!

Solar Treatments for Reducing

Survival of Mountain Pine

Beetle in Infested Ponderosa

and Lodgepole Pine Logs

José F. Negrón

Wayne D. Shepperd

Steve A. Mata

John B. Popp

Lance A. Asherin

Anna W. Schoettle

John M. Schmid

David A. Leatherman
Abstract

Negrón, José F.; Shepperd, Wayne A.; Mata, Steve A.; Popp, John B.; Asherin, Lance A.; Schoettle, Anna W.; Schmid, John

M.; David A. Leatherman. 2001. Solar treatments for reducing survival of mountain pine beetle in infested ponderosa

and lodgepole pine logs. Res. Pap. RMRS-RP-30. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky

Mountain Research Station. 11 p.

Three experiments were conducted to evaluate the use of solar radiation for reducing survival of mountain pine beetle

populations in infested logs. Ponderosa pine logs were used in experiments 1 and 2 and lodgepole pine logs were used in

experiment 3. Experiment 1 comprised three treatments: (1) one-layer solar treatment without plastic sheeting and logs rotated

one-third of a turn once a week; (2) two-layer solar treatment with plastic sheeting; and (3) two-layer solar treatment without

plastic sheeting. For experiment 2, two additional one-layer treatments were added: one-layer treatment with plastic sheeting

and no rotation and a one-layer with no plastic sheeting and no rotation. Experiment 3 included all the above-mentioned onelayer treatments only. For all experiments, brood density per 0.05 m2 (0.5 ft2

) was estimated before and after treatment and

analyzed using repeated measures analysis of variance. Subcortical temperatures were monitored in one replicate of all

treatments in all experiments. In experiment 2, phloem moisture was monitored before and after treatment in uninfested logs.

All treatments in all experiments caused drastic reductions in brood survival. In experiment 1, the one-layer treatment with the

logs rotated once a week significantly reduced brood survival compared to the two-layer without plastic sheeting treatment but

was not different from the two-layer with plastic sheeting treatment. There were no differences in brood survival after treatment

associated with any treatments in experiments 2 and 3. In all experiments brood survival was consistently reduced in the aspects

of the logs exposed to the sun. Maximum temperatures were consistently higher in the treatments with plastic sheeting, the

exposed surfaces of the logs to the sun, and the upper layer of logs in the two-layer treatments. No differences were detected

in phloem moisture content in uninfested logs before and after treatment in experiment 2, suggesting that heat is directly

responsible for the observed reductions in survival. We conclude that solar treatments are an effective alternative for reducing

mountain pine beetle survival in infested ponderosa and lodgepole pine logs.

Keywords: mountain pine beetle, Dendroctonus ponderosae, solar treatments, mountain pine beetle control

Authors

José F. Negrón, Wayne D. Shepperd, Steve A. Mata,

John B. Popp, Lance A. Asherin, Anna W. Schoettle

USDA Forest Service

Rocky Mountain Research Station

240 W. Prospect

Fort Collins, CO 80526

John M. Schmid

4009 Bingham Hill Rd.

Fort Collins, CO 80521

David A. Leatherman

Colorado State Forest Service

214 Forestry

Colorado State University

Fort Collins, CO 80523

Cover photos by: José Negrón, upper right; David Leatherman, center and lower right.
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 1

Introduction

Periodic outbreaks of mountain pine beetle (Dendroctonus

ponderosae) cause significant mortality of ponderosa pine (Pinus

ponderosa) and lodgepole pine (Pinus contorta) in Colorado and

other parts of the Western United States. With increased incidence of infested trees, Federal, State, and private land managers

face the predicament of what to do with these trees to prevent or

reduce further infestations. This situation is particularly important in high-value areas such as campgrounds or near private

homes. Under certain circumstances, managers and landowners

can salvage previously killed and currently infested trees. There

are no chemicals available for killing mountain pine beetles in

infested trees. Preventive insecticide applications can be used to

protect high value trees from attack. Nonetheless, chemicals available for this use are limited, and many landowners are reluctant

to use insecticides because of environmental concerns.

The use of solar heat or radiation has been considered as

an option for many decades (Craighead 1920; Graham 1924;

Massey and Wygant 1954; Patterson 1930). Various studies

have examined the use of solar treatments for control of bark

beetles in infested logs. Results from the different studies

exhibit variations in efficacy, depending on the methodology

utilized and the tree species examined. Ips-infested ponderosa pine has been successfully treated in Arizona using 4-mil

clear plastic sheeting (Buffam and Lucht 1968). Average beetle

mortality in slash piles covered with clear plastic sheeting was

89 percent, compared to 11 percent for black plastic sheetingcovered piles and 5 percent for uncovered piles. Average high

temperature recorded under the piles was highest with the clear

plastic at 74.4 °C (165.9 °F). Mitchell and Schmid (1973) tested

solar treatments in Engelmann spruce (Picea engelmannii)

for control of spruce beetle (Dendroctonus rufipennis). That

study found 90 percent or greater mortality in the top surface of logs but no significant mortality on the sides of the

logs. This suggests that direct exposure is important in subsequent mortality in uncovered logs. McCambridge and others (1975) used fumigation treatments with the insecticide

ethylene dibromide in combination with clear 6-mil plastic

sheeting to kill mountain pine beetles in ponderosa pine that

was to be used for firewood in Colorado. Population reduction was complete in insecticide-treated piles. In stacks covered with plastic but not treated with insecticides, population

reduction was small on average but relatively high in the top

of the stack, suggesting that solar radiation contributed to

beetle mortality by increasing temperature to lethal levels.

Holsten and Werner (1993) working with spruce beetle

(Dendroctonus rufipennis)- infested Lutz spruce (Picea x

lutzii) in Alaska indicated that neither clear nor black plastic

sheeting was effective for attaining significant mortality of

that species. Higher bark surface temperatures were obtained

with clear plastic sheeting when compared to black plastic

sheeting or uncovered stacks of infested material. Inner bark

temperature, however, was higher in uncovered stacks. Some

mortality was observed, but temperatures did not reach levels sufficiently high to cause extensive mortality (Holsten

and Werner 1993).

Increasing populations of mountain pine beetle in Colorado have sparked new interest in strategies to treat infested

logs in high-value areas. In the past, practitioners and landowners in Colorado have used different forms of solar radiation treatments for mountain pine beetle. However,

quantitative data to support recommendations are lacking.

Solar Treatments for Reducing Survival of

Mountain Pine Beetle in

Infested Ponderosa and Lodgepole Pine Logs

José F. Negrón

Wayne D. Shepperd

Steve A. Mata

John B. Popp

Lance A. Asherin

Anna W. Schoettle

John M. Schmid

David A. Leatherman
2 USDA Forest Service Res. Pap. RMRS-RP-30. 2001

In this study, we examine the use of solar treatments for reducing survival of mountain pine beetle in infested ponderosa

and lodgepole pine logs in Colorado.

Methods

Study Sites and Experiments

Three experiments were conducted. Experiments 1 and 2

were conducted in ponderosa pine during June and July 1999

and May through July 2000, respectively, on the Canyon Lakes

Ranger District of the Arapaho-Roosevelt National Forest,

Colorado. Experiment 3 was conducted in lodgepole pine

during June and July 2000 on the Sulphur Ranger District of

the Arapaho-Roosevelt National Forest (table 1).

Experiment 1—This experiment comprised three treatments: (1) one-layer solar treatment without plastic sheeting

and rotated one-third of a turn once a week; (2) two-layer

solar treatment with plastic sheeting and no rotation; and (3)

two-layer solar treatment without plastic sheeting and no rotation (fig. 1). The experiment lasted for 6 weeks; installed on

1–2 June 1999 and terminated on 19–20 July 1999. Logs in

the one-layer with rotation treatment were rotated on 11 June,

18 June, 25 June, 1 July, and 9 July.

For the one-layer treatment, seven logs were arranged side

by side on the ground. Logs in this treatment were rotated

one-third of a turn once a week, so that by the end of the

experiment all sides of the logs were fully exposed to the sun

for approximately 2 weeks. Approximately one-third of the

log surface was fully exposed to the sun at any given time.

For the two-layer solar treatment with plastic sheeting, seven

logs were stacked in two layers, with four logs on the lower

layer and three on the upper layer, and the stack covered with

6-mill clear plastic sheeting. The plastic sheeting was sealed

around the edges of the stack with soil. For the two-layer

solar treatment without plastic sheeting, logs were arranged

the same way as for the two-layer solar treatment with plastic

sheeting but were not covered.

Table 1. Species treated, starting and termination dates, and locations for experiments 1 through 3,

Canyon Lakes and Sulphur Ranger Districts, Arapaho and Roosevelt National Forests, Colorado. June–July 1999 and May–July 2000.

Experiment 1 Experiment 2 Experiment 3

_________________________________________________________________________________________________

Species Pinus ponderosa Pinus ponderosa Pinus contorta

Starting date June 1–2, 1999 May 30–June 1, 2000 June 6–7, 2000

Termination date July 19–20, 1999 July 10–12, 2000 July 5–6, 2000

Location Canyon Lakes RD Canyon Lakes RD Sulphur RD

_________________________________________________________________________________________________

Figure 1. Schematics of treatments established in experiments 1

through 3. Circles indicate logs. Logs with shading indicate the

position of the logs where temperature was monitored, Canyon

Lakes and Sulphur Ranger Districts, Arapaho-Roosevelt National

Forest, Colorado, May–July 1999–2000.

Experiment 1: Canyon Lakes 1999

Experiment 3: Sulphur 2000

Schematic of Treatments

1-layer, no plastic sheeting 2-layer, no plastic sheeting

2-layer, with plastic sheeting

Experiment 2: Canyon Lakes 2000

1-layer, no plastic sheeting, with rotation

1-layer, with plastic sheeting, no rotation

1-layer, no plastic sheeting, no rotation

2-layer, no plastic sheeting, no rotation 2-layer, with plastic sheeting, no rotation

1-layer, no plastic sheeting, with rotation

1-layer, with plastic sheeting, no rotation

1-layer, no plastic sheeting, no rotation
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 3

Experiment 2—This experiment incorporated two additional one-layer treatments to the treatments from experiment

1: a one-layer treatment with plastic sheeting and no rotation

and a one-layer treatment without plastic sheeting no log rotation. This experiment also lasted for 6 weeks; installed on

30 May to 1 June 2000 and terminated on 10–12 July 2000.

Logs in the rotated treatment were turned on 9 June, 16 June,

23 June, 29 June, and 3 July. For the one-layer treatments,

five logs were arranged side by side on the ground; for the

two-layer treatments five logs were stacked in two layers, with

three logs on the lower layer and two on the upper layer.

Experiment 3—This experiment included only the onelayer treatments used in experiments 1 and 2 and lasted for 4

weeks; installed on 6–7 June 2000 and terminated on 5–6 July

2000. Logs in the rotated treatment were turned on 16 June

and 26 June, so that by the completion date all sides were

exposed to the sun for approximately 10 days. Five logs were

used for each treatment. The logs were arranged side by side

on the ground.

For all experiments, pines infested with mountain pine

beetle were felled, limbed, and cut into 1.2 m (4 ft) logs. Average tree diameters ± standard error of the mean at breast

height for the three experiments were as follows: experiment

1 — 31.9 ± 0.9 cm (12.5 ± 0.3 inches); experiment 2 — 34.8

± 1.4 cm (13.7 ± 0.6 inches), and experiment 3 — 31.4 ± 0.9

cm (12.3 ± 0.4 inches). The north-facing aspect of each tree

was marked prior to felling and then marked on the end of

each log. The lower five to six logs were used from the felled

trees because this is where mountain pine beetle infestations

tend to concentrate. Logs were kept covered with branches to

prevent overheating prior to pretreatment brood sampling. All

logs were numbered with metal tags and information recorded

on diameter of source tree at breast height and position of the

log in the tree. Numbers ran sequentially starting from the

bottom log, which was about 0.76 m (2.5 ft) from the ground.

Logs less than 15.24 cm (6 inches) outside diameter were not

used because that is about the smallest diameter where mountain pine beetles are likely to be found. Logs were distributed

into stacks based on the diameter of the source tree at breast

height and log location in order to create stacks of similar

composition and to represent each source tree in multiple

stacks. Each treatment was then randomly assigned to one of

the stacks.

For consistency, logs were always placed with the north

aspect oriented up and the south aspect oriented toward the

ground, and these orientations will be referred to hereafter as

top and bottom aspect, respectively. For the one-layer with

rotation treatments, the north side began in the top orientation. Because rotation resulted in log orientation changes during the experiment, the north and south terminology is retained

for this treatment only.

Four replications of each treatment were conducted for each

experiment. The replications were within 3 miles of one another. All logs used for each replication came from the same

group of infested trees. Each replication was in an area with a

high degree of sun exposure, such as a canopy gap or small

meadow, in proximity to the source area of the trees.

Brood Sampling

To evaluate the effectiveness of treatments, brood sampling

was conducted in all logs before and after treatment. For each

pre- and posttreatment sampling, two 15.2 X 30.5 cm (6 X 12

inches) samples with a surface area of 0.05 m2 (0.5 ft2) were

collected from each log. One sample was taken from the north

aspect and one from the south aspect and on opposite ends of

each log. Live mountain pine beetle larvae (and a few pupae)

were counted before treatment. At the conclusion of the experiment, two additional 15.2 X 30.5 cm (6 X 12 inches)

samples were collected, again one each from the north and

south sides and on opposite ends of each log, to determine the

number of live mountain pine beetle immature or brood adult

per 0.05 m2 (0.5 ft2) of bark surface. Hereafter, these counts

will be referred to as pretreatment and posttreatment brood

densities.

Temperature Monitoring

Temperature monitoring and recording equipment was set

up for one replicate of each experiment. Temperature data were

collected for all treatments in the replicate by placing YSI

thermilinear thermistor networks into the inner bark in the top

and bottom of one or two logs in each treatment. The thermistors were connected to a Campbell Scientific 21X

micrologger (Logan, UT). A temperature reading was taken

every minute, and hourly averages were stored by the

micrologger. From these data we obtained the maximum hourly

average per day (hereafter referred as maximum temperature).

The equipment was set on 4 June 1999 for experiment 1; 2

June 2000 for experiment 2; and 6 June 2000 for experiment

3. Thermistors in the one-layer treatment with rotation were

reset in the top and bottom of the log when the log was turned

weekly.

Phloem Moisture Analysis

While conducting posttreatment brood sampling for experiment 1 in 1999, we noticed that logs in the one-layer with

rotation treatment appeared to be much drier than in the rest

of the treatments. We hypothesized that drying of the phloem

may have contributed to reduced insect survival and decided

to examine this further. In experiment 2, we felled an uninfested

tree for each replicate. The tree was also cut into 1.2 m (4 ft)

logs. An 8.9 X 8.9 cm (3.5 X 3.5 inch) phloem sample was

collected from the north and the south aspect of each log, just

as was done with the brood sampling. After the phloem samples

were collected, the logs were randomly assigned to the different treatments. One log was placed in each of the one-layer
4 USDA Forest Service Res. Pap. RMRS-RP-30. 2001

treatments. Two logs were placed in each of the two-layer treatments, one each on the upper and lower layers.

The outer bark was removed from each sample and the

phloem wrapped in aluminum foil, placed in a cooler, and

brought to the laboratory. The samples were weighed and the

sample area measured using video imaging (Delta-T Devices,

Cambridge, England) and sample thickness measured with a

caliper. The samples were dried in an oven at 65 °C (149 °F)

for 48 hours and dry weight obtained. Moisture content was

calculated in a dry weight basis (mg H2

O/gm dry weight of

phloem tissue). After drying, the samples were weighed again.

With this information, we calculated percent moisture content based on dry weight. Volume of the fresh sample was also

calculated. This process was repeated after completion of the

study to obtain posttreatment data on the same variables.

Data Analysis

When planning for experiments 2 and 3, we were faced

with a considerable increase in the number of samples needed

to adequately measure pre- and posttreatment brood densities. The observed data collected in experiment 1 were assumed to represent the target population. Using these data, a

bootstrap resampling simulation was conducted to assess the

possible bias and loss of precision associated with reduced

sample sizes (Efron and Tibshirani 1993). Hypothetical

samples were drawn with replacement from the observed 1999

data and an estimate of the mean and associated standard error obtained for each sample. A total of 1,000 samples were

drawn for each sampling level of n=3 to n=7. The distribution

of the estimates and standard errors were then displayed using box plots. The potential for bias and lack of precision associated with particular sample sizes can be assessed by noting

whether the mean hypothetical estimate is close to the observed estimate in 1999, whether the box is symmetric about

the “true” estimate, the length of the box (which includes 50

percent of the hypothetical estimates), and the size of potential large deviations from the “true” estimate as represented

by the length of the whiskers and presence of individual outliers. The analysis indicated that using five logs per stack would

be adequate. Therefore, in experiments 2 and 3, all stacks used

contained five logs. The rest of the methodology was the same

as in experiment 1.

Repeated measures analysis of variance was used to examine differences between pre- and posttreatment brood densities. Deviations from normality in brood differences were

examined with Q-Q plots and the Kolmogorov-Smirnov test

for normality. The test indicated no deviations from normality

for any of the experiments. Treatment and aspect main effects

and their interactions were examined. To examine the effect of

layer in the stack, a separate analysis was conducted where only

the two-layer treatments were included. Tukey’s HSD test was

used to evaluate differences when comparing three or more means.

Because we measured live mountain pine beetle densities before

and after treatment, larger differences are associated with decreased survival.

Repeated measures analysis of variance was also conducted

to examine differences in moisture content of the uninfested logs

before and after treatment in experiment 2. Because of the variability caused by variations in sample dimensions and phloem

thickness, the dry weight on a volume basis of the samples was

used as a covariate.

Maximum temperature data were examined with analysis of

variance to determine if significant variation was associated with

treatments, aspects, layers, and aspect within layers. A paired ttest was conducted to compare pretreatment brood densities between the north and the south aspect of the logs.

Results

Experiment 1

In experiment 1, the difference between pre- and posttreatment brood densities was significantly larger (indicating reduced survival) in the one-layer with rotation treatment when

compared to the two-layer with no plastic sheeting treatment,

but it was not different from the two-layer with plastic sheeting treatment (table 2A).

Mean differences in brood densities associated with aspect

were observed only in the two-layer with plastic sheeting treatment where reduced survival was observed in the top aspect of

the logs. There were no mean differences in brood densities detected between layers for the two-layer treatments (table 2B).

Survival was significantly reduced in the top aspects of both

layers of the two-layer with plastic sheeting, but no differences

were observed in aspects within layers for the two-layer with no

plastic sheeting treatment (table 2C).

Maximum temperatures were significantly higher in the

upper layer (40.9 ± 1.6 °C) of the two-layer with plastic sheeting

treatment when compared to the upper layer of the two-layer

with no plastic treatment (25.1 ± 1.0 °C) and the one-layer with

rotation treatment (26.1 ± 0.9 °C) (not shown in table). Maximum temperatures were significantly higher in the top aspect of

the logs in the one-layer treatment (table 3B). For the two-layer

treatments only, maximum temperatures were higher in the treatment with plastic sheeting, the top aspect of the logs, and in the

upper layers (table 3C). For the aspect and layer effect by twolayer treatments, maximum temperatures were higher in the top

aspects of both two-layer treatments, and in the upper layer of

the two-layer with plastic sheeting treatment (table 3D). For the

aspect within layer effect by two-layer treatments, for both treatments there were higher maximum temperatures in the top aspects of both layers (table 3E).

Experiment 2

Although survival was less in the one-layer with rotation

treatment, differences between pre- and posttreatment brood

densities were not significant among any of the treatments
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 5

(table 4A). Mean differences between pre- and posttreatment

brood densities indicate that for all treatments there was significantly less survival in the top aspects and in the north aspect of the one-layer with rotation treatment. For the two-layer

treatments there were no mean differences in brood densities

detected between layers (table 4B). For the two-layer treatment with plastic sheeting, there was also reduced survival in

the top aspect of the upper layer of logs. No mean differences

in brood densities were observed in aspect within layers for

the lower layer of the two-layer with plastic sheeting treatment or for any layer of the two-layer with no plastic sheeting

treatment (table 4C).

Temperature data for the one-layer treatments indicated

higher maximum temperatures for the one-layer with plastic

sheeting treatment and higher maximum temperatures in the

top aspects across all treatments (table 3A). The top aspects in

the one-layer treatments also had higher maximum temperatures for all treatments (table 3B). For the two-layer treatments,

higher maximum temperatures were observed in the two-layer

with plastic sheeting treatment, in the top aspects, and in the

upper layer across all two-layer treatments (table 3C). For the

aspect and layer effects for the two-layer treatments: for the

Table 2. Mean (standard error of mean) pretreatment, posttreatment, and difference in brood densities

per 0.05 m2 (0.5 ft2) for treatments, aspects, and layers in experiment 1, Canyon Lakes Ranger District, Arapaho and Roosevelt National Forests, Colorado. June–July 1999.

_________________________________________________________________________________________________ Pretreatment Posttreatment

brood density brood density Mean differencea

_________________________________________________________________________________________________

A. Treatment main effect

1-layer with rotation 40.6 (3.0) 0.6 (0.3) 39.9 (3.0) a

2-layer with plastic sheeting 37.5 (3.5) 7.5 (1.6) 30.0 (3.7) ab

2-layer no plastic sheeting 35.4 (3.1) 14.2 (2.6) 21.2 (3.8) b

B. Aspect and layers effects by treatments

1-layer with rotation North 43.9 (4.1) 1.1 (0.5) 42.8 (4.2) a

South 37.2 (4.2) 0.1 (0.1) 37.1 (4.3) a

2-layer with plastic sheeting Top 45.4 (4.9) 2.3 (1.1) 43.1 (4.5) a

Bottom 29.6 (4.6) 12.7 (2.8) 16.9 (4.8) b

 Upper 33.0 (5.5) 4.2 (2.2) 28.8 (6.2) a

 Lower 40.9 (4.5) 10.0 (2.3) 30.8 (4.6) a

2-layer no plastic sheeting Top 38.3 (4.7) 10.1 (3.2) 28.2 (5.8) a

Bottom 32.5 (4.1) 18.4 (3.9) 14.1 (4.5) a

 Upper 30.5 (3.7) 5.2 (1.6) 25.3 (3.4) a

 Lower 39.0 (4.7) 21.0 (4.0) 18.0 (6.1) a

_________________________________________________________________________________________________

C. Aspects within layers for two-layer treatments

2-layer with plastic sheeting Upper:top 43.6 (7.1) 0.1 (0.1) 43.5 (7.1) a

Upper:bottom 22.4 (7.6) 8.3 (4.2) 14.2 (8.5) b

 Lower:top 46.8 (6.9) 4.0 (1.8) 42.8 (6.0) a

 Lower:bottom 35.0 (5.5) 16.1 (3.6) 18.9 (5.7) b

2-layer no plastic sheeting Upper:top 32.5 (5.8) 3.2 (2.4) 29.3 (4.9) a

Upper:bottom 28.5 (4.8) 7.2 (2.1) 21.3 (4.5) a

 Lower:top 42.6 (7.1) 15.3 (5.0) 27.4 (9.6) a

 Lower:bottom 35.4 (6.2) 26.8 (6.0) 8.7 (7.0) a

a Treatment, aspect, layer, and aspect within layer mean difference within each treatment followed by the same letter

are not significantly different at the P = 0.05 level. ANOVA for two means and Tukey’s HSD test for more than two

means. Except for treatment means, comparisons are made between pairwise indented effects.

two-layer with plastic sheeting treatment, higher maximum

temperatures were observed in the top aspects and in the upper layer; for the two-layer no plastic sheeting treatment, no

differences in maximum temperatures were observed for the

aspect effect but higher maximum temperatures were observed

in the upper layer (table 3D). For the aspect within layer by

two-layer treatments, higher maximum temperatures were

observed in the top aspect of both layers for the two-layer

with plastic sheeting treatment but no differences were observed for aspect within layer for the two-layer no plastic sheeting treatment (table 3E).

Phloem Moisture Analysis—Repeated measures analysis

of variance indicated no mean differences in phloem moisture content across time (before and after treatment) (F = 0.71;

df = 1, 15; P > 0.41), or treatment by time (F = 0.53; df = 4,

15; P > 0.71), or aspect by time (F = 0.0; df = 1, 15; P > 0.99).

Overall pretreatment and posttreatment means (standard error of the mean) for moisture content across all treatments,

aspects, and layers were 117.8 (1.8) and 142.2 (5.6), respectively.
6 USDA Forest Service Res. Pap. RMRS-RP-30. 2001

Table 3. Mean (standard error of mean) daily maximum hourly average recorded in experiments 1 through 3 for treatments,

aspects, and layers, Canyon Lakes and Sulphur Ranger Districts, Arapaho and Roosevelt National Forests, Colorado.

June–July 1999 and May–July 2000. a

Experiment 1 Experiment 2 Experiment 3

A. Treatment and aspect main effects

1-layer rotated 26.1 (0.9) 33.0 (1.3) b 28.1 (1.4) b

1-layer with plastic sheeting NA 40.0 (1.4) a 37.6 (2.0) a

1-layer no rotation NA 31.3 (1.3) b 29.3 (1.5) b

Top NA 49.3 (0.7) a 47.9 (0.9) a

Bottom NA 20.2 (0.4) b 15.4 (0.3) b

_________________________________________________________________________________________________

B. Aspect main effect by treatments

1-layer rotated

Top 36.5 (1.0) a 46.1 (1.2) a 41.4 (1.1) a

Bottom 15.7 (0.5) b 19.9 (0.9) b 14.8 (0.8) b

1-layer with plastic sheeting

Top NA 55.9 (1.2) a 58.0 (1.2) a

Bottom NA 24.2 (0.3) b 17.3 (0.3) b

1-layer no rotation

Top NA 45.9 (1.1) a 44.3 (1.1) a

Bottom NA 16.6 (0.3) b 14.2 (0.4) b

_________________________________________________________________________________________________

C. Two-layer treatments only: treatment, aspect, and layer main effects

2-layer with plastic sheeting 32.5 (1.1) a 36.3 (1.2) a NA

2-layer no plastic sheeting 24.3 (0.8) b 33.7 (1.4) b NA

Top 37.4 (0.9) a 40.1 (1.4) a NA

Bottom 19.4 (0.5) b 30.0 (1.4) b NA

Upper 33.0 (1.1) a 46.2 (1.2) a NA

Lower 23.8 (0.8) b 23.8 (0.6) b NA

_________________________________________________________________________________________________

D. Two-layer treatments by treatments: aspects and layer effects

2-layer with plastic sheeting

Top 41.6 (1.5) a 46.5 (1.8) a NA

Bottom 23.4 (0.8) b 26.1 (0.6) b NA

Upper 40.9 (1.6) a 43.7 (2.0) a NA

Lower 24.0 (0.8) b 28.9 (0.8) b NA

2-layer no plastic sheeting

Top 33.2 (0.9) a 33.6 (1.9) a NA

Bottom 15.5 (0.5) b 33.9 (2.1) a NA

Upper 25.1 (1.0) a 48.7 (1.4) a NA

Lower 23.6 (1.3) a 18.7 (0.4) b NA

_________________________________________________________________________________________________

E. By treatment and layer: aspect effect

2-layer with plastic sheeting

Upper:top 53.0 (1.7) a 58.6 (2.0) a NA

Upper:bottom 28.9 (0.8) b 28.7 (0.8) b NA

Lower:top 30.1 (0.9) a 34.3 (0.9) a NA

Lower:bottom 17.9 (0.5) b 23.5 (0.7) b NA

2-layer no plastic sheeting

Upper:top 31.9 (1.2) a 47.7 (1.8) a NA

Upper:bottom 18.3 (0.7) b 49.8 (2.1) a NA

Lower:top 46.9 (1.3) a 19.6 (0.7) a NA

Lower:bottom 12.7 (0.5) b 17.9 (0.5) a NA

a Means within columns by and indentation level followed by the same letter are not significantly different at the P = 0.05 level. NA means

treatment not in that experiment. ANOVA for two means and Tukey’s HSD test for more than two means.
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 7

Table 4. Mean (standard error of mean) pretreatment, posttreatment, and difference in brood densities per 0.05 m2

 (0.5 ft2) for

treatments, aspects, and layers in experiment 2, Canyon Lakes Ranger District, Arapaho and Roosevelt National Forests,

Colorado. June–July 2000.

Pretreatment Posttreatment

brood density brood density Mean differencea

A. Treatment main effect

1-layer with rotation 37.7 (5.1) 0.7 (0.4) 37.0 (5.1) a

1-layer with plastic sheeting 31.0 (3.7) 5.7 (1.6) 25.3 (4.4) a

1-layer with no rotation 41.8 (4.7) 10.3 (3.2) 31.5 (6.2) a

2-layer with plastic sheeting 35.8 (3.9) 7.0 (2.3) 28.8 (4.2) a

2-layer no plastic sheeting 36.3 (3.9) 12.0 (2.8) 24.3 (4.2) a

_________________________________________________________________________________________________

B. Aspect and layer effects by treatment

1-layer with rotation North 50.3 (8.2) 0.3 (0.2) 50.1 (8.2) a

South 25.1 (4.6) 1.1 (0.7) 24.0 (4.5) b

1-layer with plastic sheeting Top 37.9 (6.2) 0.0 (0.0) 37.9 (6.2) a

Bottom 24.1 (3.8) 11.4 (2.7) 12.7 (4.8) b

1-layer no rotation Top 56.1 (6.1) 0.0 (0.0) 56.1 (6.1) a

Bottom 27.4 (5.8) 20.6 (5.5) 6.8 (7.5) b

2-layer with plastic sheeting Top 44.9 (6.4) 7.5 (4.2) 37.4 (7.3) a

Bottom 26.8 (3.8) 6.5 (2.1) 20.3 (3.5) b

 Upper 38.3 (7.2) 2.3 (1.1) 36.0 (7.4) a

 Lower 34.1 (4.6) 10.1 (3.7) 24.0 (4.9) a

2-layer no plastic sheeting Top 43.7 (5.9) 8.1 (3.6) 35.6 (6.1) a

Bottom 28.8 (4.5) 15.9 (4.3) 12.9 (4.7) b

 Upper 33.9 (7.7) 6.9 (3.2) 26.9 (8.1) a

 Lower 37.8 (4.0) 15.4 (4.1) 22.5 (4.6) a

_________________________________________________________________________________________________

C. Aspect within layer for two-layer treatments

2-layer with plastic sheeting Upper:top 52.6 (11.0) 0.1 (0.1) 52.5 (11.0) a

Upper:bottom 24.0 (6.7) 4.5 (1.9) 19.5 (6.2) b

 Lower:top 39.7 (7.7) 12.4 (6.8) 27.3 (8.9) a

 Lower:bottom 28.6 (4.7) 7.8 (3.3) 20.8 (4.4) a

2-layer no plastic sheeting Upper:top 42.0 (12.7) 0.0 (0.0) 42.0 (12.7) a

Upper:bottom 25.8 (8.7) 13.9 (5.6) 11.9 (7.5) a

 Lower:top 44.8 (5.7) 13.5 (5.5) 31.3 (5.9) a

 Lower:bottom 30.8 (5.1) 17.3 (6.3) 13.6 (6.2) a

a Treatment, aspect, layer, and aspect within layer mean difference within each treatment followed by the same letter are not significantly

different at the P = 0.05 level. ANOVA for two means and Tukey’s HSD test for more than two means. Except for treatment means,

comparisons are made between pairwise indented effects.
8 USDA Forest Service Res. Pap. RMRS-RP-30. 2001

Experiment 3

We observed reduced survival in the one-layer with rotation treatment, but mean differences in brood densities were

not significant among any of the treatments (table 5A). Mean

differences in brood densities indicated significantly reduced

survival in the north aspect of the one-layer with rotation treatment and in the top aspects of the one-layer with plastic sheeting and the one-layer with no rotation treatment (table 5B).

Temperature data indicated higher maximum temperatures

for the one-layer with plastic sheeting treatment and the top

aspect across all treatments (table 3A). For each treatment

the top aspects had higher maximum temperatures (table 3B).

Pretreatment Brood Densities by Aspect

In all experiments pretreatment brood densities per 0.05 m2

(0.5 ft2) of bark surface were significantly higher in the north

aspect of the logs compared to the south (experiment 1, t = 3.3,

df = 83, P < 0.001; experiment 2, t = 6.6, df = 98, P < 0.0001;

experiment 3, t = 8.7, df = 58, P < 0.0001). Mean pretreatment

brood densities (standard error of the mean) in experiment 1

were 42.5 (2.6) for the north aspect and 33.1 (2.5) for the south

aspect. In experiment 2, average densities were 46.5 (2.9) for

the north aspect and 26.4 (2.0) for the south aspect. For experiment 3 the mean brood densities were 49.3 (3.2) in the north

aspect and 20.0 (2.4) in the south aspect.

Discussion

Seasonal trends of mountain pine beetle in the Black Hills,

South Dakota, indicated that brood densities declined precipitously shortly after the trees were attacked and the brood

established (Schmid 1972). Conversely, little change in brood

densities occurred after late May. Therefore, we believe that

the pretreatment brood densities obtained in our study represent potentially emerging populations and that the subsequent

reductions observed in posttreatment brood densities satisfactorily characterize treatment effects.

All treatments in all experiments for both tree species and

across all aspects and layers caused drastic reductions in

mountain pine beetle survival in the infested logs. The highest treatment survival observed was 40 percent for the twolayer with no plastic sheeting in experiment 2. The one-layer

with rotation treatment was significantly better than one other

treatment evaluated only in experiment 1. In experiments 2

and 3, the one-layer with rotation treatments had the largest

reductions in brood counts, but the differences were not significant. In all experiments, brood densities were consistently

lower after treatment in the top aspects of the treated logs.

With some exceptions, higher maximum temperatures were

observed in the top aspects of the logs, in the upper layers of

the two-layer treatments, and in the treatments covered with

plastic sheeting. These higher maximum temperatures were

associated with reduced mountain pine beetle survival in the

top aspects of the logs and the upper layers of the two-layer

treatments but not in the two-layer treatments with plastic

sheeting.

The lack of differences in phloem moisture before and after treatment in experiment 2 suggests that observed reductions in brood survival may primarily be a function of increased

temperature. This statement needs to be cautioned. We examined phloem moisture in uninfested trees because it is difficult to obtain an adequate sample for moisture content analysis

from an infested tree. The uninfested tree is different from

the infested tree, which has been losing moisture from the

time that it dies from beetle attack soon after infestation in the

summer. In standing infested trees, moisture loss is not a limiting factor for mountain pine beetle populations as evidenced

by their natural emergence from such trees. However, a felled

infested tree has more tree surface area directly exposed to

radiation, so phloem drying beyond some threshold may become an important factor by itself or in combination with high

temperature.

Mitchell and Schmid (1973) conducted a laboratory study

and indicated that inner bark temperatures of 49 °C (120 °F)

for 30 minutes caused 92 percent mortality of spruce beetle in

5 ft logs, while inner bark temperatures of 46.1 °C (115 °F)

caused 83 percent mortality. Mitchell and Schmid (1973) recognized that, within the range of temperatures examined, temperature levels were important in determining mortality levels.

Nevertheless, they suggested that the duration of specific high

temperatures was more important than the temperature itself.

Our study was not designed with the intent of identifying

temperature thresholds that may be responsible for causing

mortality. Nevertheless, mountain pine beetle survival appears

related to maximum bark temperatures. When maximum temperatures reached or surpassed 40 °C (104 °F), observed survival was less than 10 percent with only two exceptions: in

experiment 1 in the top aspect of the lower layer for the twolayer with no plastic sheeting treatment, and in experiment 2

in the top aspect of the lower layer of the two-layer with plastic sheeting treatment. When the maximum temperature failed

to reach 40 °C (104 °F), then survival was consistently over

20 percent with one exception: the bottom aspect of the upper

layer for the two-layer with plastic sheeting in experiment 2

(table 6). This critical temperature observed in our study is

not unreasonably different from the lethal temperatures obtained by Mitchell and Schmid (1973).

Management Considerations

Mountain pine beetle most commonly infests the lower 20

to 30 ft of a tree. Felling and bucking an infested tree about 12

inches d.b.h. into 4 ft logs will yield about five to seven logs

for treatment. Under epidemic populations of mountain pine
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 9

Table 6. Percent brood survival of Dendroctonus ponderosae and corresponding maximum temperature (°C) recorded for the

particular surface within treatment for experiments 1 through 3, Canyon Lakes and Sulphur Ranger Districts, Arapaho and

Roosevelt National Forests, Colorado. June–July 1999 and May–July 2000.

Survival (%)a Max Temp (°C)

Experiment 1 2-layer with plastic sheeting Upper:top 0.2 66.7

Upper:bottom 36.8 38.6

Lower:top 8.6 40.3

Lower:bottom 45.9 27.4

2-layer with no plastic sheeting Upper:top 9.8 44.1

Upper:bottom 25.2 29.7

Lower:top 35.8 46.9

Lower:bottom 75.5 25.4

Experiment 2 2-layer with plastic sheeting Upper:top 0.2 73.3

Upper:bottom 18.8 38.1

Lower:top 31.3 42.9

Lower:bottom 27.4 30.8

2-layer with no plastic sheeting Upper:top 0.0 62.6

Upper:bottom 53.9 nab

Lower:top 30.1 26.7

Lower:bottom 56.0 25.2

1-layer with plastic sheeting Top 0.0 69.6

Bottom 70.9 32.6

1-layer no plastic sheeting Top 0.0 62.2

Bottom 47.2 23.4

Experiment 3 1-layer with plastic sheeting Top 4.0 70.4

Bottom 100 25.1

1-layer no plastic sheeting Top 3.5 57.0

Bottom 100 27.7

a Percent survival calculated as ratio of posttreatment brood density to pretreatment brood density for the particular surface within treatment.

Table presents treatments with no rotation only. b

 Thermistor malfunction.

Table 5. Mean (standard error of mean) pretreatment, posttreatment, and difference in brood densities per 0.5 ft2 (0.05 m2) for

treatments and aspects in experiment 3, Sulphur Ranger District, Arapaho and Roosevelt National Forests, Colorado.

May–July 2000.

Pretreatment Posttreatment

brood density brood density Mean differencea

_________________________________________________________________________________________________

A. Treatment main effect

1-layer with rotation 36.5 (4.6) 5.33 (2.5) 31.2 (4.5) a

1-layer with plastic sheeting 33.5 (4.0) 13.1 (3.8) 19.7 (5.2) a

1-layer no rotation 35.0 (4.0) 10.4 (2.8) 24.7 (5.3) a

_________________________________________________________________________________________________

B. Aspect effect by treatment

1-layer with rotation North 52.9 (6.4) 8.2 (4.8) 44.8 (7.2) a

South 20.1 (4.1) 2.5 (1.4) 17.6 (3.3) b

1-layer with plastic sheeting Top 45.8 (5.1) 1.8 (1.8) 43.7 (6.4) a

Bottom 21.3 (5.0) 23.2 (6.2) -1.9 (4.0) b

1-layer no rotation and no plastic sheeting Top 50.6 (5.2) 1.8 (0.6) 48.9 (5.2) a

Bottom 18.6 (3.4) 18.9 (4.9) -0.8 (4.4) b

a

 Treatment and aspect mean difference within each treatment followed by the same letter are not significantly different at the P = 0.05 level.

ANOVA for two means and Tukey’s HSD test for more than two means. Except for treatment means, comparisons are made between

pairwise effects.
10 USDA Forest Service Res. Pap. RMRS-RP-30. 2001

beetle, where groups of five to hundreds of trees are common,

the number of logs to be treated can become overwhelming.

Solar treatments may be appropriate only with small groups

in high value areas.

If plastic sheeting is used to cover stacks of logs, the number of trees that can be treated with one roll of plastic sheeting

will vary. A 10 x 100 ft roll of 6 mil clear plastic sheeting

costs about $35 and weighs about 30 lb. If 4 ft logs are arranged in stacks of five to seven logs, a roll may be enough

for about 10 stacks, for a cost of about $3.50 per stack.

The use of plastic sheeting presents additional challenges.

When the treatments are complete, there is the need to responsibly dispose of the plastic sheeting. We observed ant nests

inside of most stacks treated with plastic sheeting, probably

due to increased humidity and perhaps protection from predators. The ants become problematic in the process of removing

and disposing of the plastic sheeting.

In our study, the use of two-layer treatments was as effective statistically as the one-layer treatments in experiments 2

and 3. However, survival increased from the top to the bottom of a log and from the upper layer to the lower layer in the

stacks. Although, three or more layers were not tested in our

study, we suspect that lethal temperatures may not be reached

beyond the second layer of logs from the top of the stack. If

this is the case, stacks more than two-layers high may not effectively reduce mountain pine beetles in the infested logs.

The one-layer treatments without plastic sheeting seem to

present the best alternative from the perspective of reduced

cost and not having to dispose of plastic sheeting. Although

overall survival in the one-layer treatments without plastic

sheeting was not different between rotated and unrotated treatments, significantly increased survival was observed in the

underside of the unrotated treatments in experiments 2 and 3.

A manager or homeowner that has the time and resources to

turn the logs to expose the different surfaces to the sun may

derive some benefits by reducing beetle survival.

In all experiments, logs contained higher brood densities

in the north aspect of the tree compared to the south. This is

consistent with observations made by McCambridge (1964).

If logs are not to be rotated, the north aspect should face the

sun to expose a larger proportion of the brood to direct solar

radiation. If rotation is to be conducted, the user may want to

plan so that the north aspect is facing the sun during the warmest time during the treatment.

When using solarization, duration of the treatments is important. The experiments conducted at the Canyon Lakes

Ranger District represent conditions in Colorado Front Range

ponderosa pine forests. The experiments lasted for 6 weeks,

which seemed an adequate time to cause reduced survival of

mountain pine beetle brood. While we established our treatments the last week of May and first week of June, a land

manager or homeowner will likely see benefits by installing

treatments earlier in the spring or even in the fall after beetle

flight, if a trained professional can adequately identify successfully attacked trees. On the other hand, the experiment

conducted at the Sulphur Ranger District in a lodgepole pine

forest lasted for only 4 weeks because logistics prevented an

earlier establishment date, which would have been more desirable. In addition, it was important to terminate the experiment before the initiation of beetle flight to preserve the

accuracy of posttreatment brood counts. Had the treatments

been in place for a longer period, further reductions in survival may have been observed. We also observed cool temperatures during part of that study.

Lodgepole pine forests are not as warm as Front Range

ponderosa pine forests because of elevation and because of

higher canopy closure. In lodgepole pine forests treatments

should last longer than what we were able to complete. Because snow may impede accessibility to some sites in the

spring, it may be advisable to establish treatments in the fall

after beetle flight is complete but only after careful determination of the success of new attacks.

Solarization treatments should always be established in

areas that will facilitate the highest temperatures possible.

Forest openings, particularly with southern exposures, should

be favored. Finding openings in Front Range ponderosa pine

forests is not difficult but may be challenging in higher elevation lodgepole pine forests. Removing additional trees in

lodgepole pine forests may be necessary to increase solar radiation in the treatment area.

The information provided should help guide the use of solar treatments for reducing survival of mountain pine beetles

in infested ponderosa and lodgepole pine logs in Colorado.

Properly implemented solar treatments will reduce mountain

pine beetle survival in infested logs.

Acknowledgements

The authors would like to thank the following individuals.

Anna Greene, Keith A. Lingenfelter, Mitchell L. Ludwig,

Audrey A. Miles, Isabel A. Munck, and Brett J. Sanborn, Rocky

Mountain Research Station; Bernard Benton, Lee Pederson,

and Bill Schaupp, Forest Health Management, Region 2, for

their assistance in conducting the field work for the study.

Jennifer Langen, Colorado State Forest Service, for her assistance in locating field sites in the Sulphur Ranger District. Jill

Williams, Rocky Mountain Research Station, for conducting

the bootstrapping simulation analysis and Rudy King, Rocky

Mountain Research Station, for his assistance in statistical

analysis. Joyce VanDeWater, Rocky Mountain Research Station for preparing figure 1. Paul Langowski, Canyon Lakes

Ranger District, and Jan Burke, Sulphur Ranger District, for

their logistical support. This study was a cooperative effort

between the Rocky Mountain Research Station, the ArapahoRoosevelt National Forest, Forest Health Management, Region 2, and the Colorado State Forest Service.
USDA Forest Service Res. Pap. RMRS-RP-30. 2001 11

References

Buffam, P.E. and D.D. Lucht. 1968. Use of polyethylene sheeting

for control of Ips spp. in logging debris. J. Econ. Entomol. 61:

1465–1466.

Craighead, F.C. 1920. Direct sunlight as a factor in forest insect

control. Proc. Entomol. Soc. Wash. 22: 106–108.

Efron, B. and R.J. Tibshirani. 1993. An introduction to the bootstrap. Chapman & Hall, New York. 436 p.

Graham, S.A. 1924. Temperature as a limiting factor in the life of

subcortical insects. J. Econ. Entomol. 17: 377–83.

Holsten, E.H. and R.A. Werner. 1993. Effectiveness of polyethylene

sheeting in controlling spruce beetles (Coleoptera: Scolytidae)

in infested stacks of spruce firewood in Alaska. USDA Forest

Service, Pacific Northwest Research Station, Research Paper

PNW-RP-466. 6 p.

Massey, C.L. and N.D. Wygant. 1954. Biology and control of the

Engelmann spruce beetle in Colorado. USDA Circ. 944. 35 p.

McCambridge, W.F. 1964. Emergence period of Black Hills beetles

from ponderosa pine in the Central Rocky Mountains. USDA

Forest Service, Rocky Mountain Forest and Range Experiment

Station, Research Note RM-32. 4 p.

McCambridge, W.F., J. Laut, and R. Gosnell. 1975. Fumigate firewood infested with mountain pine beetle. USDA Forest Service,

Rocky Mountain Forest and Range Experiment Station, Research

Note RM-289. 2 p.

Mitchell, J.C. and J.M. Schmid. 1973. Spruce beetle: mortality from

solar heat in cull logs of Engelmann spruce. J. Econ. Entomol.

66: 401–403.

Patterson, J.E. 1930. Control of the mountain pine beetle in lodgepole

pine by the use of solar heat. USDA. Tech. Bulletin. 195. 20 p.

Schmid, J.M. 1972. Emergence, attack densities, and seasonal trends

of mountain pine beetle (Dendroctonus ponderosae) in the Black

Hills. USDA Forest Service, Rocky Mountain Forest and Range

Experiment Station, Research Note RM-211. 7 p.

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