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Journal of Chemical Ecology, Vol. 12, No. 2, 1986

SPRUCE B U D W O R M (Choristoneura fumiferana) 1 P H E R O M O N E CHEMISTRY A N D B E H A V I O R A L RESPONSES TO PHEROMONE COMPONENTS AND ANALOGS

PETER J. SILK and L.P.S. KUENEN Pheromone Research Group New Brunswick Research and Productivity Council P.O. Box 6000, College Hill Road Fredericton, New Brunswick E3B 5H1 (Received June 3, 1985; accepted August 1, 1985) Abstract--This paper reviews the sex pheromone chemistry and pheromonemediated behavior of the spruce budworm and related coniferophagous (Choristoneura) budworms. In C. fumiferana, temporal changes in pheromone-gland monounsaturated fatty acids (pheromone precursors) enable the prediction of the primary sex pheromone components. This technique may also be applicable for predicting additional pheromone components. Tetradecanal (14:Aid), previously shown to enhance close-range precopulatory behavior, lowers the threshold of response by males for upwind flight to a pheromone-component source. Spruce budworm males maintain upwind flight to 95:5 (E/Z)-l,12-pentadecadiene (diolefin analog) after initiating upwind flight to a primary-component pheromone source (95 : 5 E/Z11-14 : Aid). This is the first demonstration of apparently normal male flight responses to a pheromone analog. Key Words--Choristoneura fumiferana, spruce budworm, Lepidoptera, Tortricidae, sex pheromone, behavior, flight tunnel, pheromone analog, pheromone fatty acid precursors.

INTRODUCTION

Lepidopteran female sex pheromones are, with few exceptions, multicomponent, consisting of a blend of two or more chemicals emitted at fairly consistent l Lcpidoptera: Tortricidae 367 0098-0331/86/0200 0367505.00/0 9 1986 Plenum Publishing Corporation

368

SILKANDKUENEN

ratios and release rates. These chemical blends elicit in conspecific males sequences of behaviors that include upwind flight which brings males to within close proximity of females. These behaviors are often readily observed in laboratory wind tunnels, and responses by males to synthetic pheromone sources can be compared to their responses to natural pheromone or females. The existence of a pheromone communication system in the spruce budworm (Choristoneura fumiferana Clemens) was demonstrated by Greenbank (1963), but elucidation of the blend of chemicals comprising the female sex pheromone is still incomplete. However, recent progress has been made in defining the sex-pheromone chemistry and pheromone-mediated behavior of this insect. This paper reviews the history and some current research related to the spruce budworm pheromone communication system.

BACKGROUND In the genus Choristoneura (Lepidoptera: Tortricidae), known primary sex pheromone components are comprised of All-unsaturated C~4 carbon-chain compounds. Different species' primary sex pheromone components have different oxygenated functional groups and varying blends of these components (see Inscoe, 1982). Specifically, the coniferophagous spruce budworms comprise a group of closely related (Choristoneura) species, native to North America (Freeman, 1967; Freeman and Stehr, 1967; Powell, 1980). Six species have been studied in terms of their pheromone specificity (Sanders, 1971; Sanders et al., 1974, 1977). The components of these female-produced sex pheromones form a group of congeneric A11-C j4 aldehydes (411-14 :Ald), acetates (A1114 : Ac), and alcohols (2~11-14 : OH), with blends, geometrical isomer ratios, and release rates specific to each species (Table 1). In attempting to characterize the sex pheromone of budworm species through cross-attraction studies, Sanders et al. (1977) concluded that C. fumiferana, C. occidentalis, and C. biennis apparently had similar pheromones while C. pinus pinus, C. orae, and C. retiniana (= C. viridis; Powell, 1980) were mutually cross-stimulating but did not appear to have sex pheromone components in common with the former group. This was an accurate assessment; subsequent research has shown that the former group utilizes 411-14 : Ald's as primary sex pheromone components, whereas the latter, utilize A11-14:Ac's or A11-14 : Ac/A11-14 : OH blends (Table 1). It has yet to be verified that the C. biennis sex pheromone is A11-14 :Ald, although present evidence is strongly supportive (Sanders, 1971; Sanders et al., 1974, 1977). Sex pheromone components of the remaining five species have been documented: C. fumiferana (Sanders and Weatherston, 1976; Silk et al., 1980) and C. occidentalis (Cory et al., 1982; Silk et al., 1982) have been shown to release E/Zll-14:AId as

369

SPRUCE BUDWORM PHEROMONE TABLE 1. SEX PHEROMONE COMPONENTS a OF CONIFEROPHAGOUS Choristoneura

Species C. fumiferana

Primary

Additional (Secondary)

E11-14:Aid 96:4 E/ZI 1-14:Ald

C. occidentaIis

95:5 E/Z11-14:Ald

14:Ald

92:8 E/Zll-14:AId 92:8 E/Z11-14:Ald

89: l 1 E/Z 11-14:Ac

spp.

References Weatherston et al., 1971 Sanders and Weatherston, 1976 Silk et al., 1980 Alford et al., 1983 Cory et al., t982 Silk et al., I982 Alford and Silk, 1983

85:15 E/Z ll-14:OH C. biennis

E/Z11-14:Ald b E/Z ratio unknown

C. orae

82:9:9, E11-14:Ac, ZI 1-14:Ac, E11-14:OH 90:10, 85:15 E/Z11-14:Ac, 85:15 E/Zll-14:OH 92:8,

C. pinus pinus

C. retiniana

E/Z11-14 :Ac

Sanders, 1971 Sanders et al, 1974 Gray et al., 1984

Silk et al., 1985b

E or Z11-14:OH (enhances trap capture)

Daterman et aI., 1984

"E/Z11-14:Ald = (E/Z)-I 1-tetradecenal; E/Z11-14:Ac = (E/Z)-I 1-tetradecenyl acetate. E/Z11-14 :OH = (E/Z)-ll-tetradecen-l-ol; 14:Ald = tetradecanal.

blnferred from cross-attraction studies (Sanders, 1971).

primary sex pheromone components. In contrast, C. p i n u s p i n u s (Silk et al., 1985b), C. retiniana (Daterman et al., 1984), and C. orae (Gray et al., 1984) release E / Z 11-14 : Ac or E / Z 1 1 - 1 4 : A c / E / Z 1 1 - 1 4 : OH blends as primary components (Table 1). However, all species have A 11-14 : Ac in c o m m o n as the major component in the pheromone gland (in references above). In C. f u m i f e r a n a 2~11-tetradecenyl acetate is synthesized de novo only in the pheromone gland, the A 1 1 14 : Ac is the direct biosynthetic precursor to the aldehyde pheromone (Morse and Meighen, 1984). Morse and M e i g h e n (1984) also found that the female diel aldehyde-emission period was synchronous with acetate production, and this supports their hypothesis that in this (coniferophagous) Choristoneura group a metabolic relationship exists between the aldehyde, acetate, and alcohol. It seems likely, therefore, that species specificity in pheromone production is controlled by species-specific metabolic processes, giving rise to different functional groups, ratios, and release rates from the c o m m o n acetate precursor.

370

SILKANDKUENZN REVIEW OF SEX PHEROMONE CHEMISTRY OF SPRUCE BUDWORM

Among coniferophagous budworms, the spruce budworm, C. fumiferana, has been the most intensively studied. Early work indicated that spruce budworm females release a pheromone that "attracts" males (Greenbank, 1963). Subsequently, E11-14 :Ald was identified (Weatherston et al., 1971) as a pheromone component. The importance of adding the Z to the E isomer was determined upon reanalysis of female volatiles and a (96:4) E/Z11-14:Ald blend was shown to maximize trap captures (Sanders and Weatherston, 1976). Solvent extracts of excised pheromone glands were inactive in eliciting male response (Sanders, 1971). Reanalysis of gland extracts identified E11-14:OH (Weatherston and MacLean, 1974) and El l - 1 4 : A c (Wiesner et al., 1979), both of which inhibited trap capture (Sanders and Lucuik, 1972; Sanders et al., 1972; Sanders 1976). More detailed chemical analyses (Silk et al., 1980) of pheromone gland extracts showed that A11-14: Ac (20-40 ng/insect), A11-14 :Ald (1-3 ng/insect), and Axl 1-14 : OH (1-3 ng/insect) were all present in 95 : 5 E/Z ratios; the saturated analogs of each functionality were also present at ca. 1% of the corresponding E isomer. In contrast, effluvia from "calling" females were found to contain E/Z11-14 :Ald (95:5; 10-40 ng/insect/night) and the saturated analog, tetradecanal (14 :Ald) at ca. 2 % of the E11-14:Ald (Silk et al., 1980). In addition, traces of (E)I 1-14:Ac were found; no alcohols were detected. In the same study, field testing showed that there were no significant differences in trap captures between traps baited with all four components (formulated in PVC at female effluvial ratios) compared to captures using the primary components (95:5 E/Z11-14:Aid) alone. The reduction of trap capture by admixture of k l l - 1 4 : A c with 95:5 E/Z11-14:Ald (Sanders et al., 1972) was confirmed; however, this effect appeared to be negated by the presence of 14:Ald, but only when all components were present in synthetic sources in female effluvial ratios (Silk et al., 1980). Pheromone release rate by "calling" females, measured by a specific and sensitive bioluminescent assay technique (Morse et al., 1982, Meighen et al., 1981, 1982), occurs mainly during scotophase in a series of "bursts" at rates as high as 50 ng/hr with considerable individual variability. REVIEW OF PHEROMONE-MEDIATEDBEHAVIOR IN SPRUCE BUDWORM Behavioral patterns involved in mate location in feral insects generally involve upwind flight, apparent close-range orientation, and copulation (Roelofs and Carde, 1977). As in most moths, spruce budworm males locate conspecific females by flying upwind along a pheromone plume. Often, the effects of putative pheromone components on these male behaviors has been inferred from

371

SPRUCE BUDWORM PHEROMONE

a chemical's effect on trap capture (until recently, this was also tree for spruce budworm); however, observations and quantitation of some of these behaviors can be conducted in a sustained-flight wind tunnel (e.g., Miller and Roelofs, 1978). We review here recent field and wind-tunnel work, and present some recent progress. Sanders (1981a) showed that synthetic 95:5 E / Z 1 1 - 1 4 : A i d s were equivalent in "attraction" to virgin females in field trapping experiments when using a 0.03 % PVC source, which releases these primary components at a rate close to that of a "calling" virgin female (Silk et al., 1980). Furthermore, in preliminary wind-tunnel work, some males demonstrated an apparent full range of precopulatory behaviors, e.g., upwind flight, courtship, and copulatory attempts in response to only these two primary components (Sanders, 1979). However, more detailed observations in the wind tunnel (Sanders et al., 1981) showed that males exposed to pheromone produced by "calling" females exhibited a higher incidence of upwind flight and made more rapid upwind progress than males exposed to a similar concentration of synthetic pheromone (95 : 5 E/Z11-14 : Aid). Sanders and Seabrook (1982) concluded that it was unlikely that other chemicals were involved in the "attraction" phase of the mating process. However, recent observations in our laboratory's wind tunnel and in the field (Alford et al., 1983) indicated an effect of tetradecanal (14:Ald) on the behavior of male spruce budworm. A greater number of males initiated upwind flight and continued on to contact a source with ca. 5 % 14 :Ald added to the A 11-14 : Ald's than when only the A11-14:Aids were present. The addition of E11-14 : Ac to the 2xl 1-14 : Aids decreased the males' responsiveness to the aldehydes, but when present at low levels, its effect appeared to be attenuated when 14:Ald was also present (Alford et al., 1983). This latter effect was also seen in earlier field-trapping experiments (Silk et al., 1980) and was subsequently confirmed by further laboratory wind-tunnel studies (Sanders, 1984). In addition, Sanders (1984) found that duration of sustained flights was significantly longer in response to "calling" females than to any synthetic sources (with or without 14:Ald), implying that the synthetic blends are incomplete with respect to the female-emitted blend. RECENT PROGRESS

It is apparent that not all the chemicals involved in the sex pheromone communication system of spruce budworm are known. In monitoring and mating disruption programs, however, it may not be essential to know every minor component although, as Roelofs has pointed out (1978), trap specificity and potency may be greatly increased as the synthetic lure more closely duplicates the natural pheromone, and it is presumed that the efficacy of mating disruption

372

SILK AND KUENEN

would likewise be enhanced by a "more complete pheromone." Sanders (1984) concluded that, although single components can cause considerable mating disruption in noctuids (Campion et al., 1981), incomplete blends are considerably less effective against tortricids (Charlton and Card6, 1981; Roelofs and Novak, 1981; Sanders, 1981b). This has led many to the conclusion that elucidation of the "complete" pheromone blend for budworm is of importance prior to further major mating-disruption tests. Recent work in our laboratory has, therefore, focused on the identification of the "complete" spruce budworm pheromone. Previous analyses of female spruce budworm effluvia (Silk et al., 1980), using a Porapak | Q collection technique, did not indicate, at least from a chemical perspective, the presence of other components. This method, however, does introduce relatively large amounts of contamination and minor components may have been obscured by this background contamination. The fact that, chemically, minor components are present in very low quantities in spruce budworm prompted the use of indirect techniques to ascertain component identity. Recently, Bjostad and Roelofs (1981, 1983) demonstrated that fatty acid precursors of female sex pheromone components can be identified and used to predict the presence of minor pheromone components (Bjostad and Roelofs, 1983; Bjostad et al., 1984). A technique for rapidly identifying these monounsaturated fatty acids in pheromone glands excised from female moths, using GC-MS analysis after dimethyldisulfide derivatization (DMDS) of gland extracts has been developed. A detailed analysis of monounsaturated fatty acids present in the pheromone glands of C. fumiferana, C. occidentalis, and C. pinus TABLE 2. MONOUNSATURATED FATTY ACID ESTERS OBTAINED BY D M D S DERIVATIZATION OF PHEROMONE GLAND EXTRACTS FROM THREE

Choristoneura

SPEC1ES a

DMDS b z~Fatty ester

C. fumiferana

C. occidentalis

C. pinus pinus

9-12:Me 5-14:Me 7-14:Me 9-14: Me ll-14:Me 7-16:Me 9-16:Me ll-16:Me 12-16:Me

T VS T VS M M L M T

T VS T VS L M L M VS

T T T VS S S L S ND c

aQuantitative estimate relative to the most abundant fatty ester DMDS adduct (C12-C16). L 10050; M 50-30; S 30-10; VS 10-1; T < 1 (L, M, S, VS, T: large, medium, small, very small, and trace, respectively; in %). Data from Dunkelblum et al., 1985. bMethanolyzed samples of chloroform-methanol extracts. eND, not detected.


373

pinus was camed out; the techniques and results are discussed in detail elsewhere (Dunkelblum et al., 1985) and are summarized in Table 2. As can be seen, the major pheromone-gland components (which have been previously identified) are readily correlated with their corresponding fatty acids. For example, in these three budworm species, the E/Z11-14 : Me (E/Z11-tetradecenoic acids, methyl esters) are correlated with the zXl 1-Ci4 moieties which comprise the primary pheromone components (Tables 1 and 2). The fatty acid profile is very similar for all three species. The other unsaturated fatty acids may be precursors to as yet unidentified secondary sex pheromone components in these species. In some female moths, pheromone titer appears to be quite low on eclosion and increases to a maximum in a few days [e.g., Trichoplusia ni Hiibner (Shorey and Gaston, 1965)]. Based on this fact, analysis of monounsaturated fatty acids in spruce budworm females by the DMDS method was repeated with the view of ascertaining whether changes in fatty acid profile occurred with moth age. Pheromone glands were obtained from groups of ca. 20 females that were in the pupal stage (just prior to emergence), 1 hr post-emergence, and 48 hr postemergence (all pupae and adults were maintained on a 16 : 8 light-dark cycle and glands were excised during the 2nd and 3rd hr of scotophase, coincident with mature females' peak "calling" period). Pheromone glands (three replicates) excised from these three groups were extracted with chloroform-metha-

TABLE 3. MONOUNSATURATED FATTY ACID ESTERS OBTAINED BY D M D S DERIVATIZATION OF EXTRACTS FROM PUPAL AND 4 8 - H o u R POSTECLOSION SPRUCE BUDWORM PHEROMONE GLANDSa

DMDS t' ,5Fatty ester 5-14:Me 7-14:Me 9-14:Me 11-14:Me 7-16:Me 9-16:Me 11 16:Me 12-16:Me

Pupal glands " T T S, but largest 14:Me T S L, both E/Z; largest 16:Me VS T

48 h post-eclosion T T S M, both E/Z isomers present; largest 14:Me M L, both E/Z isomers; largest 16:Me M ND d

aKuenen, Dunkelblum, and Silk, unpublished data. bL, M, S, VS, and T same meaning as footnote in Table 3. "Results for 1-h postemergence extracts were not significantly different from preemergence extracts and are not included in the table. dND, not detected.

374

SILK AND KUENEN

nol (2: 1) and subjected to acid-methanolysis followed by the DMDS reaction and capillary GC-MS (as in Dunkelblum et al., 1985). The results are presented in Table 3. A large increase is seen for A l t 14: Me (from < 1% to 30-50%), and this is to be expected since this fatty acyl moiety is most likely the direct biosynthetic precursor to A11-14:Ac and this component to the pheromone, A11-14:Ald (Morse and Meighen, 1984). Perhaps more significantly, a large increase in titer occurred with two other monounsaturated fatty acids: A7-16 : Me and A11-16 : Me with the latter showing the largest increase. This prompted the supposition, following the corollary of A1114 : Me ~ A11-14 : Ac ~ A11-14 : Aid, that a similar sequence of events may be occurring in the pheromone gland of the spruce budworm for these A16 components. Although this does not preclude the other fatty acids (and certainly only monounsaturated moieties would be detected by this method), these two components were considered a suitable starting point for further chemical and behavioral analyses. Reanalysis of female gland extracts (Dunkelblum and Silk, unpublished data) indicated that, indeed, A11-16:Ac is present in the spruce budworm sex pheromone gland ( < 0 . 1 % of El l - 1 4 : A c ) but that A7-16:Ac could not be detected. However, neither A11-16 : Aid nor A11-16 :Ac was detected in effluvial material obtained by the Poropak Q collection method (Silk et al., 1980), although background contamination probably precluded detection. Because A11-14: Ac is the biosynthetic precursor to A11-14 :Ald (primary pheromone components), it was assumed, as a first step, that since A11-16:Ac was determined as a gland component, it might be emitted as the aldehyde. However, initial wind-tunnel tests to determine the possible function of A l l - t 6 : A l d ' s were inconclusive; further tests will be warranted if A11-16 : Ald's are found in female pheromone-gland volatiles. The effects on behavior of putative pheromone components are usually assessed by adding them to compounds with known activity, (e.g., Linn and Gaston, 1981; Baker and Card6, 1979). Alternatively, changes in male behavior have been measured in response to removing one or more components from the believed complete volatile blend, or by giving males a choice between two merging odor plumes (e.g., Teal et al., 1986). We have recently tested another approach relating to male response to low dosages of pheromone blends. More specifically, we hypothesized that males would have a lower response threshold to "more complete" pheromone blends, i.e., the active space (Bossert and Wilson, 1963) would become greater as the pheromone blend being tested more closely approached the natural female-emitted blend. To test this hypothesis in our sustained-flight wind tunnel, we employed two "pheromone" sources (Figure 1). Both sources (rubber septa) were suspended, one behind the other, by thread (as in Baker and Kuenen, 1982; Kuenen and Baker, 1983) 15 cm above the center of the tunnel floor. The downwind

375

SPRUCE B U D W O R M PHEROMONE

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source (DS) was constant at 3 or 10 t~g 95 : 5 E/Z11-14 : Ald, while the upwind source (US; the test source) ranged from 3 ~g (95:5 E/ZI 1-14:Aid) down to 30 ng in half-log. .z ~2

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379


TABLE 6. RESPONSESOF MALZ SPRUCE BUDWORMTO (1) AI 1-14:Ald (2) DtOLEFIN ANALOG, AND (3) 1 : 1 MIXTUREOF BOTHa

Mean % moths activatedb Mean % moths initiating flight Mean % moths flying upwind Mean distance flown per moth flying upwind (cm)C

(1) 10 ngA11-14:Aid

(2) 10 ng DO

84.0a (16.80) 92.0a (17.80) 48.0a (11.00) 150.8 (69.90)

8.0b (11.00) 36.0b (7.20) 4.0b (9.00) 185 ( - )

(3) (1) + (2) 92.0a (17.80) 92.0a (11.00) 48,0a (11.00) 150.8 (51.16)

azXll-14:Ald = 95:5 E/Z11-14:Aid; DO = diolefin analog. N = 25 (five groups of five); values are means (+ SD) calculated from means of each group of five moths tested. bMeans in each horizontal row having no letters in common are significantly different; P < 0.05, Duncan's new multiple-range test. CMeans were not analyzed since only one moth flew up-tunnel (center column) when diolefin alone was present. placed in a circle around traps baited with A l l - 1 4 : A l d ' s , trap capture was reduced to a level not significantly different (P > 0.05) from traps surrounded by equally spaced P V C s containing 0.03% A 1 1 - 1 4 : A l d ' s . F r o m this we concluded that the diolefin had biological activity, but the trap capture data were ambiguous. W e then tested the diolefin in our wind tunnel. Male spruce b u d w o r m responses to (1) A l l - 1 4 : A l d ' s , (2) diolefin, and (3) 1 + 2 were examined. In measures o f activation, flight initiation, flight distance, and percentage source contact, males responded similarly (Table 6; P > 0.05) to A 1 1 - 1 4 : A l d ' s alone and when in admixture (1 : 1) with the diolefin, but by itself the diolefin did not elicit upwind flight in males. [Although one male reached the upwind portion o f the tunnel (Table 6), its flight path appeared random and was rarely in or near the analog plume.) In another study, male responses to the diolefin alone were not distinguishable (P > 0.05) from responses to a blank (control) source (Kuenen and Silk, unpublished data). Thus the diolefin did not enhance or diminish the responsiveness o f males flying upwind toward a " p h e r o m o n e " source. However, we reasoned that trap capture in diolefin-baited traps (mid-season study) may have occurred after males responded to female-emitted pheromone, while no pheromone sources (virgin females) were present in our late season study where diolefin did not elicit male activity (trap capture). As a first test o f this hypothesis, we allowed individual males to initiate flight to two chemical sources (see Figure 1). The upwind source contained diolefin alone or was blank, while the downwind (15 cm) source contained A 1 1 - 1 4 : A l d ' s . After males had flown to within 140 cm o f the upwind source, the downwind source was quickly pulled upward by its supporting thread. M a l e s ' progress was then recorded. Most notably, males continued their normal upwind ap-

380

SILK AND KUENEN

proach to the diolefin source [upwind source; mean distance flown 163.3 cm + 45.73 (SD); N = 24/50 tested], while, as expected, they soon initiated crosswind casting (Kennedy and Marsh, 1974; Marsh et al., 1978) when the upwind source was blank [mean distance flown 119.0 cm + 29.75 (SD); P < 0.05; t test; N = 30/50 tested]. The males' flights to the diolefin source were not visually distinguishable from their flight responses to a A l l - 1 4 : A l d source, and 16 o f the 24 moths flying upwind continued their upwind flight to reach and land on the diolefin source.

CONCLUSIONS Progress in understanding the sex pheromone chemistry of the spruce budworm in relation to male behavior has been made in recent years. However, the sex pheromone blend o f the b u d w o r m is not completely defined. Very low emission rates o f additional pheromone components have made it difficult to identify these components. Identification of pheromone gland fatty acids, and particularly their temporal variation in relation to pheromone production, may become a very useful technique in identifying these additional components. The data we have presented on male flight thresholds is not definitive at this point, but represents an approach to the study o f the spruce budworm communication system. Our analyses of male responses to a pheromone analog are also preliminary; however, the demonstration o f normal male upwind flight in response to the diolefin analog is, to the best o f our knowledge, the first report of the observation o f this behavioral response to a pheromone analog. Acknowledgments--This research was funded in part by the New Brunswick Department of Natural Resources, and the Canadian Forestry Service. We thank Dr. C. Northcott (RPC) for synthesis of AI 1-16 : Ald and the diolefin analog from a nonaldehyde source, and Dr. G. Lonergan (UNB) for synthesis of the diolefin from A11-14:Ald. We also thank Dr. E. Butterworth and M. McClure for technical assistance and L. Jewett for typing the manuscript. Special thanks go to Dr. E. Dunkelblum, for his expertise and enthusiasm during a sabbatical year from the Volcani Center; Bet Dagan, Israel during 1984-85 with PRG/RPC.

REFERENCES ALFORD, A.R., and SILK, P.J. 1983. Behavioral effects of secondary components of the western spruce budworm (Choristoneura occidental&) Free. J. Chem. Ecol. 10:265-270. ALFORD, A.R., SINK, P.J., McCLURE, M., GIBSON, C., and FTTZPATRICK,J. 1983. Behaviorai effects of secondary components of the sex pheromone of the eastern spruce budworm, Choristoneura fumiferana (Lepidoptera: Tortricidae). Can. Entomol. 115:1053-1058.

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