Repellent Effect and Metabolite Volatile Profile of the Essential Oil of Achillea millefolium Against Aegorhinus nodipennis (Hope) (Coleoptera: Curculionidae)

Composition and Biological Activity of the Essential Oils from Wild Horsemint, Yarrow, and Yampah from Subalpine Meadows in Southwestern Montana: Immunomodulatory Activity of Dillapiole

Agastache urticifolia (Benth.) Kuntze (horsemint), Achillea millefolium L. (yarrow), and Perideridia gairdneri (Hook. & Arn.) Mathias (yampah) are native, culturally important plants that grow in the subalpine meadows of Montana. Analysis of the composition of essential oils extracted from these plants showed that the main components of essential oils obtained from flowers and leaves of A. urticifolia (designated as AUF/AUL) were menthone (2.7/25.7%), isomenthone (2.6/29.1%), pulegone (78.9/28.8%), and limonene (4.2/6.2%), whereas essential oils obtained from the inflorescence of A. millefolium (designated as AMI) were high in α-thujone (17.1%) and β-thujone (14.9%), 1,8-cineole (17.0%), camphor (13.0%), sabinene (7.0%), guaia-3,9-dien-11-ol (3.2%), and terpinen-4-ol (2.5%). Essential oils obtained from the inflorescence of P. gairdneri (designated as PGI) contained high amounts of dillapiole (30.3%), p-cymen-8-ol (14.1%), terpinolene (12.0%), 4-hydroxy-4-methyl-cyclohex-2-enone (6.2%), and γ-terpinene (2.4%). Evaluation of their immunomodulatory activity demonstrated that essential oils extracted from all of these plants could activate human neutrophils with varying efficacy. Analysis of individual components showed that dillapiole activated human neutrophil intracellular Ca²⁺ flux ([Ca²⁺]_i) (EC₅₀ = 19.3 ± 1.4 μM), while α-thujone, β-thujone, menthone, isomenthone, and pulegone were inactive. Since dillapiole activated neutrophils, we also evaluated if it was able to down-regulate neutrophil responses to subsequent agonist activation and found that pretreatment with dillapiole inhibited neutrophil activation by the chemoattractant fMLF (IC₅₀ = 34.3 ± 2.1 μM). Pretreatment with P. gairdneri essential oil or dillapiole also inhibited neutrophil chemotaxis induced by fMLF, suggesting these treatments could down-regulate human neutrophil responses to inflammatory chemoattractants. Thus, dillapiole may be a novel modulator of human neutrophil function.

Common yarrow (Achillea millefolium) essential oil and main components as potential repellents and acaricides against Ixodes scapularis and Dermacentor variabilis (Acari: Ixodidae) ticks

Repellent and acaricidal activities of essential oils (EO) extracted from common yarrow (Achillea millefolium L.) and main chemical components were evaluated against Ixodes scapularis and Dermacentor variabilis adult ticks and nymphs. Flowers and leaves were collected from two locations, Harvest Moon trail (HMT) and Port Williams (PW) in Nova Scotia (Canada), and EO were extracted via hydro-distillation. Samples were analyzed using GC-MS, and differences in chemical composition and quantity of compounds detected were reported in relation to the collection site and plant parts. EO were both rich in germacrene D (HMT EO 21.5 ± 1.31% wt; PW EO 25.5 ± 0.76% wt); however, HMT flower EO has a higher concentration of camphor (9.9 ± 0.08% wt) compared to PW flower EO (3.0 ± 0.01% wt). Significant acaricidal activity was reported against I. scapularis adult ticks, particularly for HMT flower EO with a LD₅₀ of 2.4% v/v (95% confidence interval = 1.74-3.35) at 24 h post-exposure. Germacrene D had the lowest LD₅₀ of 2.0% v/v (95% CI 1.45-2.58) among the four compounds after 7 days. No significant acaricidal effect was observed on D. variabilis adult ticks. Yarrow PW flower EO exerted repellent activity towards I. scapularis nymphs (100% repellency up to 30 min); however, repellency significantly declined over time. Yarrow EO exert promising acaricidal and repellent properties, that may be used to manage Ixodes ticks and the diseases they vector.

Pure Camphor and a Thujone-Camphor Mixture as Eco-Friendly Antifeedants against Larvae and Adults of the Colorado Potato Beetle

The Colorado potato beetle (CPB) is a serious pest of economically important Solanaceae species. The use of essential oil compounds in pest management has been proposed as an alternative to harmful chemical insecticides that disturb human health and ecosystem functioning. We examined the antifeedant activity of three concentrations (0.125%, 0.25% and 0.5%) of pure camphor and a thujone-camphor mixture against 3rd instar larvae and adults. Their efficacy was evaluated according to the degree of leaf damage and avoidance of treated leaves by the CPB. Treatment of potato leaves significantly reduced leaf damage compared to the control. Leaf protection increased at higher concentrations of the examined compounds. Camphor was more effective against larvae and the thujone-camphor mixture was more effective against adults. Additionally, adults moved faster towards the control leaf disc in the two-choice olfactometer assay if an alternative disc was treated with a thujone-camphor mixture, whereas larvae responded similarly to the two potential repellents. However, after contact with the leaf disc treated with the highest compound concentration, the larvae escaped faster from the thujone-camphor mixture than from pure camphor. In conclusion, both examined compounds are promising eco-friendly antifeedants, but their efficacy depends on the developmental stage of the beetle, compound type and applied concentration.

Exploring the Antioxidant and Bioinsecticidal Activity of Spontaneous Flora Vegetal Extracts for Plant Protection and Prevention of Soil Contamination

The purpose of this article was to evaluate the application of different plant extracts with bioinsecticidal action and antioxidant activity for plants and soil protection, by substitution of the application of synthetically formulated pesticides with eco-friendly compounds. In this framework, this research focused on the utilization of plant extracts from the spontaneous flora of Moldova (Romania) as bioinsecticides for the control of field pests of the species Leptinotarsa decemlineata and their antioxidant activity. Plant extracts of oregano (Origanum vulgare), yarrow (Achillea millefolium), wormwood (Artemisia absinthium), and cowslip (Primula veris) were assessed for their antioxidant activity by the microplate spectrophotometric-based method (for polyphenols and flavonoids content and for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenger activity) and were characterized by FTIR spectroscopy spectra. To evaluate the bioinsecticidal properties of the plant extracts, the mortality (%) and neuroleptic manifestations appearing in the middle of the monitoring period for larvae and adults of the Leptinotarsa decemlineata species were identified. Mortality (%) was statistically analyzed using a one-way analysis of variance (ANOVA) and the resulting experimental results were compared with the LSD-Fisher’s test (p < 0.05). The highest mortality (%) was observed after 24 h of treatment with extracts of Origanum vulgare at 100% concentration, while the maximum effect was recorded after 48 h for Origanum vulgare at 60% and 100% concentrations.

Volatile-Mediated Induced and Passively Acquired Resistance in Sagebrush (Artemisia tridentata)

Plants produce a diversity of secondary metabolites including volatile organic compounds. Some species show discrete variation in these volatile compounds such that individuals within a population can be grouped into distinct chemotypes. A few studies reported that volatile-mediated induced resistance is more effective between plants belonging to the same chemotype and that chemotypes are heritable. The authors concluded that the ability of plants to differentially respond to cues from related individuals that share the same chemotype is a form of kin recognition. These studies assumed plants were actively responding but did not test the mechanism of resistance. A similar result was possible through the passive adsorption and reemission of repellent or toxic VOCs by plants exposed to damage-induced plant volatiles (DIPVs). Here we conducted exposure experiments with five chemotypes of sagebrush in growth chambers; undamaged receiver plants were exposed to either filtered air or DIPVs from mechanically wounded branches. Receiver plants exposed to DIPVs experienced less herbivore damage, which was correlated with increased expression of genes involved in plant defense as well as increased emission of repellent VOCs. Plants belonging to two of the five chemotypes exhibited stronger resistance when exposed to DIPVs from plants of the same chemotypes compared to when DIPVs were from plants of a different chemotype. Moreover, some plants passively absorbed DIPVs and reemitted them, potentially conferring associational resistance. These findings support previous work demonstrating that sagebrush plants actively responded to alarm cues and that the strength of their response was dependent on the chemotypes of the plants involved. This study provides further support for kin recognition in plants but also identified volatile-mediated associational resistance as a passively acquired additional defense mechanism in sagebrush.

Evaluation of Drimys winteri (Canelo) Essential Oil as Insecticide against Acanthoscelides obtectus (Coleoptera: Bruchidae) and Aegorhinus superciliosus (Coleoptera: Curculionidae)

Adverse effects caused by synthetic pesticides have increased interest in plant-derived insecticidal compounds, in particular essential oils, as a more compatible and ecofriendly alternative for pest control of economic importance. For this reason, the essential oil isolated from leaves and shoots of Drimys winteri (J.R. Forster & G. Forster)-also named canelo (CEO)-was investigated for its chemical profile and insecticidal action against Acanthoscelides obtectus (Say)-one of the most important post-harvest pests of dry beans in the world-and Aegorhinus superciliosus (Guérin)-a significant pest of fruit trees in Chile. The analysis by gas chromatography, paired with mass spectrometry (GC/MS) determined 56 compounds, corresponding to 92.28% of the detected compounds. Elemol (13.54%), γ-eudesmol (11.42%), β-eudesmol (8.49%), α-eudesmol (6.39%), α-pinene (7.92%) and β-pinene (5.17%) were the most abundant. Regarding the bioactivity of the CEO, the results demonstrated toxicological effects against A. obtectus. A concentration of 158.3 µL L^-1 had a mortality rate of 94% after 24 h exposure. The LC₅₀ and LC₉₀ values at 24 h were 60.1 and 163.0 µL L^-1. Moreover, behavioral bioassays showed a repellent effect against A. superciliosus with a dose of one microliter of CEO. Both sexes of the raspberry weevil stayed for very short times in the treated area with the oil (<0.8 min), showing a homogeneous repellency in the species. The overall data suggest that canelo leaves and shoots essential oil has an insecticide effect and is worth exploring to better understand the synergistic relationship between the compounds present in the essential oil.

β-Thujone and Its Derivatives Modify the Probing Behavior of the Peach Potato Aphid

Thujone is a natural biologically active monoterpene ketone component of essential oils of numerous plants. The aim of the study was to evaluate the effect of β-thujone and β-thujone derivatives bisulfite adduct, lactone, oxime, and lactam application on behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae) during probing and settling. The choice and no-choice tests (aphid settling and Electrical Penetration Graph (EPG), respectively) revealed that stereochemistry of thujone was important for biological activity (β-thujone caused changes in aphid behavior while α-thujone did not) and that cyclopentane ring modifications and functional groups addition gave derivatives that possessed stronger and more durable deterrent effects. The most effective modification was the incorporation of a lactam moiety into the β-thujone molecule. Application of β-thujone lactam limited aphid settling for at least 24 h, caused restlessness in aphids and a delay or failure in reaching phloem phase by M. persicae. β-Thujone lactam can be considered a deterrent of medium potency with activity expressed at preingestive phase of aphid probing. Other compounds did not restrain aphid stylet penetration in non-phloem tissues but slightly limited sap ingestion (lactone, oxime), and restrained aphid settling for a period of less than 24 h (β-Thujone, bisulphite adduct, lactone).

Repellent Activity of the Essential Oil from the Heartwood of Pilgerodendron uviferum (D. Don) Florin against Aegorhinus superciliosus (Coleoptera: Curculionidae)

The weevil Aegorhinus superciliosus Guérin (Coleoptera: Curculionidae), which is endemic to Central-Southern Chile and Argentina, is one of the major berry pests in Chile and the most important pest in the La Araucanía Region (38°44'9″S, 72°35'25″W). Due to the poor effectiveness and problems surrounding the implementation of the traditional control methods using organophosphate and carbamate insecticides, new strategies for controlling this pest are needed. In this communication, we evaluated the behavioral responses of male and female A. superciliosus to volatile compounds released from the essential oil (EO) obtained from the heartwood of Pilgerodendron uviferum (D. Don) Florin using olfactometric bioassays. The composition of the EO was analyzed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). According to these analyses, δ-cadinol (24.16%), cubenol (22.64%), 15-copaenol (15.46%) and δ-cadinene (10.81%) were the principal components of the EO. The Pilgerodendron uviferum EO, which is almost exclusively composed of sesquiterpenes (99.5%), exhibited a repellent effect against A. superciliosus adults, regardless of the sex or concentration used (56.6 mg/cm³ and 1.58 × 10(-2) mg/cm³). The EO has low volatility and greater persistence than the EOs composed of monoterpenes and is considered a good model in the search for raspberry weevil repellents.