Extent and Severity of Balsam Woolly Adelgid
(Adelges piceae (Ratzeburg)) Damage
to Eastside Washington and Oregon Forests
Year 1 of 2 Year Project Grant, WC-F-07-01 Authors: Lia Spiegel1. Kris Chadwick2, Connie Mehmel3
USDA Forest Service, Forest Health Protection
1. La Grande, Oregon
2. Bend, Oregon
3. Wenatchee, Washington
OBJECTIVES:
1. Determine the extent and severity of
damage and mortality to subalpine fir
(Abies lasiocarpa (Hook.) Nutt.) from
balsam woolly adelgid.
2. Assess the management options available
to promote resistance and/or regeneration
that will ensure the long-term viability of
subalpine fir on the landscape.
METHODS:
PRELIMINARY RESULTS:
Plot centers are marked
with orange plastic
stakes (lower right).
All trees and snags
larger than 5” dbh
are tagged.
In the fall of 2007 we
installed permanent
fixed plots in 13 subalpine fir stands distributed throughout
Photo by C. Yenney,
Yenney,
FHP Wenatchee
Wenatche
eastern Oregon and
Washington. Each
plot is 0.1 acre in size
(37.2 feet in radius), with a smaller plot (0.02 acres, 16.7 feet in radius) nested at the same
center. In order to characterize stands of interest, we
have recorded the following information:
All areas surveyed have yielded surprises.
• In the eastern Cascades, adelgid infesta­
tions may not be as widespread as re­
ported. Stands examined in northern
Washington revealed no BWA infestations.
Damage reported by aerial survey was ap­
parently caused by other agents, most
prominently Cytospora canker and Pityok­
teines minutus. P. minutus, while in the
“twig beetle” group, appears to be acting
as a tree killer in these drought-affected
stands.
• Plant association
• Disturbance history
• Stands examined in northeastern Oregon
are very severely infested. Areas recorded
as free of BWA in 2000 now all have wide­
spread infestations. Some stands had so
few subalpine fir over 5” in diameter still
alive that plot locations had to be adjusted.
• Height, diameter and species of all trees or snags
greater than or equal to five inches in diameter on
the large plot
• Height, diameter and species of all trees greater than
or equal to one foot tall but less than five inches in
diameter on the small plot
BACKGROUND:
• Tree status on the large plot
(Standing/Blowdown/Live/Dead/Snag Condition)
The balsam woolly adelgid (BWA) is a tiny sucking
insect that was introduced into North America from
Europe around 1900. It feeds on the stem, branches and
twigs of true firs (Abies spp.). During feeding, the
insect injects a salivary substance into the host tree
which causes branch calluses and abnormal wood for­
mation. Heavy bole infestations usually kill the tree.
Branch and twig infestations cause gouting which pro­
gressively weakens the tree. Tops become curled or
“fiddle-shaped,” and portions of the crown may die.
• Live crown ratio
• Double the number of plot installations in 2008.
• Age from increment core (one fir in each five-inch
diameter class)
• Continue long term monitoring of established plots.
Photo by L. Spiegel,
FHP LaGrande
• Evaluate management options for subalpine fir.
• Radial growth for the last 10 years
• Evaluate the relationship of crown severity and gout­
ing severity as measures of BWA impact.
The following data are used to characterize adelgid
severity:
Relationship of Crown Severity and Gouting Severity Ratings Central Oregon and Blue Mountains Plots
• Stem Infestation Density
– an estimate of the number of adelgids found on the bole 10
Crown Severity
Gout
9
8
7
Numerical Rating
BWA damage to subalpine fir:
Tree in the center has typical “fiddle shaped” crown.
FUTURE WORK:
• Crown Severity Rating – percentage of the crown damaged or killed by
BWA
6
5
4
3
2
1
0
• Gouting Severity –
number of nodes on a branch affected by BWA
3 Creeks
Lake
Black Butte CASCADE
LAKES
HWY
Eagle
Creek
Moss
Springs
North
South
Van Patten North Fork
Strawberry Strawberry
Location
CROWN SEVERITY = Amount of the crown damaged or killed by BWA. Maximum value is 12.
GOUT = Number of nodes on a sample branch with gouting from BWA.
Okanogan National Forest
Heavy stem infestation of BWA:
Note the cottony appearance
Sweet Grass
Plots
Deer Creek
Plots
!
(
!
(
Photo by C. Mehmel,
FHP, Wenatchee
Because the impact on the host is sometimes subtle
and the insects are only visible for a short time, FIA and
CVS plots probably underreport the incidence of balsam woolly adelgid. Plot remeasurements occurring be­
tween 1997-2004 in Region 6 documented little or no
adelgid activity in many forests while aerial surveys
documented thousands of acres of increasing damage in these same forests. While mortality in these areas is widely recognized, the
impact on the landscape is not understood. Winthrop
.
!
Declining crown
with pronounced
lichens are a
signature used by
aerial survey to
identify BWA
Photo by
R. Flowers, OR Dept.
of Forestry
2007 Balsam Woolly Adelgid Survey Areas
O K A N O G A N
Twisp
N F
.
!
Legend
Plots without BWA
Plots with BWA
Okanogan
National Forest Lands
Colville
±
Legend
!
(
!
.
Plot Areas
Cities
BWA delineated by Aerial Survey
Wenatchee
Subalpine fir type
National Forest Boundaries
W E N AT C H E E
Olympic
N F
4
2
0
4 Miles
W
WA
AS
SH
H II N
NG
GT
TO
ON
N
Falls Creek
Plots
Gifford
Pinchot
161 spur
Plots
!!
(
(
Brians Butte
Plots
!
(
Umatilla
Balsam woolly adelgid adult.
Central Oregon
±
Photo from USDA FS archives
WallowaWhitman
Mt.
Hood
Black Butte
Plots
Blue Mountains
O C H O C O
N F
!
(
La Grande
.
!
Moss Springs
Plots
Ochoco
Siuslaw
!
(
Malheur
Willamette
Deschutes
±
Winema
.
!
Fremont
Siskiyou
Legend
!
(
!
.
Plot Areas (contain BWA)
40
Cities
20
0
Eagle Creek
Plots
O
OR
RE
EG
GO
ON
N
Rogue
River
Sisters
Union
.
!
40 Miles
!
(
Van Patten
Plots
North Fork
Plots
UM AT I L L A
N F
!
(
!
(
BWA delineated by Aerial Survey
Subalpine fir type
National Forest Boundaries
Baker
.
!
WA L L O WA ­
W H I T M A N
N F
W I L L A M E T T E
N F
D E S C H U T E S
3 Creeks Lake
Plots
Fir with flagging
caused by
Cytospora abietis.
In Washington,
cytospora was
sometimes mistaken for BWA damage during aerial survey.
N F
!
(
Branch gouting from BWA infestation.
Impact is sometimes subtle.
Photo by J. Hadfield, FHP Wenatchee
Cascades Lakes Highway
Plots
!
(
2
1
0
2 Miles
Photo by D. Carlson,
FHP Wenatchee
M A L H E U R
N F
Prairie_city
.
!
Unity
.
!
Legend
!
(
Plot areas (with BWA)
!
.
Cities
North Strawberry
Plots
±
BWA delineated by Aerial Survey
!
(
Subalpine fir type
South Strawberry
Plots
!
(
National Forest Boundaries
10
5
0
10 Miles