Forest Health Processes on the Allegheny National Forest: Integrating Aerial Survey and Plot Data
Randall Morin, Andrew Liebhold, Kurt Gottschalk, Stephen Horsley, and Eugene Luzader - Northeastern Research Station
Daniel Twardus and Robert Acciavatti - Northeastern Area State and Private Forestry
Robert White - Region 9, Allegheny National Forest
William Smith - Southern Research Station
ELM SPANWORM
SUGAR MALE DECLINE
This is a native species that is found throughout the
eastern United States and into Canada. Elm spanworm
outbreaks are relatively uncommon. Though it
periodically severely defoliates hardwoods such as ash,
hickory, walnut, beech, black cherry, elm, basswood, red
maple, and yellow birch. One year of defoliation often
has little impact, but two consecutive summers of elm
spanworm defoliation can cause dieback and even
mortality when an invasion of secondary pests occurs.
Elm spanworm is highly polyphagous and nearly all
major tree species on the ANF except yellow-poplar are
hosts. The preferred hosts for elm spanworm on the
Allegheny during this outbreak were black cherry, red
maple, and sugar maple.
This species is native and is widely
distributed in the eastern United States
and Canada. It is not considered to be a
serious pest in most areas. As larvae grow
the shelters are enlarged or reformed on
new, undefoliated branches (Craighead
1950). This progressive feeding often
defoliates entire trees, reducing radial
growth the following year and causing
rapid decline in some stands.
350000
% Black Cherry Basal Area
0 - 11
11 - 22
22 - 32
32 - 43
43 - 54
No Data
Acres Defoliated
300000
1
2
1
2
3
250000
200000
150000
100000
50000
Numerous reports of sugar maple decline or dieback have been recorded over the last 50 years. Crown
dieback and death result when one or more predisposing stress events reduce resistance to invasion by
opportunistic, secondary-action organisms that cause the death of tissues. Episodes of maple
dieback/decline have been associated with insect defoliation, drought, logging, and root freezing. In study
by Horsley et. al., sugar maple growing on the lower slopes of unglaciated sites and in any topographical
position on glaciated sites seemed unaffected or only slightly affected. In contrast, trees located on the
upper slopes of unglaciated sites were the most affected. Defoliated stands were more likely to be
unhealthy. Conversely, all stands that were defoliated did not have unhealthy sugar maple. Therefore it was
concluded that some factor or factors must by involved in making some stands more resistant to defoliation.
This resistance was attributed to foliar chemistry. Unhealthy sugar maple was found on sites with lowest
foliar Ca and Mg and the highest Al and Mn. (Horsley, S.B.; Long, R.P.; Bailey, S.W.; Hallett, R.A.; and
Hall, T.J. 2000. Factors associated with the decline disease of sugar maple on the Allegheny plateau.
Canadian Journal of Forest Research 30: 1-14)
The FHM data for the Allegheny National
Forest was used to compare live and dead sugar
maple basal area to the terrain position of the
trees and whether they had been defoliated by
elm spanworm. The most standing dead sugar
maple was located on the upper slopes
regardless of whether the areas were defoliated
or not. This suggests that the less nutrient rich
upper slopes are less suitable for sugar maple
growth. Overall mortality was greater in
defoliated stands.
7
6
Dead Sugar Maple BA/Acre (sq. ft.)
CHERRY SCALLOPSHELL MOTH
5
4
Defoliated
Not Defoliated
3
2
1
0
UPPER SLOPE
LOWER SLOPE
50000
Average Years of Cherry Scallop
Moth Defoliation
19
84
19
85
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
0
1.4
21 Plots
1.2
22 Plots
1
0.8
0.6
26 Plots
26 Plots
0.4
0.2
0
0
0-25
25-50
50-100
% Standing Dead Black Cherry BA
% Black Cherry BA
The preferred host for this species on the
ANF is black cherry. Therefore, black
cherry dominated stands are normally the
hardest hit by cherry scallopshell moth
outbreaks There was significant evidence of
a linear trend between percent black cherry
basal area and years of cherry scallopshell
moth defoliation (regression, F=14.96,
p=0.0002).
7 Plots
35
30
25
20
15
10
12 Plots
24 Plots
5
0
0
1
2
The amount of standing dead black cherry
was significantly greater in areas that were
defoliated for two years. There was
significant evidence of a linear trend
between years of cherry scallopshell moth
defoliation and percent standing dead black
cherry (one-way ANOVA, F=3.83,
p=0.0302).
Average % Black Cherry Crown
Dieback
Years of Cherry Scallopshell Moth Defoliation
7 Plots
12
29 Plots
10
8
27 Plots
6
4
2
0
0
1
2
Years of Cherry Scallop Shell Moth Defoliation
The average crown dieback value reported
for black cherry trees that were defoliated
increased as the number of years of
defoliation increased but was not
significantly different. There was
significant evidence of a linear trend
between years of defoliation and black
cherry crown dieback (one-way ANOVA,
F=0.38, p=0.6845).
26 Plots
0.4
0.2
0.5
0.4
0.3
0.2
0.1
0
0
0
0-25
25-50
6 Plots
40
35
30
25
20
19 Plots
10
30 Plots
5
0
0
1
0
0-25
6 Plots
14
12
8
30 Plots
6
4
2
0
1
2
19
98
19
96
19
94
8 Plots
0.4
0.2
0
0-25
25
20
15
10
32 Plots
24 Plots
5
0
0
1
9 Plots
20
10
5
0
4 Plots
8
31 Plots
6
4
39 Plots
2
0
1
1
Years of Elm Spanworm Defoliation
12
2
Years of Elm Spanworm Defoliation
The average crown dieback value
for stands that were defoliated
twice was higher but the difference
was not significantly different.
There was significant linear
relationship (one-way ANOVA
F=3.13, p=0.0496).
Also known as beech scale Nectria canker, beech bark disease is an insect-fungus “complex” that
kills or injures American beech. The disease results when a Nectria fungus infects the bark through
the feeding wounds caused by beech scale insects. Around the turn of the century the beech scale
insect was introduced into Nova Scotia from Europe. It has since spread south westward into New
England, New York, Pennsylvania, and West Virginia.
Wingless young scale insects are attracted to rough areas on the smooth
bark of beech trees. They insert their stylets through the bark and into
the phloem to feed. Once they begin feeding, they cease to move.
Each insect then secretes a white, woolly, protective covering to
overwinter. The insects may cover the entire trunk. Female insects
reproduce parthenogenetically (in the absence of fertilization) causing
the population to increase rapidly. One generation occurs annually.
15
0
Plots that were defoliated twice had
a significantly greater percent of
standing dead red maple. There was
significant evidence of a linear
trend between years of elm
spanworm defoliation and percent
standing dead red maple basal area
(one-way ANOVA F=5.96,
p=0.0044).
BEECH BARK DISEASE
16 Plots
25
Plots that suffered defoliation had a
greater percentage of standing dead
sugar maple, but the difference was
not significant. There was not
significant evidence of a linear
trend between years of elm
spanworm defoliation and percent
standing dead sugar maple basal
area.
16
1989
1999
% Beech Basal Area
0-9
9 - 19
19 - 28
28 - 38
38 - 47
No Data
28 Plots
14
12
10
8
6
18 Plots
4 Plots
4
2
0
0
1
2
Years of Elm Spanwom Defoliation
Years of Elm Spanworm Defoliation
Crown dieback did increase with
years of defoliation but the
relationship was not significant.
Lower slope sugar maple stand showing healthy
trees.
50-100
The average number of years of elm
spanworm defoliation was greatest
for plots with greater than 50%
sugar maple basal area.
2
10
25-50
% Sugar Maple Basal Area
40
35
30
0
0
40 Plots
Years of Elm Spanworm Defoliation
The percent standing dead black
cherry basal area was significantly
greater on plots that were defoliated
by elm spanworm in two successive
years than ones that were defoliated
once. There was significant
evidence of a linear relationship
between years of elm spanworm
defoliation and percent standing
dead black cherry basal area (oneway ANOVA F=5.04, p=0.01).
19 Plots
0.6
50-100
5 Plots
50
45
Years of Elm Spanworm Defoliation
10
25-50
There was not evidence of a
relationship between percent red
maple basal area and years of elm
spanworm defoliation.
2
16
0.8
% Red Maple Basal Area
The average duration of defoliation
was significantly greater on plots
with greater than 25% black cherry
basal area. There was significant
evidence of a linear trend between
percent black cherry basal area and
years of elm spanworm defoliation
(regression, F=14.57, p=.0002).
15
39 Plots
1
Upper slope
sugar maple
stand showing
extensive
mortality.
0
50-100
% Black Cherry Basal Area
45
19
92
19
90
19
88
Average Years of Elm Spanworm
Defoliation
0.6
38 Plots
0.6
% Standing Dead Sugar Maple BA
100000
26 Plots
0.7
4 Plots
1.2
Average Crown Dieback of Sugar
Maple Trees
150000
0.8
14 Plots
23 Plots
0.8
% Standing Dead Red Maple BA
200000
20 Plots
1
Average Crown Dieback for Red
Maple Trees
Historically outbreaks occur approximately
every 10 years in the region. Previous
outbreaks occurred in 1972-1974 and 19821984. The most severe defoliation occurred
in 1995 when nearly 290,000 acres were
affected.
16 Plots
Average Years of Elm Spanworm
Defoliation
250000
1.4
0.9
19 Plots
% Standing Dead Black Cherry BA
Acres Defoliated
300000
1.2
Average Crown Dieback for Black
Cherry Trees
350000
The area defoliated by the elm spanworm within the
proclamation boundary of the ANF covered almost
320,000 acres in 1993.
The most recent elm spanworm outbreak on the
ANF was in 1992 and 1993.
Average Years of Elm Spanworm
Defoliation
A kriged surface of percent black cherry basal
area highlights the areas where cherry makes
up the majority of stand stocking.
The most recent cherry scallop shell moth
outbreak on the Allegheny was in 1993, 1994,
1995, and 1996. Outbreaks generally last two
to three years.
19
86
19
84
0
Sugar maple trees that were
defoliated once by elm spanworm
exhibited significantly more crown
dieback than trees that were not
defoliated or defoliated in two
years.
A kriged surface of percent American beech
basal area illustrates that the highest
concentrations of beech are located in the
northeastern part of the ANF.
1989 Killing Front
IN
OUT
1989 FIA
2.9%
1.4%
2000 FHM 2.6%
5.5%
Beech bark disease first moved into
Pennsylvania in 1958. Currently the killing
front is moving across the northeast corner
of the ANF.
2000 Killing Front
IN
OUT
1.8%
1.6%
9.7%
0.9%
The percent standing dead beech
is almost twice as great inside
the 1989 killing front according
to the 1989 FIA data. The
percent standing dead beech is
over ten times greater inside the
2000 killing front as indicated
by the 1998 and 1999 FHM
data.
THE FOREST
CURRENT FOREST CONDITIONS
GYPSY MOTH
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The two major forest types
represented on the ANF are
black cherry and red
maple/northern hardwoods. The
western and southern edges are
the only areas that have a
significant oak component. The
rest of forest is predominantly
northern and Allegheny
hardwoods.
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Red maple/northern hardwoods
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Mixed northern hardwoods
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White oak/red oak/hickory
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Gypsy moths spend the winter in the egg stage as
embryonated eggs. In April or early May the
eggs hatch, and larvae feed until June. After
feeding is complete the larvae pupate and emerge
as adult moths after about two weeks. The adults
then mate and the female lays eggs, usually on
tree trunks. The gypsy moth has one generation
per year.
$
Ñ
#
Allegheny
National Forest
black cherry
black cherry
Pennsylvania
red maple
red maple
American beech
American beech
sugar maple
sugar maple
eastern hemlock
1989 FIA Survey
1998 and 1999 FHM Surveys
red oak
The Allegheny National Forest (ANF) comprises 740,500 acres and is located in northwestern
Pennsylvania on the unglaciated portion of the Allegheny Plateau. The ANF is characterized by an
abundance of black cherry, maple, and other hardwoods. The ANF was established in 1923 and
currently the Forest Service performs a range of management activities designed to provide multiple
benefits. Recently, there has been increasing concern about forest health issues on the ANF due to
actions by both endemic and exotic disturbance agents. This project focused on quantifying the
effects of several forest disturbance agents including gypsy moth, cherry scallopshell moth, elm
spanworm, and beech bark disease. These objectives were addressed via comparisons of historical
aerial survey with forest conditions recorded in permanent plots that are maintained by the Forest
Service Forest Inventory and Analysis (FIA) and Forest Health Monitoring (FHM) programs.
RANGE OF THE GYPSY MOTH AS OF 1999
The gypsy moth was introduced in 1868 or 1869
near Boston, Massachusetts. Outbreaks began to
occur in the area about 10 years later. Since then
the range of the gypsy moth has been slowly
spreading. The gypsy moth invaded the ANF in
the early 1980s.
eastern hemlock
1989 FIA Survey
red oak
birch spp.
birch spp.
white ash
white oak
white oak
1998 and 1999 FHM Surveys
% Oak Basal Area
0 - 13
14 - 26
27 - 39
40 - 52
53 - 66
No Data
white ash
bigtooth aspen
bigtooth aspen
0
5
10
15
20
25
30
35
40
0
AVG. LIVE BA/ACRE (sq. ft.)
10
20
30
40
50
AVG. % STANDING DEAD BA
Black cherry and red maple are the two most
abundant species on the ANF.
THE DATA
Among the five most abundant species,
mortality was proportionally greatest in sugar
maple. The increase in the percent of dead sugar
maple may due to a general decline in sugar
maple on the ANF. Beech bark disease is
probably the cause of the increase in percent
dead American beech basal area.
1
2
3
4
The most recent major outbreak of gypsy moth
occurred in 1984-1989 on the Allegheny National
Forest. A second, less intense, outbreak took
place in 1992. Most of the defoliation occurred in
areas with a major oak component.
A kriged surface of percent oak basal area from
the 1989 FIA data shows that most of the oak on
the ANF is on the western edge.
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no FH M
an d 19 98 F HM plot
an d 19 99 F HM plot
an d R em e asur ed F H M
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% Standing Dead BA
0-5
5 - 14
14 - 29
29 - 53
53 - 98
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Plot L oc atio ns
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FIA and FHM plot locations on the ANF
FHM field plot design
According to the 1989 FIA survey, the
western part of the forest had a higher
percentage of standing dead basal area.
A kriged surface of percent standing dead basal
area from the 1989 FIA survey illustrates that the
area defoliated by gypsy moth had a higher
proportion of mortality.
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The analyses for this project
were derived from three
sources of data:
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0 (14.9%)
1 (35.5%)
2 (36.5%)
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4 (1.4%)
5 (0.2%)
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1999
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25
12 Plots
1.2
5 Plots
4 Plots
1
0.8
0.6
0.4
143 Plots
0.2
3 Plots
20
15
10
13 Plots
3 Plots
5
0
0
0-20
20-50
50-80
80-100
% Oak BA
0
1
2
Years of Gypsy Moth Defoliation
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% Standing Dead BA
0-3
3-8
8 - 15
15 - 33
33 - 54
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Kriged % Standing Dead
2-4
4-6
6-8
8 - 10
10 - 12
No Data
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1999
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1. Forest Inventory and
Analysis (FIA) plot data,
2. Forest Health Monitoring
(FHM) plot data, and
3. aerial surveys of
defoliation.
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Average Years of Gypsy Moth
Defoliation
1.4
% Standing Dead Oak BA
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Kriged % Standing Dead
0-4
4-9
9 - 13
13 - 18
18 - 22
No Data
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1989
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A major outbreak occurred from
1984 to 1989. The worst year
during that episode was 1987
when nearly 160,000 acres were
defoliated. Another less
extensive outbreak occurred from
1991 to 1993. Almost 50,000
acres were defoliated in 1992.
140000
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84
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1989
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88
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160000
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Years of defoliation and percent of land area defoliated by all
damage causing agents (1984-1998)
A posting of percent standing dead basal area
from the 1998 and 1999 FHM surveys shows that
the south central portion of the forest appears to
have more plots with greater than 8% mortality.
The kriged surface of percent standing dead
basal area from the 1998 and 1999 FHM surveys
highlights the areas with the highest mortality.
The area is similar to the area defoliated by
cherry scallopshell moth.
Return to FHM Posters Home Page
On the ANF, stands with a higher percentage of
oak were defoliated more often by gypsy moth.
There was significant evidence of a linear trend
between percent oak basal area and years of
gypsy moth defoliation (regression, F=92.51,
p<0.0001).
The average amount of standing dead oak basal
area increased with frequency of defoliation
although the relationship was not significant.