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Essential Oils as Ecofriendly Biopesticides? Challenges and Constraints
Abstract
Recently, a growing number of plant essential oils (EOs) have been tested against a wide range of arthropod pests with promising results. EOs showed high effectiveness, multiple mechanisms of action, low toxicity on non-target vertebrates and potential for the use of byproducts as reducing and stabilizing agents for the synthesis of nanopesticides. However, the number of commercial biopesticides based on EOs remains low. We analyze the main strengths and weaknesses arising from the use of EO-based biopesticides. Key challenges for future research include: (i) development of efficient stabilization processes (e.g., microencapsulation); (ii) simplification of the complex and costly biopesticide authorization requirements; and (iii) optimization of plant growing conditions and extraction processes leading to EOs of homogeneous chemical composition.
... " Such aspects reinforce the development of new technologies to control these ectoparasites in a manner that is safe for humans, animals and the environment (One Health), in addition to being economically viable (Sustainability) [13,[32][33][34]. Essential oils (EOs) have shown potential for the development of ecofriendly acaricides [35]. These oils are natural products resulting from the secondary metabolism of aromatic plants, containing a mixture of about 20 to 60 volatile, fat-soluble and strongly odorous compounds [36]. ...
... These oils are natural products resulting from the secondary metabolism of aromatic plants, containing a mixture of about 20 to 60 volatile, fat-soluble and strongly odorous compounds [36]. In plants, EOs work by attracting pollinators and seed dispersers, repelling and combating parasites, pathogens and predators, in addition to assisting against abiotic stressors ( Fig. 1) [35,37,38]. The compounds found in EOs (EOCs) can be divided mainly into two groups according to their biosynthesis: terpenes/terpenoids (such as monoterpenes and sesquiterpenes) and aromatic and aliphatic compounds, such as phenylpropanoids [36,39]. ...
... As an advantage, EOs present lower toxicity to vertebrates compared to the major compounds isolated from them when tested alone [115]. Furthermore, their mixtures can result in synergistic effects due to the presence of compounds with different action mechanisms [35,37]. As a negative aspect, EOs present variations in chemical composition, which can hinder commercial applications due to the lack of standardization, hence generating difficulties in quality control and obtaining raw materials on a large scale. ...
Background
Tick control is a worldwide challenge due to its resistance to acaricides. Essential oils (EOs) and isolated compounds (EOCs) are potential alternatives for tick control technologies.
Methods
A review with EOs and EOCs, under field and semi-field conditions, was performed based on Scopus, Web of Science and PubMed databases. Thirty-one studies published between 1991 and 2022 were selected. The search was performed using the following keywords: "essential oil" combined with "tick," "Ixodes," "Argas," "Rhipicephalus," "Amblyomma," "Hyalomma," "Dermacentor," "Haemaphysalis" and "Ornithodoros." The words "essential oil" and "tick" were searched in the singular and plural.
Results
The number of studies increased over the years. Brazil stands out with the largest number (51.6%) of publications. The most studied tick species were Rhipicephalus microplus (48.4%), Ixodes scapularis (19.4%), Amblyomma americanum and R. sanguineus sensu lato (9.7% each). Cattle (70%) and dogs (13%) were the main target animal species. Regarding the application of EOs/EOCs formulations, 74% of the studies were conducted with topical application (spray, pour-on, foam, drop) and 26% with environmental treatment (spray). Efficacy results are difficult to evaluate because of the lack of information on the methodology and standardization. The nanotechnology and combination with synthetic acaricides were reported as an alternative to enhance the efficacy of EOs/EOCs. No adverse reactions were observed in 86.6% of the studies evaluating EOs/EOCs clinical safety. Studies regarding toxicity in non-target species and residues are scarce.
Conclusions
This article provides a comprehensive review on the use of EOs and EOCs to reduce tick infestations, in both the hosts and the environment. As future directions, we recommend the chemical characterization of EOs, methodology standardization, combination of EOs/EOCs with potential synergists, nanotechnology for new formulations and safety studies for target and non-target organisms, also considering the environmental friendliness.
Graphical abstract
... The EOs are generally composed of a large number of compounds, such as monoterpenes, sesquiterpenes, phenols, ketones and other compounds [25,26]. Their chemical compounds are often affected by some biological factors (genotypes and interactions with other organisms), some environmental factors (altitude, nutrition levels, and climate), collection time and collection parts and so on [27][28][29]. Generally, the content and interactions of different chemical compounds in EO can affect the EO's overall biological activity [30]. ...
... Overall, there are some quantitative and qualitative differences in chemical composition of the EOs of the same species from different plant parts or different reports. The differences of chemical composition of EO may be probably due to genetic factors, different chemotypes, environmental factor and the nutritional status of the plants as well as other factors that can influence the EO composition [27][28][29]46]. In addition, the chemical diversity between leaves and flowers EOs might be the results of a different genetic expression that allows an adaptation process to ecological functions [47]. ...
... [9] Therefore, several studies have considered EOs as botanical insecticides for controlling agents that can be pathogenic to humans. [8][9][10][12][13][14][15] The use of synthetic control methods against phytopathogens has also proven to be disadvantageous in agricultural production, mainly due to the decrease in soil quality and crop yields obtained. [16,17] On the other hand, natural compounds are biodegradable and have been shown to be an alternative for the treatment of fungal infections, mainly due to their broad spectrum of bioactive compounds. ...
... However, the present study identified a wide range of oxygenated sesquiterpenes in the obtained EO, possibly indicating that its chemical composition is related to its larvicidal activity. Oxygenated components can generate chemical interactions with the larvae's epithelium [9,15] which could also explain the efficacy of the EO of E. brasiliensis against the immature stages of A. aegypti. The EO obtained from E. uniflora, with an LC 10 of 95.9 ppm, LC 90 of 226.5 ppm and LC 50 of 147.46 PPM, can be considered effective against A. aegypti larvae. ...
Myrtaceae is one of the most diverse and abundant botanical families, exhibiting wide diversity in the chemical composition of essential oils (EOs). EOs have various biotechnological applications such as controlling the populations of organisms that negatively impact humans. This study aimed to extract EOs from Myrtaceae species, chemically characterize them, and evaluate their larvicidal and fungicidal effects. EOs were extracted from the leaves of Eugenia brasiliensis, Eugenia uniflora, Psidium cattleyanum, Psidium guajava, and Syzygium cumini by hydrodistillation for 3 h and characterized by chromatographic analysis. Larvaes of Aedes aegypti and colonies of Fusarium oxysporum were subjected to increasing EO concentrations to determine the larvicidal and fungicidal potential. The EOs of Eugenia and Psidium species are primarily composed of sesquiterpenes (> 80%), whereas S. cumini EO is rich in monoterpenes (more than 60%). The Eugenia species had similar amounts of oxygenated monoterpenes, which may explain their higher larvicidal potential compared to other species, with CL50 of 86.68 and 147.46 PPM, respectively. In addition to these two study species, S. cumini showed a high inhibition of fungal growth, with more than 65% inhibition. We demonstrated that the actions of five EOs from Myrtaceae with different biological activities are associated with chemical diversity.
... To our knowledge, Kompolti hemp EOs were previously evaluated for antimicrobial (Novak et al., 2001), and antimycotic (Di Sotto et al., 2022) properties, while literature data on their insecticidal, acaricidal, and repellent effect are missing. To overcome the main limiting factors in the use of EOs as active ingredients for green insecticide formulations, namely the high volatility, low stability, thermal degradation, oxidative decomposition, and scarce water solubility, innovative EOs delivery systems are being recently studied (Turek and Stintzing, 2013;Pavela and Benelli, 2016). In this respect, EOs encapsulation in micro-and nanoemulsions (NEs) has turned out to be one of the most promising solutions for improving EOs physicochemical characteristics, bioavailability, and administration (Pavoni et al., 2019;Benelli et al., 2020;Ricupero et al., 2022). ...
... On the other hand, Rossi et al. (2020) tested two EOs from different hemp varieties (i.e., Felina 32 and Carmagnola CS) on Anopheles stephensi Liston and Anopheles gambiae (Giles) larvae, showing an LC 50 between 73.5 and 78.8 ppm, much closer to that estimated in the present research. Besides the different susceptibility of diverse mosquito species to hemp EO, it is well known that the EO efficacy can vary according to several factors, such as the variety and the parts of the plant from which the EO was extracted, the plant's growing area, among others, and the EO extraction method, among others (Pavela and Benelli, 2016). ...
... Additionally, mixtures of two or more essential oil components have been shown to exhibit synergis tic, additive, or antagonis tic effects on various insects, including spiders, nematodes, house flies, plant mites, and moths. Synergis tic toxic interactions are relevant to pes t management and the development of effective natural product formulations, and they enable us to achieve higher mortality rates with lower amounts of active ingredients [14][15]. There are many plants' essential oil components that have insecticidal effects. ...
... It has been found to have insecticidal properties agains t various insects, including mosquitoes, flies, and cockroaches. Its mode of action is thought to be disrupting the insects' nervous sys tem, leading to paralysis and death [12][13][14][15][16][17][18][19][20]28]. α-pinene is a monoterpene that is commonly found in essential oils of pine trees, as well as in other plants such as rosemary and eucalyptus. ...
Using plant essential oils (EOs) as a pesticide alternative has gained increasing interest as a promising strategy to reduce the harmful effects of chemical pesticides. This study aims to investigate the chemical composition of Eucalyptus globulus Labill and Rosmarinus officinalis L. essential oils and evaluate their impacts against Blattella germanica L. under laboratory conditions. The essential oils were prepared from dried leaves using hydro-distillation (HD) as a chemical extraction method. The gas chromatography-mass spectrometry (GC-MS) was employed to analyze and identify their chemical compounds. Bioassays were conducted using the standard contact method recommended by the World Health Organization, and the data were analyzed using the probit regression model. By GC-MS analysis, the major components included 1,8-cineole (50.67%), alpha-pinene (17.48%), limonene (4.26%) for eucalyptus and alpha-pinene (20.67%), camphor (10.69%), 1,8-cineole (9.38%), Borneol (9.02%), comphene (7.15%), and limonene (4.88%) for rosemary. The LD50 values were 9. 27, 10.54, and 3.23 %, and LD95 values increased to 27.2, 22.3 %, and 14.3% for rosemary, eucalyptus, and their mixture. The EOs mixture had a higher repellent effect with a repellency rate of 98.9% at a concentration of 3% compared to 93.3% and 90% at a concentration of 5% for rosemary and eucalyptus alone.
... They can be extracted from all plant organs: buds, flowers, stems, seeds, fruits, roots, wood (Jugreet et al. 2020). EOs are composed of many compounds, generally, around 20-60 components with different concentrations; some are major components at fairly high concentrations (20-70%), while others are present in trace amounts (Bilia et al. 2014;Pavela and Benelli 2016). The composition of EOs can be variable according to the growth conditions of the plant from which they are extracted (abiotic and biotic stress) (Seow et al. 2014). ...
... In literature, a lot of laboratory work was carried out on the use of EOs in plant protection to manage weeds (herbicidal effect), insects (acaricidal, nematicidal, and insecticidal effect), and causal agents of diseases (virucidal, bactericidal, and fungicidal effect), and there are many review articles that summarize it (Bakkali et al. 2008;Jugreet et al. 2020;Pavela and Benelli 2016;Kalemba and Kunicka 2003;Yoon et al. 2013 ;Nazzaro et al. 2017;Campolo et al. 2018;Fierascu et al. 2020;Ikbal and Pavela 2019 ;Ibáñez and Blázquez 2020 ;Raveau et al. 2020). Regarding the anti-fungal properties of EOs, distinctions were made between toxigenic (Dambolena et al. 2012), post-harvest (Lee et al. 2007;Combrinck et al. 2011;Camele et al. 2012;Shao et al. 2013), or phytopathogenic fungi (Terzi et al. 2007;Dan et al. 2010;Kadoglidou et al. 2011;Riccioni and Orzali 2011;Sharma et al. 2017). ...
Botanicals are various plant-based products like plant extracts or essential oils. Anti-fungal activities of selected essential oils were tested on the pathogen causing potato and tomato late blight ( Phytophthora infestans ). Tests to evaluate anti-oomycete activities of commercial essential oils and their major compounds were carried out in vitro in microplate in liquid media. Anti-oomycete activities on Phytophthora infestans strain were obtained from essential oils/major compounds: Eucalyptus citriodora /citronellal; Syzygium aromaticum (clove)/eugenol; Mentha spicata /D-Carvone, L-Carvone; Origanum compactum /carvacrol; Satureja montana (savory)/carvacrol; Melaleuca alternifolia (tea tree)/terpinen-4-ol, and Thymus vulgaris /thymol. As an active substance of mineral origin, copper sulfate was chosen as a control. All selected essential oils showed an anti-oomycete activity calculated with IC 50 indicator. The essential oils of clove, savory, and thyme showed the best anti-oomycete activities similar to copper sulfate, while oregano, eucalyptus, mint, and tea tree essential oils exhibited significantly weaker activities than copper sulfate. Clove essential oil showed the best activity (IC 50 = 28 mg/L), while tea tree essential oil showed the worst activity (IC 50 = 476 mg/L). For major compounds, three results were obtained: they were statistically more active than their essential oils (carvacrol for oregano, D- and L-Carvone for mint) or as active as their essential oils sources (thymol for thyme, carvacrol for savory, terpinen-4-ol for tea tree) or less active than their original essential oils (eugenol for clove, citronellal for eucalyptus). Microscopical observations carried out with the seven essential oils showed that they were all responsible for a modification of the morphology of the mycelium. The results demonstrated that various essential oils show different anti-oomycete activities, sometimes related to a major compound and sometimes unrelated, indicating that other compounds must play a role in total anti-oomycete activity.
... According to Abdelgaleil et al. (2009) and Allam et al. (2018), the most potent inhibitor of AChE isolated from Tribolium castaneum Herbst larvae is 1,8-cineole, followed by (−)-limonene. In general, monoterpenes' lethal action may be specialized to the inhibition of AChE (Pavela and Benelli 2016). ...
... Biopesticides are usually classified into three classes: (a) microorganism-based pesticides (e.g., biofungicides, bioinsecticides); (b) plant-incorporated pesticides in which transgenes are acting (e.g., transgenic Bt toxins [26,27]); and (c) biochemical-based pesticides in which naturally occurring substances are components (e.g., plant essential oil) [28] as depicted in Fig. 1. In addition to the microbial and plant-derived biopesticides, various phytophagous insect varieties are also included in the category of biopesticides for their predatory or inhibitory role against pathogens as well as pests [29]. ...
Biopesticides are biological products or organisms which are potential candidates for eco-friendly pest management and crop protection over the chemical pesticides. The so-called biopesticides include viruses, bacteria, fungi, predators, parasites, and pheromones exhibiting a variety of modes of actions. They are less toxic, rapidly degradable, and more targeted to specific pests. However, it is noted that the formulation of biopesticides plays a crucial link between production and application, and the former dictates economy, longer shelf life, ease of application, and enhanced field efficacy. Moreover, there is an urgent need for organic farmers to gain more proficiency in using biopesticides. Even though biopesticides have more advantages, the main challenge is the marketing of biopesticides. Advances in biopesticide research and development significantly reduce the environmental damage caused by the residues of synthetic insecticides and support sustainable agriculture. Numerous products have been developed since the introduction of biopesticides, some of which have taken the lead in the agro-market after being registered and released. The types of biopesticides; their mode of action; formulation strategies; recent advancements of biopesticides focusing mainly on improvement of its action spectra, to thereby replace chemical pesticides; and finally, the future aspects of biopesticides have been discussed in this review.
... Future research should therefore focus on experimentally testing our hypothesis that the pesticidal activity observed in this study correlates with the relative abundancies of the respective EOs' majority compounds. The elucidation of potential synergistic effects should also receive special attention before the evaluation of particular coating techniques, aimed at improving the efficacy of the active principles, is considered (Pavela and Benelli 2016). ...
In search of new sustainable biopesticides, we determined the phytochemical profiles, acaricidal and insecticidal properties of EOs distilled from the aerial parts of three Mexican Bursera species. Results were obtained by GC–MS analysis and three different bioassays, indicating that the EO of Bursera glabrifolia exhibited high relative abundancies of α-pinene, β-myrcene, and α-phellandrene, as well as promising pesticidal activity against Spodoptera littoralis larvae (LD50,90 = 32.4, 107.2 µg/larva), and Musca domestica (LD50,90 = 23.2, 103.2, and 13.5, 77.4 µg/female or male adult, respectively) and Tetranychus urticae adults (LD50,90 = 7.4, 30.3 µg/cm2). The Bursera lancifolia and Bursera linanoe samples contained mainly D-limonene or linalyl acetate and linalool, respectively, and showed generally less potent pesticidal properties (S. littoralis larva, LD50,90 = 45.4, 154.4 and 52.2, 158.7 µg/larva, respectively; female M. domestica adult, LD50,90 = 69.2, 210.9 and 45.1, 243.8 µg/female adult, respectively; T. urticae adults, LD50,90 = 20.7, 90.5 and 17.5, 71.4 µg/cm2, respectively). However, the EO of B. linanoe exhibited an especially pronounced activity against male M. domestica adults (LD50,90 = 10.6, 77.2 µg/male adult). Our findings prove the pesticidal potential of Mexican Bursera species in the context of integrated pest management (IPM) and highlight the importance of conducting further research to elucidate both the active principles and possibly existing synergistic effects.
... Researchers have carried out experiments to test the potential of natural substances as Acaricidal against Varroa Destructor [12,13]. Indeed, many essential oils (EOs) based products have become alternatives for mite control [14,15]. These essential oils can cause toxicity, repellent effects, or inhibit pest reproduction [16,17]. ...
Several studies have shown that oregano (Origanum) essential oil has Acaricidal activity against Varroa Destructor, a parasitic pest of the honey bee Apis mellifera. While many researchers have demonstrated that essential oils of this genus are highly variable due to genetic factors and climatic condition, this raises the question of whether this variance affects their Acaricidal activity. If there are differences in effectiveness, which chemical composition exhibits the greatest bio-Acaricidal activity against Varroa Destructor? This comparative study aimed to analyze the chemical composition of essential oils (EOs) extracted by Hydrodistillation from three populations of Algerian Origanum [Origanum floribundum Munby from Blida (O.f B), Origanum floribundum Munby from Guelma (O.f G), and Origanum vulgare L. subsp. glandulosum (Desf.) from Jijel (O.g)], and evaluate their Acaricidal activity against Varroa Destructor. The results revealed significant variations in phenolic contents among the different oregano oils. Oregano oils, specifically Origanum floribundum Munby from Guelma and Origanum floribundum Munby from Blida, both rich in carvacrol, exhibited acaricidal efficacy comparable to the chemical acaricide Bayvarol. Conversely, Origanum glandulosum (Desf.) oil from Jijel displayed lower efficacy. These findings pave the way for future studies aimed at developing and optimizing natural acaricides, promoting a more environmentally and bee-friendly approach in apiculture.
... Maia & Moore 2011;Pavela 2016;Lengai et al. 2020). These botanically-derived crop protection agents are generally considered less environmentally harmful than synthetic biocides, with reduced longevity of effects, lower risk to users, and fewer non-target effects (Regnault-Roger et al. 2012;Pavela & Benelli 2016;Isman 2020). ...
... These insecticides, such as essential oils (EOs), have the potential to mitigate adverse effects on both non-target organisms and the environment. 22,23 Although EOs activity has been studied on many insect species, research on their effect when administered at low doses is still limited. 24 Low dosages of green pesticides have been shown to influence insect life span, development, sex, ratio, fertility, fecundity and behavioral features. ...
Pesticide exposure, even at low doses, can have detrimental effects on ecosystems. This study aimed at validating the use of machine learning for recognizing motor anomalies, produced by minimal insecticide exposure on a model insect species. The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), was exposed to food contaminated with low concentrations of Carlina acaulis essential oil (EO). A deep learning approach enabled fly pose estimation on video recordings in a custom-built arena. Five machine learning algorithms were trained on handcrafted features, extracted from the predicted pose, to distinguish treated individuals. Random Forest and K-Nearest Neighbor algorithms best performed, with an area under the receiver operating characteristic (ROC) curve of 0.75 and 0.73, respectively. Both algorithms achieved an accuracy of 0.71. Results show the machine learning potential for detecting sublethal effects arising from insecticide exposure on fly motor behavior, which could also affect other organisms and environmental health.
... The chemical composition of essential oils depends on environmental factors (soil type, moisture, mechanical damage, crops, and ecological and geographical origin), genetic factors, age, and harvesting season. These factors could explain the variation in chemical composition in different studies (Kunle et al. 2012;Pavela and Benelli, 2016). ...
... These natural pesticides are important to the agri-food sector because they generally have multiple modes and sites of action and target multiple species. Also, since they derive from natural sources, they often do not lead to the development of resistant strains (Pavela and Benelli 2016). They can also biodegrade to non-toxic compounds and have low adverse effects on non-target organisms (Assadpour et al. 2023). ...
Nature is a source of biologically active products that can act as fungicides, bactericides, acaricides, herbicides and insecticides. However, the application of these biopesticides can be challenging because they are generally insoluble in aqueous phases, highly volatile and unstable. One strategy to promote their use is their encapsulation into natural hosts, cyclodextrins. Cyclodextrins are food-grade and readily biodegradable oligosaccharides obtained from the enzymatic degradation of starch. Encapsulation in cyclodextrins would offer many advantages such as increased solubility, lower release rates and protection against chemical and physical degradation. Herein, we review the efficacy of cyclodextrin/natural compound inclusion complexes for crop protection. We discuss preharvest treatment and the different stages of the postharvest handling such as storage, distribution, packaging and marketing.
... The number of Denguerelated deaths is estimated to be around 40,000 annually [3] . Over the years, people have been utilizing natural remedies like neem leaves and flowers of Chrysanthemum cinerariaefolium to combat arthropod pests effectively [4] . While pesticides are essential tools in controlling insect pests that affect both agriculture and public health, their indiscriminate use can lead to adverse consequences [5] . ...
Mosquitoes are notorious vectors of severe diseases, posing significant threats to human health. Although pesticides are commonly used for mosquito control, their indiscriminate application can harm the environment and non-target organisms. Consequently, alternative strategies, such as plant-based mosquitocides, are gaining interest. This study evaluated the larvicidal efficacy of methanolic leaf extracts from Vitex negundo and Argemone mexicana against the fourth instar larvae of Anopheles subpictus. The extracts were analyzed for phytochemical compositions. Larvicidal bioassay showed concentration-dependent activity of both extracts against An. subpictus. V. negundo extract exhibited 86.36% mortality at 400 ppm, while A. mexicana extract showed 83.33% mortality at the same concentration. Probit analysis determined LC50 and LC90 values for V. negundo as 217.06 ppm and 404.32 ppm, respectively, and for A. mexicana as 224.45 ppm and 420.34 ppm, respectively. These findings suggest the potential of V. negundo and A. mexicana as natural larvicidal agents against An. subpictus.
... Recently, a growing number of essential oils (EOs) from plants have been tested against a wide range of pest insects, showing promising results due to their high effectiveness, different mechanisms of action, low toxicity on non-target vertebrates, and potential valorization of their byproducts as nanopesticides. 4 The need to find alternatives to synthetic pesticides, which have harmful effects on human health and the environment, has encouraged research on biopesticides. A. pubescens EO, with its interesting bioactive components, could be valorized in agriculture as a potential natural pest control agent. Mawussi et al. 5 demonstrated the insecticidal activity of A. pubescens against the coffee berry borer, while Bohounton et al. 6 reported its effectiveness against the mosquito A. gambiae. ...
Aeollanthus pubescens Benth. (Lamiaceae) is a herbaceous plant that is native to West Africa. It is commonly used in cooking and traditional healing in some parts of Togo and Benin. This study analyzed the chemical compositions of essential oils obtained from different parts of Togo (Kozah, Est-Mono, and Ogou) using gas chromatography-mass spectrometry. Additionally, the study investigated the bioactivity of essential oils and water extracts on the cowpea weevil Callosobruchus maculatus, plant parasitic nematode Meloidogyne incognita, and two plant seeds, Sesamum indicum, and Pennisetum glaucum, regarding germination inhibition. The results showed that the major components of the different essential oils were thymol (55.02%) and thymol acetate (20.03%) for Kozah, D-fenchone (65.05%) for Est-Mono, and thymol (29.48%), carvacrol (20.93%), thymol acetate (16.98%), and carvacryl acetate (13.14%) for Ogou. The Est-Mono essential oil was the most effective in controlling cowpea weevils with an EC 50 value of 3.1 ± 0.6 µL/L air. Kozah and Ogou essential oils showed more potent nematicidal activity with EC 50/72h values of 305.4 ± 7.3 mg/L and 275.6 ± 2.6 mg/L, respectively, while Est-Mono essential oil did not exhibit any activity. Finally, the Kozah and Ogou essential oils were found to inhibit the germination of dicotyledonous S. indicum seeds by more than 80% at 10 mg/mL, while less germicidal activity was observed on the monocotyledon P. glaucum from the different essential oils. These findings suggest that extracts of A. pubescens could be used in agriculture as a biopesticide.
... Also, most essential oils have low mammalian toxicity compared to synthetic insecticides and are considered to be eco-friendly (Mossa, 2016). Essential oils have neurotoxic activity in insects due to their ability to inactivate acetylcholinesterase (AChE), modulate the octopaminergic system, and bind to gamma-aminobutyric acid (GABA) receptors (Pavela, Benelli, 2016). In addition to target pest mortality, the studies conducted over the past few years have determined the toxic effects of essential oils on a wide range of pests. ...
The experiment was conducted in the Entomology The aim of the study was to determine the toxic effects of five essential oils on five important biological control agents. The commercially obtained essential oils of carrot, wintergreen, ginger, wormwood, and clove were shown to be toxic to biological control agents Orius laevigatus, Nesidiocoris tenuis, Macrolophus pygmaeus, Encarsia formosa, and Eretmocerus eremicus in three doses: 0.125, 0.25, and 0.5 v/v. After 3 hours, for the predator O. laevigatus, the most effective (100%) oils were wintergreen and clove oils, while for N. tenuis, the most effective were wintergreen (100%), wormwood (100%), and clove (97%) ones. After 24 hours, ginger oil showed a 95% mortality effect on M. pygmaeus. The parasitoids E. formosa and E. eremicus were less affected by the oils, only wormwood oil had a slightly deleterious effect on the parasitoids E. formosa and E. eremicus (mean 53% and 43%, respectively).
... However, the rapid evolution of resistance to acaricides in spider mites has also been recorded 11, 12 . In addition, they also showed detrimental effects on native phytoseiid populations inhabiting cultivated plants, causing major problems in Integrated Pest Management (IPM) strategies [13][14][15] , leading researchers to focus their interest on botanical-based products [16][17][18] . ...
BACKGROUND
Tetranychus urticae Koch , is a polyphagous and damaging pest, presenting several resistant populations worldwide. Among new and more environmentally friendly control tools, botanical pesticides represent a valuable alternative to synthetic ones within IPM strategies. Accordingly, we investigated on the lethal and sub‐lethal effects of the polyacetylene carlina oxide isolated from Carlina acaulis (Asteraceae) on T. urticae and on its natural enemy, the predatory mite, Neoseiulus californicus (McGregor).
RESULTS
Carlina oxide (98.7% pure compound) was used for acaricidal tests on eggs, nymphs, and adult females of T. urticae, (concentrations of 312.5, 625, 1250, 2500 and 5000 μL/L), and eggs and females of N. californicus (1250 and 5000 μL/L on eggs and females, respectively). Behavioral two‐choice tests were also conducted on phytoseiid females. Carlina oxide toxicity was higher on T. urticae females than nymphs (LD 50 1145 and 1825 μL/L, respectively), while egg mortality and the mean hatching time were significantly affected by all tested concentrations. A decreasing daily oviposition rate of T. urticae was recorded with concentrations ranging from 625 to 5000 μL/L, while negative effects on the population growth rate were recorded only with the three higher concentrations (1250, 2500 and 5000 μL/L). No toxic effect to N. californicus females was found, but a strong repellent activity lasting for 48 h from applications was registered.
CONCLUSION
Carlina oxide reduced longevity and fecundity of T. urticae adults, but not of N. californicus . This selective property allows to propose it as a novel active ingredient of eco‐friendly acaricides for T. urticae management.
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... Relevant crop losses are due to damage caused by insect pests, and several international legislations urgently demand sustainable practices for their control. Over the past decades, EOs have been claimed as a potential pest control tool in IPM programs (Pavela & Benelli 2016). Similarly, secondary metabolites such as plant volatiles that mediate tritrophic interactions can be successfully exploited in agriculture to repel insect pests and lure beneficial arthropods (Turlings & Erb 2018). ...
Exploiting plant defense mechanisms is a promising tool for pest management in modern agriculture. Plant Essential Oils (EOs) are used for the sustainable control of agricultural pests; however, their impact on plant defense has been scarcely investigated. In this work, we study for the first time whether the spraying of EOs can activate plant defense mechanisms in sweet pepper. The olfactory capacity of Encarsia formosa (Hymenoptera: Aphelinidae) to respond to defense- activated plants was used to select garlic and peppermint EOs among nine EOs sprayed on sweet peppers. The expression level of defense-related genes in plant tissues and the phytotoxicity were measured in response to EO foliar applications. Moreover, the olfactory responses of the herbivores, Bemisia tabaci (Hemiptera: Aleyrodidae) and Frankliniella occiden- talis (Thysanoptera: Thripidae), and their natural enemies, Orius laevigatus (Hemiptera: Anthocoridae) and Nesidiocoris tenuis (Hemiptera: Miridae), to EO induced plant volatiles were also investigated. The gene expression analysis revealed activated jasmonic and salicylic acid defense signaling pathways in EO-sprayed sweet pepper plants and a negligible phy- totoxic effect was recorded. Choice tests revealed varying behavioral responses in selected insect models when plants were treated with garlic and peppermint EOs in different concentrations. Our results suggest that garlic and peppermint EO spray applications can enhance the defense mechanisms of sweet peppers and have a cascading bottom-up effects on the associ- ated food chain. These initial findings provide a foundation for the future development of Integrated Pest Management strategies to protect solanaceous crops.
... Consequently, searching for eco-friendly acaricides is a pressing need 12,16,67 . Besides their pesticidal effects, botanicals have fungicidal, bactericidal, and antioxidant properties; therefore, they are used in medicine and cosmetics 15,24,32,49 . There are few studies on the efficacy of herbal extracts against H. dromedarii 10,78-81 and very rare studies tested their effect on its reproductive potential 50 . ...
Hyalomma dromedarii is an important tick species infesting livestock. This work evaluated the novel adulticidal, insect growth-regulating, and enzymatic efficacy of ethanol plant extracts of Aloe vera and Rheum rhabarbarum and their nanoemulsions against males and engorged females of the camel tick, H. dromedarii. The physicochemical properties of nanoemulsions were evaluated. The High-Performance Liquid Chromatography (HPLC) analyses indicated that the extracts contained polyphenols and flavonoids, which could enhance their acaricidal effect. Dynamic light scattering (DLS) of the nanoemulsions of A. vera and R. rhabarbarum were 196.7 and 291 nm, whereas their zeta potentials were − 29.1 and − 53.1 mV, respectively. Transmission electron microscope (TEM) indicated that nanoemulsions showed a regular spherical shape (less than 100 nm). Fifteen days post-treatment (PT) with 25%, the mortality% of A. vera and R. rhabarbarum were 88.5 and 96.2%, respectively. Five days PT, the median lethal concentration values of A. vera, R. rhabarbarum, and their nanoemulsions were 7.8, 7.1, 2.8, and 1.02%, respectively, and their toxicity indices were 91.02, 100, 36.4, and 100%, respectively. Their median lethal time values PT with 3.5% were 6.09, 5.09, 1.75, and 1.34 days, respectively. Nanoemulsions enhanced the efficacy of the crude extract 1–7 folds, 5 days PT, and accelerated their speed of killing ticks 2–4 times. The total protein and carbohydrates, Acetylcholinesterase, Alpha esterase, and Amylase were affected PT. The reproductive potential of engorged females was adversely impacted. In conclusion, the novel A. vera and R. rhabarbarum extracts were promising acaricides, and their nanoformulations enhanced their efficacies.
... In the CT bioassay, when an insect comes into direct contact with tannic acid, the cell membranes are disrupted; the cuticle's chitin and wax dissolve, and the respiratory openings are blocked, which ultimately results in the death of the insect [46]. When compared with the tested brown seaweed crude and fractions, it was demonstrated using S. polypodioides against A. devastans adults ( Table 6) and nymphs ( Table 8) that standard tannic acid against adults (Table 6) and gallic acid against nymphs are needed in very low concentrations to cause insect mortality (Table 8). ...
Citation: Petchidurai, G.; Sahayaraj, K.; Al-Shuraym, L.A.; Albogami, B.Z.; Sayed, S.M. Insecticidal Activity of Tannins from Selected Brown Macroalgae against the Cotton Leafhopper Amrasca devastans. Plants 2023, 12, 3188. https://doi. Abstract: Seaweeds, also known as marine macroalgae, are renewable biological resources that are found worldwide and possess a wide variety of secondary metabolites, including tannins. Drifted brown seaweed (DBSW) is particularly rich in tannins and is regarded as biological trash. The cotton leaf hopper Amrasca devastans (Distant) has caused both quantitative and qualitative losses in cotton production. Drifted brown seaweeds (DBSWs) were used in this study to extract, qualitatively profile, and quantify the levels of total tannins, condensed tannins, hydrolyzable tannins, and phlorotannins in the seaweeds; test their insecticidal activity; and determine the mechanism of action. The largest amount of tannin extract was found in Sargassum wightii Greville (20.62%) using the Soxhlet method (SM). Significantly higher amounts of hydrolyzable tannins (p = 0.005), soluble phlorotannins (p = 0.005), total tannins in the SM (p = 0.003), and total tannins in the cold percolation method (p = 0.005) were recorded in S. wightii. However, high levels of condensed tannins (CTAs) were observed in Turbinaria ornata (Turner) J. Agardh (p = 0.004). A. devastans nymphs and adults were examined for oral toxicity (OT) and contact toxicity (CT) against DBSW tannin crude extract and column chromatographic fractions 1 (Rf = 0.86) and 2 (Rf = 0.88). Stoechospermum polypodioides (J.V. Lamouroux) J. Agardh crude tannin was highly effective against A. devastans using the OT method (LC 50 , 0.044%) when compared with the standard gallic acid (LC 50 , 0.044%) and tannic acid (LC50, 0.122%). Similarly, S. wightii fraction 2 (LC 50 , 0.007%) showed a greater insecticidal effect against A. devastans adults in OT than gallic acid (LC 50 , 0.034%) and tannic acid (LC 50 , 0.022%). The mechanism of action results show that A. devastans adults treated with crude tannin of T. ornata had significantly decreased amylase, protease (p = 0.005), and invertase (p = 0.003) levels when compared with the detoxification enzymes. The levels of glycosidase, lactate dehydrogenase, esterase, lipase, invertase, and acid phosphate activities (p = 0.005) of S. wightii were reduced when compared with those of the Vijayneem and chemical pesticide Monocrotophos. In adult insects treated with LC 50 concentrations of S. wightii tannin fraction 1, the total body protein (9.00 µg/µL) was significantly reduced (OT, LC 50-0.019%). The SDS-PAGE analysis results also show that S. wightii tannin fraction 1 (OT and CT), fraction 2 (OT), and S. polypodioides fraction 2 (CT) had a significant effect on the total body portion level, appearance, and disappearance of some proteins and polypeptides. This study shows that the selected brown macroalgae can be utilized for the safer management of cotton leaf hoppers.
... Most recent statistics holds that 75% of biopesticides used consist of Bt-based products (Samada et al., 2020). Neem has proven to be the most widely used botanical biopesticide (Rodgers, 1993;Leng et al., 2011;Pavela, 2014;George et al., 2014;Pavela and Benelli, 2016;Huang et al., 2020). Moreover, neem has demonstrated multiple modes of action by acting as an antifeedant, sterilant, ovicidal and insecticide. ...
... In higher plants, more than 23,000 terpene structures have been found (Pavela andBenelli 2016, Trindade, Pedro et al. 2018). The terpenes or isopropenoids are secondary metabolites present in essential oils. ...
The genus Thymus from the Lamiaceae family has more than 300 species distributed worldwide, including in Europe and Asia. 18 Thymus species have been identified in Iran's flora, of which 4 are endemic to Iran. Thymus species are known as medicinal plants due to their biological and medicinal properties. Thyme has many biological activities, including antimicrobial, antioxidant and anti-inflammatory effects. Therefore, Thymus species interest many pharmaceutical, food and cosmetic industries. Throughout the evolution of plants, essential oils have played a crucial part in the direct and indirect defenses of plants against possible predators and pathogens, as well as in the processes of plant reproduction by attracting pollinators and disseminators to the seeds The present study was conducted to investigate the chemical composition of essential oils of Thymus species in Iran. The information and findings in this review were obtained from scientific databases and search engines, including Web of Knowledge, PubMed, ScienceDirect, Medline, Reaxys and Google Scholar. In this research, we investigated different species of Thymus collected wild and cultivated in different parts of Iran. The results showed that the main composition of thyme included thymol, carvacrol, geraniol, γ-terpinene and linalool. The conclusion of this review shows that plant compounds are a promising source of bioactive compounds that can be explored for development against diseases and complications associated with its chemical drugs.
... In recent years, scientific research has aimed at the establishment of new technologies intended at increasing the yield of agricultural crops and quality of products, not forgetting the progressive decrease in land availability, water scarcity, and increasing climatic changes. Scientific development involves advances in the field of phytogenetics, searching for more resistant seeds with a higher yield, in the management of grazing, as well as about the development of biopesticides based on natural products (Pavela and Benelli 2016;Isman 2020). ...
Plant-borne secondary metabolites are attracting high interest for their potential use in agricultural applications, with special reference to the control of arthropod pests. In the present work, the structural elucidation of glycosylated diterpenoid carboxyatractyloside (2) isolated from the roots of Chamaeleon gummifer Cass. (Asteraceae) is reported by means of spectroscopic and spectrometric techniques. Complete identification occurred thanks to one- and two-dimensional NMR experiments, assigning the single protons and carbons, and the stereochemistry by the NOESY correlations. Carboxyatractyloside (2), together with two ent-kaurenes atractyloside (1) and atractyligenin (3), extracted from the roots of C. gummifer, have been tested for their acaricidal and oviposition inhibition activity against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) Notably, compounds 1–3 were toxic to T. urticae, leading to significant mortality, oviposition inhibition, reduced hatchability of eggs, and natality inhibition. However, at the lowest dose (12.5 µg cm⁻²) compound 2 was the most effective, leading to mortality > 60% after 5 days exposure, inhibiting oviposition by > 70% and egg hatching by 33%; it also reduced natality by 80%. Overall, these compounds represent valuable candidates to develop novel acaricides for crop protection. Further research on how to develop stable formulations for field use, as well as on non-target effects of these compounds on pollinators and mite biocontrol agents, is ongoing.
... Agrochemical industries are focusing on the development of novel eco-friendly pesticides and plant-derived products are gaining increasing importance in this field (Isman, 2020). Crucial factors for their real-world employment are efficacy of these products and availability of the raw material from which they are obtained (Pavela and Benelli, 2016). Given the results reported in this study and taking into account the already established large-scale cultivation of the plant for various purposes, we believe that this extract might be considered as a new candidate for the development of grain protectant to manage stored-product insect pests. ...
The evaluation of sublethal effects of botanical insecticides is a key tool to develop new strategies in pest management programs, since they potentially affect insect physiology and behavior. Acmella oleracea (L.) R.K. Jansen (Asteraceae) is a medicinal food plant widely used on an industrial level and with recognized efficacy against various arthropod pests and vectors. In this study, the sublethal effects of an A. oleracea hexane extract (HE) on the mobility, mating, and behavior of Prostephanus truncatus were investigated. The concentrations that killed 10, 30 and 50% of the exposed adults were 7.01, 19.5, and 39.5 mg/mL, respectively. The walking behavioral traits, i.e., duration and number of stops, and upside down (i.e., the time spent by the beetle on its back), were significantly higher in the adults exposed to LC 30 than LC 10 and control ones. The highest velocity was recorded for control beetles (21.5 mm/s), followed by LC 10-(20.7 mm/s) and LC 30-treated ones (21.2 mm/ s). Concerning lateralization, P. truncatus males were right biased during the mating sequence. Sublethal concentrations negatively affected the mating success of LC 10-and LC 30-exposed males in comparison with control ones. Overall, our findings outlined that the exposure of P. truncatus adults to A. oleracea HE LC 10 and LC 30 deeply affected their walking and mating behavior, a fact that should be considered further when optimizing pest management tactics in storages.
... With increased worries about pesticide residues in agricultural crops and the ecosystem, greater emphasis has been placed on developing non-chemical, healthier, and more ecofriendly alternatives to synthetic pesticides, with natural plant products receiving a lot of attention in this regard (Benelli et al., 2019;Benelli and Maggi, 2022;Assadpour et al., 2023). Among botanicals with pesticide properties, essential plant oils (EOs) are experiencing a revival because many are sustainable, pest-specific; have low human and mammalian toxicity, biodegrade rapidly into non-toxic metabolites and exert their action via multiple target sites; hence the chance for developing resistance in targeted pests become rare (Koul et al., 2008;Pavela and Benelli, 2016;Isman, 2020;Assadpour et al., 2023). In literature, EOs possess remarkable bio-insecticidal, antifeeding, repellent, and growth inhibiting properties against insects infesting cereals in stores, including the granary weevil (Nenaah, 2014a;Kanda et al., 2017;Alkan et al., 2018Alkan et al., , 2020Feng et al., 2022;Karabörklü and Ayvaz, 2023). ...
In the pursuit of searching for novel and environmentally benign insecticides to minimize the environmental risks of synthetic pesticides, essential oil (EO) of Salvia officinalis L., the so-called common sage, was hydro-distilled and analyzed using gas chromatography-flame ionization detection (GC-FID) and Gas chromatography-Mass spectrometry (GC-MS). The monoterpenes, α-thujone (26.8%), camphor (19.9%), and 1,8-cineole (13.4%) were identified as the key fractions. Oil-in-water nanoemulsion (NE) was developed adopting a green low energy method, then characterized for thermodynamic stability. The EO, the NE and monoterpenes showed insecticidal bioactivity against the granary weevil, Sitophilus granarius L. The NE caused the strongest contact bioactivity against larvae (LC 50 =7.2 µL/cm 2) after 72 h of exposure. At the same assaying conditions, EO (LC 50 = 14.1 µL/ cm 2) and camphor (19.3 µL/cm 2) exhibited promising bioactivities. For adults, the LC 50's of NE, EO and camphor after 72 h of exposure were 5.8, 9.2, and 19.8 µL/cm 2 , respectively. Upon fumigation, the NE, EO and camphor were the most effective as fumigants, where LC 50 values after 72 h larval exposure were 8.1, 11.0, and 14.0 µL/L, respectively, and for adult were 5.4, 9.6, and 12.1 µL/L, respectively. The phytochemicals effectively repelled the weevils at low concentrations, and considerably inhibited the activity of acetylcholinesterase (AChE). None-target evaluations proved that the phytochemicals and NE were safe for earthworm, Eisenia fetida (Savigny, 1826) at a limit concentration of 200 mg/kg soil, and the albino rat at an oral limit dose of 4500 mg/kg body weight, except for α-thujone. The test phytochemicals were non-phytotoxic to wheat grains at concentrations reached 150 µL/ml. Results provide evidence for a potentiality for using sage EO, particularly at its nanoscale, as ecofriendly grain protectant against the granary weevil.
Aedes aegypti mosquitoes represent a significant public health hazard as they serve as vectors for a variety of arboviral infections, including Dengue, Zika, and Chikungunya. This necessitates the development of efficacious vector control strategies. The current study conducted at the Medical Entomology laboratory of the Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan, evaluated the potential use of locally sourced aqueous-based plant extracts against different life stages of Aedes aegypti mosquitoes. The utilization of plant extracts, including Parthenium hysterophorus, Nicotiana tabacum, Melia azedarach, and Fagonia indica, offers a potentially effective and ecologically sustainable strategy for pest control. The above excerpts present environmentally friendly alternatives that are biodegradable and have a little impact on the environment. These alternatives are in contrast to synthetic pesticides and contribute to the promotion of sustainable and ecologically responsible methods of pest control. The study tested various plant extracts, specifically those from Parthenium hysterophorus, Nicotiana tabacum, Melia azedarach, and Fagonia indica. These were examined at high concentrations to assess their toxicity to the mosquito species. The extract of P. hysterophorus demonstrated impressive efficacy, displaying 100 % effectiveness across all mosquito life stages. This was closely followed by N. tabacum, F. indica, and M. azedarach in decreasing order of efficacy. To better understand the potency of these plant extracts, their LC50 values were determined after 24, 48, and 72 h post-exposure. LC50 values, a common measure in toxicology, indicate the concentration at which 50 % of the test organisms are killed. Among the tested extracts, M. azedarach exhibited the highest LC50 values (1.703 %, 2.142 %, 2.640 %), implying lower toxicity, while P. hysterophorus showed the lowest LC50 values (0.120 %, 0.420 %, 0.975 %), indicating high toxicity to Aedes aegypti mosquito larvae. Based on the comparative analysis of toxicity, the extracts' efficiency order was established as follows: P. hysterophorus extracts > N. tabacum extracts > F. indica extracts > M. azedarach extracts. These findings suggest that P. hysterophorus and N. tabacum, particularly at a 3 % concentration, hold promising potential as components in eco-friendly integrated vector management (IVM) strategies. This approach would serve as an alternative to the traditional reliance on synthetic pesticides, which often pose environmental and health risks due to their residual toxicity.
Fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a widely distributed and important pest of corn crops. However, the improper use of the conventional synthetic organophosphate and neonicotinoids pesticides to control S. frugiperda has led to resistant populations. Herein, the biological activities of some plant essential oils against S. frugiperda were determined to provide theoretical basis for the biological control of S. frugiperda . Our results showed that peppermint essential oil at 4.00% concentration showed the obvious ovicidal activity (96.00%) against S. frugiperda eggs, and lemon essential oil at 1.00% concentration had the greatest antifeedant activity (99.11%) against S. frugiperda larvae. Meanwhile, patchouli essential oil and patchouli essential oil at 4.00% concentration revealed remarkable fumigation and contact activities against S. frugiperda larvae at 96 h with the inhibition rates of 93.33% and 95.67%, respectively. In addition, the combination of patchouli essential oil and indoxacarb (in a ratio of 5:1) demonstrated the most effective synergistic effect (97.67%) on S. frugiperda larvae at 96 h. Moreover, the average dwell times of rosemary essential oil at 0.50% concentration against S. frugiperda larvae as well as citronella essential oil at 0.25% and 2.00% concentrations, patchouli essential oil at 1.00% and 4.00% concentrations, and lemon essential oil at 0.50% and 1.00% concentrations against both S. frugiperda male and female adults were all 0 s, indicating that some plant essential oils revealed excellent repellent activity against S. frugiperda . These findings could help to guide the development of new insecticides for the biological control of S. frugiperda .
The present study aimed to determine the effects of three different doses of three thyme essential oils on Sitophilus oryzae (L.) and Sitophilus granarius (L.) (Coleoptera: Curculionidae). The present study was conducted under controlled laboratory conditions (25°C temperature and 65% relative humidity) in 2020. Various thyme varieties (Origanum majorona (L.), Origanum saccatum P.H. Davis, Thymbra spicata var spicata L. (Lamiaceae)), cultivated in Diyarbakır province ecological conditions were employed in the study. After the 4 th day of the experiment, the highest mortality rates (100%) were observed with the highest doses of T. spicata var spicata and O. majarona on S. granarius adults, while the mortality rate was 73.75% with O. saccatum. The LC90 values for T. spicata var. spicata, O. majarona, and O. saccatum were 0.9, 0.1, and 1.3 µl/ml respectively. After the 4 th day, 100% S. oryzae adult mortality was observed with higher doses of O. majarona (0.5%; 1% v/v), while 1% (v/v) T. spicata var spicata dose led to a 72.50%, and 1% (v/v) O. saccatum oil dose led to 46.25% mortality.
Triatoma infestans, es el principal vector de la enfermedad de Chagas en Bolivia y países vecinos. Su control se basa principalmente en tratamientos con insecticidas sintéticos, pero existen pocos estudios sobre los efectos de los repelentes naturales en esta especie. El objetivo de este estudio fue evaluar la actividad repelente de los aceites esenciales (AEs) de especies nativas de Chile, Argentina y Bolivia: Amomyrtus meli (Phil.) D. Legrand & Kausel [Myrtaceae], Peumus boldus Molina [Monimiaceae] y Senecio nutans Sch. Bip. [Asteraceae] obtenidos por hidrodestilación. La arena experimental estuvo constituida por un papel filtro que tenía una mitad tratada con acetona y la otra mitad con una solución de AE en acetona. Como control positivo se utilizó N, N-dietil-3-metilbenzamida (DEET). Se colocó una ninfa de quinto estadío de T. Infestans sobre el papel y, durante 10 minutos se registró el tiempo que el insecto estuvo en la zona tratada con AE o en la zona alternativa. Se evaluaron cinco concentraciones de cada AE entre 4.12, 8.25, 16.5, 33.0 y 66.0 µg/cm2. Los tres AEs produjeron un efecto repelente sobre T. infestans, y su perfil de repelencia fue similar al de la DEET. Futuras investigaciones deberían centrarse en el estudio de la repelencia individualizada de compuestos específicos de los AE además de las interacciones toxicológicas entre ellos cuando se aplican como mezclas simples. En particular, las interacciones sinérgicas serían un fenómeno atractivo para el desarrollo de productos repelentes de triatominos.
In this study, essential oils (EOs) of Citrus limon (L.), Citrus sinensis (L.) (Sapindales: Rutaceae), Allium sativum (L.) (Asparagales: Amaryllidaceae) and Brassica nigra (L.) (Brassicales: Brassicaceae) were evaluated for their insecticidal effects on the green peach aphid Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae). The lethal and sublethal effects of these EOs on M. persicae were studied under laboratory conditions. This study was conducted at Yozgat Bozok University, Faculty of Agriculture, Department of Plant Protection in 2023. The experiments were evaluated at different concentrations for 24 hours after treatment. The lethal concentrations (LC50, LC90) of the EOs were calculated based on the data obtained. The life table parameters of newly born aphids were studied at sublethal concentrations (LC40, LC30) of EOs, and these parameters were calculated using the Euler-Lotka equation. The results show that the mortality rate increases with growing concentration of essential oils. The lethal concentration (LC50) of essential oils were calculated to be 3.47, 4.37, 4.51, and 5.16 µL/L, respectively. The sublethal concentrations (LC40, LC30) of essential oils caused an increase in adult longevity, a decrease in fecundity of surviving aphids and intrinsic rate of increase. From the data obtained, the EOs of C. limon and C. sinensis were more effective than other EOs in the study. It was found that other essential oils (A. sativum and B. nigra) may also be effective against M. persicae, even if their effect is low.
Potato late blight disease is caused by the oomycete Phytophthora infestans and is listed as one of the most severe phytopathologies on Earth. The current environmental issues require new methods of pest management. For that reason, plant secondary metabolites and, in particular, essential oils (EOs) have demonstrated promising potential as pesticide alternatives. This review presents the up-to-date work accomplished using EOs against P. infestans at various experimental scales, from in vitro to in vivo. Additionally, some cellular mechanisms of action on Phytophthora spp, especially towards cell membranes, are also presented for a better understanding of anti-oomycete activities. Finally, some challenges and constraints encountered for the development of EOs-based biopesticides are highlighted.
BACKGROUND
The push‐pull strategy is considered as a promising eco‐friendly method for pest management. Plant volatile organic compounds (PVOCs) act as semiochemicals constitute the key factor in implementing this strategy. Benzyl alcohol and geraniol, as functional PVOCs, were reported to regulate insect behavior, showing the potential application in pest control. Using geraniol as lead, a geraniol derivative 5i with fine repellent activity was discovered in our previous work. In order to explore novel, eco‐friendly aphid control agents, a series of benzyl geranate derivatives was designed and synthesized using 5i as the lead and benzyl alcohol as the active fragment.
RESULTS
Benzyl alcohol was firstly evaluated to have repellent activity to Acyrthosiphon pisum . Based on this repellent fragment, a series of novel benzyl geranate derivatives was rationally designed and synthesized using a scaffold‐hopping strategy. Among them, compound T9 , with a binding affinity ( Kd : 0.43 μM) and a substantial repellency of 64.7% against A. pisum , is the most promising compound. Molecule docking showed that hydrophobic and hydrogen‐bonding interactions substantially influenced the binding affinity of compounds with ApisOBP9. Additionally, T9 exhibited low‐toxicity to honeybees and ladybugs.
CONCLUSION
Using a simple scaffold‐hopping strategy combined with active fragment benzyl alcohol, a new derivative T9 , with high aphid‐repellent and low‐toxicity to non‐target organisms, can be considered as a novel potential eco‐friendly aphid control agent for sustainable agriculture.
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The present investigation aims to validate the larvicidal and antibacterial potential of Cladophora sp through in vitro and in silico approaches. The presence of phytoconstituents, functional groups and the compounds responsible for antibacterial and larvicidal activity were assessed through FT–IR and GC–MS analyses which unveiled the existence of active secondary metabolites, hydroxyl, alkane and carbonyl groups. The larvicidal and antibacterial activity of algal extract were examined and revealed complete mortality and substantial zone of inhibition was observed against Culex quinquefasciatus and E. coli. To support the in vitro investigation in silico studies were performed. Molecular docking investigations of the selected compounds from GC–MS which exhibited favorable agreement with drug likeness and ADMET properties indicated robust interactions with the larvicidal and bacterial proteins showcasing considerable binding affinities. Notably, 1,2,4-Oxadiazole, 3-(1,3-benzodioxol-5-yl)-5-[(4-iodo-1H-pyrazol-1-yl) methyl]- exhibited strong interactions with the target proteins. Density Functional Theory revealed that the energy gap of the lead compound was reduced and substantiates the occurrence of intermolecular charge transfer. Molecular Dynamic simulations confirms the stability and flexibility of the lead compound. Hence, this investigation offers computational perspectives on the molecular interactions of Cladophora sp, suggesting its suitability as a promising biocontrol agent.
BACKGROUND
The study on plant antibacterial components (carvacrol) has recently become a hot topic in modern farming. Carvacrol industrial applications are restricted by their physicochemical instability and partial solubility in water. In the present study, an ultrasonic emulsification method was used to prepare carvacrol nanoemulsion (CAR‐NE) employing nonionic surfactants. The CAR‐NE was characterized using a dynamic light scattering (DLS) instrument and TEM. The goal of this work was nanoencapsulation of carvacrol to improve its aqueous solubility and preservation of encapsulated compound against climatic conditions. Another aim of the present study was the evaluation of the growth‐promoting effects and antibacterial potential of CAR‐NE against bacterial leaf blight of cluster bean.
RESULTS
CAR‐NE had shown hydrodynamic diameter, zeta potential, and polydispersity index (PDI) of 43.88 ± 4.30 nm, ‐47.8 ± 0.23 mV, and 0.246 ± 0.04 respectively. The spherical shape morphology of CAR‐NE is confirmed by TEM imaging. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the CAR‐NE were 20μL/mL and 160μL/mL respectively against Xanthomonas axonopodis pv . Cyamopsidis . Additionally, the antibacterial potential of CAR‐NE was evaluated for controlling bacterial blight of cluster bean in fields. Disease severity in the negative control plants (water) was 84%, but the disease severity in the CAR‐NE (160 μL/mL) was remarkable (14%) which was nearly the same as the positive control (streptomycin sulphate).
CONCLUSION
The shelf‐life of CAR‐NE was two months at room temperature without any appreciable changes in hydrodynamic diameter and zeta potential. Consequently, plants treated with CAR‐NE (160μL/mL) showed substantial improvement in plant growth.
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Fusarium wilt of banana (FWB) caused by soil-borne Fusarium oxysporum f.sp. cubense (Foc) , is a widely distributed disease that generates devastating losses in banana. The most aggressive Foc tropical race 4 (TR4), attacks Cavendish clones and a diverse range of other banana varieties. Management practices to suppress Foc are emerging, however they are challenging. Therefore, enhancing biological control activities could potentiate FWD control practices. Here we determine the antifungal synergistic effect of plant-based cinnamon ( Cinnamomum zeylanicum) extract and Bacillus tequilensis EA-CB0015 cyclic lipopeptides against Fusarium sp. strains in vitro and in banana plants in greenhouse. We found, through a bioprospecting assay of 17 plant-based natural extracts, that cinnamon was highly active against Foc isolate IB (race 1). Furthermore, cinnamon and cyclic lipopeptides inhibited different Fusarium spp. strains belonging to race 1 and TR4, and their combination increased 1.4-fold the effect of the single extracts in vitro . Our results demonstrate that soil concentration of F. odoratissimum TR4-II5 was reduced by 78.5% with the combination treatment in a soil microcosm system. Although, while the combination reduced external FWB symptoms, only cinnamon extract had a significant impact on internal symptoms in plants. Taken together, the biological control effect of cyclic lipopeptides with cinnamon extract on Fusarium spp. supports their function towards increasing soil health and reducing disease intensity and suggests that the combination enhances the effect of the single extracts.
Rhipicephalus microplus (Ixodidae, canestrini, 1888) is an invasive ectoparasite of cattle which causes high economic losses in emerging countries such as Brazil. Phytochemical compounds have been tested as an alternative to synthetic acaricides due to potentially lower mammalian toxicity. This study evaluated the acaricidal activity against R. microplus of the 2-methoxy-clovan-9-ol rich fraction obtained from Eugenia copacabanensis Kiaersk.leaves, a little known Myrtaceae species from the Brazilian Atlantic Forest. This fraction was obtained by maceration with methanol, partition with n-hexane and purification by normal-phase column chromatography. GC-MS, 1H and 13C NMR and IR analysis contributed to the identification of a major compound as the sesquiterpene 2-methoxy-clovan-9-ol, reported for the first time for the Myrtaceae family. The fraction was tested against R. microplus unfed larvae and engorged females and a 93% larval mortality was observed at the concentration of 50 mg mL-1. Lower concentrations of the solution tested demonstrated a significant difference in egg mass weight, hatching and control percentage. Experiments with 50.0 mg mL-1 showed significative results, with lower concentration and maximum efficacy for both assays. The IC50 values for unfed larvae and engorged females were 21.76 and 11.13 mg mL-1, respectively. These results were similar to those obtained in other studies with isolated botanical compounds and essential oils. The lower IC50 for engorged females than for unfed R. microplus larvae had also been described for other plant materials, including plants from the same Myrtaceae family. The present result suggested different mechanisms of action of the compound on the reproductive biology of engorged females, improving its effect against egg viability. These results are important for tick control, suggesting that 2-methoxy-clovan-9-ol could be a potential natural acaricidal product against both R. microplus unfed larvae and engorged females.
Triatoma infestans, is the main vector of Chagas disease in Bolivia and neighboring countries. Its control is mainly based on treatments with synthetic insecticides, but there are few studies on the effects of repellents on this species. This paper aimed at evaluating the repellent activity of essential oils (EOs) from native species of Chile, Argentina and Bolivia: Amomyrtus meli (Phil.) D. Legrand & Kausel [Myrtaceae], Peumus boldus Molina [Monimiaceae] and Senecio nutans Sch. Beep. [Asteraceae] obtained by hydrodistillation. The experimental sand consisted of a filter paper that had one half treated with acetone and the other half with an EO solution in acetone. As a positive control, N, N-diethyl-3-methylbenzamide (DEET) was used. A fifth instar nymph of T. infestans was placed on the paper and for ten minutes, the time that the insect was in the area treated with EO or in the alternative zone was recorded. Five concentrations of each EA between 4.12, 8.25, 16.5, 33.0 and 66.0 µg/cm2 were evaluated. All three EOs produced a repellent effect on T. infestans, and their repellency profile was similar to DEET. Future researches should focus on the study of the individualized repellency of the main components of the EO and the toxicological interactions between them when applied as simple mixtures. In particular, synergistic interactions would be an attractive phenomenon for the development of triatomine repellent products
The advent of the "Green Revolution" was a great success in significantly increasing crop productivity. However, it involved high ecological costs in terms of excessive use of synthetic agrochemicals, raising concerns about agricultural sustainability. Indiscriminate use of synthetic pesticides resulted in environmental degradation, the development of pest resistance, and possible dangers to a variety of nontarget species (including plants, animals, and humans). Thus, a sustainable approach necessitates the exploration of viable ecofriendly alternatives. Plant-based biopesticides are attracting considerable attention in this context due to their target specificity, ecofriendliness, biodegradability, and safety for humans and other life forms. Among all the relevant biopesticides, plant essential oils (PEOs) or their active components are being widely explored against weeds, pests, and microorganisms. This review aims to collate the information related to the expansion and advancement in research and technology on the applications of PEOs as biopesticides. An insight into the mechanism of action of PEO-based bioherbicides, bioinsecticides, and biofungicides is also provided. With the aid of bibliometric analysis, it was found that~75% of the documents on PEOs having biopesticidal potential were published in the last five years, with an annual growth rate of 20.51% and a citation per document of 20.91. Research on the biopesticidal properties of PEOs is receiving adequate attention from European (Italy and Spain), Asian (China, India, Iran, and Saudi Arabia), and American (Argentina, Brazil, and the United States of America) nations. Despite the increasing biopesticidal applications of PEOs and their widespread acceptance by governments, they face many challenges due to their inherent nature (lipophilicity and high volatility), production costs, and manufacturing constraints. To overcome these limitations, the incorporation of emerging innovations like the nanoencapsulation of PEOs, bioinformatics, and RNA-Seq in biopesticide development has been proposed. With these novel technological interventions, PEO-based biopesticides have the potential to be used for sustainable pest management in the future.
The mosquito larvicidal activity of Zanthoxylum monophyllum leaf essential oil (EO) and its major chemical constituents was tested against the three mosquito vectors Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus. In the EO of Z. monophyllum, it contains 36 compounds with the two major compounds being Germacrene D-4-ol (19.40 %) and α-Cadinol (12.30). The larvicidal activity of the essential oil against An. subpictus, Ae. albopictus and Cx. tritaeniorhynchus was determined and LC50 values were estimated at 41.50, 45.35 and 49.01 µg/mL, respectively. The two major compounds Germacrene D-4-ol and α-Cadinol were tested for acute toxicity against larvae of the three mosquito vectors. Germacrene D-4-ol showed a significantly higher efficacy compared to α-Cadinol. While LC50 for Germacrene D-4-ol ranged from 6.12 to 7.26 µg/mL, LC50 values for α-Cadinol were estimated in the range from 10.27 to 12.28 µg/mL. The EO, Germacrene D-4-ol and α-Cadinol were found safer to the non-target organism Gambusia affinis (LC50 = 4234.07, 414.05 and 635.12 µg/mL, respectively), which was manifested in the high suitability of the index/predator safety factor value, ranging from 86.36 for the least sensitive larvae of Cx. tritaeniorhynchus to 102.02 for the most sensitive larvae of An. subpictus.
The fight against mosquito-borne diseases is a challenge of huge public health importance. To our mind, 2015 was an extraordinary year for malaria control, due to three hot news: the Nobel Prize to Youyou Tu for the discovery of artemisinin, the development of the first vaccine against Plasmodium falciparum malaria [i.e. RTS,S/AS01 (RTS,S)], and the fall of malaria infection rates worldwide, with special reference to sub-Saharan Africa. However, there are major challenges that still deserve attention, in order to boost malaria prevention and control. Indeed, parasite strains resistant to artemisinin have been detected, and RTS,S vaccine does not offer protection against Plasmodium vivax malaria, which predominates in many countries outside of Africa. Furthermore, the recent outbreaks of Zika virus infections, occurring in South America, Central America and the Caribbean, represent the most recent of four arrivals of important arboviruses in the Western Hemisphere, over the last 20 years. Zika virus follows dengue (which slyly arrived in the hemisphere over decades and became more aggressive in the 1990s), West Nile virus (emerged in 1999) and chikungunya (emerged in 2013). Notably, there are no specific treatments for these arboviruses. The emerging scenario highlights that the effective and eco-friendly control of mosquito vectors, with special reference to highly invasive species such as Aedes aegypti and Aedes albopictus, is crucial. The concrete potential of screening plant species as sources of metabolites for parasitological purposes is worthy of attention, as elucidated by the Y. Tu’s example. Notably, plant-borne molecules are often effective at few parts per million against Aedes, Ochlerotatus, Anopheles and Culex young instars, can be used for the rapid synthesis of mosquitocidal nanoformulations and even employed to prepare cheap repellents with low human toxicity. In addition, behaviour-based control tools relying to the employ of sound traps and the manipulation of swarming behaviour (i.e. “lure and kill” approach) are discussed. The importance of further research on the chemical cues routing mosquito swarming and mating dynamics is highlighted. Besides radiation, transgenic and symbiont-based mosquito control approaches, an effective option may be the employ of biological control agents of mosquito young instars, in the presence of ultra-low quantities of nanoformulated botanicals, which boost their predation rates.
Insecticide resistance is one of the most important evolutionary phenomena for researchers. Overuse of chemicals has induced resistance in insect pests that ultimately has led to the collapse of disease control programs in many countries. The erroneous and inappropriate management of insect vectors has resulted in dissemination of many vector-borne diseases like dengue, malaria, diarrhea, leishmaniasis, and many others. In most cases, the emergence of new diseases and the revival of old ones can be related with ecological changes that have favored rapid growth of vector densities. Understanding molecular mechanisms in resistant strains can assist in the development of management programs to control the development and spread of resistant insect populations. The dominant, recessive, and co-dominant forms of genes encoding resistance can be investigated, and furthermore, resistance development can be addressed either by the release of susceptible strains or timely insecticide rotation. The present review discusses the resistance level in all important insect vectors of human diseases; the molecular basis of evolvement of resistance has also been discussed.
Mosquitoes (Diptera: Culicidae) are a key threat for millions of people worldwide, since they act as vectors for devastating parasites and pathogens. Mosquito young instars are usually targeted with organophosphates, insect growth regulators and microbial control agents. Indoors residual spraying and insecticide-treated bed nets are also employed. However, these chemicals have strong negative effects on human health and the environment. Newer and safer tools have been recently implemented to enhance control of mosquitoes. In this review, I focus on characterization, effectiveness, and non-target effects of mosquitocidal nanoparticles synthesized using botanical products (mosquitocidal nanoparticles, MNP). The majority of plant-fabricated MNP are silver ones. The synthesis of MNP is usually confirmed by UV-visualization spectroscopy, followed by scanning electron microscopy or transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction studies. Interestingly, plant-synthesized metal nanoparticles have been reported as effective ovicides, larvicides, pupicides, adulticides, and oviposition deterrents against different mosquito species of medical and veterinary importance. Few parts per million of different MNP are highly toxic against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti, and the filariasis mosquito Culex quiquefasciatus. However, despite the growing number of evidences about the effectiveness of MNP, moderate efforts have been carried out to shed light on their possible non-target effects against mosquito's natural enemies and other aquatic organisms. In the final section, particular attention was dedicated to this issue. A number of hot areas that need further research and cooperation among parasitologists and entomologists are highlighted.
The essential oils have been widely used as antiparasitical, bactericidal, fungicidal, antivirus and insecticidal. On the other hand the main method to control insect pest is using synthetic pesticides, but the development of insect resistance to this products, the high operational cost and environmental pollution have created the need for developing alternative approaches to control many insects pest, and in this sense the essential oils are an alternative to control many insects. This work is a review for the last five years, which shows the main essential oils from 30 botanical families with activity against coleopterans insect pest in stored grains. It was found that 22 species belong to the family Lamiaceae 17 of Asteraceae and 10 of Myrtaceae
The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC50 for the 2nd to 4th instar larvae was estimated as 26-27 mu L center dot L-1 and 15-19 mu L center dot L-1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)(50) was estimated as 9.3 mu L mL(-1) (spray test), 1.9 mu L L-1 (fumigation test) and 0.6 mu g cm(-2) (tarsal test), and for trans-Anethole as 8.1 mu L mL(-1) (spray test), 2.1 mu L L-1 (fumigation test) and 0.4 mu g cm(-2) (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)99 of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235 mffi depending on the larval instar, and from 9 to 180 mffi when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied. The essential oil and trans-Anethole were toxic for Daphnia magna (62-92% mortality) and significantly reduced its fertility at high concentrations (35-50 mu L mL(-1)) and long exposure (48 h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6 h) and/or lower concentrations (20 mu L mL(-1)). Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides.
The present investigation reports on the chemical composition of Cudrania tricuspidata fruit essential oil (CTEO) and examines its possible antimicrobial mode of action against food-borne pathogenic bacteria. The CTEO was obtained by hydrodistillation of C. tricuspidata fruits using a microwave-assisted extraction technique. Gas chromatography-mass spectrometry analysis of the CTEO resulted in the determination of 29 different compounds, representing 94.46% of the total oil. The CTEO (1000 μg/disc) showed potential antibacterial effect as diameters of inhibition zones (15.0 ± 0.1–21.0 ± 1.0 mm) against the tested food-borne pathogenic bacteria including Bacillus cereus ATCC 13061, Staphylococcus aureus ATCC 12600, Listeria monocytogenes ATCC 7644, Salmonella typhimurium ATCC 43174 and Escherichia coli O157:H7 ATCC 43889. The minimum inhibitory (MIC) and minimum bactericidal (MBC) concentration values of CTEO against the tested bacteria were found in the range of 250–1000 μg/mL, respectively. Also the CTEO had potential inhibitory effect on the cell viability of the tested pathogens at MIC concentration. The SEM analysis showed the inhibitory effect of CTEO as confirmed by considerable morphological alterations on the cell wall B. cereus ATCC 13061 and E. coli O157:H7 ATCC 43889. In addition, the CTEO revealed its mode of action on membrane integrity as confirmed by release of extracellular ATP, loss of 260-nm absorbing materials and leakage of potassium ions against food-borne pathogenic bacteria. These findings suggest that CTEO showed a broad-spectrum of antibacterial efficacy and compromise its mode of action on membrane integrity.
Recent studies proved that monoterpenoids could be an alternative to synthetic insecticides against stored-product pests. For that reason, it is necessary to learn the mode of action of these monoterpenoids. Inhibition of acetylcholinesterase (AChE) activity as a possible mode of action by 8 monoterpenoids which cause high mortality of three stored-product insect pests, Sitophilus oryzae L. (Coleoptera: Curculionidae), Rhyzopertha dominica Fabricius (Coleoptera: Bostrichidae) and Cryptolestes pusillus Schönherr (Coleoptera: Cucujidae) and the role of these monoterpenoids as inhibitors were examined. Inhibition of AChE was measured by colorimetric method where a chemical reaction with enzyme acetylcholinesterase, a substrate (acetylthiocoline iodide), the Ellman's reagent and each monoterpenoid as inhibitor was carried out. The majority of monoterpenoids tested inhibited the enzyme acetylcholinesterase; fenchone, S-carvone and linalool produced the highest inhibition. Furthermore, it was observed that fenchone, γ-terpinene, geraniol and linalool showed a reversible competitive inhibition at least at the enzyme's hydrophobic active site. S-carvone, estragole and camphor produced a mixed inhibition for this enzyme binding to either the free enzyme or the enzyme–substrate complex which links to a different site from the active site where the substrate binds. No inhibition of enzyme acetylcholinesterase by E-anethole was observed.
In spite of intensive research on plant natural products and insect-plant chemical interactions over the past three decades, only two new types of botanical insecticides have been commercialized with any success in the past 15 years, those based on neem seed extracts (azadirachtin), and those based on plant essential oils. Certain plant essential oils, obtained through steam distillation and rich in mono- and sesquiterpenes and related phenols, are widely used in the flavouring and fragrance industries and in aromatherapy. Some aromatic plants have traditionally been used for stored product protection, but the potential for development of pesticides from plant essential oils for use in a wide range of pest management applications has only recently been realized. Many plant essential oils and their major terpenoid constituents are neurotoxic to insects and mites and behaviourally active at sublethal concentrations. Most plant essential oils are complex mixtures. In our laboratory we have demonstrated that individual constituents of oils rarely account for a major share of the respective oil's toxicity. Further, our results suggest synergy among constituents, including among those that appear non-toxic in isolation. Repellent effects may be particularly useful in applications against public health and domestic pests, but may be useful in specific agricultural applications as well. In all of these applications, there is a premium on human and animal safety that takes priority over absolute efficacy. In agriculture, the main market niche for essential oil-based pesticides is in organic food production, at least in developed countries, where there are fewer competing pest management products. There is also scope for mixing these oils with conventional insecticides and for enhancing their efficacy with natural synergists. Some examples of field efficacy against agricultural pests are discussed.
The essential oil extracted from the seeds of dill (Anethum graveolens L.) was demonstrated in this study as a potential source of an eco-friendly antifungal agent. To elucidate the mechanism of the antifungal action further, the effect of the essential oil on the plasma membrane and mitochondria of Aspergillus flavus was investigated. The lesion in the plasma membrane was detected through flow cytometry and further verified through the inhibition of ergosterol synthesis. The essential oil caused morphological changes in the cells of A. flavus and a reduction in the ergosterol quantity. Moreover, mitochondrial membrane potential (MMP), acidification of external medium, and mitochondrial ATPase and dehydrogenase activities were detected. The reactive oxygen species (ROS) accumulation was also examined through fluorometric assay. Exposure to dill oil resulted in an elevation of MMP, and in the suppression of the glucose-induced decrease in external pH at 4 µl/ml. Decreased ATPase and dehydrogenase activities in A. flavus cells were also observed in a dose-dependent manner. The above dysfunctions of the mitochondria caused ROS accumulation in A. flavus. A reduction in cell viability was prevented through the addition of L-cysteine, which indicates that ROS is an important mediator of the antifungal action of dill oil. In summary, the antifungal activity of dill oil results from its ability to disrupt the permeability barrier of the plasma membrane and from the mitochondrial dysfunction-induced ROS accumulation in A. flavus.
Volatile compounds act as a language that plants use for their communication and interaction with the surrounding environment. To date, a total of 1700 volatile compounds have been isolated from more than 90 plant families. These volatiles, released from leaves, flowers, and fruits into the atmosphere and from roots into the soil, defend plants against herbivores and pathogens or provide a reproductive advantage by attracting pollinators and seed dispersers. Plant volatiles constitute about 1% of plant secondary metabolites and are mainly represented by terpenoids, phenylpropanoids/benzenoids, fatty acid derivatives, and amino acid derivatives. In this review we focus on the functions of plant volatiles, their biosynthesis and regulation, and the metabolic engineering of the volatile spectrum, which results in plant defense improvement and changes of scent and aroma properties of flowers and fruits.
In recent years, the use of essential oils (EOs) derived from aromatic plants as low-risk insecticides has increased considerably owing to their popularity with organic growers and environmentally conscious consumers. EOs are easily produced by steam distillation of plant material and contain many volatile, low-molecular-weight terpenes and phenolics. The major plant families from which EOs are extracted include Myrtaceae, Lauraceae, Lamiaceae, and Asteraceae. EOs have repellent, insecticidal, and growth-reducing effects on a variety of insects. They have been used effectively to control preharvest and postharvest phytophagous insects and as insect repellents for biting flies and for home and garden insects. The compounds exert their activities on insects through neurotoxic effects involving several mechanisms, notably through GABA, octopamine synapses, and the inhibition of acetylcholinesterase. With a few exceptions, their mammalian toxicity is low and environmental persistence is short. Registration has been the main bottleneck in putting new products on the market, but more EOs have been approved for use in the United States than elsewhere owing to reduced-risk processes for these materials.
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Volatile terpenoids released from different plant parts play crucial roles in pollinator attraction, plant defense, and interaction with the surrounding environment. Two distinct pathways localized in different subcellular compartments are responsible for the biosynthesis of these compounds. Recent advances in the characterization of genes and enzymes responsible for substrate and end product biosynthesis as well as efforts in metabolic engineering have revealed new aspects of volatile terpenoid biosynthesis. This review summarizes recent progress in the characterization of volatile terpenoid biosynthetic genes, their spatio-temporal expression patterns and subcellular localization of corresponding proteins. In addition, recent information obtained from metabolic engineering is discussed.
Currently, the use of synthetic chemicals to control insects and arthropods raises several concerns related to environment and human health. An alternative is to use natural products that possess good efficacy and are environmentally friendly. Among those chemicals, essential oils from plants belonging to several species have been extensively tested to assess their repellent properties as a valuable natural resource. The essential oils whose repellent activities have been demonstrated, as well as the importance of the synergistic effects among their components are the main focus of this review. Essential oils are volatile mixtures of hydrocarbons with a diversity of functional groups, and their repellent activity has been linked to the presence of monoterpenes and sesquiterpenes. However, in some cases, these chemicals can work synergistically, improving their effectiveness. In addition, the use of other natural products in the mixture, such as vanillin, could increase the protection time, potentiating the repellent effect of some essential oils. Among the plant families with promising essential oils used as repellents, Cymbopogon spp., Ocimum spp. and Eucalyptus spp. are the most cited. Individual compounds present in these mixtures with high repellent activity include alpha-pinene, limonene, citronellol, citronellal, camphor and thymol. Finally, although from an economical point of view synthetic chemicals are still more frequently used as repellents than essential oils, these natural products have the potential to provide efficient, and safer repellents for humans and the environment.
Bioactive oils are commonly used for their pharmaceutical, cosmetic and nutritional properties. Generally, these are volatile substances sensitive to oxygen, light, moisture, and heat. These reported special characteristics could diminish their applicability in the use of cosmetics, food and pharmaceutical industry. Thus, encapsulation is one of the most efficient methods for the formulation of bioactive oils and various investigations have been developed in this aspect. The encapsulation system is selected in line with the intended usage of the final formulation, which can vary depending on the size, shape or nature of selling components. In this review, we state an overview on the different systems for the encapsulation of bioactive oils, as well as, the elaboration methods currently utilized.
The seeking of new alternatives of synthetic insecticides for the safe environment and health has become an important issue of scientific research which may enable us to obtain safe foods. Although botanical insecticides (BIs) can never entirely replace the amounts of produced synthetic insecticides, they may significantly contribute to seeking the solution of problems associated with application of synthetic pesticides. Three most important arguments support the use of BIs: environmental safety, low or no toxicity for vertebrates and prevention of resistance development. The above-mentioned assets of BIs make us believe in the need of increasing the society-wide efforts leading to further expansion of practical use of these products. However, despite these assets, several limiting factors are associated with BIs that prevent their wider use or restrict their practical applications. This chapter is an effort to critically summarise the advantages and disadvantages of botanical insecticides including major factors that pose limitations to their practical use.
Context:
There is an increasing concern about chronic low-level pesticide exposure during childhood and its influence on childhood cancers.
Objective:
In this meta-analysis, we aimed to examine associations between residential childhood pesticide exposures and childhood cancers.
Data sources:
We searched all observational studies published in PubMed before February 2014 and reviewed reference sections of articles derived from searches.
Study selection:
The literature search yielded 277 studies that met inclusion criteria.
Data extraction:
Sixteen studies were included in the meta-analysis. We calculated effect sizes and 95% confidence intervals (CIs) by using a random effect model with inverse variance weights.
Results:
We found that childhood exposure to indoor but not outdoor residential insecticides was associated with a significant increase in risk of childhood leukemia (odds ratio [OR] = 1.47; 95% CI, 1.26-1.72; I(2) = 30%) and childhood lymphomas (OR = 1.43; 95% CI, 1.15-1.78; I(2) = 0%). A significant increase in risk of leukemia was also associated with herbicide exposure (OR = 1.26; 95% CI, 1.10-1.44; I(2) = 0%). Also observed was a positive but not statistically significant association between childhood home pesticide or herbicide exposure and childhood brain tumors.
Limitations:
The small number of studies included in the analysis represents a major limitation of the current analysis.
Conclusions:
Results from this meta-analysis indicated that children exposed to indoor insecticides would have a higher risk of childhood hematopoietic cancers. Additional research is needed to confirm the association between residential indoor pesticide exposures and childhood cancers. Meanwhile, preventive measures should be considered to reduce children's exposure to pesticides at home.
Botanical insecticides continue to be a subject of keen interest among the international research community, reflected in the steady growth of scientific publications devoted to the subject. Until very recently though, the translation of that theory to practice, i.e., the commercialization and adoption of new botanical insecticides in the marketplace, has seriously lagged behind. Strict regulatory regimes, long the bane of small pesticide producers, are beginning to relax some of the data requirements for "low risk" pesticide products, facilitating movement of more botanicals into the commercial arena. In this paper I discuss some of the jurisdictions where botanicals are increasingly finding favour, some of the newer botanical insecticides in the plant and animal health arsenal, and some of the specific sectors where botanicals are most likely to compete effectively with other types of insecticidal products.
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The efficacy of 30 aromatic compounds and their mutual binary combinations was assessed for acute toxicity against the larvae Culex quinquefasciatus. Based on comparison of the lethal doses, thymol and p-cymene were selected as the most effective (LD50 = 18 and 21 mg L(-1), respectively, and LD90 = 25 and 30 mg L(-1), respectively). Although the LD50 for terpinolene and trans-anethole was also estimated at 21 mg L(-1), their LD90 was significantly higher compared to the substances above (245 and 34 mg L(-1), respectively). In total, 435 binary combinations were tested, of which 249 combinations showed a significant synergistic effect, while 74 combinations showed a significant antagonistic effect on mortality. Only nine substances were identified as being able to create a synergistic effect with more than 20 substances: limonene, trans-anethole, 4-allylanisole, carvacrol, isoeugenol, menthone, carvone, borneol, and camphor. The highest synergistic effect on larval mortality was achieved for the combinations: eugenol and isoeugenol, carvone and carvacrol, carvone and 4-allylanisole, carvone and α-terpineol, carvone and menthone, limonene and trans-anethole, limonene and menthone, α-pinene and menthone, β-citronellol and menthone, carvacrol and 4-allylanisole, carvacrol and terpineol, α-terpinene and trans-anethole, camphor and menthone, camphene and menthone, and 4-allylanisole and menthone. Significant differences between achieved mortality and the mutual mixing ratio were found for the five selected binary mixtures that had shown the most significant synergistic effect in the previous tests. The mixture of limonene and trans-anethole showed the highest mortality, with the mixing ratio 1:1; the mixture of eugenol and isoeugenol caused 90.2 % mortality, with the mixing ratio 1:3. One hundred percent mortality was achieved if carvacrol was contained in a mixture with carvone in a ratio >2. After a comparison of all our results, based on our experiments, we can choose two pairs that caused mortality higher than 90 % in concentrations lower than 20 mg L(-1): limonene and trans-anethole (with the mixing ratio 1:1), and carvone and carvacrol (with the mixing ratio 1:2-3). The information gained can thus be used in the development of new botanical insecticides based on essential oils (EOs) and particularly in the creation of formulations.
Mosquitoes (Diptera: Culicidae) are a key threat for millions of people worldwide, since they act as vectors for devastating pathogens and parasites. In this scenario, vector control is crucial. Mosquito larvae are usually targeted using organophosphates, insect growth regulators, and microbial agents. Indoor residual spraying and insecticide-treated bed nets are also employed. However, these chemicals have negative effects on human health and the environment and induce resistance in a number of vectors. Newer and safer tools have been recently implemented to enhance control of mosquitoes. Here, I focus on some crucial challenges about eco-friendly control of mosquito vectors, mainly the improvement of behavior-based control strategies (sterile insect technique ("SIT") and "boosted SIT") and plant-borne mosquitocidals, including green-synthesized nanoparticles. A number of hot areas that need further research and cooperation among parasitologists, entomologists, and behavioral ecologists are highlighted.
Essential oils (EOs) and their main constituent compounds have been extensively investigated due to their application in the food industry for improving the shelf life of perishable products. Although they are still not available for use in food packaging in the market in Europe, considerable research in this field has been carried out recently. The safety of these EOs should be guaranteed before being commercialized. The aim of this work was to review the scientific publications, with a primary focus on the last 10 years, with respect to different in vitro toxicological aspects, mainly focussed on mutagenicity/genotoxicity. In general, fewer genotoxic studies have been reported on EOs in comparison to their main components, and most of them did not show mutagenic activity. However, more studies are needed in this field since the guidelines of the European Food Safety Authority have not always being followed accurately. The mutagenic/genotoxic activities of these substances have been related to metabolic activation. Therefore, in vivo tests are required to confirm the absence of genotoxic effects. Considering the great variability of the EOs and their main compounds, a case-by-case evaluation is needed to assure their safe use in food packaging.
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Plant essential oils are usually complex mixtures, and many factors can affect their chemical composition. To identify relationships between composition and bioactivity of the constituents, comparative and synergistic interactions of the major constituents of rosemary essential oil were evaluated against third instar larvae and an ovarian cell line of the cabbage looper, Trichoplusia ni via different methods of application.
The major constituents of the rosemary oil we used were 1,8-cineole, (±)-camphor, (+)-α-pinene and camphene. Via topical application to larvae, 1,8-cineole was identified as the major active compound, whereas via fumigation, 1,8-cineole and (±)-camphor, and in a cytotoxicity assay, (+)-α-pinene, were determined to be the major active principles. Several combinations of these constituents exhibited synergistic insecticidal activities when topically applied, particularly among combinations of three major constituents, (±)-camphor, (+)-α-pinene, and camphene. A binary mixture of 1,8-cineole and (±)-camphor showed enhanced activity, with a synergy ratio of 1.72.
Based on our results, the insecticidal activity of rosemary oil appears to be a consequence of the synergistic interaction between 1,8-cineole and (±)-camphor, and (±)-camphor should be considered a promising synergizing agent.
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Background
Plant extracts and by-products furnish various alternative products for crop protection and are traditionally used by farmers. But the cost and timeframe for their registration as active substances are prohibitive for small companies and farmers’ associations with the new Plant Protection Products (PPP) Regulation (EC) No 1107/2009. However, there is now a possibility to register light compounds as “Basic Substances”, a new category described in article 23 and in the “whereas/ recital (18)”.ResultsWe developed a regulatory expertise on the approval of such products in the framework of the PPP regulation. A Draft Assessment Report in one volume was established, later transformed by EC Directorate into a Basic Substance Application Template, and subsequently used by the EC as a matrix for the corresponding Guidelines for applicants (SANCO 10363/2012 rev. 9). Here we provide further tools, consisting in methodological, linguistic and strategic recommendations in order to constitute a Basic Substance Application (BSA) and proceed to its registration.Conclusion
While the use of alternative agents for crop protection is increasing both in organic and conventional agriculture, these usages are still considered as “minor uses”. Our approach and tools are valuable to non-PPP specialized applicants for simplifying and facilitating their submission of the BSA.
Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture.
However, the prophylactic use of broad‐spectrum pesticides goes against the long‐established principles of integrated pest management ( IPM ), leading to environmental concerns.
It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC 50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees.
Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals.
Synthesis and applications . Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non‐target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.
Microencapsulation by spray-drying is widely used in the preparation of flavors in the food industry. This study sought to evaluate the influence of oil load and wall material ratios on the properties of rosemary essential oil microencapsulated by spray-drying, using maltodextrin and modified starch as carriers. Increasing the oil load of the emulsion, the obtained particles presented higher moisture content, lower hygroscopicity and higher total oil content. The increased wall material content lengthened the wettability time. This research further suggested that the optimal wall concentration and oil load conditions are 20.9% and 29.4%, respectively. The encapsulated oil composition proved to be quite similar to pure oil. The mean particle size was 12.2 μm and the analysis of the particles revealed surfaces with some depressions, however without fissures.
In our paper, we have tested 12 simple of phenols and 9 phenolic acids for acute toxicity and feeding inhibition on Spodoptera littoralis larvae. It was found that while the phenolic acids showed little or no effect on acute toxicity, all the tested simple phenols caused larval mortality within 24 hours upon application. Lethal doses were successfully estimated for 11 substances using probit analysis. Thymol and carvacrol showed the highest efficiency, for LD50 were estimated as 20 and 27 μg/larvae, respectively. The tested phenols also showed significantly higher feeding inhibition than phenolic acids. The most significant antifeedant effect was exerted by thymol, where LD50 and LD90 were estimated as 6 and 9 μg/cm2, respectively.
Insecticidal activity of thyme oil was screened against the housefly (M. domestica) under laboratory conditions. The aim of this study was to research the toxic effects of the thyme oil on House fly larvae and adults and the effects of the thyme oil sublethal doses on vitality and fecundity adults and on the F1 generation vitality. In comparison with the female and larvae, the male flies were more sensitive in the contact application. The application of sublethal doses to the adults of the housefly has significantly decreased the longevity of both sexes. Generally, it was determined that the natural mortality of 50% of the treated adults occurs on the 5th - 7th day, to the contrary of 18th -19th day on which occurs the natural mortality of the non-treated adults. The natality was decreased by 76%-81%, in comparison to the control test in which either sex or, female flies only, were treated with the test agent. Thereby, the most significant mortality (more than 80%) was seen with larvae which emerged from eggs which were laid by the treated female flies. These larvae were non-vital, their pupae were significantly smaller and the survived pupae had a much higher mortality.
In recent years, consumers have developed an ever-increasing interest in natural products as alternatives for artificial additives or pharmacologically relevant agents. Among them, essential oils have gained great popularity in the food, cosmetic, as well as the pharmaceutical industries. Constituting an array of many lipophilic and highly volatile components derived from a great range of different chemical classes, essential oils are known to be susceptible to conversion and degradation reactions. Oxidative and polymerization processes may result in a loss of quality and pharmacological properties. Despite their relevance for consumers, there is a paucity of information available addressing this issue. Therefore, the present review provides a comprehensive summary on possible changes in essential oils and factors affecting their stability. Focusing on individual essential oils, the various paths of degradation upon exposure to extrinsic parameters are outlined. Especially temperature, light, and oxygen availability are recognized to have a crucial impact on essential oil integrity. Finally, analytical methods to assess both genuine as well as altered essential oil profiles are evaluated with respect to their suitability to track chemical alterations. It is believed that only a careful inspection of essential oils by a set of convenient methods allows profound quality assessment that is relevant to producers and consumers alike.
Our analysis of >20000 papers on botanical insecticides from 1980 to 2012, indicates major growth in the number of papers published annually (61 in 1980 to 1207 in 2012), and their proportion among all papers on insecticides (1.43% in 1980 to 21.38% in 2012). However, only one-third of 197 random articles among the 1086 papers on botanical insecticides published in 2011 included any chemical data or characterization; and only a quarter of them included positive controls. Therefore, a substantial portion of recently published studies has design flaws that limit reproducibility and comparisons with other and/or future studies. In our opinion, much of the scientific literature on this subject is of limited use in the progress toward commercialization or advancement of knowledge, given the resources expended.
In the present study, the complexation between volatile flavor compounds and cyclodextrins (CDs) was investigated by static headspace gas chromatography (SH-GC). We focused on the complexation behavior of α-CD, β-CD, γ-CD, hydroxypropyl-β-cyclodextrin (HPBCD), randomly methylated-β-cyclodextrin (RAMEB), and of a low methylated-β-cyclodextrin (CRYSMEB) for 13 volatile flavor compounds (α-pinene, β-pinene, camphene, eucalyptol, limonene, linalool, p-cymene, myrcene, menthone, menthol, trans-anethole, pulegone and camphor). The obtained results indicated the formation of a 1:1 inclusion complex for all the studied compounds. α-CD and γ-CD gave generally lower stability constants than β-CDs. Moreover, the complexation efficiency of native β-CD is close to the modified β-CDs (HPBCD, RAMEB and CRYSMEB).