United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Animal Damage

Several higher animal species cause damage to trees. The most

important include porcupines, bears, mountain beavers, pocket

gophers, wood rats, sapsuckers, and deer. Animal feeding

creates injuries that can result in tree death or infection by

wood decay fungi.

Hosts: All trees.

Symptoms: Trunk scars with teeth or claw marks; clipped tops

or branches on seedlings or saplings; holes in tree (woodpeckers and sapsuckers); pocket gopher burrows present in area.

Management: Retardents or protective structures can be

placed on or over seedlings to discourage deer and rodents;

poisonous baits can be used against pocket gophers; snares

and hunting have been used against bears.

May be Confused With: Root diseases, comandra rust.

Bear Damage pn

young Douglas-fir

Sapsucker damage

Porcupine damage on

ponderosa pine
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Stain and decay caused by

Fomes annosus in western hemlock

Fomes annosus conks

in white fire stump

Typical Fomes

annosus conks on

western hemlock

Fomes annosus infection area centered around stump

Forest Disease

Management Notes

Annosus Root and Butt Rot

Annosus root and butt rot is caused by the fungus, Fomes

annosus. Estimates of loss are not available for the Pacific

Northwest. The disease causes growth loss, root and butt rot,

uprooting, and tree killing. Damage is increasing in pine and

true fir stands.

Hosts: All conifers, especially common in western hemlock

and white fir. Damage is seldom seen except in pines, hemlock,

and true firs.

Recognition: Resinous hosts, especially pines, exhibit

decreased terminal growth, needle yellowing, pitch soaking of

root wood, decline, and death; non-resinous hosts exhibit

stain or a white stringy rot in roots and butts; wind-throw may

occur. Rot often has small black specks.

Perennial, flat, button, or bracket-shaped leathery conks in

hollows, crotches, or on root collars of dead trees or stumps,

often below the duff surface; conks are brown to tan with a

lighter colored sterile margin and white pore surface.

Disease Spread: Windborne spores germinate on freshly cut

stump surfaces; the fungus colonizes the stump and roots;

roots of surrounding live trees that are in contact with those of

the stump become infected as well; infection also may occur

through wounds on live trees; tree to tree spread continues

across root grafts and contacts; secondary attack by bark

beetles is common.

Management: Careful logging practices aimed at minimizing

injury to residual trees; removal of severely wounded trees

during stand improvement activities. Short rotations (40-120

years) in western hemlock and true firs will minimize decay

loss. Trees with decay associated with wounds or with root or

butt rot should be treated in recreation areas. When stain or

decay is not present, treat fresh stumps with borax to prevent

infection in recreation areas. Infected stumps could be

removed in high value sites.

May be Confused With: Laminated root rot, Armillaria root rot.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Diagnostic mycelial fan

under bark of Armillaria

mellea-infected tree

Basal resin flow

associated with

Armillaria mellea infection

Armillaria mellea mushrooms

Forest Disease

Management Notes

Armillaria Root Rot

Armillaria root rot, also called shoestring root rot, is caused by

the fungus Armillaria mellea. This is the most common conifer

root rot in the Pacific Northwest. Infection results in growth

loss, root and butt rot, uprooting, and tree killing.

Hosts: Virtually all trees and other woody species.

Recognition: Decline in growth increment, foliage yellowing,

distress cone crop, heavy resin flow at tree base, tree death;

early decay appears as a watersoaked area with tiny pockets;

advanced decay is a yellow stringy rot; butt rot sometimes

develops in non-resinous hosts, especially hardwoods.

Disease centers contain numerous stubs, snags, and dying

trees.

White mycelial sheets often shaped like fans developed under

bark of roots and lower bole; rhizomorphs (black or brown

shoestring-like structures) form in the same areas; mushrooms

are golden-yellow with a ring on the stem and grow from

infected material in the fall.

Disease Spread: The fungus survives and grows in old

stumps or dead trees; rhizomorphs are formed and grow

through the soil to infect the roots of new hosts; spread also

occurs across root contacts and grafts; spread by spores is

negligible. On the West Side Douglas-fir develops resistance

to the disease at age 20- Disease centers usually occur around

infected stumps of the former overstory. Secondary attack by

bark beetles is common. Frequently occurs on trees affected

by other root diseases.

Management: West Side - Maintain vigorous growing stock.

In severely diseased areas, plant or favor species that appear

only lightly or not affected; remove stumps of infected trees to

sanitize severely infected sites. Do not thin severely infected

areas. East Side - Precommercial thinning or harvesting and

stump removal may be necessary to sanitize severely infected

sites. Normal tree harvesting does not reduce or prevent

infection and may aggravate the problem. Infected trees

should be treated in recreation areas.

May be Confused With: No other disease or insect if mycelial

fans are present.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Atropellis canker on

lodgepole pinr

Stain under

Atropellis canker

Fruit bodies of

Atropellis piniphila

Forest Disease

Management Notes

Atropellis Canker

Atropellis canker of pines is caused by two fungi, Atropellis

piniphila. and A. pinicola. The disease occurs in many

lodgepole pine stands, but only a relatively few are severely

infected. Infection can result in reduction of wood quality,

stem breakage, and occasionally tree killing. Bark is difficult to

remove from cankers.

Hosts: Especially damaging on lodgepole pine; also affects

western white, ponderosa, and sugar pines.

Recognition: Elongated, flattened depressions, covered with

roughened bark on stems and branches; heavy resin flow;

dead branches; misshapened stems; occasional mortality of

small trees.

Small black or dark brown fruit bodies (apothecia and conidial

stromata) form on dead bark in the cankers, dark, bluish stain

in the wood behind cankers (the fungus invades the ray cells

and the stain is wedgeshaped in cross section).

Disease Spread: Windborne spores infect new hosts throughout the growing season; spores are not released until fruiting

bodies are moistened; cankers may continue to produce

spores several years after tree death; most infection occurs

through unbroken bark in the nodal region, though some

infection occurs through branch stubs; open-grown trees are

less subject to infection than trees in overstocked stands.

Management: Remove infected trees during thinning; thin

heavily stocked stands early to make conditions less favorable

for the disease; clearcut heavily-infected stands in wide strips

or large blocks and destroy small unmerchantable trees in the

clearcuts; encourage development of mixed species stands;

plant non-susceptible tree species in areas where infection has

been severe; after cutting unmerchantable infected trees, it

may be desirable to burn or chip them as cankers may continue

to produce inoculum for several years after host death. Trees

with deeply indented stem cankers should be treated in

recreation areas.

May be Confused With: Stalactiform rust on lodgepole, white

pine blister rust on western white and sugar nines.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Douglas-fir being killed by

black stain root disease

Diagnostic stain caused by

Ceratocystis wageneri

in Douglas-fir

Forest Disease

Management Notes

Black Stain Root Disease

Black stain root disease is caused by the fungus Ceratocystis

(Verticicladiella) wageneri. Incidence of this disease is

increasing in the Pacific Northwest, particularly in Douglas-fir

plantations. Infection results in growth loss and tree killing.

Hosts: Major hosts are Douglas-fir and ponderosa pine;

mountain hemlock, western hemlock, lodgepole pine, sugar

pine, and western white pine are infected occasionally.

Recognition: Dark-brown to purple-black stain in the sapwood

of roots, root crowns, and lower stems are especially diagnostic. Growth reduction, foliage yellowing, distress cone crops,

basal resinosis, rapid decline, death; symptoms may begin on

one side of the tree.

Disease Spread: Occurs in stands with a large component of

host species; in the Pacific Northwest, most common in 10-30

year-old Douglas-fir plantations; sometimes found killing

ponderosa pine on moist East Side sites; usually found

causing discrete infection centers which contain old dead

trees and trees in all stages of disease development; spreads

from tree to tree across root contacts and grafts at a rate of

6-12 feet per year; long distance spread probably involves

bark beetle and weevil vectors; the fungus dies soon after

death of the host tree.

Management: Remove host trees in infection center and

50-foot buffer strip; replant with non-hosts. Host trees may be

planted 1 year after infected trees are removed.

May be Confused With: Laminated root rot, Armillaria root rot,

mountain pine beetle damage or animal feeding on roots.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Conks of F. pinicola

Forest Disease

Management Notes

Brown Crumbly Rot

Brown crumbly rot is caused by Fomitopsis (Fomes) pinicola,

commonly called the redbelt fungus. This is the most commonly observed rotter of slash and dead trees in the Pacific

Northwest. Conks are occasionally seen on dead portions of

living conifers and indicate considerable decay.

Hosts: Practically all conifers.

Recognition: Hard, woody, perennial, shelf- to hoof- shaped

conks (2-10 inches width); smooth, gray to black upper surface

with a wide red margin; undersurface is white to yellowish.

Brown cubical rot of sapwood and heartwood.

Disease Spread: Spores released from conks are carried by

wind. They germinate on exposed wood. Insects spread the

fungus by carrying mycelial fragments when they emerge from

decayed trees.

Management: Avoid wounding of living trees; salvage living

trees with conks. Trees with conks should be treated in

recreation areas.

May be Confused With: White mottled rot (G. applanatum),

red ring rot (F. pini), and red-brown rot (P schweinitzii).
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Phaeolus schweinitzii conks

Characteristic brown cubical rot

caused by Phaeolus schweinitzii

Forest Disease

Management Notes

Brown Cubical Butt Rot

Brown cubical butt rot is caused by Phaeolus (Polyporus)

schweinitzii, often called the velvet-top fungus. This fungus

causes extensive butt rot in infected trees. It is common in

old-growth trees, particularly those with fire scars. It can also

cause a tree-killing root rot in young trees.

Hosts: Douglas-fir, pines, spruces, larch.

Recognition: Large mushrooms may occur on ground near or

growing from the base of infected trees and on the stem rarely

over 10 foot above the ground; these appear in late summer

and fall and are at first redbrown with a yellow, velvet tinge; as

they age, they attain a dark brown color and resemble cow

droppings; mushrooms growing on the ground have a circular

shape with a depressed center and taper to a short, thick stalk;

those growing on trees are often bracket-shaped; thin

crust-like mycelial layers frequently are found in shrinkage

cracks of decayed wood. There may be no evidence of early

decay, or it may show as a yellow to reddish-brown discoloration running a few inches to several feet ahead of advanced

decay; advanced decay is a distinctive dry, crumbly, brown

cubical rot; decay is limited to heartwood and normally is

confined to roots and butt of the host; extreme decay frequently results in breakage or windthrow.

Disease Spread: Windborne spores infect new hosts through

fire scars and wounded roots; also spreads along roots;

mostly a problem on older trees, though young trees occasionally are affected. The fungus can persist in roots of dead or cut

trees and infect roots of the developing trees.

Management: Avoid wounding trees; when possible, harvest

trees before they become overmature; in recreation areas, treat

all trees showing evidence of infection by this fungus.

May be Confused With: Brown trunk rot (F. laricis), brown

crumbly rot (F. pinicola), white pocket root rot (I. tomentosus).
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

H. nigra on white fire

N. coulteri on

lodgepole pine

Forest Disease

Management Notes

Brown Felt Blight

Brown felt blight is caused by two similar fungi, Herpotrichia

nigra and Neopeckia coulteri. Although this disease is

common in some years, it causes almost no economic loss in

forests.

Hosts: H.. nigra - conifers other than pines; N. coulteri- pine

species.

Recognition: Common at high elevations; lower branches are

covered with dense cobwebby growths of brown to black

mycelium that kill foliage; small black globular fruit bodies are

scattered over the mycelium; the two fungi are macroscopically identical.

Disease Spread: Fungi develop on foliage under snow; high

humidity and mild temperatures (Optima are 50° F for N.

coulteri and 59-64° F for H. nigra), are required for fungus

growth; brown mycelium is very resistant to adverse conditions; after snowmelt, fruit bodies form on mycelium. and

release spores that are windborne and infect susceptible

foliage; damage is primarily growth loss.

Management: Usually none is warranted except in nurseries or

on ornamentals; foliage s rays of 5% Zineb or Maneb applied

before first snowfall are effective in control.

May be Confused With: Gray mold (seedlings).
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Conks of Fomitopsis officinalis

Decay and mycelial felts

in shrinkage cracks

Forest Disease

Management Notes

Brown Trunk Rot

Brown trunk rot is caused by Fomitopsis officinalis commonly

called the quinine conk. Decay by this fungus is most common

in old-growth trees. Trees bearing quinine conks usually are

extensively decayed.

Hosts: Douglas-fir, larch, pines.

Recognition: Conks can be large (4-8 x 8-24 inches), dirty

white throughout, chalky, and pendulous or hoofshaped;

mycelial felts are abundant in shrinkage cracks of decayed

wood (felts taste bitter); brown cubical rot of heartwood.

Disease Spread: Infections occur through broken branch

stubs, or other wounds, especially in old-growth trees; spores

are windborne.

Management: None warranted except avoidance of stem

wounding. Conks generally indicate cull. Salvage merchantable trees with de prevent cull. Trees with conks should be

recreation areas.

May be Confused With: Brown cubical butt rot (P

schweinitzii), brown crumbly rot (F. pinicola).
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Cedar leaf blight

Forest Disease

Management Notes

Cedar Leaf Blight

Cedar leaf blight caused by the fungus, Didymascella

(Keithia) thujina appears sporadically in the Pacific Northwest. Damage is rarely serious in forest stands.

Hosts: Western redcedar, mainly a problem of seedlings and

young saplings.

Recognition: Foliage, especially of lower branches in dense

stands, takes on a scorched appearance; in the spring leaves

turn reddish-brown then gray; in fall, infected leaf twigs drop,

leaving the branches bare. In the spring following infection,

circular to elliptical olive-brown to black fruit bodies are

formed in the upper surfaces of infected leaves.

Disease Spread: Spores are discharged from June to

mid-October during periods of moist weather and infect new

foliage; trees in the interior of dense stands or in deep ravines

where the air is stagnant and moist are most likely to be

infected; seedlings covered by snow are also prone to severe

infection.

Management: Several applications of fungicide throughout

summer and fall will control the disease in nurseries; no

control yet devised for forest stands and is rarely required.

May be Confused With: Normal fall foliage drop.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Typical comandra rust infection with

aecia on sapling pine

Bastard toadflax infected with

comandra rust

Dead top caused by

comandra rust

Forest Disease

Management Notes

Comandra Blister Rust

Comandra blister rust caused by the fungus, Cronartium

comandrae is an important disease only in local areas of the

ponderosa pine type in the Pacific Northwest. It kills branches,

tops, and entire trees.

Hosts: Primary hosts- hard pines, most serious on ponderosa

pines; alternate host- bastard toadflax (Comandra).

Recognition: Spindle-shaped, often inconspicuous swellings

are formed on pine stems and branches; infections break open

and produce a cracked and pitted canker or lesion with

abundant resin flow; rodents frequently gnaw bark from

infections; “hags” (dead branches with discolored foliage

attached) and dead tops are common; the fungus grows

slowly down infected stems causing progressive dying-, tree

mortality may occur, especially in young trees.

On pines, inconspicuous reddish-orange ooze or drops

(pycnia) appear on swellings in the summer 1 to 3 years after

infection; dark orange spore pustules (aecia) rupture through

bark in the spring of the following year. On bastard toadflax

leaves yellow spots with yellow spore pustules (uredia) and

brownish hairlike structures (telia) occur throughout the

summer and fall.

Disease Spread: Beginning in late spring, aeciospores are

released from pine hosts and are carried by wind to infect

bastard toadflax; aecios e production continues until fall but

tapers off the season progresses; uredia and telia are produced within a few weeks to a month on bastard toadflax

leaves; urediospores reinfect bastard toadflax causing

intensification of the disease; pines are infected by windborne

spores in the late summer or fall; comandra rust is favored by

cool, moist conditions at the time of infection of both hosts;

pine infection tends to occur in wave years when weather

conditions are especially favorable (wet summers).

Management: Concentrate on removing infected trees during

thinning and stand improvement operations; log severely

infected stands; replace susceptible pines with less susceptible species in area where plantations have failed due to

heavy infection. Control of bastard toadflax is impractical,

May be Confused With: Insect attack, animal damage, dwarf

mistletoe, environmental damage.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Branch canker associated with

Cytospora abietis and dwarf mistletoe on

Pacific silver fir

Cytospora canker on

Douglas-fir

Cytospora spore tendrils

Forest Disease

Management Notes

Cytospora Canker

Cytospora cankers are caused b several species of fungi in the

genus Cytospora. This disease is usually associated with

environmental stress. It occurs sporadically in the Pacific

Northwest, but with the exception of the dwarf mistletoe -

Cytospora association, it seldom causes serious damage.

Hosts: Weakened conifers; Cytospara abietis frequently is

found on dwarf mistletoe-infected true firs, and an unidentified

Cytospora has been found causing stem cankers on sapling

and polesize Douglas-fir.

Recognition: Slightly sunken, gradually enlarging cankers on

branches or stems, heavy resin flow on Canker face, death of

branches; occasionally, death of trees.

Small pimple-like fruit pustules (pycnidia) on dead bark; large

numbers of spores ooze from these fruit bodies in mild wet

weather, forming yellow-orange tendrils.

Disease Spread: Spores are carried by wind, insects, and

birds, or rain splash; new hosts are infected through wounds

or dead twigs; the fungus only affects weakened trees, trees

on poor sites, injured trees, and especially drought-weakened

trees; Cytospora abietis on true firs commonly infects dwarf

mistletoe-infected branches; Cytospora species are most

successful when bark is relatively thin; predisposes trees to

bark beetle attack and possibly root diseases.

Management: Maintain a vigorous stand; control dwarf

mistletoe; avoid wounding trees; use local seed source stock;

remove trees with severe flagging and low live-crown ratios.

May be Confused With: Fir broom rust, animal damage,

environmental damage.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Damped-off

Douglas-fire seedling

Forest Disease

Management Notes

Damping-off

Damping-off of seedlings is caused by fungi in the genera

Phytophthora, Pythium, Fusarium and Rhizodonia. Damage

can be extensive in wet springs or poorly drained soils.

Damping-off results in death of succulent seedlings and root

rot with associated stunting in older seedlings.

Hosts: Conifer seedlings.

Recognition: Pre-emergent damping-off is characterized by

failure of seedlings to emerge due to the infection and decay

of the young radicals. Post-emergent damping-off is characterized by infection and decay of succulent stem tissue at or just

below the ground line causing seedlings to fall over. At the

point of infection, the stem is watersoaked and necrptic. Root

infections of slightly older seedlings may also occur causing

partial or total decay; in these cases seedlings may remain

upright after dying.

No visible signs of fungi are seen on damped-off seedlings.

Fungi are easily cultured from infected seedlings and can be

separated from one another by differences in spore and

mycelium characteristics.

Disease Spread: Damping-off fungi are soil inhabitants,

surviving either as dormant spores or mycelium in organic

matter. After the seedlings are infected, additional mycelium or

spores are formed within seedling tissue so that the population of damping-off fungi increases with each successive crop

of trees. Generally, high moisture and high soil pH favor

damping-off. Infection by damping-off fungi is usually most

severe in very young, succulent seedlings, but these fungi

may attack roots of older woody seedlings as well. The

disease can be spread by movement of infested soil and

seedlings.

Management: Nursery beds with high damping-off fungi

populations should be fumigated prior to sowing. Avoid

excessive movement of soil between fumigated and nonfumigated areas. Provide good drainage. Maintain acid soil

(pH 5.5). Seed treatments have not proven to be consistently

effective in preventing damping-off losses. Soil drenches with

registered fungicides may be effective if applied soon after

sowing.

May be Confused With: Heat injury, wind injury,

non-germinating seeds.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Conks of Laetiporus sulfureus

Forest Disease

Management Notes

Dark Brown Cubical Rot

Dark brown cubical rot is caused by the fungus Laetiporus

(Polyporus) sulfereus. It is commonly called the “sulphur

fungus.”

Hosts: Hemlocks, spruces, pines, larches, true firs, hardwoods.

Recognition: Brown cubical rot of the heartwood.

Soft, watery, shelving, annual conks are produced in overlap

ping clusters; upper surface is bright orange to lower surface

is sulfur yellow; mycelial sheets abundant in shrinkage cracks

of decayed wood.

Disease Spread: Infections by spores occur through dead

branch stubs and wounds; often a butt rot in conifers but less

localized in hardwoods; conks usually indicate complete cull;

generally a minor problem in living conifers.

Management: Avoid stem wounds; remove live trees with

broken tops, sizable wounds, or fruit bodies; harvest old,

decadent trees. Trees with fruit bodies should be treated in

recreation areas.

May be Confused With: Nothing if conks are present; brown

crumbly rot and red brown butt rot if conks are absent.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Douglas-fir stand

severly infested with

dwarf mistletoe

Dwarf mistletoe plants on

Douglas-fir

Forest Disease

Management Notes

Douglas-fir Dwarf Mistletoe

Douglas-fir dwarf mistletoe, Arceuthobium douglasii, is

probably the most damaging disease of Douglas-fir in eastern

Washington and eastern and southern Oregon. It infests 42%

of the Douglas-fir type on the East Side. Infection causes

growth loss, wood quality reduction, top-killing, and tree

killing.

Host: Douglas-fir.

Recognition: Leafless, olive-green shoots about 3 to 2 in.

long) on infected branches in witches’brooms; branch and

stem swellings, witches’-brooms that can reach massive sizes,

dead tops, and dead trees.

Disease Spread: Seeds are sticky and forcibly shot from fruits

in the fall; most seeds travel less than 10 feet; seeds germinate

in spring, infection occurs on thin bark wood. Disease spread

is most rapid in multistoried stands; spread in single-storied

stands averages 1-2 feet per year.

Death of host results in death of dwarf mistletoe. Infections

are systemic (spread internally) in Douglas-fir.

Management: Clearcut severely infested stands; remove

infested overstory if a managable susceptible understory is

present. Remove severely infected trees in lightly infested

stands; favor non-hosts in mixed stands.

May be Confused With: Brooms caused by viruses or genetic

abnormalities.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

“Flagging” caused by

Elytroderma deformans

Witches’-broom

caused by

Elytroderma

deformans

Hysterothecia of

Elytroderma deformans

Forest Disease

Management Notes

Elytroderma Needle Blight

Elytroderma needle blight of ponderosa pine is caused by the

fungus Elytroderma deformans. It is the most important

foliage disease of ponderosa pine in the Pacific Northwest.

Infection occurs at low levels in many stands, but usually only

becomes damaging at elevations around 3,500 feet in Washington and 5,000 feet in Oregon. Trees in high infection zones

suffer from growth loss, attack by bark beetles, and tree killing.

Hosts: Ponderosa pine, Jeffrey pine, and rarely, lodgepole

pine.

Recognition: “Flags” (reddened, dead 1-year-old needles with

green current season needles at tip) are conspicuous in spring,

small to large compact witches brooms with upward turning

branches and many dead needles occur when infections

become perennial; inner bark of infected branches contains

numerous dark dead lesions; if severely infected, entire tree

tops may be misshappened, growth loss occurs, and occasionally, trees die or are predisposed to bark beetles and root

diseases.

Clear tendrils of inconspicuous pycnidiospores appear on

reddened needles in spring-, black elongated fruit bodies

(hysterothecia) form on dead needles in summer.

Disease Spread: Windborne spores are released from

hysterothecia for several months beginning in July; only

current year’s foliage is infected; high humidity and cool

temperatures favor infection; and the disease is most severe in

microsites where these conditions prevail. The fungus grows

from needles into woody tissues. Infections in woody tissues

remain active for many years, reinfecting needles and producing spores that begin new outbreaks when environmental

conditions are especially favorable for the fungus.

Management: In immature stands - (1) maintain good spacing

but avoid creating large openings in the stand, (2) remove as

many severely infected trees as possible when thinning (no

trees with “flags” within 6 feet of the leader should be

retained?, (3) prune infected branches where economically 1

justifiable; in mature stands - (1) recognize that considerable

infection can occur without causing appreciable damage;

avoid hasty action, (2) evaluate the situation annually, watch

for evidence of serious damage (tree death, bark beetle attacks,

etc.), (3) log stands when damage becomes severe - discriminate against moderately to heavily infected trees in the

residual stand.

May be Confused With: Dwarf mistletoe, Dothistroma needle

blight, Lophodermella needle cast.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Witches’-broom in

true fir caused by

Melampsorella caryophyllacearum

Needle bearing aecia of

Melampsorella carypphyllacearum

Forest Disease

Management Notes

Fir Broom Rust

Fir broom rust, caused by the fungus Melampsorella

Caryophyllacearum, is occasionally seen in Pacific Northwest

true fir stands. Damage is seldom extensive enough to be

serious.

Hosts: Primary hosts- true firs; alternate hosts-chickweed.

Recognition: Causes formation of conspicuous dense, upright

witches-brooms on true firs; needles on broom twigs are

extremely yellow and shorter and thicker than healthy needles;

broom foliage dies in the fall, causing the broom to appear

dead in the winter; can be confused with dwarf mistletoe

brooms, but contains no dwarf mistletoe plants; severe

infection may result in stem malformation, growth loss, and

occasionally, mortality; causes a leaf or shoot blight of

chickweed.

Yellow spore pustules (aecia) appear in great numbers on

needles of witches’-brooms in summer; orange spore pustules

(uredia and telia) occur on chlorotic chickweek leaves in spring

and summer.

Disease Spread: Both fir and chickweed hosts are required for

completion of the life cycle; windborne basidiospores, infect

newly opened fir buds in spring-, the mycelium becomes

perennial in the fir host, causing production of a

witches’-broom; aeciospores are produced the following

summer (and each summer thereafter), are windborne and

infect chickweed; infection on chickweed also may be perennial and is intensified by urediospore infection; infection is

favored by moist conditions.

Management: Remove trees with main stem infections when

practical; other control measures are not considered economically feasible and are seldom warranted.

May be Confused With: Dwarf mistletoe.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Nursery bed experiencing scattered

Fusarium root rot mortality

Seedlings killed by

Fusarium root rot

Forest Disease

Management Notes

Fusarium Root Rot

Fusarium root rot of conifer seedlings caused by the fungus

Fusarium oxysporum f. sp. pini is the most serious disease in

Pacific Northwest bareroot nurseries. Damage in the form of

seedling death and stunting can become very serious if sites

are not treated.

Hosts: Conifer seedlings.

Recognition: In newly emerging seedlings, causes “damping

off’ (collapse of the seedling at ground line); in older seedlings, causes typical root rot symptoms: rootlet deterioration,

foliage yellowing, general decline, and death; bark of infected

seedlings sloughs off easily; mortality generally scattered

randomly throughout nursery beds.

A variable colored mycelial growth can sometimes be seen on

roots and at the base of the stem; diagnostic microscopic

canoe-shaped (macroconidia) and smaller round spores

(microconidia) form readily in culture.

Disease Spread: The fungus survives in soil on organic matter

or as resting spores (chlamydospores) and infects succulent,

young roots; warm, moist conditions favor the fungus;

especially damaging to very young seedlings (seldom serious

in seedlings 2 years old or older). Soil and seedling movement

in nurseries can spread the disease.

Management : Fumigate nursery soils with methyl bromide

-chloropcrin; maintain good soil drainage in nurseries.

May be Confused With: Pythium, Phytophthora.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Botrytis cincerea-infected seedling

on right, healthy

seedling on left

Forest Disease

Management Notes

Gray Mold

Gray mold of seedlings is caused by the fungus Botrytis

cinerea. This disease is especially common in container

nurseries and in dense 2-year-old and older beds in bareroot

nurseries. Cool, wet conditions favor the fungus.

Hosts: All tree species, especially Douglas-fir.

Recognition: Brownish-gray mold (fungus mycelium) on

infected portions of plants; microscopic fruit bodies that

release puffs of spores when infected seedlings are agitated.

Yellowing and browning of foliage of stored seedlings; top

dieback, bark sloughing, girdling, root deterioration; seedling

death, frequently involving groups of closely associated

seedlings.

Disease Spread: Botrytis cinerea is a common saprophyte and

soil inhabitant Infection and disease spread are favored by

high seedling densities, dead vegetation, and cool, moist

conditions in the field and greenhouse. Spores are spread by

wind currents, agitation, or water. In storage, warm temperatures, stagnant air, and moist conditions favor the spread of

infection throughout boxes or bundles of stored trees.

Wounding predisposes trees to infection; fully dormant

seedlings are less susceptible than those that have not yet

hardened off.

Management: Avoid conditions favorable for the pathogen;

apply fungicides when the disease is noticed or anticipated.

Keep storage areas clean and cool (preferably between 28°

and 36° F), well ventilated, and as dry as possible without

desiccating seedlings (avoid standing water); if molds do

develop, remove infected material from storage areas and

consider fungicide application such as Bravo or Botran.

May be Confused With: Other molds, environmental damage,

brown felt blight.
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Gray Saprot

Gray saprot is caused by the fungus Cryptoporm (Polyporus)

volvatus, often called the pouch fungus. Polyporus is very

common on recently killed conifers.

Hosts: Occurs on most conifers, but most common on

ponderosa and lodgepole pine.

Recognition: Superficial soft grayish saprot of slash and dead

trees.

White to tan leathery globose annual conks issue from insect

holes in the bark; brown tube layer is completely enclosed by

a leathery membrane.

Disease S read: Conks appear 6-18 months after tree death;

bark beetles carry mycelial fragments of the fungus from

infected to uninfected trees; tunneling activities of the beetles

create suitable infection courts for fungus establishment;

spores are probably not insect disseminated and are relatively

unimportant in the infection process.

Management: Generally not a problem on living trees. Salvage

dead trees promptly. Conky trees in recreation areas should be

removed.

May be Confused With: Nothing if conks are present.

C. volvatus conk on

Douglas-fir
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Hemlock Dwarf Mistletoe

Hemlock dwarf mistletoe, Arceuthobium tsugense, infests 21%

of the western and mountain hemlock types in the Pacific

Northwest. Severe infestations cause growth loss, wood

quality reduction, and tree killing. Damage is much more

serious in stands over 100 years old than in younger stands.

Hosts: Principal- western and mountain hemlock; Secondary

Pacific silver, subalpine, and noble fir, coastal lodgepole,

western white, and white-bark pine.

Recognition: Leafless, green or red dwarf mistletoe shoots

(about 2 in. long) a pear on infected branches; basal cups of

old detached shoots remain on branches. Branch and stem

swellings, witches’-brooms, dead tops, branch flagging;

branch mortality is accentuated by fungi that invade mistletoe

infections; severely infected true firs are predisposed to attack

and mortality by fir engravers (Scolytus ventralis).

Disease Spread: Seeds are sticky and forcibly shot as far as 50

feet from fruits in the fall; seeds germinate in the spring,

infection occurs on thin bark wood; spread is most rapid in

multi-storied stands; spread in singlestoried stands averages

1-2 feet per year; spread is faster in open than dense stands;

death of host results in death of dwarf mistletoe.

Management: Clearcut severely infested stands, remove

infested overstory if a manageable susceptible understory is

present; remove severely infected trees in lightly infested

stands; destroy infected live residuals left after clearcutting,

fires, or blowdown; favor nonhosts in mixed stands; trees with

open-faced stem cankers or with dead tops should be treated

in recreation areas; prune witches’-brooms in recreation sites

to prolong tree life.

May be Confused With: True fir dwarf mistletoe on true firs,

but the effects are the same. Suppressed western hemlocks

form simulation brooms when they are-released. Simulation

brooms do not have dwarf mistletoe shoots.

Hemlock dwarf mistletoe plants

Westarn hemlock severaly

infected by dwarf mistletoe

Flagging in noble fir

caused by hemlock dwarf mistletoe

and canker fungi
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Incense Cedar Rust

Incense cedar rust is caused by the fungus

Gymnosporangium libocedri. Incidence of the disease is

sporadic in southern Oregon. Damage is seldom serious.

Hosts: Incense cedar; alternate hosts- serviceberry, hawthorn,

apple, pear, quince, and mountain ash.

Recognition: Red-orange, gelatinous spore pustules (telia)

appear on infected incense cedar foliage in s ng, On incense

cedar, causes spindle-shaped Spring and trunk swellings with

numerous small dark-brown flecks often in a fan- or

wedge-shaped pattern in wood, witches’-brooms and death of

small sprays of foliage; heavy infection results in crown

deformation; small black fruiting bodies on the alternate host

produce an orange colored liquid (pycnial exudate) in early

summer; later, whitishyellow spore cups (aecia) are produced

in clumps usually on the undersurfaces of infected leaves; on

alternate hosts causes light-yellow, circular spots on leaves,

fruits, and tender green shoots.

Disease Spread: Teliospores germinate in place, producing

basidiospores that are windborne and infect alternate hosts in

spring-, aeciospores released during the summer are also

windborne, and infect incense cedar leaves or young stems;

high humidity favors infections on both hosts; symptoms

appear on cedars 1 year after infection; mycelium of the

fungus survives in cedar tissues for many years.

Management: Prune infected branches of ornamental or

nursery trees; no control is warranted in the forest.

May be Confused With: True mistletoe.

Witches’-broom on

incense cedar caused by

Gymnosporangium librocedri

Telia of Gymnosporangium librocedri

on cedar foliage
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Laminated Root Rot

Laminated root rot, caused by the fungus Phellinus (Poria)

weirii is responsible for an annual estimated volume loss of 32

million cubic feet in the West Side Douglas-fir type. Surveys

indicate approximately 5% of the area of highly susceptible

host types in Oregon and Washington is out of production

because of this disease. It causes growth loss, butt decay,

uprooting, and tree mortality.

Hosts: Highly susceptible- Douglas-fir, mountain hemlock,

Pacific silver, white, and grand fir; intermediately susceptiblespruces, larch, western hemlock, red, noble, and subalpine fir;

tolerant-lodgepole, sugar, and western white pine;

resistant-ponderosa pine, western red and incense cedar-,

immune- hardwoods.

Recognition: Growth increment reduction, especially height,

foliage yellowing, distress cone crop, slow crown decline,

death; infected trees are often windthrown, exhibiting a “root

ball” where roots have rotted off just below the root crown;

early decay appears as a reddish stain, usually crescent

shaped or semi-circular in cross-section; advanced decay is a

laminated rot, the wood separating readily at the growth rings

and containing numerous small, elliptical pits; butt rot is more

common than tree killing in tolerant species.

White to grayish mycelium on bark surface of roots (ectotrophic mycelium); reddish, whiskery mycelium between

layers of rotted wood; flat gray to brown fruit bodies formed in

protected locations but infrequently observed.

Disease Spread: The fungus can survive for decades in large

old stumps or roots; new hosts are infected when their roots

contact old infected material; tree to tree spread occurs across

root grafts and contacts; infection centers are generally small

(less than 1 acre) and scattered on West Side, large on East

Side; trees of all ages are affected; secondary attack by bark

beetles is common.

Management: Remove infected trees from infection centers

and susceptible hosts from a 50-75 foot buffer strip then (1)

replant with resistant conifers or immune hardwoods or (2)

remove stumps and roots and replant with susceptible species.

Trees with signs or symptoms should be treated in recreational

areas. Favoring less susceptible tree species is usually the

most practical treatment.

May be Confused With: Annosus root and butt rot, brown

cubical butt rot, black stain root disease, Armillaria root rot, or

animal feeding on roots.

“Root Ball” characteristic of Phellinus weirii infection

Ectotrophic mycelium of

Phellinus weirii

Typical laminated

Phellinus weirii rot
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Larch Dwarf Mistletoe

Larch dwarf mistletoe, Arceuthobium laricis is present in

47% of the western larch type in the Pacific Northwest.

Infected trees suffer growth loss, wood quality reduction, and

death.

Hosts: Principal- western larch; Secondary- subalpine larch,

subalpine fir, mountain hemlock, lodgepole pine. OccasionalEngelmann spruce, whitebark, and ponderosa pine.

Recognition: Leafless, dark-purple dwarf mistletoe shoots

(1.5-4 in. long) on infected branches. Stem and branch

swellings, witches’-brooms, “spike-top” trees. Stem burls

occur where infected branches break off.

Disease Spread: Seeds are sticky and forcibly discharged from

fruits in the fall; seeds germinate in spring, infection occurs

through thin bark on stems and branches. Spread is most rapid

in multi-storied stands; infections cause branch or stem

swelling and eventual death of member; death of host results

in death of parasite.

Management: Clearcut severely infested stands, remove

infested overstory if a manageable susceptible understory is

present; remove severely infected trees in lightly infested

stands; favor non-hosts in mixed stands; in recreation areas,

trees with large, dead tops should be treated.

May be Confused With: No other disease resembles larch

dwarf mistletoe.

Larch dwarf mistletoe plants

Larch dying from

dwarf mistletoe
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Larch Needle Blight

Larch needle blight is caused by the fungus Hypodermella

laricis. This disease appears frequently throughout Pacific

Northwest larch stands. Trees in forest stands generally do

not experience serious damage even though the disease may

appear to be spectacular.

Hosts: Western larch.

Recognition: Needles are reddish-brown over their entire

length as if scorched by fire; damage generally occurs in June;

typically, all needles on a spur are affected.

Small, black fruit bodies (hysterothecia) are formed on dead

needles; fruit bodies often merge to form narrow rows.

Disease Spread: Airborne spores infect larch needles in early

spring, immediately after budbreak; mature needles are

immune; 6 weeks after infection, needles turn red and die; later

in summer, hysterothecia form on dead needles; infected

needles are retained for 1 year or more; spores develop in

hysterothecia in autumn; following spring rains, hysterothecia

rupture and release spores; spores on the old needles can also

be carried by rain splash to newly emerging foliage to cause

infection; infected crowns generally refoliate the following

season; repeated infection may cause growth loss and, rarely,

mortality.

Management: None warranted in forest stands; in nurseries or

on ornamentals, benomyl or maneb applied repeatedly during

infection period (1 week before to 2-3 weeks after budbreak)

should prevent disease.

May be Confused With: Meria laricis, larch casebearer.

H. laricis hysterothecia on

western larch

Larch needles killed by

H. laricis
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Lodgepole Pine Dwarf Mistletoe

Lodgepole pine dwarf mistletoe, Arceuthobium americanum

infests 42% of the lodgepole pine type in the Pacific Northwest. Severe infestations cause growth loss, wood quality

reduction, and tree killing Dwarf mistletoe is the most serious

disease affecting lodgepole pine.

Hosts: Lodgepole pine.

Recognition: Leafless, yellow to olive-green dwarf mistletoe

shoots (about 2.5 in. long) a pear on infected branches and

stems; basal cups of old, detached shoots remain on

branches; branch and stem swellings, witches’-brooms,

branch and top death.

Disease Spread: Dwarf mistletoe seeds are sticky and forcibly

discharged from fruit for distances up to 50 feet in the fall;

seeds germinate in the spring, infection occurs on thin bark

wood; spread is most rapid in multi-storied stands; spread in

single-storied stands averages 1-2 feet per year; spread is

faster in open than dense stands; dwarf mistletoe is a true

parasite, dying with host death.

Management: Clearcut severely infested stands, remove the

infested overstory if a manageable susceptible understory is

present; remove severely infected trees in lightly infested

stands; favor non-hosts in mixed stands; maintain even-aged

stands in single species forests; prune witches’-brooms in

recreation sites to prolong tree life.

May be Confused With: Simulation brooms produced when

suppressed trees are released. Simulation brooms do not have

dwarf mistletoe shoots.

A. americanum plants on

lodgepole

Witches’-broom caused by

dwarf mistletoe
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Lophodermella Needle Casts

Several species of fungi in the genus Lophodermella cause

needle casting of Pacific Northwest pines. Appearance of the

disease is sporadic and strongly influenced by weather

conditions. Trees are seldom killed directly by Lophodermella

needle casts.

Hosts: Pines.

Recognition: Affected needles turn brown in spring of year

following infection; trees take on a scorched appearance;

needles are cast; if infected for several years, trees have a

“lion tailed” appearance and are weak and unthrifty.

Short, elliptical fruit bodies are produced (hysterothecia) on

the needles after they die.

Disease Spread: New host needles are infected by windborne

and rain-splashed spores in early summer; only succulent,

young-needles are infected; symptoms appear the following

year; infection is greatly favored by moist conditions; disease

is most serious on young or small trees.

Management: Usually none warranted. Avoid planting offsite

pine stock, especially in damp areas (canyons, basins, fog

belts, etc.). Nursery or ornamental trees may be protected by

spraying with two applications of bordeaux mixture, once

when new needles are half-grown and again when growth

ceases.

May be Confused With: Dothistroma needle blight, environmental damage, Elytroderma needle blight, root diseases.

Ponderosa pines infected by

Lophodermella morbida

Lodgepole pines infected by

Lophodermella concolor

Dead ponderosa pine needle

bearing hysterothecia of

Lophodermella morbida
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Mechanical Injury

Mechanical injuries are caused by a large number of agents.

The most common are wind, hail, falling trees, and

man-operated equipment. Large losses are associated with

mechanical injury. Injuries commonly become infected by

wood decay fungi.

Hosts: All trees; thin barked species are more subject to

wounding.

Recognition: Windthrown and broken trees lying approximately in the same direction indicate damage from severe

wind; hail damage appears mostly on thin bark stems, twigs,

and occurs only on the upper sides; scars from equipment

(bulldozers, axes, etc.) resemble animal feeding wounds, but

lack teeth marks; wood is often goughed.

Management: None for hail; for wind, avoid opening tip

shallow rooted stands, especially in root-diseased areas;

equipment-caused damage can be reduced by good pre-sale

preparation and proper logging techniques.

Pre-Sale Preparation

1. Do not log in spring or early summer in easily

injured species.

2. Select equipment appropriate to site.

3. Mark leave trees rather than those to be cut.

4. Lay out skid trails in advance.

5. Cut short logs.

6. Do not thin stands of young, thin-barked species too

heavily.

Logging Techniques

1. Harvest trees first in skid trails.

2. Cut stumps low to prevent skidder shunting.

3. Fell trees either away or toward skid trails.

4. Use end-line skidding.

5. Limb, top, and buck logs before skidding.

May be Confused With: Insect and animal damage.

Hail injury on grand fir

Scarring caused by

logging equipment

Damage caused by

severe winds
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Mottled Rot

Mottled rot is caused by the fungus Pholiota limanella. This

is often called the “yellow cap fungus.”

Hosts: Hardwoods, hemlock, true fir.

Recognition: Brown mottled rot of heartwood.

Soft annual mushrooms with yellow central stem appear on

infected trees in late summer and fall; upper surface is sticky,

slightly scaly and yellow; undersurface has yellow to brown

gills; mushrooms may appear in clusters.

Disease Spread: Generally associated with wounds, especially

basal scars on old growth. The fungus produces spores that

are carried by winds. They can cause infection if they land on

wood exposed by wounds.

Management: Avoid tree wounding; remove live trees with

sizable wounds or mushrooms; harvest old, decadent trees.

Trees with basal scars or mushrooms should be treated in

recreation areas.

May be Confused With: Armillaria root rot.

Mushrooms of P. limonella

Decay associated with

P. limonella
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Needle Cast of Larch

Needle cast of larch is caused by the fungus, Meria Laricis.

This disease appears sporadically throughout Pacific Northwest larch stands and nurseries growing larch seedlings. Trees

in forest stands generally do not experience serious damage

even though the disease may appear spectacular. Damage is

greatest on 2-year and older seedlings in nurseries. Tree killing

can occur in nurseries.

Hosts: western larch (Larix occidentalis), subalpine larch (L

lilyalii), European larch (L. decidua), Japanese larch (L

leptolepis), and hybrid larch (L eurolepis).

Recognition: Needle discoloration and browning begin at the

tips or in the middle of the needle, spreading from the tip

downward. Not all needles on each individual spur shoot are

affected. Lower portion of trees are often affected first.

Infected needles are cast early. Discoloration first appears in

mid- to late-spring.

Spore clusters are found in and emerging from stomatal

openings on the underside of needles. Spore clusters are white

and difficult to see without staining and magnification.

Disease Spread: Short distance spread occurs by spores

traveling from infected to healthy needles or trees. Spores

probably are spread via wind or water droplets. Long distance

spread can occur by transplanting infected stock into

disease-free areas. Infection and spread are favored by moist

weather. The fungus overwinters in needles on the ground or

in the trees.

Management: No measures are available or needed for control

of needle cast in forest trees. Control in forest nurseries is

achieved by:

1. Use of benomyl and maneb fungicides at 1.0 and 1.5 lbs. a.i./

100 gallons of water at bud swell, 1 month after first application, and at 2 or 3 week intervals thereafter. Continue applications until weather becomes dry or until the end of July.

2. Transplant seedlings at end of first year to seedbeds where

larch have not been grown recently to prevent reinfection of

new growth by the fungus overwintering in fallen needles.

3. Avoid introduction of diseased stock into disease-free

nurseries. This can be accomplished by growing all larch stock

from seed.

May be Confused With: Frost damage, Hypodermella laricis,

larch casebearer.

Needle discoloration caused by

Meria laricis Meria laricis on

2-0 seedlings
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Pecky Rot

Pecky rot, caused by the fungus Polyporus amarus, is the

most important stem decay of incense-cedar in Oregon. Conks

indicate extensive decay columns.

Hosts: Incense-cedar.

Recognition: Early rot appears as a yellowish brown discoloration in the heartwood; advanced decay consists of

round-ended pockets (1/2-12 in. long) containing dark brown,

crumbly, dry rot with numerous longitudinal shrinkage cracks;

as decay intensifies, pockets become more numerous and

sometimes nearly coalesce; rot is confined to the heartwood

and usually is not prominent in the butt of the tree; shot-hole

cups (depressions in the bark caused by woodpeckers

searching for insects at a former conk location) are common

indicators of infection.

Annual conks form on the bark above open knots in late

summer or fall; conks are hoofshaped, 4 to 9 in. wide, and buff

to bright yellow in color; when fresh, conks are soft and moist,

becoming firm and dry with age; numerous small angular pore

openings cover the underside of the conks; conks are

destroyed rapidly by insects.

Disease Spread: Airborne spores infect, chiefly through open

fire wounds, large open knots, and broken branch stubs; trees

are particularly susceptible when growing in ravines or other

locations favoring the retention of surface moisture on

exposed heartwood; mainly a problem of older trees; trees

exhibiting either conks or shot-hole cups are almost certain to

be unmerchantable as the result of extensive decay.

Management: Lower rotation age for incense-cedar; fell trees

with conks and shot-hole cups; avoid injuring trees. Trees

with conks should be removed in recreation areas.

May be Confused With: Nothing.

Polyporus amarus conk

Pecky rot caused by

Polyporus amarus
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Phomopsis Canker of Douglas-Fir

Phomopsis canker of Douglas-fir is caused by the fungus

Diaporthe (Phomopsis) lokoyae. This disease appears

periodically in the Pacific Northwest, typically 1 or 2 years

after droughts. Damage is usually not serious. Infection can

result in cankers, top-killing, and tree killing of small trees.

Hosts: Douglas-fir.

Recognition: Infection causes distinct roundish or oval

sunken cankers with brown bark. Bark sloughs in the following

growing season. Some resin flow may occur following

infection. Small dead branchlets are frequently in the center of

cankers. Bark on dead growing tips has a blackish-brown

scorched appearance. Fruit bodies appear as fine black

pimples on dead bark.

Disease Spread: Fungus spreads by spores produced in fruit

bodies; wind-borne spores are forcibly ejected from sexual

fruit bodies (perithecia); rain-disseminated spores ooze out of

asexual fruiting bodies (pycnidia); spores infect small shoots

and mycelium. spreads to the main stem; the fungus is

endemic on suppressed trees and branches and becomes

locally epidemic during droughts.

Management: Avoid poor planting sites and overcrowding; in

nurseries watering during dry periods will prevent weakening

and predisposition to the disease; pruning off affected

branches will help control the disease on ornamental trees.

May be Confused With: Sunscald, wounds, animal damage.

Phomopsis canker on

young Douglas-fir

Top-kill by

Phomopsis canker
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Phytophthora Root Rots of Seedlings

Several species of the fungus genus Phytophthora cause root

rots of conifer seedlings grown in Pacific Northwest bare root

nurseries.

Hosts: Conifer seedlings.

Recognition: Patches of, or scattered dying seedlings.

Stunting, yellowing, and wilting usually precede death;

patches may expand in size; red to brown discoloration of

cambium of roots and root collar is a common symptom; the

line separating discolored from unaffected tissue is usually

distinct; often only root tips are infected. No visible signs of

the fungi occur on the roots or above ground parts.

Disease Spread: Phytophthoras invade the root cambium from

the soil; mycelium and infective spores of Phytophthoras are

quite fragile and require high soil moisture to survive.

Thick-walled spores (oospores, chlamydospores) are formed in

host tissue. These may survive several years in the soil.

Infested soil may be moved on trees, machinery, or by man to

noninfested areas. Contact of spores with susceptible roots

leads to spore germination and production of motile

“zoospores” which infect host roots. Zoospores are spread via

water or soil. More spores are formed soon after infection.

Often the disease is confined to wet, low-lying areas, along

drainages, or where drainage is poor. The fungus requires high

soil moisture in order to infect and survive.

Management: Avoid use of low, poorly drained areas r nursery

production. Improve drainage by tiling. Restrict use of

machinery in infested areas, particulary when soil is wet.

Prevent movement of soil from infested to noninfested areas of

nursery. Avoid overwatering to puddle or run-off point.

Sanitize infested beds by removing and burning all infected

trees. Avoid movement of infected trees within and between

nurseries. Fumigate soil before sowing. Plant resistant or less

susceptible species in previously infested areas.

May be Confused With: Nematodes, Cylindrocladium root rot.

Phytophthora root rot in transplanted Douglas-fir

Cambium discoloration

casued by Phytophthora

Wilting and killing of

Douglas-fir seedlings casued by

Phytophthora root rot
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Port-Orford-Cedar Root Rot

Port-Orford-cedar root rot is caused by the fungus

Phytophthora lateralis. This is a devastating disease that has

killed thousands of Port-Orford-cedars.

Hosts: Port-Orford-cedar, occasionally Alaska cedar in

ornamental settings.

Recognition: Rapid decline and death; crowns fade from

yellow through red and brown; cinnamon-brown stain in wood

of roots and root crowns.

Disease Spread: Spores spread in moving water, germinating

when they contact roots; spores may be carried from place to

place in soil on logging equipment, animals, etc. Tree to tree

spread also occurs across root grafts; conditions favorable for

Port-Orford-cedar also favor the disease; P. lateralis is an

introduced fungus, and there are only traces of resistance to

the disease in Port-Orford-cedar populations.

Management: Avoid moving infested soil from infested to

uninfested stands; concentrate Port-Orford-cedar on slopes

that do not receive drainage from roads; favor other tree

species in drainages.

May be Confused With: Armillaria root rot.

Characteristic Brown Stain caused by

Phytophthora lateralis

Tree mortality caused by

Phytophthora lateralis
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Red Band Needle Blight

Red band needle blight is caused by the fungus Dothistroma

pini. It is occasionally damaging to pines in the Pacific

Northwest. Damage seems to be most severe on off-site trees.

Hosts: Most commonly infects lodgepole and ponderosa pine;

other pine species are occasionally infected.

Recognition: Yellow to tan watersoaked spots and bands

begin to appear on infected needles in July; these turn reddish

brown with time, and the ends of the needles die; infected

needles drop in late summer, fall, or, in some cases, spring of

the following year; infected trees have a scorched appearance

and may exhibit a “lion’s tailing” effect with a few healthy

needles concentrated at the outer ends of branches or near

tops.

Inconspicuous (stromata) black fruit bodies containing spores

form in the center of the red bands under the needle epidermis,

which splits open at spore release.

Disease Spread: Spores are released from May to November,

are windborne, and can infect needles of all ages; considerable

moisture is necessary for germination and infection, and

spores are usually released during periods of rainfall; the

fungus completes its entire life cycle in 1 year; trees under 10

years old are most susceptible.

Management: None usually warranted except for nursery or

ornamental trees. When necessary, control can be attained

with two applications of a copper fungicide, once just before

needles emerge and again shortly after; pine clones resistant

to the disease can be planted in areas where the pathogen is

especially damaging.

May be Confused With: Lophodermella needle casts,

Elytroderma needle blight, environmental damage, root

diseases.

“Lion’s Tailing” on a

severely infected tree

Red-band symptoms on

needles infected by

Dothistroma pini
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Red Ring Rot

Red ring rot, caused by the fungus Phellinus (Fomes) pini, is

the most common stem decay of conifers in the Pacific

Northwest. Enormous volumes of wood are decayed by this

fungus It is most common in old growth stands. In addition to

causing stem decay, it can form sunken cankers on true firs,

especially in southern Oregon.

Hosts: Douglas-fir, pines, larch, hemlocks, and true firs.

Recognition: Hoof-shaped to bracket-like perennial conks on

stems, often issuing from knots or branch stubs; upper surface

of conk is rough, dull gray to brownish black with concentric

furrows paralleling the lighter colored margin; lower surface is

a rich brown color with small circular to large sinuous tube

openings; context is a distinctive cinnamon color and is

punky; on true firs, conks appear on sunken areas around the

main stem. Early decay appears as a red to purple discoloration

of the heartwood; advanced decay appears as numerous small

pockets (1 mm x 2 mm) containing white mycelium (this kind of

rot is commonly called “white speck”) decay often occurs in

concentric bands or rings; “punk knots” are an indication of

infection on some trees.

Disease Spread: The disease is spread by wind-carried spores

that germinate on wounds and branch stubs.

Management: Salvage infected trees before excessive merchantability is lost; increasing amounts of decay in trees are

indicated by larger size and number of conks and wider

spacing between them; maintain young, vigorous stands;

avoid scarring trees; in recreation areas, check all trees with

conks and remove those with amounts of rot sufficient to

render them hazardous.

May be Confused With: Brown crumbly rot (F. pinicola).

Phellinus pini

var. cancriformans conks

on white fir

Phellinus pini conks

Phellinus pini rot

on fir

“Punk knot” caused by

Phellinus pini
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Rhabdocline Needle Cast

Rhabdocline needle cast of Douglas-fir is caused by the

fungus Rhabdocline pseudotsugae. This disease is occasionally common, but seldom damaging in Douglas-fir stands

unless the trees are off-site.

Host: Douglas-fir.

Recognition: Yellow and purple blotches appear on infected

needles in the fall and following spring. Needles drop 1 year

after infection. Purplish-pink fruit bodies break through the

undersides of 1-year-old needles to expose orange-brown

spores.

Disease Spread: Fruit bodies mature in May to June on

1-year-old needles and spores released from them are

windborne, spores require considerable moisture to germinate,

because of this and since infected needles are not killed and

cast until the following year, the disease is most visible

following wet years; only current season’s needles are

susceptible. There is considerable variation in the susceptibility of Douglas-fir to this disease, in general, coastal

Douglas-fir is less susceptible than the inter-mountain variety

and local seed source stock is less susceptible than offsite

stock, but trees within any stand show different levels of

infection (many trees are immune); disease is most common on

trees 5-30 years old.

Management: Usually none is warranted; disease normally

causes growth loss, not mortality; nonsusceptible trees can be

favored when thinning; establish plantations with local seed

sources; may be controlled by fungicides or rogueing in

Christmas tree plantations.

May be Confused With: Swiss needlecast, root diseases.

Browning of previous

year’s needles infected by

Rhabdocline pseudotsugae

Defoliation caused by

Rhabdocline needle cast

Fruit bidies of Rhabdocline pseudotsugae on

undersurface of

Douglas-fir needles
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Rhizina Root Rot

Rhizina root rot is caused by Rhizina undulata, sometimes

called the teapot fungus. Seedlings affected by this disease

usually die. It does not cause serious large-scale losses. Small

groups of seedlings may be killed. Damage is most common in

the northern Washington Cascades.

Hosts: Young conifer seedlings (Douglas-fir, pines, spruces,

hemlocks, true fir).

Recognition: Similar to those caused by drought or other root

diseases; foliage becomes yellow, seedlings decline rapidly

and die.

Brown to black, fleshy fruit bodies (apothecia) resembling liver

grow on duff or mineral soil around infected seedlings; when

fresh, fruit bodies have a whitish-yellow margin and a

yellow-gray undersurface. Fruit bodies are attached to host

roots or other organic material in the soil by root-like structures called rhizoids.

Disease Spread: Infects only seedlings established on

recently burned areas and is usually damaging in such areas

for only 2 years after burning; wind carried spores settle in soil

and are activated by high temperatures created when slash is

burned; the mycelium either directly attacks seedling roots or

colonizes old roots and burned wood from which it infects

newly established seedlings; mortality occurs during the

growing season; fungus most prevalent on moist but not wet

sites. Damage is most severe in northwest Washington.

Management: In most cases, no special management is

necessary because damage is negligible; in localized areas

where past damage has been severe, future damage can be

avoided by piling and burning slash and not planting in the

burned areas, or by delaying planting for 1 2 to 2 years after

broadcast burning.

May be Confused With: Other root diseases, drought

Rhizina undulata ascocarp and

dead infected seedling
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Rust Red Stringy Rot

Rust red stringy rot is caused by Echinodontium tinctorium,

commonly called the Indian paint fungus. Decay is most

serious in old-growth trees. One large conk indicates approximately 40 feet of cull. This is the most important cause of stem

decay of true firs in the Pacific Northwest.

Hosts: True firs, hemlocks.

Recognition: Hard, woody, hoof-shaped conks occur, mostly

at branch stubs; the upper surface of the conk is dull black

and rough, the undersurface is gray and composed of coarse

teeth; the interior of the conk is bright orange. Early decay

appears as a light-brown stain in the heartwood; advanced

decay is a rust-red stringy rot; “punk knots” are sometimes

found on infected trees.

Disease Spread: Windborne spores infect new hosts through

tiny (0.5 mm) dead branch stubs; the fungus remains dormant

until the tree is stressed (usually by wounding). Once activated, it rapidly decays wood.

Management: Maintain a vigorous stand; keep rotations to

less than 150 years if possible; salvage infected trees before

merchantability is lost; avoid wounding trees; monitor decay

in infected trees in recreation areas and remove trees that have

conks; when thinning, avoid leaving trees suppressed for

more than 50 years; avoid retaining advanced regeneration

that is over 50 years old, that is growing under conky

old-growth, or that is growing on sites poorly adapted for

hemlock or fir growth. A computer program is available to

assess the risk of rust red stringy rot in suppressed understories.

May be Confused With: Nothing, especially when conks are

present.

Typical rot caused by

Echinodontium tinctorium

Echinodontium

 tinctorium conk

Interior of

Echinodontium tinctorium conk
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Spruce Broom Rust

Spruce broom rust is caused by the fungus Chrysomyxa

arctostaphyli It is occasionally seen in Pacific Northwest

spruce stands, but seldom causes damage.

Hosts: Primary hosts- spruces; alternate host -kinnikinnick.

Recognition: Causes conspicuous witches’-brooms; with

profuse short twigs; needles on witches’-broom twigs are

yellow in summer, die, and are shed in fall, leaving brooms to

appear dead during winter; heavy infection results in

spike-tops, dead branches, bole deformation, growth loss, and,

occasionally, tree mortality; causes a purple-brown leaf spot

on kinnikinnick.

Whitish-yellow spore pustules (aecia) occur in great numbers

on foliage of witches’-brooms in summer; brooms appear

yellow; orange-brown spore pustules (telia) occur on the

undersides of kinnikinnick in late spring.

Disease Spread: Both hosts are required for completion of the

life cycle; spores that infect both hosts are windborne, and

moist conditions favor infection.

Management: Brooms could be pruned from ornamental trees;

seldom serious enough in Pacific Northwest forest stands to

justify control.

May be Confused With: Dwarf mistletoe, which rarely infects

spruces.

Chrysomxa arctostaphyli broom

on spruce
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Spruce Cone Rust

Spruce cone rust is caused by two fungi, Chrysomyxa pirolata

and C. monesis. Incidence of this disease is sporadic in the

Pacific Northwest. It can cause considerable damage to spruce

seed crops in local areas.

Hosts: Primary hosts- spruces; alternate hosts- winter green

and single delight.

Recognition: On spruce, causes malformation, browning, and

premature opening of cones accompanied by destruction of

seeds; yellow spore masses (aecia) develop between cone

scales; on alternate host, may cause slight atrophy, yellowing

of foliage, or no visible symptoms; yellow spore pustules

(uredia and telia) form on leaves, petioles, stems, peduncles,

and flowers of alternate host in spring, summer, and fall.

Disease Spread: Both spruce and alternate hosts are required

for completion of the pathogen’s life cycle, but perennial

infections and continuing urediospore production make

long-term survival, intensification, and inoculum buildup

possible on the alternate hosts; spores that infect both hosts

are windborne; spore germination and infection are favored by

moist conditions in summer.

Management: Remove alternate hosts within 500’of spruce

seed orchards if the disease has been a problem in the past.

May be Confused With: Insect damage.

Spruce cones infected by

Chrysomyxa pirolata
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Stalactiform Rust

Stalactiform rust is caused by the fungus Peridermium

stalactiforme. This disease is quite common in Pacific Northwest lodgepole pine stands, however, the percentage of trees

infected is usually quite low. Infection causes stem malformation, and breakage, but

seldom tree killing. Lumber recovery from infected trees is poor

because the wood is pitch-soaked at canker sites.

Hosts: Primary host lodgepole pine; alternate hosts Indian

paintbrush and other members of the Scrophulariaceae.

Recognition: Young infections appear as slight

spindle-shaped swellings on stems and branches. Older

infections produce diamond-shaped cankers that can be up to

30 feet long. Cankers are pitch-soaked and yellow. Bark on

canker faces sloughs off, leaving ridges; rodents frequently

gnaw bark around infections. Small inconspicuous blister-like

swellings with clear ooze appears on young cankers. Yellow

spore pustules (aecia) form on the edge of active cankers in

early summer. Orange spore pustules (uredia and telia) are

produced on leaves of alternate hosts in the summer.

Disease Spread: Aeciospores produced in May through

August are windborne and infect the alternate host; pines are

infected during late summer and fall by Windborne spores;

infection of both hosts is favored by moist conditions.

Management: Remove infected trees during thinning and

stand improvement projects; removal of alternate host is

impractical.

May be Confused With: Atropellis canker, western gall rust,

wounds.

Aecial stage of

stalactiform rust on pine

Stalactiform rust canker on

lodgepole pine
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Swiss Needle Cast

Swiss needle cast is caused by the fungus Phaeocryptopus

gaumanni. This disease is very common in western Oregon

and Washington. Damage is seldom serious in forest stands,

but is probably the most important disease in Christmas tree

plantations.

Hosts: Douglas-fir.

Recognition: Yellowing and browning of infected previous

year’s needles in spring shortly after current needles emerge;

loss of 1- and 2-year-old needles in summer; needle casting

begins in the lower portion of tree crowns and progresses

upward. Severely infected trees may have only current

season’s needles in the fall . Tiny black fruit bodies (perithecia) of the fungus appear in the stomatal openings on the

underside of current year’s needles as early as October and

increase in numbers throughout the winter and spring; large

numbers of fruit bodies cause the normally white stomatal

rows to appear black.

Disease Spread: Perithecia mature in April and May on

1-year-old needles; spores released from them are windborne;

spore release is dependent upon wetting of the fruit bodies;

spore germination also requires ample moisture on current

season’s foliage. The disease is most noticeable following wet

springs. Succulent foliage, dense stocking and moist conditions favor infection. There is considerable variation in

susceptibility to infection between seed sources.

Management: Usually none is warranted in forest stands;

disease normally causes growth loss, not mortality; may be

controlled in Christmas tree plantations by one application of

chlorothalonil, maneb, or benomyl applied in early June.

May be Confused With: Rhabdocline needle cast, root

diseases.

Perithecia of Phaeocryptopus gaumanni

on undersurface of

Douglas-fir needeles

Defoliation caused by

Swiss needlen cast
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

True Fir Dwarf Mistletoe

True fir dwarf mistletoe, Arceuthobium abietinum, infests

thousands of acres of true fir types in southern Oregon and

the eastern slopes of the Cascades in Oregon. Infestations are

not common in Washington. Infection results in growth loss,

wood quality reduction, and tree killing, especially in old trees.

Hosts: Primary- white, grand, and Shasta red fir; SecondaryPacific silver fir. There are two varieties of true fir mistletoe;

one on white and grand fir and one on red fir. White fir dwarf

mistletoe does not infect red fir and vice versa.

Recognition: Leafless yellow-green dwarf mistletoe shoots

(about 3 to 8 inches long) appear on infected branches; basal

cups of detached shoots remain on branches. Infection causes

branch and stem swellings witches’-brooms are small and flat;

branch flagging is accentuated by fungi that invade mistletoe

infections. Severely infected trees are predisposed to attack by

fir engravers (Scolytus ventralis) and possibly root diseases.

Disease Spread: Seeds are sticky and forcibly discharged up

to 50 feet from the fruit in the fall, landing on surrounding

trees. Infection takes place on branches or stems where bark is

thin in the spring-, spread is most rapid in multi-storied stands;

spread in single-storied stands averages 1-2 feet per year;

death of the host results in death of dwarf mistletoe.

Management: Clearcut severely infested stands; remove

infested overstory from manageable susceptible understory;

remove infected trees when thinning lightly infested stands;

destroy infected live residuals left after clearcutting, fires, or

blowdown; favor non-hosts in mixed stands. Trees with

open-faced stem cankers should be treated in recreation areas.

Trees with good live-crown ratios can tolerate heavier

infection levels than trees with poor live-crown ratios.

May be Confused With: Fir broom rust. Hemlock dwarf

mistletoe, but the effects on hosts are the same.

Flagging in grand fir caused by

true fir dwarf mistletoe

and canker fungi

Mistletoe stem canker

Arceuthobium abietinum on

white fir
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

True Mistletoes

True mistletoes in the Pacific Northwest are all members of the

genus Phoradendron. The most conspicuous true mistletoes,

infect oaks in western and southern Oregon. Severe infestations can cause growth loss, branch dieback, and tree killing.

Hosts: Hardwoods (oaks), junipers, incense cedar.

Recognition: Infection can cause excessive twig formation

(witches’-brooms); occasionally branch death. Conspicuous

leafy, perennial evergreen tufts of mistletoe shoots; stems and

leaves are green but may have a yellow or brown cast; seeds

are pearly white.

Disease Spread: Seeds are borne in white or red fruits and are

distributed by birds and other animals; unlike dwarf mistletoes,

the seeds are not forcibly discharged; infection occurs on

young, thin bark of host; plants make most of their own food

by photosynthesis but obtain water and some nutrition from

their hosts; generally causes little damage except in cases

where mistletoe plants are extremely numerous.

Management: Usually not warranted; remove heavily infected

individuals. Prune severely infected branches. Harvest plants

for Christmas smootching.

May be Confused With: Dwarf mistletoes, incense cedar rust

True mistletoe on incense cedar

True mistletoe on juniper

True mistletoe on oak
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Western Dwarf Mistletoe

Western dwarf mistletoe, also called ponderosa pine dwarf

mistletoe, Arceuthobium campylopodum, infests 26% of the

ponderosa-Jeffrey pine type in the Pacific Northwest. Infected

trees experience growth loss, wood quality reduction, and

premature death.

Hosts: Principal- ponderosa, Jeffrey, and knobcone pine;

Secondary- lodgepole pine.

Recognition: Leafless, olive-green to yellow dwarf mistletoe

shoots (3-8 in. long) on infected branches; basal cups remain

after shoots die. Branch and stem swellings, witches’-brooms,

branch flagging, dead tops, deformed trees.

Disease Spread: Seeds are sticky and forcibly shot from fruits

in the fall (max. distance 100 ft.); seeds germinate in spring,

infection occurs on thin bark wood; infections cause branch or

stem swellings and eventual death of member; death of host

results in death of parasite. Disease spread in dense stands is

slow, is fastest at 9-foot tree spacings, and is reduced at

18-foot spacings.

Disease spread is most rapid in multi-storied stands; spread in

single-storied stands averages 1-2 feet per year.

Management: Clearcut severely infested stands. Remove

infested overstory to protect susceptible understory. Remove

severely infected trees in lightly infested stands; favor

nonhosts in mixed stands. Prune witches’-brooms to prolong

tree life in recreation sites.

May be Confused With: Elytroderma needle blight.

Witches’-brooms caused by

 dward mistleto

Female dwarf mistletoe plants

with seeds on ponderosa pine
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Western Gall Rust

Western gall rust is caused by the fungus Endocronartium

(Peridermium) harknessii. This is probably the most commonly observed disease of lodgepole pine. Practically all

Pacific Northwest lodgepole pine stands are infected. Severe

infection causes stem malformation, breakage, and tree killing,

especially of seedlings.

Hosts: Two and three-needle pines, especially lodgepole and

ponderosa pine.

Recognition: Small to large globose to pear-shaped galls on

branches or stems; galls on main stems may continue to grow

for years, forming very large, hard burls or may partially girdle

the stems and die, developing into cankers. An inconspicuous

white or colorless ooze (pycnia) may appear tween bark

fissures in spring; yellow-orange spore pustules (aecia) are

produced in cracks on galls in spring and early summer.

Disease Spread: Aecia are produced each spring as long as

the fungus is alive in the host (may be as long as 100 years);

spores are windborne and infect other hard pines, no alternate

host is required; moist conditions stimulate spore release and

favor infection;

symptoms may develop the same year as infection or 1 to 2

years later. Infection occurs on succulent stem tissue. The

fastest growing trees are more susceptible than suppressed

trees.

Management: Selective removal of trees exhibiting numerous

galls, especially stem galls (trees with only small numbers of

branch galls do not suffer much growth loss and may be

retained); favor uninfected or lightly infected trees during

thinning or seed collection. Trees with deeply indented (3 to

2 of the bole) cankers on the upper stem should be treated in

recreation areas. Branch galls could be pruned from ornamental pines.

May be Confused With: Stalactiform rust, dwarf mistletoe,

atropellis canker.

Old gall on main stem

Aecia on gall in spring

Endocronartium harknessii gall
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

White Mottled Rot

White mottled rot is caused by Ganoderma applanatum,

commonly called the artist’s conk. This fungus is common

throughout western Oregon and Washington.

Hosts: Hardwoods, some conifers (especially western hemlock

and Douglas-fir).

Recognition: Hard, woody, shelf-like perennial conks which

may reach a width of 2 feet or more; upper surface is smooth,

zoned, gray to black in color; lower surface is white to

yellowish turning brown when bruised, artist’s scribe the lower

surface. White mottled rot with fine black zone lines.

Disease Spread: Spores are windborne, infection occurs

through wounds; mostly found on living or dead hardwoods

or dead conifers; does occasionally cause rot of heartwood

and living sapwood of conifers.

Management: Avoid tree wounding; remove live trees with

broken tops, sizable wounds, or conks; harvest old, decadent

trees. Trees with conks should be treated in recreation areas.

May be Confused With: Brown crumbly rot (F pinicola).

Conks of G. applanatum
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

White Pine Blister Rust

White pine blister rust is caused by the fungus Cronartium

ribicola. This is the most serious pest of 5-needle pines in the

Pacific Northwest. Annual losses are estimated to be about 5

million cubic feet.

Hosts: Primary hosts- western white, sugar, and white bark

pines. Alternate hosts- members of the genus Ribes.

Recognition: Yellow and red needle spots; spindle-shaped

swellings often with small Cup-like depressions on branches;

cankers with dead roughened bark, margins greenish-yellow to

orange; flagging of branches and tops; tree mortality; defoliation of Ribes.

Clear, sappy ooze (pycnia) and white to yellow-orange spore

pustules (aecia) ap ar on swollen portions of pine stems in

spring-, reddish spore pustules and brown tails (uredia and

telia, respectively) develop on the underside of Ribes leaves in

spring and summer.

Disease Spread: 5 spore stages in life cycle; both pine and

Ribes hosts are essential for completion of life cycle; spores

that initiate infections on both pines and Ribes are windborne;

48 hours with saturated air and with a maximum temperature of

not over 68°F are necessary for infection of pines; cool, moist

conditions during summer and autumn greatly favor the

disease while warm, dry conditions are unfavorable.

Management: Rate sites for infection hazard; reforest with

resistant 5-needle planting stock on medium and high infection

hazard sites; retain uninfected or very lightly infected trees for

seed sources when cutting severely infected stands; branches

with cankers more than 4 inches and less than 24 inches from

the stem can be pruned; attempts to eliminate the alternative

host (Ribes) or develop chemical controls have proven

unsuccessful.

May be Confused With: Mountain pine beetle damage.

Telial stage of

Cronartium ribicola on Ribies

Aecial stage of

Cronartium ribicola

Branch infection that has

spread to the stem
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

White Pocket Root and Butt Rot

White pocket root and butt rot is caused by the fungus

Inonotus (Polyporus) tomentosus. This disease is seen

most frequently in Engelmann spruce, but it is not widespread

in the Pacific Northwest. It can cause serious damage within

infected stands.

Hosts: Spruces, true firs, lodgepole and ponderosa pine.

Recognition: Crown symptoms (stunting, yellowing) appear in

severely infected trees; presence of disease indicated primarily

by uprooted trees and stand openings; decay of root and stem

appears as small, square pockets separated by firm wood

(honeycombed).

Small (1 - 2.5-inch diameter) yellow to rusty brown mushrooms

with a central stalk appear on the ground or on the tree in the

fall; upper surface is velvety to hairy; undersurface is white.

Disease Spread: The fungus spreads from tree to tree by root

contacts; fungus growth is slow, hence above ground

symptoms may be delayed several years after infection;

windborne spores may function in the spread of the disease.

Management: Harvest visibly infected and nearby “high risk”

trees in severely infected areas. Trees with basal conks should

be treated in recreational areas. Not commonly found in

Oregon and Washington.

May be Confused With: Brown cubical butt rot, other root

diseases.

Decay by I. tomentosus on

ponderosa pine

Fruiting body of

I. tomentosus
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

White Trunk Rot Of Aspen

White trunk rot is caused by the fungus Fomes ignarius var

populinus, also commonly called the false-tinder fungus. This

is the most common cause of stem decay in aspen.

Hosts: Aspen, alder, other hardwoods.

Recognition: Soft yellow-white decay with zone lines in the

heartwood.

Conks are hard, variable in shape, ranging from shelflike to

hoof-like; upper surface gray to black and divided into

irregular squares by numerous cracks; under-surface medium

brown and pitted by numerous tiny pores.

Disease Spread: Spores are released from conks during

periods of high relative humidity and warm temperature;

spores enter branch stubs, cankers, or wounds, and the

underlying wood is colonized and eventually decayed.

Management: Avoid trunk wounds, the principal infection

courts of the fungus. Maintain uniform well-stocked stands

and harvest at ages 80 to 100 years or earlier to reduce decay

losses. Trees with conks are defective and should be treated in

recreation areas. Aspen with conks have an average cull of

82% of the gross tree volume.

May be Confused With: Nothing if conks are present.

Decay caused by

F. ignarius on aspen

Conks of F. ignarius

on aspen
United States

Department of

Agriculture

Forest Service

Pacific Northwest

Region

Forest Disease

Management Notes

Yellow Brown Top Rot

Yellow brown top rot is caused by Fomitopsis cajanderi,

formerly called Fomes subroseus. This fungus causes decay in

broken-top trees.

Hosts: Most damaging on Douglas-fir (especially on the West

Side); occasionally affects other conifers.

Recognition: Infection causes a green stain that develops into

a brown pocket rot of the heartwood below the break. Trees

with broken tops, volunteer tops, crooks, or forked tops,

especially if frequent in the stand, indicate a high probability

of infection. Small, inconspicuous, perennial conks occur in

crotches of malformed tops or in breaks; tops of conks are

dark gray or black; undersurfaces pink or rose-colored.

Disease Spread: Windborne spores infect primarily broken

tops; amount of decay increases with break diameter and time

since break.

Management: Remove broken-top trees when thinning. Stand

replacement should be considered if damage is sufficiently

severe to leave few or no crop trees. Stands near commercial

size may be carried through the rotation if sufficient crowns

remain.

May be Confused With: Brown trunk rot (F. laricis); brown

crumbly rot (F. pinicola).

Fomitopsis cajanderi conks

Decay caused by

Fomitopsis cajanderi