Interpopulational variation in emitted pheromone blend of cabbage looper moth,Trichoplusia ni

Female cabbage looper moths,Trichoplusia ni, from laboratory colonies initiated from three locations across the United States emitted similar quantities and blend ratios of the six known pheromone components. In contrast, females from a long-established laboratory colony emitted a greater proportion of four of the five minor components relative to the major component, (Z)-7-dodecenyl acetate; only the relative proportion of 11-dodecenyl acetate was similar in all of the populations sampled. Females from this population emitted (Z)-7-dodecenyl acetate at a rate similar to that from females from field-collected colonies. Within each population there were highly significant correlations among the quantities of pheromone components of similar molecular weights. Correlations between components of different molecular weights were not as great, but often were significant. Similarities of blend ratios among field populations may indicate that the chemical signal in this species is conservative. The difference of the blend ratios in our laboratory population from the other populations may indicate a decrease in the intensity of selection pressure that usually would maintain these values.     

A mutation in pheromonal communication system of cabbage looper moth,Trichoplusia ni

A mutation that results in a dramatic change in the relative proportions of the pheromone components produced by female cabbage looper moths has been found. The most notable changes involve reduction in the emission rate of the major component [(Z)-7-dodecenyl acetate], near absence of a component [(Z)-5-dodecenyl acetate] that is normally present at about 20% of the major component, and a remarkable ca. 20-fold increase in a trace component [(Z)-9-tetradecenyl acetate]. In spite of the multiplicity of changes in the pheromone blend, a genetic analysis indicates that the condition is controlled by a single autosomal gene. These mutants are ineffective in attracting conspecifics, but do attract another distantly related noctuid moth. These results suggest that the evolutionary process that leads to distinct chemical signals in sibling species may include single gene mutations that lead to major changes in the species-specific blend.     

Dodecyl acetate,a second pheromone component of the cabbage looper moth,Trichoplusia ni

Dodecyl acetate was identified as a second component of the sex pheromone ofTrichoplusia ni (Hübner). Dodecyl acetate comprised 9.6% by weight of the total pheromone [(Z)-7-dodecenyl acetate plus dodecyl acetate] extracted from glands and 7.3% by weight of the total pheromone evaporated from the surfaces of glands. Dodecyl acetate appears to function as a short-range pheromone component. Evaporation at female release rates of a 1090 mixture of dodecyl acetate and (Z)-7-dodecenyl acetate in the field caused a significantly greater percentage of males to land on the pheromone source, increased significantly the time they spent on the source, but decreased significantly the time they spent searching for the source when within 50 cm, as compared to (Z)-7-dodecenyl acetate alone.Lepidoptera: Noctuidae.     

Genetic aspects of interpopulational differences in pheromone blend of cabbage looper moth,Trichoplusia ni

The genetic basis of interpopulational differences in the pheromone blend emitted by the cabbage looper moth,Trichoplusia ni (Hübner), was examined by crossing individuals from a field-derived population (P₁) with individuals from a long-maintained laboratory colony (P₂). These colonies differed in the emission rate and relative proportions of four of the five known minor pheromone components, but not in the emission rate of the major component, (Z)-7-dodecenyl acetate (Z7-12Ac). These differences in pheromone blend were quantitatively small but biologically significant, because in the field, males responded preferentially to traps baited with a pheromone blend that is similar to that emitted by P₁ females relative to a blend similar to that emitted by P₂ females. In initial crosses, variation in the quantity and quality of pheromone blends among families of P₁, P₂, and F₁ hybrid females was examined. In F₁ females the relative proportions (quantity relative to the major component) of (Z)-5-dodecenyl acetate (Z5-12Ac) and (Z)-7-tetradecenyl acetate (Z7-14Ac) were intermediate to parental lines. In a second more extensive set of crosses, analyses included P₁, P₂, F₁, F₂, and selected backcrosses. The relative proportion of Z5-12Ac, Z7-14Ac, and Z9-14Ac emitted by F₁ females were intermediate to parental lines. The frequency distributions of relative proportions of these components emitted by females were not consistent with those expected under a single autosomal or sex-linked gene hypothesis, suggesting that more than one gene is involved in the quantitative differences in the pheromone blend.     

Filamentous nature of pheromone plumes protects integrity of signal from background chemical noise in cabbage looper moth,Trichoplusia ni

(Z)-7-Dodecenol failed to interrupt pheromone-mediated anemotactic responses by male cabbage looper moths,Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) in a wind tunnel when released 5 cm crosswind on both sides of the pheromone source or 10 cm upwind of the source to create an overlapping plume downwind. Significant inhibitory effects of (Z)-7-dodecenol were observed when released with the six-component pheromone blend from the same septum or abutting septa. These results indicate that (Z)-7-dodecenol needs to be received simultaneously with the pheromone blend to inhibit the anemotactic responses of males to the sex pheromone. We suggest that this feature and the filamentous nature of pheromone plumes render pheromone signals relatively protected from background chemical noise that may originate from pheromone plumes of other insect species. Unless filaments from a pheromone signal and an inhibitor arrive simultaneously, the integrity of the signal is maintained.     

Identification of new sex pheromone components inTrichoplusia ni,predicted from biosynthetic precursors

In addition to the previously identified components (Z)-7-dodecenyl acetate and dodecyl acetate, sex pheromone glands ofTrichoplusia ni release (Z)-5-dodecenyl acetate, 11-dodecenyl acetate, (Z)-7-tetradecenyl acetate, and (Z)-9-tetradecenyl acetate. Bioassays in a flight tunnel showed that a synthetic blend of these six compounds elicited complete flights to the source from 95% of the males tested and elicited hairpenciling responses at the end of the flights from 88% of the males tested. This blend was not significantly different from intact pheromone glands, which elicited complete flights to the source from 98% of the males tested and hairpenciling responses from 91% of the males tested. In contrast, the previously identified two-component blend elicited significantly fewer complete flights to the source (33%) and did not elicit hairpenciling responses from any of the males tested. The search for additional sex pheromone components was prompted by our previous identification of unusual fatty acyl moieties in the gland that seemed to be possible biosynthetic intermediates.     

Comparison of electroantennograms from female and male cabbage looper moths (Trichoplusia ni) of different ages and for various pheromone concentrations

The electroantennogram (EAG) responses of both male and femaleTrichoplusia ni to two components of the female-released sex pheromone were determined over a range of concentrations of chemical and age of insect. The EAG was at a peak at a dose of 100 g for both dodecyl acetate and (Z)-7-dodecenyl acetate (Z7–12OAc) for both sexes. The EAG responses varied with age of the insect. Responsiveness to both components was at a maximum at three days postemergence for males followed by a fairly rapid senescence, and for females it peaked at three days followed by a rapid senescence forZ7–12OAc but not for dodcecyl acetate.     

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.     

Identification of sex pheromone components from pheromone gland volatiles of the tomato looper,Plusia chalcites (Esp.)

The sex pheromone glands ofPlusia chalcites release, dodecyl acetate, (Z)-7-dodecenyl acetate, (Z)-9-dodecenyl acetate, 11-dodecenyl acetate, (Z)-8-tridecenyl acetate, and (Z)-9-tetradecenyl acetate. A combination of capillary GC, GC-MS, and dimethyl disulfide derivatization enabled a rigorous identification of all these compounds, some of which were previously found in gland extracts. Bioassays in a flight tunnel showed that a ternary blend of (Z)-7-dodecenyl acetate, (Z)-9-dodecenyl acetate, and (Z)-9-tetradecenyl acetate elicited directed flights from 85 to 100% of the males tested and elicited copulation attempts, at the end of the flights, from 44 to 74% of the males tested. This blend was equal in activity to the natural gland extract. Addition of the other acetates had only a slight influence on the activity of this mixture. Substitution of either (Z)-9-dodecenyl acetate or (Z)-9-tetradecenyl acetate in this blend by 11-dodecenyl acetate gave two ternary mixtures which also elicited high levels of courtship activity, almost as high as that of the original blend. Addition of (Z)-7-dodecenyl alcohol inhibited almost totally the flight activity of males.Lepidoptera: Noctuidae.Contribution from the Agricultural Research Organization (ARO) No. 1701-E, 1986 series.     

Identification of unique pheromone components for soybean looper mothPseudoplusia includens

Analysis of sex pheromone glands from individual female soybean looper moths showed that in addition to the previously identified main component (Z)-7-dodecenyl acetate, the compounds dodecyl acetate, 11-dodecenyl acetate, (Z)-7-dodecenyl propionate, and (Z)-7-dodecenyl butanoate were also produced. Two of the components, 12OAc and 11–12OAc, were not detected in a single analysis of female effluvium. Flight-tunnel tests showed that the five-component and three-component blends were equal to each other and to a female extract (> 80% source contacts) and that the mixtures were superior toZ7–12OAc alone. Field tests indicated that the five-component blend was significantly more attractive thanZ7–12OAc alone at a dosage of 1 mg, but that the blend was only slightly better at 3 mg.     

Individual variation in the pheromone of the turnip moth,Agrotis segetum

Female turnip moths (Agrotis segetum) from a laboratory culture inbred for more than 30 generations, and the offspring (first and third generation) from field-collected insects were analyzed individually for acetates and alcohols in the pheromone gland. Quantitative analysis of individual components was performed at the subnanogram level by gas chromatographymass spectrometry (selected ion monitoring). The titer of the pheromone, i.e., the sum of the homologous acetates (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-tetradecenyl acetate was 2.0 ± 0.3 ng in the laboratory culture and 3.2 ± 0.6 ng in the wild strain. There was no correlation between pheromone titer and female weight. The relative proportion of the pheromone components varied substantially between individuals, but there was no statistically significant difference between the two populations. The percentages of the respective compounds (¯X ± coefficient of variation) were 14.8 ± 127% for Z5-10:OAc, 55.6 ± 32% for Z7-12:OAc, and 29.6 ± 59% forZ9-14:OAc. The pheromone composition varied more in the wild strain than in the laboratory culture. The significance of the pheromone variation to the attraction of males was tested in a field experiment. The ratio of males trapped by the most attractive blend versus the least attractive one was 2.2.Schiff., Lepidoptera: Noctuidae.This study was made within the Swedish project Odour Signals for Control of Pest Insects.     

Sex pheromone of the chokecherry leafroller moth,Sparganothis directana

(E)-9,11-Dodecadienyl acetate and (Z)-9,11-dodecadienyl acetate in conjunction with (E)-11-tetradecenyl acetate and (Z)-11-tetradecenyl acetate were found to comprise the sex pheromone ofSparganothis directana, based on chemical analysis, electroantennogram tests, and field trapping. (E)-9-Dodecenyl acetate and (Z)-9-dodecenyl acetate were also found in gland extracts but did not influence trap catches. The relative amounts of these compounds in the gland were 3521928 106, in the order named. Only (E)-9,1 1-dodecadienyl acetate, (E)-11-tetradecenyl acetate, and (Z)-11-tetradecenyl acetate were required for attraction of males to traps, dispensed in the relative amounts 501238, respectively.Lepidoptera: Tortricidae.Supported by National Science Foundation grant PCM 78-13241.     

Identification of female sex pheromone components of rice looper,Plusia festucae (L.), (Lepidoptera: Noctuidae)

The rice looper,Plusia festucae, is a defoliator of the rice plant. Chromatographic behavior, chemical reactions, and GC-MS analyses of the female sex pheromone revealed that the main component was (Z)-5-dodecenyl acetate (Z5–12: OAc, component I). The GC-MS analysis also indicated that the pheromone gland extract included another three monounsaturated components, (Z)-5-dodecen-l-ol (Z5–12: OH, component II), (Z)-7-tetradecenyl acetate (Z7–14: OAc, component III), and (Z)-7-tetradecen-l-ol (Z7–14: OH, component IV) in the following ratio: I:II:III:IV=100:6:15:1. In a paddy field, the mixture of synthetic I, II, and III in a ratio of 100:6:15 showed stronger attractancy than the virgin female, while the role of IV was unknown.     

Redundancy in a chemical signal: Behavioral responses of maleTrichoplusia ni to a 6-Component sex pheromone blend

The flight response of maleTrichoplusia ni was observed in a flight tunnel to a sex pheromone blend composed of six components:Z7–12Ac, 12Ac,Z5-12Ac, 11-12Ac,Z7-14Ac, and Z9-14Ac. The number of males reaching a 3000-g source of this blend was > 95%, equal to that observed to female glands and significantly greater than with the previously identified two-component blend (Z7-12Ac + 12Ac). In subtraction tests, all five-component blends, with the exception of the blend lacking the primary componentZ7-12Ac, and several four-component blends elicited similar peak levels of upwind flight, source contacts, and hairpencil displays to that observed with the six-component blend. We characterize the substitution of certain minor components for one another as a form of redundancy in the chemical signal and suggest that it contributes to response specificity and signal recognition in males. The results also support the concept that the full blend of components acts as a unit to influence male behavior at all phases of the response. Individual minor components were not responsible for eliciting specific behaviors in the sequence.     

Pheromone hydrolysis by cuticular and interior esterases of the antennae,legs, and wings of the cabbage looper moth,Trichoplusia ni (Hübner)

Examination was made of the hydrolytic activities of esterases obtained from the antennae, legs, and wings of 3-day-old cabbage looper moths,Trichoplusia ni (Hübner), by elution and by homogenation of those appendages. Pheromone hydrolysis in 1-min assays was monitored by use of tritium-labeled (Z)-7-dodecen-1-ol acetate and thin-layer chromatography to separate the reaction products. Listed according to the activities of the esterases obtained by homogenation, the organs were antennae > legs > wings. In contrast, the order according to the activities of the eluted esterases was wings > legs > antennae. Also, the eluted enzymes were less active than the esterases obtained by homogenization. The relatively high pheromone-hydrolyzing activity present in homogenized antennae suggests that the esterases originated inside the antennae and lends support to the hypothesis proposed in earlier investigations that pheromone-inactivating enzymes may play an important role in the olfactory process, possibly by clearing pheromone from the vicinity of the olfactory receptors. The esterases detected on the cuticle, on the other hand, may function by preventing surface accumulation of pheromone. The higher measured esterase activity in homogenates of prothoracic legs than of mesothoracic or metathoracic legs suggests that the prothoracic legs, which are used to clean the antennae of debris, may function by removing and degrading pheromone from the surface of antennae.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Attraction of male turnip mothsAgrotis segetum (Lepidoptera: Noctuidae) to sex pheromone components and their mixtures at 11 sites in Europe,Asia, and Africa

Selected combinations of (Z)-5-decenyl, (Z)-7-dodecenyl, and (Z)-9-tetradecenyl acetates, the pheromone components of the turnip mothAgrotis Segetum were tested for field attractancy at six, two, and three sites in Europe, Asia, and Africa, respectively. At all of the sites in Eurasia and in northern Africa the ternary mixture of the acetates captured most males, while at the sites south of the Sahara in Africa, (Z)-5-decenyl acetate alone was responsible for attraction. Differences in male attraction among the populations studied confirm the existence of significant population variation in the pheromone ofA. segetum. Interpretation of the present results together with earlier studies suggests that this variation is more or less continuous in Eurasia and north Africa, while a clearly distinct pheromone type is present in the areas south of the Sahara desert.     

Identification of sex pheromone components of darksided cutworm,Euxoa messoria,and modification of sex attractant blend for adult males

Eleven pheromone-like compounds were identified in excised abdomen tip extracts of calling adult females of darksided cutworm,Euxoa messoria (Harris). The essential pheromone components were (Z)-7- and (Z)-11-hexadecenyl acetates in a ratio of 140, which agreed with an attractant blend developed empirically by field testing the attractancies of synthetic blends. The pheromone component, (Z)-11-hexadecenol, improved the attraction of darksided cutworm males whereas the components (Z)-9-tetradecenyl acetate and (Z)-7-dodecenyl acetate inhibited their attraction. The other pheromone-like compounds identified in the female extracts had no obvious effect on the attraction of darksided cutworm males. Three compounds that functioned as parapheromones when substituted for (Z)-7-hexadecenyl acetate in the two-component blend were (Z)-7-pentadecenyl, (Z)-7-tetradecenyl, and (Z)-7-tridecenyl acetates. (Z)-11-hexadecenal was not detected in the female extracts, but it had a synergistic effect on the attraction of darksided cutworm moths and inhibited the attraction of male moths of a nontarget species,Helotropha reniformis (Grote). As a trap bait for monitoring purposes, we recommend a four-component blend of (Z)-7-hexadecenyl acetate, (Z)-11-hexadecenyl acetate, (Z)-11-hexadecenol, and (Z)-11-hexadecenal at 12.5, 500, 1, and 10 g/red rubber septum dispenser containing 5 g of antioxidant 2,6-tert-butyl-4-methyl phenol. This blend is effective under field conditions for at least six weeks.     

Identification and field testing of additional components of female sex pheromone of African armyworm,Spodoptera exempta (Lepidoptera: Noctuidae)

Ovipositor washings from virgin femaleSpodoptera exempta (Walker) (Lepidoptera: Noctuidae) were analyzed by high-resolution gas chromatography (GC) linked to a male electroantennogram (EAG). GC retention times of the two major EAG responses observed were consistent with their assignment as (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate, as previously identified. However, three other EAG responses were also noted that had GC retention times consistent with (Z)-9-tetradecenal, (Z)-9-tetradecen-1-o 1, and (Z)-11-hexadecenyl acetate. The components were present in the ratio of 10051.53.54, respectively. Further analysis of the ovipositor washings by GC linked to a mass spectrometer (GC-MS) confirmed these findings and indicated the presence of a sixth component consistent with (Z)-11-tetradecenyl acetate present at 2 % of the major component. In field tests carried out in Kenya, (Z)-11-hexadecenyl acetate was the only newly identified component to enhance the catch of the original two-component mixture when presented in their natural ratio. The addition of (Z)-9-tetradecen-1-ol reduced catch, while (Z)-9-tetradecenal and (Z)-11-tetradecenyl acetate had no apparent effect.     

Behavioral responses of male turnip moths,Agrotis segetum,to sex pheromone in a flight tunnel and in the field

The response of individual male turnip mothsAgrotis segetum was observed in a sustained flight tunnel to a mixture of decyl acetate, (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-tetradecenyl acetate in proportions similar to those found in gland extracts from virgin females (0.6: 1:5:2.5). Lures containing 3–30 g (Z)-5-decenyl acetate proved to be maximally attractive, with approximately 60% of the males completing all behavioral steps from activation to copulation efforts. A 300-g dosage caused significant arrestment of upwind flight. Peak response to synthetics, however, was significantly lower than to female glands. Omitting decyl acetate from the blend did not affect the activity, while omission of any of the three monounsaturated acetates caused a dramatic decrease in response. In the field maximum trap catches were achieved with 1- to 30-g lures. The subtractive assay carried out in the field confirmed the neutrality of decyl acetate and the importance of the three monoenes. Adding 1% of (Z)-8-dodecenyl acetate (earlier reported as an inhibitor) to the four-component mixture decreased the trap catch to about 50%, and increasing the amount of (Z)-8-dodecenyl acetate to 27% decreased the activity further to about 10%. (Z)-8-Dodecenyl acetate also decreased the number of successful flights in the flight tunnel.Schiff., Lepidoptera: Noctuidae.This study was made within the Swedish project Odour Signals for Control of Pest Insects.     

Sex pheromone components of the variegated leafroller moth,Platynota flavedana

Female tip extracts of the variegated leafroller moth,Platynota flavedana (Clemens), were analyzed and found to contain a mixture of (E)-11-tetradecen-1-ol and (Z)-11-tetradecen-1-ol (91), as well as a mixture of (E)-11-tetradecenyl acetate and (Z)-11-tetradecenyl acetate (2-31). Small amounts of tetradecen-1-ol and tetradecyl acetate probably are also present. In the field, a mixture of the two alcohols (8416,EZ ratio) attracted significantly more male moths of this species than any other mixture tested. The data indicate that the acetates are probably not used as pheromone components.Lepidoptera:Tortricidae:Tortricinae.This research was supported in part by the Rockefeller Foundation and by NSF Grant No. GB-38020.