United States 

Department of 

Agriculture

Forest Service 

Forest

Products

Laboratory

Research

Paper

FPL 472 

Durability of

PreservativeTreated

Wood Utility Poles

in Guam

Rodney C. DeGroot 

Thomas H. Lauret 
Abstract Caution

Pressure-treated wood utility poles in Guam were inspected 

to evaluate efficiency of preservative standards. Formosan 

termites (Coptotermes formosanus Shiraki) can destroy the 

untreated heartwood of Douglas-fir poles treated with 

creosote, pentachlorophenol, and chromated copper 

arsenate (CCA). Where Formosan termites are a hazard, a 

supplemental soil treatment for termite control should be 

used around Douglas-fir poles pressure treated with 

creosote or pentachlorophenol. Where Formosan termites 

are a serious hazard, the utilization of CCA-treated 

Douglas-fir utility poles should be questioned. Pressure 

treatments with ammoniacal copper arsenate (ACA) seem to 

be effective in protecting heartwood of treated Douglas-fir 

poles from attack by Formosan termites, but additional 

documentation is needed to determine the full potential of 

that treatment. Early attack by soft-rot fungi and by termites 

were detected on some pentachlorophenol-treated southern 

pine poles in Guam. 

Keywords: Poles, creosote, pentachlorophenol, CCA, ACA, 

preservative, termites, Formosan termites. 

May 1986 

DeGroot, Rodney Lauret, Thomas Durability of preservative-treated 

wood utility poles in Guam. Res. Pap. FPL 472. Madison, WI: 

U.S. Department of Agriculture, Forest Service, Forest Products Laboratory; 

1986. 16 p. 

A limited number of free copies of this publication are available to the public 

from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 

53705-2398. Laboratory publications are sent to over 1,000 libraries in the 

United States and elsewhere. 

This publication reports research involving pesticides. It does 

not contain recommendations for their use, nor does it imply 

that the uses discussed here have been registered. All uses 

of pesticides must be registered by appropriate State and/or 

Federal agencies before they can be recommended. 

CAUTION: Pesticides can be injurious to humans, domestic 

animals, desirable plants, and fish or other wildlife-if they 

are not handled or applied properly. Use all pesticides 

selectively and carefully. Follow recommended practices for 

the disposal of surplus pesticides and pesticide containers. 

The Laboratory is maintained in cooperation with the University of Wisconsin. 
Durability of 

Preservative-Treated

Wood Utility Poles 

in Guam 

Rodney C. DeGroot, Supervisory Research Plant Pathologist 

Forest Products Laboratory, Madison, WI 

Thomas H. Lauret, Manager, Applied Biology 

Department of Navy, Pacific Division 

Naval Facilities Engineering Command 

Pearl Harbor. HI 

Introduction

Installation of properly treated utility poles will result in lower 

replacement costs and lower maintenance costs. For these 

reasons, it is wise to periodically evaluate the durability of 

poles already in the field and use this information to assess 

the adequacy of wood preservative standards for different 

uses and environments. In this paper we report our 

observations and evaluations of preservative-treated utility 

poles in Guam. Their durability is particularly interesting 

because of severe Formosan termite (Coptotermes

formosanus Shiraki) activity there and because most of the 

poles purchased for use on Guam after the War of the 

Pacific were in compliance with Federal specifications (U.S. 

Federal Supply Service) for treated wood products. (They 

were procured through U.S. Navy supply channels.) The 

majority of wood poles on Guam are Douglas-fir 

(Pseudotsuga menziesii (Mirb.) Franco). Preservative 

penetration requirements reflect a relatively thin band of 

sapwood (American Wood-Preservers’ Association (AWPA) 

1983, Lassen and Okkonen 1969). The heartwood has been 

described as moderately durable (U.S. Department of 

Agriculture (USDA) 1974) or nondurable (Graham and 

Helsing 1979). 

Causes of Deterioration 

According to Graham (1973), large Douglas-fir poles 

normally are dried to meet treating requirements and not to 

moisture contents that they will attain in service. The 

heartwood moisture content of about 30 to 40 percent 

frequently remains unchanged until the treated pole is 

installed. In service, the interior of the pole at and above the 

groundline drops below the fiber saturation point, and 

seasoning checks may extend into the pole beyond the shell 

of treated wood. Fungi, termites, and carpenter ants enter 

the poles through the exposed untreated wood and may 

cause extensive internal deterioration within 10 years after 

installation. One might expect that this would be a problem 

of special consequence in tropical regions where termite 

activity is intense. The Formosan termite, for example, will 

readily feed upon Douglas-fir heartwood (Mannesmann 

1973).

Past Research 

Two previous studies described conditions in large-diameter 

Douglas-fir poles. Graham et al. (1976) surveyed 479 

Douglas-fir poles that were pressure treated with 

pentachlorophenol in heavy oil and were in service for 6 to 

18 years in western Oregon. They found internal decay in 

46 percent of the 60- to 80-foot-long poles. 

Zabel et al. (1980) detected decay in 190 of 952 

(approximately 20 pct) treated Douglas-fir poles installed for 

up to 10 years in the northeastern United States. 

Seventy-two percent (73/102) of chromated copper 

arsenate- (CCA) treated poles examined had decay. Fifteen 

percent (1061689) of poles pressure treated with 

pentachlorophenol in oil had decay. 

The question often arises whether small-diameter Douglas-fir 

poles might perform better than large-diameter poles. 

Assumably, small-diameter poles would be less likely to 

develop deep seasoning checks which penetrate the 

peripheral zone of treated wood. 
Figure 1.—Decay severity zones for wood utility poles as defined by the USDA Rural Electrification 

Association. Decay is least severe in zone 1, most severe in zone 5. (ML84 5657) 

Most of the available information about performance of 

small-diameter Douglas-fir poles comes from experiments 

and field experience in temperate climates. Approximately 

25 to 30 million poles are installed in rural electric systems 

that participate with the USDA Rural Electrification 

Administration (REA 1973) in periodic studies of pole 

performance. These studies reveal that within the contiguous 

United States 78 percent of all poles replaced by REA 

cooperatives were replaced because of decay, followed by 

woodpeckers (7.2 pct) and lightning (4.6 pct). For purposes 

of estimating decay hazards to poles, the REA divided the 

contiguous 48 states into 5 “decay” zones (fig. 1) which 

broadly group poles with like experiences. Zone 1 has the 

lowest hazard: Zone 5, the highest. 

Within the REA system, creosoted Douglas-fir has been 

primarily used in less severe decay zones. The record for 

creosoted Douglas-fir poles in Zone 2 has been very good 

(REA 1973). Records of pole inspections by the Osmose 

Company during 1974 and 1975 also indicate good 

performance of Douglas-fir distribution poles in zones of low 

to medium decay hazard (table 1). 

Pole-diameter, treated Douglas-fir posts (approximately 20 ft 

long, 7 to 9 in. in diameter) were exposed by the Bell 

System in a field plot near Orange Park, FL. That site had 

an annual rainfall of 54 inches and a sandy organic 

soil—Lakeland Sand (Ochrymowych and McOrmond 1978). 

2

Termite species native to Florida were present. After 

21 years of exposure, posts treated to 0.5 pound per cubic 

foot (lb/ft3

) of ammoniacal copper arsenate (ACA) had 

excellent performance. Only one of 21 ACA-treated 

Douglas-fir posts had slight surface decay. 

Forty-five Douglas-fir posts, treated with 

pentachlorophenol/liquified petroleum gas-isopropyl ether 

cosolvent, were exposed for 14 years at Orange Park. After 

14 years, slight surface deterioration caused by either decay 

or termite attack was present on all posts. Nine percent of 

the posts showed moderate attack. 

Table 1.óCondition of Douglas-fir distribution poles

examined during 1974 and 1975 in low to medium 

decay-hazard zones of contiguous United States1

Region of Number Poles rejected Poles with decay 

observation Preservative2 of poles but not rejected 

in sample Number Percent Number percent 

California

to Maine C 2,787 112 4.0 276 11.9

California

to New York P 7,334 269 3.7 290 3.9

1

Data provided by Mr. Robert E. Birtz Vice President, Utilities Division, Osmose, Buffalo, NY. Letter 

of May 18, 1984. Data is this report were randomly selected from actual pole inspection and treating 

program records. 

2

C = creosote; P = pentachlorophenol in oil. 
Methods

A report on durability of telephone poles on the island of 

Hawaii (Boone 1965) is one of the few reports available on 

performance of U.S.-produced wood poles that are installed 

in the Tropics. Boone concluded from his examinations of 

utility company records that, after 20 years in line, 

84 percent of the pressure-treated Douglas-fir poles were 

still serviceable, and 74 percent of the pressure-treated 

southern pine poles were serviceable in urban areas. He did 

not determine whether termites or wood decay were present 

in the serviceable poles. Treated poles were presumed to 

have been pressure treated with creosote to a retention of 

8 Ib/ft3

. Higher rainfall affected untreated species more than 

it did treated species. Neither rainfall nor differences in 

elevation appeared to have had any effect on the durability 

of treated poles. 

This Study 

Guam is the largest and southernmost island of the Mariana 

Islands. It lies about 13.5° N, 145° E, with the Philippine Sea 

on the west and the Pacific Ocean to the east. The climate 

of Guam is almost uniformly warm and humid. The mean 

annual temperature is 78.7 °F; the mean annual precipitation 

(rainfall) is 102.1 inches. The dry season extends from 

January through April. The rainy season lasts from mid-July 

to mid-November. About 15 percent of the annual rainfall 

occurs during the dry season and 55 percent during the 

rainy season. Typhoons move directly across Guam at a 

frequency of about 1 every 8 years (National Oceanic and 

Atmospheric Administration 1982). 

Soils in Guam vary considerably. In northern Guam, soils 

are generally neutral to slightly alkaline and have a coraline 

parent material. Most southern soils are typically acidic, 

being derived from volcanic materials.1

Until 1978, soil treatments with termiticides were used 

around new and old poles to control attack by subterranean 

termites. Unfortunately, no records were kept on year or 

location of those treatments. Consequently, poles set before 

1978 and still sound cannot be accepted as evidence for 

intrinsic durability because of the possibility that soil 

treatments could have been used around those poles. No 

other records on individual pole histories were available for 

any utility lines, with the exception of one with which Mr. 

Lauret has personal experience. In that line, located on U.S. 

Navy property, 2 percent chlordane was applied around 

poles as they were installed in 1969.2

 A segment of that line 

was examined in this study (table 8). For all other lines and 

poles discussed in this report, data for poles installed after 

1977 reflect performance without benefit of soil treatments to 

control subterranean termites. 

1

Joan Jordon, Soil Conservation Service, U.S. Department of Agriculture, 

University of Guam Station, Mangilao, Guam 96913. Personal communication 

dated 2/17/84. 

2

About 3 to 4 gal of 2 pct chlordane were sprayed into the cavity around the 

pole at the time of backfilling when the poles were set. Later this process was 

changed to rodding the material down alongside the pole after it was set. This 

permitted better coordination of the different crews that were needed to set 

poles and treat soil. The U.S. Environmental Protection Agency currently 

would require a special use permit for application of 2 pct chlordane around 

poles as described here. 

Poles on Guam were inspected in March 1984. Personnel 

from the U.S. Navy Public Works Center and from Guam 

Power Authority identified lines with different histories and 

participated in the field inspections. In addition, Dr. Robert 

Bielarski, U.S. Naval Facilities Engineering Command, 

Alexandria, VA, joined in the inspection of several line 

segments.

Our experimental approach was to document current 

conditions in individual line segments or in groups of poles 

of like species, size class, preservative treatment, or history. 

Where possible, attempts were made to examine 

consecutive poles in a line (tables 1-8). Such runs always 

began at an intersection, road, or some other distinctive 

geographical benchmark to avoid personal bias in selecting 

line segments. A number of creosote-treated Douglas-fir 

poles that were already removed from lines because of 

termite attack were also examined individually to determine 

depths of preservative penetration. Because most poles on 

Guam are in size Classes 1 through 33

, poles of smaller 

size classes (table 9) were examined wherever they were 

located. A few additional poles were examined individually 

as we were enroute to points of interest. 

All poles that we inspected were visually inspected for 

evidence of termite attack above ground and were sounded 

with a hammer. In more detailed inspections given to some 

poles, increment cores were extracted from the base of 

poles about 6 inches above the groundline. Depths of 

preservative penetration were measured directly on the 

cores using chrome Azurol for CCA and ACA and 

Penta-Check for pentachlorophenol (AWPA, Standard M2). 

Thickness of solid wood was determined from increment 

cores and with a shell thickness indicator. Some cores 

subsequently were chemically analyzed for the amount of 

preservative present within the appropriate assay zone 

(AWPA 1983). Cores from some of the older, 

creosote-treated poles without a legible brand were also 

checked for chlorine content to determine if they might have 

been treated with a creosote-pentachlorophenol mixture. The 

species of some poles could not be identified in the field, so 

species identification was made in the laboratory on the 

basis of anatomical characteristics of the increment cores. 

Species identification, based on wood anatomy, grouped the 

southern yellow pines, lodgepole, and ponderosa pines in 

one category: “yellow pines.” 

Some poles were also inspected below grade. Soil was 

removed from the base of the pole to a depth of 6 inches, 

and the exterior of the poles was examined for evidence of 

decay and termite attack. 

3

Class sizes of poles are described in REA Bulletin 44-2:345-1, Spec. No. 

DT-SC (Electric) PE-9 (Telecommunications), Jan. 1982, USDA, Washington, 

DC.
Six lines of poles were examined: 

A. A maintained line in a residential area, west central 

Guam. This line was presumably installed in the 1950’s 

(tables 2 and 3). 

B. Abandoned and replacement poles in a line located near 

an abandoned housing area along the northwestern side 

of Guam. This line was originally installed in 1959. 

Replacement poles were set in 1977 (tables 4 and 5). 

C. An old line of Douglas-fir poles. The installation date of 

this line is unknown, but Guam Power Authority 

personnel regard these poles as examples of their oldest 

poles in service (table 6). 

D. A line of poles in a rural area at the north end of Guam. 

This location never was urbanized. Installation date of 

line is unknown (table 7). 

E. A line of poles which received soil treatments with 

termiticides as poles were being set in the ground in 

1969 (table 8). Mr. Lauret personally observed the 

pesticide application around poles in the line segment 

included in this study. 

F. A line of southern pine poles that were installed after 

1979 in a residential area in central Guam (table 9). 

Table 2.—Condition of 31 consecutive Class 1 through 3

Douglas-fir poles in a line through residential area in west 

central Guam (Line A)1

Poles Poles not Brand dates that Preser- attacked attacked were observed vative2

by termites by termites on poles 3

------------Number------------

2 15 1957, 1957,

1959, 1970 

P 1 2 1969

ACA 0 3

CCA 3 5 1972, 1979, 1972, 

1970, 1976 

1

Poles were 35 to 45 ft long. Occasional poles of non-United States 

species were skipped. The proportion of original/replacement poles 

was not determined. 

2

ACA = ammoniacal copper arsenate; C = creosote; 

CCA = chromated copper arsenate; P = pentachlorophenol in oil. 

3

Dates were legible on only 10 poles. 

Table 3.—Condition of 10 Class 1 through 3 Douglas-fir 

poles in a line through residential area In west central 

Guam (Line A)1

Circum- Brand

Preservative Retention Termite Pole Depth of 

ference

tration assay4 attack5

hollow6 wood

In. Yr In. Lb/ft3 In.

42 ACA 1.4 S >5.0

1.9

53 C 2.8 10.5 (3) – S >5.0

1.4

48 1957 C 1.5 3.6 (2) + H 1.5

.8

40 1972 CCA .6 .6 (3) + ~

.8

1.2

37 C 2.0

1.2

8.5 (4) – S >4.0

1.3

date2

Type3 Pene- by solid/ sound

46 CCA 1.0 .3 (1) +

1.7

41 1962 P 1.8 .8 (3) – S >4.0

1.7

1.9

43 1967 P 2.6 .4 (3) + H 1.9-2.6

2.2

.8 .1 (2) 

47 1972 CCA .8 .6 (2) + H 1.9->4.0

1.0

1.0

52 C 2.0 12.0 (5) + H 2.0-2.1

2.0

2.1

2.1

2.0

1

These poles were specifically selected for detailed observation after the condition of the 

whole line (table 1) had been determined. Poles were 35 to 45 ft in length. 

2

Only dates that were legible are listed. Omissions indicate either that brand (or tag) was 

not seen or that the date was illegible. 

3

ACA = ammoniacal copper arsenate; C = creosote; CCA = chromated copper arsenate; 

P = pentachlorophenol in oil. 

4

The number of increment cores in the composite sample that was analyzed is shown in 

parentheses. Assay zone = 0.25 to 1.0 in. from surface. 

5

+ = visual evidence of termite attacks; – = no termite attack observed. 

6

S = solid; H = hollow: ~ = termite attack present, but pole not hollow yet. 

4

C

.5-.8
Table 4.—Condition of six consecutive Class 1 and 2

creosote-treated, Douglas-fir poles that were set out in 

1959 and abandoned in 1977 (Line B)1

Depth of Pole Pole Circum- Termite solid/ number 2 ference Preservative Sound attack3

hollow4

penetration wood

GPA 6 42 1.8 1.8 + H

GPA 7 43 1.6 1.6 + H

GPA 9 37 1.2 1.2 + H

GPA 12 + H

GPA 13 42 + H

GPA 16 39 1.5 >5.0 – S

1

These poles are still standing, but they are not being used. They 

were replaced in 1977 by poles shown in table 5. Poles were 30 to 

45 ft long. Omissions in table occur where no measurements were 

taken.

2

Number refers to entry in field record book, not to utility number for 

pole.

3

+ = visual evidence of termite attacks; – = no termite attack 

observed.

4

S = solid; H = hollow. 

Table 5.—Condition of 5 consecutive, pentachlorophenoltreated, Douglas-fir poles set in 1977 as replacements for 

poles shown in table 4 (Line B)1

Pole Size Depth of Preservative Termite

number2

 class3 Preservative Sound retention4 attack5

penetration wood 

Lb/ft3

GPA 8 2 1.9 >4.5 1.1 –

2.9 >4.5

GPA 10 1 1.8 >5.0 0.7

2.2 >5.0

GPA 11 2 2.1 >5.0 0.6 –

2.2 >5.0

GPA 14 2 2.5 >5.0 1.2 –

3.2 >5.0

GPA 15 2 2.7 >5.0 1.3 –

1

These poles replaced the 1959 poles described in table 4. These 

poles were often set close to an old pole that was attacked by 

termites. Poles were not inspected below ground. 

2

Number refers to entry in field record book, not to utility number for 

pole.

3

Poles were 45 ft long. 

4

Retentions reported are average of two increment cores taken 90° 

apart, 6 in. above groundline. Assay zone = 0.25 to 1.0 in. from 

surface. Assays were performed by the lime ignition method. 

5

+ = visual evidence of termite attacks; – = no termite attack 

observed.

Table 6.—Condition of 11 consecutive 45- to 55-foot, Douglas-fir poles in a line that 

was identified by Guam Power Authority personnel as one of the oldest on the island 

(Line C) 

Pole

number 1

Brand

date 2

Circumference Preservative3 Depth of 

Sound

penetration wood

Termite

attack4

Pole

solid/

hollow5

Yr In.

GPA 17 47 C 1.8 1.8 + H

GPA 18 1962 47 C 1.9 1.9 + H

GPA 19 48 C 1.8 1.8 + H

GPA 20 1967 48 C 1.1 >4.2 – S

GPA 21 1962 43 C 1.2 1.5 + H

GPA 22 46 C 1.8 >4.0 + S

GPA 23 50 C 1.6 1.6 + H

GPA 24 47 C 1.2 1.4 + H

GPA 25 1972 43 ACA .9 >4.0 – S

GPA 26 1957 48 C 1.5 >4.0 – S

GPA 27 1957 48 C 1.2 1.2 + H

1

Number refers to field record book, not to utility line number. 

2

No entries were made where information could not be read on the brand. 

3

ACA = ammoniacal copper arsenate; C = creosote. 

4

+ = visual evidence of termite attacks; – = no termite attack observed. 

5

S = solid; H = hollow. 

5
1

2

3

4

5

6

7

8

9

10

11

12

Table 7.—Condition of 11 consecutive, 30- to 45-foot, Douglas-fir poles in a rural line at 

the northern end of Guam (Line D)1

Pole Brand CircumPreservative Retention

Termite Pole

Pene- On By solid/ number2 date3 ference Type tration brand assay4 attack5

hollow6

Yr In. In.

– 1972 48 CCA 1.7 0.7 S

1971 46 CCA 1.1 .4 + H – 1966 C 8 S – 44 ACA 1.2 .6 S

CCA 2.2 .5 + H

1965 41 C 1.9 5.7 + H

51 P 1.7 .7 – S – 1965 40 C 1.6 13.0 S – 37 C 4.2 8 10.7 S

41 P 1.4 0.2 – S

( 7

) C 3.0 5.0 – S

– 43 C S

1

This area was never urbanized. Omissions in table occur where no measurements were taken. 

2

Numbers refer to poles examined, not the utility line number. 

3

0nly information that was legible on the brand is entered. Where information couldn’t be found or 

read on brand, no entry is made. 

4

Assay results are reported for a single core only. No assay was made on poles 3 and 12. Assays 

for pentachlorophenol were by the lime ignition method. 

5

+ = visual evidence of termite attacks; – = no termite attack observed 

6

S = solid; H = hollow. 

7

The eleventh pole in this series is not a Class 1 Douglas-fir pole. It was identified from wood 

anatomy as being “yellow pine.” 

6
Table 8.—Condition of 10 consecutive poles that received soil treatments with 2 percent 

chlordane for termite control as poles were being set in line in 1969 (Line E)1

Pole Brand Circum- Wood species Depth of Preservative Termite Pole

and solid/ number2 date ference preservative3

Length preservative retention by attack5

hollow6 assay4

Yr In. Ft In. Lb/ft3

– 14 1960 38 DF-C 40 1.5 3.6 S

1.6 – 15 1971 48 DF-P 55 2.5 .3 S

2.4 – 16 1965 43 WL-P 40 .8 .5 S

1.0 – 17 (7) 38 DF-C (

7

) 1.6 6.1 S

2.4 – 18 1965 42 WL-P 40 1.2 1.1 S

1.3 – 19 1962 40 DF-C 40 .6 1.8 S

.5 – 20 1961 38 DF-C 45 1.6 2.9 S

1.8 – 21 1969 46 DF-P 60 2.0 .1 S

1.6 – 22 1962 37 DF-C 40 1.0 9.1 S

1.6 – 23 1961 41 DF-C (

7 ) 2.1 6.3 S

2.3

1

Coauthor Mr. Lauret observed the soil treatment of poles in this line segment which is located along 

the edge of a wooded area. All poles were sound at this inspection. 

2

Pole numbers refer to numbers in field record book, not to utility pole number. Pole No. 15 is presumed 

to be a replacement pole. 

3

DF = Douglas-fir; WL = western larch; C = creosote; P = pentachlorophenol in oil. 

4

Assay of two cores taken 90° apart, 6 in. above grade. Assay zones were 0.25 to 1.0 in. from surface 

for DF; 0.1 to 0.6 in. from surface for WL. 

5

+ = visual evidence of termite attacks; – = no termite attack observed. 

6

S = solid; H = hollow. 

7

Omissions occur where information could not be read on brand. 

7
Table 9.—Condition of 10 consecutive, pentachlorophenol-treated, 40-foot southern 

pine poles in a line through a residential area in central Guam (Line F)1

Exterior of pole 0 to 

Pole Brand Circum- Preservative 6 inches below grade 

number2 date ference retention3

Termite wood soft 

attack4,5 or firm6

24

25

26

27

28

29

30

31

32

33

Yr In.

1979 47

1979 42

1979 43

1979 41

1979 42

1979 44

1979 42

1979 43

1979 44

1979 44

Lb/ft3

7

0.46 + S 7

.54 – S 7

.49 – S 7

.43 – F 7

.41 – S

.39 – S – .56 S – .66 S

7.20 + S

.41 Grazing, S

but no 

active

infestation

Information on pole species, height, and preservative treatment recorded from brand. 

2

Numbers refer to entries in field record book, not to utility number of poles in line. 

3

Increment cores, taken from poles in the field, were analyzed by the lime ignition method. 

Preservative penetration appeared to meet or exceed requirements of Federal Specification 

TT-W-571, but this was difficult to verify in the field with indicator solutions. 

4

Formosan termites (Coptotermes formosanus (Shiraki)).

5

+ = visual evidence of termite attack; – = no termite attack observed. 

6

Softened wood (either due to decay or soft rot) usually occurred from 2 to 6 in. below grade, but in 

pole No. 24 it extended to several inches above ground. Radial depth of softened wood was from 

1/8 to 1/4 in. S = soft; F = firm. 

7

Average of independent analysis on each of two cores (three cores for pole No. 24). Values 

reported for poles 21, 29, 30, 31, and 33 are for individual cores. Assay zone is 0.5 to 2.0 in. from 

surface.

8

1
Findings

The majority of poles installed more than 12 years ago were 

pressure treated with creosote. Poles treated with 

pentachlorophenol were used to a lesser extent. More 

recently, poles treated with the waterborne preservatives 

ACA or CCA have also been used. No estimate was made 

of the relative proportions of each type of preservative that 

exists within the total population of poles. 

Formosan termites have destroyed the central core of 

heartwood in many of the preservative-treated Douglas-fir 

utility poles present in lines on Guam (tables 3,4,6,7,10,11). 

This occurs in poles of small diameter (table 10) as well as 

in larger poles (tables 3,4,6,7,11). Nevertheless, some poles 

survive (tables 4,6), even in old lines with severe termite 

attack. We estimated that up to 20 percent of 

creosote-treated Douglas-fir poles in old lines are not 

attacked by termites. 

Soil Treatments 

Ninety percent of the Douglas-fir and western larch poles 

that received a soil treatment with 2 percent chlordane as 

the poles were set in line were sound after approximately 

14 years in service, even though some of the residual 

preservative retentions appear rather low (table 8). 

Creosote

Douglas-fir utility poles that are pressure treated with 

creosote, and which do not receive a supplemental soil 

treatment, are susceptible to attack by Formosan termites. 

Termites can destroy the internal, untreated heartwood 

throughout the length of the pole (figs. 2a,2b), but do not 

attack the peripheral ring of creosote-penetrated wood. 

Creosote in the peripheral ring of wood, which is penetrated 

during pressure treatment, adequately protects that wood 

from attack by decay fungi, termites, and other insects. 

Analytical results for creosote and pentachlorophenol 

content that are derived from a small number of cores/pole 

are not exact. Still, values for composites of three or more 

cores from the same pole indicate a substantial loading of 

creosote. A seven-core composite showed 9.1 Ib/ft3

 in the 

assay zone of another Douglas-fir pole that was attacked by 

termites (fig. 3). All poles are presumed to be treated with 

creosote and not with creo-penta mixtures. We saw no 

brand indications for creo-penta mixtures, and we did not 

detect any high chlorine contents in our chemical analyses. 

Table 10.—Condition of small, creosote-treated, Douglas-fir poles observed at different 

locations on Guam 

Depth of Termite Pole Pole Brand Circum- solid/ number1 date2 ference Class2 Length2

Preservative Sound attack3

hollow4

penetration wood

Yr In. Ft

GPA 3 34

GPA 4 35 40

1.5 1.5 + H

1.6 >4.0 – S

1.5 1.5 + H

1.8 >4.5 – GPA 5 31

GPA 41 34

GPA 44 1966 31

GPA 45 30

GPA 46 1964 29

GPA 47 1965 28

GPA 48 1953 29

GPA 49 1965 33

5 45

5

5

4 30

30

5 25

4 35

S

1.4 >4.5 + S – 1.5 >4.5 S

.9 .9 + H

1.9 >4.2 – S – 1.9 >4.5 S – 1.5 >4.5 S

1

Poles 3, 4, and 5 were in an abandoned housing area. They probably were installed in the 

mid-1950’s. Pole 41 was in a rural area. Poles 44 to 49 were in a city. All pole numbers refer to 

entries in record book: they are not actual utility numbers. 

2

0nly information that was legible on brand or tag is entered. 

3

+ = visual evidence of termite attack; – = no termite attack observed. 

4

S = solid; H = hollow. 

9
Table 11 .—Condition of Douglas-fir poles on Guam examined individually or in small 

groups

Depth of Termite Pole Pole Brand Circum- Presernumber 1 date ference vative Preservative Sound attack2 solid/

penetration wood hollow3

In.

GPA 28 1968 39

GPA 29 1968 40

GPA 30 1968 42

C

C

C

P

C

P

C

0.8-1.5

.8-1.5

a. 1.8

b. 1.8

c. 1.4

d. 1.8

e. 1.5

2.0

1.4

1.5-2.1

1.0-2.0

.8-1.5

1.8

1.9

1.6

2.0

1.6

>5.0

>5.0

>5.0

>5.0

>5.0

>5.0

>5.0

+ H

+ H

+ H

– S – S – S – S

+ S – S – S – S

– S – S

GPA 31 33

GPA 32 1968

GPA 33 1962 37

GPA 34 1958 41

GPA 35 1974 49

GPA 36 1976 48

GPA 37 1972 55

GPA 38 1972 49

GPA 39 47

GPA 40 1972 48

CCA 1.1

ACA 0.9

ACA 2.1

ACA 1.6

ACA

ACA

1

Pole numbers refer to numbers in record book, not to utility number of poles in line. Poles of 

unique interest: GPA 28, 29, and 30 are three Douglas-fir poles that were creosote-treated in 1968, 

set in service for at least 10 years in Guam, and removed from service in March 1984 because of 

attack from Formosan termites. 

GPA 31 and 32 are two sound Douglas-fir poles that were located in vicinity of 28-30. Note that 

poles GPA 30 and 32 have equivalent preservative penetrations. 

GPA 33–sound pole that was recently taken down. 

GPA 34–sound pole in front of shopping center. 

GPA 35–CCA pole along road at north end of island. We stopped for an inspection when we 

spotted pole. 

GPA 36 through 40–five consecutive ACA-treated Douglas-fir poles on west side of island near 

north end. No increment cores were taken from GPA 39 and 40. 

2

+ = visual evidence of termite attack; – = no termite attack observed. 

3

S = solid: H = hollow. 

The amount of solid wood remaining in termite-attacked, 

creosote-treated, Douglas-fir poles represented the depth of 

preservative penetration. The minimum depth of solid wood 

in all standing poles that were attacked by Formosan 

termites was always more than 1 inch. However, less than 

1 inch of creosote penetration was observed in one sound 

pole that was protected from subterranean termite attack by 

a supplemental soil treatment applied at time of pole 

installation (table 8). 

Some of the old, but sound, creosote-treated Douglas-fir 

poles had internal rings filled with preservative. Often, these 

rings were several inches from the peripheral band of 

treated wood (fig. 4). This pattern was not observed in all 

creosote-treated poles that were sound, but did occur with 

sufficient frequency to give an impression that deep 

penetration of creosote into checks, shakes, or other internal 

voids contributed to long-term durability of poles in line. 

10

The old line (table 6) of creosote-treated Douglas-fir was 

comprised of mostly hollow poles. This line was heavily 

supported with guy wires, which probably contributed to the 

line’s survival. 

Pentachlorophenol in Petroleum Oil 

Mixed results were observed on poles treated with 

pentachlorophenol in petroleum oil. Penta treatments on 

western pole species (tables 2,3,5,7,11) usually were 

extremely dark brown to almost black. These poles had 

been in line for 7 or more years. No decay was observed 

below grade on penta-treated western poles in lines A or E. 

Lines B and D were not examined below grade. With some 

of the penta-treated Douglas-fir poles, Formosan termites 

attack the heartwood in the same manner as they attack 

heartwood in creosote-treated poles. 
Figure 2a.—Cross section of creosote-treated 

Douglas-fir utility pole that was attacked by 

Formosan termites, C. formosanus. The central core 

of heartwood was destroyed and has been replaced 

by termite-produced “carton.” (M84 0175) 

Figure 2b.—Section of creosote-treated Douglas-fir 

pole that has been attacked by Formosan termites. 

Termites destroyed the heartwood throughout the 

length of the pole. (M84 0178) 

Figure 3.—Replacement poles are customarily

installed next to the base of old, termite-infested 

poles. The creosote retention in the assay zone of 

the termite-attacked pole being removed was 

9.1 lb/ft3

 This was determined from a composite of 

seven increment cores. (M84 0180) 

11
Figure 4.—Increment borings from sound, creosote-treated Douglas-fir poles. Isolated loadings of 

creosote deep within the pole are evident. This pattern was often seen in sound poles. (M84 0113) 

Nine of 10 penta-treated southern pine poles (line F, table 9) 

that were examined had external soft rot (fig. 5) below 

grade. Two of the ten poles were also being attacked by 

Formosan termites. In contrast to creosote-treated 

Douglas-fir poles, termite attack was on the exterior of the 

pentachlorophenol-treated southern pine poles (fig. 6). On 

southern pine poles, termite attack appeared to follow attack 

by soft-rot fungi. These poles were treated in 1977. Thus 

they are rather new poles. Chemical analyses indicate that 

the retention level of pentachlorophenol in those poles 

probably met standards (table 9). 

Chromated Copper Arsenate 

Twelve CCA-treated Douglas-fir poles were examined in 

utility lines. Six of these were attacked by Formosan termites 

(Tables 2,7,11). Channels that had been excavated by 

Formosan termites were observed in treated sapwood of 

Douglas-fir poles (fig. 7). In some CCA-treated Douglas-fir 

poles that had Formosan termites in the heartwood, the 

residual amount of sound wood at the perimeter of the pole 

was occasionally as little as 0.5 inch. Whether this reflected 

poor preservative penetration or destruction of treated wood 

by the colony of termites in the heartwood could not be 

determined.

Ammoniacal Copper Arsenate 

Ten ACA-treated Douglas-fir poles were examined in line. 

None of these was attacked by Formosan termites (tables 

2,6,7,11). Five of these ACA-treated poles (table 11) were 

part of a longer series of ACA poles on the northeast side of 

the island. 

12
Figure 6.—Termite attack observed below grade on 

a pentachlorophenol-treated southern pine poles. 

(M84 0382) 

Figure 7.—Formosan termite channels (arrow) on 

exterior of CCA-treated sapwood of Douglas-fir 

poles. (M84 0176) 

Figure 5.—Scanning electron micrographs of 

transverse sections of wood collected below grade 

from exterior of southern pine poles treated with 

pentachlorophenol in petroleum solvent. 

(A) Boundary between soft-rotted wood and 

unattacked wood within latewood of an annual ring, 

(B) Latewood showing uniformity of attack, where it 

occurs, and (C) Soft-rot cavities within S2 layers of 

fiber cell walls. (M85 0107) 

13
Discussion

About 20 percent of the poles, even in old lines, are not 

attacked by Formosan termites. Several factors could 

contribute to this; namely, repeated application of soil 

treatments around certain poles; extraordinarily deep 

penetration of preservative into internal voids within the 

poles as was noted with some creosote treatments (fig. 4); 

or feeding patterns of Formosan termites. 

Dr. Minoru Tamashiro4

 believes that Formosan termites do 

not randomly search for food as is thought to be true for 

Reticulitermes spp. in the Southeastern United States. 

Instead, the Formosan termites have a more directed 

feeding pattern, which would explain why they might miss 

some items in a linear array (e.g., utility poles). 

Replacement poles, however, are usually installed close to 

cutoff stubs of old termite-destroyed poles. Unless a soil 

treatment is used, an active termite colony in the old pole 

stubs probably would soon find the new pole. To maximize 

the life of replacement poles, the soil around the poles 

should be treated with an approved termiticide as the poles 

are set in line. 

Creosote

We assume that the minimum depth of preservative 

penetration allowed in specifications (0.75 in.) was in effect 

when these poles were treated. The ring of sound wood in 

surviving, but termite-attacked, Douglas-fir poles consistently 

was more than 1 inch thick. Many of the termite-attacked 

Class 1 through 3 poles were supported in part by guys and 

adjacent poles in line. Even for poles with supplemental 

support, there seems justification in questioning whether a

minimum of 3/4-inch penetration is adequate for creosote 

treatments of Class 1-3 poles. 

Pentachlorophenol

Variations in the petroleum oils used with the different 

pentachlorophenol treatments may be one factor contributing 

to differences in performance of pentachlorophenol-treated 

poles (c.f. Baechler and Roth 1962, Duncan and Richards 

1950, Gjovik and Gutzmer 1983 (table 17)). 

Another factor to consider is the time between treatment and 

ultimate installation. Often, this is more than 1 year. That is 

not desirable for optimum performance of poles treated with 

oilborne preservatives, but long shipping and storage times 

are a reality for islands in the western Pacific. 

4

Dr. Minoru Tamashiro, Dep. of Entomology, Univ. of Hawaii, Honolulu, HI. 

Personal communication, March 1984. On file with Dr. DeGroot. 

Chromated Copper Arsenate 

With regards to termite attack of treated poles, a significant 

difference between CCA and creosote treatments is that 

creosote protects the peripheral zone of 

preservative-penetrated wood from attack by termites. CCA 

does not. Consequently, the zone of treated wood in 

CCA-treated poles cannot be regarded as a potential source 

of residual strength, once attack by Formosan termites 

begins.

We observed that creosote-treated sapwood of Douglas-fir 

poles was more resistant to attack by Formosan termites 

than that of the CCA-treated poles. We presume that this is 

because vapors of creosote treatments have some 

repellency effect, which the CCA treatment lacks. CCA is 

fixed within the treated sapwood, is odor-free, and leach 

resistant. As such, it has no repellency effect for termites, 

which can quickly pass through the shell of CCA-treated 

sapwood.

Utility personnel within the U.S. Navy Public Works Center 

have the impression that CCA-treated Douglas-fir poles on 

Guam are attacked more quickly than are poles treated with 

other preservatives. Would soil treatments with termiticides 

be as effective in protecting CCA-treated Douglas-fir as they 

are in protecting creosote- and pentachlorophenol-treated 

poles of that species? They probably would be; but in many 

residential settings, shrubbery or other materials contact 

aboveground portions of poles and provide a bridge over soil 

treatments. Where such bridges occurred, the lack of any 

repellency seemingly would allow ready colonization of the 

poles.

The potential for decay within interiors of CCA-treated 

Douglas-fir poles (Zabel, Lombard, and Kenderes 1980) 

would not be altered by soil treatments. That decay in 

CCA-treated Douglas-fir poles can be a serious problem in 

New York implies that potentials for wood decay should also 

be of concern in the Tropics. Therefore, we question 

whether current standards for CCA-treatment of Douglas-fir 

poles adequately address potentials for attack by both 

termites and decay fungi in the Tropics. 

We make no extrapolation from observations of CCA-treated 

Douglas-fir poles to CCA-treated poles of other species. 

Whether Formosan termites will penetrate CCA-treated 

sapwood of thick sapwood species with a lesser volume of 

untreated heartwood as readily as they penetrate 

CCA-treated sapwood of Douglas-fir could not be 

determined in this inspection. We were unable to determine 

whether the termites went directly through the shell of 

treated wood from the outside of the pole or whether they 

only attacked the treated wood after a colony was well 

established within the pole. 

14
Conclusions

Ammoniacal Copper Arsenate 

ACA-treated poles are regarded by utility personnel in the 

U.S. Navy Public Works Center as being the most durable 

treated wood pole on Guam. Because of the lack of records 

on soil treatments around poles in line, we were unable to 

verify this impression. We observed an occasional 

ACA-treated pole, not in a utility line, that had termite attack. 

Nevertheless, we share the impression that ACA poles have 

relatively good durability where Formosan termites are 

present, but we cannot present a definitive argument to this 

point. Additional documentation is needed in areas where 

soil treatments were never used to better appreciate the 

durability of ACA-treated Douglas-fir poles. 

Class 1 through 5 Douglas-fir utility poles that are pressure 

treated with creosote are susceptible to attack by Formosan 

termites. These termites can destroy the untreated 

heartwood on the inside of the pole but do not destroy the 

peripheral ring of treated wood. The level of creosote that 

was required by specifications for the assay zone provides 

adequate protection against termites and decay fungi for that 

peripheral ring that is penetrated by the preservative. 

Additional protection is needed for the interior heartwood. 

Additional protection for creosote- and 

pentachlorophenol-treated Douglas-fir can be achieved by 

treating the ground around the pole with a termiticide when 

poles are set in line. Current specifications for pressure 

treatment of Douglas-fir poles with creosote and with 

pentachlorophenol, for use where Formosan or comparable 

species of termites are a hazard, should be supplemented 

with an additional requirement for soil treatment with an 

approved termiticide. 

Current Federal specifications for treatment of Douglas-fir 

poles with CCA should be reviewed with regard to use in 

areas where Formosan termites are a serious hazard. 

Additional documentation of the field performance of 

ACA-treated Douglas-fir poles is needed to determine 

whether this treatment more effectively protects the 

heartwood of Douglas-fir poles from attack by Formosan 

termites than do other preservatives. 

Additional investigation is also needed to determine the 

cause of variation in durability of pentachlorophenol-treated 

poles. The early appearance of soft rot and termites in 

southern pine poles, seemingly with adequate retentions of 

pentachlorophenol, is of particular concern for poles 

exposed in environments such as that in Guam. 

15
Literature Cited 

American Wood-Preservers’ Association. Standard C4. 

Poles-preservative treatment by pressure processes. In: 

AWPA Book of Standards. Stevensville, MD: American 

Wood-Preservers’ Association; 1983. 6 p. 

Baechler, R. H.; Roth, H. G. Effect of petroleum carrier on 

rate of loss of pentachlorophenol from treated stakes. 

Forest Products Journal. 4: 187-190; 1962. 

Boone, R. S. Service life of telephone poles on the island 

of Hawaii. Berkeley, CA: U.S. Department of Agriculture, 

Forest Service, Pacific Southwest Forest and Range 

Experiment Station; 1965. 6 p. 

Duncan, C. C.; Richards, C. A. Evaluating wood 

preservatives by soil-block tests: 1. Effect of the carrier 

on pentachlorophenol solutions. 2. Comparison of a 

coal-tar creosote, a petroleum containing penta 

chlorophenol or copper naphthenate and mixtures of 

them. American Wood-Preservers’ Association 

Proceedings. 46: 131-145; 1950. 

Gjovik, L. R.; Gutzmer, D. I. Comparison of wood 

preservatives in stake tests. Res. Note FPL-02. Madison, 

WI: U.S. Department of Agriculture, Forest Service, 

Forest Products Laboratory; 1983. 79 p. 

Graham, R. D. Preventing and stopping internal decay of 

Douglas-fir poles. Holzforschung. 27(5): 168-178; 1973. 

Graham, R. D.; Helsing, G. G. Wood pole maintenance 

manual: Inspection and supplemental treatment of 

Douglas-fir and western redcedar poles. Res. Bull. 24. 

Corvallis, OR: Oregon State University: February 1979. 

62 p. 

Graham, R. D.; Scheffer, T. C.; Helsing, G.; Lew, J. D. 

Fumigants can stop internal decay of Douglas-fir poles for 

at least 5 years. Forest Products Journal. 26(7): 38-41; 

1976.

Lassen, L. E.; Okkonen, E. A. Sapwood thickness of 

Douglas-fir and five other western softwoods. Res. Pap. 

FPL 124. Madison, WI: U.S. Department of Agriculture, 

Forest Service, Forest Products Laboratory; October 

1969. 16 p. 

Mannesmann, R. Comparison of twenty-one commercial 

wood species from North America in relation to feeding 

rates of the Formosan termite, Coptotermes formosanus 

Shiraki. Material und Organismen. 8(2):107-120; 1973. 

National Oceanic and Atmospheric Administration. 

Local climatological data. Annual summary with 

comparative data. Guam, Pacific. Asheville, NC: NOAA, 

National Environmental Satellite Data and Information 

Service, National Climatic Data Center; 1982. 4 p. 

Ochrymowych, J.; McOrmond, R. R. Performance of 

pole-diameter posts treated with various preservatives 

during a quarter century of testing at Orange Park, FL 

test plot. Orange Park, FL: American Wood-Preservers’ 

Association Proceedings. 1978: 190-213. 

Rural Electrification Administration. Pole performance 

study. Staff Report. Washington, DC: U.S. Department of 

Agriculture, REA; Feb. 1973. 43 p. 

U.S. Department of Agriculture. Wood handbook: Wood 

as an engineering material. Agric. Handb. 72. Madison, 

WI: U.S. Department of Agriculture, Forest Service, 

Forest Products Laboratory; 1974. rev. 

U.S. Federal Supply Service, General Services 

Administration. Interim Federal Specification. Wood 

preservation: Treating practices. TT-W-00571 

(AGR-AFS). Updated at irregular intervals. 

Zabel, R. A., Lombard, F. F.; Kenderes, A. M. Fungi

associated with decay in treated Douglas-fir transmission 

poles in the Northeastern United States. Forest Products 

Journal. 30(4): 51-56; 1980. 

16
Acknowledgments

The authors gratefully acknowledge the assistance of Donna 

Christensen, Daniel Foster, and Thomas Kuster, U.S. 

Department of Agriculture, Forest Service, Forest Products 

Laboratory, Madison, WI, for wood species identification of 

increment cores, for analysis of wood preservatives, and for 

scanning election microscopic examination of wood samples. 

The assistance of utility specialists from U.S. Navy Public 

Works Center and from Guam Power Authority also 

contributed to the success of this study. This investigation 

was partially funded by the U.S. Agency for International 

Development.

2.5-4/86

17