Specificity of male response to multicomponent pheromones in noctuid mothsTrichoplusia ni andPseudoplusia includens

The response of male cabbage looper (CL) and soybean iooper (SBL) moths was observed in the flight tunnel and measured in field tests to the six-component CL pheromone, the five-component SBL pheromone, and toZ7–12: OAc, the major component common to each pheromone. In both the flight tunnel and the field, male CL exhibited significantly greater levels of response to their six-component blend than toZ7–12: OAc alone. A low level of cross-attraction of male CL to the SBL pheromone was observed in both the flight tunnel and the field, but it was quantitatively and qualitatively similar to their response toZ7–12: OAc alone. Thus the minor components of the SBL blend did not appear to disrupt the flight behavior of male CL. With respect to SBL, in the flight tunnel males also exhibited a greater level of response to the five-component blend compared toZ7–12: OAc, but in the field their response was not significantly different to either treatment. There was also a low level of cross-attraction of male SBL to the CL blend, but this appeared to involve a significant arrestment effect on the upwind flight of males, as well as a difference in male sensitivity to the blend of components compared withZ7–12: OAc alone. The observed arrestment effect may have been due to male perception of one or more minor components of the CL pheromone. The results show that the multicomponent pheromones of these species function effectively as specific mating signals and that discrimination of odor quality by male moths can occur as the result of minor components affecting male sensitivity or their upwind flight response to the pheromone.     

Response specificity of male pink bollworm moths to different blends and dosages of sex pheromone

Male pink bollworm,Pectinophora gossypiella, were tested in a sustained flight tunnel to 119 blend-dosage combinations of the sex pheromone components, (Z,Z)- and (Z,E)-7,11-hexadecadienyl acetates, which are released by conspecific females in a 6139 ratio. Hierarchical cluster analysis was used to define an area of peak attraction. Within this area males were most sensitive at lower dosages to ratios around the natural blend of components, but exhibited peak response levels at higher dosages to a wide range of blends, with a shift in blend preference to higherZ,Z isomer ratios at the highest dosage tested (10 mg). Male response specificity appeared to be influenced exclusively by a threshold for initiation of upwind flight, and not arrestment of upwind flight. The results are compared with those of another species, the Oriental fruit moth.     

Wind tunnel studies of sex pheromone-mediated behavior of the Hessian fly (Diptera: Cecidomyiidae)

In a wind-tunnel, male Hessian flies flying toward a source of the female-produced sex pheromone exhibited flight maneuvers very similar to those described for male moths. Upwind flight, consisting of zigzagging and straight flight upwind, was initiated within seconds after flies were placed in the odor plume. This upwind flight was sometimes interrupted by casting, which consisted of wide excursions in the horizontal plane ranging 10–35 cm across the central zone of the tunnel. Comparison of the flight maneuvers of males exposed to ten female equivalents of a hexane extract of female ovipositors and males exposed to 20 ng of (2S)-(E)10-tridecen-2-yl acetate (SE10-13:OAc), which has been identified as a component of the Hessian fly sex pheromone, indicated that the sex pheromone probably contains additional components. However, SE10-13: OAc elicited upwind flight and source location by a significant number of males, even at dosages as low as 2 ng on filter paper. At the highest dosage of SE10-13:OAc tested (200 ng on filter paper), there was a significant decrease in net flight velocity and a slight, but not significant, reduction in the number of males contacting the odor source. The addition of increasing amounts of the R enantiomer to the S enantiomer resulted in increased inhibition of upwind flight and source contact by males.     

Activity of perfluorobutyl-containing components in pheromone blend of cabbage looper moth,Trichoplusia ni

Substitution of nine hydrogens by nine fluorines in the butyl terminus of (Z)-7-dodecenyl acetate, the major component of the pheromone blend of the cabbage looper,Trichoplusia ni (Lepidoptera: Noctuidae), produces a highly volatile analog that is significantly less active as a replacement for the natural pheromone component, either alone or substituted in the sixcomponent pheromone blend of this species. When 9,9,10,10,11,11,12,12, 12-nonafluoro-(Z)-7-dodecenyl acetate (nf-Z7-12: OAc) was tested in a wind tunnel as a single component or as part of the six-component blend, males exhibited preflight activation, but they did not orient in the pheromone plume and fly upwind over a five-decade range of doses at levels comparable with those of the natural component and blend. Addition of large amounts of nf-Z7-12:OAc to the optimal dose of the natural blend also did not effect flight arrestment as when increased amounts of Z7-12:OAc were added. The nonafluoro (nf) analog of (Z)-9-tetradecenyl acetate, a minor component in theT. ni blend, did not affect male behavior when substituted in the sixcomponent blend, and substitution of both nf analogs in the natural blend produced the same results as observed for blends containing nf-Z7-12:OAc. The lack of an effect with substitution of nf-Z9-14:OAc is discussed in relation to the reported redundancy in the action of minor components inT. ni.     

Behavioral responses ofSpodoptera littoralis males to sex pheromone components and virgin females in wind tunnel

The major component of the sex pheromone of femaleSpodoptera littoralis, (Z,E)-9,11-tetradecadienyl acetate (1), elicited all steps of the male behavioral sequence, i.e., wing fanning and taking flight, oriented upwind flight and arrival to the middle of the tunnel, close approach and contact with the source. The activity was equivalent to that elicited by virgin females. In the range of doses tested, the dosage of1 had no significant effect on the number of source contacts. Male response was significantly affected by light intensity, being optimum at 3 lux. Activity of the minor components (Z)-9-tetradecenyl acetate (2), (E)-11-tetradecenyl acetate (3), tetradecyl acetate (4), (Z)-11-tetradecenyl acetate (5), and (Z,E)-9,12-tetradecadienyl acetate (6) was significantly lower than that of the major component when assayed individually. In multicomponent blends compound4 appeared to strongly decrease the number of males arrested at the source, the effect being particularly important when compound5 was present in the blend. Results of single sensillum experiments confirmed the existence of two main physiologically distinct sensillar types. The most common type of sensilla contained a neuron that responded specifically to compound1. A second type of sensilla, located laterally on the ventral sensory surface, contained two receptor neurons responding to compound6 and to (Z)-9-tetradecenol. Among short sensilla, one hair responded to compound4 and could represent a minor sensillar type. No sensory neuron was found to detect the other minor pheromone compounds2, 3, and5.Dedicated to the memory of the late Prof. Félix Serratosa (1925–1995).     

More Rare Males in <Emphasis Type="Italic">Ostrinia</Emphasis>: Response of Asian Corn Borer Moths to the Sex Pheromone of the European Corn Borer

A previous flight tunnel study showed that 3–5% of European corn borer (ECB) moths, Ostrinia nubilalis (Z/E11-14:OAc), could fly upwind and make contact with sources releasing the sex pheromone of the related Asian corn borer (ACB), Ostrinia furnacalis (2:1 Z/E12-14:OAc). In this study, we show that rare males (3–4%) are also present in South Korean ACB that respond to the sex pheromone blends of the ECB UZ (97:3 Z/E11-14:OAc) and BE (1:99 Z/E11-14:OAc) pheromone races. We also show that the upwind flight response of a significant proportion of male ACB was antagonized by the addition of 1% Z9-14:OAc to the ACB blend, a compound that also antagonizes the upwind flight of ECB males. Male ACB flight behavior was not, however, affected by adding either of the ECB blends to the ACB blend, or by the addition of 50% 14:OAc, a compound identified from female pheromone glands of ACB and a number of other Ostrinia species. Additional flight tunnel tests with ACB to study the comparative aspects of ECB and ACB pheromone response specificity showed that male ACB exhibited maximal levels of upwind flight and source contact with doses of pheromone (30 and 100 μg on rubber septum sources) that also elicited maximal levels in the two ECB pheromone races. The maximal level of source contact for ACB (66%) was lower than observed with the UZ race of ECB to its pheromone blend (>95%), but comparable to those for the BE race of ECB (65–70%). Male ACB also flew upwind in high proportions to a broader range of ratios of Z/E12-14:OAc (80:20 to 20:80) than was previously observed for either of the ECB races.     

Identification and bioassay of sex pheromone components of carob moth,Ectomyelois ceratoniae (Zeller)

Three sex pheromone components of the carob moth were isolated and identified from the extract of female pheromone glands, using a variety of techniques including coupled gas chromatographic-electroantennographic recordings, coupled gas chromatographic-mass spectrometric analysis, microozonolysis, electroantennographic assays of monounsaturated standards, wind-tunnel bioassays, and field trials. The major component was identified as (Z,E)-9,11,13-tetradecatrienal, a novel lepidopterous pheromone component structure. Two minor components, either one of which improves the upwind flight response of males when blended with the major component, were identified as (Z,E)-9,11-tetradecadienal, and (Z)-9-tetra-decenal.     

Pheromone-mediated responses of male cabbage looper moths,Trichoplusia ni,following various exposures to sex pheromone or (Z)-7-dodecenol

Prolonged preexposure (three days) of maleTrichoplusia ni to its six-component sex pheromone blend or its major pheromone component, (Z)-7-dodecenyl acetate, reduced subsequent upwind flight responses to a pheromone source. Preexposure to (Z)-7-dodecenol increased upwind flight responses to a pheromone source combined with (Z)-7-dodecenol. The impact of long-term preexposures was moderate when compared to the more immediate effects of background noise. When (Z)-7-dodecenyl acetate was presented as background noise, all maleT. ni failed to respond to a plume of the full pheromone blend. However, most moths succeeded in locking on to the pheromone plume and contacting the pheromone source in the presence of the five minor pheromone components as background noise. When (Z)-7-dodecenol was released as background noise the response rate to a pheromone source containing (Z)-7-dodecenol was increased dramatically. This indicates that males became adapted to (Z)-7-dodecenol while responding to the pheromone source. The results of this study indicate that both long-term preexposure treatments and immediate exposure to background noise can limit the ability of maleT. ni to respond to sex pheromone sources.     

European corn borer sex pheromone

The biological activity of analogs of the pheromone components of the European corn borer,Ostrinia nubilalis, (Z)- and (E)-11-tetradecen1-ol acetate, in which modifications were made in the terminal alkyl portion were studied in the three pheromonal types of the insect. European corn borer males respond to pheromonal stimuli at three levels of behavioral activity, i.e., short-range sexual stimulation, activation in the flight tunnel, and response in the field. Structural requirements for elicitation of response at these levels were found to be increasingly restrictive, respectively. Flighttunnel activity was induced only by compounds that had a total chain length of 13 or 14 carbons and in which branching at carbon 13 was limited to one methyl group or a cyclopropyl group. Three new analogs were active in the flight tunnel, viz., (E and (Z)-13-methyl-11-tetradecen-1-ol acetate and (Z)-12-cyclopropyl-11-dodecen-1-ol acetate. The cyclopropyl analog was the most active analog against theZZ type of the European corn borer. TheE isomer, however, was pheromonally inactive in theEE type and was shown to be a pheromone antagonist. This dissimilarity is most likely due to differences in structure of the receptors in the European corn borer strains. Analogs that were biologically active against the European corn borer were tested against the redbanded leafroller,Argyrotaenia velutinana, which also uses (Z)- and (E)-11-tetradecen-1-ol acetate as part of its pheromone. Results showed that the redbanded leafroller pheromone acceptor system is different from that of the European com borer; marginal behavioral response was elicited by only one of the new analogs. Thus, although both species use 11-tetradecen-1-ol acetate isomers as their pheromone, the mechanisms by which they are perceived are different.Mention of a commercial product does not constitute endorsement of that product by USDA.     

Courtship Behavior in Relation to the Female Sex Pheromone in the Parasitoid, <Emphasis Type="Italic">Aphidius ervi</Emphasis> (Hymenoptera: Braconidae)

Mating in the aphid parasitoid, Aphidius ervi, is mediated by sex pheromones. Virgin females produce pheromones that stimulate both upwind flight and elicit close-range courtship behavior by males. Field studies and laboratory bioassays demonstrated that time of day and adult age affect both the emission of, and receptivity to, the sex pheromones. In contrast, mating affected female pheromone production, but not male responsiveness.     

Altered Olfactory Receptor Neuron Responsiveness Is Correlated with a Shift in Behavioral Response in an Evolved Colony of the Cabbage Looper Moth, <Emphasis Type="Italic">Trichoplusia ni</Emphasis>

There is little understanding of how sex pheromone blends might change during speciation events. For the cabbage looper, Trichoplusia ni, there is a mutant laboratory strain that has exhibited characteristics of a shift to a new pheromone blend. Mutant females produce a blend that is significantly different from wild-type females in having a much higher proportion of a minor pheromone component and lower quantity of the major component. Males in this colony have changed over the years to become more broadly tuned and fly upwind equally well to both the wild-type and mutant female pheromone blends. They also exhibit reduced overall sensitivity to pheromone, flying upwind to either blend at a lower success rate than is typical when wild-type males respond to the wild-type blend. Using single-cell recordings, we examined the olfactory receptor neurons (ORNs) of males from evolved and wild-type colonies for evidence of changes in response characteristics that might explain the above-described behavioral evolution. We found that in evolved-colony males the ORNs tuned to the major sex pheromone component exhibited a somewhat lower responsiveness to that compound than the ORNs of wild-type males. In addition, the minor pheromone component, emitted at excessively high rates by mutant females, elicited a drastically reduced ORN responsiveness in evolved-colony males compared to wild-type males. This alteration in ORN responsiveness may be responsible for allowing evolved males to tolerate the excessive amounts of the minor pheromone component in the mutant female blend, which would normally antagonize the upwind flight of unevolved males. Thus, peripheral olfactory alterations have occurred in T. ni males that are correlated with the evolution of the more broadly tuned, but less sensitive, behavioral response profile.     

Sex pheromone of oriental beetle,Exomala orientalis: Identification and field evaluation

A gas chromatograph coupled with a behavioral bioassay was used to identify two sex pheromone components, 7-(Z)- and 7-(E)-tetradecen-2-one of the Oriental beetle (OB),Exomala orientalis. Field experiments showed that the blend of the two isomers (Z:E, 7:1) was not significantly more attractive than theZ component alone. The best performance of traps baited with the synthetic sex pheromone was achieved when they were set with the pheromone device at 30 cm above the ground. Catches in traps baited with 1 and 10 mg were not significantly different, but they were higher (2.9-fold) than captures in traps loaded with 0.1 mg of the pheromone. Further investigations by GC-EAD revealed the presence of a possible minor component, but the small amount of material prevented its identification. 2-(E)-Nonenol, with the same retention time as the natural product, did not affect the attractancy of the synthetic sex pheromone. GC-EAD screening of previously identified sex pheromones of scarab beetles showed that male antennae of the Oriental beetle responded to japonilure, but it showed neither synergism nor inhibition to the OB sex pheromone.     

Roles of minor components in pheromone-mediated behavior of western spruce budworm male moths

The behavior of male western spruce budworm moths,Choristoneura occidentalis Freeman, was observed in a flight tunnel in response to virgin females and synthetic sex pheromone components, alone and in blends. Pheromone blends were also compared in the field using sticky trap bioassays. Pheromones were incorporated into small rods of polyvinyl chloride. The blend of 928 (E/Z)-11-tetradecenal-8911 (E/Z)-11-tetradecenyl acetate-8515 (E/Z)-11-tetradecenol (AldAcOH) that approximated that released from a virgin female moth elicited levels of response similar to those elicited by the female. This blend induced a significantly greater percentage of moths to fly upwind and land at the lure than did the Ald lure. In contrast to the flight-tunnel bioassays, the numbers of moths caught in Ald-baited sticky traps in the field were not significantly increased by the addition of Ac and OH lures. The net upwind groundspeed of flight in response to the 0.05% Ald lure was lower than that in response to the virgin females and was significantly increased by the addition of Ac + OH lures in two of three bioassays. The flight-tunnel bioassays support the hypothesis that the natural blend of major (Ald) and minor (Ac + OH) components stimulates the precopulatory behavior of western spruce budworm male moths at long range (> 1 m downwind) as well as at close range.     

Wing fanning as a measure of pheromone response in the male pink bollworm,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

A still-air, wing fanning bioassay measured male pheromone response in the pink bollworm moth,Pectinophora gossypiella (Saunders). As pheromone concentration was increased, the duration of wing fanning increased while its latency decreased. Response duration was longest for the natural pheromone blend [44:56 (Z,E)- and (Z,Z)-7,11-hexadecadienyl acetates], although responses to 38% and 50%Z,E blends were not significantly briefer. Preexposure to pheromone had no effect on wing fanning in males retested after 24 hr. Wing fanning was highly correlated with upwind flight and other responses observed in a wind tunnel. Wing fanning duration provides a continuous measure of pheromone response and allows a large number of males to be tested in a short time; these two characteristics of the wingfanning assay are helpful for genetic analyses of male response.     

Effect of sex-pheromone concentration on behavior of three strains of western spruce budworm male moths

The responses of male western spruce budworm moths,Choristoneura occidentalis Freeman, to a range of concentrations of the major sex pheromone, 928 (E/Z)-11-tetradecenal (Ald), in polyvinyl chloride lures, were observed using the electroantennogram technique, a flight tunnel, and field-trapping bioassays. The responses to virgin female moths were also observed in the flight tunnel and field bioassays. The moths were from three strains: a nondiapausing laboratory colony; field-collected wild budworm; and laboratory-wild crosses. The mean peak amplitude of antennal response and the time required for the electroantennogram signal to return to the baseline after stimulation (lag) increased with Ald concentration in both laboratory and wild moths. However, at Ald concentrations of 0.005% and greater, the lag period of the wild male's antennae was significantly shorter than that of the laboratory male's. The mean number of moths caught in the field in delta sticky traps increased with Ald concentration, but the number of moths caught per trap was not significantly different between concentrations of 0.005 % and 0.5 %. The threshold concentration required to elicit upwind flight in the flight tunnel was between 0.0005 and 0.005% Ald; peak response occurred to 0.05 % Ald but was not significantly different from that to 0.005 % or 0.5% Ald. Moths from all three populations significantly reduced their net upwind groundspeed as they approached the pheromone lure. When pheromone concentration was increased, the net upwind groundspeed of laboratory and lab-wild moths, but not wild moths, was significantly reduced between 2 m and 1 m downwind from the pheromone lure. The three populations of moths differed significantly in the percentage of wing-fanning and copulatory attempts, and in the net upwind groundspeed of flight from 2 m to 1 m downwind from the lure.     

Sex pheromone of horse-chestnut leafminer Camneraria ohridella and its use in a pheromone-based monitoring system

Gas chromatography combined with electroantennographic detection (GC-EAD), electroantennography (EAG), and wind-tunnel and field experiments were used to reinvestigate the composition of Cameraria ohridella (Lepidoptera, Gracillariidae, Lithocolletinae) sex pheromone. The GC-EAD experiments showed one EAD-active area corresponding to the major pheromone component, (8E,10Z)-tetradeca-8,10-dienal. The EAG experiments proved that (9E)-tetracedecenal and stereoisomers of (8E,10Z)-tetradeca-8,10-dienal exhibited significant electrophysiological activity and could, therefore, be considered as possible minor pheromone components. However, wind-tunnel and field experiments demonstrated that none of these compounds affect the efficacy of the main pheromone component. A monitoring system based on (8E,10Z)-tetradeca-8,10-dienal was developed and used to study the flight activity of C. ohridella.     

Sex pheromone of cranberry fruitworm,Acrobasis vaccinii riley (Lepidoptera: Pyralidae)

The following compounds and (approximate ratios) were identified in sex pheromone gland extracts of femaleAcrobasis vaccinii Riley by comparison of gas chromatography-mass spectrometric traces with those of synthetic standards: (E,Z)-, (Z,E)-, (Z,Z), and (E,E)-8, 10-pentadecadien-l-ol acetates (100:1:2:12), a dodecen-l-ol acetate (8), (Z)-8-, (Z)-9-, and (E)-9-pentadecen-l-ol acetates (3:23:4), two heptadecen-l-ol acetates (4:4), tetradecyl, pentadecyl, hexadecyl, and heptadecyl acetates (3:15:10:8), dodecan-l-ol (6), tetradecan-l-ol (5), and hexadecan-l-ol (23). The amount of (E,Z)-8, 10-pentadecadien-l-ol acetate (E8,Z10–15:Ac) in the extract was about 0.5 ng/female. Electroantennographic analysis of gas chromatographic fractions of female sex pheromone gland extract showed that the fraction containingE8,Z10–15:Ac elicited the greatest response. Alone,E8,Z10–15:Ac failed to elicit upwind flight of males in flight-tunnel tests, and traps baited with it did not catch males in field experiments. WhenE8,Z10–15:Ac was combined with (E)-9-pentadecen-l-ol acetate (100:4), male upwind flight response in flight-tunnel tests was equivalent to those obtained with extract of female sex pheromone glands (synthetic, 62%; natural, 51%), but the percent of males flying upwind that contacted the source was lower (synthetic, 47%; natural, 88%). The lower percent of source contact elicited by the synthetic pheromone could be a result of the difference in isomer ratios of 8,10–15:Ac in the natural and synthetic pheromone or could indicate that the synthetic pheromone is incomplete. Traps baited with the 100:4 combination caught large numbers of males in field experiments.     

Sex pheromone of the european sunflower moth,Homoeosoma nebulellum (Den. & Schiff.) (Lepidoptera: Pyralidae)

Four components, (Z)-9-tetradecenal (8.6%), (Z,E)-9,12-tetradecadienal (4.8%), (Z)-11-hexadecenal (49.5%), and (Z)-13-octadecenal (37.1%), were identified in extracts of female pheromone glands of the European sunflower moth,Homoeosoma nebulellum (Lepidoptera: Pyralidae) using GC and GC-MS analyses. EAG and single-cell recordings of male antennal receptors gave strong evidence for (Z,E)-9,12-tetradecadienal as the antennal key compound of sex pheromone detection in this species. This result was confirmed by field trapping; removal of (Z,E)-9,12-tetradecadienal from quaternary blends completely suppressed the male catches. The synthetic blends with this compound as a major component caught five times less males than the blends reproducing the ratio found in the female extracts [5% of (Z,E)-9,12-tetradecadienal only]. The occurrence of a minor component perceived as the most biologically relevant compound is discussed.     

(3R*,5S*,6R*)-3,5-dimethyl-6-(methylethyl)-3,4,5,6-tetrahydropyran-2-one,a third sex pheromone component forMacrocentrus grandii (goidanich) (Hymenoptera: Braconidae) and evidence for its utility at eclosion

The compound (3R^*,5S^*,6R^*)-3,5-dimethyl-6-(methylethyl)-3, 4,5,6-tetrahydropyran-2-one was identified as a sex pheromone component ofM. grandii. Laboratory and field bioassays demonstrated that it elicits flight initiation, upwind anemotaxis, and casting in male wasps. The compound acts synergistically with (Z)-4-tridecenal, a previously identified sex pheromone component of femaleM. grandii, to increase male response to the aldehyde component. The source of the lactone was determined to be the mandibular glands of male and female wasps. At eclosion a majority of male-female and female-only cocoon masses released the lactone and attracted male wasps. Male-only cocoon masses were not attractive at eclosion and the lactone component was either not released or released at below-threshold concentration. Mating was observed to occur following eclosion in laboratory and field studies.     

Pheromone emission and blend percentages inEoreuma loftini determined by two methods

Calling behavior and pheromone emission by virgin femaleE. loftini moths were investigated in laboratory experiments. Calling peaked during the last three hours of the night. Three-day-old moths called more than older or younger moths and began calling earlier in the night than younger moths. Female emissions were collected in flasks without airflow and cylinders with airflow. Control tests indicated that the pheromone components (Z)-11-hexadecenyl acetate (HDA) and (Z)-13-octadecenylacetate (ODA) were 69 and 54% adsorbed on moths, respectively, and the component (Z)-13-octadecenal (ODL) was 92–99% adsorbed depending on its concentration, when put into flasks with noncalling females for 4 hr. Pheromone exposed to moths for less than 4 hr was adsorbed less. After correction for adsorption, the pheromone blend from females calling in flasks was 9:42:49% of HDA/ODL/ODA with an overall emission rate of 58 ng/female/4 hr. Three-day-old females emitted more pheromone than 0- to 2- or 4- to 5-day-old moths, in flasks. Little or no pheromone put into cylinders either downwind or upwind from a male moth was adsorbed by the moth. The pheromone blends from females calling in cylinders, corrected using downwind and upwind control test results, respectively, were 15:35:50 and 13:40:48% of HDA/ODL/ODA with overall emission rates of 32 and 35 ng/female/night.Lepidoptera: Pyralidae.