Western balsam bark beetle use of spruce-fir blowdown in Wyoming
Kurt K. Allen, Daniel F. Long, Joel D. McMillin & Jose F. Negron, R2 FHP, Rapid City, SD and RMRS, Ft. Collins, CO
Introduction
16
Broo d/36 in 2
Mid top
Mid bot
Crow n top
Crow n bot
Figure 9. We stern balsam bark beetle brood in baited vs. unbaited
felled fir on the Bi ghorn Na tional Forest.
New Adults
Un
Larvae
Pupae
Cr
ow
n
id
M
H
DB
Tree Location
Figure 10. Total number of brood found in samples taken
from different locations on felled fir.
0
Eggs
m
d
i te
ba
Ba
it e
d
1
0.5
tto
1.5
p
2
18
16
14
12
10
8
6
4
2
0
Bo
2
Total brood/36 in
DBH bot
To
Larvae
Pupae
Life stage
2.5
Figure 2. Locations of study sites (red shaded
areas) on the Bighorn and Shoshone National
Forests.
6
Bo le Pos ition
1. Does western balsam bark beetle successfully attack and
produce brood in downed fir?
Answers to these questions should be applicable to many areas of
the central and northern Rockies where there are extensive
stands of predominantly subalpine fir, blowdown events have
occurred and western bark beetle is present.
8
DBH top
Figure 4. Life stage of western balsam bark
beetle brood in felled trees on the Shoshone NF
(September 2001).
4. What is the life history of western balsam bark beetle in
blowdown?
Unbaited
10
0
Study Objectives
3. Does brood production vary by the location on the bole?
Baited
12
2
Eggs
2. Do pheromone baits increase the number of brood in felled
trees?
14
4
Tota l brood/ 3 6 in 2
Brood/ 36 in2
Western balsam bark beetle (Dryocoetes confusus Swaine)
attacks subalpine fir (Abies lasiocarpa) throughout western
North America (Furniss and Carolin 1980). However, little is
known about factors contributing to outbreaks of this species
(McMillin et al. 2001). Tree blowdown is known to trigger
outbreaks of certain bark beetles, such as spruce beetle
(Schmid and Frye 1977), but has not been examined for
western balsam bark beetle. This is despite observational
studies having found outbreaks of this beetle adjacent to areas
of tree blowdown (Figure 1).
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
New A dults
Life stage
25
2.5
2
1.5
1
0.5
n
ro
w
C
id
M
H
DB
Bo
tto
m
p
To
nb
a
U
10
ite
d
0
15
B
ai
te
d
Brood/ 36 in2
20
3
Attacks/72 in 2
Figure 5. Life Stage of western balsam bark beetle
brood in felled trees on the Bighorn National Forest.
5
0
DBH - top
DBH - bot
Mid - top
Mid - bot
Crown top
Crown bot
Tree Location
Figure 11. Number of attackes at different locations on
felled fir (both forests combined).
Bole position
The studies were conducted on the Bighorn and Shoshone National
Forests, Wyoming (Figure 2). The areas are characterized by
mixed stands of SAF, Engelmann spruce and lodgepole pine.
1. Five trees were felled at each of four locations on both the
Bighorn and Shoshone National Forests in early July 2001
(Figure 3).
2. At half of the locations the felled trees were baited with exobrevicomin and the other locations were not baited.
3. In September 2001 trees were sampled for the number of brood
by life stage in 36 in2 taken from the top and bottom aspect at
DBH, mid-bole, and the upper crown.
4. The number of initial attacks were also recorded in 72 in2 taken
from the top and bottom aspect at DBH, mid-bole and upper
crown .
5. Brood sampling will be repeated in the spring, summer, and fall
2002 to determine the life cycle of this beetle.
Conclusions
Brood/36 in2
6
Results
5
•Based on the preliminary data, we conclude that western
balsam bark beetle takes advantage of storm events that
create downed host material.
4
3
2
1
0
•Western balsam bark beetle attacked and brood are
developing in the felled trees (Figures 4 – 11).
DBH top
• Most of the brood in felled trees were in the larval stage
(Figure 4) or egg and larval stages (Figure 5).
• Pheromones did not increase the number of brood in
felled trees (Figures 8 – 11).
•.The mid-bole portion of felled trees had more brood than
lower or higher on the bole on the Shoshone National
Forest (Figures 6), but there was no difference on the
Bighorn National Forest (Figures 7).
• More brood were found on the bottom aspect of the
felled trees than the top for both forests combined (Figure
10).
• Higher numbers of brood were found in the felled trees
on the Shoshone than the Bighorn National Forests
(Figures 4 – 11).
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DBH bot
Mid top
Mid bot
Bole Position
Crown top Crown bot
Figure 7. Western balsam bark beetle brood in felled fir on the
Bighorn National Forest.
25.00
2
Methods and Materials
Figure 3. Felled fir susceptible to western
balsam bark beetle attack.
Brood/ 36 in
Figure 1. Subalpine fir mortality caused by western balsam
bark beetle adjacent to area of blowdown on the Bighorn
National Forest.
Figure 6. Western balsam bark beetle brood in
felled fir on the Shoshone N F (Sept. 2001).
20.00
15.00
• This suggests that prompt management of downed
material is needed to reduce the likelihood of subsequent
western balsam bark beetle outbreaks.
• Furthermore, intentional felled trees could possibly be
used in a trap tree approach to reduce local populations of
western balsam bark beetle similar to strategies used for
spruce beetle.
Bait
No bait
Literature Cited
10.00
5.00
Furniss, R.L. and V.M. Carolin. 1980. Western Forest Insects. USDA
Forest Service Misc. Publication 1339.
0.00
DBH - top DBH - bot Mid - top
Mid - bot
Bole position
Crown top
Crown bot
Figure 8. Western balsam bark beetle brood in baited
vs. no bait felled fir on the Shoshone NF.
| FHM 2002 Posters
McMillin, J.D., K.K. Allen, J.L. Harris and D.F. Long. 2001. Stand level
impact of subalpine fir decline in spruce-fir forest type of the north-central
Rocky Mountains. USDA Forest Service Technical Report R2–65.
Schmid, J.M. and R.H. Frye. 1977. Spruce Beetle in the Rockies. USDA
Forest Service, Rocky Mountain Forest and Range Experiment Station,
General Technical Report RM-49. 38 p.