Analysis Of Headspace Volatiles Research Articles

Blends of (R)-3-hydroxyhexan-2-one and alkan-2-ones identified as potential pheromones produced by three species of cerambycid beetles

We present data indicating that three species of cerambycid beetles (subfamily Cerambycinae) produce the common cerambycine pheromone component (R)-3-hydroxyhexan-2-one as well as an alkan-2-one component, a possible new motif for cerambycid pheromone components. GC/MS analyses of headspace volatiles produced by male beetles indicated that Cyrtophorus verrucosus (Olivier) produced (R)-3-hydroxyhexan-2-one but also nonan-2-one at ~18 % of the hydroxyketone component, whereas Orwellion gibbulum arizonense (Casey) and Parelaphidion aspersum (Haldeman) produced decan-2-one at ~40 and 7 % of the amount of the hydroxyketone, respectively. In field bioassays, adult C. verrucosus were attracted by (R)-3-hydroxyhexan-2-one alone, but attraction was significantly enhanced by nonan-2-one. This effect was lost if the quantity of nonan-2-one exceeded 100 % of the hydroxyketone, suggesting that beetles could discern ratios of the two chemicals and were most strongly attracted to those approximating the blend produced by males. We suggest that nonan-2-one plays a role in the species specificity of the pheromone signal of C. verrucosus, and that decan-2-one plays a similar role in the semiochemical communication of O. g. arizonense and P. aspersum.

Comparison of Antioxidant Capacities of Rosmarinate Alkyl Esters in Riboflavin Photosensitized Oil‐in‐Water Emulsions

AbstractEffects of the alkyl chain length of rosmarinate alkyl esters on the oxidative stability in photosensitized oil‐in‐water (O/W) emulsions were determined by lipid hydroperoxides and headspace volatile analyses. Antioxidant capacities of 20 μM rosmarinate esters with alkyl chain length of 0, 4, 8, 12, 18, and 20 were tested in O/W emulsion containing stripped soybean oil, Tween 20 as an emulsifier, and riboflavin as a photosensitizer. Synergistic or antagonistic effects of 20 μM α‐tocopherol in the presence of rosmarinate alkyl esters were also determined. Samples containing rosmarinate with 4 and 8 alkyl esters showed lower lipid hydroperoxides and headspace volatiles than those without rosmarinate and those with 0, 12, 18, and 20 alkyl esters, which indicates that phenolic free radical scavengers showed antioxidant capacities non‐linearly in riboflavin photosensitized O/W emulsions. Antagonistic rather than synergistic effects were observed in all rosmarinate alkyl esters with α‐tocopherol in current conditions although rosmarinates with 4, 8, and 12 alkyl esters showed better antioxidant capacities than those with other alkyl chain length. The results of this study clearly showed that rosmarinates need the proper length of non‐polar groups to show optimum antioxidant capacities in O/W emulsions with Tween 20 as an emulsifier under riboflavin photosensitization.

The Effect of Antibrowning Agents on Inhibition of Potato Browning, Volatile Organic Compound Profile, and Microbial Inhibition

Burbank and Norkotah potato slices were dipped into 3% sodium acid sulfate (SAS), citric acid (CA), sodium erythorbate (SE), malic acid (MA), sodium acid pyrophosphate (SAPP), or a combination of SAS-CA-SE. Browning by polyphenol oxidase (PPO) obtained from potato extract with 0.04 to 0.016 g/mL of antibrowning solutions at pH 2.0 to 6.9 were measured by UV-Vis spectroscopy. The color of slices dipped in antibrowning solutions at pHs 2 to 7 and stored at 4 °C for 15 d was measured every 5 d by colorimeter. Headspace analysis of volatiles in raw and cooked potato samples was performed by selected ion flow tube mass spectrometer (SIFT-MS) and soft independent modelling by class analogy (SIMCA) analysis of the calculated odor activity values (OAV) determined interclass distances. Microbial growth was measured at 15 d. At unadjusted pHs (1.1 to 7.1), the PPO browning of the control and samples with SAPP was not significantly different, SAS, CA, and MA produced some inhibition and SE and SAS-CA-SE prevented browning. At pH 5 to 7, only SE and SAS-CA-SE were effective browning inhibitors. Based on the color of potato slices, SE was the most effective at pH 2 to 7, but SAS was most effective at unadjusted pH. Cooking increased volatile levels in the treated potatoes and decreased differences between volatile profiles. Differences between cooked samples may not be noticeable by the consumer because volatiles with high discriminating powers have low OAVs. SAS, CA, and SAS-CA-SE treatments inhibited microbial growth but SAPP, control, and SE did not, most likely due to pH. Antibrowning agents inhibit polyphenol oxidase, increasing shelf life and consumer acceptability of processed raw potato products by preserving the color. Their effectiveness was shown to be mainly due to a pH effect, except SE, which was not pH dependent. MA, CA, and SAS-CA-SE are better acidulants for inhibition of color change as well as growth of spoilage bacteria, yeast, and mold than SAPP, the industry standard.

Herbivory by a Phloem-Feeding Insect Inhibits Floral Volatile Production

There is extensive knowledge on the effects of insect herbivory on volatile emission from vegetative tissue, but little is known about its impact on floral volatiles. We show that herbivory by phloem-feeding aphids inhibits floral volatile emission in white mustard Sinapis alba measured by gas chromatographic analysis of headspace volatiles. The effect of the Brassica specialist aphid Lipaphis erysimi was stronger than the generalist aphid Myzus persicae and feeding by chewing larvae of the moth Plutella xylostella caused no reduction in floral volatile emission. Field observations showed no effect of L. erysimi-mediated floral volatile emission on the total number of flower visits by pollinators. Olfactory bioassays suggested that although two aphid natural enemies could detect aphid inhibition of floral volatiles, their olfactory orientation to infested plants was not disrupted. This is the first demonstration that phloem-feeding herbivory can affect floral volatile emission, and that the outcome of interaction between herbivory and floral chemistry may differ depending on the herbivore's feeding mode and degree of specialisation. The findings provide new insights into interactions between insect herbivores and plant chemistry.

Antioxidant capacities of α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate in riboflavin photosensitized oil-in-water emulsions

Antioxidant capacities of α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate at 0.01, 0.1, and 1.0mM in riboflavin photosensitized oil-in-water (O/W) emulsions were determined using headspace oxygen depletion, lipid hydroperoxide, and headspace volatile analyses. After 32h visible light irradiation, headspace oxygen in O/W emulsions without adding antioxidants, with 1.0mM α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate decreased to 18.50%, 18.85%, 16.01%, 17.92%, and 19.88%, respectively, whereas those samples in the dark were 20.74%. Trolox and ascorbic acid acted as prooxidants while their lipophilic counterparts, α-tocopherol and ascorbyl palmitate, respectively showed antioxidant properties. Similar antioxidative or prooxidative properties of the tested compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. However, the prooxidant and antioxidant properties of the tested compounds were not clearly shown at 0.01 and 0.1mM concentration. Both the type and concentration of antioxidants influenced the antioxidant capacities in riboflavin photosensitized O/W emulsions.

Enhanced β-ionone Emission in Arabidopsis Over-expressing <I>AtCCD1</I> Reduces Feeding Damage <I>in vivo</I> by the Crucifer Flea Beetle

Plant carotenoid derived β-ionone has been shown to have diverse biological effects on some insect herbivores and herbivore parasitoids. In this study, Arabidopsis transgenic plants over-expressing a carotenoid cleavage dioxygenase1 gene (AtCCD1) were generated to test whether β-ionone emissions could be enhanced and used to control feeding by the crucifer flea beetle (Phyllotreta cruciferae Goeze). The transgenic plants exhibited a morphological phenotype indistinguishable from the wild type (WT) control over their complete life cycle. Gas chromatography and mass spectrometry analyses of headspace volatiles collected from 6-wk-old intact flowering plants revealed substantially enhanced β-ionone emission from transgenic plants compared with WT, but no β-ionone enhancement occurred at a young vegetative stage (4-wk-old seedlings). Bioassays in an enclosed environment showed that AtCCD1 over-expression resulted in ≍50% less leaf area damage by flea beetles on transgenic plants compared with WT plants. The mean number of damaged transgenic leaves per plant also was significantly lower in transgenic plants (P<0.05). Our results indicate that AtCCD1 over-expression and induced β-ionone emission might find application in the control of pests for Brassica crops grown in greenhouse operations. Potentially, β-ionone also could be used on crops grown in open-air ecosystems if this allomone is released in sufficient quantities to discourage herbivore foragers.

Behavioural and chemical evidence of a male‐produced aggregation pheromone in the flower thrips Frankliniella intonsa

The response of adult flower thrips Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) to conspecifics is investigated in Y‐tube olfactometer bioassays. The results show that both males and females are attracted to the odours of adult males, which indicates a male‐produced aggregation pheromone in this species. Gas chromatography‐mass spectroscopy analyses of headspace volatiles collected on solid‐phase microextraction fibres show that two major components and six minor components are present in volatiles from males but not in females. Further gas chromatography‐mass spectroscopy analyses reveal that the two major components in head‐space volatiles produced by F. intonsa males are the same compounds that are reported in volatiles of Frankliniella occidentalis males: (R)‐lavandulyl acetate and neryl (S)‐2‐methylbutanoate. However, the quantity of these two compounds in the volatiles differs between the species.

Volatile Compound Fingerprinting of Mixed-Culture Fermentations

With the advent of the -omics era, classical technology platforms, such as hyphenated mass spectrometry, are currently undergoing a transformation toward high-throughput application. These novel platforms yield highly detailed metabolite profiles in large numbers of samples. Such profiles can be used as fingerprints for the accurate identification and classification of samples as well as for the study of effects of experimental conditions on the concentrations of specific metabolites. Challenges for the application of these methods lie in the acquisition of high-quality data, data normalization, and data mining. Here, a high-throughput fingerprinting approach based on analysis of headspace volatiles using ultrafast gas chromatography coupled to time of flight mass spectrometry (ultrafast GC/TOF-MS) was developed and evaluated for classification and screening purposes in food fermentation. GC-MS mass spectra of headspace samples of milk fermented by different mixed cultures of lactic acid bacteria (LAB) were collected and preprocessed in MetAlign, a dedicated software package for the preprocessing and comparison of liquid chromatography (LC)-MS and GC-MS data. The Random Forest algorithm was used to detect mass peaks that discriminated combinations of species or strains used in fermentations. Many of these mass peaks originated from key flavor compounds, indicating that the presence or absence of individual strains or combinations of strains significantly influenced the concentrations of these components. We demonstrate that the approach can be used for purposes like the selection of strains from collections based on flavor characteristics and the screening of (mixed) cultures for the presence or absence of strains. In addition, we show that strain-specific flavor characteristics can be traced back to genetic markers when comparative genome hybridization (CGH) data are available.

Electrophysiological Response of Female Dogwood Borer (Lepidoptera: Sesiidae) to Volatile Compounds from Apple Trees

Coupled gas chromatography and electroantennogram detection (GC-EAD) analyses of headspace volatiles from apple host tissues revealed a total of 16 compounds to which female dogwood borer, Synanthedon scitula (Harris), antennae responded. There were no differences in the amplitude of the response of antennae from virgin and mated females, and no consistent responses to host odors were generated from male antennae. Four compounds, including octanal, nonanal, decanal, and methyl salicylate, were identified from all headspace collections taken from apple trees. Use of the solid-phase microextraction (SPME) technique revealed that a single volatile compound, α-bergamotene, emanating from larval dogwood borer frass elicited a strong female antennal response. This compound was also present in headspace collections from ‘Red Chief Delicious’ apple trees with burr knot tissue infested with dogwood borer larvae and from 1-d-old cut bark on ‘Granny Smith’ trees, suggesting that it is produced by apple trees in resp...

Effects of Metal Chelator, Sodium Azide, and Superoxide Dismutase on the Oxidative Stability in Riboflavin-Photosensitized Oil-in-Water Emulsion Systems

The effects of riboflavin photosensitization on the oxidative stability of oil-in-water (O/W) emulsions were determined using lipid hydroperoxides and headspace volatile analyses. The influences of a metal chelator, sodium azide, and superoxide dismutase (SOD) on oxidation pathways were tested to gain a better understanding of the role of transition metals, singlet oxygen, and superoxide anion, respectively. Emulsions with riboflavin and visible light irradiation had significantly higher lipid hydroperoxides and volatiles (p < 0.05) as compared to samples without light irradiation or riboflavin. The addition of ethylenediammetetraacetic acid (EDTA) decreased the formation of lipid hydroperoxides, hexanal, 2-heptenal, and 1-octen-3-ol in a concentration-dependent manner. Sodium azide, a singlet oxygen physical quencher, only inhibited the formation of 2-heptenal and 1-octen-3-ol. Overall, photosensitized riboflavin participated in both type I and type II pathways in O/W emulsions, and these pathways enhance the prooxidant activity of metals through their ability to produce lipid hydroperoxides and superoxide anion.

Male Phyllotreta striolata (F.) Produce an Aggregation Pheromone: Identification of Male-specific compounds and Interaction with Host Plant Volatiles

The chrysomelid beetle Phyllotreta striolata is an important pest of Brassicaceae in Southeast Asia and North America. Here, we identified the aggregation pheromone of a population of P. striolata from Taiwan, and host plant volatiles that interact with the pheromone. Volatiles emitted by feeding male P. striolata attracted males and females in the field. Headspace volatile analyses revealed that six sesquiterpenes were emitted specifically by feeding males. Only one of these, however, elicited an electrophysiological response from antennae of both sexes. A number of host plant volatiles, e.g., 1-hexanol, (Z)-3-hexen-1-ol, and the glucosinolate hydrolysis products allyl isothiocyanate (AITC), 3-butenyl isothiocyanate, and 4-pentenyl isothiocyanate also elicited clear responses from the antenna. The active male-specific compound was identified as (+)-(6R,7S)-himachala-9,11-diene by chiral stationary phase gas-chromatography with coupled mass spectrometry, and by comparison with reference samples from Abies nordmanniana, which is known to produce the corresponding enantiomer. The pheromone compound was synthesized starting from (-)-α-himachalene isolated from Cedrus atlantica. Under field conditions, the activity of the synthetic pheromone required concomitant presence of the host plant volatile allyl isothiocyanate. However, both synthetic (+)-(6R,7S)-himachala-9,11-diene alone and in combination with AITC were attractive in a two-choice laboratory assay devoid of other natural olfactory stimuli. We hypothesize that P. striolata adults respond to the pheromone only if specific host volatiles are present. In the same laboratory set up, more beetles were attracted by feeding males than by the synthetic stimuli. Thus, further research will be necessary to reveal the components of a more complex blend of host or male-produced semiochemicals that might enhance trap attractiveness in the field.

Detection of onion postharvest diseases by analyses of headspace volatiles using a gas sensor array and GC-MS

Onion postharvest diseases cause significant losses in storage. Volatile sensing by the gas sensor array technology could be used as a promising alternative method to detect onion diseases. Onions were inoculated with Botrytis allii and Burkholderia cepacia, causal pathogen for Botrytis neck rot and sour skin, respectively. In the first phase of this study, 30 onions with equal number of B. allii inoculated and control healthy onions were measured by the gas sensor array from 8 to 11 days after inoculation (dai) and the principal component analysis (PCA) score plot demonstrated that the gas sensor array responded differently to Botrytis neck rot infected onions from those of healthy onions. In the second phase, 30 onions with 10 for each of the three treatments (Botrytis neck rot, sour skin, control) were measured by the gas sensor array on 5, 6, and 7 dai. The PCA score plot illustrated that three treatments formed three distinct clusters, while a hierarchical cluster analysis dendrogram indicated that the response of the gas sensor array to Botrytis neck rot and sour skin were similar. The correct classification rate of the linear discriminant model for three treatments was over 97.8%. Results from GC-MS showed that total 24 major volatiles were identified from the headspace of three treatments. Sixteen compounds were uniquely present in B. allii and B. cepacia inoculated onion bulbs. Total amount of volatile compounds detected in pathogen inoculated bulbs was one to two orders of magnitude higher than that of control healthy bulbs. This study demonstrated the feasibility of using a gas sensor array to detect two onion postharvest diseases in storage.

Interactions Between the Yeast Ogataea pini and Filamentous Fungi Associated with the Western Pine Beetle

Ecologically important microbes other than filamentous fungi can be housed within the fungal-transport structures (mycangia) of Dendroctonus bark beetles. The yeast Ogataea pini (Saccharomycetales: Saccharomycetaceae) was isolated from the mycangia of western pine beetle (Dendroctonus brevicomis) populations in northern Arizona (USA) with a frequency of 56%. We performed a series of in vitro assays to test whether volatile organic compounds produced by O. pini affected radial growth rates of mutualistic and antagonistic species of filamentous fungi that are commonly found in association with the beetle including Entomocorticium sp. B, Ophiostoma minus, Beauvaria bassiana, and an Aspergillus sp. We determined the compounds O. pini produced when grown on 2% malt extract agar using a gas chromatography/mass spectrometry (GC/MS) analysis of headspace volatiles. Volatiles produced by O. pini on artificial media significantly enhanced the growth of the mutualistic Entomocorticium sp. B, and inhibited growth of the entomopathogenic fungus B. bassiana. GC/MS revealed that O. pini produced ethanol, carbon disulfide (CS(2)), and Δ-3-carene in headspace. The results of these studies implicate O. pini as an important component in D. brevicomis community ecology, and we introduce multiple hypotheses for future tests of the effects of yeasts in the symbiont assemblages associated with Dendroctonus bark beetles.

Comparative Analysis of Headspace Volatiles of Chinese Rosa rugosa

The floral headspace compounds of Chinese Rosa rugosa germplasms that were isolated by an automated headspace sampler with built-in trap, and followed by gas chromatography-mass spectrometry for identification and quantification. Up to 33 volatile compounds were identified from the 23 rose germplasms, including nine alcohols, five esters, three alkanes, 10 terpenes, three aldehydes, two ketones, and one ether. The main floral components identified were 2-phenylethanol, β-citronellol, ethanol, and n-hexane. ‘xizi’, ‘miaofengshan’, ‘xiangciguo’, and ‘tangbai’ contained the highest amounts of 2-phenylethanol at 84.66 μg·g-1, β-citronellol at 70.98 μg·g-1, ethanol at 83.87 μg·g-1, and n-hexane at 18.23 μg·g-1, respectively. ‘Rongchengyesheng’, ‘tanghong’, ‘xizi’, ‘miaofengshan’, and ‘baizizhi’ could be considered good materials for extracting rose oil and breeding new cultivars.

Auxin treatment of pre-veraison grape (Vitis vinifera L.) berries both delays ripening and increases the synchronicity of sugar accumulation

Background and Aims: Pre-veraison auxin treatments can delay grape berry ripening, but there is little information about their effects on berry development and wine composition. The aim of this study was to further investigate these effects and explore the practical implications of delaying ripening. Methods and Results: Treatment of pre-veraison Vitis vinifera L. cv. Shiraz berries with 1-naphthaleneacetic acid (NAA) significantly delayed ripening as measured by the accumulation of total soluble solids (TSS) and anthocyanins. The onset of the post-veraison phase of berry size increase was delayed in NAA-treated fruit, but these fruit were significantly larger than Control fruit at harvest. NAA-treatments significantly increased the synchronicity of berry sugar accumulation. GC-MS analysis of wine headspace volatiles showed significant, but largely small, differences in the concentration of 19 compounds. No significant difference in sensory properties was found between replicate small-scale wine lots made from Control and NAA-treated fruit. Conclusions: Auxin treatment delayed berry ripening, increased the synchronicity of sugar accumulation between berries, increased berry size and changed the levels of some volatile compounds, but did not affect wine sensory properties. Significance of the Study: We propose that NAA sprays might be used to delay grape berry ripening and increase the synchronicity of sugar accumulation, and therefore ripening, without deleterious effects on wine quality. This may be useful in controlling winery intake and fruit composition.

Male-Produced Sex Pheromone of the Cerambycid Beetle Hedypathes betulinus: Chemical Identification and Biological Activity

We identified, synthesized, determined the diel periodicity of release, and tested the bioactivity of components of the male-produced sex pheromone of Hedypathes betulinus (Coleoptera: Cerambycidae: Lamiinae). Gas chromatographic-mass spectrometric analysis of headspace volatiles from adult beetles showed three male-specific compounds, which were identified as (E)-6,10-dimethyl-5,9-undecadien-2-yl acetate (major component), (E)-6,10-dimethyl-5,9-undecadien-2-one (geranylacetone), and (E)-6,10-dimethyl-5,9-undecadien-2-ol. Release of these chemicals was dependent on time of the photoperiod and presence of the host plant. Pheromone release took place primarily during the photophase, with maximum release occurring between 4 and 6hr after the onset of photophase. The amount of pheromone released by males was much greater when they were in the presence of their host plant than when they were not. In Y-tube olfactometer tests, a ternary mixture of the compounds was attractive to female beetles, although the individual compounds were not attractive by themselves. Addition of volatiles from the host plant greatly increased the attractiveness of the ternary pheromone mixture and of the major pheromone component alone.

Guava leaf volatiles and dimethyl disulphide inhibit response of Diaphorina citri Kuwayama to host plant volatiles

The Asian citrus psyllid, Diaphorina citri Kuwayama, vectors the causal pathogen of huanglongbing (HLB), which is likely the most important disease affecting worldwide citrus production. Interplanting citrus with guava, Psidium guajava L., was reported to reduce D. citri populations and incidence of HLB. We describe a series of investigations on the response of D. citri to citrus volatiles with and without guava leaf volatiles and to synthetic dimethyl disulphide (DMDS), in laboratory olfactometers and in the field. Volatiles from guava leaves significantly inhibited attraction of D. citri to normally attractive host-plant (citrus) volatiles. A similar level of inhibition was recorded when synthetic DMDS was co-released with volatiles from citrus leaves. In addition, the volatile mixture emanating from a combination of intact citrus and intact guava leaves induced a knock-down effect on adult D. citri. Compounds similar to DMDS including dipropyl disulphide, ethyl-1-propyl disulphide, and diethyl disulphide did not affect the behavioural response of D. citri to attractive citrus host plant volatiles. Head-space volatile analyses were conducted to compare sulphur volatile profiles of citrus and guava, used in our behavioural assays, with a gas chromatography-pulsed flame photometric detector. DMDS, produced by wounded guava in our olfactometer assays, was not produced by similarly wounded citrus. The airborne concentration of DMDS that induced the behavioural effect in the 4-choice olfactometer was 107 pg/ml. In a small plot field experiment, populations of D. citri were significantly reduced by deployment of synthetic DMDS from polyethylene vials compared with untreated control plots. Our results verify that guava leaf volatiles inhibit the response of D. citri to citrus host plant volatiles and suggest that the induced compound, DMDS, may be partially responsible for this effect. Also, we show that field deployment of DMDS reduces densities of D. citri and thus may have potential as a novel control strategy.

Identification and characterisation of headspace volatiles of fish miso, a Japanese fish meat based fermented paste, with special emphasis on effect of fish species and meat washing

The present study investigated the suitability of four species of trash fishes for the production of fish miso, a Japanese fermented fish meat paste compared with soy and rice miso from the point of view of product aroma. The effect of washing fish meat on finished product was also evaluated. Headspace volatiles for different miso samples were analyzed by using solid phase microextraction (SPME) technique. A total of 107 volatile compounds have been identified, where 94 were common for all the miso samples. Considering the lower threshold perception and higher odour active values 2-methylbutanal, 3-methylbutanal, methional, isoamyl acetate, dimethyl disulfide, dimethyl trisulfide, 2,3-butanedione, 3-methylethyl butanoate, 3-methyl-1-butanol, ethyl hexanoate, 1-octen-3-ol, heptanol, heptanal and 2-undecanone were identified as key compounds for the miso products. Principal components analysis (PCA) and hierarchical cluster analysis (HCA) of headspace volatiles clearly elucidated the relationship amongst different miso samples based on fish species and effect of fresh water washing of meat on aroma of finished product.

Male-produced aggregation pheromones of the cerambycid beetles Xylotrechus colonus and Sarosesthes fulminans.

Adults of both sexes of the cerambycid beetles Xylotrechus colonus (F.) and Sarosesthes fulminans (F.) were attracted to odors produced by male conspecifics in olfactometer bioassays. Analyses of headspace volatiles from adults revealed that male X. colonus produced a blend of (R)- and (S)-3-hydroxyhexan-2-one and (2 S,3 S)- and (2R,3R)-2,3-hexanediol, whereas male S. fulminans produced (R)-3-hydroxyhexan-2-one and (2 S,3R)-2,3-hexanediol. All of these compounds were absent in the headspace of females. Two field bioassays were conducted to confirm the biological activity of the synthesized pheromones: (1) enantiomerically enriched pheromone components were tested singly and in species-specific blends and (2) four-component mixture of racemic 3-hydroxyhexan-2-one plus racemic 2-hydroxyhexan-3-one and the four-component blend of the stereoisomers of 2,3-hexanediols were tested separately and as a combined eight-component blend. In these experiments, adult male and female X. colonus were captured in greatest numbers in traps baited with the reconstructed blend of components produced by males, although significant numbers were also captured in traps baited with (R)-3-hydroxyhexan-2-one alone or in blends with other compounds. Too few adult S. fulminans were captured for a statistical comparison among treatments, but all were caught in traps baited with lures containing (R)-3-hydroxyhexan-2-one. In addition to these two species, adults of two other species of cerambycid beetles, for which pheromones had previously been identified, were caught: Neoclytus a. acuminatus (F.) and its congener Neoclytus m. mucronatus (F.). Cross-attraction of beetles to pheromone blends of other species, and to individual pheromone components that are shared by two or more sympatric species, may facilitate location of larval hosts by species that compete for the same host species.

Novel Lepidopteran Sex Pheromone Components From &lt;I&gt;Marmara gulosa&lt;/I&gt; (Lepidoptera: Gracillariidae)

Marmara gulosa Guillén & Davis (Lepidoptera: Gracillariidae) is a sporadic pest of citrus and a number of other crops in southern and central California. Coupled gas chromatographic-electroantennogram detection analyses of headspace volatiles collected by solid phase microextraction from virgin female moths revealed at least four related compounds in the extracts that elicited significant antennal responses from antennae of male moths. These compounds were identified as (8E,10E)-tetradecadien-1-ol, and the corresponding aldehyde, acetate, and formate ester, representing the first report of a formate as a lepidopteran pheromone component. The four compounds were consistently found in headspace volatiles collected from virgin female moths from different regions of the state and from M. gulosa collected from different host plants (citrus and squash). Repeated field trials determined that the formate ester alone was as attractive or more attractive than any blend of the formate with one or more of the remaining compounds. Although large numbers of moths were caught in some field trials, trap catches were not consistent. Thus, the pheromone may be useful for detection of the moth and setting an initial biofix, but it remains unclear whether the pheromone can be used as a reliable and accurate tool for monitoring densities of M. gulosa populations.