Note: Descriptions are shown in the official language in which they were submitted.
SPECIFICATION
This invention relates to a composition for
combating the mountain pine beetle, Dendroctonus ~onderosae
Hopkins, which does serious harm in the forest by killing
pine trees.
One way of controlling the mountain pine beetle is
to harvest the infested trees. The beetles which are
resident in the inner bark are killed during the
manufacturing process. however, it is often not feasible to
harvest the trees in time to control the beetles before they
di6perse to new trees. Pesticides have limited use in
controlling the beetle. Fîrstly, individual tree trunks,
rather than the whole forest must be sprayed at great cost.
Secondly, it is difficult to obtain a good effect since the
beetles live hidden under the bark most of the time.
One promising potential method for use in
integrated control of bark beetles is to use semiochemicals
(message-bearing chemicals) against them. In attacking a new
tree, bark beetles characteristically use two types of
semiochemicals to signal the acceptability of the host. One
type of semiochemical is an aggregation pheromone which is
produced by the beetles to induce other beetles of the same
species to aggregate on that host tree. The other type is a
tree-produced volatile that acts synergistically with one or
more aggregation pheromones to intensify the chemical
message. If the natural semiochemicals are known, they can
be synthesized and used to attract populations of bark
beetles. Thus they may be used in traps to monitor or
suppress a beetle population. They can also be used to
attract beetles to designated trap-trees which may be
harvested or treated with insecticides.
It is known that the pheromone, trans-verbenol
-- ~2~L~
(trans-4,6,6~trimethylbicyclo[3.1.1]hept-3-en-2-oll) is a
female-produced aggregation pheromone of the mountain
pine beetle. The host tree volatile, pinene (2,6,6-
trimethylbicyclo[3.1.1]hept-2-ene) is reported to act
synergistically with trans-verbenol. Inconsistent results
have been obtained with other monoterpenes and beetle-
produced compounds, including a male-produced
compound, exo-brevicomin (exo-7-ethyl-5-methyl-6,8-
dioxabicyclo[3.2.1]octane).
We have been unable to attract significant numbers
of mountain pine beetles to traps baited with trans-verbenol
and alpha-pinene. We assumed that this failure was caused by
the omizsion from the test bait of semiochemicals which the
beetle uses in nature. These difficulties therefore have
prevented se~iochemicals from being used a8 a tool to combat
mountain pine beetles.
We have discovered that in combination with the
host tree monoterpene, myrcene (7-methyl-3-methylene-lJ6-
octadiene) trans-verbenol synergistically attracts mainly
male mountain pine beetles to baited traps. When the male-
produced compound exo-brevicomin is added to the trans-
verbenol and myrcene bait, the attraction to female beetles
is increased so that approximately equal numbers of male and
female beetles are attracted. This same mixture of
semiochemicals i8 highly effective in inducing attack by
natural populations of mountain pine beetles on baited
lodgepole pine trees.
Thus, this invention provides a synergistic
composition, composed of myrcene and trans-verbenol in a
combined amount which i8 an effective bait for mountain pine
beetles.
In a second aspect, this invention provides for a
synergistic composition, composed of myrcene, trans-verbenol
~Z~ 4~
and further comprising exo-brevicomin in a combined amount
which is an effective bait for mountain pine beetles.
In a third aspect, this invention provides a
method o attracting mountain pine beetles by exposing them
to a synergistic composition composed of myrcene, trans-
verbenol and exo-brevicomin in a combined amount which
comprises an effective attractant for the beetles.
In a fourth aspect this invention provides a method
of attracting mountain pine beetles to traps for the purpose
of monitoring or suppressing beetle populations. The method
entails exposing the beetles to traps baited with a
synergistic composition composed o myrcene, trans-verbenol,
and exo-brevicomin in an amount which is effective in
causing the beetles to be captured in or on the traps.
In a fifth aspect this invention provides a
method of attracting mountain pine beetles to living pine
trees and inducing the beetles to mass attack (infest) the
tree. The method entails exposing the beetles to trees
baited with a synergistic composition composed of myrcene,
trans-verbenol, and exo-brevicomin in an amount which is
efective in causing the beetles to mass attack the baited
trees and nearby trees.
In a sixth aspect, this invention provides a
method of concentrating mountain pine beetle inestations in
selected areas of a forest. This method entails exposing the
beetles to a synergistic composition composed of myrcene,
trans-verbenol and exo-brevicomin in a combined amount which
is effective in concentrating the beetles.
In a seventh aspect, this invention provides a
method of moving the locus of mountain pine beetle
infestations within a forest. This method entailæ exposing
the beetles to a synergistic composition composed of myrcene,
trans-verbenol and exo-brevicomin in a combined amount which
~2~
is effective in moving the beetle3.
In an eighth aspect, this invention provides a
method of containing mountain p;ne beetle infestations within
previously attacked areas of a forestO This method entails
exposing the beetles to a synergistic composition comprised
of myrcene, trans-verbenol and exo-brevicomin in a combined
amount which is effective in containing the beetles.
A selection of host volatiles and insect-
produced compounds were screened for attractiveness to
mountain pine beetles using a simple laboratory
bioassay. Compounds found to be attractive were
trans-verbenol ~trans-4J6,6-trimethylbicyclo[3.1.1]-nept-3-en-
2-ol), 3-carene-10-ol (4-hydroxymethyl-7,7-dimethyl-3-
bicyclo[4.1.0]heptene), acetophenone (phenylmethyl ketone),
2-p-menthen-7-ol (4-isopropyl-2-cyclohexenyl methanol), exo-
brevicomin (exo-7-ethyl-5-methyl-6,8-
dioxabicyclol3.2.1]octane), myrcenol ((E)-2-methyl-6-
methylene-octa-2,7-dienol), ipsdienol (2-methyl-6-methylene-
20 2,7-octadien-4-ol), 3~carene (3,7,7-trimethylbicyclo[0.1.4]-
3-heptene), alpha-pinene (2,6,6-trimethylbicyclo[3.1.1]hept-
2-ene), beta-pinene (7,7-dimethyl-2(10)-
bicyclo[3.1.1]heptene), beta-phellandrene (3-isopropyl-6-
methylene-cyclohexene), terpinolene ((~-mentha-2,4(8)-diene),
and myrcene (7-methyl-3-methylene-1,6-octadiene).
Two experiments were conducted in the month of
August in mixed lodgepole pine and ponderosa pine forests
near Princeton, British Columbia.
In the first, seven-replicate experiment, trans-
verbenol was tested with each of six monoterpenes as a bait
in Lindgren funnel traps. A mixture composed of trans-
verbenol and myrcene was very attractive to mountain pine
beetles, but was more attractive to male than female beetles
(Table 1).
~Z~
Table 1. Ranked responses of De~dro~tonu~ ~ondero~ae to funnel
traps baited with various monoterpenes and the
aggregation pheromone trans-verbenol, near Princeton,
British Columbia, August 7-15. ~=7 replicates.
Number of Beetles Captured
Stimulus* Males Females Total
==========_==========================_=============================
No Bait (controlj
beta-Pinene + trans-Verbenol8 3 11
~p~-Pinene + trans-Verbenol21 6 27
3-Carene trans-Verbenol 35 11 46
beta-Phellandrene trans-Verbenol 47 11 58
Terpinolene + trans-Verbenol 87 31 118
Myrcene trans-Verbenol 263 47 310
*Release rates determined at room temperature as follows:
monoterpenes, 14 mg/24 h; trans-verbenol, 0.4 mg/24 h.
~2~
The second, six-replicate experiment tested three
baits in which myrcene was combined with trans-verbenol J exo-
brevicomin or both. As in the first experiment, myrcene
combined with trans-verbenol was highly attractive to male
mountain pine beetles and less so to females (Table 2).
however 9 the addit iOII of exo-brevicomin to the other two
volatiles raised the catch of femzles to a level comparable
to the catch of males.
Thus a three-part, semiochemical mixture consisting
of a host-tree compound, myrcene, 8 female-produced
aggregation pheromone, trans-verbenol, and a male-
produced aggregation pheromone, exo-brevicomin is required
to reproduce the attractive response by both sexes of
mountain pine beetles in nature.
Several experiments were conducted in which a
semiochemical stimulus composed of myrcene, trans verbenol
and exo-brevicomin was tested as a bait on pine trees to
induce attack by the mountain pine beetle.
Fifty uninfested lodgepole pine trees were baited
with the above composition in June in a lodgepole pine forest
in Manning Park, British Columbia. Many mountain pine beetle
infested trees had been removed from the forest prior to the
experiment in an attempt to control the beetle population.
Forty-eight of the baited trees were subsequently attacked by
the mountain pine beetle (Table 3). In addition 80 trees
were attacked within a 12 meter radius of the ~8 trees (a
total area of 2.2 hectares) while only 86 trees were attacked
in the entire 62.8 hectares oE remaining forest which was
examined by an intensive search.
Thus the bait was very effective in concentrating
attack of beetles on baited trees and trees closely
surrounding them. This result clearly demonstrates that the
bait can be used in post-logging mop-up of residual beetle
able 2. Ranked responses of Dendroctonus ~erosae to funnel
traps baited with myrcene, trans-verbenol and/or exo-
brevicomin, near Princeton, British Columbia, August
15-26, ~=6 replicates.
umber of Beetles Captured
Stimulus*
Males Females Total Female
======================================_=============================
No Bait (control) 3 2 5 nos. too low
Myrcene + exo~Brevicomin2 3 5 nos. too low
Myrcene + trans-Verbenol108 3~ 140 22.9
Myrcene + trans-Verbenol +
exo-Brevicomin141 125 266 47,0
. _ _ .. .. .. . .. . _ _ . _ . _ . _
- *Release rates determined at room temperature as follows:
myrcene, 14 mg/24 h; trans-verbenol 0.40 mg/24 h; exo-brevicomin,
0.05 mg/24
~,2~2~gLgt
able 3. Distribution of attack by ~e~L~ ponderosae on and
around 50 lodgepole pine trees baited with ~yrcene,
trans-verbenol and e~o-brevicomin*, Manning Park,
British Columbia.
No. of % of Total Area of
Attacked Attacked Land
Category of Tree Trees Trees Covered (ha)
=========================8=========================================
Baited 48 22.4
Within 12 m of
baited trees 80 37.4 2.2
Beyond 12 m of
baited trees 86 40.1 62.8
*Release rates determined at room temperature as follows:
myrcene, 17 mg/24 h; trans-verbenol, 1 mg/24 h; exo-brevicomin,
0.50 mg/24 h.
- ~z~
populations. These insects can be removed by harvesting
infested trees in which attack has been induced.
n isolated infestation of 41 trees (12 ponderosa
and 29 lodgepole pine trees) on private land was inaccessible
to logging because of objections by the owner. An accessible
forest was separated by a 50 meter space Erom the
inaccessible infestation. In this latter forest, 16
uninfested pines (12 ponderosa and 4 lodgepole pine trees)
were baited with myrcene, trans-verbenol and exo-brevicomin
in èarly July. An intensive search in September-October
disclosed that all 16 baited trees were attacked by the
mountain pine beetle. In addition, 45 trees ~27 ponderosa
and 18 lodgepole pines) were newly-attacked within
approximately Z0 meters of the nearest baited tree. Only
one attacked tree was found near the previous year's infested
trees in the inaccessible forest, and no additional newly-
attacked trees were located within 50 meters of either
infestation. Therefore, it is concluded that the locus of
the infestation was shifted over 50 meters by the baiting
program.
Five isolated blocks of mountain pine beetle-
infeæted forests were treated in June by baiting one
lodgepole or ponderosa pine tree every 50 meters on a 50
meter grid with myrcene, trans-verbenol and exo-brevicomin.
Five equivalent control blocks were left unbaitedO In the
fall every tree in each block was assessed for attack by the
mountain pine beetle. In the experimental blocks (Table 4)
58.9% of the baited trees were newly-attacked. The
surrounding attacked trees were closer to the baited trees
than to equivalent, marked trees in the control blocks. Most
significantly, the ratio of newly-infested to previous year's
infested trees was 2.5:1 in the baited blocks and 1.8:1 in
the control blocks. Because the blocks were chosen for their
able 4~ Containment of E~s~us ponderosae infestations in
isolated forests by baiting trees on a 50 m grid with
myrcene, trans-verbenol and exo-brevicomin*. Summary
for 5 replicates in various locations through-
out British Columbia.
Criterion Control Forests Experimental Forest
===================================================================
Total Area 106.3 ha 91.6 ha
No. Baited Trees (experimental)
or Equivalent Marked, but not
Baited Trees tcontrol) 373 280
% of Baited or Marked Trees
Attacked 2.7% 58.9%
No. of Surrounding Trees
Attacked 560 458
Mean Distance of Surrounding
Trees from Baited or Marked
Trees 18.5 m 12.5 m
No. Infested Trees in Previous
Year 312 250
Ratio of Newly Infested Trees
to Previous Year Infested Trees 1.8 2.5
*Release rates as in Table 3.
isolated infestations, it ;8 unlikely that there were
significant numbers of beetles attracted from the surrounding
forest into the baited blocks, Rather the emergent beetles
were inhibited from leaving the baited blocks. Thus the
baiting program caused the infestations to be contained
within the baited area.
