Repellent Activity Of Essential Oils Research Articles

Insecticidal and Repellent Activity of Essential Oils from Seven Different Plant Species against Tribolium castaneum (Coleoptera: Tenebrionidae).

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is the most destructive pest of stored grain commodities. To control the attack of this insect pest, it is important to develop non-hazardous alternatives to replace fumigants. This study examined the fumigant toxicity and repellent activity of seven essential oils (Chinopodium ambrosiodes, Pinus roxburghii, Zanthoxylum armatum, Lepidium sativum, Azadirachta indica, Baccharis teindalensis, and Origanum majorana) against adult T. castaneum under controlled laboratory conditions. The fumigant toxicity and repellent activities of essential oils were tested using five different doses (62.5, 125, 250, 500, and 1000 µg) in vapour-phase fumigation and four-arm olfactometer bioassays, respectively. In vapor-phase fumigation bioassays, mortality data were recorded after 24, 48, and 72 h. The results showed that C. ambrosiodes and P. roxburghii essential oils are potential fumigants against adult T. castaneum. In repellency bioassays, a one-week-old adult population of T. castaneum was used to test the repellency potential of the essential oils. The results indicated that C. ambrosiodes and P. roxburghii had significant repellency potential against T. castaneum. Overall, we conclude that these essential oils have strong repellent and fumigant properties and can be used as potential repellent compounds to deter the insects.

Formulation and evaluation of nanoemulgel loaded with essential oils with mosquito repellent activities

The mosquito repellent potential of plant materials, including essential oils, has been exploited for centuries. However, due to the volatility of essential oils, the protection against mosquitoes is short-lived. This study aimed to formulate citronella oil (CO) (Cymbopogon nardus) and palmarosa oil (PO) (C. martini) in the form of nanoemulgel (NEG) to delay their volatility and prolong protection time against mosquitoes. Nanoemulsions (NE) of both essential oils were prepared using ultrasonication after suitable hydrophilic-lipophilic balance (HLB) selection and phase diagram development. NEGs were formulated by mixing NEs and Carbopol 934 gel. Physicochemical characterizations, including in vitro release and permeation studies were conducted. Tween 80, Transcutol P and distilled water with 40 % glycerol were selected as surfactant, co-surfactant and aqueous components of the NEs, respectively. HLB values of 11 and 12 were found to be appropriate for CO and PO NEs preparation, respectively. The NEGs were kinetically stable and the formulation components were chemically compatible with each other. The NEG formulations prolonged the release of both essential oils for 24 h and significantly reduced the percentage permeation via cellulose acetate membrane as compared to NEs. Consequently, NEG could be a potential formulation to prolong the mosquito repellent activity of essential oils.

Repellent activity of essential oils to the Lone Star tick, Amblyomma americanum

BackgroundThe Lone Star tick, Amblyomma americanum is important to human health because of a variety of pathogenic organisms transmitted to humans during feeding events, which underscores the need to identify novel approaches to prevent tick bites. Thus, the goal of this study was to test natural and synthetic molecules for repellent activity against ticks in spatial, contact and human fingertip bioassays.MethodsThe efficacy of essential oils and naturally derived compounds as repellents to Am. americanum nymphs was compared in three different bioassays: contact, spatial and fingertip repellent bioassays.ResultsConcentration response curves after contact exposure to 1R-trans-chrysanthemic acid (TCA) indicated a 5.6 μg/cm2 concentration required to repel 50% of ticks (RC50), which was five- and sevenfold more active than DEET and nootkatone, respectively. For contact repellency, the rank order of repellency at 50 μg/cm2 for natural oils was clove > geranium > oregano > cedarwood > thyme > amyris > patchouli > citronella > juniper berry > peppermint > cassia. For spatial bioassays, TCA was approximately twofold more active than DEET and nootkatone at 50 μg/cm2 but was not significantly different at 10 μg/cm2. In spatial assays, thyme and cassia were the most active compounds tested with 100% and 80% ticks repelled within 15 min of exposure respectively and was approximately twofold more effective than DEET at the same concentration. To translate these non-host assays to efficacy when used on the human host, we quantified repellency using a finger-climbing assay. TCA, nootkatone and DEET were equally effective in the fingertip assay, and patchouli oil was the only natural oil that significantly repelled ticks.ConclusionsThe differences in repellent potency based on the assay type suggests that the ability to discover active tick repellents suitable for development may be more complicated than with other arthropod species; furthermore, the field delivery mechanism must be considered early in development to ensure translation to field efficacy. TCA, which is naturally derived, is a promising candidate for a tick repellent that has comparable repellency to commercialized tick repellents.Graphical

Chemical Composition, Toxicity, and Repellency of Essential Oils from Three Hedychium Species Against Stored-Product Insects.

Stored products are constantly infested by insects, so finding eco-friendly bioinsecticides for insect management is important. The work aimed to assess the insecticidal and repellent activity of essential oil (EO) from Hedychium glabrum S. Q. Tong, Hedychium coronarium Koen., and Hedychium yunnanense Gagnep. against Tribolium castaneum, Lasioderma serricorne, and Liposcelis bostrychophila. Results showed that 88 chemical components were identified in the extracted Hedychium EOs, indicating that they exhibited diversity in components. According to principal component analysis (PCA), the composition of the EO from the H. yunnanense stem and leaf (EOHYSL) was significantly different from other EOs due to the different organs and species. The biological activity also varied continuously with plant species and organs. Only the EO of H. yunnanense (EOHY) showed strong fumigant toxicity. While in the contact tests, EOHGR showed the strongest toxicity effect on L. bostrychophila, with a LC50 value of 71.76 μg/cm2, which was closest to the positive control (Pyrethrin). All EOs had remarkable repellent activities against the three target insects, and repellency increased with concentration. According to the results of the comprehensive score, EOHY had the highest potential, which ranged from 0.7999 to 0.8689. Thus, Hedychium EOs possess potential biorational traits to be biological insecticides.

Contact toxicity and repellent activity of essential oils from Alpinia zerumbet cv. ‘Variegata’ against stored product insects

ABSTRACT Alpinia zerumbet cv. ’Variegata’, as a special spice, has attracted social attention for its potential to replace synthetic chemicals as insecticides and repellents in food protection. In this work, the essential oils (EOs) from different organs of Alpinia zerumbet cv. ’Variegata’ (stem and leaf, flower, and rhizome) were extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The contact toxicities and repellent activities of the extracted EOs, along with their common components, against three insect species (Tribolium castaneum, Lasioderma serricorne, and Liposcelis bostrychophila) were evaluated. GC-MS analysis identified 25 components, and eucalyptol and camphor were the common primary components in the three EOs. The result showed that EOs and the main components (eucalyptol and camphor) exhibited varying degrees of contact toxicity and repellent activity against three insect species. Camphor exhibited more obvious contact toxicity than eucalyptol against both insect species (L. serricorne and L. bostrychophila), but the toxic effect was opposite for T. castaneum. The gray relation analysis explained that REOA had the strongest repellency against L. serricorne, with a coefficient of 0.52. The results in this study suggest that EOs of A. zerumbet cv. ’Variegata’ have the potential to be developed into botanical insecticides and repellents to control stored-product insects.

Essential Oils from Different Parts of Magnolia laevifolia: Chemical Constituents and Insecticidal Activities against Liposcelis bostrychophila.

Many synthetic pesticides were used to control a severe storage pest, booklouse (Liposcelis bostrychophila). However, considering the environmental impact, plant secondary metabolites were acceptable alternatives. An endemic plant, Magnolia laevifolia, has a significant and unique odour, so its essential oil (EO) could be an option for bio-pesticide development. This study extracted EOs from leaves, flowers, carpels and seeds of M. laevifolia. The common and major compound of EOs was isocapnell-9-en-8-one, which was present at 17.7 to 91.6 % in these four parts. We found no regular pattern in the composition of EO in terms of parts and collection time according to principal component analysis. The contact and repellent activities of EOs against the booklouse were then conducted. Leaves and flowers' EOs collected in the flowering stage had the best contact toxicity. The percent repellency values of the EOs from different parts of M. laevifolia reached above 80 % after 2 and 4 h exposure at 63.17 nL/cm2, with the same levels as DEET (p<0.05). It was shown that parts of plants and collecting time could influence the insecticidal activities of M. laevifolia EOs against booklouse, but collecting time played a significant decisive role in the contact test.

Chemical composition and repellent activity of essential oils of Tithonia diversifolia (Asteraceae) leaves against the bites of Anopheles coluzzii

Tithonia diversifolia is widely used in African traditional medicine for the treatment of a large number of ailments and disorders, including malaria. In the present study, we evaluated the repellent activity of essential oils (EO) of this plant against Anopheles coluzzii, a major vector of malaria in Africa. Fresh leaves of T. diversifolia were used to extract EO, which were used to perform repellency assays in the laboratory and in the field using commercially available N,N-Diethyl-meta-toluamide (DEET) and Cymbopogon (C.) citratus EO as positive controls and vaseline as negative control. The repellency rates and durations of protection of the human volunteers involved were used as measures of repellent activity. Chemical composition of the T. diversifolia EO was established further by gas chromatography coupled with mass spectrometry. The moisture content and oil yield were 81% and 0.02% respectively. A total of 29 compounds in the T. diversifolia EO was identified, with d-limonene (20.1%), α-Copaene (10.3%) and o-Cymene (10.0%) as the most represented. In field studies, the mean time of protection against mosquito bites was significantly lower in T. diversifolia EO-treated volunteers compared to treatments with C. citratus EO (71 min versus 125 min, p = 0.04), but significantly higher when compared with the non-treated volunteers (71 min vs 0.5 min, p = 0.03). The same pattern was found in laboratory repellency assays against A. coluzzii. In contrast, repulsion rates were statistically similar between T. diversifolia EO and positive controls. In conclusion, the study suggests promising repellent potential of leaves of T. diversifolia EO against A. coluzzii.

Volatile metabolites from new cultivars of catnip and oregano as potential antibacterial and insect repellent agents.

Plant based natural products have been widely used as antibacterial and insect repellent agents globally. Because of growing resistance in bacterial plant pathogens and urban pests to current methods of control, combined with the long- and short-term negative impact of certain chemical controls in humans, non-target organisms, and the environment, finding alternative methods is necessary to prevent and/or mitigate losses caused by these pathogens and pests. The antibacterial and insect repellent activities of essential oils of novel cultivars of catnip (Nepeta cataria L. cv. CR9) and oregano (Origanum vulgare L. cv. Pierre) rich in the terpenes nepetalactone and carvacrol, respectively, were evaluated using the agar well diffusion assay and petri dish repellency assay. The essential oils exhibit moderate to high antibacterial activity against three plant pathogens, Pseudomonas cichorii, Pseudomonas syringae and Xanthomonas perforans of economic interest and the individual essential oils, their mixtures and carvacrol possess strong insect repellent activity against the common bed bug (Cimex lectularius L.), an urban pest of major significance to public health. In this study, the essential oils of catnip and oregano were determined to be promising candidates for further evaluation and development as antibacterial agents and plant-based insect repellents with applications in agriculture and urban pest management.

Synergized potential, insecticidal and repellent activity of essential oils from two Rhododendron species against three stored product insects

ABSTRACT In this work, the essential oils (EOs) from leaves and flowers of Rhododendron spinuliferum and Rhododendron spiciferum were extracted by hydrodistillation, chemical compositions of EOs were analyzed by GC-MS and GC-FID. For R. spinuliferum and R. spiciferum, α- and β-pinene were common major compounds. It provided an opportunity to test the potential synergistic effect of α- and β-pinene among EOs. Firstly, four EOs and two major compounds (α- and β-pinene) exhibited fumigant, contact and repellent activities to three stored-product insects. To the red flour beetle, leaves of both species exhibited stronger contact toxicity than flowers did. This trend was diverse to the booklouse. Furthermore, binary mixture bioassays of α- and β-pinene were performed following natural proportions. Results of multiple linear regression showed that α-pinene, trans-β-farnesene and bornyl acetate were responsible for the contact toxicity to the red flour beetle and booklouse with diverse contribution.

Chemical Composition and Antifungal, Insecticidal and Repellent Activity of Essential Oils From Origanum compactum Benth. Used in the Mediterranean Diet.

Essential oils (EO) of Origanum compactum Benth. (O. compactum) are well known for their biological and pharmacological activities. This study aimed to assess the chemical composition, antifungal, insecticidal and repellent activities of EO of O. compactum used in the Mediterranean diet. Phytochemical screening was conducted using gas chromatography-mass spectrometry (GC/MS). Antifungal activity was tested by the disc diffusion method followed by a minimal inhibitory concentration (MIC) assay against Candida albicans (C. albicans), Aspergillus flavus (A. flavus), Aspergillus niger (A. nige), and Fusarium oxysporum (F. oxysporum). Repellent potential and toxicity of EO by contact and inhalation were tested against Callosobruchus maculatus (C. maculatus). The yield of essential oil obtained by hydrodistillation of O. compactum was 4.41 ± 0.35%, mainly composed of Carvacrol (38%) and Thymol (31.46%). Regarding antifungal activity, the results revealed a wide antifungal spectrum of the studied EO against the tested strains, which reached 100% growth inhibition, especially against A. niger and C. albicans even at the lowest MIC values (3.125 μg/mL). Concerning insecticidal activity, the EO caused total mortality of C. maculatus adults at a dose of 20 μL/L air with LC50 value of 5.3 μL/L air. A significant reduction in the number of eggs and emergence was proportionally recorded with increasing doses up to 100% at 20 μL/L air. For repellent activity, the studied EO showed a moderate repellent activity with an average percentage of 39.16%. The outcome of this work revealed that O. Compactum EO could be a sustainable and environmentally friendly alternative bioinsecticide and bio-fungicide to replace the chemically synthesized forms.

English

In recent years, essential oils (EOs) as alternatives to synthetic&nbsp;pesticides&nbsp;in managing pests have been assessed. The use of bioinsecticide in pest management is encouraged in agroecology for a sustainable agricultural system. Essential oils of Lantana camara&nbsp;L.&nbsp;leaves&nbsp;from different climatic zones of Kenya were extracted by&nbsp;steam distillation&nbsp;and analyzed through GC-MS to identify the compounds. The contact toxicity and&nbsp;repellent&nbsp;activity of EOs against the invasive tomato pest, Tuta absoluta,&nbsp;were tested. The toxicological assays were performed following the leaf-dip bioassay protocol, while the repellency activity was performed using the repellent response method for phytophagous pests and the data analyzed using the ANOVA test. It was found that L. camara EO has a good insecticidal activity with higher mortality (89%) on the 2nd instar larvae with a higher dosage (0.01 &micro;l/&micro;l). The repellence test also showed a higher average repellence (93.44%) effect with a higher dosage (0.01 &micro;l/&micro;l) of the EOs. According to these results, the EO of&nbsp;L. camara&nbsp;may well be a sustainable, eco-friendly alternative for synthetic insecticide in the T. absoluta management program. Key words: Bioinsecticide; essential oil, integrated pest management, invasive species, secondary metabolites.

Toxicity and repellent activities of Thymus pallescens and Cymbopogon citratus essential oils against Sitophylus granarius

This study evaluated the toxicity and repellent activities of essential oils (EOs) against Sitophilus granarius (Linnaeus, 1758), both in vitro and in vivo conditions. The EOs obtained from Thymus pallescens Noë. (Lamiaceae) and Cymbopogon citratus Stapf. (Poaceae) were analyzed by GC-MS, and revealed that carvacrol (56.64%) and geraniol (20.8%) as the respective major components. T. pallescens EO was found to be a more effective toxicant, with LC&lt;sub&gt;50&lt;/sub&gt; and LC&lt;sub&gt;90&lt;/sub&gt; values of 9.3 and 34.6 µL/mL, respectively, in the contact test vs 8.2 and 25.3 µL/mL in the fumigation test. T. pallescens EO showed also a stronger repellent effect with values ranging from 83.4% to 100%. In the in vivo test, the survival probability decreased from 99.9 to 2.48% among insects exposed to T. pallescens EO. These data demonstrated that EOs could be considered effective alternatives to chemical insecticides, providing pest control for stored products in an ecologically sustainable manner.

New approach for evaluating the repellent activity of essential oils against storage pests using a miniaturized model of stored-commodity packaging and a wooden transport pallet

Essential oils (EOs) are promising compounds for repellent protection of packed commodities or processed food against storage insect pests. Currently, the efficacy of EOs has been tested only when applied to packages, whereas no tests are available for real-world situations in which products are placed on cardboard spacers and transport pallets. Therefore, the aim of this work was to test the effects of placing products on pallets and the treatment of packaging with bergamot essential oil as repellent of storage pests. Due to the size constraint posed by the size of pallets and packaging, miniaturized models were designed and constructed. In this work, we experimentally determined (i) the pest behavioral modification resulting from placing untreated packaging (i.e., without repellent treatment) containing untreated food on a miniaturized pallet vs. placing it on a simulated floor surface and (ii) the repellent effect of bergamot oil applied separately to carton packaging (containing untreated food), wooden pallets or cardboard pallet spacers located between the pallet and packaging on two key storage pests (Sitophilus granarius and Tribolium confusum). The beetle infestation was assessed as a number of beetles in the packaging, and the EO repellency was assessed as number of beetles in the packaging and in the cardboard. The placement of untreated packaging on untreated pallets and spacers decreased packaging infestation by both species in comparison with the placement of products directly on the floor surface. The treatment of various parts of the packaging set (i.e., food packaging, pallet, and cardboard spacer) with bergamot oil had significant repellent activity that was generally more apparent for S. granarius than for T. confusum. The wooden pallet treatment had a greater and longer (i.e., 24 h) repellent effect than the packaging or cardboard spacer treatment on the tested pests. The results showed that the treatment of some parts (such as pallets and cardboard spacers) of the packaging set with essential oils may make it unnecessary to treat primary food/commodity packaging. This may have profound implications for the use and acceptance of essential oils as insect repellents under industrial conditions, since producers may worry about the migration of EOs from the primary packaging to food. Moreover, the miniaturized packaging model presented in this study allowed effective EO repellent testing in large assays in a limited space (e.g., 360 miniaturized model pallets were used in this experiment, and testing this volume of actual Euro pallets would require an area of 346 m2).

Insecticidal and Repellent Activities of Essential Oils from Seed and Root of Celery (Apium graveolens L.) Against Three Stored Product Insects

To exploit botanical insecticides and decrease the damage to crops by stored insects, we analyzed the chemical composition of essential oils derived from celery (Apium graveolens L.) seed and root. Repellent and insecticidal activity of obtained essential oils and components derived from celery seed and root against Tribolium castaneum (Coleoptera: Tenebrionidae), Lasioderma serricorne (Coleoptera: Anobiidae), and Liposcelis bostrychophila (Psocoptera: Liposcelididae) were evaluated. A total of fourteen and twelve components were respectively identified from the celery seed and root essential oil. D-limonene (79.3 %) and myristicin (47.3 %) were respectively the dominant components of seed and root essential oil. The root essential oil, D-limonene, and myristicin exhibited strong repellent activity (over 80 %) against T. castaneum at a concentration of 78.63 and 15.83 nL/cm2 after 2 h exposure. The seed essential oil, root essential oil, D- limonene, and myristicin showed contact toxicity against T. castaneum, L. serricorne, and L. bostrychophila with LD50 values of 16.15, 18.74, 14.57, and 36.46 μg/adult; 16.01, 74.78, 13.91, and 22.15 μg/adult; 199.56, 208.91, 810.85, and 29.71 μg/cm2, respectively. Seed essential oil and D-limonene showed stronger fumigant toxicity against T. castaneum, L. serricorne, and L. bostrychophila with LD50 values of 18.41 and 9.25 μg/ adult; 86.98 and 14.32 μg/adult; 36.58 and 18.39 μg/cm2, respectively. These findings suggested celery could be used as a botanical insecticide for insect management.

Preliminary Predictive Model of Termiticidal and Repellent Activities of Essential Oil Extracted from Ocotea quixos Leaves against Nasutitermes corniger (Isoptera: Termitidae) Using One-Factor Response Surface Methodology Design

Termites are one of the most challenging pests that agriculture and urban environments are faced with. They bring substantial losses in annual and perennial crops and damage wood components at construction sites. The development of natural products with biological activity for termite control is an ecological alternative in the search to replace conventional products. Hence, the aim of this research was to predict the termiticidal and repellent effects of the essential oil from Ocotea quixos leaves on Nasutitermes corniger using a one-factor response surface methodology design. The variable analysed was the concentration of essential oil in ethanol at an interval of 0.3–0.05% for anti-termite activity and between 0.12 and 0.01% for repellent action. A 100% mortality rate was found at concentrations higher than 0.12% and at the minimum concentration analysed, the effect was 22.2%. As for the repellent action, the concentration of 0.12% was able to repel 100% of the termites and at 0.01% it repelled 48.9%. The analysis of the essential oil from Ocotea quixos leaves by GC-MS resulted in the presence of 42 compounds, 39 of them elucidated. The main compounds were (E)-cinnamyl acetate (36.44%), (E)-cinnamaldehyde (27.03%), (E)-β-caryophyllene (5.21%) and (E)-methyl isoeugenol (4.18%).

Insecticidal and acetylcholine esterase inhibition activity of Rhododendron thymifolium essential oil and its main constituent against two stored product insects

In this work, we investigated the bioactivities of the essential oil (EO) extracted from the Rhododendron thymifolium and its principal germacrone against Lasioderma serricorne and Tribolium castaneum. The EO was obtained by steam distillation. Germacrone was obtained by cryogenic crystallization. The bioactivity of EO and germacrone was tested via contact and repellent activity assays. The results showed that EO and germacrone possessed contact and repellent activities against two species of insects. EO exhibited obvious contact activity against the L. serricorn adults, larvae and T. castaneum larvae with LD50 values of 29.15 µg/adult, 42.73 µg/larva, 19.65 µg/larva respectively. Germacrone exhibited excellent contact activity against the L. serricorne adults, larvae and the T. castaneum larvae with LD50 values of 17.18 µg/adult, 20.94 µg/larva, 20.93 µg/larva respectively. And at the highest testing concentrations (78.63 and 15.73 nL/cm2), the repellent activity of EO and germacrone on two target insects was comparable to that of the positive control (DEET) after 30 h exposure. In especially, in the treatment of the 120 h after the repellent activity of EO and germacrone against T.castaneum adults and larvae were still very significant and showed the same level percentage repellency as DEET. Meanwhile, germacrone exhibited inhibition of acetylcholinesterase activity with IC50 values of 3%. The results indicated that the EO of R. thymifolium and germacrone had the potential to be developed as natural insecticides and repellents for the control of T. castaneum and L. serricorne.

Essential oils of a few aromatic plants and their potential as knockdown, repellent and adulticidal agent to the filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae)

Use of synthetic products for the control of mosquito vectors raises serious concern about their negative impact on the environment, non-target organisms and human safety. Alternatively, the use of several natural products, particularly plant based essential oils have gained attention due to their good efficacy and ecofriendly nature. The adult knockdown effect and repellent activities of essential oils derived from three selected plants on Culex quinquefasciatus were evaluated. Data processing was performed using probit analysis. The results showed that essential oils from all the selected plants exhibited considerable knockdown effect on Cx. quinquefasciatus. In addition to this, all plant derived essential oils showed repellent activity which was significant in all concentrations. It is suggested that essential oils derived from Citrus limon were found to be very active as mosquito repellent.

Acute toxicity and repellent activity of essential oil from Atalantia guillauminii Swingle fruits and its main monoterpenes against two stored product insects

ABSTRACT The objective of this work was to analyze the essential oil from Atalantia guillauminii fruits in China and evaluate their chemical compositions, insecticidal and repellent activities against Tribolium castaneum and Lasioderma serricorne adults. The essential oil was obtained by hydro-distillation and its yield was 0.12% (V/W). All together 25 chemical compositions were identified by GC-FID and GC-MS, and the main chemical compositions were D-limonene (41.8%), β-pinene (10.9%) and selina-3,7(11)-diene (6.8%). The bioactivity of the obtained essential oil and its two main compositions (D-limonene and β-pinene) was investigated by fumigation, contact and repellent activity bioassay. The essential oil and its two main compositions all showed significant fumigant toxicity, contact toxicity and repellent activity against two target insects. These results suggest that the essential oil and its two main compositions have potential to be developed as natural insecticides and repellents for the control of stored product insect pests.

Essential Oils of Three Hypericum Species from Colombia: Chemical Composition, Insecticidal and Repellent Activity Against Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

The maize weevil (Sitophilus zeamais) is one of the main insect responsible of significant losses in stored products, and to keep nutritional value of them to find effective and safe solutions are very important. The Hypericum genus might be a potential source of new bio-insecticides due to the chemical composition of essential oils. In this study, components of essential oils of three Hypericum species were investigated for first time by Gas Chromatography-Mass Spectrometry (GC-MS) and, fumigant and contact toxicities as well as the repellent activity of essential oils of them were evaluated against S. zeamais adults. While the main components in H. mexicanum oil were determined as n-nonane (53.08%) and α-pinene (25.28%), the major constituents were determined as α-pinene (45.52%) and β-caryophyllene (13.59%) in the essential oil of H. myricariifolium. Chemical composition of essential oil of H. juniperinum were found to be n-nonane (12.0%), α-pinene (8.25%), geranyl acetate (7.93%), and β-caryophyllene (13.60%). The results revealed that H. mexicanum and H. myricariifolium oils have fumigant toxicity (LC50 &lt; 500 µL/L air) and a potential action as repellents (RP &gt; 70% at 6.2–22.7 μL/L air) for the control of the pest.

Mosquitocidal and repellent activities of essential oils againstCulex pipiensL.

AbstractPlants are a prospective source of novel natural insect repellents and botanical insecticides. This study was conducted to investigate the chemical composition of the essential oils of three plants growing in Saudi Arabia, namelyDucrosia anethifolia,Achillea fragrantissima, andTeucrium polium; and to evaluate their potential mosquitocidal and repellent activities against adult femaleCulex pipiensL. The main components of the three oils were found to be decanal (28.9%) and chrysanthenyl acetate (10.04%), (D. anethifolia); sabinyl acetate (35.79) and artemesia ketone (18.28%) (A. fragrantissima);α‐cadinol (49.53%) andδ‐cadinene (10.23%) (T. polium). The oil ofA. fragrantissimawas the most toxic (LC50 = 0.11 μL/L air) followed byD. anethifoliaandT. poliumwith LC50values of 5.22 and 25.98 μL/L air, respectively.T. poliumoil was the most repellent (292 min at 2 μL/cm2), followed byD. anethifoliaandA. fragrantissima. The results indicate that the essential oils have a potential fumigant insecticidal and repellent activities for mosquito control.