Pheromone-Based Pest Management in China: Past, Present, and Future Prospects

Variations in Mating and Reproduction in Oriental Fruit Moth Caused by Adult Physiological State in Laboratory Tests

Grapholita molesta (Busck) is a pest of rosaceous fruit plants worldwide. Due to a combination of monandry and promiscuity in G. molesta, the age and mating history of both sexes significantly affected the mating and reproductive success. In this study, the interactions of different ages (3, 5, or 7 days) and mating history (unmated or mated) in each sex on the mating selection, reproductive system, and offspring production were investigated in the laboratory. The results showed that these differences mainly occurred in young females or males, associated with unmated or mated state. Especially, the 3-day-old unmated females were preferred by the 7-day-old males but discriminated against by the 3- or 5-day-old unmated males, whereas the 3-day-old mated males were preferred by the 3-day-old mated or 7-day-old females but discriminated against by the 3- or 5-day-old unmated females. The lengths of the ovarian ducts were affected by age in the unmated females, with the greatest length being found at 7 days old. The size of testes varied with age in the unmated males, being the largest at 3 days old. At 3 days old, the testes size of the unmated males was larger than that of the mated males. The pairing of 5-day-old unmated females × 3-day-old mated males maximized the successful matings. The least productive pairing was 7-day-old unmated females × 5-day-old mated males. The pairing of 5-day-old mated males × 3-day-old mated females had the lowest number of matings and the highest number of offspring. The pairing of 3-day-old mated females × 3-day-old mated males had a high rate of mating success and the most offspring. These results revealed the different roles between females and males because of physiological states in terms of the reproductive biology in G. molesta.

Identification of sex pheromone in Macdunnoughia crassisigna Warren (Lepidoptera: Noctuidae) and field optimization of the sex attractant

BACKGROUND

Sex pheromones have proven to be a viable tool for monitoring and controlling pests and is an important part of integrated pest management (IPM). The noctuid moth Macdunnoughia crassisigna Warren poses a significant threat as a defoliator pest, impacting soybean and cruciferous vegetable production and quality in East Asia. However, a lack of comprehensive knowledge about its sexual chemical signaling hampers the development of semiochemical-based IPM approaches for M. crassisigna.

RESULTS

We first determined the mating rhythms of M. crassisigna. We then collected pheromones from the sex glands of virgin females at the mating peak and analyzed their components using gas chromatography-electroantennogram detection analysis. The results showed that three components elicited significant electrophysiological responses in male antennae. Gas chromatography-mass spectrometry analysis characterized these components as (Z)-7-dodecene acetate (Z7-12:OAc), (Z)-9-tetradecene acetate (Z9-14:OAc), and (Z)-11-hexadecen-1-ol (Z11-16:OH). Further field experiments indicated that the mixture of Z7-12:OAc and Z9-14:OAc at a ratio of 3:1 displayed significant attractivity to males, confirming its role as a putative sex pheromone of M. crassisigna. Long-term monitoring tests showed that traps baited with these pheromone lures effectively mirrored the population dynamics of M. crassisigna.

CONCLUSION

This study successfully identified and validated the sex pheromone released by female M. crassisigna and formulated potent sex lures for field-based pest monitoring. These findings enriched our understanding of chemical communication in Noctuidae and laid a foundation for developing practical monitoring and control methods against M. crassisigna. © 2023 Society of Chemical Industry.

RNAi-mediated silencing of SlitPer disrupts sex pheromone communication behavior in Spodoptera litura

BACKGROUND

The 24-h circadian rhythm is considered crucial for insect sexual communication. However, its molecular mechanisms and signaling pathways, particularly the roles of the clock gene period (Per), remain largely unclear. The sex pheromone communication behavior of Spodoptera litura displays typical circadian rhythm characteristics. Thus, it represents an excellent model for functional analyses of the clock gene Per.

RESULTS

In this study, we investigated the potential roles of SlitPer in regulating sex pheromone communication in S. litura using RNA interference, quantitative real-time polymerase chain reactions (qPCR), gas chromatography, and behavioral assays. The qPCR results showed that the expression levels of SlitPer and two desaturase genes (SlitDes5 and SlitDes11) in the siPer group differed significantly at most time points from those in the siNC group. Dynamic variation in the three major sex pheromone titers and calling behavior of S. litura females in the siPer group was disordered. In addition, the mating rates of siPer S. litura females decreased significantly by 33.33%. Oviposition by mated siPer females was substantially reduced by 84.84%.

CONCLUSION

These findings provide a fundamental basis for elucidating the molecular mechanism by which Per regulates sex pheromone communication behavior in lepidopteran species. © 2023 Society of Chemical Industry.

Dispensers for pheromonal pest control

The detrimental effects of pesticides on the environment and human health have motivated the development of alternative pest control strategies. Pheromonal pest control is one alternative strategy that is attractive because most pheromones used commercially are non-toxic. Pheromones are also effective at low concentrations, and insects are slower to develop resistance to them compared to pesticides. Pheromones can be used to control pests by attracting them towards traps, repelling them from crops, or disrupting their mating behaviour. Viability of pheromonal control strategies must be evaluated on a case-by-case basis and depends on the target species, the pheromone being used, the specific control strategy, the method of dispensing pheromone, other pest control strategies pheromones being used alongside, and many other factors. The efficacy of pheromonal control has been demonstrated in commercial applications such as the control of palm weevils using traps releasing their male aggregation pheromone. Mating disruption using female sex pheromones has also been widely applied for control of both the codling moth Cydia Pomonella and the european grapevine moth Lobesia Botrana (Bangels and Beliën, 2012; Lucchi et al., 2018). Pheromones are volatiles that both degrade quickly in the environment and can be rapidly dispersed by wind. Consequently, administering pheromones to fields requires the use of dispensers that emits pheromone continuously or intermittently. Septum dispensers, membrane dispensers and solid matrix dispensers are best suited to treating smaller areas of cropland since they need to be installed by hand, a labor-intensive process. For treating a large area with pheromones, sprayable formulations and aerosol dispensers are alternative dispensing technologies that can be employed. The characteristics of these different dispenser designs are discussed as well as the kinetics governing pheromone release. Possible areas for future work in pheromone dispenser technology include examining new integrated strategies that employ pheromones alongside other pest control techniques in unique ways. The combination of pheromonal control with physical exclusion or predator release are examples of integrated strategies that are promising but have yet to be widely commercialized. Most commercial pheromonal dispensers are also noted to be impossible or impractical to reuse, apart from aerosol devices. Creating new types of rechargeable dispenser might have some cost saving benefits and would be an interesting area for future innovation in this field.

Two Odorant-Binding Proteins Involved in the Recognition of Sex Pheromones in Spodoptera litura Larvae

Usually, the recognition of sex pheromone signals is restricted to adult moths. Here, our behavioral assay showed that fourth-instar Spodoptera litura larvae are attracted to cabbage laced with minor sex pheromones Z9,E12-tetradecadienyl acetate (Z9,E12-14:Ac) or Z9-tetradecenyl acetate (Z9-14:Ac). Seven odorant-binding proteins (OBPs) were upregulated after exposure to Z9,E12-14:Ac, and one OBP was upregulated after exposure to Z9-14:Ac. Fluorescence competitive binding assays showed that GOBP2 and OBP7 bound to sex pheromones. RNAi treatment significantly downregulated GOBP2 and OBP7 mRNA expression by 70.37 and 63.27%, respectively. The siOBP-treated larvae were not attracted to Z9,E12-14:Ac or Z9-14:Ac, and the corresponding preference indices were significantly lower than those in siGFP-treated larvae. Therefore, we concluded that GOBP2 and OBP7 are involved in the attraction of S. litura larvae to food containing Z9,E12-14:Ac and Z9-14:Ac. These results provide an important basis for exploring the olfactory mechanisms underlying sex pheromone attraction in moth larvae.

Genome-Wide Analysis of Odorant-Binding Proteins and Chemosensory Proteins in the Bean bug Riptortus pedestris

Insects have sensitive olfactory systems to interact with environment and respond to the change in host plant conditions. Key genes in the system can be potential targets for developing new and efficient pest behaviour control methods. Riptortus pedestris is an important soybean pest in East Asia and has caused serious damage to the soybean plants in Huang-Huai-Hai region of China. However, the current treatment of pests is dominated by chemical insecticides and lacks efficient sustainable prevention and control technologies. In this study, we identified 49 putative odorant-binding proteins (OBPs) (43 were new genes) and 25 chemosensory proteins (CSPs) (17 were new genes) in R. pedestris genome. These OBP and CSP genes are clustered in highly conserved groups from other hemipteran species in phylogenetic trees. Most RpedOBPs displayed antennal-biased expression. Among the 49 RpedOBPs, 33 were significantly highly expressed in the antennae, including three male-biased and nine female-biased. While many RpedCSPs were detected both in the antennae and in non-antennal tissues, only 11 RpedCSPs displayed antennal-biased expression, in which four RpedCSPs were male-biased and five RpedCSPs were female-biased. Some OBP and CSP genes showed sex-biased expression profiles. Our results not only provide a foundation for future exploration of the functions of RpedOBPs and RpedCSPs but also aid in developing environmentally friendly insecticides in the future.

Octopamine modulates insect mating and Oviposition

The neuro-mechanisms that regulate insect reproduction are not fully understood. Biogenic amines, including octopamine, are neuromodulators that have been shown to modulate insect reproduction in various ways, e.g., promote or inhibit insect mating or oviposition. In this study, we examined the role of octopamine in regulating the reproduction behaviors of a devastating underground insect pest, the dark black chafer (Holotrichia parallela). We first measured the abundance of octopamine in different neural tissues of the adult chafer pre- and post-mating, demonstrating that octopamine decreased in the abdominal ganglia of females but increased in males post-mating. We then fed the adult H. parallela with a concentration gradient of octopamine to test the effects on insect reproductive behaviors. Compared with its antagonist mianserin, octopamine at the concentration of 2 µg/mL resulted in the highest increase in males' preference for sex pheromone and females' oviposition, whereas the mianserin-treatment increased the survival rate and prolonged the lifespan of H. parallela. In addition, we did not observe significant differences in egg hatchability between octopamine and mianserin-treated H. parallela. Our results demonstrated that octopamine promotes H. parallela mating and oviposition with a clear low dosage effect, illustrated how neural substrates modulate insect behaviors, and provided insights for applying octopamine in pest management.

Structural insights into the discrepant synergistic activity of Codlemone and (Z)-8-dodecenol towards Grapholita molesta pheromones

BACKGROUND

Insect pheromone synergists have been widely used to produce potent pheromone products for environment-friendly pest control. Codlemone (Cod) and (Z)-8-dodecenol (Dod) are two major Grapholita molesta pheromone synergists, with Cod having greater synergism and affinity for G. molesta pheromone binding protein 2 (GmolPBP2). Uncovering structural information key to the different binding affinity of Cod and Dod to GmolPBP2 would gain insights into what causes their synergy activity discrepancy.

RESULTS

Binding modes of the two synergists in the binding pocket of GmolPBP2 were analyzed and compared by molecular dynamics-based approaches. Although Cod and Dod were stabilized in a similar hydrophobic pocket, their interaction details with GmolPBP2 were divergent due to the extra double bond (C10═C11) in Cod. The C10═C11 improved the hydrophobic interactions of Cod with around residues. Such hydrophobic interaction improvement was also reflected in the raised importance of Phe11 in the GmolPBP2-Cod interaction. Not only that, the increased hydrophobic forces introduced by the C10═C11 changed the CH2-OH orientation in the GmolPBP2-Cod complex, which improved the H-bond interaction. Electrostatic complementarity analysis further indicated the positive role of C10═C11 in optimizing GmolPBP2-Cod interaction.

CONCLUSION

The C10═C11 is thought to contribute greatly to Cod's stronger synergy as a group key to the higher GmolPBP2-affinity, based on which the improvement directions for Cod and Dod were addressed as well. Our findings will aid in the development and optimization of more effective pheromone synergists, resulting in more effective pheromone-based pest management.

Structure dynamics reveal key residues essential for the sense of 1-dodecanol by Cydia pomonella pheromone binding protein 2 (CpomPBP2)

BACKGROUND

Cydia pomonella, a worldwide quarantine fruit pest, causes great damage to fruit production every year. Sex pheromone-mediated control of C. pomonella has been widely used. As an indispensable ingredient of commercial sex attractants, 1-dodecanol (Dod) works to synergize the effect of codlemone in attracting male moths of C. pomonella. The interactions between Dod and its transporter protein, C. pomonella pheromone-binding protein 2 (CpomPBP2), provide inspiration for chemical optimizations to improve the synergistic effects of Dod.

RESULTS

In this research, molecular simulations and biological verifications were used in combination to uncover key residues in CpomPBP2 essential for sensing Dod. After performing 150 ns molecular dynamics (MD) simulations, the C1-C12 chain of Dod was found to be locked by the van der Waals energy contributed by the hydrophobic residues Phe12, Leu68, and Ile113, whereas the -OH part of Dod was anchored by the H-bond derived from Glu98 and the salt-bridge derived from Arg109. Because of the importance of these two electrostatic interactions, Glu98 and Arg109 were further verified as key residues in determining the binding affinity between Dod and CpomPBP2. In addition, interactions unfavorable to the binding of Dod were described.

CONCLUSION

The research detailed the discovery of key residues involved in CpomPBP2-Dod interactions. Our results provide guidance and caution for the prospective discovery, optimization, and design of novel chemicals with a similar or stronger synergistic effect to codlemone in controlling C. pomonella.

Identification of chemosensory genes from the antennal transcriptome of Semiothisa cinerearia

Olfaction plays vital roles in the survival and reproduction of insects. The completion of olfactory recognition requires the participation of various complex protein families. However, little is known about the olfactory-related proteins in Semiothisa cinerearia Bremer et Grey, an important pest of Chinese scholar tree. In this study, we sequenced the antennal transcriptome of S. cinerearia and identified 125 olfactory-related genes, including 25 odorant-binding proteins (OBPs), 15 chemosensory proteins (CSPs), two sensory neuron membrane proteins (SNMPs), 52 odorant receptors (ORs), eight gustatory receptors (GRs) and 23 ionotropic receptors (IRs). BLASTX best hit results and phylogenetic analyses indicated that these genes were most identical to their respective orthologs from Ectropis obliqua. Further quantitative real-time PCR (qRT-PCR) analysis revealed that three ScinOBPs and three ScinORs were highly expressed in male antennae, while seven ScinOBPs and twelve ScinORs were female-specifically expressed. Our study will be useful for the elucidation of olfactory mechanisms in S. cinerearia.

Repurposing a traditional Japanese method of pest control for wintering pine moths, Komo-trap, for use against summer and winter populations of fall webworms

Background

The fall webworm, Hyphantria cunea Drury (Lepidoptera: Erebidae), is a widespread invasive species. It is native to North America, ranging from southern Canada to northern Mexico. During and after the 1940s, this pest was accidentally introduced in many parts of Europe and Asia. It has now spread to more than 30 countries. The larvae feed on leaves of a wide range of tree species, including ones used as street trees in cities, causing an increase in urban management cost. Although several pest management methods have been employed, pest damage continues especially in newly invaded areas. In this study, we examined the effect and cost-effectiveness of the komo-trap, traditionally used in Japan to reduce the population of larvae of the pine moth Dendrolimus spectabilis Butler (Lepidoptera: Lasiocampidae). This trap, which is safe for people and ecosystems, has not yet been applied to trap the fall webworm.

Methods

In two seasons of 2017, we set komo-traps on street trees in Hakodate City, Japan. We counted the numbers of captured fall webworms compared with controls. We also monitored other species to evaluate any nontarget effects of the trap.

Results

One komo, the material cost of which is about 1.10 USD, captured 43.8 fall webworms on average in summer and 27.2 in the fall. The values were significantly larger than those of the controls, which were 0.07 in summer and 0.14 in winter. Bycatch of other species was minimal in summer, whereas in the fall one komo, on average, caught 10.7 woodlice Porcellio sp. or spp. (Isopoda: Porcellionidae).

Discussion

The komo-trap is effective in capturing fall webworm. The cost performance of the trap is very favorable, and the nontarget effects can be reduced by using the trap in summer only. The komo-trap would complement other control methods such as tree pruning. Because its cost is low, we recommend that the komo-trap be introduced as a larger-scale trial.

Key Amino Acid Residues Influencing Binding Affinities of Pheromone-Binding Protein from Athetis lepigone to Two Sex Pheromones

Athetis lepigone is a polyphagous pest found around the world that feeds on maize, wheat, and various other important crops. Although it exhibits a degree of resistance to various chemical insecticides, an effective pest-control method has not yet been developed. The sex pheromone communication system plays an essential role in the mating and reproduction of moths, in which pheromone-binding proteins (PBPs) are crucial genes. In this study, we cloned and purified the protein AlepPBP1 using an E. coli expression system and found it had a higher binding affinity to two sex pheromones of A. lepigone, namely, Z7-12:Ac and Z9-14:Ac (with K_i 0.77 ± 0.10 and 1.10 ± 0.20 μM, respectively), than to other plant volatiles. The binding-mode analysis of protein conformation with equilibrium stabilization was obtained using molecular dynamics (MD) simulation and indicated that hydrophobic interactions involving several nonpolar residues were the main driving force for the binding affinity of AlepPBP1 with sex pheromones. Computational alanine scanning (CAS) was performed to further identify key amino acid residues and validate their binding contributions. Each key residue, including Phe36, Trp37, Val52, and Phe118, was subsequently mutated into alanine using site-directed mutagenesis. Binding assays showed that the efficient binding abilities to Z7-12:Ac (F36A, W37A, and F118A) and Z9-14:Ac (F36A, W37A, V52A, and F118A) were almost lost in the mutated proteins. Our results demonstrated that these key amino acid residues are crucial for determining the binding ability of AlepPBP1 to sex pheromones. These findings provide a basis for the use of AlepPBP1 in the studies as a specific target for the development of novel behavioral antagonists with marked inhibition or mating-disruption abilities using computer-aided drug design (CADD).

Mating Disruption of Chilo suppressalis From Sex Pheromone of Another Pyralid Rice Pest Cnaphalocrocis medinalis (Lepidoptera: Pyralidae)

The rice stem borer, Chilo suppressalis (Walker), and the rice leaf folder, Cnaphalocrocis medinalis Guenée, are two of the most destructive lepidopteran pests in rice. Since these two pyralid insects overlap in their occurrence in rice paddy fields, farmers prefer to set their pheromone-baited traps together in the rice fields for their monitoring. However, our field observation demonstrated that no male adult of C. suppressalis was captured in traps baited with commercial sex pheromone of C. suppressalis (CCS) combined with commercial sex pheromone of C. medinalis (CCM). To confirm that the C. medinalis sex pheromone component(s) interfere with the attraction of males of the rice stem borers to their conspecific females, single components of C. medinalis sex pheromone combined with CCS in traps were tested in the laboratory and rice paddy field. The results revealed that the two alcohol components in CCM, i.e., (Z)-11-octadecen-1-ol (Z11-18: OH) and (Z)-13-octadecen-1-ol (Z13-18: OH) may cause a significant reduction in capturing C. suppressalis males caused by CCS. We recommend against using these sex pheromones together in the field and suggest that Z11-18: OH and Z13-18: OH could be potential inhibitors or antagonists of C. suppressalis sex pheromone to control the rice stem borer.

Functional characterization of four sex pheromone receptors in the newly discovered maize pest Athetis lepigone

Chemoreception systems play a crucial role in regulating key behavioral activities of insects, such as mating, oviposition, and foraging. Odorant receptors (ORs) trigger the transduction of chemical signals into electric signals, and are involved in the corresponding responses associated with odorant guidance behaviors. Pheromone receptors (PRs) of male adult insects are generally thought to function in the recognition of female sex pheromones, and are also important molecular targets for the development of behavioral inhibitors and insecticides. In this study, we successfully expressed and functionally analyzed four AlepPRs of Athetis lepigone in Xenopus oocytes using the two-electrode voltage-clamp method. The results demonstrated that AlepOR3 responded exclusively to the sex pheromone compound of A. lepigone, (Z)-7-dodecenyl acetate (Z7-12:Ac) (EC₅₀ = 8.830 × 10^-6 M), while AlepOR4 responded to all five compounds [(Z7-12:Ac, (Z)-8-dodecenyl acetate (Z8-12:Ac), (Z)-9-tetradecenyl acetate (Z9-14:Ac), (Z,E)-9,11-tetradecadienyl acetate (Z9,E11-14:Ac), and (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:Ac)] and had a higher response to Z9-14:Ac (EC₅₀ = 2.243 × 10^-5 M) than to Z7-12:Ac. However, AlepOR6 displayed a significantly higher response to a non-pheromone of A. lepigone, Z9,E12-14:Ac (EC₅₀ = 7.145 × 10^-6 M), than to the other four compounds. AlepOR5 displayed no responses to any of the pheromone compounds of A. lepigone, but responded exclusively to (Z)-11-hexadecenyl acetate (Z11-16:Ac) (EC₅₀ = 7.870 × 10^-6 M), a sex pheromone compound of other Noctuidae species. These findings can help explore the molecular mechanisms of sex pheromone recognition in A. lepigone and other moths, and develop broad-spectrum behavioral inhibitors and insecticides against different maize moths in future.

Identification and Field Evaluation of the Sex Pheromone of Orthaga achatina (Lepidoptera: Pyralidae)

Orthaga achatina (Lepidoptera: Pyralidae) is the most serious pest in south China of camphor trees, Cinnamomum camphora (L.) Presl, an important urban tree species. Gas chromatography-electroantennographic detection (GC-EAD) of the sex pheromone of O. achatina showed three EAD-active components. Coupled gas chromatography/mass spectrometry analyses identified these as (Z)-11-hexadecenol (Z11-16:OH), (Z)-11-hexadecenyl acetate (Z11-16:OAc), and (3Z,6Z,9Z,12Z,15Z)-tricosapentaene (Z3,Z6,Z9,Z12,Z15-23:H). In field tests using different combinations of the three compounds, male moths were attracted to a mixture of Z11-16:OAc and Z3,Z6,Z9,Z12,Z15-23:H, but less attracted to other blends. Further field tests with different ratios of the two compounds determined the optimal ratio of the binary blend as 500:250. The addition of Z11-16:OH to Z11-16:OAc, or to the binary mixture of Z11-16: OAc and the pentaene did not yield higher catches. This shows that O. achatina uses a mixture of Type I and Type II sex pheromone components. Orthaga achatina is the third Pyraloidea species found to utilize Z3,Z6,Z9,Z12,Z15-23:H as a sex pheromone component.

Asymmetric Total Synthesis of Four Stereoisomers of the Sex Pheromone of the Western Corn Rootworm

A convergent synthesis of four stereoisomers of the sex pheromone of the western corn rootworm (8-methyldecan-2-yl propionate, 1) from commercially available chiral starting materials is reported. The key step was Julia–Kocienski olefination between chiral BT-sulfone and chiral aldehyde. This synthetic route provided the four stereoisomers of 1 in 24–29% total yield via a six-step sequence. The simple scale-up strategy provides a new way to achieve the asymmetric synthesis of the sex pheromone.

Evidence of Premating Isolation Between Two Sibling Moths: Ectropis grisescens and Ectropis obliqua (Lepidoptera: Geometridae)

The sex pheromones of Ectropis grisescens Warren and Ectropis obliqua Prout were both reported to contain (Z,Z,Z)-3,6,9-octadecatriene (Z3,Z6,Z9-18:H) and (Z,Z)-3,9-cis-6,7-epoxy-octadecadiene (Z3,epo6,Z9-18:H). To clarify how these two sibling geometrids maintain premating isolation, the female sex pheromones of the two species were reexamined. Gas chromatography-electroantennographic detection (GC-EAD) and gas chromatography-mass spectrometry revealed two GC-EAD-active compounds, Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H, in E. grisescens female pheromone glands as well as an additional GC-EAD-active compound, (Z,Z)-3,9-cis-6,7-epoxy-nonadecadiene (Z3,epo6,Z9-19:H), in E. obliqua female pheromone glands. Synthesized Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H elicited dose-dependent electroantennogram (EAG) responses from male antennae of both E. grisescens and E. obliqua. However, Z3,epo6,Z9-19:H only elicited dose-dependent EAG responses from E. obliqua and limited EAG responses from E. grisescens at all doses. In wind-tunnel studies, lures that contained Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H attracted E. grisescens males and had no effect on E. obliqua males. The addition of Z3,epo6,Z9-19:H to the blend of Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H strongly attracted E. obliqua males but had a limited attraction for E. grisescens males. Thus, Z3,Z6,Z9-18:H and Z3,epo6,Z9-18:H were sex pheromone components of E. grisescens, whereas Z3,Z6,Z9-18:H, Z3,epo6,Z9-18:H and Z3,epo6,Z9-19:H were sex pheromone components of E. obliqua. The presence or absence of Z3,epo6,Z9-19:H played a central role in the premating isolation of these two sibling species.