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The opisthonotal glands of Astigmata contain monoterpenes, aromatics, aliphatics, and other volatile compounds; some of these compounds act as pheromones and have antifungal effects. This study analyzed volatile compounds secreted by mites on three traditional mite-ripened cheeses from producers (Milbenkäse from Germany, Mimolette and Artisou from France). The mites obtained from various traditional ripened French cheeses (Mimolette, Laguiole, Salers, and Cantal vieux) from stores were also investigated. The gas chromatography (GC) profiles of all their hexane extracts, except the Cantal vieux one, showed almost no differences and were identical to that of Tyrolichus casei Oudemans except for trace components. Based on the GC results, the mites of Cantal vieux were identified as Acarus siro L. For the Artisou and Cantal vieux, not studied before, the influence of the mite secretions on their characteristics was investigated by analyzing the headspace volatiles from the cheeses. According to the results, neral secreted from T. casei is the main compound responsible for the lemon-like flavor of the mite-ripened cheeses, which is, hence, due to a component of the mite secretions rather than the fermentation of the cheese itself. Moreover, the compounds secreted by the mites are not directly added to the cheese through ripening as they were not detected in the odors of the Artisou and Cantal vieux after the mites were removed. However, the consumers of the Artisou usually eat also the cheese rind, and thus, can enjoy its lemon-like flavor fully.

Ambrosia beetles in the Euwallacea nr. fornicatus complex (Coleoptera: Curculionidae) vector Fusarium spp. fungi pathogenic to susceptible hosts, including avocado, Persea americana Mill., (Lauraceae). Previous survey traps in Florida avocado groves indicated significant beetle populations in several groves with minimal observed beetle activity, suggesting an external beetle source. A natural area near one such grove revealed E. nr. fornicatus colonization of wild tamarind, Lysiloma latisiliquum (L.) Bentham (Fabaceae). A survey of the natural area was conducted to understand the role that natural areas might play in E. nr. fornicatus ecology in southern Florida. Headspace volatiles from rasped avocado and L. latisiliquum bark were analyzed by gas chromatography-mass spectroscopy (GC-MS) to identify potential attractants. Genetic analysis confirmed that these beetles and their symbiotic fungi are of the same complex that attacks Florida avocado. Gas chromatography-mass spectroscopy analysis indicated that avocado is high in α-copaene (a known attractant of E. nr. fornicatus), but this kairomone is lacking in L. latisiliquum. Host diam and ht were examined for potential influence on colonization behavior. Albizia lebbeck (L.) Bentham (Fabaceae) and an unknown shrub also were observed to be suitable hosts. Concurrent with this study, a nearby grove of soursop, Annona muricata L. (Annonaceae), was found to have infestations of E. nr. fornicatus. Euwallacea nr. fornicatus populations are increasing in Florida and other cultivated and native trees are potentially at risk. Further research is warranted to better understand the ecology of this emerging pest and the chemical cues used for host location.

Chemical control of Drosophila suzukii (Diptera: Drosophilidae) based on the use of insecticides is particularly challenging as the insect attacks ripening fruits shortly before harvest. An alternative strategy may rely on the use of yeasts as phagostimulants and baits, applied on canopy as attract-and-kill formulations. The aim of this research was to identify the most attractive among six yeast species for D. suzukii: Saccharomyces cerevisiae, Hanseniaspora uvarum, Clavispora santaluciae, Saccharomycopsis vini, Issatchenkia terricola, and Metschnikowia pulcherrima. The volatile profile of C. santaluciae was described for the first time. Behavioural experiments identified H. uvarum and S. vini as the most attractive yeasts. The characterization of yeast headspace volatiles using direct headspace (DHS) and solid-phase microextraction (SPME) revealed several strain-specific compounds. With DHS injection, 19 volatiles were characterised, while SPME revealed 71 compounds constituting the yeast headspace. Both analyses revealed terpenoids including β-ocimene, citronellol, (Z)-geraniol (nerol), and geranial as distinct constituents of S. vini. H. uvarum and S. vini were further investigated using closed-loop stripping analysis (CSLA) and electroantennography. Out of 14 compounds quantified by CSLA, ethyl acetate, isoamyl acetate, β-myrcene, benzaldehyde and linalool were detected by D. suzukii antennae and might generate the strong attractiveness of S. vini and H. uvarum. Our results highlight a strong attraction of D. suzukii to various yeasts associated with both the flies and their habitat and demonstrate how different sampling methods can impact the results of volatile compound characterization. It remains to be demonstrated whether the distinct attraction is based on special adaptations to certain yeasts and to what extent the metabolites causing attraction are interchangeable.

Background Insects rely on chemosensory perception, mainly olfaction, for the location of mates, food sources, and oviposition sites. Plant-released volatile compounds guide herbivorous insects to search for and locate their host plants, further helping them to identify suitable positions for oviposition. The fall armyworm Spodoptera frugiperda ( S. frugiperda ) was found to invade China in 2019 and has since seriously threatened multiple crops, particularly maize and rice. However, the chemical and molecular mechanisms underlying oviposition preference in this pest are not fully understood. Here, the oviposition preference of S. frugiperda on maize and rice plants was investigated. Results GC-EAD and GC–MS/MS techniques were used to identify the antennally active volatiles from maize and rice plants. The attraction and oviposition stimulation of identified components to female adults were tested in both laboratory and field settings. The odorant receptors (ORs) on female antennae were expressed in Xenopus oocytes , and their functions evaluated by RNAi. Ten and eleven compounds of maize and rice plants, respectively, were identified to possess electrophysiological activity from headspace volatiles. Among these compounds, ( Z )-3-hexenyl-acetate specifically presented in maize volatiles was found to play a critical role in attracting females and stimulating oviposition compared to rice volatiles. Among the cloned ORs on the antennae of both sexes, SfruOR23 with highly female-biased expression mediated the responses of females to ( Z )-3-hexenyl-acetate. Knockdown of SfruOR23 using RNAi markedly reduced the electrophysiological response of female antennae and oviposition preference to the compound. Conclusions ( Z )-3-Hexenyl-acetate is a key volatile mediating the host and oviposition preference of S. frugiperda on maize. The olfactory receptor of ( Z )-3-hexenyl-acetate was identified to be SfruOR23 , which is mainly expressed in the antennae of S. frugiperda .

Odontothrips loti (Haliday) (Thysanoptera: Thripidae) is one of the most serious pests on alfalfa, causing direct damage by feeding and indirect damage by transmitting plant viruses. This damage causes significant loss in alfalfa production. Semiochemicals offer opportunities to develop new approaches to thrips management. In this study, behavioral responses of female and male adults of O. loti to headspace volatiles from live female and male conspecifics were tested in a Y-tube olfactometer. The results showed that both male and female adults of O. loti were attracted to the odors released by conspecific males but not those released by females. Headspace volatiles released by female and male adults were collected using headspace solid-phase microextraction (HS-SPME). The active compound in the volatiles was identified by gas chromatography-mass spectrometry (GC-MS). The analysis showed that there was one major compound, (R)-lavandulyl (R)-2-methylbutanoate. The attractive activity of the synthetic aggregation pheromone compound was tested under laboratory and field conditions. In an olfactometer, both male and female adults showed significant preference for synthetic (R)-lavandulyl (R)-2-methylbutanoate at certain doses. Lures with synthetic (R)-lavandulyl (R)-2-methylbutanoate significantly increased the trap catches of sticky white traps at doses of 40–80 µg in the field. This study confirmed the production of aggregation pheromone by O. loti male adults and identified its active compound as (R)-lavandulyl (R)-2-methylbutanoate, providing a basis for population monitoring and mass trapping of this pest.

The cabbage aphid (Brevicoryne brassicae) is a major pest of kale (Brassica oleraceae var. acephala), an important vegetable that is grown worldwide due to its high nutritional and economic value. Brevicoryne brassicae poses a great challenge to B. oleraceae var. acephala production, causing significant direct and indirect yield losses. Farmers overly rely on synthetic insecticides to manage the pest with limited success owing to its high reproductive behavior and development of resistance. This necessitates a search for sustainable alternatives to mitigate these challenges. This study assessed behavioral responses of B. brassicae to odors from rosemary (Rosmarinus officinalis) and B. oleraceae var. acephala headspace volatiles in a Perspex four-arm olfactometer. We identified and quantified volatiles emitted by each of the two plants and those eliciting antennal response using coupled gas chromatography-mass spectrometry (GC-MS) and GC-electroantennograhic detection(GC-EAD), respectively. Our findings revealed that B. brassicae spent more time in the arms of the olfactometer that contained B. oleraceae var. acephala volatiles compared to the arm that held R. officinalis volatiles. Additionally, B. brassicae spent more time in the olfactometer arms with B. oleracea var. acephala compared to the arms holding B. oleracea var. acephala and R. officinalis enclosed together and clean air. GC-MS analysis revealed diverse and higher quantities of volatile compounds in R. officinalis compared to B. oleraceae var. acephala. GC-EAD analysis showed that antennae of B. brassicae detected Linalool, α-Terpineol, Verbenone, Geraniol, Camphor, and Borneol from the volatiles of R. officinalis, and Sabinene, γ-Terpinene, and β-Caryophyllene from B. oleraceae var. acephala volatiles. Our findings demonstrate the potential of R. officinalis as a repellent plant against B. brassicae and could be utilized as a ‘push’ plant in an intercropping strategy against this pest.

In response to attack by herbivorous insects, plants produce semiochemicals for intra- and interspecific communication. The perception of these semiochemicals by conspecifics of the herbivore defines their choice for oviposition and feeding. We aimed to investigate the role of herbivore-induced plant volatiles (HIPVs) by Tuta absoluta larvae on the oviposition choice of conspecific females on tomato plants. We performed two- choice and non-choice bioassays with plants damaged by larvae feeding and intact control plants. We also collected headspace volatiles of those plants and tested the response of female antennae on those blends with Gas Chromatography- Electro-Antennographical Detection (GC-EAD). In total 55 compounds were collected from the headspace of T. absoluta larvae-infested plants. Our results show that female moths preferred to oviposit on intact control plants instead of damaged ones. Herbivory induced the emission of hexanal, (Ζ)-3-hexen-1-ol, (E)-β-ocimene, linalool, (Z)-3-hexenyl butanoate, methyl salicylate, indole, nerolidol, guaidiene-6,9, β-pinene, β-myrcene, α-terpinene, hexenyl hexanoate, β-elemene, β-caryophyllene and (Ε-Ε)- 4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), one unidentified sesquiterpene and three unknown compounds. In Electroantennographic (EAG) assays, the antennae of T. absoluta females responded to hexanal, (Ζ)-3-hexen-1-ol, methyl salicylate and indole. The antennae of T. absoluta females exhibited a dose-response in EAG studies with authentic samples. Strong EAG responses were obtained for compounds induced on damaged tomato plants, as well as in nonanal, a compound emitted by both infested and control plants. These compounds could be utilized in integrated pest management of T. absoluta.

Complex inter-organismal communication among plants, insects, and microbes in natural and agricultural ecological systems is typically governed by emitted and perceived semiochemicals. To understand and ultimately utilize the role of volatile semiochemicals in these interactions, headspace volatiles are routinely collected and analyzed. Numerous collection systems are available (e.g., static or dynamic; adsorption or absorption) where the choice of technique should be dependent upon the plant, insect, or microbial ecological system studied, the information sought, and the limitations of each method. Within these constraints, it remains necessary that each method detects and provides the accurate in situ, or in vitro, volatile profile of the studied system. Herein, we analyzed and compared the pros and cons of three solventless, thermal desorption systems (SPME, Tenax/cold trap, SPDE) using a synthetic standard blend of compounds mimicking a simple natural blend (benzaldehyde, b-caryophyllene, (Z)-3-hexenol, 6-methyl-5-hepten-2-one, and limonene). Direct splitless injection and Super Q collections of the standard blend were used as controls. The results indicated that related qualitative, as well as quantitative differences, could be correlated with adsorbent sampling capacity and structural bias. The results for Tenax/cold trap and SPDE also were affected by sampled headspace volumes. All solventless techniques exhibited high analytical reproducibility, with SPME and SPDE providing ease of use, low cost, and minimal instrument modifications. The more complex Tenax/cold trap technique provided higher collection efficiency. Using these results, we provide guidance for technique selection for chemical communication applications

Wireworms, the larvae of click beetles (Coleoptera: Elateridae), are soil-dwelling insect pests inflicting major economic damage on many types of agricultural crops worldwide. The objective of this work was to identify the female-produced sex pheromones of the Pacific Coast wireworm, Limonius canus LeConte, and the sugarbeet wireworm, L. californicus (Mannerheim) (Coleoptera: Elateridae). Headspace volatiles from separate groups of female L. canus and L. californicus were collected on Porapak Q and analyzed by gas chromatography with electroantennographic detection (GC-EAD) and GC-mass spectrometry. GC-EAD recordings revealed strong responses from male L. canus and male L. californicus antennae to the same compound, which appeared below GC detection threshold. The structure of this candidate pheromone component was deduced from the results of micro-analytical treatments of extracts, retention index calculations on four GC columns, and by syntheses of more than 25 model compounds which were assessed for their GC retention characteristics and electrophysiological activity. The EAD-active compound was identified as (E)-4-ethyloct-4-enoic acid, which we name limoniic acid. In field experiments in British Columbia and Alberta, Canada, traps baited with synthetic limoniic acid captured large numbers of male Limonius click beetles, whereas unbaited control traps captured few. Compared to traps baited with the analogue, (E)-5-ethyloct-4-enoic acid, traps baited with limoniic acid captured 9-times more male L. californicus, and 6.5-times more male western field wireworms, L. infuscatus Motschulsky, but 2.3-times fewer male L. canus. Limoniic acid can now be developed for detection, monitoring and possibly control of L. californicus, L. infuscatus and L. canus populations.

Performed phytochemical study contributes to the knowledge of volatile organic compounds (VOCs) of Halopteris filicina (Grateloup) Kützing, Dictyota dichotoma (Hudson) J. V. Lamouroux, Posidonia oceanica (L.) Delile and Flabellia petiolata (Turra) Nizamuddin from the Adriatic Sea (single point collection). VOCs were investigated by headspace solid-phase microextraction (HS-SPME) and analysed by gas chromatography and mass spectrometry (GC-MS/FID). H. filicina headspace contained dimethyl sulfide (DMS; 12.8%), C8-compounds (e.g. fucoserratene (I; 9.5%)), benzaldehyde (II; 8.7%), alkane C17, dictyopterene D and C (III, IV), tribromomethane (V), 1-iodopentane, others. F. petiolata headspace was characterized by DMS (22.2%), 6-methylhept-5-en-2-one (9.5%), C17 (9.1%), II (6.5%), compounds I-V. DMS (59.3%), C15 (14.5%), C17 (7.2%) and C19 (6.3%) dominated in P. oceanica headspace. Sesquiterpenes were found in D. dichotoma, predominantly germacrene D (28.3%) followed by other cadinenyl (abundant), muurolenyl and amorphenyl structures. Determined VOCs may be significant for chemosystematics and chemical communications in marine ecosystem.