United States

Department of

Agriculture

Forest Service

Southeastern Forest

Experiment Station

Research Note

SE-355

April 1990

Field Tests of Pine Oil

as a Repellent for

Southern Pine Bark Beetles

J.C. Nod, F.L. Hastings, and A.S. Jones

ABSTRACT

An experimental mixture of terpene hydrocarbons derived from

wood pulping, BBR-2, sprayed on the lower 6 m of widely separated

southern pine trees did not protect nearby trees from southern

pine beetle attacks. Whether treated trees were protected from

southern pine beetle was inconclusive. The pine oil mixture did

not repel lps from treated trees or nearby untreated trees. Black

turpentine beetles were attracted either by pine oil or by the resinosis

and injury of the host caused by the pine oil. The pine oil was

phytotoxic to treated trees, causing resinosis, mottling of the inner

phloem and outer xylem tissue, and mortality. This is the first report

of phytotoxicity to conifers.

Keywords: Dendroctonus frontalis, D. terebrans, Ips grandicollis,

Pinus taeda, P. echinata, P. virginiana, BBR-2, phytotoxicity.

Nijholt (1980), Nijholt and McMullen (1980), and

Nijholt and others (1981) reported that Norpine-

(Northwest Petrochemical Corp., Anacortes, WA), a

mixture of terpenes, terpene alcohols, and other

minor constituents’ derived as a byproduct of sulphate

wood pulping of firs, hemlock, and pine, was active

as a repellent of ambrosia beetles and three species

of Dendroctonus bark beetles when sprayed undiluted

on logs and living trees in British Columbia. Norpineand an experimental mixture of terpene hydrocarbons

selected for repellency to various species of bark

beetles, BBR-2 (Safer Agro-Chem Ltd., Victoria, British

Columbia, Canada), repelled mountain pine beetles,

D. ponderosae Hopkins, (Richmond 1985, 1986;

The authors are, respectively, Research Entomologist, USDA Forest

Service, Southeastern Forest Experiment Station, Forestry Sciences

Laboratory, Athens, GA, and Research Entomologist and Research

Microbiologist, USDA Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Research Triangle

Park, NC.

‘Nijholt (1980) gives the gaschromatographic analysis of Norpine-65.

McMullen and Safranyik 1985) and spruce beetle, D.

rufipennis (Kirby), (Werner and others 1986). Repelling

of southern pine beetles (SPB), D. frontalis Zimmermann, was observed in a study by O’Donnell and

others (1986) with Norpine- and in a study by

Berisford and others (1986) with BBR-2. In the

Berisford and others (1986) study, BBR-2 did not

repel Ips graandicollis (Eichhoff) or black turpentine

beetle (BTB), D. ferebrans (Olivier).

In this Note we report attempts to determine whether

BBR-2 repels SPB from treated trees located in the

path of an advancing SPB spot head and from

untreated adjacent trees. Results are inconclusive

because spot expansion failed to occur in most cases,

but potentially valuable observations are made on

SPB, BTB, and Ips activity, and there was a strong

indication that BBR-2 is phytotoxic to three southern

pine species. Those results are reported here. A

general description of the methods used is given;

further details may be obtained from the authors.

Methods

Location and Stand Characteristics

Trees in the path of eight active SPB spots in the

Piedmont of South Carolina were treated with pine

oil in 1983. Table 1 gives locations and stand

characteristics for each of these SPB spots. Spot

selection criteria were: (1) 20 or more newly attacked

green trees with apparently healthy SPB brood, (2) a

minimum pine basal area of 18.4 m*/ha, and (3) a

spot head width and stand depth of 20 meters or

more in the path of spot expansion.
Table 1 -Southern pine beetle spots in South Carolina where BBR-2 was sprayed onto pine boles for repellency, 1983

Test trees

County

and

study area

Treatment Number

date treated

Number

controls SPP.’

Average

height

Average

d.b.h.

Stand

basal

area

spot

expansionb

Oconee Oconee Point

Reedy Fork

Route 488

m cm mzlha

July 20 2 2 SL c c c _ _ __ __

21 8 8 L 20.9 19.8 56.4 +

26 4 0 SL, V 21.5 21.1 32.8

Cherokee Route 50

l-85

Aug. 23 2 2 c c c c _ _ __ _ _ _.

24 2 2 SL __ e 19.3 31.7

Spartanburg

Chesnee

Glenn Springs

Clifton

Sept. 14 5 0 SL, v 13.5 26.1 30.7

20 10 0 SL, L 13.5 18.4 28.2

22 4 0 SL 23.3 21.9 34.0

L SL = shortleaf pine; L = loblolly pine; V = Virginia pine.

SPB spot salvaged before data taken.

i + = spot expanded; - = spot did not expand.

One SL.

’ Data not recorded.

Treatment

The trunks of test trees were sprayed to runoff with

undiluted Safer BBR-22 from a height of 6 m (height

marked with a band of marking tape) to the ground

with a compressed-air garden sprayer. The trees

were treated the same day the spot head was marked

or early the next morning. Test trees were not baited

with pheromone to induce attack.

Experimental Layout

The active head of each spot was carefully delineated

by flagging newly infested trees after examining the

trunks at ground level and up to 8 m for evidence of

attack (pitch tubes, red and/or white boring dust

expelled from entrance holes, or the presence of

clerid adults running over the bark in search of bark

beetle prey) using 8.5-m extension ladders. Trees

were examined in this manner within 7 m of the

apparent head to make sure the extent of spot

expansion was known. Then pairs of trees receiving

randomly assigned treatments (sprayed and un2BBR-2 is generally described as a mixture of terpene hydrocarbons

which varies somewhat from batch to batch because it is a byproduct

of the wood pulping process. The repellent ingredient(s) is unknown.

For more detailed information about composition, one should

contact Safer Agro-Chem Ltd., Victoria, British Columbia.

sprayed) were located 5 and 15 m beyond the head.

Trees in each pair were separated from each other

by a distance of 10 m (fig. 1). Of course, because

these SPB spots were located in natural stands, the

10-m spacing between test trees was approximate

and minimum. Trees were sometimes slightly more

than 10 m apart. Test trees were dominants and

codominants and apparently healthy.

Active head (7/21/m) ;

---- Inactive head (7/21/@3)

.*****..*.**** Expanded head (9/8/W)

l Treated tree I

0 Untreated tree

t-w Direction of spread

Figure 1 -Southern pine beetle spot with active heads at lefl and

right, layout of test trees, and 5-m-radius circular plots. (BBR-2 test

at Reedy Fork study area in South Carolina, 1983.)

2
Evaluation

When the head moved past the treated trees (4-6

weeks after treatment), the treated and control trees

were examined to midboie and classified as “attacked”

or ‘unattacked” by SPB and/or Ips. All trees within a

5-m radius of the test trees were recorded as to

bearing and distance from each test tree, and each

was classed by the above procedures as ‘attacked”

or “unattacked.” Additional information was recorded

for these trees: tree species, crown class, diameter

at breast height (d.b.h.); i.e., 1.4 m above ground.

Bark was peeled off trees to determine species of

attacking beetles and their success. No bark was

disturbed until the spot had moved past the treated

trees or had died out, so no new attractive source

was created before the end of the test.

Since SPB spot expansion occurred only in one area

(Reedy Fork) and since it was limited on that area,

statistical analyses were not done. If spots had

expanded as anticipated, the study design would

have permitted statistical comparisons between

treatments in terms of incidence of attack on treated

versus control trees using a contingency table (Steel

and Torrie 1960). The analysis of the area effect of

the repellent on trees adjacent to treated trees would

have utilized a paired t-test if the number of trees

within the 5-m radius was ~15 and the percentage

of attack was spread over a range; otherwise, a sign

test would have been utilized (Snedecor and Cochran

1967). Pairs in which both test trees are unattacked,

as well as all trees within a 5-m radius of both test

trees, were not to be used in the analyses. Since the

analysis had to be abandoned, the reported results

are anecdotal.

Results and Discussion

SPB Responses

Repellency from treated trees. Only one sector (A)

of the SPB spot head at Reedy Fork expanded into

the area near the two treated test trees (fig.1). In

that sector, both control trees (A-l and A-3) were

mass attacked and killed by SPB and Ips within 4

weeks of plot installation. Both BBR-2-treated trees

were attacked by Ips but not by SPB. One treated

tree, A-4, was unsuccessfully attacked by Ips above

the spray zone and it lived; the other, A-2, was attacked

moderately by 1. grandicollis and it died. Neither

sprayed tree was attacked by SPB but both trees

were on the edge of the spot expansion, as indicated

by several unattacked trees within 5 m mostly in the

northerly and westerly directions (fig. 1). Hence, the

treated trees may have escaped attacks by chance,

and we cannot say that the pine oil protected them

from SPB attack.

Berisford and others (1986) baited treated loblolly

pine (Pinus taeda L.) bolts with SPB attractant

(Frontalure) to promote attack and found a reduction

in beetle visits and no attacks on treated bolts for 2

months after treatment with BBR-2. They therefore

concluded that BBR-2 was repellent to SPB. In another

study in which treated loblolly and shortleaf (P.

echinata Mill.) pines were baited with Frontalure,

O’Donnell and others (1986) observed a reduction in

beetle visits and attacks for only 1 week, and attacks

increased thereafter. All treated trees eventually died

from beetle attack, nine from SPB mass attack 2

weeks after treatment and six from SPB and Ips

sometime later. So the repellent action did not last

very long. It is possible that mass attacks would not

have occurred if Frontalure had not been applied to

bait the trees.

Frontalure was used in the above tests to make sure

beetles came to treated trees, but it may produce an

unfair test of a repellent. Nijholt (unpublished information obtained through telephone conversation with

W.W. Nijholt, Safer Agro-Chem Ltd., Victoria, British

Columbia) believes that on unbaited trees pine oil

repels individual beetles or small numbers of pioneer

beetles landing on the tree. Therefore, secondary

attractants are never produced on the tree and mass

attack does not occur. If secondary attractants are

abundant on the tree, as when a treated tree is baited,

the repellency may be overwhelmed and mass attack

may occur. This is the reason we did not apply

Frontalure to pine oil-treated trees in the path of SPB

spot expansion.

Area effect. Most of the trees surrounding the two

control trees in front of the spot expansion at Reedy

Fork were attacked and killed by a mixed population

of SPB and Ips. In fact, four trees within 5 m of one

control tree were all that were unattacked, and these

were the only survivors. More trees survived around

the treated trees (36-38 percent), but the head seemed

to expand up to the treated trees and stop (fig. 1).

However, 12 trees within 5 m of BBR-Ztreated trees

were successfully attacked by SPB or SPB and Ips.

Of those, two were within 2 to 3 m, and three were

less than 2 m from the treated trees. Thus, even if

there was a repellent effect of BBR-2 on a treated

tree, there was little area effect, if any, on SPB attacking

the adjacent trees.

Berisford (unpublished information obtained through

telephone conversation with C.W. Berisford, Department of Entomology, University of Georgia, Athens,

GA) found no evidence that BBR-2 had an area effect

on SPB. Check bolts within 2 m of treated bolts were

attacked, and all trees in which treated bolts were

hung were attacked by SPB. O’Donnell and others

3
(1986) found SPB attacks in apparently untreated

bark crevices on sprayed trees, suggesting that

there was no area effect. Nijholt and others (1981)

concluded that pine oil (Norpine-65) had at least a

lo-m-radius area effect on Douglas-fir beetle, D.

pseudorsugae Hopkins, mountain pine beetle, and

spruce beetle. However, McMullen and Safranyik

(1985) were unable to demonstrate an area effect for

BBR-2 and Norpine- for mountain pine beetle in

lodgepole pine, P. contorta Dougl. ex Loud.

fps spp. Responses

Repellency from treated trees. In the Route 488

plot, two BBR-2-treated codominant Virginia pines

(P. virginiana Mill.) (15.2 and 16.5 cm d.b.h.) in front

of portions of the head containing an active Ips

population were mass attacked by 1. grandicollis.

They died some time between the third and sixth

week after treatment. Another sprayed Virginia pine

located in front of the SPB head at Route 488 was

also mass attacked by 1. grandicollis, and it died.

Several BBRZ-treated loblolly pines at Reedy Fork

were moderately attacked by 1. grandicollis and 1.

avulsus (Eichhoff). These treated trees were probably

weakened by the BBR-2 prior to the mass attacks. In

any case, 5 to 6 weeks after treatment, BBR-2 did

not repel Ips from dying and perhaps weakened

trees. Berisford and others (1986) found that BBR-2

did not prevent 1. grandicollis attack on pine cut

immediately after treatment. They observed Ips mass

attacks 5 days after treatment.

Area effect. Two Virginia pines at Route 488 adjacent

to a BBR-2-treated tree were attacked by 1. grandicollis

and 1. avulsus. They were 2.0 and 2.6 m from the

treated tree. If BBR-2 has a repellent effect on Ips,

that effect does not extend from treated trees to

adjacent trees.

BTB Responses

In the Reedy Fork area, where a large population of

BTB occurred in SPB trees, all but one of the

BBR-2-treated trees had been attacked by two to six

BTB. Five of the six treated trees in front of sectors

B, C, and D of the SPB head, which did not expand,

were attacked by BTB (fig. 1). None of the control

trees were attacked, and only 2 of the 162 trees

within a 5-m radius of treated and control trees in

sectors B, C, and D were attacked by BTB; both

were near one control tree (D-i).

In the Route 488 plot treated on July 26, three of the

four sprayed trees (two shortleaf and two Virginia

pines) near the SPB head were attacked by BTB.

One of them had nine attacks and the other two had

two BTB attacks each. No BTB attacks occurred on

the two trees sprayed at Oconee Point. Only 2 of 21

trees sprayed with BBR-2 after mid-August were

attacked by BTB. In BBR-2-sprayed trees, success

rate of the BTB attacks (as defined by the presence

of live parent adults boring egg galleries and/or the

presence of brood) was 47 percent at Reedy Fork

and 67 percent at Route 488.

The high incidence of BTB attacks on BBR-2-treated

trees 3 to 4 weeks after treatment in July together

with a virtual absence of attacks on surrounding

trees indicate that the pine oil might have attracted

BTB. Another plausible possibility is that the phytotoxicity of the BBR-2 may have been responsible for the

trees attracting BTB. Weakening of the trees and/or

presence of copious quantities of resin under and

on the bark may have attracted BTB just as paraquattreated trees attract BTB (Nord and others 1985;

Stubbs and others 1984). In any case, BBR-2 does

not seem to repel BTB from injured trees and it does

not appear to adversely affect success of those

attacks.

Berisford and others (1986) found no evidence that

BBR-2 was repellent to BTB, in fact the opposite

may have been true.

Phytotoxicity of BBR-2

The first symptom of phytotoxicity that we noticed

was resinosis-resin running down the trunks of

trees that had been sprayed with BBR-2 in July. It

was first noticed on August 17 at the Reedy Fork

plot on loblolly pines, 4 weeks after treatment, and

at the Route 488 plot on Virginia pines 3 weeks after

treatment. The resin was usually clear and uncrystallized, but occasionally it was opaque, yellow, and

crystallized. It emanated from one to several points

on the trunk in the spray zone and ran down the

trunk on the outer bark scales for several meters. A

check of surrounding trees showed that resinosis

occurred only on sprayed trees.

When the trees at Reedy Fork and Route 488 were

checked again about 3 weeks later on September

7-8, we noticed boring dust coming from some of

the sprayed trees. In checking for the identity of the

insect involved, we discovered that some of the trees

had been attacked by Ips and were already dead,

as evidenced by the brown color of the inner phloem

and outer xylem. After seeing this, we checked some

sprayed trees that had no sign of beetle attack and

found them to be alive but with brown mottling stains

in the otherwise light-colored outer xylem and/or the

4
inner phloem. We refrained from cutting the bark l Resin had accumulated under the bark in pockets,

until this time, fearing that we would attract beetles and it was under such great pressure that resin hit

to the test trees. Since the tests were essentially the observer in the face when one of the pitch pockets

over, however, we decided to check every test tree was punctured. These pitch pockets were assumed

for phytotoxicity. to be the origin of the resin flow on the trunk.

Table 2 shows a summary of those observations

made on September 7-8, 1983. Resinosis and mottling

of the outer xylem and/or inner phloem was almost

universal among sprayed trees; these symptoms did

not occur in unsprayed trees, Mortality did not occur

at Oconee Point where two shortleaf pines were

treated. At Reedy Fork, however, mortality was 71

percent among the seven loblolly pines treated (the

lone treated shottleaf pine survived). Except for the

SPB-killed trees near the control trees in sector A,

none of the 162 trees within 5 m of the other test

trees had died as of December 7, 1983. At Route

488, three out of four of the BBR-Zsprayed Virginia

pines died by September 7, but the two treated

shortleaf pines survived. In checking these test trees

at Reedy Fork and Route 488 by shaving bark with a

machete, the following characteristics were noted:

l The origin of resin flow could not be readily

associated with anatomical features on the trunk

except in one shortleaf pine, on which it seemed to

be coming from around adventitious buds. Flow was

found only in the sprayed zone, which had been

marked with a flagging band at 6 m.

l Mottling of the inner phloem and outer xylem

seemed to be common throughout most of the

sprayed zone. Sometimes it was absent at breast

height but present at 5 to 6 m and vice versa. Mottling

was absent above the spray zone.

l Ips attack on the loblolly pines that died at Reedy

Fork did not look heavy enough to girdle the trees at

least up to 6 to 7 m. Three treated Virginia pines at

Route 488 were mass-attacked however. In some

dying trees at Reedy Fork, cerambycid infestations

were heavy.

Table 2-Phytotoxic symptoms and black turpentine beetle attack on three species of pine sprayed to

6 m with pine oil in late July 1983

BTB attack

Area

and

species

Treated

trees

Dead

trees

Trees

with

resinosis

Live trees

showing

mottling

Trees

attacked

Success

rate

_ _ _ _ Number - - - - __________--_---- Percent _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Oconee Point

Shortleaf 2 0 __ 100 0 __

Reedy Fork

Shortleaf

Loblolly

1 0 _- 100 0 __

7 5 71.4 100 85.7 39

Route 488

Shortleaf

Virginia

2 0 _ _ 100 100 50

4 3 100 100 25 100
Table 3-Phytotoxlc symptoms on three species of plnes sprayed to 6 m with pine oil from late August to late September 1963

Species

and

treatment date

Total Dead

trees trees

spots of

Subcortical mottling at - -

oozing pitch

between O-6 m Breast height ’ 5-6 m

0 1 2-5 >5 Phb XY b Phb Xyb

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Percentoftrees_____________________

Shortleaf

Aug. 24Sept. 22 16 0 50 12 25 12 81 25 87 19

Virginia

Sept. 14 3 0 0 0 0 100 100 67 100 67

Loblolly

Sept. 20 2 0 50 0 50 0 100 50 100 50

z 1.4 m above ground.

Ph = phloem; Xy = xylem.

Table 3 summarizes phytotoxicity data on trees treated

after August 23. Similar symptoms were noted except

that none of the trees had died as of December 6,

1983. Resinosis or oozing of pitch occurred only in

the sprayed zone of trees treated with BBR-2.

Incidence of resinosis was 50 percent in shortleaf

(n = 16) and loblolly (n = 2) pines and 100 percent

in Virginia pine (n = 3). Pitch oozed from more places

on the trunks of Virginia pines than it did on shortleaf

or loblolly pine. Incidence of mottling of the inner

phloem in the spray zone was higher than that of

the outer xylem in all species of pine. Shortleaf pine

had less mottling of the outer xylem than did Virginia

and loblolly pines. Mottling of both phloem and xylem

tissues were equally common at breast height and

at 5 to 6 m in all species. Mottling did not occur

above the spray zone in any tree.

BBR-2 appears to have a phytotoxic effect on all

three species of pine tested. Judging from the

incidence of tree mortality and mottling of inner phloem

and outer xylem, and the amount of resinosis, shortleaf

pine seems to be less affected than loblolly or Virginia

pine. Even when and where the phytotoxic reaction

was most severe, none of the five treated shortleaf

pines died, whereas 71 percent of the loblolly and

75 percent of the Virginia pine died. None of the

pines treated from late August to late September

died. However, most of the trees treated after

mid-August were shortleaf pine, which seemed less

sensitive earlier in the season.

Phytotoxicity of pine oil to treated trees was not

repotted in other studies. Berisford and others (1986)

treated loblolly pine in one test with undiluted BBR-2

to a height of 4 m, but the treatment was applied in

mid-September (information obtained through telephone conversation with C.W. Berisford, Department

of Entomology, University of Georgia, Athens, GA),

so it may not be fatal at this time of year. In another

test by Berisford and others (1986) slash pines (P.

elliottii Engelm. var. e//iotrj/) were sprayed with

undiluted BBR-2 to 0.9 m above ground in mid-July.

One day later they and control trees were partially

girdled (l/3 circumference) and a 4-percent paraquat

solution was applied to the wounds to stimulate

attack by BTB. No phytotoxicity from BBR-2 to the

treated pines was reported in that study, but it would

be hard to distinguish phytotoxicity caused by BBR-2

from that normally caused by paraquat.

O’Donnell and others (1986) treated 15 loblolly and

shortleaf pines with undiluted pine oil (Norpine-65) to

a height of 10 m in May. All treated trees were attacked

by bark beetles and succumbed within 35 days of

treatment, so there was no chance to observe the

phytotoxicity of the chemical at a macroscopic level.

Werner and others (1986) sprayed white spruce

(Picea glauca (Moench) Voss) to a height of 3 m

with undiluted BBR-2 and Norpine-65. A moderate

number of treated trees survived for 13 months, and

no phytotoxicity was evident.

6
Nijholt and others (1981) sprayed Norpine- to

runoff on the lower 2.5 m of lodgepole pine, white

spruce X Engelmann spruce hybrids (P. glauca x P.

engelmannii Parry ex Engelm.) and Douglas-fir,

Pseudofsuga menziesii (Mirb.) France. They reported

no phytotoxic symptoms on sprayed trees. Also,

Nijholt and McMullen (1980) reported no phytotoxicity

on lodgepole pine in a preliminary study. McMullen

and Safranyik (1985) sprayed mature lodgepole pine

in British Columbia to a height of 3.5 m with both

Norpine- and BBR-2. They did not mention phytotoxicity. Richmond (1985) sprayed lodgepole pines in

Colorado to a height of 5 m with Norpine- and

BBR-2 but did not report any phytotoxicity.

In our study, BBR-2 was very phytotoxic to all broadleaf

vegetation covered by the spray in the understory

and on the ground. Leaves yellowed and desiccated

overnight. Berisford and others (1986) also reported

phytotoxicity of BBR-2 to nontarget plants. Because

of this phytotoxicity to understory vegetation, it is

doubtful that the BBR-2 would be useful in urban

settings unless some sort of controlled-release

dispenser or controlled-spray applicator could be

developed.

Future Research on Pine Oil

Future research with pine oil should address the

phytotoxicity of BBR-2 to southern pines and other

vegetation. Diluted material and/or treatment of less

of the bole could be tested. Effects of weather,

environmental conditions, season of treatment, and

tree growth and vigor on toxicity should be measured.

Less adverse weather and better soil/water relations

might have been important factors in the greater

survival of the September-treated trees in our study.

It would be helpful if the repellent component of the

pine oil could be isolated so that it could be applied

in a nonphytotoxic carrier or in a dispenser of some

kind. Identification of the repellent component would

also solve the quality-control problem associated

with variations among batches of pine oil. Shea (1989)

has reported results of field tests of different distillation

tower refinements of Norpine-65P as repellents for

mountain pine beetle on lodgepole pine.

Acknowledgments

We wish to acknowledge the help of Dr. Roy L. Hedden,

Clemson University; Michael C. Remion, South

Carolina Commission of Forestry; and Tom Coffey

from the University of Georgia, in locating SPB spots.

For permission to use their land for studies, we thank

Buck A. Bearden, Gary Blanton, David Fort, H.P.

Hines, Dorsey Jones, C.V. Stribling, Jr., Lloyd Trent,

Dean Wall, Clemson University, and Oconee County

Hospital. We also thank Ricky Couch, Gordon Moore,

and Gretchen Waldbauer for their help with the field

work.

The use of trade, firm, or corporation names in this publication is

for the information and convenience of the reader. Such use does

not constitute an official endorsement or approval by the U.S.

Department of Agriculture of any product or service to the exclusion

of others that may be suitable.
Literature Cited

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of Entomological Science 21:316-318.

McMullen, L.H.; Safranyik, L 1985. Some effects of pine oil on

mountain pine beetle (Coleoptera:Scolytidae) at different

population levels. Journal of Entomological Society of British

Columbia 8229-30.

Nijholt, W.W. 1980. Pine oil and oleic acid delay and reduce attacks

on logs by ambrosia beetles (Coleoptera:Scolytidae). Canadian

Entomologist 112:199-204.

Nijholt, W.W.; L.H. McMullen. 1980. Pine oil prevents mountain

pine beetle attack on living lodgepole pine trees. Bi-Monthly

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O’Donnell, B.P.; Payne, T.L.; Walsh, K.D. 1986. Effect of pine oil

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21:319-321.

Richmond, Charles E. 1985. Effectiveness of two pine oils for

protecting lodgepole pine from attack by mountain pine beetle

(Coleoptera: Scolytidae). Canadian Entomologist 117:1445-1446.

Richmond, Charles E. 1986. Effectiveness of Norpine- for

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