Assessment of the Insecticidal Potential of the Eupatorium buniifolium Essential Oil Against Triatoma infestans (Hemiptera: Reduviidae). A Chiral Recognition Approach

How to repel a killer; chemical identification and effective repellent activity of commercial essential oils against kissing bugs

Triatomines are haematophagous insects, some species are vectors of Trypanosoma cruzi, the aetiological agent of Chagas disease. The main strategy for interrupting T. cruzi transmission is to avoid contact of the vector populations with humans. Volatiles from commercial essential oils are excellent candidates to serve as repellents of kissing bugs. We used an exposure device to assess the repellence effect of eight commercial essential oils on Triatoma pallidipennis. The most effective oils were blended and evaluated against T. infestans, T. pallidipennis and Rhodnius prolixus. The blend was also evaluated on parasitised T. pallidipennis. Data were compared with the commercial repellent NN-diethyl-3-methylbenzamide. We recorded the time the insects spent in the proximity of the host and determined if any of the evaluated oils served as kissing bug repellent. We found commercial essential oils and a blend that significantly reduced the time spent in the proximity of the host. The blend was effective for use by human males and females, repelling infected and non-infected insects. The study of essential oils as repellents of blood-sucking disease-vector insects could shed light on the development of new control strategies.

Investigation of insecticidal activity of two Rhododendron species on stored-product insects

This study was designed to investigate the insecticidal activity of the essential oils (EOs) and extracts from Rhododendron rufum and Rhododendron przewalskii. The EOs were extracted from the leaves of R. Rufum and R. przewalskii by hydro-distillation and their chemical components were analyzed by gas chromatography-mass spectrometry (GC-MS). The repellency, contact toxicity and antifeedant activity of the EOs and extracts were evaluated against Sitophilus oryzae and Tribolium castaneum along with those of their main components. A total of nine compounds were identified from the EO of R. Rufum, and the most abundant component was myristicin (79.72%). The EO of R. Rufum exhibited repellent activities at different levels and its main compound myristicin showed contact toxicity and repellent effects against S. oryzae and T. castaneum. Meanwhile, by bioassay-guided fractionation, four compounds with strong antifeedant activities against T. castaneum, 24-methylenecycloartanyl-2'E, 4'Z-tetradecadienoate (1), methyl thyrsiflorin B acetate (2), friedelin (3) and Excoecarin R1 methyl ester (4) were separated and identified from the ethanol extract of R. przewalskii for the first time. Considering the significant anti-insect activities, the EOs and extracts of R. Rufum and R. przewalskii might be used in integrated pest strategies, establishing a good perspective for the comprehensive use of natural plant resources of Rhododendron genus.

Volatile constituents of Eupatorieae (Asteraceae). Compositional multivariate analysis of volatile oils from Southern Brazilian species in the subtribe Disynaphiinae

Volatile oils (VOs) obtained from the aerial parts of species from the Disynaphiinae subtribe (genera Acanthostyles, Campovassouria, Disynaphia, Grazielia, Raulinoreitzia, and Symphyopappus) of Eupatorieae (Asteraceae) collected in Rio Grande do Sul, southern Brazil, were characterized using GC-MS. The yield of VOs relative to fresh material ranged from 0.2 to 1.7% between the Disynaphiinae subtribe samples (Acanthostyles buniifolius, Campovassouria cruciata, Disynaphia ericoides, D. ligulifolia, D. spathulata, Symphyopappus casarettoi, S. reticulatus, S. itatiayensis, Grazielia gaudichaudieana, G. intermedia, G. nummularia, G. serrata, Raulinoreitzia crenulata, and R. tremula). The VOs in this subtribe were mainly composed of terpene compounds. Compositional multivariate analysis demonstrated clustering between the samples of Grazielia and Raulinoreitzia on one side, which contain relatively higher proportions of monoterpenes, and Disynaphia and Campovassouria, which contain more oxygenated sesquiterpenes. The samples of Symphyopappus and Acanthostyles, which contain more sesquiterpene hydrocarbons, were located between these two main groups. Multivariate analysis accounting for the recent proposals of subtribal recircumscription of Eupatorieae was also performed. The odd chemistry of S. itatiayensis was in accordance with the recent attempts to exclude it from the genus Symphyopappus.

The application of essential oils as a next-generation of pesticides: recent developments and future perspectives

The overuse of synthetic pesticide, a consequence of the rush to increase crop production, led to tremendous adverse effects, as they constitute a major pollutant for both soils and water, with a high toxicity towards humans and animals and, at the same time, led to development of pest resistance. In the last period, the researches were directed towards finding new solutions with a lower toxicity, less damaging behaviour towards the environment, and a better specificity of action. In this context, the use of essential oils, a complex and unique mixture of compounds, can be considered for the next-generation pesticides. This review aims to present the main applications of the essential oils as insecticides, herbicides, acaricides, and nematicides, as they emerged from the scientific literature published in the last 5 years (2015 to present). From the identified articles within the time period, only those dealing with essential oils obtained by the authors (not commercially available) were selected to be inserted in the review, characterized using established analytical techniques and employed for the envisaged applications. The review is concluded with a chapter containing the main conclusions of the literature study and the future perspectives, regarding the application of essential oils as next-generation pesticides.