Acaricidal Activity Of Essential Oils Research Articles

In vitro acaricidal activity of essential oils and their binary mixtures against ixodes scapularis (Acari: Ixodidae)

Ixodes scapularis ticks are vectors of infectious agents that cause illness in humans, including Lyme disease. Recent years have seen a surge in tick-borne diseases (TBD) resulting in a high demand for tick management products. Plants offer a valuable source of active compounds for the development of novel, eco-friendly tick control products, reducing potential risks to human and animal health. Essential oils (EOs) have emerged as potential acaricides and repellents against ticks providing an alternative to synthetic chemicals and aiding in the prevention of TBD by lowering the risk of tick bites. We investigated the acaricidal activity of EOs from lemongrass (Cymbopogon citratus), geranium (Pelargonium x asperum), savory thyme (Thymus saturejoides), and white thyme (Thymus zygis) on I. scapularis. The interactions (i.e., synergistic, antagonistic, or additive) of their binary mixtures were also evaluated. EO samples were analyzed via gas chromatography-mass spectrometry to determine their chemical composition. The adult immersion test was used to determine the lethal concentration (LC50) of each EO alone and in mixtures. Quantitative assessment of synergistic, additive, or antagonistic effect of the binary mixtures was performed by calculating the combination index. Strong acaricidal activity was recorded for savory thyme and white thyme EOs, with LC50 values of 28.0 and 11.0 μg/μL, respectively. The LC50 of lemongrass and geranium EOs were 49.0 and 39.7 μg/μL, respectively. Among the tested EOs, savory thyme and white thyme had a strong acaricidal effect on I. scapularis, which might be linked to the presence of carvacrol (26.05 % ± 0.38) and thymol (53.6 % ± 2.31), main components present in savory thyme and white thyme EOs, respectively. The tick killing efficacy of lemongrass and geranium EOs was lower when mixed than when used separately (LC50 of 65.3 µg/µL). The same happened with savory thyme and white thyme EOs, except at 9.75 µg/µL where they had a synergistic effect (LC50 of 58.3 µg/µL). Lemongrass and savory thyme EOs had a synergistic effect at low concentrations, and an antagonistic effect at higher concentrations (LC50 of 95.4 µg/µL). Lemongrass and white thyme EOs had a synergistic effect against ticks from 15 to 120 µg/µL (LC50 of 18.5 µg/µL) similar to white thyme EO. Geranium and savory thyme EOs had an antagonistic effect at all concentrations, with an LC50 of 66.8 µg/µL. Geranium and white thyme EOs also had an antagonistic effect, except at 12.7 µg/µL where they had a synergistic effect (LC50 of 66.8 µg/µL). The interaction observed when combining selected essential oils suggests promising potential for developing acaricidal formulations aimed at controlling ticks and curbing the transmission of tick-borne disease agents.

Chemical Composition and Acaricidal Activity of Essential Oils from Leaves and Flowers of Ipomoea aegyptia and Ipomoea bahiensis

Chemical Composition and Acaricidal Activity of Essential Oils from Leaves and Flowers of Ipomoea aegyptia and Ipomoea bahiensis

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 24h 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 30min); 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.

Repellent and acaricidal activities of basil (Ocimum basilicum) essential oils and rock dust against Ixodes scapularis and Dermacentor variabilis ticks.

Repellent and acaricidal activity of essential oils extracted from three varieties of basil (Ocimum basilicum L.) were evaluated on blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) in laboratory conditions. Essential oils were extracted and characterized through gas chromatography-mass spectrometry, and tested at different concentrations for long-term repellent activity using horizontal bioassays. In addition, basil essential oils were combined with an inert material (i.e., granite rock dust) with known insecticidal and miticidal properties to assess acaricidal activities against adult ticks. Among the tested basil varieties, var. Jolina essential oil at 15% vol/vol concentration repelled 96% of tested ticks up to 2h post-treatment. The EC50 for I. scapularis nymphs was 4.65% vol/vol (95% confidence interval: 4.73-4.57). In acaricidal tests, the combination of essential oil from var. Aroma 2 at 10% wt/wt with rock dust resulted in 100% tick mortality after only 24h post-exposure, with a LD50 of 3.48% wt/wt (95% CI 4.05-2.91) for freshly prepared treatment tested on I. scapularis adults. The most common compounds detected in basil essential oils by GC-MS were linalool (52.2% in var. Nu Far, 48.2% in Aroma 2, 43.9% in Jolina), sabinene (6.71% in Nu Far, 8.99% in Aroma 2, 8.11% in Jolina), eugenol (11.2% in Jolina, 8.71% in Aroma 2), and estragole (18.2% in Nu Far). The use of essential oils alone and in combination with rock dust provides an innovative and environmentally friendly approach for managing ticks and inhibiting vector-borne disease transmission.

Acaricidal activity of essential oils from Curcuma zedoaria and Alpinia zerumbet rhizomes against Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

ABSTRACT This study aimed to determine the chemical composition and evaluate the acaricidal activity of essential oils (EOs) from Curcuma zedoaria and Alpinia zerumbet rhizomes against Rhipicephalus microplus in vitro. EOs were obtained by hydrodistillation and chemical characterization was performed by gas chromatography coupled with mass spectrometry (GC-MS). The acaricidal activity of each EO was firstly evaluated on larvae by larval packet test at concentrations of 2.5, 5.0, 10.0, and 15.0 mg/mL. Through the result of the treatment on larvae, where only the EO from C. zedoaria caused mortality, it was realized the adult immersion tests at concentrations 10.0, 20.0, 40.0, 60.0, and 80.0 mg/mL for R. microplus engorged females. The GC-MS analysis of EOs showed 1,8-cineole (43.49%), curzerenone (13.40%) and camphor (12.29%) as major components in C. zedoaria, and 4-terpineol (22.27%), 1,8-cineole (16.51%), terpinene (10.75%), p-cymene (9.24%) and sabinene (9.18%) in A. zerumbet. Regarding the acaricidal activity, both in R. microplus larvae and engorged females, only the EO from C. zedoaria was effective, causing 100% larval mortality at a concentration of 15 mg/mL and 98.6% efficacy on engorged females at a concentration of 80 mg/mL. Thus, our results provide support for further investigation of C. zedoaria EO compounds as novel natural products to control R. microplus.

In vitro acaricidal activity of essential oil and crude extracts of Laurus nobilis, (Lauraceae) grown in Tunisia, against arthropod ectoparasites of livestock and poultry: Hyalomma scupense and Dermanyssus gallinae

The current study assayed the toxicity of Laurus nobilis essential oil and crude extracts obtained using solvents of increasing polarity (cyclohexane, acetone and ethanol), on two ectoparasites of veterinary importance, i.e., Hyalomma scupense and Dermanyssus gallinae.The major components detected in bay laurel essential oil were dominated by 1.8-cineole (46.56 %), α-terpinenyl acetate (13.99 %), sabinene (7.69), α-pinene (5.75), linalool (5.50), methyleugenol (5.36 %) and β-pinene (3.97). The highest total phenolic and flavonoids contents were present in the ethalonic extract of L. nobilis leaves at an amount of 152.88 mg gallic acid equivalents per gram of dry weight (GAE/g DW) and 21.77 mg quercetin equivalent per gram of dry weight (QE/g DW), respectively.In vitro acaricidal effects of essensial oil and crude extract of L. nobilis against H. scupense were ascertained by adult immersion test of engorged females (AIT) and larval packet test (LPT) compared with a reference drug amitraz.The essential oil exhibited strong acaricidal activity against tick engorged female and inhibition of hatching eggs. After 24 h of exposure, at the highest tested concentration (100 mg/mL) essential oil induced 90.67 % mortality of H. scupense larvae (LC50 = 10.69 mg/mL). Otherwise, essential oil exhibited high acaricidal activity compared to extracts, and among the extract, the ethanolic extract revealed the highest acaricidal efficacy (81.27 % female mortality).Results from mite contact toxicity showed that essential oil and extracts from L. nobilis were toxic to D. gallinae. Bay essential oil was both more toxic to mites, and faster in exerting this toxicity than other tested crude extracts. L. nobilis essential oil concentration leaded to enhance mortality of D. gallinae reaching the highest (100 %) mortality at 12 h with a concentration of 320 mg/mL. While, ethanolic extract acheived this rate after 24 h of exposure at same concentration. Cyclohexanic extract showed weak acaricidal activity.

Acaricidal activity of essential oils for the control of honeybee (Apis mellifera) mites Tropilaelaps mercedesae under laboratory and colony conditions

Tropilaelaps spp. mites are considered a major parasite of honeybees. In this study, essential oils (EOs) of 11 plant species were evaluated for acaricidal activity under laboratory and field conditions. Five adult mites per petri dish and ten adult worker bees per plastic cup cage were exposed to different concentrations of each essential oil (0.1, 0.5, 1.0, 5.0, and 10.0% (v/v)). The essential oil of Piper betle (betel) showed the highest acaricidal activity in laboratory testing. Additionally, most EOs showed low toxicity to adult honeybees in a lab assay. Piper betle, Amomum krervanh, and Zanthoxylum limonella were then tested in whole colonies using cardboard strips soaked in 10 mL of each essential oil at various concentrations, every week for 4 weeks. Amomum krervanh at 10% (v/v) and P. betel at 5.0% (v/v) decreased mite populations after 30 days. We further tested grease and a sponge as application methods to deliver A. krervanh, with no significant impact on mites. Although several essential oils demonstrated acaricidal activity against Tropilaelaps under laboratory conditions, the EOs tested did not significantly reduce mites under colony conditions. Therefore, the concentration and colony delivery methods of these promising EOs warrant further investigation.

Acaricidal activity of essential oils of Cinnamomum zeylanicum and Eremanthus erythropappus, major compounds and cinnamyl acetate in Rhipicephalus microplus.

This study aimed to chemically characterize the essential oils (EOs) of Cinnamomum zeylanicum (cinnamon) and Eremanthus erythropappus (candeia) and evaluate their acaricidal activity, together with that of their major compounds and cinnamyl acetate derivative, against Rhipicephalus microplus. Essential oil compounds were identified through gas chromatography. The larval packet test (LPT) at concentrations ranging from 0.31 to 10.0 mg/mL and the adult immersion test (AIT) at concentrations between 2.5 and 60.0 mg/mL were performed. (E)-cinnamaldehyde and α-bisabolol were the major compounds in cinnamon (86.93%) and candeia (78.41%) EOs, respectively. In the LPT, the EOs of cinnamon and candeia and the compounds (E)-cinnamaldehyde, α-bisabolol and cinnamyl acetate resulted in 100% mortality at concentrations of 2.5, 2.5, 5.0, 10.0 and 10.0 mg/mL respectively. In the AIT, percentage control values > 95% were observed for cinnamon and candeia EOs, (E)-cinnamaldehyde and α-bisabolol at the concentrations of 5.0, 60.0, 20.0, and 20.0 mg/mL, respectively, whereas cinnamyl acetate showed low activity. We conclude that EOs and their compounds showed high acaricidal activity, whereas the acetylated derivative of (E)-cinnamaldehyde presented less acaricidal activity on R. microplus engorged females.

Chemical composition and acaricidal activity of essential oils from fruits of Illicium verum and rhizomes of Curcuma zedoaria against Dermacentor nitens (Acari: Ixodidae)

ABSTRACT This study aimed to determine the chemical composition of essential oils (EOs) from fruits of Illicium verum and rhizomes of Curcuma zedoaria and evaluate the acaricidal activity against Dermacentor nitens, the tropical horse tick. The EOs were characterized by gas chromatography coupled with mass spectrometry analysis. Mostly, the chemical compounds found were (E)-anethole (88.32%) from I. verum, and 1,8-cineole (43.49%), curzerenone (13.40%) and camphor (12.29%) from C. zedoaria. The acaricidal activity was evaluated on D. nitens engorged females by Adult Immersion Test (AIT) using 40.0 mg mL−1 of each essential oil. Illicium verum EOs showed a high acaricidal activity (89.6%) on the engorged females and also influenced on larvae hatching percent, while C. zedoaria presented low acaricidal activity (4.9%). The present data provide support for further investigation of I. verum EOs components as novel botanical acaricide to control D. nitens infestations.

In vitro acaricidal activity of essential oil and alcoholic extract of Trachyspermum ammi against Dermanyssus gallinae

This study aimed to assess in vitro acaricidal activity of essential oil (EO) and alcoholic extracts (AE) of Ajowan against D. gallinae. Using contact and spraying bioassays, different doses of EO and AE were tested. Cypermethrin and thymol (positive controls), and ethanol and distilled water (negative controls) were also tested. The results indicated that effects were method and dose dependent. Statistical analysis showed a highly significant difference for contact and spraying bioassays and various doses of EO and AE (p < 0.0001) as, the spraying method was more effective than the contact method for acaricidal activity at 24 h post treatment (PT). In this method, Cypermethrin, EO and thymol caused over 90 % mite mortality at 50 μgcm−2, while AE caused this rate at 150 μgcm−2. In the contact bioassay, all tests produced low mortality rates except for Cypermethrin. Thymol was the main constituent of EO (Area = 42.26 %) and AE (Area = 45.8 %). Results of the present study indicated that Ajowan had a satisfactory acaricidal effect against D. gallinae in vitro. It was also found that the spraying method could be used to control the D. gallinae as the most appropriate method.

Chemical profile, characterization and acaricidal activity of essential oils of three plant species and their nanoemulsions against Tyrophagus putrescentiae, a stored-food mite.

Essential oils of Ocimum basilicum (L.), Achillea fragrantissima (Forssk.) and Achillea santolina (L.) were obtained by hydrodistillation and analyzed using gas chromatography (GC) and GC/mass spectrometry (MS). Oil-in-water nanoemulsions (10% active ingredient) were prepared through a high-energy (ultrasonication) emulsification process. Nanoemulsions were characterized by viscosity, pH, thermodynamic stability, droplet size, polydispersity index (PDI) and scanning electron microscopy (SEM) measurements. The plant oils and their nanoemulsions showed considerable acaricidal activity against the mold mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae). In a contact toxicity bioassay and 48h post treatment, O. basilicum oil was the most toxic, followed by A. fragrantissima and A. santolina, where LC50 values were 8.4, 14.1 and 21.8µl/cm2, respectively. LC50 for benzyl benzoate, a standard acaricide was 9.8µl/cm2. Upon fumigation, responses also varied according to the test oil. Based on the 48-h LC50 values, the same manner of activity was also observed, where O. basilicum was the most toxic followed by A. fragrantissima and A. santolina. When prepared as nanoemulsions (particle size from 78.5 to 104.6) and tested as fumigants, toxicity of the oils was increased drastically with LC50 values of 2.2, 4.7, and 9.6µl/l air for O. basilicum, A. fragrantissima and A. santolina, respectively. The oils showed a moderate to strong residual acaricidal activity, where O. basilicum oil was the most effective. The results suggest that appropriate nanoemulsions containing the tested oils can be developed to control T. putrescentiae after the required toxicological assessments.

Chemical composition and acaricidal activity of essential oils from two species of the genus Bauhinia that occur in the Cerrado biome in Brazil

ABSTRACTEssential oils from the leaves of Bauhinia rufa and B. dumosa collected from the Cerrado biome in central Brazil were obtained by hydrodistillation and analyzed using GC and GC/MS. Both oils had a predominance of sesquiterpenes (B. rufa: 95.3 ± 0.5%; B. dumosa: 97.2 ± 1.1%). β-Caryophyllene (15.8 ± 0.5%), epi-α-cadinol (12.8 ± 0.4%), γ-muurolene (12.2 ± 0.4%) and α-cadinol (10.0 ± 0.5%) were identified as the major constituents of the B. rufa oil, whereas germacrene B (37.6 ± 1.2%) and (E)-nerolidol (29.1 ± 0.6%) were the major constituents of the B. dumosa oil. Both oils were toxic to Tetranychus urticae by fumigation (B. rufa: LC50 = 2.76 µL/L of air; B. dumosa: LC50 = 0.97 µL/L of air) and residual contact (B. rufa: LC50 = 30.46 µL/mL; B. dumosa: LC50 = 16.44 µL/mL). The results of the two-choice method revealed that the oils affect the behavior of the mite, interfering in its feeding and egg-laying preferences.

In vitro assessment of synergistic combinations of essential oils against Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Rhipicephalus (Boophilus) microplus (Acari: Ixodidae), is one of the most important ectoparasite of cattle, responsible for causing severe economic losses in the tropical and subtropical regions of the world. The development of resistance to most of the commonly used chemical acaricides has stimulated the search for new herbal products as an eco-friendly tick control alternative. The aim of the present study was to evaluate the in vitro acaricidal activity of essential oils (EOs) of cloves (Syzygium aromaticum), bark of cinnamon (Cinnamomum zeylanicum) and leaves of lemon grass (Cymbopogon citratus) against unfed larvae of R. (B.)microplus by larval packet test. Also, various combinations were prepared by mixing of equal concentrations of any two and all three EOs and used to study the effects of interactions of mixtures against larvae of R. (B.) microplus. The lethal concentrations at 50% (LC50), 90% (LC90) and 99% (LC99) with 95% confidence limits (CL) were estimated by Probit analysis using PoloPlus. The computer software, CompuSyn, was used for determining the effects of interactions (synergistic, additive or antagonistic) of EO mixtures by calculation of Combination index (CI) and Dose-reduction index (DRI). Among the individual and mixture of two EOs, cinnamon EO and cinnamon EO + lemon grass EO combination showed highest acaricidal activity against R. (B.) microplus larvae. Further, the combination of cinnamon EO + lemon grass EO showed high synergism with CI value of 0.381, followed by cinnamon EO + clove EO showing moderate synergism whereas, clove EO + lemon grass EO showed only additive effect, with favorable dose reduction for each constituent drug in all three combinations. The combination of all three EOs (1:1:1) showed high synergism (CI value of 0.376) and favorable dose reduction (DRI index of 8.19, 25.64 and 4.64 for clove, cinnamon and lemon grass EOs, respectively) against R. (B.) microplus larvae.

Composition and acaricidal activity of essential oil from Elsholtzia densa Benth against Sarcoptes scabiei mites in vitro

Plant-based natural products represent an alternative to chemical compounds for the control of mites in veterinary medicine. Here, the essential oil of Elsholtzia densa (E. densa) Benth was extracted using hydrodistillation at a rate of 1.2%. The chemical composition of the essential oil was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The GC-MS analysis indicated that the principal compounds in the volatile oil of the sample were 4-Pyridinol (28.16%) and thymol (26.58%). The acaricidal activity of E. densa oil against Sarcoptes scabiei (S. scabiei) was tested in vitro. Toxicity test data were analysed using a complementary log-log (CLL) model. The E. densa oil was prepared in five concentrations by dilution with liquid paraffin (1, 2, 4, 8 and 16 mg/ml) and exhibited strong toxicity against S. scabiei with LT&lt;sub&gt;50&lt;/sub&gt; values of 16.637, 5.075, 2.884, 1.184 and 0.760 h, respectively. The LC&lt;sub&gt;50&lt;/sub&gt; values were 7.678, 4.623, 2.543, 1.502, 1.298 and 0.981 mg/ml for S. scabiei at 1, 2, 4, 8, 16 and 24 h, respectively. Compared to the control, the essential oil showed significant effects against S. scabiei in vitro. At 16 mg/ml, E. densa oil was found to kill all mites within a 16-h period. The results indicate that E. densa oil possesses potential acaricidal activity in vitro and may be exploited as a novel drug for the effective control of S. scabiei.

Evaluación del aceite esencial de cilantro (Coriandrum sativum L.) sobre el ácaro rojo de aves Dermanyssus gallinae (De Geer, 1778) (Acari: Dermanyssidae) bajo condiciones de laboratorio

El ácaro rojo Dermanyssus gallinae afecta las producciones avícolas, principalmente de ponedoras, al alimentarse de su sangre. Su control se realiza a través de acaricidas químicos, hacia los cuales aumenta su resistencia. Se evaluó la actividad acaricida de aceite esencial (ae) de cilantro (Coriandrum sativum) a concentraciones de 1, 2 y 3 mg/cm2 a través de bioensayos por contacto sobre adultos de D. gallinae y se comparó con un acaricida químico (Neguvón®). Los ácaros fueron colectados de aves (Gallus gallus L.) de traspatio. Se realizaron seis repeticiones por tratamiento. Estadísticamente, se determinaron los porcentajes de mortalidad y se calculó el anova. Se estableció el porcentaje de la actividad letal. Se estimó la CL50 y el TL50. El ae de cilantro causó el 100 % de mortalidad sobre la población de D. gallinae a los 25 min después del contacto con una concentración de 2 y 3 mg/cm2 y a los 30 min con una concentración de 1 mg/cm2. La CL50 del ae de cilantro fue de 1,3 mg /cm2, con un TL50 de 13 min sobre la población de D. gallinae. Se sugiere el aceite esencial de cilantro C. sativum como una alternativa a los acaricidas químicos para el control del ácaro rojo de aves D. gallinae.

Acaricidal properties of essential oils from Moroccan plants against immature ticks of Hyalomma aegyptium (Linnaeus, 1758); an external parasite of the spur-thighed tortoise (Testudo graeca)

ABSTRACTHyalomma aegyptium (Linnaeus, 1758) is a hard-tick species of the Ixodidae family with the main adult hosts being Palearctic tortoises of the genus Testudo. In Morocco, it is commonly found infecting Testudo graeca that has a wide geographic distribution and is subject to protection through international illegal trade legislation. This tortoise tick has been reported as an important vector of various human and animal pathogens. Unfortunately, to date, there are no strategies to control this hematophagous ectoparasite. The present study was conducted in laboratory to evaluate the acaricidal activity of essential oils (EOs) extracted from six plants of Moroccan origin as an alternative against H. aegyptium. All EOs tested displayed toxic effects on different life stages of H. aegyptium. Mentha suaveolens subsp. timija (LC50 = 0.910 µL/mL and LC90 = 1.465 µL/mL) and Satureja calamintha EOs (LC50 = 0.927 µL/mL and LC90 = 1.347 µL/mL) exhibited higher activity against hatching eggs, whereas Chenopodium ambrosioides EO was comparatively more toxic to larvae (LC50 = 0.444 µL/mL and LC90 = 0.918 µL/mL). Juniperus thurifera var. africana (LC50 = 0.0045 mL/cm2 and LC90 = 0.0118 mL/cm2) and Lavandula pedunculata subsp. atlantica EOs (LC50 = 0.0036 mL/cm2 and LC90 = 0.0110 mL/cm2) caused high mortality in nymphs. The effect of different EOs is discussed according to their chemical composition and bioactive components.

In vitro efficacy of essential oils with different concentrations of 1,8-cineole against Rhipicephalus (Boophilus) microplus.

The aim of this study was to evaluate the acaricidal activity of essential oils from three species of plants with intermediary concentrations of 1,8-cineole against the tick species Rhipicephalus (Boophilus) microplus. For this purpose, five serial concentrations (100.0, 50.0, 25.0, 12.5, 6.2 mg/mL) of essential oils from Mesosphaerum suaveolens (L.) Kuntze, Ocimum gratissimum L. and Alpinia zerumbet (Pers.) B. L. Burtt & R. M. Sm. were used on larval packet and adult immersion tests. The essential oils were analysed by gas chromatography-mass spectrometry (GC/MS) and gas chromatography-flame ionization detection (GC-FID), being detected 35.8, 24.7 and 24.0% of 1.8-cineol in the oils of M. suaveolens, O. gratissimum and A. zerumbet, respectively. The lethal concentration (LC 50) of each oil for larvae and engorged females was calculated through Probit analysis. All essential oils showed high efficacy (≥ 95.0%) on engorged females at the 100.0 mg/mL concentration. In regards to larvae, O. gratissimum (LC 50 = 11.9 mg/mL) was the most potent, followed by the A. zerumbet (LC50 = 19.7 mg/mL) and the M. suaveolens (LC50 = 51.6 mg/mL) essential oils. These results show that other compounds interfere with 1,8-cineole action.

Chemical Composition and Acaricidal Activity of Essential Oils from Croton rhamnifolioides Pax and Hoffm. in Different Regions of a Caatinga Biome in Northeastern Brazil

Essential oils from the stems and leaves of Croton rhamnifolioides Pax and Hoffm from three locations in the semiarid region of the state of Pernambuco, Brazil, were investigated. Seventy constituents were identified by gas chromatography-mass spectrometry (GC-MS) of the oils from the municipalities of Serra Talhada (ST), Buíque (BU) and Floresta (FL), representing 97.99±1.03% and 97.12±0.94% of the leaf and stem oils in ST, 97.42±0.77% and 97.50±0.68% in BU and 98.30±0.84% and 97.10±0.80% in FL. Sesquiterpenes were predominant in the oils. β-caryophyllene was the main constituent in all locations (ST: 22.45±0.70% in leaf oil and 25.80±0.63% in stem oil; BU: 33.34±0.56% in leaf oil and 38.45±0.95% in stem oil; FL: 26.67±0.53% in leaf oil and 29.50±0.86% in stem oil). Bicyclogermacrene (ST: 11.65±0.75% in leaf oil and 9.34±0.55% in stem oil; FL: 10.58±0.38% in leaf oil and 9.90±0.66% in stem oil) and 1,8-cineole (BU: 10.45±0.56% in leaf oil and 6.50±0.26% in stem oil) were also found in significant proportions. According to the principal component analysis, the chemical composition of the essential oils from C. rhamnifolioides varied across geographic locations. All oils demonstrated acaricidal action against T. urticae. The best result was observed for the BU oil, which was nine-fold and 14-fold more toxic as well as fourfold and 11-fold more repellent that the oils from ST and FL, respectively.

Acaricidal activity of essential oil of Syzygium aromaticum, hydrolate and eugenol formulated or free on larvae and engorged females of Rhipicephalus microplus.

The cattle tick, Rhipicephalus microplus (Canestrini, 1888) (Ixodida: Ixodidae), is the most important ectoparasite in cattle-breeding areas and is responsible for severe economic losses. Synthetic acaricides have been used to control this parasite. However, the need for safer products has stimulated the search for new acaricides, such as those to be obtained from medicinal plants. The essential oil of Syzygium aromaticum (clove) has many biological properties and shows great potential for use in veterinary applications. In the context of the need for new agents, this study investigated the in vitro properties of the hydrolate, essential oil and the main constituent of S.aromaticum, eugenol, in formulated and free applications against larvae and females of R.microplus. Eugenol and the essential oil caused 100% mortality in larvae at starting applications of 2.5 mg/mL and 5.0 mg/mL, respectively. The hydrolate showed no activity. Both eugenol and essential oil had good efficacy in adult immersion tests at 50 mg/mL and achieved 100% efficacy at a concentration of 100 mg/mL. The results of these tests reaffirm the important potential of clove essential oil and eugenol.

Acaricidal activities of essential oils against two-spotted spider mite, Tetranychus urticae Koch

Eleven essential oils (EOs) were screened for their fumigant and repellent activity against two-spotted spider mite, Tetranychus urticae Koch (Acarina: Tetranychidae) under laboratory conditions. Results showed that, in fumigant toxicity assay, Mentha longifolia L. showed more toxic to T. urticae (LC50 = 11.08 mg L−1 air) and was followed by Mentha piperita L. (LC50 = 15.86 mg L−1 air), Cymbopogon flexuosus (Nees ex Steud.) W. Watson (LC50 = 17.23 mg L−1 air) and Chrysopogon zizanioides (L.) (LC50 = 18.82 mg L−1 air). In repellent activity test, Acorus calamus (L.), M. piperita and C. flexuosus showed 100% repellent activity to T. urticae as compared to Cedrus deodara (Roxb.) and Aegle marmelos (L.) (76.67%).