Semi-field evaluations of three botanically derived repellents against the blacklegged tick, Ixodes scapularis (Acari: Ixodidae)

Three compounds derived from botanicals sources, ethyl perillyl carbonate, geranyl isovalerate, and citronellyl cyclobutane carboxylate, were tested for repellent activity against Ixodes scapularis Say in a semi-field trial. Tick drags were treated with the compounds or with N, N-diethyl-m-toluamide (DEET) at high (0.25mg/cm2) or low (0.15mg/cm2) concentrations. Negative controls included untreated drags and drags treated with acetone, the carrier for all repellents. Freshly treated drags (within 20 minutes) were used to collect I. scapularis ticks at a county park in Wisconsin. To assess effectiveness, we measured tick encounter rates, detachment rate, and time to detachment. None of the repellent treatments resulted in significantly fewer encounters compared to both control treatments. However, the percentage of ticks that detached within 3 min was significantly higher on drags treated with repellents compared to controls. DEET was the most effective, repelling 69.7 - 87% of ticks by 3 min, but the effectiveness of the three test compounds was still high, ranging from 42% to 87% of ticks detaching by 3 min. For time to detachment, there were no significant differences between DEET and the three test compounds. We conclude that these botanically-derived repellents were effective against I. scapularis in a semi-field trial and could be viable alternatives to DEET.

Medicinal plants with mosquitoes repellent activity: a systematic review

Repellents are important allies in trying to prevent diseases transmitted by mosquito bites. Plants have been a source of various repellents and insecticides because they have a large reservoir of bioactive substances, in addition, their products have already been tested and are gaining space in research as a low-cost and easy-access alternative. A systematic review was carried out in the databases, Science Direct, Scielo, SciFinder, Springer, PubMed / Medline, Scopus and Web of Science, evaluated by three reviewers. Titles, abstracts and articles were analyzed in full in English, Spanish and Portuguese. To identify the articles, the following descriptors from the Medical Subject Headings (MeSH) were used: “insect repellents”, “essential oils”, “plants extract”, “repellent activity”, mosquitoes and plants. The bibliographic search resulted in 2274 records. Of these, 27 abstracts were considered potentially relevant, and at the end of the selection, 17 articles were included in their entirety. It was found that medicinal plants showed repellent activity against various species of mosquitoes, however due to the little standardization of the methodologies used and the products obtained it is necessary to develop standardized methods to guarantee the quality and reproducibility of clinical trials with medicinal plants.

Development and Evaluation of Herbal Mosquito Repellent Cream

Mosquito repellent is a product that is applied to the skin or other surfaces to deter insects (and arthropods in general) from landing or climbing on that surface. The interest in plant-based repellants has been revived seeing that the development of resistance, cross-resistance and possible toxicity hazards associated with synthetic insecticides and their rising cost. The present study aimed towards the development and evaluation of safe and efficient herbal mosquito repellent from leaf extracts of Azadirachta indica, Vitex negundo, and Ocimum gratissimum. Six different types of formulation (Type-1 to 6) were prepared using each plant extract and optimized ingredients. The mosquito repellent activity of the formulation was tested using the arm-in-cage method. One skin rubbed with a small quantity of formulation was exposed to 20 mosquitoes and the number of mosquitoes that aligned or biting the arm was recorded in each minute for five minutes. The most effective repellent activity of the Type2 formulation was 87.5% (Y-shaped Model) and 91.62% (Rectangular-shaped Model). The Type1, Type3, Type4, Type5 and Type6 formulation showed 66.62% , 58.25%, 68.75%, 70.75% and 62.5% repellent activity in Y shaped model and 66.62%, 62.5%, 70.75%, 83.25% and 62.5% repellent activity in Rectangular shaped model respectively. During these studies, we found that Hexane extract showed higher repellent activity. No allergic reactions were observed upon the skin. So, it is a safe product. The formulation was ecological, economical and highly efficient.

Ateleia glazioveana and Ocimum basilicum: plants with potential larvicidal and repellent against Aedes aegypti (Diptera, Culicidae)

The Aedes aegypti is the main vector of the transmission of diseases such as dengue, yellow fever, Chikungunya, and Zika. The agents used for the control of mosquito involve the use of synthetic compounds, which may cause toxicity and contamination environmental. Aiming to test the effectiveness of natural products, the aim of this study was to evaluate the larvicidal and repellent activity of extracts of Ateleia glazioveana Baill. (timbó) and essential oil of Ocimum basilicum L. (manjericão), against A. aegypti. The activities of hydroalcoholic (HEA) and dichloromethane (DEA) extracts from A. glazioveana against A. aegypti larvae were assessed after exposure for 24, 48, and 72 h, using water and Bacillus thuringiensis israelensis as negative and positive controls, respectively. For repellent evaluation, we investigated the sting attempts of A. aegypti in response to the application of HEA- and DEA-based body creams (5%), as well as an alcoholic spray based on the essential oil from O. basilicum. The repellency of these preparations was compared with negative (vehicle) and positive (DEET) controls. Although HEA showed no apparent larvicidal activity, DEA at concentrations of 150 to 500 mg/ml showed high larvicidal potential after 24 h, compared to the negative control group (p < 0.001). Moreover, the DEA-based cream and the alcoholic spray of O. basilicum based essential oil showed higher repellency compared with the vehicle (84.5% and 70.5%, respectively). Accordingly, it is possible to infer that extracts and preparations of A. glazioveana and O. basilicum exhibit larvicidal and repellent activity against A. aegypti.

Ovicidal and Repellent Activities of Several Plant Essential Oils Against Periplaneta americana L. and Enhanced Activities from their Combined Formulation

Natural ovicidal and repellent agents against Periplaneta americana are in urgent need, and plant essential oils (EOs) can assume this role quite readily. In this study, ovicidal and repellent activities against Periplaneta americana of EOs from Cymbopogon citratus, Cinnamomum verum, Eucalyptus globulus, Illicium verum, and Zanthoxylum limonella in soybean oil and in ethyl alcohol were determined by topical and dual-choice assays, as well as 10% cypermethrin and a combined formulation of 5% C. verum EO + 5% I. verum EO. Cypermethrin at 10% provided the highest toxicity (100% inhibition rate) against the eggs, but only slightly higher than that (99.3%) provided by the combined EO formulation, while the highest repellent activity against the adults was provided by the combined formulation (89.5% repelled cockroaches at 48 h after treatment). In addition, all EO formulations in soybean oil provided higher ovicidal and repellent activities than in ethyl alcohol. To conclude, the combined EO formulation in soybean oil can replace cypermethrin because their efficacy was nearly equivalent, but the combination should be much safer to use.

Repellent Activity of Cymbopogon citratus Essential Oil Against Four Major Stored Product Pests: Plodia interpunctella, Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum

Summary The purpose of this study is to assess the repellent activity of lemongrass (Cymbopogon citratus) essential oil (EO), grown in Serbia under greenhouse conditions, against four prevalent stored product pests: Plodia interpunctella (larvae), Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum (adults). The lemongrass EO repellency was tested using filter paper in Petri dishes and a Y-tube olfactometer. According to the repellency index (RI), the lemongrass EO repellency was divided into 5 classes. Prior to biotesting, the chemical characterization of lemongrass EO was performed and the following main compounds were detected: myrcene (31.0%), geranial (30.0%), and neral (23.6%). The C. citratus EO considered was found to exhibit the Class III repellent activity against P. interpunctella larvae only at the highest concentration (namely 0.5%). This is the very first report on the C. citratus EO repellent activity against this pest. The lemongrass EO examined showed strong repellency (Class IV) against S. oryzae (0.2% and 0.5% of EO), A. obtectus (0.1% and 0.2%), and T. castaneum (0.05-0.1%). Moreover, higher lemongrass EO concentrations (0.5%) were found to exhibit extreme repellency (Class V) against A. obtectus and T. castaneum. The results obtained were confirmed in the bioassays performed, indicating the great potential of lemongrass EO as a bio-repellent when applied in higher concentrations to all the insects considered, regardless of the exposure period.

Repellent activity of three essential oils against dengue and filarial vector mosquitoes

Cymbopogon nardus, Syzygium aromaticum, and Citrus sinensis have been well known to possess insecticidal activity. Here, we investigated the repellent activity of individual of three essential oils (C. nardus, S. aromaticum, C. sinensis) and a combination of essential oils (C. nardus + C. sinensis, C. nardus + S. aromaticum, and C. sinensis + S. aromaticum) against a dengue vector, Aedes aegypti and a filarial vector, Culex quinquefasciatus. The essential oils (1 mg) were smeared evenly on the surface of the left arm (three volunteers) and then subjected to 25 females of A. aegypti and C. quinquefasciatus in the cage. The number of landed mosquitos was observed every hour for 7 hours to determine the protection index (PI). The result showed that individuals of three essential oils and a combination of essential oils generated > 90% of PI until 7 hours of application for both mosquitos species tested. Overall, the data demonstrated that individual of three essential oils, i.e., C. nardus, S. aromaticum, C. sinensis, and various combinations of essential oils (C. nardus + C. sinensis; C. nardus + S. aromaticum; C. sinensis + S. aromaticum) are promising as repellent agents against A. aegypti and C. quinquefasciatus.