Effects on eastern larch beetle of its natural attractant and synthetic pheromones in Alaska

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lta CORE 1 IST

vies, §—" E-FFaqts on Eastern Larch’Beetle c's

Agriculture

roestsovice §=©6- OF: ItS Natural Attractant and

Pacific Northwest

roemarene §OYNthetic Pheromones

Experiment Station

Research Note Nn A | a S k a

PNW-371
February 1981

Richard A.!Werner,! Malcolm M.{(Furniss,~

Larry C. Yarger,3 and Thomas Ward
| fe
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BAO , pit
Abstract Traps baited with Seudenol + ’a-pinene caught 87 percent more

eastern larch beetles, Dendroctonus simplex LeConte , than did
tamarack logs infested with females. Male beetles responded to
the synthetic attractant in greater numbers than females. Male
beetles were not attracted to frontalin, a principal attractant
of the closely related Douglas-fir beetle, Dendroctonus
pseudotsugae Hopkins. Attraction was reduced by 92 and 86 Pees
cent by addition of methylcylohexenone (MCH) and frontalin but ‘
by only 36 percent when trans-verbenol was added. This evidence
partially supports the taxonomic separation of the two
Dendroctonus Spence

a a

Keywords: Attractants (chemical) (-forest pest control, eastern

s ae larch beetle, [Dendroctonus simplex]
in ve =

= = linstitute of Northern Forestry, Pacific Northwest Forest and
Sa or Range Experiment Station, USDA Forest Service, .Fairbanks,
ee Alaska 99701.

= 5 -2Forestry Sciences Laboratory, Intermountain Forest and Range

“Experiment Station, USDA Forest Service, Moscow, Idaho 83843.

us -¢3Forest Insect and Disease Management, State and Private
) Forestry, USDA Forest Service, Juneau, Alaska 99801. Present
address: Forest Insect and Disease Management, USDA Forest
Service, Morgantown, West Virginia 18337.

4Institute of Northern Forestry, Pacific Northwest Forest and
Range Experiment Station, USDA Forest Service, Fairbanks, Alaska
99701. Present address: Dep. of Biological Science, Simon
Fraser University, Burnaby, B.C., Canada V5A 156.

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Pesticide
Statement

Introduction

This publication reports research involving pesticides. It
does not contain recommendations for their use, nor does it
imply that the uses discussed 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 eastern larch beetle, Dendroctonus simplex LeConte, is a pri-
mary pest of tamarack, Larix laricina (DuRoi) K. Koch, in western
Canada and Alaska. Beetles normally attack tamarack stands that
have been weakened, in some instances by defoliation during
outbreaks of the larch sawfly, Pristiphora erichsonii (Hartig),
or larch budmoth, Zeiraphera improbana (Walker). ‘The beetles
readily attack green, healthy tamarack when the parent population
increases above the carrying capacity of the initially attacked
trees. Infested trees seldom survive.

The presence of unmated females in a recently attacked tree
intensifies the attractiveness of the host tree to male beetles.
Although no aggregative pheromones have been isolated from

D. simplex females, experiments have shawn that males are
attracted to female-infested bolts and to Seudenol (3-methy1-2-
cyclohexen-l-ol) (Baker et al. 1977). Seudenol (Vite' et al.
1972), frontalin (Kinzer et al. 1971), and trans-~werbenol
(Rudinsky et al. 1972) have been identified as aggregative
pheromones of the Douglas-fir beetle, D. pseudotsugae Hopkins.
In addition, methylcyclohexenone (MCH) was identified as an anti-
aggregative pheromone in D. pseudotsugae (Kinzer et al. 1971).

D. simplex and D. A are taxonomically similar (Wood

‘1963, Furniss 1976) and could produce similar aggregative and

anti-aggregative pheromones. A field test was conducted to assess
the effect of frontalin, MCH, and trans-verbenol on the natural

attractant of D. simple “

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Methods

A field test was conducted for 6 days in June 1978 in an
80-yr-old open tamarack stand on the Bonanza Creek Experimental
Forest 42 km west of Fairbanks, Alaska. Tree height varied from
1.8 to 9.0 mwith d.b.h. between 2.5 and 15.0 cm. Temperatures
ranged from 2° to 27°C during the test.

Cylindrical sticky traps ‘similar to those described by Kline

et al. (1974) were baited with the test materials. The traps
were set on iron posts 1.5 m above the ground at 30-m intervals.
The traps measured 45 cm in length, 25 cm in diameter, and were
constructed of 6.35-mm mesh wire screen. Two replications of 23
traps each were used in a randomized complete block design.
Twenty-three treatments were assigned to the traps each day for
6 days in a randomized manner. Days were treated as subsamples,
and the 6-day data were pooled for each treatment per replicate.
In addition, the test site of each replication was moved a
distance of at least 60 m to a new location in order to eliminate
the effects of spillover of beetles from the attractant-baited
traps into adjacent live tamarack trees, thus creating an addi-
tional attractive source.

Treatments consisted of tamarack logs infested with females and
the synthetic pheromones: Seudenol, frontalin, trans-verbenol,
and MCH, alone and in combination with each other as shown in
table 1. Controls consisted of an empty trap and an uninfested
log section. The sources of natural attractant were tamarack
log sections, ca. 9 cm in length and 9-cm in diameter,
artificially infested by unmated female beetles. Freshly cut
tamarack logs were infested in the laboratory 1 day before
testing.

Part of the experiment utilized tamarack logs infested with
unmated D. pseudotsugae females transported to Alaska from Idaho.
The attractants produced by D. pseudotsugae were tested to deter-
mine if D. simplex responded to a taxonomically similar species.
These beetles were stored for 1 week at 5°C and then placed

at 22°C for 2 days before infesting the logs. D. simplex

female beetles were treated similarly. One female beetle was
placed in each of five preformed entrance holes in each log;
i.e., five female beetles per log, the holes were covered with
metal screen, and the log enclosed in a metal screen cage to
exclude wild male beetles because mating would terminate the
production of attractants by the females in the infested logs.

The synthetic pheromones were 1 ml each of Seudenol, frontalin,
trans-verbenol and MCH in open 1/2-dram glass vials placed
within perforated aluminum cans attached to the traps. Alpha
pinene in l-ml quantities was used as a synergist to Seudenol.

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Table 1--Number of Dendroctonus simplex adults trapped in
response to natural and synthetic pheromones

O58 percent slat 4 ite es ee ee

Mean catch/day Daily range
Treatments
2 b r 9

SESE ee ee een
Seudenol + a-pinene 12.0 dl/ 30.1 b A? 1 1e 3-35 3-93
Seudenol + a-pinene + TV2/ BS de 20.oucus2laz spe l=L7 4-62
5 D. simplex log 5.2 de 2 Ose Tweuae _ l-Ls 0-8
Seudenol + a-pinene + F3/ 3.4 e 226.6. 0.0 de OU-7 O=5
a-pinene Sa2e 2sae 5.8 de 0-4 0-6
5 D. pseudotsugae log 2.8 e Lae 4.3 e O=15 O=12
Seudenol + a-pinene + MCH4/ 2.4 e Lote 3.5 e 0-16 0-4
5 D. simplex log + TV 2.0 e RE 3.3 e 0-11 0-4
Untreated log ) Ce erm Lo 2.6 e 0-13 O7
Seudenol + a-pinene + :

TV, + JE oe Lo2e 2.5°e 0—5 U-5
Seudenol + a-pinene +

MCH + TV L ae 0.9 e 24 e 0-6 0-6
Seudenol + a-pinene +

MCH + TV + F POE 20.4 e 1.4 e 0-3 0-4
5 D. simplex log +

MCH + TV 0.8 e Q.5e 1.3 e O17 0-4
Seudenol + a-pinene +

MCB. +E O29 e 0.6 e yh Bare 0=5 0-35
5 D. simplex log + MCH 0.6 e O.44e 8.0 ce 0-1 Oo2
5 D. simplex log + F 0.2 e 0.3 e 0.5.e 0-6 0-3
TV + a-pinene 0.2 e D.2 2 0.4 e 0-2 ae
Untreated trap 0.2 e O52 Sg Us e O=1 0-2
F + a-pinene 0. ie a O.2 e 0-1 0-1
MCH O.le 0.1 e O2~e 0-1 0-1
TV + MCH 0,1 ¢ O0.le U.2 e 0-1 0-1
F + MCH O.le 0.0 e O.le (8 felt 0
Bt Mon, + TV \.0.¢ O.le O.le 0 0-1
a TY 0.0 2 0.0 e 0.0 e 0 0

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1/vyalues followed by the same letter within each test are not
significantly different at the 5-percent level (Duncan's New
Multiple Range Test).

2/tTv = trans-verbenol

3/P = frontalin

4/mcH = methlycyclohexenone

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Results and
Discussion

The commercial preparations of synthetic pheromones were purified
by preparatory gas-liquid chromatography (Birch et al. 1977) to
>99.8 percent using 4-percent Carbowax 20 M on Chromsorb G

(60/80 mesh) in a 6-m X 6.3-mm glass column.

The catches of D. simplex: adults by treatment are shown in

table 1. Response by D. simplex shows that some treatments were
attractive but others repressed attraction. Seudenol + a-pinene
caught 505 beetles or 40 percent of the total catch (1,273
beetles). The next best catch was Seudenol + a-pinene + trans-
verbenol with 327 beetles or 26 percent of the total catch. logs
with D. simplex females caught only 7 percent of the beetles.

The untreated log, a-pinene alone, and in combination with
either frontalin or trans-verbenol were not attractive to either
male or female beetles. Renwick (1970) has hypothesized that
trans-verbenol enhances the attraction of those-Dendroctonus
species that are attracted to pinene because it is similar \
chemically. The Pere that both a-pinene and trans-verbenol were
not attractive to D. simplex supports this hypothesis.

The logs containing D. simplex females caught 39 percent more
beetles than logs with D. pseudotsugae females. The reason for
the difference in attractiveness betwéen taxonomically similar
Dendroctonus species could be the production of frontalin by D.
pseudotsugae females which in our study actually repressed
attraction. Possibly D. simplex uses a different combination of

pheromones than D. pseudotsugae.

The addition.of trans-~erbenol, frontalin, and MCH either sepa-
rately or in combinations to Seudenol + a-pinene significantly
repressed attraction by D. simplex adults. The addition of MCH
to Seudenol +'a-pinene depressed response of D. simplex by

92 percent whereas the addition of frontalin alone and trans-
verbenol alone depressed response by 86 and 36 percent respec-
tively. D. simplex response was further depressed (97 percent )
when MCH, trans-verbenol and frontalin were all combined with
Seudenol + a-pinene. Reduced catches were also reported for D.
pseudotsugae when MCH and trans-verbenol were added to fronta-
lin (Rudinsky et al. 1972).

The frontalin +a-pinene and frontalin + untreated log were the
only treatments which caught (eight specimens) the bark beetle
predator, Thanasimus dubius (L.). Orthotomicus caelatus Eichoff
and Pityopthorus opaculus LeConte were the only other scolytids
caught. Most O. caelatus were caught on the 2 D. simplex-baited
traps while most P. st P. opaculus was caught on the 2 D. pseudotsugae
log (ID), the untreated control log, and the frontalin + untreated
log.

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Sonclusions Combinations of synthetic attractants caught more D. simplex
beetles than the beetle's natural attractant. Seudenol +
a-pinene caught significantly more beetles than female-infested
tamarack logs. The addition of MCH and frontalin to Seudenol +
a-pinene significantly repressed attraction. The addition of
trans-verbenol to Seudenol + 4-pinene repressed attraction to a
much lesser amount than MCH and frontalin.

The results of this field study add support to the taxonomic dif-
ferences that tend to separate D. simplex and D. pseudotsugae.

D. simplex was not attracted to frontalin, which is a principal
component of the aggregation system of D. pseudotsugae.

The pheromone components used in the aggregation system of D.
simplex should be isolated and identified in order to further
study the feasibility of using MCH or frontalin for controlling
small isolated infestations of D. simplex.

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Literature Cited

Baker, B. H., B. B. Hostetler, and M. M. Furniss.
1977. Response of eastern larch beetle (Coleoptera: Scolytidae)
in Alaska to its natural attractant and to Douglas-fir beetle
pheromones. Can. Ent. 109:289-294.

Bireh, Ma Gas Fe En Tilden, D. L. Wood, L. Es. Browne, J. C. Young,

and R. M. Silverstein.
1977. Biological activity of compounds isolated from air con-
densates and frass of the bark beetle, Ips confusus. J. Insect
Physiol. 2321373-1376.

Furniss, M. M.
1976. Controlled breeding, comparative anatomy, and bionomics
of Dendroctonus simplex LeConte and Dendroctonus pseudotsugae
Hopkins (Coleoptera: Scolytidae). In W. F. Barr (Ed.),
University of Idaho Dept. Ent. Anniv. Publ., p. 109-120.

Kinzer, GC. W., A. EF. Fentiman, Irs, R. L. Foltz, and

J. A. Rudinsky.
1971. Bark beetle attractants: 3-methyl-2-cyclohexen-1l-one
isolated from Dendroctonus pseudotsugae. J. Econ. Ent.
64:970-971. .

Kline, L. N., R. F. Schmitz, J. A. Rudinsky, and M. M. Furniss.
1974. Repression of spruce beetle (Coleoptera) attraction by
methylcyclohexenone in Idaho. Can. Ent. 106:485-491.

Renwick, J. A. A.
1970. Chemical aspects of bark beetle aggregation. Contrib.
Boyce Thompson Inst. Pl. Res. 24:337-341.

Rudinsky, J. A., G. W. Kinzer, A. W. Fentiman Jr., and

Ky. Ls Foltz. -
1972. Trans-verbenol isolated from Douglas-fir beetle:
laboratory and field bioassays in Oregon. Environ. Ent.
1:485-488.

Vite. G. P., G. By Pitman, A. F. Fentiman, Jr.,

and G. W. Kinzer.
1972. 3-methyl-2-cyclohexen-l-al isolated from Dendroctonus.
Naturwissenscahften 10:469-470.

Wood, S. I.
1963. A revision of the bark beetle genus Dendroctonus
Erichson (Coleoptera: Scolytidae). Gt. Basin Nat. 23. 117 p.

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The Forest Service of the U.S. Department of
Agriculture is dedicated to the principle of multiple
use management of the Nation’s forest resources
for sustained yields of wood, water, forage, wildlife,
and recreation. Through forestry research,
cooperation with the States and private forest
owners, and management of the National Forests
and National Grasslands; it strives — as directed by
Congress — to provide increasingly greater service
to a growing Nation.

The U.S. Department of Agriculture is an Equal
Opportunity Employer. Applicants for all Department
programs will be given equal consideration without
regard to age, race, color, sex, religion, or national
origin.

GPO 992-554

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