Mango headspace volatiles trigger differential responses of the mango fruit fly Ceratitis cosyra and its parasitoids

Before the introduction of Bactrocera dorsalis (Hendel) to sub-Saharan Africa, Ceratitis cosyra (Walker) was economically the most important pest in mango farming. Its native natural enemy, the solitary parasitoid Psyttalia cosyrae (Wilkinson), played a crucial role in C. cosyra bio-control, later complemented by the exotic parasitoids Diachasmimorpha longicaudata (Ashmead) and Fopius arisanus (Sonan) among Integrated Pest Management (IPM) systems. To understand the in situ mango-C. cosyra-parasitoid tritrophic interaction, we assessed the responses of the fruit fly and the three parasitoids to headspace volatiles from various mango conditions. These conditions included non-infested mature unripe mangoes, C. cosyra-infested mangoes, 7th- and 9th-day post-infestation mangoes, non-infested ripe mangoes of three varieties (Kent, Apple, and Haden), and clean air (blank). We also compared the fruit fly's performance in the mango varieties and identified the chemical profiles of mango headspace volatiles. Ceratitis cosyra was attracted to both infested and non-infested mangoes (66-84 % of responsive C. cosyra) and showed superior performance in Kent mango (72.1 % of the 287 puparia recovered) compared to Apple and Haden varieties. Fopius arisanus displayed a stronger attraction to the volatiles of C. cosyra-infested mangoes (68-70 %), while P. cosyrae and D. longicaudata were significantly attracted to the 9th-day post-infestation mangoes (68-78 %) compared to non-infested mango volatiles. Gas chromatography-mass spectroscopy showed substantial quantitative and qualitative differences in volatile profiles among mango treatments. Esters predominated in non-infested ripe, 7th- and 9th-day post-infestation mangoes, while monoterpenes and sesquiterpenes were most dominant in the other treatments. The in situ experiments underscored varying preferences of the species for mango headspace volatiles and their subsequent treatments. These results provide valuable insights for further exploration, specifically in identifying the key volatiles responsible for species responses, to facilitate the development of applicable selective semiochemicals for managing species of African fruit fly.

Solvent Extraction of PDMS Tubing as a New Method for the Capture of Volatile Organic Compounds from Headspace

Polydimethylsiloxane (PDMS) tubing is increasingly being used to collect volatile organic compounds (VOCs) from static biological headspace. However, analysis of VOCs collected using PDMS tubing often deploys thermal desorption, where samples are considered as 'one-offs' and cannot be used in multiple experiments. In this study, we developed a static headspace VOC collection method using PDMS tubing which is solvent-based, meaning that VOC extracts can be used multiple times and can be linked to biological activity. Using a synthetic blend containing a range of known semiochemicals (allyl isothiocyanate, (Z)-3-hexen-1-ol, 1-octen-3-one, nonanal, (E)-anethol, (S)-bornyl acetate, (E)-caryophyllene and pentadecane) with differing chemical and physicochemical properties, VOCs were collected in static headspace by exposure to PDMS tubing with differing doses, sampling times and lengths. In a second experiment, VOCs from oranges were collected using PDMS sampling of static headspace versus dynamic headspace collection. VOCs were eluted with diethyl ether and analysed using gas chromatography - flame ionization detector (GC-FID) and coupled GC - mass spectrometry. GC-FID analysis of collected samples showed that longer PDMS tubes captured significantly greater quantities of compounds than shorter tubes, and that sampling duration significantly altered the recovery of all tested compounds. Moreover, greater quantities of compounds were recovered from closed compared to open systems. Finally, analysis of orange headspace VOCs showed no qualitative differences in VOCs recovered compared to dynamic headspace collections, although quantities sampled using PDMS tubing were lower. In summary, extraction of PDMS tubing with diethyl ether solvent captures VOCs from the headspace of synthetic blends and biological samples, and the resulting extracts can be used for multiple experiments linking VOC content to biological activity.

Methyl eugenol aromatherapy: a delivery system facilitating the simultaneous application of male annihilation and sterile insect technique against the peach fruit fly

BACKGROUND

The peach fruit fly, Bactrocera zonata (Saunders) (Diptera: Tephritidae) is an economically important polyphagous, quarantine pest endemic to South and South-East Asia. The male annihilation technique (MAT) and the sterile insect technique (SIT) are environmentally benign techniques used to suppress fruit fly populations on an area-wide basis. The MAT and SIT are typically used sequentially to avoid killing released sterile males; however, MAT and SIT potentially could be used simultaneously and thereby increase the overall efficiency of control programmes. Mating competitiveness of sterile males against wild counterparts is critical for the success of the SIT. Feeding on a semiochemical, methyl eugenol (ME) has been reported to enhance the male mating performance of many Bactrocera spp., including B. zonata, but its use in SIT operational programmes is limited owing to the absence of a viable delivery system.

RESULTS

In the present study, we demonstrated that ME aromatherapy, a practical method for large-scale delivery of ME olfactorily, enhances the mating success of treated B. zonata males. ME aromatherapy application to 5-day-old immature males for a duration of 5 h resulted in increased mating success of males tested when sexually mature, compared to untreated males. The ME-aromatized males also exhibited reduced attraction to ME-lure.

CONCLUSION

A practical delivery system for applying ME by aromatherapy to mass-reared males was developed. ME-aromatherapy enhanced male mating success and suppressed their subsequent attraction to ME, thus enabling the application of MAT and SIT at the same time. © 2023 Society of Chemical Industry.

Investigating volatile semiochemical production from Bos taurus and Bos indicus as a novel phenotype for breeding host resistance to ixodid ticks

Ticks and tick-borne diseases cause significant loss in livestock production with about 80% world's cattle at risk. The cost of chemical control is high and there is an ever-increasing tick resistance to chemical acaricides. Genetic selection as alternative long-term control strategy is constrained by laborious phenotyping using tick counts or scores. This study explored the use of host volatile semiochemicals that may be attractants or repellents to ticks as a phenotype for new tick resistance, with potential to be used as a proxy in selection programmes. Approximately 100 young cattle composed of Bos indicus and Bos taurus were artificially infested with 2,500 African blue tick, Rhipicephalus decoloratus larvae, with daily female tick (4.5 mm) counts taken from day 20 post-infestation. Volatile organic compounds were sampled from cattle before and after tick infestation by dynamic headspace collection, analysed by high-resolution gas chromatography (GC) and subjected to multivariate statistical analysis. Using 6-day repeated measure analysis, three pre-infestation GC peaks (BI938 - unknown, BI966 - 6-methyl-5-hepten-2-one and BI995 - hexyl acetate) and one post-infestation GC peak (AI933 - benzaldehyde / (E)-2-heptenal) were associated with tick resistance (P < 0.01 and P < 0.05 respectively). The high correlation coefficients (r = 0.66) between repeated records with all volatile compounds support the potential predictive value for volatile compounds in selective breeding programmes for tick resistance in cattle.

Semiochemical Release and Ontogenetic Changes in a Primary Scent Gland of Podisus maculiventris

The spined shoulder bug, Podisus maculiventris, is a generalist predator studied for its biocontrol potential. Despite our growing understanding of gland development, the conditions that elicit releases are largely unknown. To determine if male age or gland development affects the chemical composition and release behavior, we dissected adult male bugs and profiled the chemical composition of the male DAG 1, 7, and 14 d post-eclosion. To determine if gland development is related to sexual maturity, we counted the number of sperm present in the seminal vesicles at the same time points. Finally, we measured the diurnal release patterns of different aged males and in various male-female combinations. We observed that newly eclosed adults have under-developed glands and male seminal vesicles contained few sperm. One week post-eclosion the DAG contained previously reported semiochemical compounds and males contained many sperm. Mirroring the trend in reproductive maturation and gland development, the number of semiochemical releases increased with age and the majority of releases followed a scotophase pattern unaffected by sexual composition. These findings link male age to 1) dorsal abdominal gland development 2) release behavior and 3) sexual maturity, which will help our understanding of when these olfactory cues are present for other organisms, like prey, to perceive. Given the results, releasing adults that are at least 1 week post eclosion will maximize the non-consumptive effects of this biocontrol agent.

(1R,4R)-Quercivorol, a Male-Produced Aggregation-Sex Pheromone of the Beetle Elytrimitatrix undata (F.) (Coleoptera: Disteniidae)

The beetle family Disteniidae is currently considered to be closely related to the much larger family Cerambycidae, the longhorned beetles. The 300 + species of disteniids are mostly native to tropical and subtropical regions, with the only described North American species north of Mexico being Elytrimitatrix undata (F.). Here we describe the identification and field testing of (1R,4R)-quercivorol as a male-produced aggregation-sex pheromone component for E. undata. This is the first pheromone identified for any species within the family Disteniidae.

Cuticular Hydrocarbon Profiling by Fractionation and GC-MS in Socially Parasitic Ants

Ants use cuticular hydrocarbon (CHC) as a semiochemical for recognizing their nestmates. For socially parasitic ants, deceiving the CHC is an important survival strategy. Profiling and quantifying CHC is a potent approach to understanding such nestmate discrimination behavior. Thus, a highly efficient, stable, and reproducible extraction method for CHC is essential for this purpose. This paper describes a method for socially parasitic ants to disguise the host species' CHC profile under laboratory conditions, as well as the extraction and measurement of CHC from ants (from a previous study). First, the artificial isotopic substance is applied to the host worker; then, the socially parasitic ant disguises the host-like CHC profile against the above host worker. Next, the CHC is extracted and fractionated from a socially parasitic ant using hexane and silica gel. After concentrating the fractionated product, this product is then used for measurement by gas chromatographymass spectrometry (GC-MS). The CHC extraction protocol described in this paper may be used for various ant species.

Molecular identification and functional analysis of Niemann-Pick type C2 proteins，carriers for semiochemicals and other hydrophobic compounds in the brown dog tick, Rhipicephalus linnaei

Ticks are important vectors of many pathogens with tremendous impact on human and animal health. Studies of semiochemical interactions and mechanisms underlying chemoreception can provide important tools in tick management. Niemann-Pick type C2 (NPC2) proteins have been proposed as one type of chemoreceptor in arthropods. Here, we cloned two NPC2 genes in the brown dog tick, Rhipicephalus linnaei, the tropical lineage previously named R. sanguineus sensu lato and characterized them functionally. R.linNPC2a and R.linNPC2b genes were found to be expressed at each developmental stage with the highest level in adult males. By using quantitative real-time PCR we revealed expression in multiple tissues, including midgut, ovary, salivary glands and legs. Ligand binding analysis revealed that R.linNPC2b bound a wide spectrum of compounds, with β-ionone, α-amylcinnamaldehyde, 2-nitrophenol and benzaldehyde displaying the strongest binding affinity (Ki < 10 μM), whereas R.linNPC2a showed a more narrow ligand binding range, with intermediate binding affinity to α-amylcinnamaldehyde and 2-nitrophenol (Ki < 20 μM). Molecular docking indicated that the amino acid residue Phe89, Leu77 and Val131 of R.linNPC2a and Phe70, Leu132 and Phe73 of R.linNPC2b could bind multiple ligands. These residues might thus play a key role in the identification of the volatiles. Our results contribute to the understanding of olfactory mechanisms of R. linnaei and can offer new pathways towards new management strategies.

Sea Lamprey Alarm Cue Comprises Water- and Chloroform- Soluble Components

A diversity of aquatic organisms manage predation risk by avoiding waters activated with conspecific alarm cues, a chemical mixture released from injuries. The sea lamprey (Petromyzon marinus) is a nocturnal migratory species that relies on its alarm cue to navigate around areas of predation risk when moving through river channels. Identification of the cue’s chemistry would allow managers to harness this innate behavioral response to guide migrating sea lamprey to traps (invasive population in the Laurentian Great Lakes) or to fish passage devices where dams block migrations in their native range. We pursued isolation of the sea lamprey alarm cue through behaviorally guided fractionation, fractionating the alarm cue into water-soluble and chloroform-soluble fractions, each of which elicited a substantial avoidance response. Recombining the two fractions restored full reactivity, suggesting the alarm cue mixture contains components that exhibit high solubility in water (e.g., nitrogenous compounds), chloroform (e.g., lipids), or perhaps materials that dissolve readily in either solvent. We further screened 13 individual compounds or pure isolates and 6 sub-fractions from the water-soluble fraction and found one of the pure isolates, isoleucine, evoked an avoidance response on its own, but not consistently when found in other mixtures. In a third experiment, we observed no behavioral response after recombining 32 compounds isolated and identified from the water-soluble fraction. These results confirm other suggestions that the process of elucidating alarm cue constituents is challenging. However, we suggest the pursuit is worthwhile given the strong evidence for the utility of alarm cues for use in the conservation and management of fishes and other aquatic organisms.

Field Response of Black Turpentine Beetle to Pine Resin Oxidation and Pheromone Displacement

The black turpentine beetle, Dendroctonus terebrans, is an economically important pest of pines in the Southeastern U.S., with a high potential for invasion to other pine-rich regions. Dendroctonus terebrans attraction to an injured host tree lessens over time as the host material degrades. Likewise, kairomonal volatiles emitted from the host change as constituents of the defensive resin oxidize. Therefore we hypothesized that volatiles associated with a fresh host would be more attractive to D. terebrans than those associated with a dead or dying host. We replicated the natural oxidation process of turpentine, fractionated the distilled products to isolate the oxidized products, and deployed the complex mixtures to measure field attraction based on the amount of oxidation performed. Contrasting with previous studies, our results suggest that D. terebrans attraction is not primarily based on host tree degradation. In a second experiment incorporating Dendroctonus pheromones, we demonstrate D. terebrans has a displacement-dependent response to endo-brevicomin, a pheromone associated with the sympatric southern pine beetle, D. frontalis. This has implications not only for possible interspecific signaling, but also for the role of endo-brevicomin in D. terebrans colonization behavior. The results from this study broaden the understanding of D. terebrans chemical ecology and directly contribute to the development of an effective lure-based monitoring system that will benefit future research and management efforts. This may become important if the species is established outside its native range, as in the closely related red turpentine beetle, Dendroctonus valens, which caused mass pine tree mortality following its introduction to Asia.

Identification and quantification of 11 airborne biochemicals emitted by the brown recluse and another primitive hunting spider using headspace solid-phase microextraction-GC/MS

Loxosceles reclusa, or brown recluse spider, is a harmful household spider whose habitat extends throughout the Midwest in the USA and other regions in the world. The pheromones and other biomolecules that facilitate signaling for brown recluses and other spider species are poorly understood. A rapid and sensitive method is needed to analyze airborne spider signaling biomolecules to better understand the structure and function of these biochemicals in order to control the population of the spiders. In this study, we developed a novel headspace solid-phase microextraction (HS-SPME)-GC/MS method to analyze potential pheromones and biomolecules emitted by the brown recluse spider. The method is highly selective and sensitive for biomolecule identification and quantification from a single live spider. Using this novel non-destructive HS-SPME-GC/MS technique, we identified 11 airborne biomolecules, including 4-methylquinazoline, dimethyl sulfone, 2-methylpropanoic acid, butanoic acid, hexanal, 3-methylbutanoic acid, 2-methylbutanoic acid, 2,4-dimethylbenzaldehyde, 2-phenoxyethanol, and citral (contains both isomers of neral and geranial). Some of these airborne biomolecules were also reported as semiochemicals associated with biological functions of other spiders and insects. The method was also applied to study the airborne biochemicals of Plectreurys tristis, another primitive hunting spider with a poor web, enabling quantitation of the same compounds and demonstrating a difference in signaling molecule concentrations between the two species. This method has potential application in the study of pheromones and biological signaling in other species, which allows for the possibility of utilizing attractant or deterrent functions to limit household populations of harmful species.

Chemical Ecology of the Asian Longhorn Beetle, Anoplophora glabripennis

The Asian longhorn beetle (ALB), Anoplophora glabripennis (Motschulsky), is a destructive forest pest in its native range, East Asia, or a high-risk invasive species in many other parts of the world. Extensive research has been directed toward the development of ALB management strategies. However, semiochemical-based trap lures, which are one of the effective tools for detecting, monitoring, and potentially assisting in eradicating cerambycids, have not reached operational efficacy for ALB to date, which is probably due to a grossly incomplete understanding of its chemical ecology. Here, we summarize the current progress in ALB chemical ecology including host selection and location, pheromone identification, trapping techniques, olfactory system, and related biology and behavior. We also briefly review the known semiochemicals in the subfamily Lamiinae, particularly the ALB congener, A. chinensis. Based on this knowledge, we highlight a potentially important role of some host-original chemicals, such as sesquiterpenes, in ALB host and mate location, and emphasize the basic studies on the biology and behavior of adult ALB. Last, we formulate suggestions for further research directions that may contribute to a better understanding of ALB chemical ecology and improved lure efficacy.

Novel use of PDMS tubing for in-soil capture of plant natural products

The extraction of small lipophilic molecules (SLMs) in the soil-root interface that play a role in belowground ecological interactions between plants and insect herbivores was investigated. Polydimethylsiloxane (PDMS) microtubing has been shown to absorb root SLMs selectively in low-disturbance setups, where analytes were extracted from the polymer with methanol. This technique was adapted to isolate SLMs that diffuse in the vapour phase in soil and sand and under various experimental parameters, extracting with a plug of diethyl ether pushed through the length of the silicon tubing. Moisture level had a substrate-dependent effect on the recovery rate of analytes that were applied as synthetic blends of known belowground SLM semiochemicals in the media. Higher amounts of two selected SLMs, (E)-caryophyllene and (-)-thujopsene, were extracted from sand, and increased polymer and solvent volume, as well as sampling duration, resulted in more of these two SLMs recovered by extraction. It was also shown that PDMS tubes lose no extraction capacity after repeated use. The signature compound (E)-caryophyllene was successfully isolated from the rhizosphere of maize plants infested with Diabrotica v. virgifera larvae by extracting the silicon tubing with diethyl ether. Because the tubes are preconditioned to reduce the presence of contaminants, such extracts can be directly analysed by GC and GC-MS and used in electrophysiological and behavioural assays. After further modifications, non-invasive, in situ PDMS probes can be developed that extract SLMs from plant rhizosphere for the study of belowground chemical ecology processes.

Morphological characterization of antennal sensilla of Earias vittella (Fabricius) (Lepidoptera: Nolidae)

The shoot and fruit borer, Earias vittella Fab. (Lepidoptera: Nolidae) is an important and most devastating insect pest on okra and cotton. The pest mainly responsible for causing significant direct damage to tender shoots and fruits of okra, flowers and green bolls of cotton causing net yield loss in both crops. Many non-chemical control strategies have been developed under the insect pest management program, A complete knowledge on the antennal morphology of E. vitella is essential for future electrophysiological and behavioural studies. In the present study, the antennal morphology and types of sensilla on the antennae of both sexes of E. vitella were examined using light and scanning electron microscopy. Nine distinct types of sensilla were identified on the antennae of both sexes: sensilla trichodea, sensilla basiconica, sensilla coeloconica, sensilla auricillica (multiporous), sensilla chaetica, uniporous peg sensilla (uniporous), sensilla styloconica, sensilla squamiformia and bohm bristles (aporous). Among all sensilla, the most widespread are multiporous sensilla trichodea with 42.90 ± 1.77/flagellomere in male and 37.38 ± 1.38/flagellomere in female. Sensilla basiconica were the second most common sensillum type in male antennae with 15.67 ± 1.92/flagellomere. Other multiporous sensilla such as auricillica (11.90 ± 0.99) and coeloconica (4.57 ± 0.25) were significantly more abundant in female than in male antennae. Results of the study provide morphological evidence that E. vitella antennae possess microscopic cuticular structures that can play a role in perception of pheromones, plant odours and other chemical stimulants. This will open up opportunities to assess the possibility of using pheromones and plant-derived compounds for the monitoring or management of E. vittella moths in the agricultural landscapes.

Infochemicals Influence Neonicotinoid Toxicity-Impact in Leaf Consumption, Growth, and Predation of the Amphipod Gammarus fossarum

Infochemicals act as inter- or intraspecific messengers. The literature suggests complex interactions between infochemicals (mainly predator cues) and chemical (e.g., pesticide) effects, with their direction and magnitude depending on the cue origin, pesticide identity, and test species. With the present study we assessed the impact of alarm cues alone and in combination with the neonicotinoid insecticide thiacloprid on leaf consumption, predation on Baetis nymphs, and dry weight of the amphipod Gammarus fossarum. Alarm cues (ground gammarids) and thiacloprid alone decreased gammarid leaf consumption with increasing intensities. At a defined alarm cue intensity, which alone did not cause a significant reduction in gammarid feeding, thiacloprid-induced feeding effects were additive. During an experiment targeting gammarid predation on Baetis nymphs (120 h), thiacloprid and alarm cues alone did increase and reduce predation significantly, respectively. Moreover, alarm cues led to a lower final gammarid dry weight. However, alarm cues did not affect response variables during a second predation experiment performed at a higher thiacloprid concentration (2 vs 0.75 µg/L). This discrepancy in alarm cue effects highlights either a varying susceptibility of the test species to these cues among experiments or that cue quality is fluctuating. Thus, the present study highlights a considerable variability in the individual and interactive effects of infochemicals and chemical stressors on aquatic biota, an insight relevant in the assessment of multiple stressors. Environ Toxicol Chem 2020;39:1755-1764. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Individual Chemical Profiles in the Leach's Storm-Petrel

Avian chemical communication, once largely overlooked, is a growing field that has revealed the important role that olfaction plays in the social lives of some birds. Leach's storm-petrels (Oceanodroma leucorhoa) have a remarkable sense of smell and a strong, musky scent. This long-lived, monogamous seabird relies on olfaction for nest relocation and foraging, but whether they use scent for communication is less well studied. They are nocturnally active at the breeding colony and yet successfully reunite with their mate despite poor night-vision, indicating an important role for non-visual communication. We investigated the chemical profiles of Leach's storm-petrels to determine whether there is socially relevant information encoded in their plumage odor. To capture the compounds comprising their strong scent, we developed a method to study the compounds present in the air surrounding their feathers using headspace stir bar sorptive extraction coupled with gas chromatography-mass spectrometry. We collected feathers from Leach's storm-petrels breeding on Bon Portage Island in Nova Scotia, Canada in both 2015 and 2016. Our method detected 142 commonly occurring compounds. We found interannual differences in chemical profiles between the two sampling years. Males and females had similar chemical profiles, while individuals had distinct chemical signatures across the two years. These findings suggest that the scent of the Leach's storm-petrel provides sociochemical information that could facilitate olfactory recognition of individuals and may inform mate choice decisions.

Comparison of BG-Lure and BG-Sweetscents attractants for field sampling of phlebotomine sand flies

Phlebotomines are important vectors of bacteria, viruses and protozoan parasites. Protozoans of the genus Leishmania which cause visceral and cutaneous leishmaniases, are among the most important etiologic agents transmitted by sand flies. Different blends of human and animal volatiles have been evaluated for use in surveillance and/or control of hematophagous insects. With regard to phlebotomine sand flies there are few records of attraction under laboratory and field conditions. This study was carried out at two collecting sites located in a Brazilian town with a high prevalence of cutaneous leishmaniasis. The aim of the present study was to evaluate the effect of adding two kinds of commercial bait which mimic human odors to light traps to attract sand flies and compare the results with those of light traps without any additional bait. The commercial baits, BG-Lure® and BG-Sweetscent®, were developed to catch anthropophilic mosquitoes. Three treatments were evaluated: 1 - HP light trap with BG-Lure® added; 2 - HP light trap with BG-Sweetscent® added and 3- HP light trap without any attractant. A total of 3,682 sand flies were collected during the study. Constrained correspondence analysis was applied to perform ordination of the captured community of sand fly species that could be explained by attractant, sampling site and sex. The most abundant species: Pintomyia nevesi, Nyssomyia whitmani and Nyssomyia antunesi were further investigated by fitting generalized linear mixed models. Only Ny. whitmani showed a slight indication of an increase in catches with BG-Lure®.

Common Cerambycid Pheromone Components as Attractants for Longhorn Beetles (Cerambycidae) Breeding in Ephemeral Oak Substrates in Northern Europe

Longhorn beetles are ecologically important insects in forest ecosystems as decomposers of woody substrates, microhabitat engineers, and as components of forest food webs. These species can be greatly affected both positively and negatively by modern forestry management practices, and should be monitored accordingly. Through headspace sampling, coupled gas chromatography-electroantennography, gas chromatography-mass spectrometry, and field bioassays, we identified two compounds, 2-methyl-1-butanol and 3-hydroxy-2-hexanone, that constitute aggregation-sex pheromone attractants of three cerambycid species which breed primarily in different types of fresh, recently dead oak wood in Northern Europe: Pyrrhidium sanguineum (L.), Phymatodes alni ssp. alni (L.), and Phymatodes testaceus (L.) (Cerambycinae: Callidiini). Analyses of headspace volatiles collected from live insects indicated that the male-produced aggregation-sex pheromone of P. sanguineum is a 1–15:100 blend of (R)-2-methyl-1-butanol and (R)-3-hydroxy-2-hexanone, whereas the corresponding ratios for P. alni were 70–110:100. In field bioassays, adult P. sanguineum and P. alni were significantly attracted to multiple blends with varying ratios of the two compounds. When tested individually, the compounds were minimally attractive. In contrast, adult P. testaceus exhibited nonspecific attraction to both of the individual compounds and to different blends, despite the hydroxyketone not being part of its pheromone, which consists of (R)-2-methyl-1-butanol alone. Overall, our results suggest that a blend of 50:100 of racemic 2-methyl-1-butanol and 3-hydroxy-2-hexanone is appropriate for parallel, cost-efficient pheromone-based monitoring of all three species. In particular, these species could serve as useful indicators of how modern forestry practices affect a whole guild of saproxylic insects that require ephemeral deadwood substrates for successful breeding.

Seeing the wood for the trees: A new way to view the human intestinal microbiome and its connection with non-communicable disease

Our paper briefly reviews the connection of the intestinal microbiome to the rise in non-communicable conditions related to atopic disease, obesity and mental health. We consider that the microbiome is best treated as if it were a single entity and have borrowed the terms semiochemical, allomone and kairomone (5) to describe interspecies relationship between the microbiome and ourselves (Fig. 1). We use the term dysbiosis to describe the breakdown of these relationships leading to disease (Fig. 2). As a result of this analysis we tentatively suggest that components of the microbiome assess microbial antigens in our food and pass this information back to our immune system via as yet undescribed chemical messengers: kairomones. We call these hypothetical microbial agents Sentinel Cells. Our suggestion is that atopic disease arises partly as a result of consuming processed food that has insufficient antigens to activate this kairomone feedback mechanism, which atrophies as a result. We note that this is potentially similar to the Old Friends concept of Rook and his co-workers (16). We suggest that obesity is a consequence of dysbiosis-induced waning of the output of allomone-like psychotropic compounds (including the known microbial metabolites dopamine and serotonin) leading to the weakening of the gut-brain axis and a negative effect on mental health. Although dysbiosis can occur in other ways, including antibiotic use and sterile caesarian section, we believe that all these problems can be overcome to provide a future free of these non-communicable diseases.

(Z)-7-Hexadecene is an Aggregation-Sex Pheromone Produced by Males of the South American Cerambycid Beetle Susuacanga octoguttata

We describe the identification, synthesis, and field bioassays of a novel aggregation-sex pheromone produced by males of Susuacanga octoguttata (Germar), a South American cerambycid beetle. Analyses of extracts of headspace volatiles produced by adult beetles revealed a sex-specific compound emitted by males which was identified as (Z)-7-hexadecene by microchemical and spectroscopic analyses. The synthesized pheromone was attractive to beetles of both sexes in field trials. This unsaturated hydrocarbon motif is unprecedented among cerambycid pheromones identified to date. During field bioassays, we serendipitously discovered that adults of S. octoguttata trapped in two Brazilian biomes differed considerably in elytral markings, although males from both populations produced (Z)-7-hexadecene as an aggregation-sex pheromone.

Validation of analytical method for rhynchophorol quantification and stability in inorganic matrix for the controlled release of this pheromone

A fast method for the identification and stability evaluation of the aggregation pheromone rhynchophorol, which is the main substance used for chemical communication by the beetle Rhynchophorus palmarum L., was validated. In addition, the technique was applied to the evaluation of two inorganic matrices, with the objective of using them as controlled-release devices. The analytical method showed good linearity (R² = 0.9978), precision (CV% < 1.79), recovery (84–105%) and limits of detection (0.2 mg mL⁻¹) and quantification (0.3 mg mL⁻¹); in compliance with the validation legislation established by ANVISA. In the interaction study, the inorganic matrices zeolite L and Na-magadiite showed high rates of pheromone recovery without promoting its degradation for a period of 180 days, which is not reported in the literature for other matrices. The structures of the zeolite L/rhynchophorol and Na-magadiite/rhynchophorol composites showed slower release kinetics during the storage period when compared with pure pheromone, which is desirable since it extends the period of rhynchophorol release and decreases the negative effects caused by the environmental parameters.

The Scent of the Fly

(Z)-4-undecenal (Z4-11Al) is the volatile pheromone produced by females of the vinegar fly Drosophila melanogaster. Female flies emit Z4-11Al for species-specific communication and mate-finding. A sensory panel finds that synthetic Z4-11Al has a characteristic flavour, which can be perceived even at the small amounts produced by a single female fly. Since only females produce Z4-11Al, and not males, we can reliably distinguish between single D. melanogaster males and females, according to their scent. Females release Z4-11Al at 2.4 ng/h and we readily sense 1 ng synthetic Z4-11Al in a glass of wine (0.03 nmol/L), while a tenfold concentration is perceived as a loud off-flavour. This corroborates the observation that a glass of wine is spoilt by a single D. melanogaster fly falling into it, which we here show is caused by Z4-11Al. The biological role of Z4-11Al or structurally related aldehydes in humans and the basis for this semiochemical convergence remains yet unclear.

Chemical Ecology of Chemosensation in Asteroidea: Insights Towards Management Strategies of Pest Species

Within the Phylum Echinodermata, the class Asteroidea, commonly known as starfish and sea stars, encompasses a large number of benthos inhabiting genera and species with various feeding modalities including herbivores, carnivores, omnivores and detritivores. The Asteroidea rely on chemosensation throughout their life histories including hunting prey, avoiding or deterring predators, in the formation of spawning aggregations, synchronizing gamete release and targeting appropriate locations for larval settlement. The identities of many of the chemical stimuli that mediate these physiological and behavioural processes remain unresolved even though evidence indicates they play pivotal roles in the functionality of benthic communities. Aspects of chemosensation, as well as putative chemically-mediated behaviours and the molecular mechanisms of chemoreception, within the Asteroidea are reviewed here, with particular reference to the coral reef pest the Crown-of-Thorns starfish Acanthaster planci species complex, in the context of mitigation of population outbreaks.

Interpopulational and seasonal variation in the chemical signals of the lizard Gallotia galloti

Communicative traits are strikingly diverse and may vary among populations of the same species. Within a population, these traits may also display seasonal variation. Chemical signals play a key role in the communication of many taxa. However, we still know far too little about chemical communication in some vertebrate groups. In lizards, only a few studies have examined interpopulational variation in the composition of chemical cues and signals and only one study has explored the seasonal effects. Here we sampled three subspecies of the Tenerife lizards (Gallotia galloti) and analyze the lipophilic fraction of their femoral gland secretions to characterize the potential interpopulational variation in the chemical signals. In addition, we assessed whether composition of these secretions differed between the reproductive and the non-reproductive season. We analyzed variations in both the overall chemical profile and the abundance of the two main compounds (cholesterol and vitamin E). Our results show interpopulational and seasonal differences in G. gallotia chemical profiles. These findings are in accordance with the high interpopulational variability of compounds observed in lizard chemical signals and show that their composition is not only shaped by selective factors linked to reproductive season.

Quercivorol as a lure for the polyphagous and Kuroshio shot hole borers, Euwallacea spp. nr. fornicatus (Coleoptera: Scolytinae), vectors of Fusarium dieback

The polyphagous shot hole borer and Kuroshio shot hole borer, two members of the Euwallacea fornicatus species complex (Coleoptera: Curculionidae: Scolytinae), are invasive ambrosia beetles that harbor distinct species of Fusarium fungal symbionts. Together with the damage caused by gallery construction, these two phytopathogenic Fusarium species are responsible for the emerging tree disease Fusarium dieback, which affects over 50 common tree species in Southern California. Host trees suffer branch dieback as the xylem is blocked by invading beetles and fungi, forcing the costly removal of dead and dying trees in urban areas. The beetles are also threatening natural riparian habitats, and avocado is susceptible to Fusarium dieback as well, resulting in damage to the avocado industries in California and Israel. Currently there are no adequate control mechanisms for shot hole borers. This paper summarizes efforts to find a suitable lure to monitor shot hole borer invasions and dispersal. Field trials were conducted in two counties in Southern California over a span of two years. We find that the chemical quercivorol is highly attractive to these beetles, and perform subsequent field experiments attempting to optimize this lure. We also explore other methods of increasing trap catch and effects of other potential attractants, as well as the deterrents verbenone and piperitone.

Identification of the Aggregation-sex Pheromone Produced by Male Monochamus saltuarius, a Major Insect Vector of the Pine Wood Nematode

In this study, we isolated and identified an aggregation-sex pheromone from Monochamus saltuarius, the major insect vector of the pine wood nematode in Korea. Adult males of M. saltuarius produce 2-undecyloxy-1-ethanol, which is known as an aggregation-sex pheromone in other Monochamus species. We performed field experiments to determine the attractiveness of the pheromone and other synergists. More M. saltuarius adult beetles were attracted to traps baited with the pheromone than to unbaited traps. Ethanol and (-)-α-pinene interacted synergistically with the pheromone. Traps baited with the pheromone + (-)-α-pinene +ethanol were more attractive to M. saltuarius adults than traps baited with the pheromone, (-)-α-pinene, or ethanol alone. Ipsenol, ipsdienol, and limonene were also identified as synergists of the aggregation-sex pheromone for M. saltuarius adults. In field experiments, the proportion of females was much higher in the beetles caught in traps than among the beetles emerging from naturally-infested logs in the laboratory. Our results suggest that a combination of aggregation-sex pheromone and synergists could be very effective for monitoring and managing M. saltuarius.

Cucumber mosaic virus and its 2b protein alter emission of host volatile organic compounds but not aphid vector settling in tobacco

BACKGROUND

Aphids, including the generalist herbivore Myzus persicae, transmit cucumber mosaic virus (CMV). CMV (strain Fny) infection affects M. persicae feeding behavior and performance on tobacco (Nicotiana tabacum), Arabidopsis thaliana and cucurbits in varying ways. In Arabidopsis and cucurbits, CMV decreases host quality and inhibits prolonged feeding by aphids, which may enhance virus transmission rates. CMV-infected cucurbits also emit deceptive, aphid-attracting volatiles, which may favor virus acquisition. In contrast, aphids on CMV-infected tobacco (cv. Xanthi) exhibit increased survival and reproduction. This may not increase transmission but might increase virus and vector persistence within plant communities. The CMV 2b counter-defense protein diminishes resistance to aphid infestation in CMV-infected tobacco plants. We hypothesised that in tobacco CMV and its 2b protein might also alter the emission of volatile organic compounds that would influence aphid behavior.

RESULTS

Analysis of headspace volatiles emitted from tobacco plants showed that CMV infection both increased the total quantity and altered the blend produced. Furthermore, experiments with a CMV 2b gene deletion mutant (CMV∆2b) showed that the 2b counter-defense protein influences volatile emission. Free choice bioassays were conducted where wingless M. persicae could choose to settle on infected or mock-inoculated plants under a normal day/night regime or in continual darkness. Settling was recorded at 15 min, 1 h and 24 h post-release. Statistical analysis indicated that aphids showed no marked preference to settle on mock-inoculated versus infected plants, except for a marginally greater settlement of aphids on mock-inoculated over CMV-infected plants under normal illumination.

CONCLUSIONS

CMV infection of tobacco plants induced quantitative and qualitative changes in host volatile emission and these changes depended in part on the activity of the 2b counter-defense protein. However, CMV-induced alterations in tobacco plant volatile emission did not have marked effects on the settling of aphids on infected versus mock-inoculated plants even though CMV-infected plants are higher quality hosts for M. persicae.

Effect of Brood Pheromone on Survival and Nutrient Intake of African Honey Bees (Apis mellifera scutellata) under Controlled Conditions

The influence of pheromones on insect physiology and behavior has been thoroughly reported for numerous aspects, such as attraction, gland development, aggregation, mate and kin recognition. Brood pheromone (BP) is released by honey bee larvae to indicate their protein requirements to the colony. Although BP is known to modulate pollen and protein consumption, which in turn can affect physiological and morphological parameters, such as hypopharyngeal gland (HPG) development and ovarian activation, few studies have focused on the effect of BP on nutritional balance. In this study, we exposed newly emerged worker bees for 14 d and found that BP exposure increased protein intake during the first few days, with a peak in consumption at day four following exposure. BP exposure decreased survival of caged honey bees, but did not affect either the size of the HPG acini or ovarian activation stage. The uncoupling of the BP releaser effect, facilitated by working under controlled conditions, and the presence of larvae as stimulating cues are discussed.

Chemical Composition of the Low-Polar Fraction of the Copitarsia uncilata Burgos & Leiva (Lepidoptera: Noctuidae) Eversible Pheromone Gland

In Colombia, Copitarsia uncilata Burgos & Leiva has been reported as a pest of ornamental flowers. The leafworm causes serious economic losses to farmers because the shipments are intercepted at the detection sites. The identification and subsequent synthesis of the sex pheromone compounds can lead to the use of semiochemicals as an important strategy to complement the pest management. This paper identifies and characterizes the chemical components of the female sexual gland of C. uncilata at three different age stages in order to relate the effect of age on the gland extract composition. Eggs and larvae were collected from commercial crops. The specimens were reared and sexed. Pheromone glands of intact females were excised at (a) 1-2, (b) 3-4, and (c) 5-6 days old. The extracts were analyzed using GC-MS after two extraction time points: 20 min and 8 days. The extracts from the third age stage showed an increase in concentration for 35% of the compounds after 8 days of storage. The relative abundance as a function of the female age showed two trends: an upward trend, where the relative abundances of the compounds increased through the age stages, while some compounds shown a downward trend. Within the first trend, mostly of the compounds were found to be related with infochemicals type structures, where tetradec-9-en-1-yl acetate (within several C-14 long-chain alcohols) is the main one. The 9-14:Ac quadrupled concentration through the ages is possibly related to the increased length of calling period as female moth age.

Synergism between Enantiomers Creates Species-Specific Pheromone Blends and Minimizes Cross-Attraction for Two Species of Cerambycid Beetles

Research over the last decade has revealed extensive parsimony among pheromones within the large insect family Cerambycidae, with males of many species producing the same, or very similar aggregation pheromones. Among some species in the subfamily Cerambycinae, interspecific attraction is minimized by temporal segregation, and/or by minor pheromone components that synergize attraction of conspecifics or inhibit attraction of heterospecifics. Less is known about pheromone-based mechanisms of reproductive isolation among species in the largest subfamily, the Lamiinae. Here, we present evidence that the pheromone systems of two sympatric lamiine species consist of synergistic blends of enantiomers of (E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol) and the structurally related (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (fuscumol acetate), as a mechanism by which species-specific blends of pheromone components can minimize interspecific attraction. Male Astylidius parvus (LeConte) were found to produce (R)- and (S)-fuscumol + (R)-fuscumol acetate + geranylacetone, whereas males of Lepturges angulatus (LeConte) produced (R)- and (S)-fuscumol acetate + geranylacetone. Field experiments confirmed that adult beetles were attracted only by their species-specific blend of the enantiomers of fuscumol and fuscumol acetate, respectively, and not to the individual enantiomers. Because other lamiine species are known to produce single enantiomers or blends of enantiomers of fuscumol and/or fuscumol acetate, synergism between enantiomers, or inhibition by enantiomers, may be a widespread mechanism for forming species-specific pheromone blends in this subfamily.

(6E,8Z)-6,8-Pentadecadienal, a Novel Attractant Pheromone Produced by Males of the Cerambycid Beetles Chlorida festiva and Chlorida costata

We report the identification, synthesis, and first field bioassays of a pheromone component with a novel structure produced by adult males of Chlorida festiva (L.) and Chlorida costata Audinet-Serville, longhorn beetle species in the subfamily Cerambycinae. Headspace volatiles from males contained a sex-specific compound that was identified as (6E,8Z)-6,8-pentadecadienal. Traps baited with this compound captured adults of both species and sexes, consistent with the aggregation-sex pheromones produced by males of many species in this subfamily. This compound represents a new structural class of cerambycid pheromones, and it is the first pheromone identified from species in the tribe Bothriospilini.

Sex and Aggregation-Sex Pheromones of Cerambycid Beetles: Basic Science and Practical Applications

Research since 2004 has shown that the use of volatile attractants and pheromones is widespread in the large beetle family Cerambycidae, with pheromones now identified from more than 100 species, and likely pheromones for many more. The pheromones identified to date from species in the subfamilies Cerambycinae, Spondylidinae, and Lamiinae are all male-produced aggregation-sex pheromones that attract both sexes, whereas all known examples for species in the subfamilies Prioninae and Lepturinae are female-produced sex pheromones that attract only males. Here, we summarize the chemistry of the known pheromones, and the optimal methods for their collection, analysis, and synthesis. Attraction of cerambycids to host plant volatiles, interactions between their pheromones and host plant volatiles, and the implications of pheromone chemistry for invasion biology are discussed. We also describe optimized traps, lures, and operational parameters for practical applications of the pheromones in detection, sampling, and management of cerambycids.

Regulatory Innovation, Mating Disruption and 4-Play(TM) in New Zealand

Straight-chained lepidopteran pheromones are now regulated under a group standard in New Zealand, which is generic for moth pheromone products of similar low risk, under the Hazardous Substances and New Organisms Act (1996). This means that compliant new pheromone products can be developed and commercialized with low regulatory requirements. This encourages innovation and supports fruit industries interested in meeting export phytosanitary standards, while targeting low or nil residues of pesticides. Changes to pheromone blends for reasons such as technical improvements or variations in pest species composition in different crops can be made with minimal regulatory involvement. We illustrate how this system now operates with a four species mating disruption product commercialized in 2012. The odors involved in "4-Play™" consist of a range of components used by codling moth (Cydia pomonella), lightbrown apple moth (Epiphyas postvittana), green-headed leafroller (Planotortrix octo), and brown-headed leafroller (Ctenopseustis obliquana). The development of 4-Play™ illustrates how mating disruption of insects can support industry goals.

A new attractant for monitoring western flower thrips, Frankliniella occidentalis in protected crops

Monitoring of pest populations is an essential component of integrated pest management. An early warning system helps growers decide when best to take control measures, or when to alter them, should a control method prove inadequate. Studies have shown that adding chemical attractants to sticky cards can increase trap catch of western flower thrips, Frankliniella occidentalis, a global pest of agriculture and horticulture, giving more accurate accounts of population size and dynamics, thus leading to more efficient monitoring. We identify a novel semiochemical to the species, (S)-(−)-verbenone, showing that addition of this compound to sticky traps significantly increased F. occidentalis catch in two geographically distinct populations, infesting two unrelated crops of global economic importance. We validate through field trials that (S)-(−)-verbenone is highly attractive to F.occidentalis and can be used with blue sticky traps to enhance trap catch, leading to better estimations of pest population densities. The compound may be used in other control methods against F.occidentalis such as lure and kill, mass trapping and push-pull.

The roles of kairomones, synomones and pheromones in the chemically-mediated behaviour of male mosquitoes

Despite decades of intensive study of the chemical ecology of female mosquitoes, relatively little is known about the chemical ecology of males. This short review summarizes the current state of knowledge of the chemicals that mediate male mosquito behaviour. Various trophic interactions including insect-plant, insect-host, and insect-insect responses are emphasized. The relevance of the chemical ecology of male mosquitoes in the context of vector control programmes is discussed.