Search Results (194)

Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) is an invasive pest that causes significant damage to Brassica crops worldwide. This study evaluated behavioral and toxicological responses of adults B. hilaris to plant volatiles and essential oils (EOs). Y-tube olfactometer assays revealed sex-specific responses to plant-emitted volatiles: females were repelled by Coriandrum sativum and Petroselinum crispum, while males responded to Pelargonium hortorum. Essential oils exhibited non-linear concentration-dependent effects, with C. sativum EO inducing repellency at 40–80 µg/µL and P. hortorum at 160–320 µg/µL. In contrast, repellency index was not influenced by sex, but strongly driven by concentration, with C. sativum and P. hortorum most effective, and P. crispum showing weaker yet consistent responses. Toxicity assays demonstrated greater male susceptibility, with lower LC₅₀ and LC₉₀ values for C. sativum and P. hortorum. Gas chromatography-mass spectrometry (GC-MS) analysis of EOs matrix identified linalool, β-citronellol, trans-geraniol, and myristicin as the predominant constituents. Importantly, repellency occurred at lower concentrations than mortality thresholds, indicating distinct behavioral and physiological mechanisms. These findings support integrating C. sativum and P. hortorum essential oils into sustainable pest management strategies for B. hilaris. Full article

Rhoptroceros cyatheae (Hymenoptera: Selandriidae) is a dominant herbivorous pest of Alsophila spinulosa in southwestern China, including Guizhou and Sichuan provinces. Infestation by this pest impairs spore reproduction of A. spinulosa and reduces the photosynthetic capacity of host plants. However, the chemosensory genes of R. cyatheae have not been reported, and the molecular basis of antennal detection of host volatile organic compounds (VOCs) is poorly understood. This study aims to screen and identify bioactive VOCs potentially involved in host searching behavior of R. cyatheae, analyze antennal VOC detection patterns, and explore the in vitro binding characteristics of an odorant-binding protein (OBP) involved in olfactory recognition, thereby providing a preliminary theoretical basis for the green management of R. cyatheae. Dynamic headspace sampling, gas chromatography-mass spectrometry (GC-MS), and gas chromatography-electroantennography (GC-EAD) were used to measure antennal electrophysiological responses of R. cyatheae to volatiles from its host A. spinulosa. Y-tube olfactometer assays were conducted to evaluate behavioral responses. For RcyaOBP7, fluorescence competitive binding assays, structural modeling, and molecular docking were integrated to investigate its in vitro binding characteristics with nine selected bioactive VOCs. Nine A. spinulosa volatiles were identified that elicited antennal electrophysiological responses in R. cyatheae, and the sawfly showed behavioral orientation to these VOCs, confirming that its antennae can detect host VOCs. In vitro binding assays showed that RcyaOBP7 exhibited strong binding affinity to p-ethylacetophenone, suggesting its potential involvement in antennal olfactory recognition of this volatile. Specific VOCs released by A. spinulosa are among the signaling molecules detected by the antennae of R. cyatheae. In vitro findings indicate that RcyaOBP7 binds specifically to p-ethylacetophenone, suggesting a possible role in antennal olfactory recognition and behaviors such as host location. However, in vivo functional validation and field trials under ecologically relevant conditions are needed to confirm these roles. This study characterizes the in vitro binding properties of RcyaOBP7 and provides a basis for further research on green management strategies for R. cyatheae based on antennal olfactory signals. Full article

Butterflies locate host sites using plant volatiles, while larval frass cues induce avoidance. This study investigated the olfactory responses of adult Papilio polytes to nine shared plant and frass volatiles across 1 × 10³ to 1 × 10⁶ ng load doses using electroantennography (EAG) and Y-tube olfactometer assays. EAG responses were significantly influenced by chemical composition, dose, and sex, as well as all their interactions. In contrast, behavioral choices were significantly driven only by chemical composition and its interaction with dose. Although females exhibited higher peripheral sensitivity than males, this physiological sexual dimorphism did not result in significant behavioral differences. Linalool, citronellal, and geraniol were identified as the most potent elicitors. While their single forms and binary blends elicited attraction or neutrality, the ternary mixture significantly repelled both sexes. These results demonstrate that VOC blend composition determines the direction of behavioral responses, with linalool playing a pivotal role in the transition from attraction to avoidance. These findings highlight the importance of shared plant–frass VOCs in host selection by oligophagous insects and provide a foundation for manipulating P. polytes behavior. Full article

Plant volatiles are critical mediators of insect–plant interactions, guiding natural enemies to specific habitats and prey. The flower bug, Orius maxidentex Ghauri (Hemiptera: Anthocoridae), is a generalist predator that exhibits a specialized ecological association with the weed Celosia argentea L. (Caryophyllales: Amaranthaceae), utilizing the plant as a primary floral niche in Hainan Island. In this study, the attractiveness of C. argentea floral volatiles to O. maxidentex was confirmed using a Y-tube olfactometer. Solid-phase microextraction (SPME) combined with gas chromatography–mass spectrometry (GC-MS) was utilized to identify six compounds in the floral volatiles: 1,3-diethenylbenzene, trans-cinnamaldehyde, β-bisabolene, methyl salicylate, 3-ethylbenzaldehyde, and nonanal. Electroantennogram (EAG) assays revealed that O. maxidentex antennae showed significant physiological responses to these compounds, and the EAG relative values were positively correlated with concentration gradients. Furthermore, O. maxidentex exhibited significant orientation responses to 1,3-diethenylbenzene, trans-cinnamaldehyde, β-bisabolene, and methyl salicylate, whereas no behavioral response was observed for 3-ethylbenzaldehyde or nonanal. Further tests revealed that β-bisabolene elicited the highest attractiveness, comparable to a synthetic blend formulated to mimic the natural release ratio of the active semiochemicals. These findings reveal the hidden chemical cues mediating the interaction between a predator and its preferred habitat. Understanding this mechanism not only helps explain insect adaptation but also offers new strategies for using these plant volatiles to influence the behavior of this specific predator, potentially enhancing its targeted recruitment in agroecosystems. Full article

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the vector of the devastating citrus disease Huanglongbing, posing a significant threat to the global citrus industry and necessitating environmentally sound management strategies. This study aimed to evaluate Australian tea tree oil (TTO) and its primary constituents as potential botanical insecticides. Gas chromatography-mass spectrometry (GC-MS) was performed to analyze the chemical profile of commercial TTO, and behavioral effects on D. citri adults were assessed using a Y-tube olfactometer. Direct spray bioassays were conducted to determine contact toxicity. A total of 12 compounds were identified, with TTO being a Terpinen-4-ol chemotype, dominated by Terpinen-4-ol (40.62%), γ-Terpinene (21.46%), and α-Terpinene (10.45%). TTO demonstrated potent, concentration-dependent repellency, achieving 100% repellency at 10 g/L. In contrast, Terpinen-4-ol alone was attractive to psyllids at low concentrations, suggesting synergistic or masking effects within the complex oil blend. TTO and its major constituents also exhibited significant dose- and time-dependent contact toxicity. Although the 72 h LC₅₀ of TTO (19.18 g/L) indicates lower potency compared to conventional insecticides (0.59–1.23 g/L), its combined repellent and toxic properties make it a promising candidate for integrated pest management (IPM) programs aimed at controlling D. citri and mitigating insecticide resistance. Full article

Although Telenomus remus is an important parasitoid of Spodoptera frugiperda, the chemical basis for its host selection behavior remains unclear. To elucidate the chemical basis of this behavior, this study combined behavioral ecology and chemical ecology methods to systematically investigate the host location and recognition behaviors of this wasp, as well as the semiochemicals that regulate these behaviors. In Y-tube olfactometer assays, T. remus exhibited a significantly stronger olfactory preference for eggs of S. frugiperda over those of S. litura (p < 0.05) or the non-host Ostrinia furnacalis. A total of 759 metabolites belonging to 11 categories were identified via metabolomics analysis, and principal component analysis (PCA) clearly distinguished between host eggs and non-host eggs. Analysis of differential metabolites revealed that the significantly upregulated metabolites in host eggs mainly included aldehydes, ketones and esters, followed by hydrocarbons, alcohols and amines. Subsequently, we screened and verified the effects of the significantly upregulated metabolites in host eggs compared with non-host eggs on the host-selection behavior of T. remus, including indole, 2-hexanol, and trans-1,2-dimethylcyclohexane, as well as 2-heptadecanone and n-nonadecane—two alkane compounds which are specifically upregulated on the surface of S. frugiperda eggs. Behavioral validation demonstrated that 2-hexanol exerted a significant repellent effect on T. remus, whereas trans-1,2-dimethylcyclohexane exhibited a significant attractive effect on the parasitoid wasp. Among the metabolites specifically upregulated in S. frugiperda eggs, 2-heptadecanone exhibited significant attractive activity at concentrations ranging from 0.1 to 1.0 mg/mL. This study is the first to report that the cycloalkane compound trans-1,2-dimethylcyclohexane acts as a potential broad-spectrum chemical marker for T. remus to recognize the eggs of host species belonging to the family Noctuidae, while 2-heptadecanone may further enhance its preference for the optimal host S. frugiperda. These findings provide novel candidate molecular targets for the development of behavioral regulators targeting egg parasitoids against S. frugiperda. Full article

Plutella xylostella (L.) (Lepidoptera: Plutellidae), the diamondback moth (DBM), is a cosmopolitan pest of brassicas. To validate and compare the performance of yeast-derived sex pheromone components with chemically synthesized ones, we studied the behavioral and electrophysiological responses (EAGs) of male DBM adults. In addition, using gas chromatography coupled with electroantennographic detection (GC-EAD), we examined whether any residual impurities present in yeast-derived pheromone components can be perceived by the insects’ antennae and are thus capable of interfering with normal behavior. Furthermore, we assessed the performance of the yeast-derived pheromones under field conditions through monitoring trials conducted in cabbage crops in Greece. Electrophysiological and behavioral assays revealed equivalent responses from the insects to both the yeast-derived (BIO) and chemically synthesized (CHEM) pheromone blends. Consistent with this, GC-EAD results showed no significant differences in antennal response to minor impurities present in the BIO blend compared to the CHEM blend. Finally, it was demonstrated that the binary pheromone blend—comprising (Z)-11-hexadecenal and (Z)-11-hexadecenyl acetate derived from (Z)-11-hexadecen-1-ol produced by yeast cell-factories—was as efficient and specific for trapping male moths in cabbage fields as the conventional ternary synthetic blend [(Z)-11-hexadecenal and (Z)-11-hexadecenyl acetate and (Z)-11-hexadecen-1-ol]. The yeast-derived mixture contained small amounts of unoxidized (Z)-11-hexadecen-1-ol due to incomplete oxidation. Full article

Rice volatiles play a crucial role in mediating resistance to the brown planthopper (Nilaparvata lugens Stål, Hemiptera: Delphacidae), a major pest of rice crops. In this study, we analyzed secondary metabolites from rice plants to identify compounds associated with insect behavior. A total of 31 volatile metabolites were detected, among which 16 differed significantly between 51 resistant or susceptible varieties. Fifteen volatiles were more abundant in susceptible plants, while one was enriched in resistant varieties. Electrophysiological (EAG) and Y-tube olfactometer assays revealed that both male and female adults exhibited positive chemotaxis toward five volatiles: Cyclohexanone, 2,2,6-trimethyl-; 3-Cyclohexen-1-one, 3,5,5-trimethyl-; (+)-Isomenthol; Benzoic acid, 2-hydroxy-, methyl ester; and 2-Methoxy-4-vinylphenol. In contrast, male adults were repelled by Benzaldehyde, 3-ethyl-, and 3-Buten-2-one, 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-. These results indicate that characteristic volatiles serve as functional cues for host selection and may act as phytochemical markers for assessing rice resistance. The findings provide new insights into plant–insect chemical interactions and suggest potential strategies for environmentally friendly pest management, including the use of attractant- or repellent-based approaches and breeding for optimized volatile profiles to control N. lugens. Full article

Volatile organic substances (VOCs) emitted by plants play an important role in the recognition and selection of host plants by insects. For polyphagous insects with a broad host range, like the brown marmorated stink bug Halyomorpha halys, not much is known about the plant volatiles that influence host choice. In order to determine which odour stimuli could influence host selection, monitoring was carried out using pheromone traps in orchards with various host plants. The headspace of the phenological stages of plants on which H. halys occurred in large numbers was sampled and analysed with gas chromatography coupled with mass spectrometry (GC-MS). The volatile profiles of the different host plants varied significantly. Some compounds occurred in high relative proportions across all taxa. Those compounds were tested by H. halys using electroantennography. H. halys’ antennae responded significantly to all of the selected compounds. In a Y-tube olfactometer, H. halys showed a significant attraction to 1 µg hexanal, 100 µg (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), and a volatile mixture. Due to the limited sustainable strategies for plant protection against this polyphagous insect, adding attractive plant volatiles to lures could improve the effectiveness of alternative volatile-based plant protection strategies, such as traps or capsules, or promote their development. Full article

The citrus spiny whitefly, Aleurocanthus spiniferus Quaintance (Hemiptera: Aleyrodidae), is an important pest of tea, Camellia sinensis (L.) Kuntze (Theales: Theaceae). Parasitic wasp, Encarsia smithi Silvestri (Hymenoptera: Aphelinidae), is one of the dominant natural enemies of the whitefly. Generally, the whitefly produces four generations per year in Chinese tea plant growing areas. The wasp adult stages are basically synchronized with the nymphal stages of the whitefly. In an indoor Y-tube olfactometer bioassay, odors from both whitefly-pierced tea leaves and adjacent intact tea leaves significantly attracted the wasps, with elevated amounts of trans-2-hexenal and methyl salicylate (MeSA) detected from these two types of tea leaves. A four-arm olfactometer bioassay verified that these two compounds and their binary blends significantly attracted the wasps. Bud green sticky boards baited with trans-2-hexenal (10⁻² g mL⁻¹), MeSA (10⁻² g mL⁻¹), and five blends of trans-2-hexenal and MeSA (1:1, 2:1, 3:1, 4:1 and 5:1, respectively, v/v) at 10⁻² g mL⁻¹ in hexane solutions captured significantly more wasps than did the un-baited boards, with the 3:1 blend catching the highest number of wasps. To enhance whitefly parasitism by the wasps, from early April to early August, the Attractant 2 lures (each holding a total mass of 80 mg of the 3:1 blend) were hung on tea branches and refreshed every 30 days. Deployment of the controlled release synomone-based attractant lures resulted in 2–3 fold higher parasitism rates by the wasps in the treated plots/sections than those in the CK plots/sections during both the peak periods of whitefly pupae of generation 2 from late July to early August and generation 3 in late August. This study demonstrated that herbivore-induced tea volatiles can be formulated as a synomone-based lure for controlling the whitefly through attracting E. smithi in tea plantations. Full article

Species sharing the same trophic level can interact not only through competition for resources but also through intraguild predation (IGP). Therefore, an important step toward implementing successful multiple predator releases in biological control strategies requires resolving how predators respond to the presence of heterogeneous competitors. This study examined the compatibility of two predatory mites, N. californicus and P. persimilis, which are both widely employed to suppress two-spotted spider mite populations in greenhouses and open fields. The experiments quantified the frequency and intensity of IGP across different developmental stages of these species on bean leaves, considering scenarios both with and without their shared prey being present. Additionally, a Y-tube olfactometer was employed to assess whether either predator avoided prey patches previously occupied by other heterospecifics, thereby providing insights into potential chemical cues that influence predator behavior. The results revealed that adult females of both predatory mite species predominantly targeted heterospecific eggs and larvae, whereas adults were largely avoided. In the absence of shared prey, N. californicus attacked 83% of the P. persimilis larvae and 37% of the eggs, whereas P. persimilis consumed 67% of the N. californicus eggs. The presence of shared prey reduced IGP risk by approximately 60%. Olfactometer assays revealed no significant avoidance of plants inhabited by heterospecifics at densities of 20 or 40 adults; both predators were similarly attracted to herbivore-induced volatiles. Generalized linear models indicated that host plant experience had a significant influence on the foraging response of N. californicus, whereas the effects of the feeding state weakened over time. Understanding predator foraging plasticity and responsiveness to chemical cues can help optimize biological control strategies in complex agroecosystems. Full article

Canine ehrlichiosis, caused by Ehrlichia canis, represents a relevant challenge in veterinary medicine, particularly in resource-limited settings where access to laboratory-based diagnostics may be constrained. This pilot and exploratory study aimed to evaluate the feasibility of a portable electronic olfactometer as a non-invasive screening approach, based on the analysis of volatile organic compounds (VOCs) present in breath, saliva, and hair samples from dogs. Signals were acquired using an array of eight metal-oxide (MOX) gas sensors (MQ and TGS series). After preprocessing, principal component analysis (PCA) was applied for dimensionality reduction, and the resulting features were analyzed using supervised machine-learning classifiers, including AdaBoost, support vector machines (SVM), k-nearest neighbors (k-NN), and Random Forests (RF). A total of 38 dogs (19 PCR-confirmed infected cases and 19 controls) were analyzed, generating 114 samples evenly distributed across the three biological matrices. Among the evaluated models, SVM showed the most consistent performance, particularly for saliva samples, achieving an accuracy, sensitivity, and precision of 94.7% (AUC = 0.964). In contrast, breath and hair samples showed lower discriminative performance. Given the limited sample size and the exploratory nature of the study, these results should be interpreted as preliminary; nevertheless, they suggest that electronic olfactometry may represent a complementary, low-cost, non-invasive screening tool for future research on canine ehrlichiosis, rather than a standalone diagnostic method. Full article

This study aims to develop a novel high-efficiency lure for Tomicus yunnanensis Existing bark beetle attractants often rely on single or fixed-ratio blends of host volatiles and their oxidation products, which struggle to mimic the dynamic release process of insect semiochemicals in nature. To address this, we established a dynamic reaction system based on the catalytic oxidation of α-pinene: ① background control (no catalyst, no heating), ② thermal oxidation system (no catalyst, 40 °C), and ③ catalytic oxidation system (with a titanium–copper modified chabazite-type zeolite catalyst, 40 °C). Behavioral screening using a Y-tube olfactometer revealed a clear gradient in attraction effectiveness among the three systems: catalytic oxidation > thermal oxidation > background control. The products from the catalytic oxidation system at 2 h of reaction showed the highest efficacy, achieving an attraction rate of 61%, which was significantly superior to the α-pinene control. These results indicate that generating dynamically proportioned volatile mixtures through catalytic oxidation can significantly enhance the attraction of T. yunnanensis Further analysis by gas chromatography–mass spectrometry (GC-MS) demonstrated that the catalyst efficiently promoted the directional conversion of α-pinene into key bioactive compounds such as verbenol, myrtenal, and myrtenone, thereby substantially improving behavioral activity. After field validation, this dynamically released attractant could potentially be developed into a real-time field-release lure system for monitoring adult emergence and large-scale trapping, providing a feasible new technological pathway for the precise and sustained management of bark beetle pests. Full article

Background: Recently, the use of volatile compounds as spatial repellents have received special attention as a promising strategy for adult An. gambiae s.l control. Anopheles gambiae s.l is a primary vector of malaria, an arthropod-borne disease of global significance. Current strategies for controlling mosquitoes heavily rely on vector control methods. Understanding the responses of these vectors to volatile compounds will be helpful in the formulation of repellants or attractants for control vector populations. This study was conducted in Nwoya district, Uganda, one of the high-malaria-transmission areas in the northern part of Uganda, as one of the ways of reducing contact between the parasite, vector, and malaria outbreak. Materials and Methods: In this study, a laboratory-reared female An. gambiae Kisumu strain from Uganda Virus Research Institute (UVRI) insectaries were used to examine spatial behavior responses of An. gambiae to selected EOs of Eucalyptus grandis and Cymbopogon citratus. Spatial activity responses were measured using a Y-tube olfactometer under controlled conditions using three replicates in various concentrations of the tested EOs. These oils were extracted by steam distillation and the main constituents identified using gas chromatography–mass spectrometry. Results: Mosquito response curves indicating effective repellency concentrations are reported, as well as the gas chromatography–mass spectrophotometry analysis results. For Eucalyptus grandis, the two components with the highest composition were L-α terpineol and Eucalyptol, while those for Cymbopogon citratus were Lavandulol, methyl ether, and citral. Other components had a percentage composition less than five but they might play a big role in repellent activity against mosquito species. Conclusions: The mosquito repellency results in this study indicate that Eucalyptus grandis and Cymbopogon citratus EOs could be used as mosquito repellents, providing more evidence that natural products have promising lead compounds for further development of botanical spatial repellents. Further characterization of EOs and testing on mosquito behavior related to the prevention of malaria and other vector-borne diseases will promote innovation in vector control and provide new vector control tools that are needed in this era of insecticide resistance. Full article

Hemipteran insects such as Euschistus heros and Dysdercus peruvianus are important pests of soybean and cotton, respectively, making them relevant targets in pest management programs. This work aims to evaluate the insecticidal and chemical activity of Cymbopogon citratus essential oil (CC-EO) and its nanoemulsion against E. heros and D. peruvianus. A mixture of citral stereoisomers (59.5%) was identified as the major constituent of CC-EO The topical application of nanoemulsion resulted in 53.33% and 33.33% mortality in E. heros and D. peruvianus, respectively. Contact treatment caused 83.33% mortality in E. heros and 86.70% mortality in D. peruvianus, also inducing antennal deformities observed by scanning electron microscopy and reflected in altered behavioral responses in a Y-tube olfactometer assay. Ovicidal effects were observed in contact treatment for both species, affecting nymph emergence from eggs treated with nanoemulsion. Treatments with pure EO resulted in 100% nymph mortality and complete inhibition of egg hatching in both insects. Headspace solid-phase microextraction (HS-SPME) analysis revealed changes in the volatile profile of treated insects, showing the presence of semiochemicals related to defense and alarm, such as terpenes and alcohols. The multiple lethal and sublethal effects demonstrated by CC-EO highlight its potential as a candidate for integrated pest management programs, offering an eco-friendly alternative to conventional chemical control methods. Full article