Note: Descriptions are shown in the official language in which they were submitted.
2041~29
METHOD AND COMPOSITION FOR
ATTRACTING AND CONTROLLING HEMLOCK LOOPER8
FIELD OF THE INVENTION
This invention relates to methods and composi-
tions for attracting, trapping and controlling hemlock
looper, Lambdina fiscellaria, a pest of coniferous forests
in North America.
BACKGROUND OF THE INVENTION
,:
The hemlock looper, Lambdina fiscellaria (Guenee)
(Lepidoptera: Geometridae) is a native North American moth
that inflicts severe damage on coniferous trees, particu-
larly balsam fir, Abies balsamea (L.) Mill., and western
hemlock Tsuga heterophylla (Raf.) Sarg. In eastern North
America, the hemlock looper ranges from Newfoundland to
Saskatchewan in Canada, and from the Great Lake States to
the eastern seaboard of the U.S.A. In the west, it ranges
from southwestern Alaska, throughout British Columbia and
south to oregon (Otvos 1973).
Since the turn of the century, the hemlock looper
in eastern North America has caused over 20 mill m3 of tree
mortality, enough to build more than 500,000 houses.
Moreover, sublethal defoliation has stressed and predis-
posed trees to attack by secondary pests, thereby increas-
ing the loss of mechantable timber.
The hemlock looper is the most important forest
insect pest in Newfoundland, where the most extensive
studies on its biology, impact and control have been done.
Adverse weather, starvation, predators, parasites and
diseases all contributed to the collapse of hemlock looper
outbreaks in Newfoundland, but failed to do so before
intolerable tree mortality occurred (Otvos 1973). Native
fungi, principally Entomo~hthora aulicae, appear to be the
major factors terminating outbreaks, but scientists have
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2041~29
-- 2 --
not yet been able to mass produce the fungi under labora-
tory conditions (Dunphy and Nolan 1980), which is necessary
for use in spray programs (Hudak et al. 1985). DimilinT~,
an insect growth regulator, has been successfully tested
(Raske et al. 1986), but is not yet registered against
hemlock loopers. The biological insecticide Bacillus
thurinqiensis, and the chemical Fenitrothion, remain the
only control options available to forest managers. Al-
though Fenitrothion causes very little environmental impact
when used as recommended (National Research Council 1975),
Hudak et al., 1988), at high dosages, it is harmful to
forest birds (Peakhall and Bant 1983) and may also affect
trout and salmon by killing aquatic insects upon which they
prey (Government of Newfoundland and Labrador, Department
of Consumer Affairs and Environment Research and Asses~ ?nt
Branch 1978). Thus, use of Fenitrothion has been discon-
tinued in some provinces and further restrictions are
expected in the future. Consequently, effective methods to
control hemlock loopers are limited in number and scope.
The key factor for suppressing, and possibly
preventing, hemlock looper outbreaks is a sensitive and
practical means for early detection and accurate forecast-
ing of increasing, pre-outbreak populations. Tree-beating,
egg- and pupa-counting for monitoring population fluctu-
ations (Kinghorn 1952, Thompson 1985, Carolin et al. 1964,
Condrashoff 1967, Shepherd and Gray 1972, Otvos 1974,
Dobesberger 1989) are laborious and time consuming.
Employment of sex pheromones, as released by
calling lepidopteran females has proven to be a powerful
tool to survey populations. Numbers of males of numerous
species attracted to and caught in pheromone-baited traps
have been well correlated with population densities
35 (Granett 1974, Riedl et al. 1976, Shelton and Wyman 1979,
Tingle and Mitchell 1981, Ramaswamy et al. 1983). In
western Canadian forests, the sex pheromone of the Douglas-
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'" 2041~29
.
-- 3
fir tussock moth, OrqYia pseudotsuaata, is operational as
a monitoring tool (Borden 1990), and in the east, spruce
budworm populations are now routinely monitored by sex
pheromone traps (Sanders 1988). Thus, pheromone trap
catches can indicate size and locations of infestations, so
that control measures with insecticides can be carefully
planned and prepared for and targeted exclusively on areas
where they are needed.
Moreover, sex pheromones themselves have become
control agents. Several field experiments have shown that
synthetic sex pheromone components, released individually
or in combination from several point sources, can cause
male disorientation and mating disruption (Gaston et al.
1967, Mitchell et al. 1975, Cardé et al. 1977, Sower and
Daterman 1977, Taschenberg and Roelofs 1978, Sower 1980,
McLaughlin et al. 1981, Mitchell 1981, Kydonieus and Beroza
1982, Palaniswamy et al. 1982, 1983, 1984, Sanders and
Meighen 1987). Increasing knowledge about the biology of
forest lepidopterans and their complete pheromonal blends,
as well as knowledge about the optimal mode of releasing
synthetic pheromones (Sanders 1981, Alford and Silk 1983),
may allow us in the near future to deploy sex pheromones as
practical and environmentally-sound control agents for
forest protection.
Relatively recently, sex pheromones have been
identified for several geometrid species including the
winter moth, Operophtera brumata (Bestmann et al. 1982,
Roelofs et al. 1982), the giant looper, Boarmia selenaria
(Becker et al. 1983, 1987), the fall cankerworm, Alsophita
pometaria (Wong et al. 1984), Peribatodes rhomboidaria
(Buser et al. 1985), Sabulodes caberata (McDonough et al.
1986), the bruce spanworm, Operophtera binceata (Underhill
et al. 1987), Semiothisa signaria, S. bicolorata, S.
ulsterata (Millar et al. 1987), Eufidonia convergaria and
Caripeta augustiorata (Millar et al. 1984).
-
2041~29
-- 4
1,Z3,Z6,Z9-Nonadecatetraene, the sex pheromone of
the winter moth, has already been successfully used to
monitor populations of that insect in South Germany (Albert
et al. 1984) and Scotland (Stoakley 1985), and synthetic
sex pheromone components of the fall cankerworm
(Palaniswamy et al. 1986) have been shown to disrupt
orientation behaviour of that moth.
Evidence of the existence of a sex pheromone for
hemlock loopers was provided using "sticky" traps baited
with virgin females (Otvos 1972, Ostaff et al. 1974). A
synthetic sex pheromone could provide new means for accu-
rately predicting outbreaks and surveying hemlock looper
populations. In addition, because hemlock looper outbreaks
are characteristically intense and concentrated, a syn-
thetic pheromone has excellent potential as a behavioural-
disruptant, and a biorational insecticide.
It has not been possible, based on the above
information, to predict or infer the chemical nature of the
Lambdina fiscellaria pheromone, nor has it been possible to
predict or infer the response of insects in nature to it.
SUMMARY OF THE lNv~NllON
This invention pertains to methods and composi-
tions for attracting and controlling hemlock loopers,
Lambdina fiscellaria. In one aspect, a method of attract-
ing male L. fiscellaria comprises the deployment fromcontrolled release devices of 5,11-dimethylheptadecane.
In another aspect, a method of attracting male L. fiscel-
laria comprises the deployment from controlled release
devices of 5,11-dimethylheptadecane alone or in combina-
tion with any one or more of 5-methylheptadecane, 7-methyl-
heptadecane and 2,5-dimethylheptadecane.
- 2041~29
DRAWINGS
In the drawings:
Figure 1 illustrates graphically detector re-
sponse, flame ionization detector (top) and electroanten-
nogram detector (bottom), to the four natural pheromone
components of the invention in relation to retention time;
Figure 2 illustrates schematically the chemical
structure of the four pheromone components of the inven-
tion.
Figure 3 illustrates block diagramatically males
captured per trap in relation to synthetic mono- and
dimethyl heptadecane combinations; and
Figure 4 illustrates block diagramatically males
captured per trap in relation to synthetic mono- and
dimethyl heptadecane combinations.
DETAILED DESCRIPTION OF SPECIFIC
EMBODIMENTS OF THE IN~7ENTION
We have demonstrated that female hemlock loopers,
Lambdina fiscellaria, contain four compounds that elicit
excitatory responses in the antennae o~ males, and in
various compositions attract males. The essenae of our
discovery is that compositions comprised of 5,11-dimethyl-
heptadecane alone or in combination with any one or more of
5-methyheptadecane, 7-methylheptadecane and 2,5-dimethyl
heptadecane are highly attractive to male _. fiscellaria in
the field, indicating that these compositions can be used
to control the behaviour of hemlock loopers. Because these
compositions, when deployed in controlled release devices,
are very effective in capturing males in baited traps,
2041~29
these compositions can further be used to monitor hemlock
looper populations.
Example 1
This example describes the identification and
synthesis of the sex pheromone of Lambdina fiscellaria.
Experimental insects were laboratory-reared or
field collected near St. John's, Newfoundland. Sexed pupae
and moths were kept at 20~C, 70% RH and a photoperiod of
16:8 (L:D). Pheromone glands of calling females were
excised and extracted in hexane for 2 min. Gas chromato-
graphic (GC) analyses on two glass capillary columns (DB-
210, DB-l) utilizing both flame ionization (FID) and
electroantennographic detection (EAD) (Arn et al. 1975)
revealed four EAD-active compounds (Figure 1) with reten-
tion indices similar to octadecane. Hydrogenated extracts
elicited the same antennal response pattern, indicative of
saturated compounds. GC-mass spectroscopic (MS) analyses
(HP 5985B) of EAD-active volatiles of another geometrid,
the western false hemlock looper, Nepytia freemani dis-
closed a dimethylheptadecane, suggesting that the bioactive
compounds in L. fiscellaria may be saturated mono- or
dimethyl-branched heptadecanes. Retention characteristics
of the two early EAD-active compounds (Figure 1) indicated
monomethylheptadecanes. Synthetic 7- and 5-methylhepta-
decane co-eluted with EAD-responses to pheromone extracts.
The structure of 5,11-dimethylheptadecane was derived from
the branching pattern of these two mono-methylheptadecanes
(Figure 2) and from GC-MS analysis of a gland extract
containing 134 female equivalents. Retention characteris-
tics of the later-eluting EAD-active compound indicated a
dimethylheptadecane with a 2-methyl position for one of the
branch points. Synthetic 2,5- but not 2,7-dimethylhepta-
decane elicited strong antennal responses. 7- and 5-
Dimethylheptadecane and 5,11- and 2,5-dimethylheptadecane
.1
2041529
coincided with antennal responses to pheromone extracts on
two GC columns with different retention characteristics
(DB-l and DB-210). Monitoring of selected ions indicative
of methyl-branches (GC-MS, GC-column and temp. program as
in Figure 1) confirmed the presence of these compounds in
an extract of 83 female L. fiscellaria pheromone glands.
7-Methylheptadecane was synthesized by treating
7-heptadecanone with methyl magnesium bromide to give 7-
methyl-7-heptadecanol, which was converted to an alkene
mixture by acid dehydration. Catalytic hydrogenation on 5%
palladium on charcoal yielded racemic 7-methylheptadecane.
Racemic 5-methylheptadecane was synthesized as described
above using 5-heptadecanone as starting matorial. To
synthesize 2,5-dimethylheptadecane, 5-methyl-2-hexanone was
added to dodecyl magnesium bromide in ether. Usual work-
up yielded 2,5-dimethyl-5-heptadecanol. Dehydration and
hydrogenation produced the isomeric 2,5-dimethylhepta-
decanes. For the synthesis of 5,11-dimethylheptadecane,
cycloheptanone was reacted with cyclohexamine, producing N-
cyclohexyl-cycloheptylimine, which was alkylated with 1-
iodobutane. Following hydrolysis, 2-butylcycloheptanone
was oxidized with m-chloroperbenzoic acid in CH2Cl2 and
reduced with diisobutylaluminumhydride in THF to yield the
hemiacetal of 7-hydroxyundecanal. Treatment with hexyl
magnesium bromide produced 5,11-heptadecanediol which was
oxidized with pyridinium chlorochromate and reacted with
methylene triphenylphosphorane Wittig reagent in dimethyl-
sulphoxide. Hydrogenation yielded the isomerlc 5,11-
dimethylheptadecane mixture.
Example 2
This example describes two experiments that were
conducted with synthetic pheromone. The objective was toverify that the synthetic pheromone determined in Example
2041~29
-- 8
1 mimicked the attractiveness of the pheromone of female L.
fiscellaria.
Synthetic 7- and 5-methylheptadecane, and 5,11-
and 2,5-dimethylheptadecane were field tested near
Flatrock, Newfoundland, from 19 September - 3 October,
1990, employing a completely randomized block design. Data
compiled in Figures 3 and 4 indicate high biological
activity of both dimethylheptadecanes. While 5,11-di-
methylheptadecane alone was attractive to males, theaddition of 2,5-dimethylheptadecane synergized its attrac-
tion (Figures 3, 4). The monomethylheptadecanes did not
effect trap catches (Figures 3, 4). Since they elicited
significant antennal responses (Figure 1), they may be
attractive at different ratios or release rates, or may
have behavioural activity during courtship. The lack of
responses to virgin females is consistent with the previous
findings in trapping experiments that hemlock looper
females were only weakly attractive (Otvos 1972, Ostaff et
al. 1974).
Discussion of Data Gathered and
Illustrated in Drawings
Figure 1: Detector responses to one female
equivalent of pheromone extract chromatographed on a
Hewlett Packard 5890A instrument (DB-210 column, 1 min. at
70~C, 20~C/min to 130~, 2~C/min to 220~C). The antennal
recording (EAD), carried out with a single antenna of male
L. fiscellaria, was so sensitive that the pheromone compo-
nents were detected, even though they were in amounts that
were below the detection threshold of the flame ionization
detector (FID). 5,11-Dimethylheptadecane (Figure 2)
invariably elicited the strongest antennal signal. Re-
sponses to 2,5-dimethylheptadecane and 7-methylheptadecane
were always smaller and the response to 5-methylheptadecane
was not always present.
- 20~1~29
Figure 2: Mono- and dimethylheptadecanes present
in female L. fiscellaria pheromone glands: 5Me-17Hy=5-
methylheptadecane, 7Me-17Hy=7-methylheptadecane, 5,11 diMe-
17Hy=5,11-dimethylheptadecane, 2,5-diMe-17Hy=2,5-dimethyl-
heptadecane.
Figure 3: Captures of male L. fiscellaria in
sticky traps (Sandia Die and Cartridge, Albuquerque, NM)
baited with canditate pheromone components alone (100 ~g
each) and in combination, September 19-21, 1990, Flatrock,
Newfoundland, N=3. Bars topped by the same letter are not
significantly different (ANOVA, followed by Duncan's
Multiple Range Test, P < 0.05).
Figure 4: Captures of male L. fiscellaria in
Multipher traps (Biocontrol Services, Ste-Foy, Quebec)
baited with binary, ternary and quaternary combinations of
four candidate pheromone components (100 ~g of each com-
pound), 27 September - 3 October, 1990, Flatrock, Newfound-
land, N=24. Bars topped by the same letter are not sig-
nificantly different (ANOVA, followed by Duncan's Multiple
Range Test, P < 0.05).
As will be apparent to those skilled in the art
in the light of the foregoing disclosure, many alterations
and modifications are possible in the practice of this
invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be
construed in accordance with the substance defined by the
following claims.
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'"' 2041529
-- 10 --
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