United States 

Department of 

Agriculture 

Forest 

Service 

Northern 

Region 

200 East Broadway 

P.O. Box 7669 

Missoula, MT 59807 

Numbered Report 08-03 January 2008

THINNING AND PRUNING PONDEROSA PINE FOR THE SUPPRESSION AND 

PREVENTION OF ELYTRODERMA NEEDLE DISEASE (Elytroderma deformans 

(Weir) Darker) ON THE BITTERROOT NATIONAL FOREST: 

ESTABLISHMENT REPORT AND FIRST RE-MEASUREMENT 

Blakey Lockman, Pathologist 

USDA Forest Service, Forest Health Protection 

Missoula Field Office 

Cheri Hartless, Silviculturalist 

USDA Forest Service, Northern Region 

Stevensville, MT 

INTRODUCTION 

Elytroderma deformans (Weir) Darker causes a 

serious needle disease of pines in Western North 

America (Childs et al. 1971) and is considered 

the most important needle disease of ponderosa 

pine in Montana. It is a fungus that was first 

described by Weir (1916). E. deformans infects 

current year's needles during mid- to latesummer; the following spring, these needles turn 

red and fruiting bodies of the fungus 

(hysterothecia) are produced on red needles in 

mid- to late-summer. Hysterothecia mature and 

produce spores which infect the current year’s 

needles during periods of high humidity, thus 

completing the cycle. After the spores are 

released, the infected needles are shed in the fall 

and throughout the winter. Vegetative growth of 

the fungus can invade branch and twig tissue. 

Once twigs have become infected, they will 

usually flag again each spring for many years 

and soon curve upwards. Vigorous infected 

branches may develop into dense, globose 

witches’ brooms. These brooms often survive 

and grow for many years, but flagged twigs on 

un-broomed branches gradually decline and die 

after just a few years (Childs 1968). 

Elytroderma needle blight is most damaging in 

trees of low vigor with poor crowns; however, 

the disease is often more conspicuous in good 

crowns (Childs et al. 1971). If a tree is lightly 

infected, growth effects are probably negligible. 

When the infection level is moderately severe in 

mature trees, the crowns become thin with 

shortened needles and the trees are reduced in 

vigor. It is assumed moderately and severely 

infected trees experience some level of growth 

loss, but these effects have not been adequately 

quantified. Direct mortality from E. deformans

has been observed in both precommercial- and 

commercial-sized trees in areas with long-term 

heavy infections. Moderately infected trees are 
2 

also susceptible to bark beetle attacks and may 

be more susceptible to root disease (Childs 

1968). The longer a tree is severely infected with 

E. deformans, the less attractive it becomes to 

bark beetles (Childs et al. 1971). 

Systemic infections from E. deformans can occur 

in the bole of the tree and not in the branches, so 

trees can display the twisting, resinous 

symptoms on the boles, but have no flagging on 

any of the branches. Young pine trees have 

needles borne directly on the bole of the tree, 

which can be an infection court for E. 

deformans. There are no second year needles on 

the bole to turn red to indicate infection because 

once the infected needles are cast, there will be 

none to replace them. If systemic infection 

occurs through these needles, the only way to 

detect it is from the characteristic bending and 

twisting of the bole and the necrotic lesions 

under the bark as seen in systemically infected 

branches. Childs (1968) discovered necrotic 

lesions in trunks of small trees that were not 

associated with branch flagging, and Roth (1959) 

discusses evidence of vegetative spread of the 

disease up and down trunks of smaller trees. 

Elytroderma needle blight has been documented 

in the literature as a cyclic disease (Scharpf and 

Bega 1981, 1988; Childs et al. 1971; Childs 

1968). It usually exists at endemic levels, but 

under certain conditions epidemic outbreaks can 

occur on some sites. In several areas in western 

Montana this disease has been ongoing for years; 

in some places for at least 50 years (Waters 

1957). It is a management concern in these 

localized areas; various outbreaks on the 

Bitterroot National Forest south of Missoula and 

Gette Lake on the Flathead Indian Reservation 

north of Missoula are approaching such 

longevity as to effect management decisions. 

E. deformans has been causing significant 

damage to young 20-year old ponderosa pine 

stands since their establishment in the Lick 

Creek area on the Darby Ranger District of the 

Bitterroot National Forest. These stands consist 

of both planted and natural ponderosa pine. At 

the request of the district, Forest Health 

Protection (FHP) first visited the area in 1999 

(Lockman 1999) and then again in 2003 

(Lockman and Jackson 2003). Elytroderma 

brooms and needle casting are present in the 

younger trees, and the scattered overstory trees 

are lightly infected. Many of the pine boles of 

the younger trees are twisted and bent with no 

directional pattern to the bending apparently due 

to bole infections by E. deformans. 

Maintaining proper stocking density of young 

stands is important in minimizing impacts from 

E. deformans; if E. deformans is already present 

within an older stand, thinning appears to 

exacerbate it, at least in the short term (Childs et 

al. 1971). Thinning ponderosa pine stands early 

and keeping them thinned is the present 

management recommendation in areas prone to 

infection by E. deformans. There is debate about 

what spacing is best to minimize new infections 

and to lessen the impact from this disease. There 

is also debate about the effectiveness of pruning 

to minimize new infections. There is no 

conclusive research indicating that pruning is 

effective, but it has been occasionally 

recommended in the past. Because most of the 

Elytroderma infections occur in the lower 

crowns, operational pruning may be effective in 

helping to control this disease; lifting the crowns 

would remove the most susceptible foliage. 

The Darby Ranger District was preparing to 

precommercially thin these young stands in Lick 

Creek, which offered an opportunity to look at 

the effects of various spacings of thinning and 

pruning on Elytroderma needle disease. With the 

assistance of the District, treatment areas were 

determined and FHP established plots to monitor 

the effects of thinning and pruning on 

Elytroderma needle disease. 

 

METHODS 

Location of Stands 

The study site is on the Darby Ranger District of 

the Bitterroot National Forest, north of Lake 

Como. Twelve stands were scheduled for 
3 

thinning and were large enough to install 

monitoring plots. Stands 2.12, 2.11, 2.10, 2.7, 

2.4, 2.5, 2.6, 2.9, and 2.13 are located off Forest 

Road 5623, and stand 2.1 is located off Forest 

Road 5608. Stands 2.4A and 2.3 are accessed by 

foot from Forest Road 5621. Seven stands are 

located in Sections 24 and 25 of T32N, R22W 

(stands 2.10, 2.7, 2.4, 2.5, 2.6, 2.9, and 2.13); 

four stands are located in Section 30 of T4N, 

R21W (stands 2.12, 2.11, 2.4A, and 2.3); and 

one stand is located in Section 19 of T4N, R21W 

(stand 2.1). 

Treatments 

Treatments were: 1) thin to 12x12 feet spacing 

(T12; 52 total acres); 2) thin to 18x18 feet 

spacing (T18; 51 total acres); 3) thin to 12x12 

feet spacing plus pruning (T12P; 49 total acres); 

and 4) control with no thinning or pruning (C; 41 

total acres). The maximum height of branches to 

be pruned was the lesser of 8 feet or 1⁄2 of the 

total height of the tree. We used a Balanced 

Incomplete Block Design and randomly assigned 

paired treatments to the twelve stands available 

for the study (see Table 1). Each treatment was 

replicated six times. 

TABLE 1. Assignment of paired treatments to each of the twelve stands available for the Elytroderma 

thinning and pruning study. 

Paired 

treatments1

Stand assignments1

 Stand assignments1

T12 T18 2.11 (split into 2.11A and 2.11B) 2.9 (split into 2.9B and 2.9A) 

T12 T12P 2.1 (split into 2.1A and 2.1B) 2.4 (split into 2.4B and 2.4C) 

T12 C 2.7 (split into 2.7 and 2.7Control) 2.4A (split into 2.4A and 2.4AControl) 

T18 T12P 2.13 (split into 2.13A and 2.13B) 2.6 (split into 2.6B and 2.6A) 

T18 C 2.12 (split into 2.12 and 2.12Control) 2.3 (split into 2.3 and 2.3Control) 

T12P C 2.10 (split into 2.10 and 2.10Control) 2.5 (split into 2.5 and 2.5Control) 

1 Each stand was split in half and randomly assigned one of the two paired treatments. Several Control assignments were switched after this random selection 

in order to accommodate concerns of the district. 

Plot Locations within Stands 

The approximate center of each stand half was 

located and marked on the stand map; the 

azimuth and distance from a corner of each stand 

to this center mark was then determined. After 

pacing to the location, a piece of rebar was 

installed. 

Pre-treatment Data 

Pre-treatment data were collected in July 2004 

after disease symptoms had fully developed. 

These stands are at an elevation of 4600 feet to 

5200 feet, so disease development is 

chronologically later than at lower elevations. 

The boundary of a 1/3 acre circular plot was 

flagged (radius equal to 60 feet), using the rebar 

as the center of the plot. Fifty potential crop 

trees were located by walking around this plot 

starting from the north and moving clockwise, 

spacing approximately 12 feet between each tree, 

and keeping within the flagged margins. If fifty 

potential crop trees could not be located within 

the flagged margins of the plot, then the margin 

was expanded until fifty trees were located. 

These trees were permanently tagged at dbh 

(diameter at breast height) facing plot center in 

the control plots, and temporarily flagged in the 

plots scheduled for treatment. Data recorded for 

each tree were: diameter at breast height (dbh); 

total tree height; crown ratio, crown class, lowest 
4 

live crown height; and any damage and severity 

of damage using Northern Region Stand Exam 

protocols (Anonymous 1986); and Elytroderma 

infections. 

Elytroderma infections were evaluated three 

different ways: 

1) First, each crown was rated for 

systemic infections with a tree based 

system as used in the Hawksworth’s 

rating system for dwarf mistletoe 

infections (Hawksworth 1977): 

Divide live crown into thirds: top, 

middle, and bottom. Each third 

receives a rating of 0= no 

systemic infections; 1= 1⁄2 or less 

of total branches have systemic 

infections; 2= more than 1⁄2 of the 

total branches have systemic 

infections. 

2) Each crown was also given an overall 

rating of red foliage using: 

0= <5% red foliage; 1= 5% to 

15%; 2= 16 to 25%, 3= 26 to 

35%; 4= 36 to 45%; 5= 46 to 

55%; 6= 56 to 65%; 7= 66 to 

75%, 8= 76 to 85%; 9= >85% of 

crown is red. 

3) And the third rating was for evaluating 

stem infections from Elytroderma: 

0= no visible stem infection; 1= 

light stem infection, appears to 

have recovered; 2= obvious stem 

infection with twisting and 

deformity. 

In addition to the tree data, plot level information 

was also recorded which included slope and 

aspect at plot center, as well as GPS location. 

Post-treatment Data 

Thinning and pruning of the stands were 

accomplished with a contract crew and were 

completed by September 2004, at which time 

post-treatment data were collected. The control 

plots did not receive a treatment, and thus did not 

need data collected again in 2004. For the 

treatment plots, the margin of a 1/3 acre circular 

plot was again flagged, using the rebar as the 

center of the plot. Fifty crop trees were located 

by walking around this plot starting from the 

north and moving clockwise, and keeping within 

the flagged margins. If fifty trees could not be 

located within the flagged margins of the plot, 

then the margin was expanded until fifty trees 

were located. These trees were permanently 

tagged at dbh facing plot center. Data recorded 

for each tree were: dbh; total tree height; crown 

ratio; lowest live crown height; and any damage 

and severity of damage using Northern Region 

Stand Exam protocols (Anonymous 1986). 

Crown class was determined to have no value 

after treatment, so was not included in the posttreatment data collection. Elytroderma was not 

evaluated at this measurement. The pretreatment Elytroderma ratings will be used as the 

initial infection levels for all plots. 

Remeasurement 

The first remeasurement was done in July 2006, 

to allow for a complete infection cycle of E. 

deformans to occur after stand treatment. In July 

2006, each plot was revisited; tree tags were 

verified and Elytroderma infections were 

evaluated using the same criteria as at plot 

establishment. No growth data were collected at 

this measurement. 

Statistical Analysis 

The statistical software SAS, Mixed Procedure 

(Littell et.al 2006) was used to analyze data. The 

differences between treatment means were tested 

using the F-test in the Type 3 Tests of Fixed 

Effects. T-test of Differences of Least Squares 

Means, with Tukey-Kramer adjustment for 

multiple comparisons, was used for further 

analysis when the F-test was significant. We 

used an alpha level of 0.10 for all statistical tests. 
5 

 

RESULTS 

Plot Establishment

Pre-treatment plot means are shown in Table 2. 

Two pieces of collected data were determined to 

be of minimal value and are not included in the 

analysis. These are crown class and crown ratio. 

All remaining tree and Elytroderma data 

collected in the field are included. Also, two 

new variables were created- elysum and elypres. 

These two data are simplifications of the 

Elytroderma information collected in the field. 

Elysum is the summation of the ratings for 

systemic infections, and elypres is a simple 

measure of presence or absence of systemic 

infections. 

TABLE 2. Pre-treatment means by plot at plot establishment in July 2004. 

Stid1 Treat2 N3 Dbh4 Ht5 Lcht6 Etop7 Emid8 Ebot9 ECrown10 EStem11 ElySum12 ElyPres13

2.11A T12 50 6.00 30.06 12.24 .00 .04 .51 .92 .06 .55 .48 

2.1B T12 51 3.62 14.63 2.12 .00 .00 .02 1.00 .10 .02 .02 

2.4A T12 50 3.92 17.76 5.78 .00 .00 .34 1.16 1.19 .34 .34 

2.4B T12 50 3.56 17.32 5.52 .00 .10 .66 1.24 .69 .76 .60 

2.7 T12 50 4.93 21.54 7.52 .00 .10 .65 1.34 .58 .75 .58 

2.9B T12 50 5.70 25.24 5.78 .00 .00 .02 1.06 .02 .02 .02 

 

2.10 T12P 50 4.65 21.14 5.28 .00 .00 .19 .72 .10 .19 .18 

2.13A T12P 50 4.08 18.72 4.48 .00 .00 .04 1.00 .04 .04 .04 

2.1A T12P 50 4.08 16.18 2.36 .00 .00 .00 1.06 .10 .00 .00 

2.4C T12P 50 3.49 18.37 5.93 .00 .04 .34 .96 .28 .38 .32 

2.5 T12P 49 3.73 17.63 5.16 .00 .00 .63 1.04 .41 .63 .57 

2.6B T12P 50 3.60 18.68 5.44 .02 .04 .58 1.06 .65 .64 .46 

 

2.11B T18 50 4.38 20.51 6.54 .00 .00 .12 1.38 .27 .12 .12 

2.12 T18 50 4.71 20.96 6.58 .00 .01 .13 1.50 .06 .14 .14 

2.13B T18 50 4.61 19.96 4.58 .00 .00 .01 1.18 .00 .01 .02 

2.3 T18 49 3.62 16.82 3.54 .00 .00 .26 1.22 .13 .26 .24 

2.6A T18 50 4.14 17.60 4.36 .00 .00 .30 1.10 .08 .30 .30 

2.9A T18 50 3.03 16.08 4.04 .00 .00 .05 1.18 .00 .05 .06 

 

2.10C C 50 4.44 21.48 5.71 .00 .00 .00 1.04 .04 .00 .00 

2.12C C 50 4.45 22.20 6.82 .00 .00 .00 1.28 .00 .00 .00 

2.3C C 51 2.82 13.20 2.96 .00 .02 .10 1.06 .10 .12 .12 

2.4AC C 50 4.38 19.00 5.26 .00 .02 .33 1.08 .59 .35 .30 

2.5C C 50 2.67 13.88 4.18 .00 .00 .06 1.16 .11 .06 .06 

2.7C C 50 3.85 19.48 7.12 .00 .11 .65 1.64 .42 .76 .54 

1 Stid= stand identification number used by Darby Ranger District. 

2 Treat= Treatment; T12= 12x12 thinning, T12P= 12x12 thinning plus pruning, T18= 18x18 thinning, C= control. 

3 N= number of trees sampled per plot. 

4 DBH= diameter at breast height. 

5 Ht= total tree height. 

6 Lcht= lowest live crown height. 

7 Etop= Elytroderma rating in top 1/3 of crown. 

8 Emid= Elytroderma rating in middle 1/3 of crown. 

9 Ebot= Elytroderma rating in bottom 1/3 of crown. 

10 Ecrown= portion of red needles in crown. 

11 Estem= Elytroderma rating in stem of tree. 

12 Elysum= Etop+Emid+Ebot 

13 ElyPres= if Elysum>0, then tree given a 1 for ElyPres, otherwise=0. 
6 

Average pre-treatment plot conditions of the six 

replications were combined by treatment, and an 

F-test for differences between treatment means 

for each plot variable was done. Table 3 

contains the information from this analysis for 

the tree measurements collected before 

treatment. The probability of an equal or larger 

F value for dbh and height was > 0.10 (Prob. F 

>0.10), so no treatment effect was found, but 

there is a possible treatment effect for lower 

crown height (lcht; Prob.F =0.1030). When the 

treatment effect for lcht is analyzed further using 

a T-test of differences of least squares means, 

significance was found between treatment T12 

and T18. The adjusted means for the tree 

variables indicate the trees in the stands selected 

for the T12 treatment are in general bigger than 

the trees selected for the other treatments, but the 

adjusted probability of an equal or larger T value 

> 0.10 (Adj. Prob. T > 0.10). 

TABLE 3. Table of treatment effects for tree measurements at time of pre-treatment (July 2004). 

Dependent = DBH1

 Ht2 Lcht3

-2 log likelihood 51.5 123.9 89.8 

AIC 63.5 135.9 101.8 

Treatments/sig 0.2217 0.2262 0.10304

Treatment T12 

Adjusted means 4.6315 21.1619 6.3804 

Treatment T12P 

Adjusted means 3.9894 19.2207 5.4785 

Treatment T18 

Adjusted means 4.0281 17.7792 4.4928 

Treatment C 

Adjusted means 3.7609 18.2449 5.1982 

1 DBH= diameter at breast height. 

2 Ht= total tree height. 

3 Lcht= lowest live crown height. 

4 Significant at α<=0.10 
7 

Tables 4a and 4b contain the analysis data for the 

Elytroderma measurements collected before 

treatment. Ecrown, which is the measurement of 

red foliage throughout the crown, was found to 

have a significant treatment effect. The T-test for 

comparisons between the four treatments found a 

significant difference between treatment T12P 

and T18 (Adj. Prob. T =0.0240). Trees in the 

plots selected for the T18 treatment have more 

red needles in their crowns than trees selected for 

the T12P treatment. Caution must be used here, 

as the adjusted means are very small to begin 

with, and very little change in this measurement 

would need to occur to change this statistic. 

Elypres is the measure of presence or absence of 

systemic infections of Elytroderma. A treatment 

effect was found for elypres (Prob. F=0.0996). 

A simple T-test found a significant difference 

between the control and treatment T12 and 

between the control and treatment T12P, but no 

significant adjusted p values were found when all 

combinations of treatments were compared. 

TABLE 4a. Table of treatment effects for Elytroderma measurements at time of pretreatment (July 2004). 

Dependent = Etop1 Emid2 Ebot3

-2 log likelihood -200.3 -107.6 -9.4 

AIC -190.3 -95.6 2.6 

Treatments/sig 0.3641 0.2147 0.1279 

Treatment T12 

Adjusted means 0 0.0310 0.3472 

Treatment T12P 

Adjusted means 0.0033 0.0167 0.3270 

Treatment T18 

Adjusted means 6.07E-20 0.0073 0.1842 

Treatment C 

Adjusted means -819E-22 0.0250 0.1400 

1 Etop= Elytroderma rating in top 1/3 of crown. 

2 Emid= Elytroderma rating in middle 1/3 of crown. 

3 Ebot= Elytroderma rating in bottom 1/3 of crown. 

TABLE 4b. Table of treatment effects for Elytroderma measurements at time of pretreatment (July 2004). 

Dependent = Ecrown1 Estem2 Elysum3 Elypres4

-2 log likelihood -23.6 0.1 -4.4 -16.5 

AIC -11.6 12.1 7.6 -4.5 

Treatments/sig 0.02705 0.1547 0.1490 0.09965

Treatment T12 

Adjusted means 1.0925 0.3949 0.3797 0.3238 

Treatment T12P 

Adjusted means 1.0039 0.3022 0.3470 0.2893 

Treatment T18 

Adjusted means 1.2751 0.1708 0.1902 0.1840 

Treatment C 

Adjusted means 1.1918 0.1354 0.1648 0.1212 

1 Ecrown= portion of red needles in crown. 

2 Estem= Elytroderma rating in stem of tree. 

3 Elysum= Etop+Emid+Ebot 

4 ElyPres= if Elysum>0, then tree given a 1 for ElyPres, otherwise=0. 

5 Significant at α<=0.10 
8 

Treatments were completed in September 2004, 

and crop trees had to be located on the treated 

plots, permanently tagged, and measured for dbh, 

height, and lower crown height. Plot means for 

these 3 variables are shown in Table 5. Average 

plot conditions of the six replications were 

combined by treatment, and a test for differences 

between treatment means for the new tree 

variables was done. The means for these posttreatment trees should be very similar to the 

means for the pre-treatment trees. 

TABLE 5. Table of raw means for post-treatment tree measurements (Sept. 2004). 

Stid1 Treat2 N3 Dbh4 Ht5 Lcht6

2.11A T12 50 5.93 29.84 11.58 

2.1B T12 51 3.55 14.08 2.14 

2.4A T12 50 4.04 18.10 6.16 

2.4B T12 51 2.98 15.51 5.16 

2.7 T12 50 5.23 23.42 7.30 

2.9B T12 50 5.63 25.02 5.90 

 

2.10 T12P 50 4.18 19.54 8.08 

2.13A T12P 50 3.63 16.66 7.32 

2.1A T12P 50 4.09 16.34 8.18 

2.4C T12P 50 2.92 13.28 5.88 

2.5 T12P 50 3.59 16.60 7.64 

2.6B T12P 51 3.79 19.51 8.06 

 

2.11B T18 50 4.37 21.48 7.30 

2.12 T18 50 4.87 24.54 7.54 

2.13B T18 50 4.97 20.74 4.46 

2.3 T18 50 3.41 15.62 3.32 

2.6A T18 51 3.93 17.16 4.98 

2.9A T18 50 3.18 15.46 4.38 

 

2.10C C 50 4.44 21.48 5.71 

2.12C C 50 4.45 22.20 6.82 

2.3C C 51 2.82 13.20 2.96 

2.4AC C 50 4.38 19.00 5.26 

2.5C C 50 2.67 13.88 4.18 

2.7C C 50 3.85 19.48 7.12 

1 Stid= stand identification number used by Darby Ranger District. 

2 Treat= Treatment; T12= 12x12 thinning, T12P= 12x12 thinning plus pruning, T18= 18x18 thinning, C= control. 

3 N= number of trees sampled per plot. 

4 DBH= diameter at breast height. 

5 Ht= total tree height. 

6 Lcht= lowest live crown height. 
9 

When analyzed (see Table 6), no significant 

treatment effect was found for dbh or height. A 

very significant treatment effect was found for 

lower crown height (Prob. F=0.0079). T-tests 

for comparison of treatments found significant 

differences between T12P and T12 (Adj. Prob. 

T=0.1095); between T12P and T18 (Adj. Prob. 

T=0.0092); and between T12P and Control (Adj. 

Prob. T=0.0145). These comparisons show that 

the pruning was successful at lifting the crowns 

significantly higher than the crowns in the other 

three treatments. 

TABLE 6. Treatment effects for tree measurements immediately after treatment (Sept. 

2004). 

Dependent = DBH1 Ht2 Lcht3

-2 log likelihood 55.3 129.0 91.5 

AIC 67.3 141.0 103.5 

Treatments/sig 0.2433 0.2106 0.00794

Treatment T12 

Adjusted means 4.5754 21.2893 6.2233 

Treatment T12P 

Adjusted means 3.7932 18.0977 8.1761 

Treatment T18 

Adjusted means 4.0351 18.0442 4.9682 

Treatment C 

Adjusted means 3.7464 17.9255 5.2041 

1 DBH= diameter at breast height. 

2 Ht= total tree height. 

3 Lcht= lowest live crown height. 

4 Significant at α<=0.10 
10 

2006 Remeasurement

Plot means for Elytroderma measurements are 

shown in Table 7. Average plot conditions of 

the six replications were combined by treatment, 

just like at plot establishment, and an F-test for 

differences between treatment means for each 

plot variable was done. Four trees died after plot 

establishment: one in stand 2.7; two in 2.13A; 

and one in 2.7C. A cause of mortality could not 

be determined for any of these four trees. 

Table 7. Treatment means for 2006 Ely measurements. 

Stid1 Treat2 N3 Etop4 Emid5 Ebot6 ECrown7 EStem8 ElySum9 ElyPres10

2.11A T12 50 .00 .12 .68 1.06 .16 .80 .60 

2.1B T12 51 .00 .00 .04 .63 .02 .04 .04 

2.4A T12 50 .00 .02 .16 .98 .66 .18 .18 

2.4B T12 51 .00 .14 .43 1.14 .49 .57 .39 

2.7 T12 4911 .00 .16 .69 1.14 .12 .86 .66 

2.9B T12 50 .00 .00 .00 .88 .00 .00 .00 

 

2.10 T12P 50 .00 .00 .08 .86 .02 .08 .08 

2.13A T12P 4811 .00 .00 .02 .56 .02 .02 .02 

2.1A T12P 50 .00 .00 .00 .12 .00 .00 .00 

2.4C T12P 50 .04 .08 .14 .90 .66 .26 .14 

2.5 T12P 50 .00 .00 .20 .94 .42 .20 .20 

2.6B T12P 51 .00 .00 .22 .71 .39 .22 .22 

 

2.11B T18 50 .00 .02 .30 .98 .04 .32 .30 

2.12 T18 50 .00 .00 .00 .48 .00 .00 .00 

2.13B T18 50 .00 .00 .00 .70 .00 .00 .00 

2.3 T18 50 .00 .02 .28 .98 .02 .30 .22 

2.6A T18 51 .00 .00 .22 .86 .16 .22 .22 

2.9A T18 50 .00 .00 .00 .96 .06 .00 .00 

 

2.10C C 50 .00 .00 .00 1.04 .04 .00 .00 

2.12C C 50 .00 .00 .02 .70 .00 .02 .02 

2.3C C 51 .00 .00 .25 .94 .12 .25 .22 

2.4AC C 50 .00 .06 .36 1.08 .34 .42 .30 

2.5C C 50 .00 .00 .02 .94 .04 .02 .02 

2.7C C 4911 .02 .12 .43 1.04 .29 .57 .34 

1 Stid= stand identification number used by Darby Ranger District. 

2 Treat= Treatment; T12= 12x12 thinning, T12P= 12x12 thinning plus pruning, T18= 18x18 thinning, C= control. 

3 N= number of trees sampled per plot. 

4 Etop= Elytroderma rating in top 1/3 of crown. 

5 Emid= Elytroderma rating in middle 1/3 of crown. 

6 Ebot= Elytroderma rating in bottom 1/3 of crown. 

7 Ecrown= portion of red needles in crown. 

8 Estem= Elytroderma rating in stem of tree. 

9 Elysum= Etop+Emid+Ebot 

10 ElyPres= if Elysum>0, then tree given a 1 for ElyPres, otherwise=0. 

11 Number reflects mortality from unknown cause(s). Means were adjusted accordingly. 

 
11 

Table 8a and 8b contain the analysis data for the 

Elytroderma measurements. Ecrown was found 

to have a significant treatment effect (Prob. 

F=0.0146). The T-test for comparisons between 

the four treatments found a significant adjusted p 

value for the comparison of treatment T12P with 

T12 (Adj. Prob. T=0.0133) and between T12P 

and Control (Adj. Prob. T=0.0367), and was 

nearly significant between T12P and T18 (Adj. 

Prob. T=0.1126). Elypres was found to have a 

significant treatment effect (Prob. F=0.0975). A 

simple T-test found a significant difference 

between treatment T12 and each of the other 

three treatments, but no significant adjusted p 

values were found when all combinations of 

treatments were compared. The adjusted mean 

for elypres in treatment T12 is larger than the 

adjusted means in the other treatments (Table 

8b). 

Table 8a. Treatment effects 1.5 years after treatment (July 2006), for Elytroderma measurements only. 

Dependent = Etop1

 Emid2 Ebot3

-2 log likelihood -161.8 -89.8 -19.4 

AIC -149.8 -77.8 -7.4 

Treatments/sig 0.4333 0.1425 0.1765 

Treatment T12 

Adjusted means -0.0006 0.0556 0.2982 

Treatment T12P 

Adjusted means 0.0068 0.0212 0.1635 

Treatment T18 

Adjusted means 0.0003 0.0178 0.1385 

Treatment C 

Adjusted means 0.0035 0.0287 0.1564 

1 Etop= Elytroderma rating in top 1/3 of crown. 

2 Emid= Elytroderma rating in middle 1/3 of crown. 

3 Ebot= Elytroderma rating in bottom 1/3 of crown. 

Table 8b. Treatment effects 1.5 years after treatment (July 2006), for Elytroderma measurements only. 

Dependent = Ecrown1 Estem2

 Elysum3 Elypres4

-2 log likelihood -20.5 -18.5 -10.6 -25.9 

AIC -8.5 -6.5 1.4 -13.9 

Treatments/sig 0.01465 0.1843 0.1727 0.09755

Treatment T12 

Adjusted means 0.9559 0.1931 0.3513 0.2817 

Treatment T12P 

Adjusted means 0.7026 0.2614 0.1937 0.1579 

Treatment T18 

Adjusted means 0.8654 0.1005 0.1583 0.1294 

Treatment C 

Adjusted means 0.9126 0.1233 0.1884 0.1261 

1 Ecrown= portion of red needles in crown. 

2 Estem= Elytroderma rating in stem of tree. 

3 Elysum= Etop+Emid+Ebot 

4 ElyPres= if Elysum>0, then tree given a 1 for ElyPres, otherwise=0. 

5 Significant at α<=0.10 
12 

DISCUSSION 

Plot Establishment 

Ideally, no significant differences would exist 

between the average pre-treatment plot 

conditions. But this is not the case. There is a 

significant difference for ecrown, but this may 

turn out to be a poor measurement of 

Elytroderma infections. There are many other 

agents that will turn the needles red, including 

other needle diseases and feeding by defoliating 

insects. The more important significant 

treatment effect is elypres. But, T-tests indicate 

there is no significant difference when the four 

treatments are compared to each other. 

The significant treatment effect of lcht at pretreatment indicates the trees in the plots selected 

for the T12 treatment may be bigger than the 

trees in the plots selected for the other 

treatments. This treatment effect on lcht still 

existed after treatment, but was due to the lower 

crowns being significantly higher in the pruned 

plots, thus masking the naturally higher crowns 

in the T12 plots. It is noteworthy that no 

treatment effect was found for dbh or height 

before or after treatment. 

2006 Remeasurement 

The significant treatment effect for ecrown for 

the T12P treatment seems logical. Ecrown is a 

measurement of red needles throughout the 

crown. Needle diseases, including Elytroderma, 

tend to be worse in the lower crown and lessen 

towards the top. Trees that have had the lower 

crowns removed would also have had that 

portion of the crown more susceptible to needle 

diseases removed, thus lowering the overall 

amount of red needles in the crown. This is a 

benefit expected in the short term with pruning, 

and hoped for in the long term. Successive 

measurements will reveal if this trend continues. 

The significant treatment effect for elypres is a 

bit more confusing. Subsequent T-tests found no 

significant adj. p values, but there are significant 

p values before adjustment. These indicate there 

are more trees with systemic infections from 

Elytroderma in the T12 treatment when 

compared to each of the other 3 treatments, but 

does not indicate that there are more Elytroderma 

infections within each tree. It will be interesting 

to see if this trend continues in future 

measurements. 

Acknowledgements

Statistical support was provided by Michael A. 

Marsden with Information Technology Experts, 

Inc. through a contract with Forest Health 

Technology Enterprise Team in Fort Collins, 

Colorado. Michael also provided constructive 

review comments on the entire report. Field 

work was accomplished by R1 Forest Health 

Protection (FHP) seasonal crews with occasional 

assistance from FHP personnel. Stand 

treatments that allowed this project to be 

undertaken were funded through USDA Forest 

Service, Forest Health Protection Suppression 

Project Funding. 
13 

LITERATURE CITED 

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ponderosa pine in the Pacific Northwest. USDA 

Forest Service Res. Pap. PNW-69. Pacific 

Northwest Forest and Range Experiment Station, 

Portland, OR. 46 pp., illus. 

Childs, T. W., K. R. Shea, and J. L. Stewart. 

1971. Elytroderma Disease of Ponderosa Pine. 

USDA Forest Service, Forest Pest Leaflet No. 

42. U.S. Government Printing Office. 6 pp. 

Hawksworth, F.G. 1977. The 6 class dwarf 

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(unpublished report). 

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Scharpf, R.F. and R. V. Bega. 1988. 

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