Diplonychus Indicus Research Articles

Essential oil from Piper tuberculatum Jacq. (Piperaceae) and its majority compound β-caryophyllene: mechanism of larvicidal action against Aedes aegypti (Diptera: Culicidae) and selective toxicity.

Synthetic insecticides have been the primary approach in controlling Aedes aegypti; however, their indiscriminate use has led to the development of resistance and toxicity to non-target animals. In contrast, essential oils (EOs) are alternatives for vector control. This study investigated the mechanism of larvicidal action of the EO and β-caryophyllene from Piper tuberculatum against A. aegypti larvae, as well as evaluated the toxicity of both on non-target animals. The EO extracted from P. tuberculatum leaves was majority constituted of β-caryophyllene (54.8%). Both demonstrated larvicidal activity (LC50 of 48.61 and 57.20ppm, p < 0.05), acetylcholinesterase inhibition (IC50 of 57.78 and 71.97ppm), and an increase in the production of reactive oxygen and nitrogen species in larvae after exposure to the EO and β-caryophyllene. Furthermore, EO and β-caryophyllene demonstrate no toxicity to non-target animals Toxorhynchites haemorrhoidalis, Anisops bouvieri, and Diplonychus indicus (100% of survival rate), while the insecticide α-cypermethrin was highly toxic (100% of death). The results demonstrate that the EO from P. tuberculatum and β-caryophyllene are important larvicidal agents.

Essential oil and fenchone extracted from Tetradenia riparia (Hochstetter.) Codd (Lamiaceae) induce oxidative stress in Culex quinquefasciatus larvae (Diptera: Culicidae) without causing lethal effects on non-target animals.

We investigated the larvicidal activity of the essential oil (EO) from Tetradenia riparia and its majority compound fenchone for controlling Culex quinquefasciatus larvae, focusing on reactive oxygen and nitrogen species (RONS), catalase (CAT), glutathione S-transferase (GST), acetylcholinesterase (AChE) activities, and total thiol content as oxidative stress indicators. Moreover, the lethal effect of EO and fenchone was evaluated against Anisops bouvieri, Diplonychus indicus, Danio rerio, and Paracheirodon axelrodi. The EO and fenchone (5 to 25µg/mL) showed larvicidal activity (LC50 from 16.05 to 18.94µg/mL), followed by an overproduction of RONS, and changes in the activity of CAT, GST, AChE, and total thiol content. The Kaplan-Meier followed by Log-rank (Mantel-Cox) analyses showed a 100% survival rate for A. bouvieri, D. indicus, D. rerio, and P. axelrodi when exposed to EO and fenchone (262.6 and 302.60µg/mL), while α-cypermethrin (0.25µg/mL) was extremely toxic to these non-target animals, causing 100% of death. These findings emphasize that the EO from T. riparia and fenchone serve as suitable larvicides for controlling C. quinquefasciatus larvae, without imposing lethal effects on the non-target animals investigated.

Mosquitocidal Susceptibility and Non-Target Effects of Tricholoma equestre Mushroom (Agaricomycetes) on the Immature Stages of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus.

The worldwide scientific community is well aware that mosquitoes are the sole agents responsible for transmitting various dreadful diseases and critical illnesses caused by vector-borne pathogens. The primary objective of this current research was to evaluate the effectiveness of methanol extract from Tricholoma equestre mushroom in controlling the early life stages of Culex quinquefasciatus Say, Anopheles stephensi Liston, and Aedes aegypti (Linnaeus in Hasselquist) mosquitoes. The larvae, pupae and eggs of these mosquitoes were exposed to four different concentrations (62.5 to 500 ppm). After 120 h of treatment, the methanol extract of T. equestre exhibited ovicidal activity ranging from 66% to 80% against the eggs of the treated mosquitoes. It also demonstrated promising larvicidal and pupicidal activity with LC50 values of 216-300 and 230-309 ppm against the early life stages of all three mosquito species. Extensive toxicity studies revealed that the methanol extract from T. equestre had no harmful effects on non-target organisms. The suitability index (SI) or predator safety factor (PSF) indicated that the methanol extract did not harm Poecilia reticulata Peters 1859, (predatory fish), Gambusia affinis S. F. Baird & Girard 1853, dragonfly nymph and Diplonychus indicus Venkatesan & Rao 1871 (water-bug). Gas chromatography-mass spectrometry (GCMS) analysis identified key compounds, including 3-butenenitrile, 2-methyl-(25.319%); 1-butanol, 2-nitro-(18.87%) and oxalic acid, heptyl propyl ester (21.82%) which may be responsible for the observed activity. Furthermore, the formulation based on the methanol extract demonstrated similar effectiveness against all treated mosquitoes at the laboratory level and was found to be non-toxic to mosquito predators. This groundbreaking research represents the first confirmation that methanol extract from T. equestre could be effectively employed in preventing mosquito-borne diseases through mosquito population control programs.

Biocontrol efficacy of apigenin isolated from Anisomeles indica (L.) Kuntze against immature stages of Culex quinquefasciatus (Say, 1823) and its in silico studies

Culex quinquefasciatus is a vector of medical importance since it transmits pathogens to humans, and domestic and wild animals. Synthetic chemical insecticides which are widely used to control mosquitoes are also reported to cause severe threats to humans, non-target organisms and the environment. However, bioactive products derived from plants for mosquito control are eco-friendly, target-specific, safe to non-target organisms, biodegradable, less toxic and reduce development of drug resistance. Therefore, the goal of the present study was to evaluate the biocontrol efficacy of Anisomeles indica (L.) Kuntze on immature stages namely eggs, pupae, and larvae of Cx. quinquefasciatus. In the preliminary screening, hexane and chloroform extracts were found active which were blended and subjected to column chromatography that finally yielded the active phytochemical apigenin. Against Cx. quinquefasciatus, apigenin caused 74% egg mortality at 2 ppm concentration after 120 h of exposure, 72% larvicidal activity with LC50 and LC90 values of 1.3 and 3.9 ppm, respectively, after 24 h, and 65% pupicidal activity with LC50 and LC90 values of 1.3 and 3.7 ppm, respectively, after 24 h exposure. Histopathology study of the exposed larvae revealed that apigenin caused damages on the midgut epithelial columnar cells and remarkable deformities in their structural development, whereas no toxicity was caused on the tested non-target organisms, Gambusia affinis (mosquito fish) and Diplonychus indicus (water bug). Docking study demonstrated that apigenin bounded and inhibited AChE1 of Cx. quinquefasciatus, which resulted in larval mortality. The present study manifested that the isolated metabolite apigenin from A. indica could be a promising biopesticide to control vector mosquitoes.

Essential oil of Origanum vulgare, its nanoemulsion and bioactive monoterpenes as eco-friendly novel green pesticides for controlling Aedes aegypti, the common vector of Dengue virus

ABSTRACT Essential oil (EO) of Origanum vulgare L. was hydrodistilled and analysed using gas chromatography–flame ionization detection and gas chromatography–mass spectrometry. The monoterpenes, carvacrol (61.2%), γ-terpinene (9.6%), thymol (8.3%), and p-cymene (5.7%) were identified. Oil-in-water nanoemulsion was prepared and characterized from the EO through a green procedure. Botanicals had a remarkable mosquitocidal and effectively inhibited acetylcholinesterase activity of Aedes aegypti. The nanoemulsion at 40 µg/ml caused 100% adult and larval mortality after 12 h. At 80 µg/ml, percentage mortality caused by EO products ranged between 55.11-100% for larvae, and 63.0 -100%. for adults After 24 h exposure, LC50's ranged between 13.2 and 75.7 µg/ml against larvae, and between 10.1 and 36.0 µg/ml against adults. The lethal time (LT50) decreased with nanoemulsion, EO and carvacrol. Test products were safe towards the non-target aquatic species, Gambusia affinis and Diplonychus indicus. Results recommend test botanicals as natural alternatives to control Ae. aegypti.

Essential oil of Piper purusanum C.DC (Piperaceae) and its main sesquiterpenes: biodefensives against malaria and dengue vectors, without lethal effect on non-target aquatic fauna.

The mosquito vectors of the genera Aedes and Anopheles present resistance to several commercial insecticides, which are also toxic to non-predator targets. On the other hand, essential oils are a promising source of insecticides. Thus, in this work, the essential oil from the leaves of Piper purusanum was characterized by gas chromatography-based approaches and evaluated as biodefensive against malaria and dengue vectors. The main compounds of P. purusanum essential oil were β-caryophyllene (57.05%), α-humulene (14.50%), and germacrene D (8.20%). The essential oil inhibited egg hatching (7.6 ± 1.5 to 95.6 ± 4.5%), caused larval death (LC50 from 49.84 to 51.60ppm), and inhibited the action of acetylcholinesterase (IC50 of 2.29µg/mL), which can be related to the mechanisms of action. On the other hand, the biological activities of β-caryophyllene, α-humulene, and germacrene D were higher than that of essential oil. In addition, these sesquiterpenes and essential oil did not show a lethal effect on Toxorhynchites splendens, Anisops bouvieri, Gambusia affinis, and Diplonychus indicus (LC50 from 2098.80 to 7707.13ppm), although D. indicus is more sensitive (SI/PSF from 48.56 to 252.02ppm) to essential oil, representing a natural alternative against these relevant vectors.

Toxicity of Trewia nudiflora-mediated silver nanoparticles on mosquito larvae and non-target aquatic fauna

In this study, we synthesized and characterized (UV–vis, XRD, FTIR, SEM, TEM, and AFM) Trewia nudiflora-assisted silver nanoparticles (Tn-AgNPs). The toxicity of T. nudiflora leaf aqueous extract and Tn-AgNPs was tested against Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus larvae and its LC50 values were 121.82/16.69, 130.51/18.11, and 142.38/19.53 μg mL–1, respectively. Moreover, the biotoxicity was analyzed against the aquatic non-target fauna Anisops bouvieri, Diplonychus indicus, and Gambusia affinis. The LC50 values of non-target fauna were 1064.66–26,537.05 μg mL–1. Thus, the Tn-AgNPs significantly controlled the mosquito larvae with less toxic effects on aquatic non-target fauna.

Laboratory evaluation on the efficacy of Bacillus thuringiensis var. israelensis Berliner 1915 (Bacillaceae) on the instars of the dengue vector Aedes aegypti Linnaeus 1762 (Diptera: Culicidae) and against the adults of Diplonychus indicus Venk. & Rao (Hemiptera: Belostomatidae) as non-target organisma

Mosquito control agents based on bacterial insecticides are the most widely used microbial pesticides as they are environment friendly alternatives to chemical insecticides and hold tremendous potential with improved efficacy. On the other hand, it is also necessary to preserve the non-target organisms, especially those that predate upon target mosquito larvae. Since, chemical larvicides are largely non-selective owing to their deleterious role on non-target organisms, bacterial insecticides when used do not cause harm to them. Therefore, in the present investigation, the toxicity of Bacillus thuringiensis var. israelensis was evaluated on all the larval instars of Aedes aegypti at concentrations of 0.1, 0.2, 0.3 and 0.4%. The LC50 values after 24, 48 and 72 hours against the first, second, third and fourth instars were 0.20, 0.19 and 0.17%; 0.16, 0.15 and 0.15%; 0.19, 0.18 and 0.16%; 0.14, 0.12 and 0.12% respectively. Further, the adults of Diplonychus indicus which were tested as the non-target organism was exposed to the same concentrations of bacterial formulation and the results indicated that they did not have toxic effect and that the treated adult bugs were normal with high predatory potential. The present research indicated that integration with appropriate biocides may not interfere with the biocontrol potential of the predator in controlling mosquitoes.

Swift fabrication of Ag nanostructures using a colloidal solution of Holostemma ada-kodien (Apocynaceae) – Antibiofilm potential, insecticidal activity against mosquitoes and non-target impact on water bugs

Recent research in entomology and parasitology focused on the efficacy of green fabricated nanomaterials as novel insecticides. In this study, we synthesized poly-dispersed and stable silver nanoparticles (AgNPs) using the leaf extract of Holostemma ada-kodien. The nanostructures were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and X-ray diffraction analysis. The efficacy of H. ada-kodien leaf extract and AgNPs in vector control was evaluated against the mosquitoes Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus, which act as major vectors of important parasitic and arboviral diseases. AgNPs showed higher toxicity if compared to the H. ada-kodien leaf aqueous extract, LC50 towards larvae of A. stephensi, A. aegypti, and C. quinquefasciatus were 12.18, 13.30, and 14.70 μg/mL, respectively. When the AgNPs were tested on non-target water bugs, Diplonychus indicus, the LC50 value was 623.48 μg/mL. Furthermore, 100 μl/mL of AgNPs achieved significant antimicrobial activity against Bacillus pumilus, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris, and Candida albicans. Light and confocal laser scanning microscopy highlighted a major impact of the H. ada-kodien-synthesized AgNPs on the external topography and architecture of microbial biofilms, both on Gram-positive and Gram-negative bacteria. Overall, this study sheds light on the insecticidal and antibiofilm potential of H. ada-kodien-synthesized AgNPs, a potential green resource for the rapid synthesis of polydispersed and highly stable AgNPs.

Eco-friendly and cost-effective Ag nanocrystals fabricated using the leaf extract of Habenaria plantaginea: toxicity on six mosquito vectors and four non-target species.

Recently, the biofabrication of metal nanoparticles has gained wide interest owing to its inherent features such as swift, simplicity, eco-friendliness, and cheaper costs. Different green-reducing agents led to the production of nanoparticles with varying toxicity on insects. In the current study, silver nanoparticles (AgNPs) were successfully synthesized using Habenaria plantaginea leaf extract. Ag nanoparticles were studied by UV-Vis spectroscopy (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). H. plantaginea extract and AgNPs were tested for mosquito larvicidal activity on Anopheles stephensi, Aedes aegypti, Culex quinquefasciatus, An. subpictus, Ae. albopictus, and Cx. tritaeniorhynchus. LC50 values were 102.51, 111.99, 123.47, 123.96, 136.56, 149.42μg/ml and 12.23, 13.38, 14.78, 14.37, 15.39, 16.89μg/ml, respectively. Moreover, H. plantaginea aqueous extract and AgNPs were tested against the non-target species Anisops bouvieri, Diplonychus indicus, Poecilia reticulata, and Gambusia affinis obtaining LC50 values ranging from 831.82 to 36,212.67μg/ml. Overall, this study showed the effectiveness of H. plantaginea-fabricated nanoparticles on a wide range of important mosquito vectors, highlighting their scarce toxicity on four natural enemies predating mosquito larvae and pupae.

Size-controlled biofabrication of silver nanoparticles using the Merremia emarginata leaf extract: Toxicity on Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) and non-target mosquito predators

Mosquito-borne diseases represent a major human and animal health problem in all tropical and subtropical countries worldwide. The synthesis of eco-friendly metal nanoparticles is a fast-growing branch of current nanoscience with a number of biomedical and entomological implications. In this study, we investigated the one-pot synthesis of silver nanoparticles (Ag NPs) using a cheap leaf extract of Merremia emarginata (Convolvulaceae). Bio-reduced Ag NPs were characterized by UV–visible spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction analysis, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. SEM, TEM and AFM morphological nanocharacterization showed that this synthesis led to the production of size-controlled Ag NPs, ranging from 25 to 65nm. The acute toxicity of M. emarginata leaf extract and biosynthesized Ag NPs was evaluated against third instar larvae of the malaria vector Anopheles stephensi, the dengue and Zika virus vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. Compared to the leaf aqueous extract, Ag NPs showed higher toxicity against A. stephensi, A. aegypti, and C. quinquefasciatus with LC50 values of 8.36, 9.20 and 10.02μg/mL, respectively. M. emarginata-fabricated Ag NPs were found safer to non-target aquatic biocontrol agents Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 ranging from 415.61 to 25,153.46μg/mL. However, although it has been proven the AgNPs fabricated in the present study are more effective if compared to the crude M. emarginata extract, they still exert some toxicity on biocontrol agents, thus further research is required to produce more eco-friendly formulations for field purposes.

Larvicidal activity of the essential oil from Amomum subulatum Roxb. (Zingiberaceae) against Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus (Diptera: Culicidae), and non-target impact on four mosquito natural enemies

Mosquitoes (Diptera: Culicidae) are the primary vectors of several serious diseases that affect both animals and humans. Most of these diseases, especially the ones that are caused by arboviruses such as Zika, dengue and Japanese encephalitis, cannot be effectively prevented or treated, thereby rendering the discovery of alternative measures for the control of mosquito-borne diseases an absolute necessity. The current study evaluates the acute toxicity of Amomum subulatum-derived essential oil against Anopheles subpictus, Aedes albopictus, and Culex tritaeniorhynchus. We used gas chromatography–mass spectroscopy to analyze the chemical composition of A. subulatum EO. Analysis revealed thirty-three components. Primary constituents were 1,8- cineole (39.8%) and α-terpineol (11.5%). The essential oil from A. subulatum demonstrated a significant toxic effect against An. subpictus, Ae. albopictus and Cx. tritaeniorhynchus third instar larvae, with LC50 values of 41.25, 44.11 and 48.12 μg/ml and LC90 values of 80.29, 85.6 and 89.30 μg/ml, respectively. Concerning non-target effects in the aquatic environment, we evaluated the acute toxicity of A. subulatum oil on 4 mosquito biocontrol agents, Anisops bouvieri, Diplonychus indicus, Poecilia reticulata and Gambusia affinis. We observed that the toxicity of this oil was extremely low, with LC50 ranging between 3123 and 9104 μg/ml. In conclusion, the A. subulatum essential oil is an interesting bioresource to develop environmental friendly mosquito larvicides. Indeed, it is effective against different Culicidae species with LC50 always lower than 50 μg/ml, while LC50 calculated for non-target organisms are about 100-fold higher.

Green and facile biosynthesis of silver nanocomposites using the aqueous extract of Rubus ellipticus leaves: Toxicity and oviposition deterrent activity against Zika virus, malaria and filariasis mosquito vectors

Botanical-based nanosynthesis has been recently reported as a cheap alternative for mosquito management. In this study, we investigated the synthesis of silver nanoparticles (AgNPs) using the leaf extract of Rubus ellipticus and AgNPs were characterized using UV–vis spectroscopy, XRD, FTIR, SEM, TEM and EDX analyses. The toxicity of R. ellipticus leaf extract and AgNPs was evaluated against eggs, larvae and adults of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. Compared to the leaf aqueous extract, biosynthesized AgNPs showed higher toxicity against the mosquito larvae with LC50 values of 12.50, 13.83 and 15.09μg/mL, respectively. AgNPs exerted zero hatchability at 60, 75 and 90μg/mL on A. stephensi, A. aegypti, and C. quinquefasciatus, respectively. Concentrations of 12–60μg/mL reduced egg laying by gravid females from 72.28 to 91.48%. Maximum adulticidal efficacy was observed for AgNPs, with LD50 values were 21.10, 23.04 and 25.06μg/mL, respectively. AgNPs were found safer to non-target organisms Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 values ranging from 896 to 2261μg/mL. Overall, R. ellipticus-fabricated AgNPs acted as effective toxic agents and ovideterrents against three important mosquitoes species, with little harmful effects on non-target aquatic species.

Towards green oviposition deterrents? Effectiveness of Syzygium lanceolatum (Myrtaceae) essential oil against six mosquito vectors and impact on four aquatic biological control agents.

Essential oils (EOs) from plants may be alternative sources of molecules toxic against mosquito vectors of public health relevance. Most of researches in this field focused on EOs as larvicides or ovicides, while limited efforts focused on the exploitation of EOs as oviposition deterrents. In the present study, the larvicidal and oviposition deterrent activity of Syzygium lanceolatum leaf EO was evaluated against six mosquito species, Anopheles stephensi, An. subpictus, Aedes aegypti, Ae. albopictus, Culex quinquefasciatus, and Cx. tritaeniorhynchus. The chemical composition of the S. lanceolatum EO was analyzed by GC-MS analysis, showing the presence of phenyl propanal, β-caryophyllene, α-humulene, and caryophyllene oxide as major constituents. S. lanceolatum EO showed high acute toxicity on An. stephensi (LC50=51.20μg/ml), Ae. aegypti (LC50=55.11μg/ml), Cx. quinquefasciatus (LC50=60.01μg/ml), An. subpictus (LC50=61.34μg/ml), Ae. albopictus (LC50=66.71μg/ml), and Cx. tritaeniorhynchus (LC50=72.24μg/ml) larvae. Furthermore, the EO was effective as oviposition deterrent against the six tested mosquito species, with OAI on An. stephensi, An. subpictus, Ae. aegypti, Ae. albopictus, Cx. quinquefasciatus, and Cx. tritaeniorhynchus reaching -0.83, -0.81, -0.84, -0.83, -0.84, and -0.86, respectively. The toxicity of S. lanceolatum EO against several biological control agents of mosquitoes, including water bugs (Anisops bouvieri and Diplonychus indicus) and fishes (Gambusia affinis and Poecilia reticulata), was extremely low, with LC50 ranging between 4148 and 15,762μg/ml. Overall, our results pointed out the promising potential of the S. lanceolatum leaf EO as a source of environmental-friendly oviposition deterrents and larvicides effective against a wide number of mosquito species of importance for parasitology.

One Pot Green Synthesis of Colloidal Silver Nanocrystals Using the Ventilago maderaspatana Leaf Extract: Acute Toxicity on Malaria, Zika Virus and Filariasis Mosquito Vectors

Mosquitoes act as a vector for most of the life-threatening diseases. The green synthesis of eco-friendly metal nanoparticles is a fast-growing branch of current nanoscience with a number of biomedical and entomological implications. Here, we have synthesized silver nanoparticles (AgNPs) by using a poorly studied Indian plant, Ventilago maderaspatana. The results recorded from UV–Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the quick synthesis of AgNPs. The toxic activity of V. maderaspatana leaf extract and biosynthesized AgNPs was evaluated against the malaria vector Anopheles stephensi, the Zika virus vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. Compared to the leaf aqueous extract, AgNPs showed higher toxicity against A. stephensi, A. aegypti, and C. quinquefasciatus with LC50 values of 24.89, 26.92 and 29.24 μg/mL, respectively. A single treatment with AgNPs tested at 120, 150 and 180 μg/mL led to no egg hatchability. In adulticidal experiments, the maximum efficacy was observed on A. stephensi (LD50 = 41.19 μg/mL), followed by A. aegypti (LD50 = 44.85 μg/mL) and C. quinquefasciatus (LD50 = 48.94 μg/mL), respectively. V. maderaspatana extract and green fabricated AgNPs were found safer to non-target aquatic biocontrol organisms Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 ranging from 1673 to 41,854 µg/ml.

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.

Single-step biological fabrication of colloidal silver nanoparticles using Hugonia mystax: larvicidal potential against Zika virus, dengue, and malaria vector mosquitoes

Mosquito control is facing key challenges, including outbreaks of new arbovirus threats. We proposed an eco-friendly synthesis of silver nanoparticles (AgNPs) employing a low-cost extract of Hugonia mystax. AgNPs were specified by UV, XRD, FTIR and EDX spectroscopy, SEM and TEM. AgNPs were more toxic to Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus larvae (LC50: 14.45, 15.86, and 17.46 μg/mL) if compared to aquatic biocontrol organisms Gambusia affinis, Diplonychus indicus, and Anisops bouvieri (LC50: 2567.15, 1075.16, and 829.63 μg/ml). Overall, we shed light on the mosquito larvicidal efficacy of H. mystax, a possible biological resource for low-cost fabrication of AgNPs.

Acute toxicity and repellent activity of the Origanum scabrum Boiss. & Heldr. (Lamiaceae) essential oil against four mosquito vectors of public health importance and its biosafety on non-target aquatic organisms.

The recent outbreaks of dengue, chikungunya, and Zika virus highlighted the pivotal importance of mosquito vector control in tropical and subtropical areas worldwide. However, mosquito control is facing hot challenges, mainly due to the rapid development of pesticide resistance in Culicidae and the limited success of biocontrol programs on Aedes mosquitoes. In this framework, screening botanicals for their mosquitocidal potential may offer effective and eco-friendly tools in the fight against mosquitoes. In the present study, the essential oil (EO) obtained from the medicinal plant Origanum scabrum was analyzed by GC-MS and evaluated for its mosquitocidal and repellent activities towards Anopheles stephensi, Aedes aegypti, Culex quinquefasciatus, and Culex tritaeniorhynchus. GC-MS analysis showed a total of 28 compounds, representing 97.1% of the EO. The major constituents were carvacrol (48.2%) and thymol (16.6%). The EO was toxic effect to the A. stephensi, A. aegypti, C. quinquefasciatus, and C. tritaeniorhynchus larvae, with LC50 of 61.65, 67.13, 72.45, and 78.87μg/ml, respectively. Complete ovicidal activity was observed at 160, 200, 240, and 280μg/ml, respectively. Against adult mosquitoes, LD50 were 122.38, 134.39, 144.53, and 158.87μg/ml, respectively. In repellency assays, the EOs tested at 1.0, 2.5, and 5.0mg/cm2 concentration of O. scabrum gave 100% protection from mosquito bites up to 210, 180, 150, and 120min, respectively. From an eco-toxicological point of view, the EO was tested on three non-target mosquito predators, Gambusia affinis, Diplonychus indicus, and Anisops bouvieri, with LC50 ranging from 4162 to 12,425μg/ml. Overall, the EO from O. scabrum may be considered as a low-cost and eco-friendly source of phytochemicals to develop novel repellents against Culicidae.

Single-Step Biofabrication of Silver Nanocrystals Using Naregamia alata: A Cost Effective and Eco-Friendly Control Tool in the Fight Against Malaria, Zika Virus and St. Louis Encephalitis Mosquito Vectors

Botanical-based nanosynthesis has been recently reported as a cheap alternative for mosquito management. Screening different botanicals as reducing and capping agents led to the production of metal nanoparticles with different biophysical and mosquitocidal features. Here, Naregamia alata-mediated biosynthesis of silver nanoparticles (AgNPs) was conducted. AgNPs were tested on egg, larval and adult populations of three important mosquito vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. AgNPs were characterized using UV–Vis spectrophotometry, FTIR, AFM, SEM, TEM, EDX, and XRD analyses. Maximum larvicidal toxicity was detected against A. stephensi (LC50 = 12.40 µg/ml), followed by A. aegypti (LC50 = 13.57 µg/ml) and C. quinquefasciatus (LC50 = 14.84 µg/ml). A single treatment with AgNPs tested at 60, 75 and 90 μg/ml led to no egg hatchability. In adulticidal experiments, the maximum efficacy was observed on A. stephensi (LD50 = 31.60 μg/ml), followed by A. aegypti (LD50 = 34.31 μg/ml) and C. quinquefasciatus (LD50 = 37.52 μg/ml), respectively. AgNPs were safer for three non-target mosquito natural enemies, Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 ranging from 629 to 2111 µg/ml. Overall, N. alata-fabricated AgNPs are a promising and eco-friendly tool against Anopheles, Aedes and Culex mosquito vectors, with negligible toxicity against non-target aquatic organisms.

Eco-friendly larvicides from Indian plants: Effectiveness of lavandulyl acetate and bicyclogermacrene on malaria, dengue and Japanese encephalitis mosquito vectors

Mosquitoes (Diptera: Culicidae) are a key threat for millions of people and animals worldwide, since they act as vectors for devastating pathogens and parasites, including malaria, dengue, Japanese encephalitis, filiariasis and Zika virus. Mosquito young instars 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. In this scenario, newer and safer tools have been recently implemented to enhance mosquito control. The concrete potential of screening plant species as sources of metabolites for entomological and parasitological purposes is worthy of attention, as recently elucidated by the Y. Tu's example. Here we investigated the toxicity of Heracleum sprengelianum (Apiaceae) leaf essential oil and its major compounds toward third instar larvae of the malaria vector Anopheles subpictus, the arbovirus vector Aedes albopictus and the Japanese encephalitis vector Culex tritaeniorhynchus. GC–MS analysis showed that EO major components were lavandulyl acetate (17.8%) and bicyclogermacrene (12.9%). The EO was toxic to A. subpictus, A. albopictus, and C. tritaeniorhynchus, with LC50 of 33.4, 37.5 and 40.9µg/ml, respectively. Lavandulyl acetate was more toxic to mosquito larvae if compared to bicyclogermacrene. Their LC50 were 4.17 and 10.3µg/ml for A. subpictus, 4.60 and 11.1µg/ml for A. albopictus, 5.11 and 12.5µg/ml for C. tritaeniorhynchus. Notably, the EO and its major compounds were safer to three non-target mosquito predators, Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 ranging from 206 to 4219µg/ml. Overall, this study highlights that H. sprengelianum EO is a promising source of eco-friendly larvicides against three important mosquito vectors with moderate toxicity against non-target aquatic organisms.