactions or alterations of a 

plant as a result of a disease or insect.

Systemic: Throughout the plant host tissues, usually surviving from 

year to year.

T

Target canker: Perennial canker produced by a fungus which 

invades live tissue during the host dormant season, and 

survives in dead material during the host growing season.

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.

V

Vector: An organism such as an insect that transmits a pathogen.

W

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 pockets. In 

advanced stage, may create a large hollow in a tree.
228

Windthrown: Trees uprooted by wind. The term is also sometimes 

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).

Woodborer: Diverse group of insects that feed at least in part in the 

wood. Many of these insects begin their larval stage in the 

cambium before constructing galleries in the xylem (wood).

X

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.

Z

Zone line: Narrow black to brown lines in decaying wood formed 

by fungi.
229

Photography and Illustration Credits

Robert L. Anderson (USDA Forest Service, www.forestryimages.

org); 188

Ronald F. Billings (Texas Forest Service, www.forestryimages.org); 

45, 149

Bob Cain (USDA Forest Service, Rocky Mountain Region); 190

Clemson University (USDA Cooperative Extension Slide Services, 

www.forestryimages.org); 44

Conklin, David A.; 2, 15, 37, 191, 194-195, 198, 202, 204, 218-224, 

230-235, 238, 240-252, 254-257, 261, 263, 295

Whitney Cranshaw (Colorado State University, www.forestryimages.

org); 61-62

Tom DeGomez (University of Arizona, Cooperative Extension); 

Cover-1,133

Jerald E. Dewey (USDA Forest Service, www.forestryimages.org); 

13, 24, 26, 46, 80

Brian Geils (USDA Forest Service, Rocky Mountain Research 

Station); 228-229

John H. Ghent (USDA Forest Service, www.forestryimages.org); 274

Kennenth E. Gibson (USDA Forest Service, www.forestryimages.

org); 83c, 104, 122

Thomas E. Hinds (USDA Forest Service, Rocky Mountain Research 

Station); 176, 210-211, 216, 225,

Edward Holsten (USDA Forest Service, www.forestryimages.org); 

50, 57, 170

Gerald J. Lenhard (Louisiana State University, www.forestryimages.

org); 43 

R. Ladd Livingston (Idaho Department of Lands); 83a, 117, 150

Ann Lynch (USDA Forest Service, Rocky Mountain Research 

Station); 41 

David McComb (USDA Forest Service, www.forestryimages.org); 5
230

Roy Morales (USDA Forest Service, Carson NF); 49

Minnesota DNR (Minnesota Department of Natural Resources 

Archives, www.forestryimages.org); 51

A. Steven Munson (USDA Forest Service, www.forestryimages.org); 

118 

Donald Owen (California Department of Forestry and Fire 

Protection, www.forestryimages.org); 130

Jeff Schalau (University of Arizona, Cooperative Extension); 92

John Schwant (USDA Forest Service, www.forestryimages.org); 189

Borys Tkacz (USDA Forest Service, Washington Office); cover-2, 

174, 178, 183-184, 275, 284, 294

Scott Tunnock (USDA Forest Service, www.forestryimages.org); 

76-77, 144 

Michael R. Wagner (Northern Arizona University); Cover-3, 20-21, 

23, 25, 27-28, 30-32, 48, 75, 78, 151-157, 161, 164

USDA Forest Service files; 72, 102

USDA Forest Service, Intermountain Region Archives (www.

forestryimages.org); 3, 10, 162

USDA Forest Service, Northern Region; 83b (R1-03-08)

USDA Forest Service, Rocky Mountain Region Archives (www.

forestryimages.org); 4, 7, 8, 11, 29, 52, 105, 107, 127

USDA Forest Service, Southwestern Region; Cover, 1, 3-4, 6, 9, 14, 

16-19, 33-36, 38-40, 42, 47, 53-56, 58-60, 63-71, 73-74, 79, 

81-82, 84-91, 93-101, 103, 106, 108-116b, 119-121, 123-

126, 128-129, 131-132, 134-143, 145-148, 158-160, 163, 

165-169, 171-173, 175, 177, 179-182, 185-187, 192-193, 

196-197, 199-201, 203, 205-209, 212-215, 217, 226-227, 

236-237, 253, 258-260, 262, 264-273, 276-283, 285-293, 

296-302

Detlev Vogler, USDA Forest Service, Pacific Southwest Research 

Station; 239
231

Instructions for Submitting 

Insect and Disease Specimens 

for Identification

Both zone offices are equipped to receive forest insect 

or disease specimens submitted from the field for identification. 

Specimens may be shipped to the appropriate zone office (addresses 

shown on next page). The following procedures for collecting and 

shipping specimens should be used:

Collecting

1. Adequate material should be collected

2. Adequate information should be recorded, including:

a. location of collection

b. when collected

c. who collected the specimen

d. host description (species, age, condition, etc.)

e. area description (forest type, site conditions, etc.)

f. unusual conditions (frost, poor drainage, etc.)

3. Personal opinion of the cause of the problem may be 

helpful.

Packing

1. Larvae and other soft-bodied insects should be shipped 

in small screw-top vials or bottles containing at least 70 

percent isopropyl (rubbing) alcohol. Make sure bottles 

are well sealed.

2. Pupae and hard-bodied insects may be shipped either 

in alcohol or in small boxes. Specimens should be 

placed between layers of tissue paper in the boxes. Pack 

carefully and make sure there is little movement of 

material within the box. Do not pack insects in cotton.
232

3. Needle or foliage diseases: Do not ship in plastic bags as 

condensation can become a problem. Use a paper bag or 

wrap in newspaper. Pack carefully and make sure there 

is little movement within the box.

Mushrooms and conks: Do not ship in plastic bags. 

Either pack and ship immediately or air-dry and pack. 

To pack, wrap specimens in newspaper and pack into a 

shipping box with more newspaper. If on wood, include 

some of the decayed wood.

Federal Forest Health Zone Offices

Arizona Zone Forest Health

2500 South Pine Knoll Drive

Flagstaff, AZ 86001

New Mexico Zone Forest Health

333 Broadway Blvd., SE

Albuquerque, NM 87102

State Insect and Disease Specialists

Arizona 

Forest Health Program

P.O. Box 15018

Northern Arizona University

Flagstaff, AZ 86011

New Mexico

NMSU Coop. Ext. Forest Entomologist

New Mexico EMNRD, Forestry Division

P.O. Box 1948

Santa Fe, NM 87504
233

Selected References

1. Amman, G. D., M. D. McGregor, and R. E. Dolph, Jr. 1985. 

Mountain pine beetle. USDA Forest Service, Forest Insect 

and Disease Leaflet 2. 11 p.

2. Barr, B. A., D. L. Hanson, and C. S. Koehler. 1978. Red 

turpentine beetle – a pest of pines. University of California, 

Division of Agricultural Sciences Leaflet 21055. 4 p.

3. Beatty, J. 1979. Forest insect and disease conditions in 

the Southwest 1979. USDA Forest Service, Southwestern 

Region Publication 80-7, 29 p.

4. Beckwith, Roy C. 1973. The large aspen tortrix. USDA 

Forest Service, Forest Pest Leaflet 139. 5 p.

5. Blake, E. A., M. R. Wagner, and T. W. Koerber. 1985. 

Insects destructive to the ponderosa pine cone crops in 

northern Arizona. In: Proc. Conifer Tree Seed in the Inland 

Mountain West Symposium, Aug. 5-6, Missoula, MT. 

USDA Forest Service, Intermountain Research Station: 238-

242.

6. Bolander, P., ed. 1999. Dust palliative selection and 

application guide. Project Report. 9977-1207-SDTDC. San 

Dimas, CA: USDA Forest Service, San Dimas Technology 

and Development Center. 20 p. 

7. Borden, J. H., and M. McClaren. 1970. Biology 

of Cryptoporus volvatus (Peck) Shear (Agaricales, 

Polyporaceae) in southwestern British Columbia: 

distribution, host species, and relationship with subcortical 

insects. Syesis, Vol. 3: 145 – 154.

8. Cain, R., J. Cota, and C. Ward. 1990. Conifer pests in 

New Mexico. Rev. ed. (Albuquerque, NM): USDA Forest 

Service, Southwestern Region. 48 p.

9. Cain, R., and D. Parker. 1998. Conifer pests in New 

Mexico. Rev. ed. (Albuquerque, NM): USDA Forest 

Service, Southwestern Region. 50 p.
234

10. Carolin, V. M., and J. A. E. Knopf. 1968. The pandora 

moth. USDA Forest Service. Forest Pest Leaflet 114, 7 p.

11. Childs, T. W., K. R. Shea, and K. L. Stewart. 1971. 

Elytroderma disease of ponderosa pine. USDA Forest 

Service. Forest Pest Leaflet 42. 6p.

12. Conklin, D. A. 2000. Dwarf mistletoe management and 

forest health in the Southwest. USDA Forest Service, 

Southwestern Region, unnumbered report. 30 p.

13. Corn, M. L., E. H. Buck, J. Rawson, and E. Fischer. 1999. 

Harmful nonnative species: issues for Congress. National 

Council for Science and the Environment. Report RL30123. 

50 p.

14. Coulson R. N. and J. A. Witter. 1984. Forest Entomology: 

Ecology and Management. John Wiley & Sons, New York, 

NY. 669 p.

15. Cranshaw, W., D. Leatherman, W. Jacobi, B. Kondraitieff, 

and L. Mannix. 2000. Insects and Diseases of Woody Plants 

of the Central Rockies. Bulletin 506A. Colorado State 

University Cooperative Extension. Fort Collins, 283 p.

16. Dahms, C. W. and B. W. Geils, tech. eds. 1997. An 

assessment of forest ecosystem health in the Southwest. 

General Technical Report RM-GTR-295. Fort Collins, CO: 

USDA, Forest Service, Rocky Mountain Forest and Range 

Experiment Station. 97 p.

17. DeMars, Jr., C. J., and B. H. Roettgering. 1982. Western 

pine beetle. USDA Forest Service, Forest Insect and Disease 

Leaflet 1. 8 p.

18. Dunbar, C. S. and M. R. Wagner. 1990. Distribution 

of ponderosa pine (Pinus ponderosa) feeding sawflies 

(Hymenoptera: Diprionidae) in the United States and 

Canada. Entomol. News 101: 266-272.
235

19. Fellin, D. G. and J. E. Dewey. 1982. Western spruce 

budworm. USDA Forest Service, Forest Insect and Disease 

Leaflet 53. 10 p.

20. Ferrell, G. T. 1986. Fir engraver. USDA Forest Service, 

Forest Insect and Disease Leaflet 13. 8 p.

21. Filip, G. M., and Schmitt, C. L. 1990. RX for Abies: 

silvicultural options for diseased firs in Oregon and 

Washington. USDA Forest Service, GTR-PNW-252. 34 p.

22. Funk, A. 1985. Foliar Fungi of Western Trees. Canadian 

Forestry Service, Pacific Research Centre. 159 p.

23. Furniss R. L. and V. M. Carolin. 1977. Western Forest 

Insects. USDA Forest Service, Miscellaneous Publication 

No. 1339. 654 p.

24. Furniss R. L. and J. B. Johnson. 2002. Field Guide to the 

Bark Beetles of Idaho and Adjacent Regions. University of 

Idaho. 125 p.

25. Geils, B. W., J. Cibrian Tovar, and B. Moody, tech. coords. 

2002. Mistletoes of North American conifers. Gen. Tech. 

Rep. RMRS-GTR-98. Ogden, UT: USDA, Forest Service, 

Rocky Mountain Research Station. 123 p.

26. Geils, B. W.; Conklin, D. A.; Van Arsdel, E. P. 1999. A 

preliminary hazard model of white pine blister rust for 

the Sacramento Ranger District, Lincoln National Forest. 

USDA Forest Service, RMRS-RN-6. 6 p.

27. Gilbertson, R. L. 1974. Fungi That Decay Ponderosa Pine. 

Tucson: University of Arizona Press. 197 p.

28. Gilbertson, R. L., and M. Rosemeyer. 1986. Comandra 

blister rust on Mondell pine in Arizona. Arizona Plant 

Pathology, Unnumbered Bulletin. Tucson, AZ; Dept. of 

Plant Pathology, University of Arizona. 3 p.
236

29. Gilbertson, R. L., and L. Ryvarden. 1986. North American 

Polypores, Volume 1. Oslo: Fungiflora: 1 - 433.

30. Gilbertson, R. L., and L. Ryvarden. 1987. North American 

Polypores, Volume 2. Oslo: Fungiflora: 434-885.

31. Hagle, S. K.; Byler, J. W. 1994. Root diseases and 

natural disease regimes in forest of western U.S.A. In: 

Johansson, M. and J. Stenlid, eds. Proceedings of the Eighth 

International Conference on Root and Butt Rots; 1993 

August 9-16; Wik, Sweden and Haikko, Finland. Uppsala, 

Sweden: Swedish University of Agricultural Sciences: 606-

617.

32. Hagle, S. K., S. Tunnock, K. E. Gibson, and C. J. Gilligan. 

1987. Field Guide to Diseases and Insect Pests of Idaho and 

Montana Forests. USDA Forest Service, Northern Region. 

123 p.

33. Hawksworth, F. G. 1961. Dwarf mistletoe of ponderosa 

pine in the Southwest. Tech. Bull. 1246. USDA, Forest 

Service, Rocky Mountain Forest and Range Experiment 

Station. 13 p.

34. Hawksworth, F. G., and B. W. Geils. 1990. How long do 

mistletoe-infected ponderosa pines live? Western Journal of 

Applied Forestry. 5(2): 47-48.

35. Hawksworth, F. G. and R. F. Scharpf. 1981. Phoradendron 

on conifers. USDA Forest Service, Forest Pest Leaflet 164. 

7p.

36. Hedlin, A. F., H. O. Yates, D. C. Tovar, B. H. Ebel, T.W. 

Koerber, and E. P. Merkel. 1980. Cone and Seed Insects of 

North American Conifers. Canadian Forestry Service. 122 

p.

37. Hessburg, P. F., D. J. Goheen, and R. V. Bega. 1995. Black 

stain root disease of conifers. Forest Insect and Disease 

Leaflet 145 (rev.). USDA Forest Service. 10 p.
237

38. Hinds, T. E. 1985. Diseases. In: DeByle, N. V., Winokur, 

R. P., eds. Aspen: Ecology and Management in Western 

United States. Tech. Rep. RM-119. Fort Collins, CO: 

USDA Forest Service, Rocky Mountain Forest and Range 

Experiment Station: 87-106.

39. Hinds, T. E. and M. G. Ryan. 1985. Expansion of sootybark and ceratocystis cankers on aspen. Plant Disease 

69:842-844.

40. Holsten, E. H., P. E. Hennon, L. Trummer, and M. Schultz. 

2001. Insects and Diseases of Alaskan Forests. USDA 

Forest Service, Alaska Region, R10-TP-87. 242 p.

41. Holsten, E. H., R. W. Their, A. S. Munson, and K. E. Gibson. 

1999. The spruce beetle. USDA Forest Service, Forest 

Insect & Disease Leaflet 127. 12 p.

42. Itami, J. K. and T. P. Craig. 1989. Life history of 

Styloxus bicolor (Coleoptera: Cerambycidae) on 

Juniperus monosperma in northern Arizona. Annals of the 

Entomological Society of America 82: 582-587.

43. Jennings, D. T. and R. E. Stevens. 1982. Southwestern pine 

tip moth. USDA Forest Service, Forest Insect and Disease 

Leaflet 58. 7 p.

44. Johnson, D. W., J. S. Beatty, and T. E. Hinds. 1995. Cankers 

on western quaking aspen. USDA Forest Service, Forest 

Pest Leaflet 152. 9 p.

45. Johnson W. T. and H. H. Lyon, 1988. Insects that feed on 

trees and shrubs, 2nd ed. Cornell University Press, Ithaca, 

NY. 556 p.

46. Kanaskie, A., J. Chetock, G. Irwin, D. Overhulser. 1990. 

Black bear damage to forest trees in northwest Oregon 1988-

1989, Pest Management Report 90-1, Oregon Department of 

Forestry, Salem, OR.
238

47. Keen, F. P. 1958. Cone and seed insects of western forest 

trees. USDA Forest Service, California Forest and Range 

Exp. Stn. Tech. Bull. 1169. 169 p.

48. Kegley, S. J., R. L. Livingston, and K. E. Gibson. 1997. 

Pine engraver, Ips pini (Say), in the western United States. 

USDA Forest Service, Forest Insect and Disease Leaflet 122. 

7 p.

49. Kimball, B. A., D. L. Nolte, D. L. Griffin, S. M. Dutton 

and S. Ferguson. 1998. Impacts of live canopy pruning on 

the chemical constituents of Douglas-fir vascular tissues: 

implications for black bear tree selection. Forest Ecology 

and Management. 109(1-3):51-56.

50. Linnane, J. P., comp. 1984. Annual Southwestern Region 

pest conditions report-1983. USDA Forest Service, 

Southwestern Region. Albuquerque, NM. R3 84-13. 13 p.

51. Lightle, P. C. and S. R. Andrews. 1968. Red rot in residual 

ponderosa pine stands on the Navajo Indian Reservation. 

USDA Forest Service, Rocky Mountain Research Station. 

Res. Pap. RM-37. 12 p.

52. Livingston, R. L. 1979. The pine engraver beetle in Idaho, 

life history, habits and management recommendations. 

Idaho Department of Lands, Forest Insect and Disease 

Control Report 79-3. 7 p.

53. Livingston, W. H., A. C. Mangini, H. G. Kinzer, and M. E. 

Mielke. 1983. Association of root diseases and bark beetles 

(Coleoptera: Scolytidae) with Pinus ponderosa in New 

Mexico. Plant Disease 67: 674-676.

54. Lynch, A. M. 2003. Spruce aphid in high elevation habitats 

in the Southwest. p. 60-63. In: S. L. C. Gosbroke, K.W. 

Gottschalk, editors, Proceedings of the USDA interagency 

research forum on gypsy moth and other invasive species, 

2002. USDA Forest Service, GTR-NE-300. 
239

55. Lynch, A. M. 2004. Fate and characteristics of Picea 

damaged by Elatobium abietinum (Walker) (Homoptera: 

Aphididae) in the White Mountains of Arizona. Western 

North American Naturalist. 7-17.

56. Lynch, A. M. and Fitzgibbon, R. A. 2005. Biology and 

impact of Nepytia janetae in spruce-fir forests in Arizona, 

USA, submitted for publication.

57. Lynch, A. M., J. L. Wilson, and M. S. Frank. In press. 

Elatobium abietinum (Walker) populations reach 

epidemic levels on Picea engelmannii Parry in the interior 

southwestern United States. Journal of Agricultural and 

Forest Entomology.

58. Maffei, H., and J. Beatty. 1988. Changes in the incidence 

of dwarf mistletoe over 30 years in the Southwest. Van der 

Kamp, B. J. ed., Proceedings 36th Western International 

Forest Disease Work Conference; 1988 September 19-

23; Park City, UT. Vancouver, BC: University of British 

Columbia: 88-90.

59. Maijala, P., T. C. Harrington, and M. Raudaskoski. 2003. A 

peroxidase gene family and gene tree in Heterobasidion and 

related genera. Mycologia 95:209-221.

60. Massey, C. L., Lucht, D. D., and J. M. Schmid. 1977. 

Roundheaded pine beetle. USDA Forest Service, Forest 

Insect and Disease Leaflet 155. 8 p.

61. Massey, C. L., and D. L. Parker. 1981. Arizona five-spined 

ips. USDA Forest Service, Forest Insect and Disease Leaflet 

116. 6 p.

62. McCambridge, W. F. 1974. Pinyon needle scale. USDA 

Forest Service, Forest Insect and Disease Leaflet 148. 3 p.

63. McGregor, M. D., and L. O. Sandin. 1969. Pinyon sawfly, 

Neodiprion edulicolis Ross. USDA Forest Service, Forest 

Insect and Disease Leaflet 117. 10 p.
240

64. McMillin, J. D., K. E. Allen, D. F. Long, J. L. Harris and 

J. F. Negrón. 2003. Effects of western balsam bark beetle 

on spruce-fir forests of north-central Wyoming. Western 

Journal of Applied Forestry 18: 259-266.

65. McMillin, J. D., G. Hengxiao, M. R. Wagner & X. Long. 

1996. Host density and elevation effects on the spatial 

distribution patterns of pine sawflies in eastern Arizona and 

southwestern China. Forest Ecology and Management 86: 

151–161.

66. McMillin, J. D., and M. R. Wagner. 1989. Assessing the 

impacts of foliage-feeding insects on timber and scenic 

beauty of ponderosa pine: a methodological approach. p. 

51–59. In: (A. Tecle, W. W. Covington & R. H. Hamre, 

tech. coor.) Multiresource Management of Ponderosa Pine 

Forests. USDA Forest Service GTR RM–185. 

67. McMillin, J. D. and M. R. Wagner. 1993. Influence of 

stand characteristics and site quality on sawfly population 

dynamics. p. 333–361. In: (M. R. Wagner & K. F. Raffa, 

eds.) Sawfly Life History Adaptations to Woody Plants. 

Academic Press, Orlando, FL.

68. McMillin, J. D. and M. R. Wagner. 1997. Chronic 

defoliation impacts pine sawfly (Hymenoptera: Diprionidae) 

performance and host plant quality. Oikos 79: 357–362.

69. McMillin, J. D. and M. R. Wagner. 1998. Influence of 

host plant versus natural enemies on the spatial distribution 

of a pine sawfly, Neodiprion autumnalis (Hymenoptera: 

Diprionidae). Ecological Entomology 23: 397–408.

70. Mielke, J. L. 1943. White pine blister rust in western North 

America. Yale Univ. School of Forestry. Bulletin No. 52. 

155 p.

71. Millar, C. S. 1984. Lophodermella species on pines. p. 

45-55. In: Recent Research on Conifer Needle Diseases. 
241

Ed. Glenn W. Peterson. USDA Forest Service, General 

Technical Report GTR-WO 50.

72. Niwa, C G., R. E. Sandquist and 19 others. 2001. 

Invertebrates of the Columbia River basin assessment area. 

(T. M. Quigley, Ed.) Interior Columbia Basin Ecosystem 

Management Project: Scientific Assessment. USDA Forest 

Service, General Technical Report PNW-GTR-512, Portland, 

OR. 74 p.

73. Otrosina, W. J.; Scharpf, R. F., technical coordinators. 

1989. Proceedings of the Symposium on Research and 

Management of Annosus Root Disease (Heterobasidion 

annosum) in Western North America; April 18-21, 1989; 

Monterey, CA. Gen. Tech. Rep. PSW-116. Berkeley, CA: 

Pacific Southwest Forest and Range Experiment Station, 

USDA Forest Service. 177 p.

74. Parker, D. L. 1980. Mountain pine beetle, Dendroctonus 

ponderosae Hopkins, in ponderosa pine, Kaibab Plateau, 

Arizona. USDA Forest Service, Southwestern Region, 

Integrated Pest Management Guide 80-8. 12 p.

75. Parker, D. L. 1991. Integrated pest management guide: 

Arizona five-spined ips, Ips lecontei Swaine, and pine 

engraver, Ips pini (Say), in ponderosa pine. USDA Forest 

Service, Southwestern Region, 91-8. 17 p.

76. Parmeter, J. R., Jr. 1978. Forest stand dynamics and 

ecological factors in relation to dwarf mistletoe spread, 

impact, and control. p. 16-30. In: Proceedings of the 

Symposium on Dwarf Mistletoe Control Through Forest 

Management. Robert F. Scharpf and John R. Parmeter, Jr., 

Tech. Coords., April 11-13, 1978, Berkeley, CA: USDA 

Forest Service, General Technical Report PSW-31. 190 p.

77. Peterson, Glenn W. 1982. Dothistroma needle blight of 

pines. USDA Forest Service. Forest Pest Leaflet 143. 6 p. 
242

78. Peterson, R. S. 1967. Studies of juniper rusts in the West. 

Madroño 19:79-91.

79. Peterson, R. S. 1968. Limb rust of pine: the causal fungi. 

Phytopathology 58: 309-315.

80. Rindge, F. H. 1967. A new species of Nepytia from the 

southern Rocky Mountains. New York Entomological 

Society LXXV: 74-76.

81. Schalau, J. 2003. Cypress bark beetles. The University 

of Arizona College of Agriculture and Life Sciences 

Publication AZ1316. 2 p.

82. Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific 

Coast Conifers. Agricultural Handbook 521. Washington, 

DC, USDA Forest Service. 199 p.

83. Scharpf, R. F., and R. V. Bega. 1981. Elytroderma disease 

reduces growth and vigor, increases mortality of jeffery pines 

at Lake Tahoe Basin, California. USDA Forest Service. 

PSW-155. 6 p.

84. Scharpf, R. F., and Hawksworth, F. G. 1974. Mistletoes 

on hardwoods in the United States. USDA Forest Service, 

Forest Pest Leaflet 147. 7 p.

85. Schmid, J. M., and D. D. Bennett. 1988. The North Kaibab 

Pandora Moth Outbreak, 1978-1984. USDA Forest Service, 

GTR-RM-153, 19 p.

86. Schmid, J. M. and R. H. Frye. 1977. Spruce beetle in the 

Rockies. USDA Forest Service, Rocky Mountain Forest and 

Range Experiment Station, General Technical Report RM49. 38 p.

87. Schmid, J. M, J. C. Mitchell, K. D. Carlin, and M. R. 

Wagner. 1984. Insect damage, cone dimensions, and seed 

production in crown levels of ponderosa pine. Great Basin 

Naturalist: 575-578.
243

88. Schmitt, C. L., J. R. Parmeter, and J. T. Kliejunas. 2000. 

Annosus root disease of western conifers. USDA Forest 

Service, Forest Pest Leaflet 172. 10 p.

89. Schmitz, R. F. and Gibson, K. E. 1996. Douglas-fir beetle. 

USDA Forest Service, Forest Insect and Disease Leaflet 5. 8 

p. 

90. Shaw, C. G., III and G. A. Kile. 1991. Armillaria Root 

Disease. USDA Forest Service, Agriculture Handbook No. 

691. 233 p.

91. Shepperd, Wayne D. and Fairweather, M. L. 1994. Impact 

of large ungulates in restoration of aspen communities in 

a southwestern ponderosa pine ecosystem. In: Covington, 

W. Wallace; DeBano, Leonard F.; tech. coords. Sustainable 

Ecological Systems: Implementing an Ecological Approach 

to Land Management. 1993 July 12-15; Flagstaff, Arizona. 

GTR-RM-247. Fort Collins, CO: USDA, Forest Service, 

Rocky Mountain Forest and Range Experiment Station.

92. Sinclair, W. A., H. H. Lyon, and W. T. Johnson. 1987. 

Diseases of Trees and Shrubs. Cornell University Press. 574 

p.

93. Smith, A. A. 1992. Identification of Distinguishing 

Characteristics Around Middens of Mount Graham Red 

Squirrels. Thesis submitted to the faculty of the School of 

Renewable Natural Resources, University of Arizona. 78 p.

94. Smith, R. H. Red turpentine beetle. USDA Forest Service, 

Forest Insect and Disease Leaflet 55. 9 p.

95. Sower, L. L., G. E. Daterman, and C. Sartwell. 1989. 

Biology and impact of western pine shoot borer, Eucosma 

sonomana, in the western United States. p. 102-109. In: 

Proceedings of the IUFRO working group on Insects 

Affecting Reforestation, XVIII International Congress of 

Entomology, 1988. Vancouver, British Columbia, Canada. 
244

96. Stevens, R. E., J. W. Brewer, and D. T. Jennings. 1978. Life 

history and habits of Coleotechnites edulicola (Gelechiidas) 

a piñon needle miner in the Southwest. Journal of the 

Lepidopterists Society. 32(2): 123-129.

97. Stevens, R. E. and D. T. Jennings. 1977. Western pine shoot 

borer: A threat to intensive management of ponderosa pine 

in the Rocky Mountain area and the Southwest. USDA 

Forest Service, GTR-RM 45. 8 p.

98. Swetnam, T. W., and A. M. Lynch. 1989. A tree-ring 

reconstruction of western spruce budworm in the southern 

Rocky Mountains. Forest Science. 35(4):962-986.

99. Swetnam, T. W. and A. M. Lynch. 1993. Multicentury, 

regional-scale patterns of western spruce budworm 

outbreaks. Ecological Monographs. 63(4):399-424.

100. Tainter, F. H. and F. A. Baker. 1996. Principles of Forest 

Pathology. John Wiley & Sons, Inc. 805 p.

101. Tinnin, R. O. 1984. The effect of dwarf mistletoe on forest 

community ecology. p. 117-122. In: Frank G. Hawksworth 

and Robert F. Scharpf, Tech. Coords., Biology of Dwarf 

Mistletoes: Proceeding of the Symposium,1984. USDA 

Forest Service, GTR-RM-111.

102. Tkacz, B. M. 1991. Survival of Inonotus tomentosus in 

spruce stumps after logging. Plant Disease 75(8): 788-790.

103. USDA Forest Service. 1985. Insects and diseases of trees in 

the South. USDA Forest Service, GTR-R8-5. 98 p.

104. USDA Forest Service. 1986. Tiger moth. USDA Forest 

Service, Southwestern Region, Fact Sheet. 2 p.

105. USDA Forest Service. 2002. Forest insect and disease 

conditions in the Southwestern Region, 2001. USDA Forest 

Service, Southwestern Region. Albuquerque, NM. R3-02-

01. 17 p.
245

106. Van Arsdel, E. P., and B. W. Geils. 2004. The Ribes of 

Colorado and New Mexico and their rust fungi. FHTET-04-

13. Fort Collins, CO: USDA Forest Service, Forest Health 

Technology Enterprise Team. 32 p.

107. Vasiloff, S. 1997. Microburst prediction and detection. 

N.O.A.A. Western Region Technical Attachment. No. 97-21. 

2 p.

108. Wagner, M. R. 2001. Insects and diseases of southwestern 

forests. Lecture notes compiled by Michael R. Wagner, 

Northern Arizona University. 159 p.

109. Washburn, R. I. and M. D. McGregor. 1974. White fir 

needle miner. USDA Forest Service, Forest Pest Leaflet 144, 

5 p.

110. Whitney, R. D. 1977. Polyporus tomentosus root rot of 

conifers. Forestry Technical Report No. 18. Canadian 

Forestry Service; 12 p.

111. Wickman, B. E., R. R. Mason, and G. C. Trostle. 1981. 

Douglas-fir tussock moth. USDA Forest Service, Forest 

Insect and Disease Leaflet 86. 10 p.

112. Williams, R. E., C. G. Shaw, III, P. M. Wargo, and W. 

H. Sites. 1989. Armillaria Root Disease. USDA Forest 

Service, Forest Insect and Disease Leaflet 78 (rev.). 8 p. 

113. Wilson, J. L. and A. M. Lynch. 1998. Spruce aphid in the 

Southwest. USDA Forest Service, Southwestern Region.

114. Wood, R. E. 1983. Mortality caused by root diseases and 

associated pests on six national forests in Arizona and New 

Mexico. USDA Forest Service, Southwestern Region, 

Albuquerque, New Mexico. R-3 83-13. 31 p. 

115. Wood, S. L. 1982. The bark and ambrosia beetles of North 

and Central America (Coleoptera: Scolytidae), a taxonomic 

monograph. Great Basin Naturalist Memoirs. Number 6. 

1359 p.
246

116. Yohem, K. H., G. B. Cummins, and R. L. Gilbertson. 

1985. Revised list and host index of Arizona rust fungi. 

Mycotaxon. 23(2): 451-468.

117. Zabel, R. A. and J. J. Morrell. 1992. Wood Microbiology: 

Decay and Its Prevention. Academic Press, Inc. 476 p.
247

Host Index

Abies concolor—white fir

Branches & Terminals

 True Fir Dwarf Mistletoe Arceuthobium abietinum . . . . . 177

 White Fir True Mistletoe Phoradendron pauciflorum. . . . 184

Foliage

 Douglas-Fir Tussock Moth Orgyia pseudotsugae. . . . . . . . 11

 New Mexico Fir Looper Galenara consimilus. . . . . . . . . . 26

 True Fir Needle Cast Lirula abietis-concoloris. . . . . . . . . 128

 Western Spruce Budworm Choristoneura occidentalis . . . . 8

 White Fir Needleminer Epinotia meritana. . . . . . . . . . . . . . 16

Roots

 Annosus Root Rot Heterobasidion annosum . . . . . . . . . . 193

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Fir Engraver Scolytus ventralis. . . . . . . . . . . . . . . . . . . 81

 Decays

 Indian Paint Fungus Echinodontium tinctorium. . . . . 138

 Red Ring Rot Phellinus pini. . . . . . . . . . . . . . . . . . . . 134

 Other

 Carpenter Ants Camponotus spp.. . . . . . . . . . . . . . . . 109

 Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

 Rusts

 Fir Broom Rust 

 Melampsorella caryophyllacearum. . . . . . . . . . . . . . 171

Abies lasiocarpa—subalpine fir

Branches & Terminals

 Douglas-Fir Dwarf Mistletoe Arceuthobium douglasii . . .177

Foliage

 Nepytia janetae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Roots

 Annosus Root Rot Heterobasidion annosum . . . . . . . . . . 193

 Armillaria or Shoestring Root Rot Armillaria Spp. . . . . . 191
248

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Western Balsam Bark Beetle Dryocoetes confusus. . . 79

 Decays

 Indian Paint Fungus Echinodontium tinctorium. . . . . 138

 Rusts

 Fir Broom Rust Melampsorella 

 caryophyllacearum. . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Acacia spp.—acacia

Branches & Terminals

 Desert Mistletoe Phoradendron californicum. . . . . . . . . . 184

Acer spp.—maple

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Alnus tenuifolia—thinleaf alder

Foliage

 Alder Flea Beetle Altica ambiens. . . . . . . . . . . . . . . . . . . . 35

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

Stem

 Cankers

 Cytospora Canker Cytospora chrysosperma . . . . . . . 152

Aphrophora spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Arbutus arizonica—Arizona madrone

Foliage

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

Cercidium spp.—palo verde

Branches & Terminals

 Desert Mistletoe Phoradendron californicum. . . . . . . . . . 184
249

Cercocarpus spp.—mountain mahogany

Foliage

 Western Tent Caterpillars Malacosoma californicum. . . . . 31

Clastoptera spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Cupressus Arizonica—Arizona cypress

Branchea & Terminals

 Cedar Bark Beetles Phloeosinus spp.. . . . . . . . . . . . . . . . . . 85

 Dense Mistletoe Phoradendron densum. . . . . . . . . . . . . . 184

 Juniper Twig Pruner Styloxus Bicolor. . . . . . . . . . . . . . . . 107

Stem

 Bark Beetles & Wood Borers

 Juniper Borers Trachykele blondeli, etc.. . . . . . . . . . . . 90

Rusts

 Gymnosporangium Rusts Gymnosporangium spp.. . . . . . 169

Fraxinus spp.—ash

Branches & Terminals

 Big Leaf Mistletoe Phoradendron macrophyllum. . . . . . . 184

Foliage

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

Juglans major—Arizona walnut

Branches & Terminals

 Big Leaf Mistletoe Phoradendron macrophyllum. . . . . . . 184

Juniperus osteosperma—Utah Juniper, J. deppeana—alligator 

juniper, J. monosperma—one-seed juniper, J. scopulorum—

rocky mountain juniper

Branches & Terminals

 Cedar Bark Beetles Phloeosinus spp.. . . . . . . . . . . . . . . . . . 85

 Juniper Mistletoe Phoradendron juniperinum. . . . . . . . . . 184

 Juniper Twig Pruner Styloxus Bicolor. . . . . . . . . . . . . . . . 107
250

Foliage

 Spider Mites Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . 54

 Spittlebugs Aphrophora spp., Clastoptera spp.. . . . . . . . . . 53

Stem

 Bark Beetles & Wood Borers

 Juniper Borers Trachykele blondeli, etc.. . . . . . . . . . . . 90

Rusts

 Gymnosporangium Rusts Gymnosporangium spp.. . . . . . 169

Picea engelmannii—Engelmann spruce

Branches & Terminals

 Western Spruce Dwarf 

 Mistletoe Arceuthobium microcarpum . . . . . . . . . . . . . . . 177

Foliage

 Cooley Spruce Gall Adelgid Adelges cooleyi. . . . . . . . . . . 40

 Frost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

 Nepytia janetae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

 Pine Needle Scale Chionaspis pinifoliae. . . . . . . . . . . . . . . 49

 Spruce Aphid Elatobium abietinum. . . . . . . . . . . . . . . . . . . 42

 Western Spruce Budworm Choristoneura occidentalis . . . . 8

Roots

 Armillaria or Shoestring Root Rot Armillaria spp.. . . . . . 191

 Schweinitzii Root and Butt Rot Phaeolus schweinitzii. . . 198

 Tomentosus Root Disease Inonotus tomentosus. . . . . . . . . 196

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Spruce Beetle Dendroctonus rufipennis. . . . . . . . . . . . 74

Decays

 Indian Paint Fungus Echinodontium tinctorium. . . . . . . . . 138

 Red Ring Rot Phellinus pini. . . . . . . . . . . . . . . . . . . . . . . 134

Rusts

 Spruce Broom Rust Chrysomyxa arctostaphyli. . . . . . . . . 171
251

Picea pungens—Colorado blue spruce

Branches & Terminals

 Western Spruce Dwarf 

 Mistletoe Arceuthobium microcarpum . . . . . . . . . . . . . . . 177

Foliage

 Cooley Spruce Gall Adelgid Adelges cooleyi. . . . . . . . . . . 40

 Douglas-Fir Tussock Moth Orgyia pseudotsugae. . . . . . . . 11

 Frost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

 Pine Needle Scale Chionaspis pinifoliae. . . . . . . . . . . . . . . 49

 Spruce Aphid Elatobium abietinum. . . . . . . . . . . . . . . . . . . 42

 Western Spruce Budworm Choristoneura occidentalis . . . . 8

Roots

 Armillaria or Shoestring Root Rot Armillaria spp.. . . . . . 191

 Schweinitzii Root and Butt Rot Phaeolus schweinitzi. . . . 198

 Tomentosus Root Disease Inonotus tomentosus. . . . . . . . . 196

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Spruce Beetle Dendroctonus rufipennis. . . . . . . . . . . . 74

Decays

 Red Ring Rot Phellinus pini. . . . . . . . . . . . . . . . . . . . . . . 134

Rusts

 Spruce Broom Rust Chrysomyxa arctostaphyli. . . . . . . . . 171

Pinus aristata—bristlecone pine

Branches & Terminals

 Western Spruce Dwarf 

 Mistletoe Arceuthobium microcarpum . . . . . . . . . . . . . . . 177

Pinus edulis—piñon, P. monophylla—singleleaf piñon, P. 

cembroides—Mexican piñon

Branches & Terminals

 Bark Moths Dioryctria spp.. . . . . . . . . . . . . . . . . . . . . . . . 106

 Pinyon Dwarf Mistletoe Arceuthobium divaricatum. . . . . 177

 Pinyon Pitch Nodule Moth Petrova arizonensis. . . . . . . . 105
252

 Pitch Moth Synanthedon spp. . . . . . . . . . . . . . . . . . . . . . . 106

 Twig Beetles Pityophthorus spp., Pityogenes spp., 

 Pityoborus secundus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Foliage

 Drought. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

 Elytroderma Needle Cast Elytroderma deformans. . . . . . 123

Pine Sawflies Neodiprion Spp., Zadiprion spp.. . . . . . . . . . 22

 Pine-Feeding Needleminers Coleotechnites spp. . . . . . . . . 14

 Pinyon Needle Scale Matsucoccus acalyptus. . . . . . . . . . . 44

 Pinyon Spindle Gall Midge Pinyinia edulicola. . . . . . . . . . 52

 Red Band Needle Blight Dothistroma septospora . . . . . . 125

 Spider Mites Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . 54

 Tiger Moth Lophocampa ingens. . . . . . . . . . . . . . . . . . . . . . 24

Roots

 Black Stain Root Disease Leptographium wageneri. . . . . 200

Stem

 Bark Beetles & Wood Borers

 Pine Engravers Ips spp. . . . . . . . . . . . . . . . . . . . . . . . . 59

 Wood Borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Decays

 Red Rot Dichomitus squalens. . . . . . . . . . . . . . . . . . . . . . 136

Pinus eldarica—Mondel pine

Stem

 Rusts

 Comandra Blister Rust Cronartium comandrae. . . . . 167

Pinus engelmannii—Apache pine

Branches & Terminals

 Southwestern Dwarf Mistletoe Arceuthobium

 vaginatum subsp. cryptopodum. . . . . . . . . . . . . . . . . . . . . 177

Stem

 Bark Beetles & Wood Borers

 Southern Pine Beetle Dendroctonus frontalis. . . . . . . . 70
253

Pinus flexilis—limber pine

Branches & Terminals

 Limber Pine Dwarf Mistletoe 

 Arceuthobium cyanocarpum. . . . . . . . . . . . . . . . . . . . . . . 177

Stem

 Bark Beetles & Wood Borers

 Mountain Pine Beetle Dendroctonus ponderosae . . . . 65

 Red Turpentine Beetle Dendroctonus valens. . . . . . . . 72

 Cankers

 Atropellis Canker Atropellis piniphila. . . . . . . . . . . . . 158

Pinus leiophylla var. chihuahuana—Chihuahua pine

Branches & Terminals

 Chihuahua Pine Dwarf Mistletoe Arceuthobium gillii. . . . 177

Cones & Seeds

 Southwestern Cone Rust Cronartium conigenum. . . . . . . 175

Stem

 Bark Beetles & Wood Borers

 Southern Pine Beetle Dendroctonus frontalis. . . . . . . . 70

Pinus ponderosa var. arizonica—Arizona pine

Branches & Terminals

 Southwestern Dwarf Mistletoe Arceuthobium 

 vaginatum subsp. cryptopodum. . . . . . . . . . . . . . . . . . . . . 177

Pinus ponderosa—ponderosa pine

Branches & Terminals

 Bark Moths Dioryctria spp.. . . . . . . . . . . . . . . . . . . . . . . . 106

 Pine Tip Moths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

 Pitch Moth Synanthedon spp. . . . . . . . . . . . . . . . . . . . . . . 106

 Southwestern Dwarf Mistletoe Arceuthobium 

 vaginatum subsp. cryptopodum. . . . . . . . . . . . . . . . . . . . . 177

 Twig Beetles Pityophthorus spp., Pityogenes spp., 

 Pityoborus secundus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

 Western Pineshoot Borer Eucosma sonomana . . . . . . . . . 103
254

Cones & Seeds

 Cone Beetles Conophthorus spp.. . . . . . . . . . . . . . . . . . . . . 95

 Pine Coneworm Dioryctria auranticella. . . . . . . . . . . . . . . 99

 Pine Seed Chalcid Megastigmus albifrons. . . . . . . . . . . . . . 98

 Ponderosa Pine Seedworm Cydia piperana . . . . . . . . . . . . 97

Foliage

 Aphids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

 Drought. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

 Elytroderma Needle Cast Elytroderma deformans. . . . . . 123

 Lophodermella Needle Cast Lophodermella cerina. . . . . 121

 Pandora Moth Coloradia pandora . . . . . . . . . . . . . . . . . . . 18

Pine Butterfly Neophasia menapia. . . . . . . . . . . . . . . . . . . 20

 Pine Needle Scale Chionaspis pinifoliae. . . . . . . . . . . . . . . 49

Pine Sawflies Neodiprion spp., Zadiprion spp.. . . . . . . . . . 22

 Pine-Feeding Needleminers Coleotechnites spp. . . . . . . . . 14

 Ponderosa Pine Resin Midge Cecidomyia piniinopis. . . . . . 50

 Prescott Scale Matsucoccus vexillorum. . . . . . . . . . . . . . . . 46

 Red Band Needle Blight Dothistroma septospora . . . . . . 125

 Red Belt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

 Salt Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

 Spider Mites Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . 54

 Tiger Moth Lophocampa ingens. . . . . . . . . . . . . . . . . . . . . . 24

 Winter Injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Roots

 Annosus Root Rot Heterobasidion annosum . . . . . . . . . . 193

 Armillaria or Shoestring Root Rot Armillaria spp.. . . . . . 191

 Schweinitzii Root and Butt Rot Phaeolus schweinitzii. . . 198

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Mexican Pine Beetle Dendroctonus mexicanus. . . . . . 70

 Mountain Pine Beetle Dendroctonus ponderosae . . . . 65

 Pine Engravers Ips spp. . . . . . . . . . . . . . . . . . . . . . . . . 59

 Red Turpentine Beetle Dendroctonus valens. . . . . . . . 72

 Roundheaded Pine Beetle Dendroctonus adjunctus. . . 67
255

 Western Pine Beetle Dendroctonus brevicomis. . . . . . 63

 Wood Borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

 Cankers

 Atropellis Canker Atropellis piniphila. . . . . . . . . . . . . 158

Decays

 Pouch Fungus Cryptoporus volvatus. . . . . . . . . . . . . . . . . 142

 Red Rot Dichomitus squalens. . . . . . . . . . . . . . . . . . . . . . 136

Other

 Carpenter Ants Camponotus spp. . . . . . . . . . . . . . . . . . . . 109

 Termites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Rusts

 Comandra Blister Rust Cronartium comandrae. . . . . . . . . 167

 Limb Rust Cronartium arizonicum. . . . . . . . . . . . . . . . . . 164

 Western Gall Rust Peridermium harknessii . . . . . . . . . . . 166

Pinus strobiformis—southwestern white pine

Branches & Terminals

 Apache Dwarf Mistletoe Arceuthobium apachecum. . . . . 177

Foliage

 White Pine Needle Cast Lophodermella arcuata . . . . . . . 129

Roots

 Schweinitzii Root and Butt Rot Phaeolus schweinitzii. . . 198

Stem

 Bark Beetles & Wood Borers

 Mountain Pine Beetle Dendroctonus ponderosae . . . . 65

 Red Turpentine Beetle Dendroctonus valens. . . . . . . . 72

 Cankers

 Atropellis Canker Atropellis piniphila. . . . . . . . . . . . . 158

Rusts

 White Pine Blister Rust Cronartium ribicola. . . . . . . . . . 161

Platanus wrightii—Arizona sycamore

Branches & Terminals

 Big Leaf Mistletoe Phoradendron macrophyllum. . . . . . . 184

Foliage

 Sycamore Anthracnose Apiognomonia veneta . . . . . . . . . 118
256

Polyporus anceps... . . . . . . . . . . . . . . . . See Dichomitus squalens

Populus spp.—cottonwood

Branches & Terminals

 Big Leaf Mistletoe Phoradendron macrophyllum. . . . . . . 184

Foliage

 Aphids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

 Black Leaf Spot Marssonina populi. . . . . . . . . . . . . . . . . 114

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

 Ink Spot Leaf Blight Ciborinia whetzelii . . . . . . . . . . . . . 115

 Melampsora Rust Melampsora spp. . . . . . . . . . . . . . . . . . 116

 Shepherd’s Crook Venturia spp.. . . . . . . . . . . . . . . . . . . . . 117

 Western Tent Caterpillars Malacosoma californicum. . . . . 31

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Cankers

 Cytospora Canker Cytospora chrysosperma . . . . . . . 152

Populus tremuloides—aspen

Foliage

 Black Leaf Spot Marssonina populi. . . . . . . . . . . . . . . . . 114

 Drought. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

 Frost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

 Ink Spot Leaf Blight Ciborinia whetzelii . . . . . . . . . . . . . 115

 Large Aspen Tortrix Choristoneura conflictana. . . . . . . . . . 33

 Melampsora Rust Melampsora spp. . . . . . . . . . . . . . . . . . 116

 Shepherd’s Crook Venturia spp.. . . . . . . . . . . . . . . . . . . . . 117

 Spider Mites Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . 54

 Western Tent Caterpillars Malacosoma californicum. . . . . 31

Roots

 Ganoderma Root Rot Ganoderma applanatum. . . . . . . . . 202

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Wood Borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
257

 Cankers

 Black Canker Ceratocystis fimbriata. . . . . . . . . . . . . 148

 Cryptosphaeria Canker Cryptosphaeria lignyota. . . . 154

 Cytospora Canker Cytospora chrysosperma . . . . . . . 152

 Hypoxylon Canker Hypoxylon mamatum. . . . . . . . . . 156

 Sooty Bark Canker Encoelia pruinosa. . . . . . . . . . . . 150

 Decays

 False Tinder Conk Phellinus tremulae. . . . . . . . . . . . 144

 Red Belt Fungus Fomitopsis pinicola. . . . . . . . . . . . . 140

Prosopis spp.—mesquite

Branches & Terminals

Desert Mistletoe Phoradendron californicum. . . . . . . . . . . . . . . . 184

Prunus virginiana vars. demissa and 

melancocarpa—common chokecherry

Foliage

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

Pseudotsuga menziesii—Douglas-fir

Branches & Terminals

 Douglas-Fir Dwarf Mistletoe Arceuthobium douglasii. . . 177

Foliage

 Cooley Spruce Gall Adelgid Adelges cooleyi. . . . . . . . . . . 40

 Douglas-Fir Tussock Moth Orgyia pseudotsugae. . . . . . . . 11

 Melampsora Rust Melampsora spp. . . . . . . . . . . . . . . . . . 116

 New Mexico Fir Looper Galenara consimilus. . . . . . . . . . 26

 Pine Needle Scale Chionaspis pinifoliae. . . . . . . . . . . . . . . 49

 Rhabdocline Needle Cast Rhabdocline spp.. . . . . . . . . . . 126

 Western Spruce Budworm Choristoneura occidentalis . . . . 8

Roots

 Armillaria or Shoestring Root Rot Armillaria spp.. . . . . . 191

 Black Stain Root Disease Leptographium wageneri. . . . . 200

 Schweinitzii Root and Butt Rot Phaeolus schweinitzii 198

 Tomentosus Root Disease Inonotus tomentosus. . . . . . . . . 196
258

Stem

 Bark Beetles & Wood Borers

 Ambrosia Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Douglas-Fir Beetle Dendroctonus pseudotsugae. . . . . 77

 Decays

 Indian Paint Fungus Echinodontium tinctorium. . . . . 138

 Pouch Fungus Cryptoporus volvatus. . . . . . . . . . . . . 142

 Red Belt Fungus Fomitopsis pinicola. . . . . . . . . . . . . 140

 Red Ring Rot Phellinus pini. . . . . . . . . . . . . . . . . . . . 134

 Other

 Carpenter Ants Camponotus spp.. . . . . . . . . . . . . . . . 109

 Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Quercus hypoleucoides—silverleaf oak

Cones & Seeds

 Southwestern Cone Rust Cronartium conigenum. . . . . . . 175

Quercus spp.—oak

Branches & Terminals

 Oak Mistletoe Phoradendron coryae. . . . . . . . . . . . . . . . . 184

Foliage

 Frost. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

 Spider Mites Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . 54

 Spittlebugs Aphrophora spp., Clastoptera spp.. . . . . . . . . . 53

Roots

 Armillaria or Shoestring Root Rot Armillaria spp.. . . . . . 191

Stem

 Decays

 Canker Rot of Oak Inonotus andersonii. . . . . . . . . . . 146

 Heart Rots of Oak Inonotus dryophilus. . . . . . . . . . . 145

 Heart Rots of Oak Phellinus everhartii . . . . . . . . . . . 145

Ribes spp.—currants and gooseberries

Foliage

 White Pine Blister Rust Cronartium ribicola. . . . . . . . . . 161
259

Salix spp.—willow

Foliage

 Fall Webworm Hyphantria cunea. . . . . . . . . . . . . . . . . . . . 29

 Melampsora Rust Melampsora spp. . . . . . . . . . . . . . . . . . 116

 Western Tent Caterpillars Malacosoma californicum. . . . . 31

Stem

 Cankers

 Cytospora Canker Cytospora chrysosperma . . . . . . . 152
260

 General Index

A

Abiotic disorders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204-212

Adelgedae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Adelges cooleyi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Adelgid

Cooley Spruce Gall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Alder Flea Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Altica ambiens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Animal Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213-217

Annosus Root Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Aphid

Conifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Hardwoods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Spruce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 42

Aphididae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Apiognomonia veneta. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

Arceuthobium spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

abietinum f. sp. concoloris. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

apachecum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

blumeri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

divaricatum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

douglasii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

gillii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

microcarpu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

vaginatum subsp. cryptopodum. . . . . . . . . . . . . . . . . . . . . 181

Armillaria or Shoestring Root Rot. . . . . . . . . . . . . . . . . . . . . . . . . 191

Armillaria spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Artist’s Conk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Atropellis piniphila. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

B

Beetles, Ambrosia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Beetles, Bark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55-86

Cedar Bark Beetles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Douglas-fir Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Douglas-fir pole beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
261

Fir Engraver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Mountain Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Pine Engravers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Red Turpentine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Roundheaded Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . 67

Scolytus monticolae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

Southern Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

Spruce Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

Western Balsam Bark Beetle. . . . . . . . . . . . . . . . . . . . . . . . 79

Western Pine Beetle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Beetles, Cone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Beetles, Twig . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Black Bear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

Black Stain Root Disease. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

Blue Stain Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Borer

Western Pineshoot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Borers, Juniper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Borers, Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

browse damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Bud Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100-107

Buprestidae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Burls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

C

Camponotus spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Canker Fungi

Atropellis Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

Black Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Cryptosphaeria Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Cytospora. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

Hypoxylon Canker. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

Sooty Bark. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Cankers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147-159

Carpenter Ants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

Cecidomyia piniinopis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
262

Cerambydidae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Ceratocystis fimbriata. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Ceratocystis spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Chionaspis pinifoliae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Choristoneura

conflictana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

occidentalis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Chrysomyxa arctostaphyli. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Ciborinia whetzelii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Clastoptera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Coleotechnites spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Coloradia pandora. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Cone Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94-99

Coneworm, Pine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Conophthorus spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Cow Patty. See Phaeolus schweinitzii

Cronartium

arizonicum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

comandrae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

conigenum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

ribicola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 161

Cryptoporus volvatus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Cryptosphaeria lignyota. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

Cydia piperana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Cytospora Canker

Cytospora chrysosperma. . . . . . . . . . . . . . . . . . . . . . . . . . 152

D

Decay

Root Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189-203

Annosus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Armillaria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

Ganoderma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Schweinitzii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Tomentosus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
263

Stem Decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132-146

False Tinder Conk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Indian Paint Fungus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Oak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

Pouch Fungus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Red Belt Fungus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

Red Ring Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

Red Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Defoliators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-36

Dendroctonus

adjunctus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

brevicomis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

frontalis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

mexicanus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

ponderosae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

pseudotsugae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

rufipennis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

valens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

Dichomitus squalens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

Dioryctria auranticella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Dioryctria spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Dothistroma septospora. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Drought . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

Dryocoetes confusus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

E

Echinodontium tinctorium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Elatobium abietinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 42

Elk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

Elytroderma deformans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Encoelia pruinosa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

Epinotia meritana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Eucosma sonomana. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
264

F

Flatheaded borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Foliar Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113-131

Fomitopsis pinicola. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

Frost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

G

Galenara consimilus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Gall Formers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Ganoderma applanatum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Ganoderma Root Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

Gymnosporangium spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

H

Hemiptera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Heterobasidion annosum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Homoptera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Hyphantria cunea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Hypoxylon mamatum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

I

Inonotus

andersonii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

dryophilus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

tomentosus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

Invasive pests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Ips spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

confusus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

lecontei . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

pini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Isoptera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

J

Juniper Twig Pruner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
265

K

Key to insects and diseases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

L

Large Aspen Tortrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Leaf Disease

Black Leaf Spot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Ink Spot Leaf Blight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Melampsora Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Shepherd’s Crook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Sycamore Anthracnose . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

Leptographium wageneri. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

Lightning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Lirula abietis-concoloris. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Looper

New Mexico Fir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Lophocampa ingens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Lophodermella arcuata. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Lophodermella cerina. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

M

Malacosoma californicum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Marssonina populi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Matsucoccus

acalyptus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

vexillorum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Megastigmus albifrons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Melampsora spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Melampsorella caryophyllacearum. . . . . . . . . . . . . . . . . . . . . . . . 171

Midge

Pinyon Spindle Gall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Ponderosa Pine Resin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Mistletoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176-188

Dwarf Mistletoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

 Apache dwarf mistletoe. . . . . . . . . . . . . . . . . . . . 181

 Blumer’s dwarf mistletoe. . . . . . . . . . . . . . . . . . . 181
266

 Chihuahua pine dwarf mistletoe. . . . . . . . . . . . . . 181

Douglas-fir dwarf mistletoe. . . . . . . . . . . . . . . . . 181

 Pinyon dwarf mistletoe. . . . . . . . . . . . . . . . . . . . . 181

 Southwestern dwarf mistletoe. . . . . . . . . . . . . . . 181

True fir dwarf mistletoe. . . . . . . . . . . . . . . . . . . . . 181

 Western spruce mistletoe. . . . . . . . . . . . . . . . . . . 181

True Mistletoes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

 Bigleaf mistletoe . . . . . . . . . . . . . . . . . . . . . . . . . 187

 Dense mistletoe . . . . . . . . . . . . . . . . . . . . . . . . . . 188

 Desert mistletoe. . . . . . . . . . . . . . . . . . . . . . . . . . 187

 Hairy juniper mistletoe. . . . . . . . . . . . . . . . . . . . . 188

 Juniper mistletoe . . . . . . . . . . . . . . . . . . . . . . . . . 188

 Southwestern oak mistletoe. . . . . . . . . . . . . . . . . 187

 Texas juniper mistletoe. . . . . . . . . . . . . . . . . . . . . 188

White fir true mistletoe. . . . . . . . . . . . . . . . . . . . . 188

Mites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Moth

Bark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Douglas-fir Tussock. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Pandora,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Pine Tip. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Pinyon Pitch Nodule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Tiger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

N

Needle Cast

Elytroderma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Lophodermella. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Red Band Needle Blight (Pine). . . . . . . . . . . . . . . . . . . . . 125

Rhabdocline (Douglas-fir). . . . . . . . . . . . . . . . . . . . . . . . . 126

True Fir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

White Pine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Needle miner

Pine-feeding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

White fir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9, 16
267

Neodiprion spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Neophasia menapia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Nepytia janetae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

New Mexico Fir Looper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Non-infectious disorders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

O

Oligonychus spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Ophiostoma spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Orgyia pseudotsugae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

P

Pandora moth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 21

Peridermium harknessii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

Petrova arizonensis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Phaeolus schweinitzii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Phellinus

everhartii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

pini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

tremulae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Phloeosinus spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Phoradendron spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

californicum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

capitellatum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

coryae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

densum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

hawksworthii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

juniperinum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

macrophyllum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

pauciflorum. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Pine Butterfly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Pinyinia edulicola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Pityoborus secundus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Pityogenes spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Pityophthorus spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Porcupine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
268

R

Red Belt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

Rhabdocline spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Rhyacionia spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Root Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189-203

Roundheaded borers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160-175

Comandra Blister Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Fir Broom Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Gymnosporangium Rusts . . . . . . . . . . . . . . . . . . . . . . . . . 169

Limb Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

Southwestern Cone Rust. . . . . . . . . . . . . . . . . . . . . . . . . . 175

Spruce Broom Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Western Gall Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

White Pine Blister Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . 160

S

Salt Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

Sapsucker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

Sap-Sucking Insects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37-54

Sawflies

Pine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Scale

Pine Needle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Pinyon Needle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Prescott . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Schweinitzii Root and Butt Rot. . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Scolytus ventralis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Seed Chalcid, Pine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

Seed Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94-99

Seedworm

Ponderosa Pine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

Shoot Insects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100-107

Spider Mites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Spittlebugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
269

Stain

Black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

Stains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Stem Decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132-146

Styloxus bicolor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53, 107

Synanthedon spp.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

T

Termites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Tiger moth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Tomentosus Root Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

U

Ungulates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

V

Venturia spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

W

Webworm

Fall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Western Spruce Budworm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Western Tent Caterpillar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

White Pine Blister Rust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 161

Windthrow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

Winter Injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

wood decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133, 191

Z

Zadiprion spp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
270
271