United States 

Department o 

Agriculture 

Forest 

Service 

Northern 

Region 

200 East Broadway 

P.O. Box 7669 

Missoula, MT 59807 

Numbered Report 05-04 August 2005

Hemlock Defoliation in North Idaho, Permanent Plot Establishment and 

Preliminary Results 2002-2004

Carol Randall, Entomologist 

USDA Forest Service, Northern Region Coeur d’Alene 

Doug Wulff, Biologist Science Technician 

USDA Forest Service, Northern Region Coeur d’Alene

Background 

In 2002 aerial surveyors detected areas of 

defoliation in western hemlock (Tsuga 

heterophylla) on the Priest Lake and Sandpoint 

Ranger Districts of the Idaho Panhandle 

National Forest (IPNF) (Figure 1). The causal 

agent was unknown. Follow up ground surveys 

found late instar larvae and adults of budworms, 

Choristoneura species (taxonomic findings are 

summarized in Appendix A). 

Defoliation was again mapped in 2003 and 

2004, extending southward into the North Fork 

of the Coeur d’Alene River drainage (Figure 2). 

There has only been one other report from 

1921-1922 of western spruce budworm feeding 

on hemlock in this area. There was no 

information on losses sustained as a result of 

the 1920’s defoliation. The current defoliation 

raises concerns about the potential impact 

moderate to severe defoliation may have on old 

growth hemlock. 

 

Figure 1: Hemlock defoliation mapped during 

aerial surveys in 2002. Subsequent ground 

surveys found larvae and adults in the genus 

Choristoneura. 
2 

Figure 2: Hemlock defoliation mapped during aerial surveys in 2003 (left) and 2004 (right). Subsequent 

ground surveys found larvae and adults in the genus Choristoneura. 

Figure 3: Acres of hemlock defoliation mapped on the Coeur d’Alene River, Sandpoint, and Priest Lake 

Ranger Districts, Idaho Panhandle National Forest during aerial surveys in 2002-2004. 

2003 Defoliation 2004 Defoliation 
3 

Permanent Plot Locations 

Six defoliated areas were chosen and permanent plots were established to quantify current defoliation 

and tree damage (Figure 4). 

 

Figure 4: Hemlock defoliation permanent plot locations, Sandpoint and Priest Lake Ranger Districts, 

Idaho Panhandle National Forests. 1= Porcupine Creek, 2= Granite Creek, 3= Athol Creek, 4= Distillery 

Bay, 5= Tango Creek, 6= South Fork of Gold Creek. 

Permanent Plot Methods 

Five 1/20th acre fixed radius permanent plots 

were established along Porcupine Creek in the 

Lightening Creek drainage north of Clark Fork, 

Idaho in the fall of 2002. In the spring of 2003 

five additional 1/20th acre plots were added 

along Porcupine Creek and ten 1/20th acre 

permanent plots were established in each of the 

following areas: Athol Creek (2), Granite Creek 

(3), Distillery Bay (4), Tango Creek (5), and 

South Fork of Gold Creek (6) (Figure 4, 

Appendix B). 
On each plot, hemlock and other traditional 

western spruce budworm host trees (Douglas-fir, 

grand fir, Engelmann spruce) 2 inches in 

diameter at breast height (DBH) and above were 

tagged and measured. Individual tree 

measurements included DBH and defoliation. A 

1/100 acre fixed radius regeneration plot was 

established. In the regeneration plot seedling 

and sapling (<2 inches DBH) were counted and 

rated for defoliation (Appendix C). 

Defoliation rating were based on Twardus 

(1985) and involved visually dividing the tree 

crown into thirds and assigning a defoliation 

code to each level (lower, middle, and upper): 

Class Percent Defoliation Median Defoliation 

1 0 No visible defoliation 

2 1-25% 12.5% 

3 26-50% 38% 

4 51-75% 63% 

5 76-99% 88% 

6 100% No current year foliage left 

Crews were instructed to use binoculars and 

estimate defoliation on current year’s foliage 

only. 

Whole tree defoliation ratings were derived by 

adding the ratings for each crown 3rd and 

dividing by three. 

Stand Conditions in Plot Areas 

Plot areas were selected based on the presence 

of visible defoliation in 2002/ 2003. Hemlock was 

the dominant overstory tree species in each of 

the 6 plot areas, though many also had western 

red cedar (Thuja plicata), Douglas-fir 

(Pseudotsuga menziesii), grand fir (Abies 

grandis), subalpine fir (Abies lasiocarpa), 

Engelmann spruce (Picea engelmanii), western 

larch (Larix occidentalis) and white pine (Pinus 

monticola) components (Table 1, Appendix C). 

Table 1: Overstory Stand Composition for 6 Hemlock Defoliation Permanent Plot Areas 2003, Sandpoint 

and Priest Lake Ranger Districts, Idaho Panhandle National Forest. 

Permanent Plot Percent Stand Basal Area by Overstory Species 

Area WH WRC GF DF WP WL SAF Birch 

Porcupine Creek 87 5 6 1 1 0 0 0 

Granite Creek 76 24 0 0 0 0 0 0 

Athol Creek 87 13 0 0 0 0 0 0 

Distillery Bay 46 17 16 3 5 7 0 7 

Tango Creek 78 18 4 0 0 0 0 0 

S Fork Gold Creek 91 8 0 0 0 0 1 0 

WH = western hemlock; WRC = western red cedar; GF = grand fir; DF = Douglas-fir; WP = white pine, 

WL = western larch, SAF = subalpine fir, Birch = birch. 

In most of the plot areas, the regeneration was hemlock dominated with minor components of other tree 

species (Table 2, Appendix C).
5 

Table 2: Regeneration Species Composition for 6 Hemlock Defoliation Permanent Plot Areas 2003, 

Sandpoint and Priest Lake Ranger Districts, Idaho Panhandle National Forest. 

Permanent Plot Trees per Acre by Species 0-4.9 DBH 

Area WH WRC GF DF WP ES SAF Junip. 

Porcupine Creek 6510 390 0 60 60 60 30 420 

Granite Creek 1830 540 0 0 0 0 0 0 

Athol Creek 2910 270 60 30 0 0 0 0 

Distillery Bay* 2850 2070 300 0 90 0 0 7 

Tango Creek 1170 1380 0 0 60 0 0 0 

S. Fork Gold Creek 2700 300 0 0 0 60 150 0 

*also western larch 30 TPA, birch 90 TPA 

WH = western hemlock; WRC = western red cedar; GF = grand fir; DF = Douglas-fir; WP = white pine, 

ES = Engelmann spruce, SAF = subalpine fir, Junip. = Juniper. 

Defoliation Summary 2002-2004 

Defoliation was concentrated in the tops of 

trees, especially during the first year of visible 

defoliation. The severity of defoliation fluctuated 

between plot areas and from year to year (Table 

3, Appendix C). 

 

Table 3: 2002-2004Top 1/3rd and Whole Tree Average Defoliation Ratings for Overstory Trees on Six 

Hemlock Defoliation Plot Areas, Sandpoint and Priest Lake Ranger Districts, Idaho Panhandle National 

Forests. 

2002 2003 2004 Plot Area # Trees Top WT Top WT Top WT 

Porcupine Creek 52*/ 132 2.58 2.20 4.47 3.18 2.37 1.69

Granite Creek 117 2.59 1.98 3.21 2.72

Athol Creek 133 1.47 1.23 2.60 2.15

Distillery Bay 186 1.97 1.62 2.4 2.16

Tango Creek 53 4.81 3.92 4.36 3.91

South Fork Gold Creek 130 3.15 2.42 4.0 3.48

 *In 2002 only 5 plots had been established along Porcupine Creek with a total of 52 trees. 

Very few trees have experienced 100% defoliation (defoliation rating = 6) in any crown third (2002-2004) 

(Table 4; Appendix C).

Table 4: Number of Trees with a Top 1/3rd Defoliation Rating of 5 (76-99% Defoliation) or 6 (100% 

defoliation) in 2002, 2003, and 2004 for Six Hemlock Defoliation Plot Areas, Sandpoint and Priest Lake 

Ranger Districts, Idaho Panhandle National Forests. 

2002 2003 2004 Plot Area # Trees 6 5 6 5 6 5 

Porcupine Creek 52*/ 132 0 2 45 37 9 8 

Granite Creek 117 5 9 0 20 

Athol Creek 133 0 2 0 9 

Distillery Bay 186 0 2 1 1 

Tango Creek 53 12 25 4 24 

South Fork Gold Creek 130 15 18 18 41 
6 

Sandpoint Ranger District: Porcupine Creek 

The Porcupine Creek plot area is the only area 

located on the Sandpoint Ranger District, IPNF. 

It is also the only area with defoliation data from 

2002-2003. The stand is mostly composed of 

western hemlock, with some Douglas-fir, grand 

fir, subalpine fir, and Engelmann spruce. 

Hemlock was the most heavily defoliated 

species in the stand. In 2002 the top 1/3rd

average defoliation rating was a 2.8, in 2003 a 

4.7, and in 2004 a 2.5, indicating a possible 

declining trend. 

Defoliation on the regeneration plots was limited 

to hemlock trees and was again highest in 2003, 

followed by 2002. In 2004 no defoliation in the 

hemlock regeneration was noted (Appendix C). 

Priest Lake Ranger District 

Hemlock is the dominant overstory species in all 

5-plot areas located on the Priest Lake Ranger 

District. Other species present include western 

red cedar, grand fir, Douglas fir, western larch, 

white pine, and subalpine fir. All plots in Priest 

Lake were established in 2003. Plot area 

average defoliation ratings for the top 1/3rd and 

whole tree generally increased or stayed the 

same from 2003-2004. 

 

Granite Creek 

Only two tree species were present in the 

overstory of the Granite Creek Plot Area, 

hemlock (89% of the TPA) and western red 

cedar (11% of the TPA). 

In 2003, minor defoliation was noted only in 

hemlock regeneration. In 2004, some 

defoliation was noted in western red cedar 

regeneration and the intensity of hemlock 

regeneration defoliation increased (Appendix C 

Table 8). 

Athol Creek 

As in Granite Creek the only overstory tree 

species in the Athol Creek plots are hemlock 

(98% of the TPA) and western red cedar (2% of 

the TPA). Western red cedar is not considered a 

host for the western spruce budworm so 

defoliation ratings were only taken on hemlock. 

The average defoliation intensity increased in 

this plot area from 2003-2004 (Table 3). 

In 2003, there was no defoliation noted in the 

regeneration in the Athol Creek Plots. In 2004, 

defoliation was noted on hemlock, western red 

cedar, and grand fir regeneration; it was most 

intense (highest defoliation ratings) on grand fir 

regeneration (Appendix C Table 12). 

Distillery Bay 

The Distillery Bay plot area has a more mixed 

conifer composition than the other defoliation 

plot areas; hemlock comprises ~ 51% of the 

TPA, followed in abundance by western red 

cedar (14% of the TPA), grand fir (12% of the 

TPA), birch (11% of the TPA), western larch (6% 

of the TPA), western white pine and Douglas-fir 

(both ~ 3% of the TPA). The average defoliation 

intensity increased in the overstory of this plot 

area from 2003 – 2004 (Table 3; Appendix C 

Table 15). No regeneration was noted. 

Tango Creek 

The Tango Creek plot area is a hemlockdominated forest (72% of the TPA) with cedar 

(21% of the TPA) and grand fir (6% of the TPA) 

also present in the overstory. Defoliation has 

been present on both overstory hemlock and 

grand fir, with the average defoliation intensity 

higher on the grand fir (Appendix C Table 18). 

The regeneration measured in the plot was 

composed of hemlock, white pine, and cedar; 

hemlock was the most significantly defoliated 

(Appendix C Table 19). 

South Fork of Gold Creek 

The South Fork of Gold Creek plot area is 

largely composed of hemlock (97% of the TPA) 

with minor amounts of subalpine fir (2% of the 

TPA) and cedar (1% of the TPA). Plot level 

average defoliation intensity ratings increased 

from 2003-2004. Average overstory subalpine 

fir defoliation intensity ratings were higher than 

average overstory hemlock defoliation intensity 

ratings in 2003 but not 2004 (Appendix C Table 

22). 

In 2003, hemlock was the only regeneration 

species to have measurable defoliation, in 2004 

regenerating Engelmann spruce and subalpine 
7 

fir had higher defoliation intensity ratings than hemlock (Appendix C Table 23). 

Conclusion 

The area affected by hemlock defoliation 

increased in 2004 from 2003 levels. While the 

intensity of defoliation appeared to decrease in 

the Porcupine Creek plot area on the Sandpoint 

Ranger District from 2003-2004, it increased or 

stayed the same on the other 5 plot areas on the 

Priest Lake Ranger District. 

Collections of larvae from defoliated areas 

indicate a complex of 4 or 5 Choristoneura

species are responsible (Appendix A), though 

Choristoneura occidentalis, the western spruce 

budworm, is the most abundant. Lower crown 

sampling has to date been unable to uncover 

any of the more frequently encountered hemlock 

defoliators such as the western blackheaded 

budworm (Acleris gloverana), western hemlock 

looper (Lambdina fiscellaria), and western false 

hemlock looper (Nepytia freemani). Only a few 

individual sawflies (Neodeprion spp.) were 

observed during sampling, not enough to result 

in the level of defoliation currently being 

observed. 

The last reported incident of western spruce 

budworm defoliation in hemlock occurred in the 

Priest Lake area in 1922. Records from that 

outbreak are incomplete. 

We will continue to monitor our permanent plots 

until the defoliation stops. 

Literature Cited 

Twardus, D.B. 1985. Surveys and sampling 

methods for population and damage 

assessment. In: Brookes, M.H., Bolbert, 

J.J.; Mitchell, R.G.; Stark, R.W., editors. 

Managing trees and stands susceptible 

to the western spruce budworm. Tech. 

Bull. 1695. Washington, D.C: U.S. 

Department of Agriculture, Forest 

Service; 27-40. 
8 

Appendix A: Taxonomic Information, Hemlock Defoliation North Idaho 2003-2004 

2003 

In 2003, 18 adult moths were collected in areas 

of hemlock defoliation in north Idaho (Bonner 

and Boundary County) and 5 adult moths were 

collected in areas of hemlock defoliation in 

western Montana (Lincoln County). All moths 

were sent to Frank W. Merickel, curator WF Barr 

Entomological Museum, University of Idaho. Mr. 

Merickel then forwarded the pinned moths onto 

a Tortricid specialist for definitive identification. 

All of the 23 moths sent in for identification were 

Tortricids in the genus Choristoneura. There 

were four species found (Table 1). 

Table 1: 2003 identification of Choristoneura species collected from areas of hemlock defoliation in 

northern Idaho and western Montana. 

Number Genus species Location 

6 Choristoneura orae Bonner Co, ID 

12 Choristoneura occidentalis 5 in Bonner Co, ID; 4 in Lincoln Co, MT; 3 

in Boundary Co, ID 

1 Choristoneura lambertiana 1 in Bonner Co, ID 

4 Choristoneura retiniana 1in Boundary Co, ID; 2 in Bonner Co, ID 

2004 

In 2004, personnel from the Priest Lake Ranger 

District collected a number of branch samples 

from defoliated trees. The branch samples were 

sent to Carol Randall, Forest Health Protection 

Entomologist in Coeur d’Alene. Carol removed 

larvae from each branch sample and reared the 

larvae on the host from which they had been 

collected. As the larvae began to pupate, Carol 

forwarded them to Frank Merickel, curator WF 

Barr Entomological Museum, University of 

Idaho, for specimen preparation and 

identification. 

The 2004 host rearing resulted in 28 moths 

representing 5 Choristoneura species (Table 2) 

as determined by Ron Leuschner. Mr. Merickel 

also reared out 8 Ichneumonid parasites. 

Table 2: 2004 identification of Choristoneura species collected from areas of hemlock defoliation in 

northern Idaho on the Priest Lake Ranger District, Idaho Panhandle National Forest. 

Number Genus species 

4 Choristoneura orae 

18 Choristoneura occidentalis 

1 Choristoneura lambertiana 

2 Choristoneura retiniana 

1 Choristoneura fumiferana* 

* 2 additional moths are still pending species identification, are thought to also be C. fumiferana
9 

Appendix B: Permanent Plot Maps for Six Areas Monitored for Hemlock Defoliation 

Area 1: Porcupine Creek Hemlock Defoliation plots area on the Sandpoint Ranger District, IPNF. 

Individual plots were not GPS-ed as of date of this report. Five plots were established fall 2002, 5 

additional plots were established in 2003. 

Area 2: Granite Creek Hemlock Defoliation plots area on the Priest Lake Ranger District, IPNF. Ten plots 

were established in 2003. 
10 

Area 3: Athol Creek Hemlock Defoliation plots area on the Priest Lake Ranger District, IPNF. Ten plots 

were established in 2003. 

Area 4: Distillery Bay Hemlock Defoliation plots area on the Priest Lake Ranger District, IPNF. Ten plots 

were established in 2003. 
11 

Area 5: Tango Creek Hemlock Defoliation plots area on the Priest Lake Ranger District, IPNF. Ten plots 

were established in 2003. 

Area 6: South Fork Gold Creek Hemlock Defoliation plots area on the Priest Lake Ranger District, IPNF. 

Ten plots were established in 2003. 
12 

Appendix C: Preliminary Permanent Plot Results 

Porcupine Creek 

The Porcupine Creek Plots are the only ones 

located on the Sandpoint Ranger District, IPNF. 

The first 5 plots in the 10-plot area were 

established in the fall of 2002, the first year of 

visible defoliation. 

Stand Conditions 

Western hemlock (hemlock) was the dominant 

tree species in the overstory and regeneration 

plots in the Porcupine Creek permanent plots 

(Tables 1 and 2). Approximately 85% of the 

overstory trees pre acre (TPA) were hemlock, 

with western red cedar (5% TPA), grand fir (5% 

TPA), white pine (3% TPA) and Douglas-fir (1% 

TPA) also present. The regeneration was also 

dominated by hemlock seedlings/ saplings (85% 

TPA) with juniper (~6% TPA) and western red 

cedar (5% TPA) and minor numbers of 

subalpine fir, spruce, western white pine, and 

Douglas-fir seedling/ sapling trees per acre. 

Table 1: Stand summary information for Porcupine Creek Defoliation Permanent Plots in 2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Grand Fir 22 10 9 6 5 

White Pine 14 2 5 1 3 

Douglas-Fir 4 2 9 1 1 

Western Red 

Cedar 

21 8 9 5 5 

Western 

Hemlock 

351 142 10 87 85 

TOTAL 411 164 9 100 100 

Table 2: Stand regeneration trees per acre summary information for Porcupine Creek Defoliation 

Permanent Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Subalpine Fir 30 0 30 

Juniper 420 0 420 

Spruce 60 0 60 

Western White Pine 30 30 60 

Douglas-fir 60 0 60 

Western Red Cedar 300 90 390 

Western Hemlock 5430 1080 6510 

TOTAL 6330 1200 7530 

Defoliation Summary 

Five of the 10 permanent plots were established 

in 2002 along Porcupine Creek. A total of 10 

plots were measured in 2003 and 2004 (Table 

3). The hemlock trees were defoliated more 

significantly (higher defoliation ratings) than the 

other species. For defoliated plot trees, the top 

third was usually more heavily defoliated than 

the middle and lower third. For the three years 

of data available, defoliation ratings were 

highest in 2003, followed by 2002 and 2004. 
13 

Table 3: Defoliation rating summary for overstory trees in permanent plots along Porcupine Creek, 

Sandpoint Ranger District, Idaho Panhandle National Forest 2002-2004. 

 

2002 

Ratings* Specie 2003 Ratings* 2004 Ratings* 

s 

# 

Tree

s** 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3 T1 M2 B3

SAF 1 2.8 2.8 2.8 1 1 1 3 2 2 1 1 1 

DF 4 9.2 2.2 23.2 2 2 2 2.8 2.3 2 2.3 1.5 1.3 

GF 6 8.2 2 11.2 1.7 2 2 2.3 2 2 1 1.2 1 

S 2 2.55 2.4 2.7 1 1 1 2 2 1 1 1 1 

WH 119 8.94 2 45.1 2.8 2.1 2 4.7 3.1 2 2.5 1.5 1.3 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% 

** In 2002 with only 5 plots tree numbers were as follow: SAF 1; DF 3; GF 3; S 2; WH 43 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

SAF = subalpine fir; DF= Douglas-fir; GF = grand fir; S = Engelmann spruce; WH = western hemlock 

Average plot defoliation ratings were the highest 

in 2003 when the plot average top 1/3rd

defoliation rating for hemlock was 4.7, or 

between 51-75% defoliated. In that year 45 plot 

trees (44 hemlock and 1 Douglas-fir) had a top 

1/3rd defoliation rating of 6 (100%) and 37 trees 

(all hemlocks) had a top 1/3rd defoliation rating of 

5 (76-99%). In 2004, the average plot level 

defoliation rating had decreased. The top 1/3rd in 

hemlock trees was 2.5, or between 1-25% 

defoliated, and only 8 plot trees, all hemlock, 

had a top 1/3rd defoliation rating of 6, and 8 plot 

hemlock trees had a top 1/3rd defoliation rating 

of 5. 

Defoliation on the regeneration plots was limited 

to hemlock trees and was again highest in 2003, 

followed by 2002, and in 2004 no current 

defoliation in the hemlock regeneration was 

noted (Table 4). 

Table 4: Defoliation rating summary for regenerating trees in permanent plots along Porcupine Creek, 

Sandpoint Ranger District, Idaho Panhandle National Forest 2002-2004. 

Specie 2002 Ratings* 2003Ratings* 2004 Ratings* 

s 

# 

Tree

s** 

T1

 M2 B3 T1 M2 B3 T1 M2 B3

WRC 3 1 1 1 1 1 1 1 1 1 

PY 11 1 1 1 1 1 1 1 1 1 

WH 7 1.5 1.5 1.5 3 2.4 2 1 1 1 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% 

** In 2002 with 5 plots tree numbers were as follow WRC 1; PY 1; WH 4 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

WRC = western red cedar; PY = Pacific yew; WH = western hemlock 

Granite Creek 

The Granite Creek Plots were established in 

2003 on the Priest Lake Ranger District, IPNF. 

 

Stand Conditions 

The Granite Creek plot area is a hemlockdominated forest with hemlock comprising 89% 

of the TPA in the overstory and 77% of the 

regeneration TPA. The only other tree species 

present was western red cedar (Tables 5 and 6). 
14 

Table 5: Stand summary information for Granite Creek Defoliation Permanent Plots in 2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Western Red 

Cedar 

42 46 24 24 11 

Western 

Hemlock 

351 144 9 76 89 

TOTAL 393 190 10 100 100 

Table 6: Stand regeneration trees per acre summary information for Granite Creek Defoliation 

Permanent Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Western Red Cedar 360 180 540 

Western Hemlock 1080 750 1830 

TOTAL 1440 930 2370 

Defoliation Summary 

The crew did not measure defoliation on cedar 

for the overstory plot trees. Hemlock defoliation 

ratings were higher in 2004 than in 2003, and in 

both years the top 1/3rd of hemlock trees were 

more heavily defoliated than the bottom 2/3rds 

(Table 7). 

Table 7: Defoliation rating summary for overstory trees in permanent plots along Granite Creek, Priest 

Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

Species # 2003Ratings* 2004 Ratings* 

Trees 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3

WH 117 10.09 2 38.1 2.6 1.9 1.4 3.3 2.7 2.2

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WH = western hemlock 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

Average plot defoliation ratings were the highest 

in 2004 when the plot average top 1/3rd

defoliation rating for hemlock was 3.3, or 

between 26-50% defoliated. In that year 20 plot 

trees had a top 1/3rd defoliation rating of 5 (76-

99%). In 2003, the average plot level defoliation 

rating was lower, however there were trees in 

2003 that had a top 1/3rd defoliation rating of 6 

(100%). The average top 1/3rd defoliation rating 

for the plots were 2.5, or between 1-25% 

defoliated, but 5 plot trees had a top 1/3rd

defoliation rating of 6, and 9 plot trees had a top 

1/3rd defoliation rating of 5. 

In 2003 minor defoliation was noted only on 

hemlock seedling/ saplings. In 2004 minor 

defoliation was noted on cedar regeneration; 

hemlock regeneration defoliation was more 

intense than it had been in 2003 (Table 8).
15 

Table 8: Defoliation rating summary for regeneration plot trees in permanent plots along Granite Creek, 

Priest Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

2003Ratings* 2004 Ratings* Species # Trees T1

 M2 B3 T1 M2 B3

WRC 7 1 1 1 1.3 1 1 

WH 5 1.4 1 1 3.2 2.8 2.6 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WRC = western red cedar; WH = western hemlock 

1

T = Top 1/3rd of crown, 2M= Middle 1/3rd of crown, 3B= Bottom 1/3rd of crown 

Athol Creek 

The Athol Creek plots were established in 2003 

on the Priest Lake Ranger District, IPNF. 

Stand Conditions 

The Athol Creek plot area is a hemlockdominated forest with hemlock comprising 98% 

of the TPA in the overstory and 90% of the 

regeneration TPA. The only other tree species 

present in the overstory was western red cedar 

(Table 9). Hemlock dominated the regeneration, 

with smaller components of western red cedar, 

Douglas-fir, and grand fir regeneration (Table 

10).

Table 9: Stand summary information for overstory trees Athol Creek Defoliation Permanent Plots in 

2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Western Red 

Cedar 

9 26 27 13 2 

Western 

Hemlock 

463 176 9 87 98 

TOTAL 472 202 10 100 100 

Table 10: Stand regeneration trees per acre summary information for Athol Creek Defoliation Permanent 

Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Grand Fir 60 0 60 

Douglas- Fir 30 0 30 

Western Red Cedar 240 30 270 

Western Hemlock 2160 750 2910 

TOTAL 2490 780 3270 

 

Defoliation Summary 

The crew did not measure defoliation on cedar 

for the overstory plot trees. Hemlock defoliation 

ratings were higher in 2004 than in 2003, and in 

both years the top 1/3rd of hemlock trees were 

more heavily defoliated than the bottom 2/3rds 

(Table11). 
16 

Table 11: Defoliation rating summary for overstory trees in permanent plots along Athol Creek, Priest 

Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

 

Species # 2003Ratings* 2004 Ratings* 

Trees 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3

WH 117 10.09 2 38.1 2.6 1.9 1.4 3.3 2.7 2.2

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WH = western hemlock 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

Grand fir regeneration was most heavily defoliated, followed by hemlock and cedar. No defoliation was 

observed on Douglas-fir regeneration.

Table 12: Defoliation rating summary for regeneration plot trees in permanent plots along Athol Creek, 

Priest Lake Ranger District, Idaho Panhandle National Forest 2003-2004. 

2003Ratings* 2004 Ratings* Species # Trees T1

 M2 B3 T1 M2 B3

WH 11 1 1 1 2 1.5 1.5 

WRC 4 1 1 1 1.75 1.25 1.25 

GF 1 1 1 1 3 2 2 

DF 1 1 1 1 1 1 1 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WRC = western red cedar; WH = western hemlock; GF= grand fir; 

DF= Douglas-fir 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

Distillery Bay 

The Distillery Bay plots were established in 2003 

on the Priest Lake Ranger District, IPNF. 

Western hemlock trees were more heavily 

defoliated than grand fir and Douglas-fir trees on 

the plots. 

Stand Conditions 

The Distillery Bay plot area is a mixed conifer 

forest with hemlock comprising 51% of the TPA 

in the overstory. Additional overstory species 

include slightly larger (QMD = 11) western red 

cedar (14% TPA), grand fir (12% TPA), birch 

(11% TPA) with occasional larch (6% TPA), 

western white pine (3%TPA) and Douglas-fir 

(3% TPA) (Table 13). Hemlock and western red 

cedar dominated the regeneration, with grand fir, 

western white pine, birch, and larch also present 

(Table 14). 
17 

Table 13: Stand summary information for Distillery Bay Defoliation Permanent Plots in 2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Larch 51 20 8 7 6 

Grand Fir 106 48 11 16 12 

Western 

White Pine 

23 14 15 5 3 

Douglas-fir 30 10 8 3 3 

Western Red 

Cedar 

119 50 11 17 14 

Western 

Hemlock 

441 138 8 46 51 

Birch 93 20 6 7 11 

TOTAL 862 300 8 100 100 

Table 14: Stand regeneration trees per acre summary information for Distillery Bay Defoliation 

Permanent Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Larch 0 30 30 

Grand Fir 150 150 300 

Western White Pine 30 60 90 

Western Red Cedar 1680 390 2070 

Western Hemlock 1410 1440 2850 

Birch 0 90 90 

TOTAL 3270 2160 5430 

Defoliation Summary 

Overall defoliation ratings were higher in 2004 

than in 2003, and in both years the top 1/3rd of 

plot trees were more heavily defoliated than the 

bottom 2/3rds (Table 15). Individual tree 

defoliation ratings were lower on the Distillery 

Bay plots than in some others, with only 2 trees 

(1 hemlock and 1 grand fir) receiving a top 1/3rd 

defoliation rating of 5 in 2003 (no 6 ratings) and 

in 2004 only one 6 and one 5 in the top 1/3rd of 

the crown (both hemlocks). The crew did not 

measure defoliation on regeneration plot in 

Distillery Bay. 

Table 15: Defoliation rating summary for overstory trees in permanent plots along Distillery Bay, Priest 

Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

 

Species # 2003Ratings* 2004 Ratings* 

Trees 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3

WH 148 6.5 2 16.9 2 1.6 1.3 2.5 2.1 2 

GF 33 13.6 2.8 21.2 1.9 1.6 1.4 2.3 2.2 2.1

DF 5 8.44 5.7 11 1.6 1.4 1.2 1.8 2 2.2

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WH =western hemlock; GF =grand fir; DF =Douglas-fir 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 
18 

Tango Creek 

The Tango Creek plots were established in 2003 

on the Priest Lake Ranger District, IPNF. In 

Tango Creek, both grand fir and hemlock were 

defoliated, with grand fir defoliation ratings 

slightly higher than hemlock in 2003 and 2004. 

Overall defoliation ratings decreased slightly for 

hemlock and increased slightly for grand fir from 

2003 to 2004. 

Stand Conditions 

The Tango Creek plot area is a hemlockdominated forest (72% TPA) with western red 

cedar (21% TPA) and grand fir (6% TPA) (Table 

16). 

Table 16: Stand summary information for Tango Creek Defoliation Permanent Plots in 2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Grand Fir 9 4 9 4 6 

Western Red 

Cedar 

34 20 12 18 21 

Western 

Hemlock 

114 86 16 78 72 

TOTAL 157 110 14 100 100 

Western red cedar and hemlock dominate the regeneration; western white pine is also present (Table 

17). 

Table 17: Stand regeneration trees per acre summary information for Tango Creek Defoliation 

Permanent Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Western White Pine 60 0 60 

Western Red Cedar 1230 150 1380 

Western Hemlock 1110 60 1170 

TOTAL 2400 210 2610 

 

Defoliation Summary 

Grand fir defoliation ratings were slightly higher 

than hemlock defoliation ratings in both 2003 

and 2004. Hemlock defoliation ratings 

decreased slightly while grand fir defoliation 

ratings increased from 2003-2004. The top 1/3rd

of both species tended to be more heavily 

defoliated than the lower 2/3rds (Table 18). 

Table 18: Defoliation rating summary for overstory trees in permanent plots along Tango Creek, Priest 

Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

Species # 2003Ratings* 2004 Ratings* 

Trees 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3

WH 51 16.0 2 45 4.8 4 3 4.3 3.7 3.6

GF 2 9 7.9 10.1 5 3.5 1.5 5 4 3.5

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WH = western hemlock; GF= grand fir 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

Hemlock was the most significantly defoliated regeneration species (Table 19). 
19 

Table 19: Defoliation rating summary for regeneration plot trees in permanent plots along Tango Creek, 

Priest Lake Ranger District, Idaho Panhandle National Forest 2003-2004. 

2003Ratings* 2004 Ratings* Species # Trees T1

 M2 B3 T1 M2 B3

WH 6 4 3.5 3.3 2.6 2.5 2.5 

WP 1 2 1 1 1 1 1 

WRC 9 1 1 1 1 1 1 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WRC = western red cedar; WH = western hemlock; WP= white pine 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

South Fork Gold Creek 

The South Fork Gold Creek plots were 

established in 2003 on the Priest Lake Ranger 

District, IPNF. Grand fir defoliation ratings were 

slightly higher than hemlock defoliation ratings in 

both 2003 and 2004 

Stand Conditions: 

The South Fork Gold Creek plot area is a 

hemlock-dominated forest (97% TPA) with an 

occasional subalpine fir (2% TPA) and western 

red cedar (1% TPA) (Table 20). 

Table 20: Stand summary information for South Fork Gold Creek Defoliation Permanent Plots in 2003. 

Species Trees/ Acre Basal Area Quadratic 

Mean 

Diameter 

% Stand 

Basal 

Area 

% Stand 

Trees/ 

Acre 

Subalpine Fir 7 2 7 1 2 

Western Red 

Cedar 

4 14 24 8 1 

Western 

Hemlock 

357 156 10 91 97 

TOTAL 368 172 10 100 100 

Hemlock dominates the regeneration; followed by western red cedar, subalpine fir, and spruce (Table 

21).

Table 21: Stand regeneration trees per acre summary information for South Fork Gold Creek Defoliation 

Permanent Plots in 2003. 

Species TPA 00 - 2.9 DBH TPA 3.0 - 4.9 DBH TOTAL 

Subalpine Fir 120 30 150 

Spruce 30 30 60 

Western Red Cedar 300 0 300 

Western Hemlock 1830 870 2700 

TOTAL 2280 930 3210 

Defoliation Summary 

Subalpine fir defoliation ratings were slightly 

higher than hemlock defoliation ratings in 2003 

but not 2004. The top 1/3rd of both species 

tended to be more heavily defoliated than the 

lower 2/3rds (Table 22). 
20 

Table 22: Defoliation rating summary for overstory trees in permanent plots along the South Fork Gold 

Creek, Priest Lake Ranger District, Idaho Panhandle National Forest 2002-2004. 

Species # 2003Ratings* 2004 Ratings* 

Trees 

Avg 

DBH 

Min 

DBH 

Max 

DBH T1

 M2 B3 T1 M2 B3

WH 126 10.2 2 47.4 3.2 2.3 1.8 4 3.4 3.1

SAF 3 4.4 2.3 7.2 3.3 2.7 1.3 3.3 2.7 2.7

ES 1 3.1 3.1 3.1 1 1 1 1 1 1 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% WH = western hemlock; SAF= subalpine fir; ES= Engelmann spruce 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown 

Hemlock was the most significantly defoliated regeneration species in 2003, however subalpine fir and 

Engelmann spruce regeneration was more significantly defoliated than hemlock in 2004 (Table 23). 

Table 23: Defoliation rating summary for regeneration plot trees in permanent plots along South Fork 

Gold Creek, Priest Lake Ranger District, Idaho Panhandle National Forest 2003-2004. 

2003Ratings* 2004 Ratings* Species # Trees T1

 M2 B3 T1 M2 B3

WH 11 1.45 1.36 1.2 3 3 2.9 

SAF 1 1 1 1 5 5 5 

WRC 2 1 1 1 1 1 1 

ES 1 1 1 1 5 5 5 

* Defoliation Ratings based upon Twardus (1985): 1= 0%, 2= 1-25%, 3= 26-50%, 4= 51-75%, 5=76-99%, 

6= 100% 

WRC = western red cedar; WH = western hemlock; SAF= subalpine fir, ES= Engelmann spruce 

1

T = Top 1/3rd of crown 2M= Middle 1/3rd of crown 3B= Bottom 1/3rd of crown