Diseases and Insect Pests of Pacific Madrone

Forest Health Fac t Sheet

EC 1619-E • May 2008

Diseases and Insect Pests of Pacific Madrone

M. Bennett and D. Shaw

Pacific madrone (Arbutus time, however, trees that are Foliage diseases
menziesii) is a broadleaf ever- more shade tolerant may crowd
green tree famous for its smooth, its sides or overtop it. Then the More than a dozen
reddish-orange bark (Figure 1). tree will begin to decline in
A Pacific Northwest native, it vigor; it may show more symp- fungal organisms can
grows from southern California toms of foliage and other dis-
to Vancouver Island. In Oregon1, eases and eventually may die. cause leaf spots and
Pacific madrone is most abun-
dant in Jackson, Josephine, and Madrone is drought tolerant. dead regions on mad-
Douglas counties, but it grows In natural settings, it is well
in every county west of the Cas- adapted to survive long, hot rone leaves, and the
cade crest, usually on warm sites summers with little or no rain.
with shallow, rocky soils. Extended droughts, however, specific disease can
may reduce tree vigor and
As an evergreen, madrone increase disease susceptibility. be difficult to identify.
retains foliage throughout the
year. New leaves emerge each Madrone Diseases For all these foliage
spring. As the year progresses,
these leaves often acquire spots Three major types of disease diseases, however, Figure 2. Leaf spot caused
or discolorations as a result of affect madrone: foliage diseases,
foliar pathogens and, sometimes, branch dieback and trunk canker young leaves are by fungal pathogens.
insect activity. The foliage may diseases, and root diseases.
appear unsightly. This is normal. infected by airborne or Photo: Alan Kanaskie,
By midsummer, most or all of Figure 1. Madrone’s evergreen water-splashed spores Oregon Department of
these leaves are shed, leav- foliage, its cinnamon-color, peeling Forestry.
ing only the new growth from bark, and its twisting trunk make it during wet weather,
spring. In drought years, or in a favorite landscape tree.
a year after heavy fruiting, new often in spring. Trees
growth may appear very stunted.
growing in creek bottoms, val-
Madrone does not tolerate
shade—even its own. A tree leys, and the forest understory
will lose lower branches that
are shaded by the upper portion are most likely to be infected.
of its canopy. Because madrone
resprouts vigorously after cut- Many foliage diseases cause
ting or fire, it often will domi-
nate the canopy initially. Over circular to irregular spots about

1 In the southern part of madrone’s 0.25 to 0.5 inch in diameter
range, its name is pronounced
“mah-drone”; in the north, it’s (Figure 2, above, and Table 1,
“mah-dron-ahh.” Long-time resi-
dents in the south sometimes call it page 2). These may remain small
laurel.
or grow into a foliage blight,

causing irregularly shaped,

dead areas that coalesce and

eventually may kill the entire

leaf (Figures 3 and 4, page 2).

A related disease, tar spot, pro-

duces irregularly shaped, black,

tarlike spots on the undersides

of leaves. These diseases may

result in unsightly foliage but

seldom are serious. They may

lead to an increase in tree stress,

however.

What can you do? In the

home landscape, pruning

dead branches and raking and

destroying fallen leaves before

Max Bennett, Extension forester,
Jackson County; David Shaw,
Extension forest health specialist;
both of Oregon State University.

fall rains may help reduce the Madrone canker occurs on the Figure 6. Madrone canker spirals up
spread of spores and infection main trunk or major branches the trunk at left. A healthy stem is at
of new leaves. Reducing com- (Figure 6), but also can be on right.
petition for light helps, too; see smaller twigs and in the flow-
“Maintaining Madrone Health,” ering stalk. It usually devel-
page 4. In the forest, minimizing ops after bark injury. Cankers
shading and reducing competi- may spiral around the trunk or
tion will help the tree. branch, girdling and killing it.
Twig dieback Vigorous trees form a ridge of
and trunk cankers callus tissue around the margins
of the canker, limiting its spread.
These diseases are caused Rapidly spreading cankers lack
by fungi that kill the cambium calluses. Often, both twig die-
(the growth layer inside the back and trunk cankers are pres-
bark). The bark initially looks ent on the same tree. Some trees
discolored, then peels off, affected by these diseases may
revealing blackened, cracked decline rapidly and die in a year
wood that almost looks as if or two. More vigorous trees may
it’s been burned. Madrone twig persist with multiple cankers for
dieback (Figure 5) progresses years, perhaps decades.
from branch tips and works
downward. It is associated with Table 1. Diseases of madrone.*
drought and is especially com-
mon in years following heavy Disease category Pathogen Disease name
flowering and berry production.
Root rots Pythium spp. Damping-off
Figure 5 (above). Often associated
with moisture stress, madrone twig Phytophthora cactorum Collar rot or basal canker
dieback is a fungal disease that
progresses from branch tips down- Phytophthora cinnamomi** Phytophthora root rot
ward into the rest of the tree.
Armillaria spp. Armillaria root disease

Heterobasidion annosum Annosus root rot

Twig dieback Neofusicoccum arbuti Madrone canker
and (Nattrassia mangiferae,
branch cankers Fusicoccum arbuti,
Hendersonula toruloidia)

Botryosphaeria dothidea Madrone twig dieback
(Fusicoccum aesculi)

Wood-decay Phellinus igniarius Brown top rot
fungi Fomitopsis cajanderi

Figure 3 Poria subacida Yellow root rot
(above left).
Madrone with Foliage diseases Ascochyta hanseni Leaf spot
foliage blight.
Coccomyces quadratus Tar spot
Figure 4
(above right). Cryptostictis arbuti Leaf spot
A closeup view
of the foliage Didymosporium arbuticola Leaf spot
blight. Though
it looks bad, it Diplodia maculata Leaf spot
won’t kill the
tree; note the Disaeta arbuti
healthy green
bud. Elsinoe mattirolianum Spot anthracnose

Exobasidium vaccinii Blister blight

Mycosphaerella arbuticola Madrone foliage blight

Phyllosticta fimibriata Leaf spot

Pucciniastrum sparsum Rust

Rhytisma arbuti Speckled tar spot

*Adapted from Elliott (1999) ** Hansen (unpublished)

2 Diseases and Insect Pests of Pacific Madrone

Deep waterings may help or two on flat or
prevent twig dieback (but see
cautions below, in discussion poorly drained
of root diseases). Minimizing
bark injury is the key to pre- ground and/or
venting cankers. Madrone bark
is so thin, it is easily damaged heavy clay soils is
by sunscald (when the trunk is
suddenly exposed to sun) or by a recipe for trouble.
mechanical wounding. Trunk
wraps can protect against sun- While some indi-
scald if placed on the tree before
it’s exposed to direct sun. vidual madrone

Once diseases are established trees may do all
in the main stem, there’s not
much you can do: no fungicide right in these situ-
is known to be effective. If
caught early, however, pruning ations, the risk of
and burning individual cankered
branches, shoots, and flowering developing root
stalks seems worthwhile. If the
canker is partway up a branch, disease is much
cut it 1 foot or so below the vis-
ible canker margin to include higher. On the Figure 7. Root disease
any fungus that may have spread
into the wood. other hand, deep (Phytophthora) canker

Madrone root diseases waterings every near ground line. Photo:

These diseases affect the roots 2 weeks or so, Ralph Byther, Washington
and tree trunk. Cankers (areas of
diseased tissue) are usually near underneath the drip State University.
the base of the tree (Figure 7)
but may be farther up the trunk. line but well away
Infected bark is brown, and sap-
wood also may be discolored. from the trunk, may promote
Loss of foliage and small, curled
leaves are common symptoms. tree vigor during extended sum- Figure 8. Young madrone infected by
Infected trees often die, some- P. ramorum. This leaf and shoot/stem
times rapidly. Moist soil condi- mer dry spells. blight often follows the midrib and peti-
tions favor the fungus; hence, ole (connecting stem) of the leaf. Photo:
overwatered trees or trees grow- Sudden Oak Death P. Maloney and D. Rizzo, University of
ing in poorly drained soils are California, Davis.
most susceptible. Pacific madrone is a host spe-
cies for the fungus Phytophthora
Other root diseases, such as ramorum, that causes Sudden
Armillaria, are typically associ- Oak Death. The disease has
ated with root wounding (e.g., not been detected on madrone
during trenching) and with poor in Oregon, however. Like the
tree health. These are most com- foliage and canker diseases
mon on older trees. described above, the Sudden
Oak Death fungus causes leaf
The main way to avoid root spots (Figure 8), leaf death, and
disease problems is to avoid branch dieback. Diagnosis is
overwatering. In home land- difficult: individual trees may
scapes, watering every day be infected by P. ramorum and
other fungal pathogens at the
same time. In Oregon, P. ramo-
rum is confined at this time to an
area in southern Curry County,
in and around Brookings.

Wood-decay fungi

Wood-decay fungi typically Figure 9. Madrone with heartwood decay is excellent
invade madrone through habitat for a number of cavity-nesting species such as
wounds, either from mechani- woodpeckers, owls, bats, and small mammals. Note the
cal injury, as from pruning, or cavity hole at the top and extensive decay exposed at
caused by cankers. The presence the butt of the tree.
of wood-decay fungi in a tree
often is obvious; for example,
exposed heartrot (Figure 9) or
conks (shelflike, fruiting bodies
of the fungi). Decays usually are

Diseases and Insect Pests of Pacific Madrone 3

not considered a major factor in trees that pose no risk to people California but isn’t considered a
major pest. However, the white,
poor tree health, but they can be or property, heartrot may be waxlike covering on the psyllid
nymphs (the immature insect)
important in large, old trees near desired for wildlife values. makes them obvious and may
alarm people.
houses or in recreation areas.
Several moth caterpillars feed
Madrone can remain standing Madrone Insect Pests on madrone by mining the leaf,
with extensive heartrot for long eating only its interior and not
the epidermis. Some cause sinu-
periods, though heavy snow Insects normally are not ous mines (Figure 11), others
loads might result in extensive a serious threat to madrone are blotch miners, and one is a
breakage. Unless the tree is a health. Insect pests of madrone blotch miner that cuts elliptical
potential hazard, it usually is not (Table 2, page 5) include the holes in the leaf after it finishes
important to remove it. fall webworm and western tent mining. The final injury looks
caterpillar, aphids, and leaf min- like paper punch holes. Dam-
Proper pruning, avoiding ers. The western tent caterpillar age is usually minor from these
wounds, and maintaining good is uncommon on madrone but insects, and no controls are
health help avoid wood decays. can occur on it. The fall web- necessary.
Madrone is known as a good worm is much more common on
wildlife tree, because heartrot madrone in southwest Oregon Wood-boring beetles may
creates habitat for cavity-nesting (Figure 10). Both form tents, in invade madrone wood that is
birds and animals. Therefore, in exposed by injury or cankers,
but the beetles are most impor-
which the caterpillars rest and tant and noticeable in dead
material, especially firewood.
feed. The western tent caterpil- Two roundheaded woodborers
are common: the western ash
lar tents are most obvious in late borer and the oak cordwood
borer. These insects are known
spring and early summer; fall to arrive at firewood piles
within hours of cutting during
webworm tents are more com- spring and summer, and they
can seriously riddle the wood
mon in late summer and early (Figure 12). Adults may emerge
from firewood inside the home,
fall. but the beetles are not harmful to
people or houses.
These pests are easily con-
Maintaining
trolled by pruning and rarely Madrone Health

cause significant damage. Trees In forestland, ensuring that
madrone has adequate sunlight
that are defoliated may have will help promote its vigor and
longevity. Adequate sunlight
Figure 10. Fall webworm feed- smaller leaves the following means full sunlight from above
and at least partial light from the
ing on madrone foliage. Though year. sides. This may require remov-
ing overtopping and/or sur-
unsightly, fall webworm seldom Aphids may attack leaves rounding trees.

causes significant damage or and terminals of madrone, and In landscape, park, or home
mortality. Photo: Don Goheen and their feeding can cause some settings where shade is not an
Ellen Michaels Goheen, USDA leaf curling. The pale green
Forest Service, Pacific Northwest aphid produces copious “honey-
Region. dew,” which coats leaves and

gives them a

sticky look

and feel. The

best control

for aphids is

to knock them

off, either by

hand or with a

Figure 11. Madrone leaf damaged Figure 12. Western ash borer. Adults strong stream
by a sinuous leaf miner. sometimes infect dead or nearly of water.
dead madrone that is cut during
the insects’ flying period, from late The mad-
spring through summer, but the bor- rone psyllid
ers do not pose a threat to live trees. is common
Photo: John Davis, Stevenson, WA. around flowers
on madrone in

4 Diseases and Insect Pests of Pacific Madrone

issue, avoiding site disturbance Table 2. Insect pests of madrone.
within the critical root zone is
key to maintaining tree vigor. Insect families Pest Common name
The critical root zone is the area
within the tree’s drip line. (Note, Aphids/Psyllids Wahlgreniella nervata Pale green aphid
however, that the tree’s roots Madrone psyllid
may extend well beyond its drip Wood boring beetles Euphyllura arbuti Western ash borer
line.) Avoid piling soil over the (Roundheaded wood borers) Neoclytus conjunctus Oak cordwood borer
existing soil surface, trenching, Xylotrechus nauticus Sinuous leaf miner
or soil compaction in this criti- Paper punch miner
cal zone and, if possible, even Blotch and Marmara arbutiella Fall webworm
beyond it. Western tent
Serpentine leaf miners (moths) Coptodisca arbutiella caterpillar
As noted above, avoid fre-
quent, light waterings and, Defoliators and Hyphantria cunea
especially, letting water directly Leaf chewers (moths)
contact the tree trunk. Deep, Malacosoma
infrequent waterings away from californicum pluviale
the trunk but within the criti-
cal root zone may promote tree For More Information
vigor during severe drought peri-
ods. In most cases, fertilizer is Adams, D. and K. Kosta. 1993. Maloney, P.E., S.C. Lynch,
not necessary or recommended, Madrone canker in California. S.F. Kane, and D.M. Rizzo.
because it may stimulate foli- Tree Notes, No. 16. California 2004. Disease progression
age growth, resulting in greater Department of Forestry and of Phytophthora ramorum
moisture stress. Mulching within Fire Protection. Sacramento, and Botryosphaeria dothidea
the critical root zone will help CA. http://ceres.ca.gov/ on Pacific madrone. Plant
conserve moisture and improve foreststeward/pdf/treenote16. Disease 88: 852–857.
soil conditions. However, avoid pdf
piling up mulch against the tree Oregon Department of Forestry,
trunk. Elliott, M. 1999. The decline Forest Health Management.
of Pacific madrone (Arbutus http://egov.oregon.gov/
Because madrone has thin, menziesii Pursh.) in urban ODF/PRIVATE_FORESTS/
easily injured bark, especially and natural environments: fh.shtml
if the tree is growing in shade, its causes and management.
avoid suddenly exposing the M.S. thesis, University of Southwest Oregon Forest Health
trunk and branches to full sun- Washington, Seattle. Protection Service Center,
light. To avoid this, thin out sur- U.S. Forest Service, Central
rounding trees in fall or winter, Furniss, R.L. and V.M. Carolin. Point, OR.
or cut down neighboring trees 1977. Western Forest Insects. http://www.fs.fed.us/r6/rogue/
gradually, or wrap the area of USDA Forest Service, swofidsc/
the lower trunk with arborist tree Miscellaneous Publication
wrap. No. 1339. Washington, DC.

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