Shin-Ichi Inomata

Lepidopteran sex pheromones.

As a consequence of the diversity of Lepidoptera, including 150,000 described species, interesting species-specific sex pheromone systems are exhibited in this insect group. The quite varied pheromones, which have been identified from female moths of nearly 530 species from around the world, are classified into groups of Type I (75%), Type II (15%), and miscellaneous (10%), according to their chemical structures. Additionally, many pheromones produced by male moths and butterflies have been known. While new sex pheromones from about 70 lepidopteran species have been reported in the last five years utilizing GC-EAD, GC-MS, LC, and NMR, our information about the pheromones is still rudimentary, and these kinds of semiochemicals remain an exciting research target for natural product chemistry. In addition to the overview of their chemical structures, this chapter deals with current methods for their identification. Furthermore, an actual application of the synthetic pheromones for pest control is briefly introduced.

Mating Communication Systems of Four Plusiinae Species Distributed in Japan: Identification of the Sex Pheromones and Field Evaluation

The sex pheromones of four Plusiinae species in the family Noctuidae, Ctenoplusia albostriata (CA), Macdunnoughia purissima (MP), Syngrapha ain (SA), and Diachrysia stenochrysis (DS) were identified by GC-EAD and GC-MS analyses. These were subsequently evaluated by a series of field trials in different ecological habitats. CA females produced (Z)-5-decenyl acetate (I), (Z)-7-dodecenyl acetate (II), and (Z)-7-dodecen-1-ol (III) in a ratio of 2:100:13. While the antennae of CA males responded to all three components, neither I nor III was essential to capture males. The MP females produced II, III, and (Z)-5-dodecenyl acetate (IV) in a ratio of 100:80:20, and this blend captured the most MP males. Compounds II and III were also identified from SA females, and mixtures ranging from 4:1 to 2:3 were equally attractive to males. DS females only produced one active compound, (Z)-7-decenyl acetate (V), and DS is the first Plusiinae species identified as using only the ω3-compound and none of ω5-compounds, such as II and III, which are common components of Plusiinae pheromones. Using previously published chemical and biosynthetic data, together with the finding from this study, we propose a classification of the Plusiinae sex pheromones.

Biosynthetic pathway for production of a conjugated dienyl sex pheromone of a Plusiinae moth, Thysanoplusia intermixta

Virgin females of Thysanoplusia intermixta (Lepidoptera; Noctuidae; Plusiinae) produce (5E,7Z)-5,7-dodecadienyl acetate as a main sex pheromone component. GC-MS analysis of the pheromone glands, which were treated with deuterated hexadecanoic, (Z)-11-hexadecenoic, and (Z)-7-dodecenoic acids, showed incorporation of the label into the dienyl component. Their incorporation rates confirmed that its biosynthesis proceeds in the following order: Delta11-desaturation of a C(16) acyl intermediate, chain shortening to a C(12) compound by beta-oxidation, Delta5-desaturation to produce a 5,7-dienyl system, reduction of the acyl group, and acetylation. These deuterated precursors also converted into a minor pheromone component, (Z)-7-docecenyl acetate, which might be prepared by the same pathway except for the step of Delta5-desaturation. While deuterium incorporation into the dienyl acetate was not observed in the extracts treated with other labeled dodecenoic acids with (E)-5-, (Z)-6-, and (E)-7-double bonds, the corresponding dodecenyl acetates were produced. This result showed low substrate specificity of the enzymes for reduction and acetylation. Labeled (Z)-10-hexadecenoic acid was not converted into a dodecenyl acetate, indicating the high substrate specificity of the enzyme for beta-oxidation.

Identification of sex pheromones of Anadevidia peponis and Macdunnoughia confusa and field tests of their role in reproductive isolation of closely related plusiinae moths.

Anadevidia peponis and Macdunnoughia confusa are defoliators of plants in the family Cucurbitaceae and Compositae, respectively, in Japan. GC-MS analyses of crude pheromone gland extracts treated with or without dimethyl disulfide indicated that females of A. peponis produced six monoene acetates and two monoene alcohols and that M. confusa females produced five monoene acetates. These components include (Z)-7-dodecenyl acetate as a major common constituent and three other acetates as minor common constituents. The minor constituents are quite different in blend composition. In addition, with (Z)-7-dodecenyl acetate, an indispensable component for male attraction is (Z)-5-decenyl acetate for A. peponis and (Z)-9-tetradecenyl acetate is essential for M. confusa. Field tests with synthetic lures showed synergistic effects of some other minor components and male attraction of three additional Plusiinae species, Macdunnoughia purissima, Ctenoplusia albostriata, and Chrysodeixis eriosoma, suggesting their reproductive isolation is based in part on pheromonal communication.

Sex pheromone of the persimmon fruit moth, Stathmopoda masinissa: Identification and laboratory bioassay of (4E, 6Z)-4,6-hexadecadien-1-ol derivatives

Three electroantennogram (EAG)-active components were detected by gas chromatography coupled to an electroantennographic detector (GC–EAD) analysis of a hexane extract of the pheromone glands of the persimmon fruit moth, Stathmopoda masinissa. These compounds were identified as (4E,6Z)-4,6-hexadecadienal (E4,Z6-16:Ald) and the corresponding acetate (E4,Z6-16: OAc) and alcohol (E4,Z6-16:OH) by mass spectral, GC retention time (RT), and microchemical test data. The characteristic base peak of the aldehyde at m/z 84 provided a crucial piece of information suggesting the possibility of a 4,6-diene structure. The (4E,6Z)-isomer elicited the strongest EAG responses among the four geometrical isomers of each synthetic 4,6-hexadecadienyl compound. In a laboratory bioassay, only E4,Z6-16:OAc elicited male moth behavioral activity significantly different from the control; the activity of the acetate was not affected by addition of the aldehyde and alcohol. A preliminary field trial confirmed that E4,Z6-16:OAc as a single component attracted male moths. The possible roles of E4,Z6-16:Ald and E4,Z6-16:OH as components of lures for field use remain to be determined.

Sex Pheromones of Five Olethreutine Species (Lepidoptera: Tortricidae) Associated with the Seedlings and Fruits of Mangrove Plants in the Ryukyu Islands, Japan: Identification and Field Evaluation

The sex pheromones of three Cryptophlebia, one Centroxena, and one Eucosma species (Lepidoptera: Olethreutinae) inhabiting mangroves in the Ryukyu Islands, Japan, were studied with coupled gas chromatography-electroantennographic detection, and GC-mass spectrometry (GC-MS). The larvae of each Cryptophlebia species are specifically associated with viviparous seedlings from one of three mangrove Rhizophoraceae plants. Whereas three EAG-active alcohol components, (Z)-8-dodecen-1-ol, (E)-8-dodecen-1-ol, and dodecan-1-ol, in a ratio of 100:12:4, were identified from the pheromone gland extract of female of C. horii (host: Bruguiera gymnorrhiza), two other sibling species produced the corresponding acetates, i.e., (Z)-8-dodecenyl acetate, (E)-8-dodecenyl acetate, and dodecyl acetate, in a 100:2:3 ratio from Cryptophlebia palustris (host: Rhizophora stylosa in Iriomote-jima Island) and in a 100:7:13 ratio from C. amamiana (host: Kandelia candel in Amami-oshima Island). The double bond positions of the monounsaturated components were confirmed by GC-MS analyses of their adducts with dimethyl disulfide. On the other hand, the larvae of Centroxena sp. feed on fruits of Sonneratia alba, another mangrove plant in the Sonneratiaceae, and the extract of the female pheromone glands contained (8E,10E)-dodecadienyl acetate and dodecyl acetate in a ratio of 100:5. The double bond position of the diunsaturated compound was confirmed by GC-MS analysis of its adduct with 4-methyl-1,2,4-triazoline-3,5-dione. (E)-9-Dodecenyl acetate was exclusively identified in the pheromone gland extract of Eucosma coniogramma females reared from seedlings of B. gymnorrhiza. Although the roles of minor components have not been revealed by field tests, synthetic lures baited with the main pheromone component of each species successfully attracted the target males, confirming that the sex pheromone is one of the most important factors for their reproductive isolation.

SEX ATTRACTANTS FOR MOTHS OF VIETNAM: FIELD ATTRACTION BY SYNTHETIC LURES BAITED WITH KNOWN LEPIDOPTERAN PHEROMONES

Screening tests of synthetic lepidopteran sex pheromones were carried out at orchards in the Mekong Delta over an approximately two-year period starting from December 1998. Monoenyl acetates with a C10–C14 chain attracted six species distributed mainly in Southeast Asia: Adoxophyes privatana, Archips atrolucens, and Meridemis furtiva in the Tortricidae family, and Argyrogramma signata, Spodoptera pectinicornis, and Zonoplusia ochreata in the Noctuidae family. These were in addition to three other noctuid species that had been attracted during previous field examinations within a temperate zone. Furthermore, male moths of three species belonging to the Cosmopterigidae, Gelechiidae, or Batrachedridae family were also caught by traps baited with acetates. Trienes with a C18–C21 chain and their monoepoxides, which are stereotypes of pheromones secreted by females in the Geometridae family, failed to attract any geometrid male, but attracted three Noctuidae species and four Arctiidae species.

Sex Pheromones of Two Melittini Species, Macroscelesia Japona and M. Longipes: Identification and Field Attraction

Two Melittini species, Macroscelesia japona and M. longipes (Lepidoptera: Sesiidae), are native to Japan, but occupy different localities as their host plants seldom grow together. The contents of the sex pheromone gland of adult females of both species, obtained after rearing larvae collected from the field, were investigated by gas chromatograph-electroantennogram detection (GC-EAD) and gas chromatograph-mass spectrometry (GC-MS) analyses. Two GC-EAD-active components were found in a crude extract of M. japona female pheromone gland, and identified as (2E,13Z)-2,13-octadecadien-1-ol (E2,Z13-18:OH) and (2E,13Z)-2,13-octadecadienal (E2,Z13-18:Ald). The average ratio of these two components was about 1:10. In the field, M. japona males were attracted to traps baited with E2,Z13-18:Ald alone, but the strongest attraction was observed with a 1:100 mixture of E2,Z13-18:OH and E2,Z13-18:Ald. The same two components were found in extracts of M. longipes females, but in a markedly different ratio. Male M. longipes were attracted most strongly to lures containing a 20:1 mixture of E2,Z13-18:OH and E2,Z13-18:Ald, although some males were also attracted to lures with E2,Z13-18:OH alone. Although the two species do not generally occur in sympatry, our data indicate that, in the event of overlap, cross attraction of the two species is unlikely.

Regulation of Sex Pheromone Biosynthesis in Three Plusiinae Moths: Macdunnoughia confusa, Anadevidia peponis, and Chrysodeixis eriosoma

Virgin females of M. confusa, A. peponis, and C. eriosoma secrete (Z)-7-dodecenyl acetate as a common main pheromone component. Their pheromone titers decreased after decapitation, and increased in the decapitated females after injection of a synthetic hormone, pheromone biosynthetic activating neuropeptide (PBAN) of Bombyx mori. In addition, an extract of brain-subesophageal ganglion complexes of each Plusiinae species activated pheromone biosynthesis in decapitated females of not only the corresponding species, but also that of Mamestra brassicae. These results indicate that pheromone biosynthesis of the three Plusiinae species is also controlled by a PBAN-like substance. However, the Plusiinae females exceptionally contained remarkable amounts of the pheromone even 1 day after decapitation. Since it has been reported that pheromones completely disappear at least 1 day after decapitation in females of many other lepdidoptran species including B. mori and M. brassicae, a different mechanism is likely regarding the regulation of the studied Plusiinae pheromone biosynthesis. Furthermore, an incorporation experiment with a labeled pheromone precursor, D9-(Z)-7-dodecenoic acid, showed that moderate biosynthesis still proceeded in the pheromone glands of M. confusa females 1 day after decapitation, providing an evidence why complete disappearance of the pheromone was not observed in the females which otherwise lacked a source of the pheromonotropic neuropeptide.

Sex Pheromones of Thysanoplusia intermixta and T. orichalcea: Identification and Field Tests

Thysanoplusia intermixta, which inhabits the temperate zone in Japan, is a defoliator of plants in the family Compositae, Apiaceae, and others. By GC-MS analysis, (Z)-7-dodecenyl acetate, (Z)-7-dodecen-l-ol, (5E, 7Z)-5,7-dodecadienyl acetate and (5E, 7Z)-5,7-dodecadien-l-ol were identified from a pheromone gland extract of the virgin females in a ratio of 18:3:100:13. A lure baited only with the major diene acetate could attract male moths of T. intermixta in the field. Other minor components had a synergistic effect on the attraction of the diene acetate. The same four components were included in a very different ratio of 100:6:11:1 in the gland extract of Thysanoplusia orichalcea, a closely related subtropical species. The monoene and diene acetates are essential for field attraction, and a 100:11 mixture is an optimum lure for T. orichalcea males. However, this mixture, including the diene acetate as a minor component, captured very few T. intermixta males, suggesting the possibility that these two Thysanoplusia species are reproductively isolated from each other by pheromonal communication.