Page 10-March 1996
Western Forester
Whafs Troubling the Douglas-fir? Swiss Needle Cast By Alan Kanaskie, Randy Johnson and Everett Hansen duced on the previous year's needles
infect the newly emerging needles
in spring. The fungus grows inside
If you drive toward the northern the needle, impairing needle func­
Oregon coast in late winter and tion and reducing the tree's ability
spring, chances are that you'll to regulate water loss. Infected nee­
notice some young Douglas-fir plan· dles turn yellow or brownish-yellow
tations that are growing poorly and slid drop prematurely from the tree,
have an unusual yellow or yellow­ giving the tree crown a very sparse,
brown coloration. They are particu· yellow appearance. The impaired
larly noticeable near Tillamook, function and loss of needles, which
between the Nehalem and Nestucca in severe· cases leaves only the cur­
rivers and inland up to about 15 rent year's foliage on a tree, reduces
miles. You . might also notice that
hemlock, spruce and cedar in the
same areas appear quite green and
vigorous.
--.. ·
Healthy Douglas-fir shows a full
complement of needles.
What exactly is troubling the
Douglas-fir? This "disorder," charac­
terized by abnormally yellow nee­
dles, premature needle drop, and
poor growth, has been referred to as
the Tillamook crud, Douglas-fir
decline, and Swiss needle cast.
Several investigations have shown
the strong association of Swiss nee­
dle cast with the damage. However,
the question of why the disease has
become so severe in these areas is as
yet unresolved.
First, some background on the
disease. Swiss needle cast is caused
by the fungus Phaeocryptopus gaeu·
mannii, a pathogen native to the
Pacific Northwest which infects
only Douglas-fir. The disease cycle
begins when wind-borne spores pr­
tree growth and may cause death.
Damage is most noticeable in young
plantations, usually between the
ages of 5 to 30 years.
Reports from early this century
indicatE! that Swiss needle cast was
common· in the Pacific Northwest
and caused mild or no apparent
injury to Douglas-fir. However,
when Douglas-fir was planted in
eastern Europe, damage to these
"off-site" or exotic plantations soon
became severe (it is called Swiss
·
·
._.
March 1998 Pase 11
VVesternForester I
,,
·The tree to the right shows a thin,
sparse crown as a result of Swiss
needle east damage..
needle cast because it was first dis­
covered in Switzerland). Similarly,
Douglas-fir planted in New Zea­
land, Australia, and in the central
and eastern United States has suf­
fered significant damage from Swiss
needle cast. The damage symptoms
in the Tillamook area appear
remarkably similar to those ob­
served in these exotic plantations.
Several of the following factors
probably contribute to the current
situation near Tillamook, but few
have been substantiated:
• Douglas-fir
may be poorly
adapted to many sites in the fog
belt, since it was typically a minor
component of previous stands. This
mal-adaptation. may increase sus­
ceptibility to the disease, similar to
what has been observed in planta­
tions abroad.
• Douglas-fir
planted in the
Tillamook area may lack natural
resistance to the disease. Genetic
resistance to Swiss needle cast is
associated with seed source and
parent trees.. Many of the existing
plantations in the fog belt were
established with seed collected from
outside the fog belt because only a
limited amount of local seed ·was
available (seed yields in the fog belt
typically are poor and sporadic).
Much of the seed may have been col­
lected in the appropriate seed zone,
but from a 'higher elevation band
(over 1,000 ft.) than the area with disease-tolerant Douglas-fir fami­
high disease pressure.
lies.
• More Douglas-fir is present to­
Several investigations are under­
day in the fog belt than was the his­ way to further our understanding of
toric norm, and this area is very the problem. The Oregon Depart­
conducive to infection and disease
ment of Forestry is cooperating with
development. This in turn could
various agencies and companies to
contribute to an increase in iilocu­ determine the distribution and
lum and disease pressure.
impact of the disease along the
• Changes in recent climatic con­
north coast. Genetic resistance is
ditions or local weather patterns ·being evaluated in a cooperative
may have favored disease develop­
effort between the USDA Forest
ment.
Service PNW Experiment Station,
• The Swiss needle cast pathogen
the Northwest Tree Improvement
. in the Tillamook area may be genet­
Cooperative, and ODF. Oregon
ically different and more virulent
State.
University
has
begun
than the pathogen in other areas.
research focusing on disease ecology
• Soil and plant nutrient dynam­
and biology of the pathogen.
ics may have affected susceptibility
Although· Swiss needle cast can
to the disease or severity of damage. be found most anywhere in coastal
Options to improve the condition
Oregon and Washington, damage is
of existing damaged plantations are
severe in only a few locations at this
limited. Research to date has shown time. However, there are certainly
that fungicides are not a promising
more plantations with nOticeable
. operational treatment, and that damage now than there were 10
additions of nitrogen and phosph­
years ago. The coming year should
rus do little to alleviate damage. Ap­ provide valuli.ble information upon
plications of complete macro- and which to base management deci­
micro-nutrient mixtures are being sions.
,evaluated but results are not yet
avBilable. Favonng species ·other
Alan: Kanaskie is a forest pathol­
than Douglas-fir during thinning or ogist with the Oregon J)epu,rtrMn t of
by interplanting is recommended. Forestry, Salem. Randy Johnson is
When establishing new plantations
a genetii:ist with the USDA Forest
in areas with severe Swiss needle Service PNW Research Station,
cast, limit the amount of Douglas­ Corvallis. Everett Hansen is a pro­
fir; 1ise only seed from fog belt or fessor of forest pathology, Oregon
State University, Corvallis.
Dou"1as-tir branch shows
abnormal lou of needles due to
Swiss needle cast.
This