Eco-friendly Control Tools Research Articles

High-energy emulsification of Allium sativum essential oil boosts insecticidal activity against Planococcus citri with no risk to honeybees

AbstractThe ecotoxicological consequences of synthetic pesticides have encouraged stakeholders to search for eco-friendly pest control tools, like essential oils (EOs). Nano-delivery systems (nanoparticles and nano-emulsions) seem ideal for developing EO-based biopesticides, although production processes should be standardized and implemented. In this study, nano-emulsions loaded with a high amount of Allium sativum L. EO (15%) were developed using different mixed bottom-up/top-down processes. Garlic EO was chemically analyzed by gas chromatography-mass spectrometry (GC-MS) and formulations were physically characterized using Dynamic Light Scattering (DLS) apparatus. The insecticidal activity against Planococcus citri Risso (Hemiptera: Pseudococcidae) and selectivity toward Apis mellifera L. (Hymenoptera: Apidae) worker bees was evaluated. Garlic EO was mainly composed of sulphur components (96.3%), with diallyl disulphide and diallyl trisulphide as the most abundant compounds (37.26% and 28.15%, respectively). Top-down processes could produce stable nano-emulsions with droplet size in the nanometric range (< 200nm) and good polydispersity index (PDI < 0.2). In contrast, the bottom-up emulsion was unstable, and its droplet size was around 500nm after 24 hours. High-energy emulsification processes significantly increased the residual toxicity of garlic EO against 3rd instar P. citri nymphs, whereas the developed formulations were harmless to A. mellifera workers in topical application. This study confirmed that the production process significantly affected the physical properties and efficacy against target pests. The lack of adverse impact on honeybees denotated the potential of these formulations as bioinsecticides in organic and/or IPM programs, although further extended ecotoxicological studies are necessary.

Bioefficacy of the ethanolic crude extract of the wild leek, Allium ampeloprasum L. (Amaryllidaceae), against the third and fourth larval stages of Aedes aegypti L. (Culicidae)

Insecticide resistance is a threat to vector control worldwide. In the Philippines, dengue burden remains significant, thus prioritizing the need to develop eco-friendly control strategies and tools against mosquito vectors. Various Allium species have been found to possess larvicidal activity against dengue-carrying mosquitoes. In this study, the larvicidal activity of the crude extract of Allium ampeloprasum L. (Asparagales: Amaryllidaceae) was studied in concentrations ranging from 1 to 10,000 mg/L against the third (L3) and fourth (L4) larval instars of Aedes aegypti L. Larval mortality at 48 h were subjected to probit analysis and Kruskal-Wallis H test to estimate lethal concentrations and to determine significant means among the groups, respectively. Results show that the crude extract of A. ampeloprasum L. demonstrated larvicidal activity against the L3 and L4 Ae. aegypti L. Concentrations corresponding to 50% mortality (Lethal Concentration 50 [LC50]) among L3 and L4 larvae were estimated at 2,829.16 and 13,014.06 mg/L, respectively. Moreover, 90% mortality (LC90) in the L3 and L4 larvae were estimated at 9,749.75 and 57,836.58 mg/L, respectively. Only 1,000 and 10,000 mg/L for L3, and the 10,000 mg/L for L4, had comparable larvicidal action to the commercial larvicide used as a positive control. The results support the presence of bioactive compounds with larvicidal properties, thus suggesting A. ampeloprasum L. as a potential source of active ingredients for the development of a plant-based larvicide.

Cupressus sempervirens Essential Oil, Nanoemulsion, and Major Terpenes as Sustainable Green Pesticides against the Rice Weevil

In order to find effective, biorational, and eco-friendly pest control tools, Cupressus sempervirens var. horizontalis essential oil (EO) was produced using hydrodistillation, before being analyzed with gas chromatography, specifically, using flame ionization detection. The monoterpene components α-pinene (46.3%), δ-3-carene (22.7%), and α-cedrol, a sesquiterpene hydrocarbon, (5.8%), were the main fractions. An oil-in-water nanoemulsion was obtained following a green protocol. The EO, its nanoemulsion, and its terpenes each exhibited both insecticidal and insect repellent activities against the rice weevil, Sitophilus oryzae. In a contact bioassay, the nanoemulsion induced a 100% adult mortality rate in a concentration of 10.0 µL/cm2 after 4 days of treatment, whereas 40 µL/cm2 of EO and α-cedrol was required to kill 100% of weevils. Using fumigation, nanoemulsion and EO at 10 µL/L air caused a 100% adult mortality rate after 4 days of treatment. The LC50 values of botanicals ranged between 5.8 and 53.4 µL/cm2 for contact, and between 4.1 and 19.6 µL/L for fumigation. The phytochemicals strongly repelled the weevil at concentrations between 0.11 and 0.88 µL/cm2, as well as considerably inhibiting AChE bioactivity. They were found to be safe for earthworms (Eisenia fetida) at 200 mg/kg, which also caused no significant alteration in wheat grain viability. This study provides evidence for the potential of using the EO of C. sempervirens and its nanoemulsion as natural, eco-friendly grain protectants against S. oryzae.

Genetic Diversity of Irradiated Galleria mellonella with Sub Sterile and Sterile Doses Assessed by Scot

Using the sterile male technique as an eco-friendly pest control tool has been confirmed in many countries. Therefore, this study was targeted to investigate the genetic divergence of the irradiated wax moth using PCR technique “start codon targeted polymorphism” and draw a phylogenetic tree to find the molecular deviation, which affords a theoretical basis for the efficiency of irradiation as a successful control strategy. This was achieved by exposing the pupae to gamma-ray doses (100; sub sterile and 260Gy; sterile). Exposure of the pupae to radiation caused the presence of new extra bands and the loss of others in SCoT analysis of the emerged adults. A dendrogram was constructed based on the similarity index. It was concluded that the irradiated group with sterile dose was more genetically different than both the control ones and the irradiated group with the sub sterile dose. Conclusions: using SCoT technique could be recommended for differentiation between irradiated and unirradiated moths.

Synthesize palladium nanoparticles from the macroalgae Sargassum fusiforme: An eco-friendly tool in the fight against Plasmodium falciparum?

Although numerous drugs are practiced to control malaria and its vectors, more recently, eco-friendly control tools have been proposed to battle its etiologic agents. Thus, using green bionanotechnology approaches, we aimed to synthesize palladium nanoparticles (Pd NPs) from the macroalgae Sargassum fusiforme (Sf), its potential antiparasitic activity against P. falciparum, as well as its possible cytotoxicity, in HeLa cells. After the biosynthesis of the PdSf NPs, their characterization was carried out by UV–Vis, FESEM, and EDX analyses, and their hydrodynamic size, zeta potential, and surface area were determined. Furthermore, the functional groups of the PdSf NPs were analyzed by FT-IR and GC–MS. While PdSf NPs had an IC50 of 7.68 μg/mL (Chloroquine (CQ)-s) and 16.42 μg/mL, S. fusiforme extract had an IC50 of 14.38 μg/mL (CQ-s) and 35.27 μg/mL (CQ-r). With an IC50 value of 94.49 μg/mL, PdSf NPs exhibited the least toxic effect on the HeLa cells. The Lipinski rule of five and ADMET prediction were used to assess the in silico models of caffeine acid hexoside and quercetin 7-O-hexoside for the presence of drug-like properties. Pathogenic proteins, primarily responsible for motility, binding, and disease-causing, were the target of the structurally based docking studies between plant-derived compounds and pathogenic proteins. Thus, our study pioneered promising results that support the potential antiplasmodial activity of eco-friendly synthesized PdSf NPs using S. fusiforme extract against P. falciparum, opening perspectives for further exploration into the use of these NPs in malaria therapy.

Efficacy of native cyclopoid copepods in biological vector control with regard to their predatory behavior against the Asian tiger mosquito, Aedes albopictus

BackgroundThe control of the Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) is crucial owing to its high vector competence for more than 20 arboviruses—the most important being dengue, chikungunya and Zika virus. Aedes albopictus has an enormous adaptive potential, and its invasive spreading across urban and suburban environments poses challenges for its control. Therefore, all suitable, cost-effective and eco-friendly control tools should be put into practice. In this context, cyclopoid copepods are already known as effective predators of mosquito larvae. This study reports an essential preliminary step towards the integration of copepods into the vector control strategy in Germany, in order to provide a sustainable tool in an integrated control strategy based on the elimination or sanitation of breeding sites, the use of formulations based on Bacillus thuringiensis israelensis (Bti.) and the sterile insect technique (SIT).MethodsThe predatory potential of native cyclopoid copepods, namely the field-derived species Megacyclops viridis (Crustacea: Cyclopidae), was examined against the larvae of Ae. albopictus, and for comparison, against the larvae of the common house mosquito, Culex pipiens sensu lato (Diptera: Culicidae). The use of different larval instars as prey, and various predator-to-prey ratios, were examined under laboratory and semi-field conditions. The compatibility of Bti. applications along with the use of copepods was assessed in the laboratory.ResultsHigh predation efficiency of M. viridis upon first-instar larvae of Ae. albopictus was observed under laboratory (up to 96%) and semi-field conditions (65.7%). The copepods did not prey upon stages further developed than the first instars, and in comparison with Ae. albopictus, the predation rates on the larvae of Cx. pipiens s.l. were significantly lower.ConclusionsThe results indicate a high predation potential of M. viridis against Ae. albopictus larvae, even though strong larval stage and mosquito species preferences were implicated. The integration of copepods as a promising biocontrol agent to the vector control strategy in Germany is therefore highly recommended, especially because of the excellent compatibility of copepods with the use of Bti. However, further research is required, concerning all the probable parameters that may impact the copepod performance under natural conditions.Graphical

Mating Disruption for Managing the Honeydew Moth, Cryptoblabes gnidiella (Millière), in Mediterranean Vineyards.

Simple SummaryCryptoblabes gnidiella has recently become one of the most feared pests in the Mediterranean grape-growing areas. Its expanding impact requires the development of effective strategies for its management. Since insecticide strategy has shown several weaknesses, we developed a pheromone-based mating disruption (MD) approach as a possible sustainable control technique for this pest. Between 2016 and 2019, field trials were carried out in two study sites in central and southern Italy, using experimental pheromone dispensers. The number of adult captures in pheromone-baited traps and the percentage of infestation recorded on ripening grapes were compared among plots treated with MD dispensers, insecticide-treated (no MD) plots, and untreated plots. Results highlighted that the application of MD may contribute to lowering the damage significantly. However, further studies aimed at clarifying the still little-known aspects of the biology and population dynamics of the honeydew moth are needed.The demand for a reduced use of pesticides in agriculture requires the development of specific strategies for managing arthropod pests. Among eco-friendly pest control tools, pheromone-based mating disruption (MD) is promising for controlling several key insect pests of economic importance, including many lepidopteran species. In our study, we evaluated an MD approach for managing the honeydew moth (HM), Cryptoblabes gnidiella, an emerging threat for the grapevine in the Mediterranean basin. The trials were carried out in two study sites, located in Tuscany (central Italy, years 2017–2019) and Apulia (southern Italy, years 2016 and 2018–2019), and by applying MD dispensers only in April, in April and July, and only in July. To evaluate the effects of MD, infested bunches (%), damaged area (%) per bunch, and number of living larvae per bunch were compared among plots covered with MD dispensers, insecticide-treated plots (Apulia only), and untreated control plots. Male flights were monitored using pheromone-baited sticky traps. Except for the sampling carried out in Tuscany in 2018, where HM infestation level was very low, a significant difference was recorded between MD and control plots, both in terms of HM damage caused to ripening grapes and/or number of living larvae per bunch. Overall, our study highlighted that MD, irrespective of the application timing, significantly reduced HM damage; the levels of control achieved here were similar to those obtained with the application of insecticides (no MD). However, MD used as stand-alone strategy was not able to provide complete pest control, which may instead be pursued by growers with an IPM approach.

Enhancing malaria control using Lagenaria siceraria and its mediated zinc oxide nanoparticles against the vector Anopheles stephensi and its parasite Plasmodium falciparum

In many developing countries, there are certain health problems faced by the public, one among them is Malaria. This tropical disease is mainly caused by Plasmodium falciparum. It is categorized as a disaster to public health, which increases both mortality and morbidity. Numerous drugs are in practice to control this disease and their vectors. Eco-friendly control tools are required to battle against vector of this significant disease. Nanotechnology plays a major role in fighting against malaria. The present paper synthesized Zinc oxide nanoparticles (ZnO NPs) using zinc nitrate via simple green routes with the help of aqueous peel extract of Lagenaria siceraria (L. siceraria). The synthesized ZnO NPs were characterized by various biophysical methods. Moreover, the extract of L. siceraria and their mediated ZnO NPs was experimented against III instar larvae of An. stephensi. The impact of the treatment based on ZnO NPs concerning histology and morphology of mosquito larval was further observed. In the normal laboratory environment, the efficiency of predation of Poeciliareticulata (P. reticulata) against An. Stephensi larvae was found to be 44%, whereas in aqueous L. siceraria extract and its mediated ZnO NPs contaminated environment, P. reticulate showed predation efficiency of about 45.8% and 61.13% against An. Stephensi larva. L. siceraria synthesized ZnO NPs were examined against the Plasmodium falciparum CQ-sensitive strains. The L. siceraria extract and its mediated ZnO NPs showed the cytotoxic effects against HeLa cell lines with an IC50 value of 62.5 µg/mL. This study concludes that L. siceraria peel extract and L. siceraria synthesized ZnO NPs represent a valuable green option to fight against malarial vectors and parasites.

Phytochemical analysis and fabrication of silver nanoparticles using Acacia catechu: An efficacious and ecofriendly control tool against selected polyphagous insect pests.

Globally, the farmers are struggling with polyphagous insect pest, and it is the number one enemy of agri-products, which made plenty of economic deterioration. Spodoptera litura and Helicoverpa armigera are the agronomically important polyphagous pests. Most of the farmers are predominately dependent on synthetic chemical insecticides (SCIs) for battle against polyphagous pets. As a result, the broad spectrum usage of SCIs led a lot of detrimental outcomes only inconsequently the researchers search the former-friendly phyto-pesticidal approach. In the present investigation, leaf ethanol extract (LEE) and silver nanoparticles (AgNPs) of A. catechu (Ac) were subjected to various spectral (TLC, CC, UV, FTIR, XRD and SEM) analyses. Larval and pupal toxicity of A. catechu Ac-LEE and Ac-AgNPs were tested against selected polyphagous insect pests. The significant larval and pupal toxicity were experimentally proven, and the highest toxicity noticed in AgNPs than Ac-LEE. The larval and pupal toxicity of Ac-AgNPs tested against S. litura and H. armigera LC50/LC90 values were 71.04/ 74.78, 85.33/ 88.91 µg/mL and 92.57/ 96.21 and 124.43/ 129.95 µg/mL respectively. Ac-AgNPs could be potential phyto-pesticidal effectiveness against selected polyphagous insect pests. In globally, it is significantly sufficient ratification giving towards the prevention of many unauthorized SCPs.

Larvicidal potential of some plant extracts against Anopheles arabiensis Patton (Diptera: Culicidae)

Insecticide based vector control intervention is threatening with the emergence and spread of resistant vectors. The development of other eco-friendly and cost effective vector control tools is required to alleviate this problem. In this study, five selected plant leaf extracts were evaluated for their larvicidal activities against 3rd instar An. arabiensis larvae at concentrations ranging from 50 to 300 ppm following the WHO protocol. The best performing extract was subjected to bioassay-guided column chromatographic fractionation and all fractions were tested separately for their larvicidal activities. All the plant extracts were found to have potential larvicidal activities against 3rd instar An. arabiensis larvae. Methanol crude extract of Calpurnia aurea achieved 100% larval mortality at 300 ppm with LC50 of 84.85 ppm while less activity was observed for methanol crude extract of Artemisia annua, 68% larval mortality at 300 ppm. Column chromatographic fractions F1and F3 of methanol extract of C. aurea caused 100% mortality at 250 and 300 ppm with LC50 of 62.51 and 82.33 ppm, respectively. The present study revealed that column chromatographic fractions F1 and F3 of methanol extract of C. aurea caused a remarkable larvicidal activity against An. arabiensis demonstrating a high potential for botanical mosquito insecticide development.

Lagenaria siceraria - synthesised ZnO NPs - a valuable green route to control the malaria vector Anopheles stephensi.

Malaria is a dangerous disease affecting humans and animals in tropical and subtropical areas worldwide. According to recent estimates, 3.2 billion people are at risk of malaria. Many drugs are in practices to control this disease and their vectors. Eco-friendly control tools are needed to fight vectors of this important disease. Nanotechnology is playing a key role in the fight against many public health emergencies. In the present study, Lagenaria siceraria aqueous peel extract was used to prepare zinc oxide nanoparticles (ZnO NPs), then tested on Anopheles stephensi eggs, larvae and pupae. The L. siceraria-synthesised ZnO NPs were characterized additionally by FTIR, AFM, XRD, UV-Vis spectroscopy, EDX, and SEM spectroscopy The ovicidal, larvicidal, pupicidal and repellent activities of L. siceraria and green-synthesised ZnO NPs were analysed on A. stephensi. The potential mechanism of action of ZnO NPs was studied investigating the changes in various enzyme activities in A. stephensi IV instar larvae. Furthermore, the smoke toxicity of L. siceraria-based cones against A. stephensi evoked higher mortality if compared with the control. Overall, the present study concluded that L. siceraria peel extract and its mediated green synthesised ZnO NPs represent a valuable green option to manage against malaria vectors.

Polymer nanoparticles containing essential oils: new options for mosquito control.

Mosquitoes (Diptera: Culicidae) are vectors of important parasites and pathogens causing death, poverty and social disability worldwide. The overuse of synthetic insecticides to control mosquito vectors lead to resistance, adverse environmental effects and high operational costs. Therefore, the development of eco-friendly control tools is an important public health challenge. In this study, two different essential oils (EO) (geranium, Geranium maculatum, and bergamot, Citrus bergamia) loaded polymeric nanoparticle (PN) were elaborated using polyethylene glycol (PEG) and chitosan (Qx) as the polymeric matrix/coating. In addition, the mosquito larvicidal acute and residual activity of the PN was evaluated on Culex pipiens pipiens. The physicochemical characterization of PN revealed that PEG-PN had sizes <255nm and encapsulation efficiency between 68 and 77%; Qx-PN showed sizes <535nm and encapsulation efficiency between 22 and 38%. From the toxicological test, it was observed that Qx-PN produced higher acute and residual activity than PEG-PN. Overall, this study highlights that polymer nanoparticles containing essential oil are a promising source of eco-friendly mosquito larvicidal products.

Larvicidal and repellent activity of the essential oil from Atalantia monophylla on three mosquito vectors of public health importance, with limited impact on non-target zebra fish

The development of eco-friendly mosquito control tools is of key importance for public health worldwide. In the present study, the essential oil [EO] from Atalantia monophylla essential oil was tested for larvicidal and repellent activity against three species of mosquitoes, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The EO showed acute toxicity against 2nd and 4th instar larvae of the tested mosquitoes, Notably, LC50 ranged from 7 to 16 ppm. EO tested as repellent at 50 ppm protected for 336–366 min against three mosquito species. Different concentrations of EO showed mortality in zebrafish (Danio rerio) and the LC50 value was 69.59 ppm. The EO did not show any allergic reaction on tested volunteers upto 50 ppm. While pure EO was tested slight itching was observed on the 2nd and 3rd volunteer. GC-MS analysis of A. monophylla EO showed the presence of 40 phytochemicals in different ratios, among them eugenol, sabinene, 1,2-dimethoxy-4-(2-methoxyethenyl)benzene and beta-asarone are major compounds. Overall, the EO showed high larvicidal and repellent activity against three mosquito vectors with limited impact on non-target zebrafish. Therefore, EO from A. monophylla could be a valuable source for the development of mosquito repellents and larvicides.

Larvicidal activity of Blumea eriantha essential oil and its components against six mosquito species, including Zika virus vectors: the promising potential of (4E,6Z)-allo-ocimene, carvotanacetone and dodecyl acetate

The effective and environmentally sustainable control of mosquitoes is a challenge of essential importance. This is due to the fact that some invasive mosquitoes, with special reference to the Aedes genus, are particularly difficult to control, due to their high ecological plasticity. Moreover, the indiscriminate overuse of synthetic insecticides resulted in undesirable effects on human health and non-target organisms, as well as resistance development in targeted vectors. Here, the leaf essential oil (EO) extracted from a scarcely studied plant of ethno-medicinal interest, Blumea eriantha (Asteraceae), was tested on the larvae of six mosquitoes, including Zika virus vectors. The B. eriantha EO was analyzed by GC and GC-MS. The B. eriantha EO showed high toxicity against 3rd instar larvae of six important mosquito species: Anopheles stephensi (LC50=41.61 μg/ml), Aedes aegypti (LC50=44.82 μg/ml), Culex quinquefasciatus (LC50 =48.92 μg/ml), Anopheles subpictus (LC50=51.21 μg/ml), Ae. albopictus (LC50=56.33 μg/ml) and Culex tritaeniorhynchus (LC50=61.33 μg/ml). The major components found in B. eriantha EO were (4E,6Z)-allo-ocimene (12.8%), carvotanacetone (10.6%), and dodecyl acetate (8.9%). Interestingly, two of the main EO components, (4E,6Z)-allo-ocimene and carvotanacetone, achieved LC50 lower than 10 μg/ml on all tested mosquito species. The acute toxicity of B. eriantha EO and its major constituents on four aquatic predators of mosquito larval instars was limited, with LC50 ranging from 519 to 11.431 μg/ml. Overall, the larvicidal activity of (4E,6Z)-allo-ocimene and carvotanacetone far exceed most of the LC50 calculated in current literature on mosquito botanical larvicides, allowing us to propose both of them as potentially alternatives for developing eco-friendly mosquito control tools.

One-pot and eco-friendly synthesis of silver nanocrystals using Adiantum raddianum: Toxicity against mosquito vectors of medical and veterinary importance

Mosquitoes (Diptera: Culicidae) represent a key threat for millions of humans and animals worldwide, since they act as vectors for devastating parasites and pathogens. Eco-friendly control tools are a priority. Plant-mediated biosynthesis of nanoparticles is rapid and cost-effective. Here we biosynthesized poly-dispersed silver nanocrystals (AgNPs) using a cheap aqueous leaf extract of Adiantum raddianum. AgNPs were characterized by UV–vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX) and X-ray diffraction analysis (XRD). The acute toxicity of A. raddianum extract and biosynthesized AgNPs was evaluated against larvae of the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. Compared to the leaf aqueous extract, AgNPs showed higher toxicity against An. stephensi, Ae. aegypti and Cx. quinquefasciatus with LC50 values of 10.33, 11.23 and 12.19μg/ml, respectively. Biosynthesized AgNPs were found safer to non-target organisms Diplonychus indicus, Anisops bouvieri and Gambusia affinis, with respective LC50 values ranging from 517.86 to 635.98μg/ml. Overall, this study firstly shed light on the potential of A. raddianum as a potential bio-resource for rapid, cheap and effective nanosynthesis of novel mosquitocides.

Green-Synthesized Mosquito Oviposition Attractants and Ovicides: Towards a Nanoparticle-Based “Lure and Kill” Approach?

Mosquitoes are key vectors of malaria, dengue, yellow fever, chikungunya, West Nile, Japanese encephalitis, lymphatic filariasis, Zika virus and St. Louis encephalitis virus. Eco-friendly control tools of Culicidae vectors are a priority. Green nanotechnologies may help to boost the effectiveness of mosquito vector control. We proposed a facile fabrication of poly-disperse and stable silver nanoparticles (AgNPs) using the Aganosma cymosa leaf extract. Nanoparticles were characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Nanoparticles showed high toxicity on eggs and larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. LC50 values were 12.45, 13.58 and 14.79 μg/mL, respectively. No egg hatchability was noted post-treatment with 40, 50 and 60 μg/mL, respectively. Nanoparticles were found safer to non-target mosquito predators Anisops bouvieri, Diplonychus indicus and Gambusia affinis, LC50 values ranged from 673.36 to 2247.43 µg/mL. Notably, AgNPs showed high oviposition attractiveness towards the three mosquito species. Overall, the oviposition attractiveness of the A. cymosa extract coupled with the ovicidal action of AgNPs can help to develop “lure and kill” tools to be used at mosquito breeding sites.

Neem-Borne Molecules as Eco-Friendly Control Tools Against Mosquito Vectors of Economic Importance

Neem-Borne Molecules as Eco-Friendly Control Tools Against Mosquito Vectors of Economic Importance

One pot synthesis of silver nanocrystals using the seaweed Gracilaria edulis: biophysical characterization and potential against the filariasis vector Culex quinquefasciatus and the midge Chironomus circumdatus

Mosquitoes (Diptera: Culicidae) represent a deadly threat for millions of humans and animals worldwide. Seaweeds are an important resource for marine biotechnology and are currently investigated as sources of reducing and capping agents for the nanosynthesis of mosquitocides. Culex quinquefasciatus is a major vector of lymphatic filariasis, while chironomid midges (Diptera: Chironomidae) elicit allergic reactions. In this research, silver nanoparticles (AgNP) were biosynthesized using a cheap aqueous extract of Gracilaria edulis as reducing and stabilizing agent. The formation of AgNP was confirmed by UV–Vis spectrophotometry. AgNP were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray analysis. AgNP were mostly spherical and cubic in shape, crystalline in nature. Gracilaria edulis-synthesized AgNP showed excellent ovicidal, larvicidal, pupicidal, and ovideterrent toxicity against Cx. quinquefasciatus and Chironomus circumdatus. Larvicidal LC50 ranged from 17 to 29 ppm. AgNP of 30 ppm led to 100 % mortality in treated eggs. Doses higher than 10 ppm lead to oviposition deterrence rates higher than 75 % (Oviposition Activity Index lower than −0.59). In the field, a single application of AgNP (10 × LC50) led to elimination of larval populations of Cx. quinquefasciatus and Ch. circumdatus within 72 h. Overall, G. edulis-synthesized AgNP may be potential candidates to develop eco-friendly control tools against Diptera of medical and veterinary importance.

Fern-synthesized silver nanocrystals: Towards a new class of mosquito oviposition deterrents?

Mosquitoes act as vectors of devastating pathogens and parasites, representing a key threat for millions of humans and animals worldwide. Eco-friendly control tools are urgently required. We proposed a novel method of fern-mediated biosynthesis of silver nanoparticles (AgNP) using Dicranopteris linearis, acting as a reducing and capping agent. AgNP were characterized by UV–vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), zeta potential and particle size analysis. In mosquitocidal assays, the LC50 of D. linearis extract against Aedes aegypti ranged from 165.213 (larva I) to 255.055ppm (pupa). LC50 of D. linearis-synthesized AgNP ranged from 18.905 (larva I) to 29.328ppm (pupa). In the field, the application of D. linearis extract and AgNP (10×LC50) led to 100% larval reduction after 72h. Smoke toxicity experiments conducted against A. aegypti adults showed that D. linearis leaf-, stem- and root-based coils evoked mortality rates comparable to the permethrin-based positive control (58%, 47%, 34%, and 48% respectively). In ovicidal experiments, egg hatchability was reduced by 100% after treatment with 25ppm of AgNP and 300ppm of D. linearis extract. Interestingly, oviposition deterrent assays highlighted that 100ppm of fern extract reduced oviposition rates of more than 65%, while 10ppm of fern-fabricated AgNP reduced oviposition rates of more than 70% in A. aegypti (OAI were −0.52 and −0.55, respectively). Overall, our results highlighted that D. linearis-synthesized AgNP could be useful candidates to develop nano-formulated oviposition deterrents effective against dengue vectors.

Single-step biosynthesis and characterization of silver nanoparticles using Zornia diphylla leaves: A potent eco-friendly tool against malaria and arbovirus vectors

Mosquitoes (Diptera: Culicidae) are vectors of important pathogens and parasites, including malaria, dengue, chikungunya, Japanese encephalitis, lymphatic filariasis and Zika virus. The application of synthetic insecticides causes development of resistance, biological magnification of toxic substances through the food chain, and adverse effects on the environment and human health. In this scenario, eco-friendly control tools of mosquito vectors are a priority. Here single-step fabrication of silver nanoparticles (AgNP) using a cheap aqueous leaf extract of Zornia diphylla as reducing and capping agent pf Ag+ ions has been carried out. Biosynthesized AgNP were characterized by UV–visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX) and X-ray diffraction analysis (XRD). The acute toxicity of Z. diphylla leaf extract and biosynthesized AgNP was evaluated against larvae of the malaria vector Anopheles subpictus, the dengue vector Aedes albopictus and the Japanese encephalitis vector Culex tritaeniorhynchus. Both the Z. diphylla leaf extract and Ag NP showed dose dependent larvicidal effect against all tested mosquito species. Compared to the leaf aqueous extract, biosynthesized Ag NP showed higher toxicity against An. subpictus, Ae. albopictus, and Cx. tritaeniorhynchus with LC50 values of 12.53, 13.42 and 14.61μg/ml, respectively. Biosynthesized Ag NP were found safer to non-target organisms Chironomus circumdatus, Anisops bouvieri and Gambusia affinis, with the respective LC50 values ranging from 613.11 to 6903.93μg/ml, if compared to target mosquitoes. Overall, our results highlight that Z. diphylla-fabricated Ag NP are a promising and eco-friendly tool against larval populations of mosquito vectors of medical and veterinary importance, with negligible toxicity against other non-target organisms.