Monitoring Host Selection Behavior and Progression of an Infestation
Infestation by the Mountain Pine Beetle, Dendroctonus ponderosae Hopkins (Coleoptera
(Coleoptera:: Scolytidae),
Scolytidae),
in Mixed Stands of Limber Pine, Pinus flexilis James, and Lodgepole Pine, Pinus contorta latifolia Engelmann.
Diana K. Dean 1, Timothy R. Collier 1, David Legg 1, Elise G. Pendall 1, Steven J. Seybold 2
1
University of Wyoming, Laramie, Wyoming, 2 USDA Forest Service PSW, Davis, California
Objectives
Assess mortality caused by mountain pine beetle (MPB) in mixed stands
limber and lodgepole pines in 2003, 2004, and 2005.
Assess emergence density of MPB from both pines in 2005
Monitor seasonal flight behavior of MPB in the mixed stands in 2004
and 2005
What is MPB seasonal flight behavior in mixed stands
of limber and lodgepole pines?
Two funnel traps were set up outside the perimeter of each of the ten
plots in 2004 (May 7th) and 2005 (June 3rd). In 2004, a three
component bait consisting of terpinolene, trans-verbenol and
exo-brevicomin was attached to each trap. In 2005, the trap procedure
Do more MPB emerge from limber pine than from lodgepole pine?
was repeated except trans-pityol was inadvertently used instead of
Is there a difference between lodgepole and limber pine mortality?
trans-verbenol as the female pheromone component of the bait.
In 2004, we trapped the first MPB during the week of June 19th and
During the last decade, the mountain pine beetle (MPB) has
Total Beetles Collected per Cage
the last MPB the week of Oct. 30th . In 2005, we trapped the first MPB
developed elevated populations in the “white pines”, including
during the week of July 1st and the last MPB the week of Oct. 3rd
limber pine. Little is known of the behavior of MPB in limber
(Fig. 11). The attenuated flight in 2005 is likely the result of the
pines, and even less is understood about their activities in mixed
trans-pityol. trans-Pityol is the female pheromone attractant for twig and
stands that include limber pine. Our study focused on mixed
cone beetles. NOTE: The number of twig beetles in the traps did triple
stands of limber and lodgepole pines in southeastern Wyoming
Lindgren funnel trap
in 2005 when compared with 2004. The sex ratios of MPB collected throughout each season
Comparison of Diameter Classes Across All Plots (measured in 2004)
were dissimilar between the two years. In 2004 the ratio of males to females was 1:1.5
1 2 3 4 5 6 7 8 9 10
whereas in 2005 the ratio of males to females was 1:3.3, probably the result of different
Emergence Cage Number
female pheromones (Fig.
Comparison of 2004 and 2005 Trap Collections
MPB attacked limber pine in the Medicine Bow National Forest
12). Comparing sex ratios
Limber Lodgepole
of MPB from funnel traps
Area underneath emergence cage
Fig. 6
(Medicine Bow National Forest) using ten 0.13 ha plots.
and emergence cages for
Twenty trees, 10 lodgepole and 10 limber, were randomly selected from the
Each plot had at least three attacked limber pines in 2003
2005 show very different
periphery of five of the ten plots in 2005. Emergence cages, covering 0.3 m2
with emergence from these trees in 2004. An analysis of
results: funnel traps 1:3.3
each were attached to these 20 trees.
the distribution of diameters of trees of both species in
(male:female), and
Emergence Cage on lodgepole
Emergence Patterns: In seven of the ten cases, more
2004 (Fig. 1) showed that: 1) many more lodgepole
emergence cages 1:1.63
Lodgepole: Seasonal Emergence Across all Cages by Gender
MPB emerged from limber pine than from lodgepole
than limber pines were in the plots; 2) the greatest
Limber
Diameter Size Class
and 1:1.45 limber and
Lodgepole
400
pine (Fig. 6). Overall emergence density, male
frequency of both species were between 5 and 20 cm in
st
350 1 Lodgepole:
lodgepole, respectively.
300
emergence density and female emergence density varied
Fig. 1
diameter; and 3) the largest diameter trees in the
250
However, the comparison
200
by host species (Table 1). In addition, emergence
stands were limber pine. The mean density of trees (no./ha) across all plots was 1018; mean basal area (m2/ha) was
150
Week of Collection
of
2004 funnel traps to
varied by gender as well as by date from the two
100
35.2. Mean density and basal area of limber pine were 193 trees/ha and14.1 m2/ha, respectively. Corresponding
50
0
Fig. 11
measurements for lodgepole were more than three times (683) and more than 40% higher (20.1), respectively.
Comparison of Sex Ratios from Trap and Emergence Cage Collections (2004 and 2005)
Limber
Lodgepole
Limber
Lodgepole 2005 emergence cages shows a
As the outbreak progressed over time, host species selection began to shift from limber to lodgepole pine
MPB
Mean
Mean
Emergence Emergence
noteworthy similarity (Fig. 12).
1:3.3
Collected
Collected
Dates
Dates
3.5
(Fig. 2, red ovals). Between 2004 and 2005, the
Tree Mortality Caused by MPB
Date of Collection
2
In 2005 MPB were collected in
(no./0.3 m ) (no./0.3 m2)
incremental number of attacked lodgepole surpassed
3
196
Male
Female
July 8th
June 17th traps from July 1st through
180
Male
the number of attacked limber, which was the initial
through
through
rd
60.3
25.9
Fig. 7
2.5
Sept. 16th
Sept. 9th Oct. 3 and emergence was June
preferred host. Still, the 2005 cumulative attack ratio
144
th
June 24th
June 10th 10 (lodgepole) through Sept.
132
Limber: Seasonal Emergence Across All Cages by Gender
126
1:1.63
1:1.5
for lodgepole was much less (1:14.2)
2
Female
through
through 23rd (limber). But, in 2004 trap
1:1.45
94.5
35.5
108
rd
th
Sept.
23
Sept.
7
(attacked:unattacked) than for limber (1:1.7). As a
400
st Limber:
collections
were
more
compatible
1
1.5
Total
69
166.5
69.2
64
300
result, the intermediate and larger diameter classes of
54
with emergence of 2005: June
48
Table 1
39
39
200
36
1
limber pine were eliminated from the stand (Fig. 3), in
27
host species (Fig. 7 and 8, Table 1). Peak emergence 19th through Oct. 30th
18 18
100
5
00 4
00 5
9
9
05
6 10
s 2 00
ps 2
ps 2
contrast to lodgepole pine, which still had a substantial
es 20
a ge
Tra
Tra
0
was the week of Aug. 12th for both sexes from
. Cag
(Figs. 7, 8 and 11).
E. C
le E
ber
gepo
Lim
number of trees in the intermediate diameter classes
Lod
n un un Ju l Ju l ul ul ul ug ug ug ug e p e p ep ep
Year of Attack
both
host
species.
The
sex
ratio
of
emerging
beetles
u
J
J
J
S
S
-J -J -J 1
8 1 5- 2 2- 2 9- 5 -A 2-A 9-A 6-A 2 - 9 - 6-S 3-S
2
1
10 17 24
(Fig. 4).
2
1
1
changed over time; and, the sex ratio also varied
Fig. 12
Limber
Lodgepole
Limber Cumulative
Lodgepole Cumulative
Cumulative (both species)
Conclusions:
Date of Collection
by host species (Fig. 9). However, the overall sex
ƒ Limber was the initial preferred host in the mixed stands of limber/lodgepole
Male
Female
Fig. 2
ratio was virtually identical between the two host
ƒ Several critical intermediate and large diameter size classes of limber were almost
Fig. 8
At the end of the 2005 field season, a series of statistical
species: 1:1.45 (males:females) for lodgepole and
eliminated from these mixed stands, likely impacting succession
analyses (Pearson’s χ2 statistic) within diameter class showed
1:1.63 (males:females) for limber (Fig. 12).
ƒ This study suggests a possible shift in host preference from limber pine to lodgepole pine,
the cumulative percentage of limber pine attacked was
Comparison of Sex Ratios Across Seasonal Emergence
but a longer term study would clarify the progress of the infestation
significantly larger in four of eight classes analyzed (Fig. 5).
ƒ In 7 out of 10 cases more MPB emerged from limber than from lodgepole
Two other classes only had attacked limber pine in them.
2.5
ƒ The mean number of emerged MPB males was higher in limber than in lodgepole
2
The most notable differences were in the intermediate diameter
1.5
ƒ The mean number of emerged MPB females was higher in limber than in lodgepole
classes. Specifically:
1
Fig. 3
ƒ MPB emergence periods varied between limber and lodgepole but peak emergence was
0.5
ƒ In the 25-30 cm class 92% of the limber and
0
identical
21% of the lodgepole were killed
ƒ Correlation between MPB emergence and MPB flight period is likely, but cannot be proven
ƒ In the 30-35 cm class 96% of the limber and
with this data
38% of the lodgepole were killed
Evaluate sex ratios of flying and emerging MPB in mixed stands in 2005
N u m b e r C o lle c te d
300
2 50
200
150
10 0
50
0
200
180
160
120
1200
100
80
1000
Number Collected
Number of Trees
140
60
40
20
<
5
5-1
0
10
-1
5
15
-2
0
20
-2
5
25
-3
0
30
-3
5
35
-4
0
40
-4
5
45
-5
0
50
-5
5
55
-6
0
60
-6
5
65
-7
0
70
-7
5
>7
5.0
0
800
600
400
200
of Ju
ne
1st w
k of
Ju ly
wk of
July
3rd
wk of
July
4th
wk o
f Ju
ly
5th
wk o
f Ju
ly
1st w
k of
Aug
.
2nd
wk o
f Aug
.
3rd
wk of
Aug
.
4th
wk o
f Au
g.
1st w
k of
Sept
.
2nd
wk of
Sep
t.
3rd
wk of
Sep
t.
4th
wk o
f Sep
t.
1st w
k of
Oct.
2nd
wk of
Oct.
3rd
wk of
Oct
.
4th
wk of
Oct
.
Males 05
Females 05
-J
u
24 n
-J
un
1Ju
l
8Ju
15 l
-J
ul
22
-J
u
29 l
-J
ul
5Au
12 g
-A
ug
19
-A
u
26 g
-A
ug
2Se
p
9Se
p
16
-S
ep
23
-S
ep
-J
10
Fe males 04
17
un
Male s 04
2nd
4th
wk
3rd
wk of
N u m b e r C o lle c te d
June
0
Sex Ratio (M :F)
200
18 0
14 0
12 0
10 0
80
60
40
20
0
B e f o re 20 0 3
2003
2004
2005
N um b er C o lle cte d
N u m b e r o f T re e s
16 0
Limber: Comparison of 2004 Diameter Distribution with Cumulative Distribution of
Attacked Trees in 2005
70
Number of Trees
60
50
40
30
20
10
Sex Ratio (M:F)
5-1
0
10
-1
5
15
-2
0
20
-2
5
25
-3
0
30
-3
5
35
-4
0
40
-4
5
45
-5
0
50
-5
5
55
-6
0
60
-6
5
65
-7
0
70
-7
5
>7
5.0
<
5
0
Diameter Size Class
T otal Limber
At tacked Limber
Lodgepole: Comparison of 2004 Diameter Distribution with Cumulative Distribution of
Attacked Trees in 2005
200
un
17
-J
un
24
-J
un
1Ju
l
8Ju
l
15
-J
ul
22
-J
ul
29
-J
ul
5Au
12 g
-A
ug
19
-A
u
26 g
-A
ug
2Se
p
9Se
p
16
-S
ep
23
-S
ep
180
10
-J
160
Number of Trees
140
120
100
80
60
40
20
5
<
5-1
0
10
-1
5
15
-2
0
20
-2
5
25
-3
0
30
-3
5
35
-4
0
40
-4
5
45
-5
0
50
-5
5
55
-6
0
60
-6
5
65
-7
0
70
-7
5
>7
5.0
0
Date of Collection
ƒ In the 35-40 cm class 89% of limber and 35%
of the lodgepole were killed
Lodgepole
Limber
Fig. 9
Diameter Size Class (in cm)
T ot al Lodgepole
At tacked Lodgepole
Fig. 4
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
ns
ns
50
-5
5
55
-6
0
40
-4
5
45
-5
0
35
-4
0
30
-3
5
25
-3
0
Acknowledgements
20
-2
5
Percentage
Comparison of Percentage of Attacked Trees for Both Pine Species by Diameter Class
(Before 2003 through 2005)
Diameter Size Classes (in cm)
Lodgepole
Future Directions:
The apparent fidelity to limber pine in the mixed stands, along with the
reproductive success of MPB in limber, suggests a mechanism based on an
underlying nutritional component and/or possible host race formation. The
nutritional component was explored using stable isotope analysis. Results from
this work will be available soon.
Limber
Fig. 5 Cumulative (before 2003-2005) percentages of attacked trees were compared by
species within diameter class by using a 2 X 2 contingency table (Pearson’s χ2 statistic).
Star denotes a significant difference within diameter class, ns = not significant, α=0.05.
NOTE: There were no lodgepole pines in the two largest size classes; the 40-45 cm size
class had only two lodgepole pines, tending to skew results.
Area of Medicine Bow National Forest
Woodpecker predation of MPB on limber pine
Stand containing plot 2 in the Medicine Bow National Forest
University of Wyoming: Richard Olson, Scott Schell, Kirk Van Dyke
USDA Forest Service FHP: Willis C. Schaupp, Jr., Rapid City, S.D., JeriLyn Harris, Robert Cain,
Kelly Sullivan-Burns, Jeff Witcosky, Lakewood, CO
John Schmid, Fort Collins, CO.
Jana C. Lee, USDA Forest Service PSW, Davis, California
Jose F. Negron, USDA Forest Service RMRS, Fort Collins, CO
USDA FS Forest Health Monitoring Funds Grant #INT-EM-05-04