Mosquito larvicidal properties of silver nanoparticles synthesized using Heliotropium indicum (Boraginaceae) against Aedes aegypti,Anopheles stephensi,and Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes transmit dreadful diseases to human beings wherein biological control of these vectors using plant-derived molecules would be an alternative to reduce mosquito population. In the present study activity of aqueous leaf extract and silver nanoparticles (AgNPs) synthesized using Helitropium indicum plant leaves against late third instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The range of varying concentrations of synthesized AgNPs (8, 16, 24, 32, and 40 μg/mL) and aqueous leaf extract (30, 60, 90, 120, and 150 μg/mL) were tested against the larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The synthesized AgNPs from H. indicum were highly toxic than crude leaf aqueous extract in three important vector mosquito species. The results were recorded from UV–Vis spectrum, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis, transmission electron microscopy, and histogram. The synthesized AgNPs showed larvicidal effects after 24 h of exposure. Considerable mortality was evident after the treatment of H. indicum for all three important vector mosquitoes. The LC₅₀ and LC₉₀ values of H. indicum aqueous leaf extract appeared to be effective against A. stephensi (LC₅₀, 68.73 μg/mL; LC₉₀, 121.07 μg/mL) followed by A. aegypti (LC₅₀, 72.72 μg/mL; LC₉₀, 126.86 μg/mL) and C. quinquefasciatus (LC₅₀, 78.74 μg/mL; LC₉₀, 134.39 μg/mL). Synthesized AgNPs against the vector mosquitoes of A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 18.40 and 32.45 μg/mL, A. aegypti had LC₅₀ and LC₉₀ values of 20.10 and 35.97 μg/mL, and C. quinquefasciatus had LC₅₀ and LC₉₀ values of 21.84 and 38.10 μg/mL. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H. indicum and green synthesis of silver nanoparticles have the potential to be used as an ideal ecofriendly approach for the control of A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

Low-cost and eco-friendly green synthesis of silver nanoparticles using Feronia elephantum (Rutaceae) against Culex quinquefasciatus,Anopheles stephensi,and Aedes aegypti (Diptera: Culicidae)

Mosquitoes transmit serious human diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of synthesized natural products for vector control have been a priority in this area. In the present study, the larvicidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against late third-instar larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (5, 10, 15, 20, and 25 μg mL^?1) and aqueous leaf extract (25, 50, 75, 100, and 125 μg mL^?1) were tested against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus. Larvae were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy analysis (EDX). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 11.56 and 20.56 μg mL^?1; A. aegypti had LC₅₀ and LC₉₀ values of 13.13 and 23.12 μg mL^?1; and C. quinquefasciatus had LC₅₀ and LC₉₀ values of 14.19 and 24.30 μg mL^?1. No mortality was observed in the control. These results suggest that the green synthesis of silver nanoparticles using F. elephantum has the potential to be used as an ideal eco-friendly approach for the control of A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

Chemical constituents and larvicidal potential of Feronia limonia leaf essential oil against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

In the present investigation, the leaf essential oil of Feronia limonia was evaluated for chemical constituents and mosquito larvicidal activity against the larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. GC and GC–MS analyses revealed that the essential oil contain 51 compounds. Estragole (34.69 %) and β-pinene(23.59 %) were identified as the major constituents followed by methyl (Z)-caryophyllene (11.05 %), eugenol (6.50 %), linalool (3.97 %), phytol (3.27 %), sabinene (2.41 %) and limonene (2.27 %). Larval mortality was observed after 12 and 24 h of exposure period. The oil showed remarkable larvicidal activity against A. stephensi (LC₅₀?=?38.93 and LC₉₀?=?108.64 ppm (after 12 h); LC₅₀?=?15.03 and LC₉₀?=?36.69 ppm (after 24 h)), A. aegypti (LC₅₀?=?37.60 and LC₉₀?=?104.69 ppm (after 12 h); LC₅₀?=?11.59 and LC₉₀?=?42.95 ppm (after 24 h)) and C. quinquefasciatus (LC₅₀?=?52.08 and LC₉₀?=?124.33 ppm (after 12 h); LC₅₀?=?22.49 and LC₉₀?=?60.90 ppm (after 24 h)). Based on the results, the essential oil of F. limonia can be considered as a new source of larvicide for the control of vector mosquitoes.     

Green synthesis of silver nanoparticles using Sida acuta (Malvaceae) leaf extract against Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti (Diptera: Culicidae)

Mosquitoes act as a vector for most of the life-threatening diseases like malaria, yellow fever, dengue fever, chikungunya fever, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management, emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain, and adverse effects on environmental quality and nontarget organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are nontoxic, easily available at affordable prices, biodegradable, and show broad-spectrum target-specific activities against different species of vector mosquitoes. In the present study, the larvicidal activity of silver nanoparticles (AgNPs) synthesized using Sida acuta plant leaf extract against late third instar larvae of Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti was determined. Range of concentrations of synthesized AgNPs (10, 20, 30, 40, and 50 μg/mL) and aqueous leaf extract (50, 100, 150, 200, and 250 μg/mL) were tested against the larvae of C. quinquefasciatus, A. stephensi and A. aegypti. The synthesized AgNPs from S. acuta leaf were highly toxic than crude leaf aqueous extract in three important vector mosquito species. The results were recorded from UV–Vis spectrum, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Larvae were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of S. acuta for all three important vector mosquitoes. The LC₅₀ and LC₉₀ values of S. acuta aqueous leaf extract appeared to be most effective against A. stephensi (LC₅₀, 109.94 μg/mL and LC₉₀, 202.42 μg/mL) followed by A. aegypti LC₅₀ (119.32 μg/mL and LC₉₀, 213.84 μg/mL) and C. quinquefasciatus (LC₅₀, 130.30 μg/mL and LC₉₀, 228.20 μg/mL). Synthesized AgNPs against the vector mosquitoes of A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 21.92, and 41.07 μg/mL; A. aegypti had LC₅₀ and LC₉₀ values of 23.96, and 44.05 μg/mL; C. quinquefasciatus had LC₅₀ and LC₉₀ values of 26.13 and 47.52 μg/mL. These results suggest that the use of S. acuta synthesized silver nanoparticles can be a rapid, environmentally safer biopesticide which can form a novel approach to develop effective biocides for controlling the target vector mosquitoes. This is the first report on the mosquito larvicidal activity of the plant aqueous extract and synthesized nanoparticles.     

Adulticidal and repellent properties of Cassia tora Linn. (Family: Caesalpinaceae) against Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi

Mosquitoes have developed resistance to various synthetic insecticides, making its control increasingly difficult. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The adulticidal and repellent activities of crude hexane, chloroform, benzene, acetone, and methanol extracts of the leaf of Cassia tora were assayed for their toxicity against three important vector mosquitoes, viz., Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi. The adult mortality was observed after 24?h of exposure. All extracts showed moderate adulticidal effects; however, the highest adult mortality observed was found in methanol extract. The LC₅₀ and LC₉₀ values of C. tora leaf extracts against adulticidal activity of (hexane, chloroform benzene, acetone, and methanol) C. quinquefasciatus, A. aegypti, and A. stephensi were the following: C. quinquefasciatus LC₅₀ values were 338.81, 315.73, 296.13, 279.23, and 261.03?ppm and LC₉₀ values were 575.77, 539.31, 513.99, 497.06, and 476.03?ppm; A. aegypti LC₅₀ values were 329.82, 307.31, 287.15, 269.57, and 252.03?ppm and LC₉₀ values were 563.24, 528.33, 496.92, 477.61, and 448.05?ppm; and A. stephensi LC₅₀ values were 317.28, 300.30, 277.51, 263.35, and 251.43?ppm and LC₉₀ values were 538.22, 512.90, 483.78, 461.08, and 430.70?ppm, respectively. The results of the repellent activity of hexane, chloroform, benzene, acetone, and methanol extracts of C. tora plant at three different concentrations of 1.0, 2.5, and 5.0?mg/cm² were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, this plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This is the first report on mosquito adulticidal and repellent activities of the reported C. tora against mosquito vectors from Southern India.     

Ovicidal,larvicidal and adulticidal properties of Asparagus racemosus (Willd.) (Family: Asparagaceae) root extracts against filariasis (Culex quinquefasciatus), dengue (Aedes aegypti) and malaria (Anopheles stephensi) vector mosquitoes (Diptera: Culicidae)

Several diseases are associated to the mosquito–human interaction. Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikungunya fever, West Nile virus and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. The present investigation was undertaken to study the ovicidal, larvicidal and adulticidal activities of crude hexane, ethyl acetate, benzene, chloroform and methanol extracts of root of Asparagus racemosus were assayed for their toxicity against three important vector mosquitoes, viz., Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi (Diptera: Culicidae). The mean percent hatchability of the eggs was observed after 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. All the five solvent extracts showed moderate ovicidal activity; however, the methanol extract showed the highest ovicidal activity. The methanol extract of Asparagus racemosus against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi exerted 100 % mortality (zero hatchability) at 375, 300 and 225 ppm, respectively. Control eggs showed 99–100 % hatchability. The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in methanol extract of root of Asparagus racemosus against the larvae of Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi with the LC₅₀ and LC₉₀ values were 115.13, 97.71 and 90.97 ppm and 210.96, 179.92, and 168.82 ppm, respectively. The adult mortality was observed after 24 h recovery period. The plant crude extracts showed dose-dependent mortality. At higher concentrations, the adult showed restless movement for some times with abnormal wagging and then died. Among the extracts tested, the highest adulticidal activity was observed in methanol extract against Anopheles stephensi followed by Aedes aegypti and Culex quinquefasciatus with the LD₅₀ and LD₉₀ values were 120.44, 135.60, and 157.71 ppm and 214.65, 248.35, and 290.95 ppm, respectively. No mortality was recorded in the control. The finding of the present investigation revealed that the root extract of Asparagus racemosus possess remarkable ovicidal, larvicidal and adulticidal activity against medically important vector mosquitoes and this is the low cost and ideal eco-friendly approach for the control of mosquitoes. This is the first report on the mosquito ovicidal, larvicidal and adulticidal activities of the reported Asparagus racemosus root.     

Studies on the impact of biosynthesized silver nanoparticles (AgNPs) in relation to malaria and filariasis vector control against Anopheles stephensi Liston and Culex quinquefasciatus Say (Diptera: Culicidae)

Biosynthesized nanoparticles have been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. The present study was based on assessments of the larvicidal activities to determine the efficacies of synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Vinca rosea (L.) (Apocynaceae) against the larvae of malaria vector Anopheles stephensi Liston and filariasis vector Culex quinquefasciatus Say (Diptera: Culicidae). Larvae were exposed to varying concentrations of aqueous extract of V. rosea and synthesized AgNPs for 24, 48, and 72 h. AgNPs were rapidly synthesized using the leaf extract of V. rosea, and the formation of nanoparticles was observed within 15 min. The results recorded from UV–Vis spectrum, Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) support the biosynthesis and characterization of AgNPs. The formation of the AgNPs synthesized from the XRD spectrum compared with the Bragg reflections at 2θ?=?29.36, 38.26, 44.51, 63.54, and 77.13° which can be indexed to the (121), (111), (200), (220), and (311) orientations, respectively, confirmed the presence of AgNPs. The FTIR spectra of AgNPs exhibited prominent peaks at the spectra showed sharp and strong absorption band at 3,406.71 to 3,431.90 cm^?1 double in case of NH₂ group of a primary amine (N–H stretch). The presence of the sharp peak at 2,926.54 to 2,925.80 cm^?1 very broad often looks like distorted baseline (O–H carboxylic acids). The band 1,633.26 to 1,625.81 cm^?1 was assigned to C?=?C alkenes, aromatic ring stretching vibration, respectively. SEM analysis of the synthesized AgNPs clearly showed the clustered and irregular shapes, mostly aggregated and having the size of 120 nm. TEM reveals spherical shape of synthesized AgNPs. Particle size analysis revealed that the size of particles ranges from 25 to 47 nm with average size of 34.61 nm. Energy-dispersive X-ray spectroscopy showed the complete chemical composition of the synthesized AgNPs. In larvicidal activity, the results showed that the maximum efficacy was observed in synthesized AgNPs against the fourth instar larvae of A. stephensi (LC₅₀?=?12.47 and 16.84 mg/mL and LC₉₀?=?36.33 and 68.62 mg/mL) on 48 and 72 h of exposure and against C. quinquefasciatus (LC₅₀?=?43.80 mg/mL and LC₉₀?=?120.54 mg/mL) on 72-h exposure, and aqueous extract showed 100 % mortality against A. stephensi and C. quinquefasciatus (LC₅₀?=?78.62 and 55.21 mg/mL and LC₉₀?=?184.85 and 112.72 mg/mL) on 72-h exposure at concentrations of 50 mg/mL, respectively. The AgNPs did not exhibit any noticeable toxicity on Poecilia reticulata after 24, 48, and 72 h of exposure. These results suggest that the synthesized AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi and C. quinquefasciatus. This method is considered as a new approach to control vectors. Therefore, this study provides the first report on the mosquito larvicidal activity of V. rosea synthesized AgNPs against vectors.     

Larvicidal,ovicidal, and adulticidal efficacy of Erythrina indica (Lam.) (Family: Fabaceae) against Anopheles stephensi,Aedes aegypti,and Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes are the major vector for the transmission of malaria, dengue fever, yellow fever, filariasis, schistosomiasis, and Japanese encephalitis. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the larvicidal, ovicidal, and adulticidal potential of the crude hexane, benzene, chloroform, ethyl acetate, and methanol solvent extracts from the medicinal plant Erythrina indica against the medically important mosquito vectors, Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in methanol extract of leaf of E. indica against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus with the LC₅₀ and LC₉₀ values of 69.43, 75.13, and 91.41 ppm and 125.49, 134.31, and 167.14 ppm, respectively. The mean percent hatchability of the eggs was observed after 48 h post treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. All the five solvent extracts showed moderate ovicidal activity; however, the methanol extract showed the highest ovicidal activity. The methanol extract of E. indica against A. stephensi, A. aegypti, and C. quinquefasciatus exerted 100 % mortality (zero hatchability) at 150, 200, and 250 ppm, respectively. Control eggs showed above 99.3–100 % hatchability. The adult mortality was observed after 24 h recovery period. The plant crude extracts showed dose-dependent mortality. At higher concentrations, the adult showed restless movement for some times with abnormal wagging and then died. Among the extracts tested, the highest adulticidal activity was observed in methanol extract against A. stephensi followed by A. aegypti and C. quinquefasciatus with the LD₅₀ and LD₉₀ values of 88.76, 94.09, and 119.64 ppm and 160.83, 169.01, and 219.77 ppm, respectively. No mortality was recorded in the control. Our data suggest that the crude hexane, benzene, chloroform, ethyl acetate, and methanol solvent extracts of E. indica have the potential to be used as an eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus.     

Ovicidal, repellent, adulticidal and field evaluations of plant extract against dengue, malaria and filarial vectors

Mosquitoes are insect vectors responsible for the transmission of parasitic and viral infections to millions of people worldwide, with substantial morbidity and mortality. Infections transmitted by mosquitoes include malaria, yellow fever, chikungunya, filariasis and other arboviruses. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The adulticidal activities of crude hexane, benzene, ethyl acetate, acetone and methanol leaf extracts of Acalypha alnifolia were assayed for their toxicity against three important vector mosquitoes, viz., Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The adult mortality was observed after 24 h of exposure. All extracts showed moderate adulticide effects; however, the highest adult mortality was found in methanol extract were observed. The LC₅₀ values of A. alnifolia leaf extracts against adulticidal activity of (hexane, benzene, ethyl acetate, acetone and methanol) A. aegypti, A. stephensi and C. quinquefasciatus were the following: A. aegypti values were 371.87, 342.97, 320.17, 300.86 and 279.75 ppm; A. stephensi values were 358.35, 336.64, 306.10, 293.01 and 274.76 ppm; C. quinquefasciatus values were 383.59, 354.13, 327.74, 314.33 and 291.71 ppm. The results of the repellent activity of hexane, benzene, ethyl acetate, acetone and methanol extract of A. alnifolia plant at three different concentrations of 1.0, 3.0, and 5.0 mg/cm² were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, this plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. Mean percent hatchability of the ovicidal activity was observed 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100 % with methanol extract of A. alnifolia was exerted at 125 and 300 ppm. The larval density was decreased after the treatment of plant extracts at the breeding sites (water bodies system) of vector mosquitoes, and hence, these plant extracts are suitable alternatives of synthetic insecticides for mosquito vector management.These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This study provides first report on the mosquito ovicidal, repellent and adulticidal activities of these plant extracts against mosquito vector species from India.     

Evaluation of plant-mediated synthesized silver nanoparticles against vector mosquitoes

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Heliotropium indicum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. Adult mosquitoes were exposed to varying concentrations of aqueous extract of H. indicum and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of H. indicum, and the formation of nanoparticles was observed within 6 h. The results recorded from UV–vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the adult of A. stephensi (lethal dose (LD)₅₀?=?26.712 μg/mL; LD₉₀?=?49.061 μg/mL), A. aegypti (LD₅₀?=?29.626 μg/mL; LD₉₀?=?54.269 μg/mL), and C. quinquefasciatus (LD₅₀?=?32.077 μg/mL; LD₉₀?=?58.426 μg/mL), respectively. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H.indicum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.     

Integration of botanical and bacterial insecticide against Aedes aegypti and Anopheles stephensi

The present study evaluated the Orthosiphon thymiflorus leaf extract and the bacterial insecticide spinosad, testing the first to fourth instars larvae and pupae of two important vector mosquitoes, viz., Aedes aegypti, Anopheles stephensi. The fresh leaves of O. thymiflorus were washed thoroughly in tap water and shade-dried at room temperature (28?±?2 °C) for 5 to 8 days. The air-dried materials were powdered separately using a commercial electrical blender. From the plants, 500 g powder was macerated with 1.5 L organic solvents of petroleum ether sequentially for a period of 72 h each and then filtered. The larval and pupal mortality was observed after 24 h of exposure; no mortality was observed in the control group. The first- to fourth-instar larvae and pupae of A. stephensi had values of LC₅₀?=?309.16, 337.58, 390.42, 429.68, and 513.34 ppm, and A. aegypti had values of LC₅₀?=?334.78, 366.45, 422.97, 467.94, and 54.02 ppm, respectively. Spinosad against the A. stephensi had values of LC₅₀?=?384.19, 433.39, 479.17, 519.79, and 572.63 ppm, and A. aegypti had values of LC₅₀?=?210.68, 241.20, 264.93, 283.27, and 305.85 ppm, respectively. Moreover, in combined treatment, the A. stephensi had values of LC₅₀?=?202.36, 224.76, 250.84, 288.05, and 324.05 ppm, and A. aegypti had values of LC₅₀?=?217.70, 246.04, 275.36, 315.29, and 353.80 ppm, respectively. Results showed that the leaf extract of O. thymiflorus and bacterial insecticide spinosad are promising as a good larvicidal and pupicidal against dengue vector, A. aegypti and malarial vector, A. stephensi. This is an ideal eco-friendly approach for the control of target species of vector control programs.     

Adulticidal properties of synthesized silver nanoparticles using leaf extracts of Feronia elephantum (Rutaceae) against filariasis,malaria, and dengue vector mosquitoes

Mosquito-borne diseases with an economic impact create loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Extracts from plants may be alternative sources of mosquito control agents because they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products and potentially suitable for use to control mosquitoes. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (8, 16, 24, 32, and 40 μg mL^?1) and aqueous leaf extract (40, 80, 120, 160, and 200 μg mL^?1) were tested against the adults of A. stephensi, A. aegypti, and C. quinquefasciatus. Adults were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy analysis (EDX), and transmission electron microscopy (TEM). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following lethal dose (LD)₅₀ and LD₉₀ values: A. stephensi had LD₅₀ and LD₉₀ values of 18.041 and 32.575 μg mL^?1; A. aegypti had LD₅₀ and LD₉₀ values of 20.399 and 37.534 μg mL^?1; and C. quinquefasciatus had LD₅₀ and LD₉₀ values of 21.798 and 39.596 μg mL^?1. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of F. elephantum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.     

Evaluation of larvicidal activity of Acalypha alnifolia Klein ex Willd. (Euphorbiaceae) leaf extract against the malarial vector, Anopheles stephensi, dengue vector, Aedes aegypti and Bancroftian filariasis vector, Culex quinquefasciatus (Diptera: Culicidae)

The leaf extract of Acalypha alnifolia with different solvents — hexane, chloroform, ethyl acetate, acetone and methanol — were tested for larvicidal activity against three important mosquitoes such as malarial vector, Anopheles stephensi, dengue vector, Aedes aegypti and Bancroftian filariasis vector, Culex quinquefasciatus. The medicinal plants were collected from the area around Kallar Hills near the Western Ghats, Coimbatore, India. A. alnifolia plant was washed with tap water and shade dried at room temperature. The dried leaves were powdered mechanically using commercial electrical stainless steel blender. The powder 800 g of the leaf material was extract with 2.5 litre of various each organic solvents such as hexane, chloroform, ethyl acetate, acetone, methanol for 8 h using Soxhlet apparatus, and filtered. The crude plant extracts were evaporated to dryness in a rotary vacuum evaporator. The yield of extracts was hexane (8.64 g), chloroform (10.74 g), ethyl acetate (9.14 g), acetone (10.02 g), and methanol (11.43 g). One gram of the each plant residue was dissolved separately in 100 ml of acetone (stock solution) from which different concentrations, i.e., 50, 150, 250, 350 and 450 ppm, was prepared. The hexane, chloroform, ethyl acetate, acetone was moderate considerable mortality; however, the highest larval mortality was methanolic extract observed in three mosquito vectors. The larval mortality was observed after 24 h exposure. No mortality was observed in the control. The early fourth-instar larvae of A. stephensi had values of LC₅₀ = 197.37, 178.75, 164.34, 149.90 and 125.73 ppm and LC₉₀ = 477.60, 459.21, 435.07, 416.20 and 395.50 ppm, respectively. The A. aegypti had values of LC₅₀ = 202.15, 182.58, 160.35, 146.07 and 128.55 ppm and LC₉₀ = 476.57, 460.83, 440.78, 415.38 and 381.67 ppm, respectively. The C. quinquefasciatus had values of LC₅₀ = 198.79, 172.48, 151.06, 140.69 and 127.98 ppm and LC₉₀ = 458.73, 430.66, 418.78, 408.83 and 386.26 ppm, respectively. The results of the leaf extract of A. alnifloia are promising as good larvicidal activity against the mosquito vector, A. stephensi, A. aegypti, C. quinquefasciatus. Therefore, this study provides first report on the larvicidal activities against three species of mosquito vectors of this plant extracts from Southern India.     

Silver nanoparticles: a possibility for malarial and filarial vector control technology

Green synthesis technology is one of the rapid, reliable and best routes for the synthesis of silver nanoparticles (AgNPs). There are bioactive compounds with enormous potential in Azadirachta indica (Neem). The extraordinary mosquitoes warrant nanotechnology to integrate with novel molecules. This will be sustainable technology for future. Here, we synthesized AgNPs using aqueous extracts of leaves and bark of Az. indica (Neem). We tested AgNPs as larvicides, pupicides and adulticides against the malaria vector Anopheles stephensi and filariasis vector Culex quinquefasciatus. The results were obtained using UV-visible spectrophotometer and the images were recorded with a transmission electron microscope (TEM). The efficacy tests were then performed at different concentrations varying many hours by probit analysis. The synthesized AgNPs were spherical in shape and with varied sizes (10.47-nm leaf and 19.22-nm bark). The larvae, pupae and adults of filariasis vector C. quinquefasciatus were found to be more susceptible to our AgNPs than the malaria vector An. stephensi. The first and the second instar larvae of C. quinquefasciatus show a mortality rate of 100 % after 30 min of exposure. The results against the pupa of C. quinquefasciatus were recorded as LC₅₀ 4 ppm, LC₉₀ 11 ppm and LC₉₉ 13 ppm after 3 h of exposure. In the case of adult mosquitoes, LC₅₀ 1.06 μL/cm², LC₉₀ 2.13 μL/cm² and LC₉₉ 2.4 μL/cm² were obtained after 4 h of exposure. These results suggest that our AgNPs are environment-friendly for controlling malarial and filarial vectors.     

Larvicidal activity of isolated compound 5-(2,4-dimethylbenzyl) pyrrolidin-2-one from marine Streptomyces VITSVK5 sp. against Rhipicephalus (Boophilus) microplus, Anopheles stephensi, and Culex tritaeniorhynchus

The aim of the present study was to assess the larvicidal property of marine actinobacterial compound 5-(2,4-dimethylbenzyl) pyrrolidin-2-one (DMBPO) extracted and isolated from Streptomyces VITSVK5 sp. tested against the larvae of Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae), Anopheles stephensi Liston, and Culex tritaeniorhynchus Giles (Diptera: Culicidae). The isolate bacteria was taxonomically characterized, identified, and designated as Streptomyces VITSVK5 sp. The crude extract was loaded on silica gel column and eluted with chloroform:methanol. The isolated pure compound was analyzed by thin layer chromatography using chloroform and methanol as the solvent system and confirmed by high-performance liquid chromatography. The structure of the purified compound was established from infrared, ultraviolet, ¹H-nuclear magnetic resonance (NMR), ¹³C-NMR, and mass spectral data. The chemical shift assignments obtained for the aliphatic compound from ¹H-NMR corresponding to the molecular formula C₁₃H₁₇NO. Bioassay-guided fractionation led to the isolation of compound which was identified as DMBPO. In the present study, Streptomyces VITSVK5 sp. crude extract and different fractions were tested against the larvae of parasites at the concentration of 1,000 ppm. Those fractions showing 100% mortality in 24 h alone was selected for further column chromatographic separation. The purified compound, C₁₃H₁₇NO, was tested in the concentrations of 500, 250, 125, 62.5, and 31.25 ppm and observed the percent larval mortality of 100, 70, 64, 40, and 28 against R. microplus; 100, 79, 63, 36, and 22 against A. stephensi; and 100, 84, 67, 42, and 27 against C. tritaeniorhynchus, respectively. The crude extract showed parasitic effects after 24 h of exposure at 1,000 ppm, and parasite mortality was observed against the larvae of R. microplus (LC₅₀?=?210.39 ppm, r ²?=?0.873); A. stephensi (LC₅₀?=?169.38 ppm, r ²?=?0.840); and C. tritaeniorhynchus (LC₅₀?=?198.75 ppm, r ²?=?0.887). The maximum efficacy was observed in purified marine actinobacterial compound DMBPO with LC₅₀ and r ² values against the larvae of R. microplus (84.31 ppm, 0.889); A. stephensi (88.97 ppm, 0.817), and C. tritaeniorhynchus (74.95 ppm, 0.781), respectively. The control (distilled water) showed nil mortality in the concurrent assay.     

Larvicidal activity of <Emphasis Type="Italic">Saraca indica,Nyctanthes arbor-tristis</Emphasis>, and <Emphasis Type="Italic">Clitoria ternatea</Emphasis> extracts against three mosquito vector species

Screening of natural products for mosquito larvicidal activity against three major mosquito vectors Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi resulted in the identification of three potential plant extracts viz., Saraca indica/asoca, Nyctanthes arbor-tristis, and Clitoria ternatea for mosquito larval control. In the case of S. indica/asoca, the petroleum ether extract of the leaves and the chloroform extract of the bark were effective against the larvae of C. quinquefasciatus with respective LC₅₀ values 228.9 and 291.5 ppm. The LC₅₀ values of chloroform extract of N. arbor-tristis leaves were 303.2, 518.2, and 420.2 ppm against A. aegypti, A. stephensi, and C. quinquefasciatus, respectively. The methanol and chloroform extracts of flowers of N. arbor-tristis showed larvicidal activity against larvae of A. stephensi with the respective LC₅₀ values of 244.4 and 747.7 ppm. Among the methanol extracts of C. ternatea leaves, roots, flowers, and seeds, the seed extract was effective against the larvae of all the three species with LC₅₀ values 65.2, 154.5, and 54.4 ppm, respectively, for A. stephensi, A. aegypti, and C. quinquefasciatus. Among the three plant species studied for mosquito larvicidal activity, C. ternatea was showing the most promising mosquito larvicidal activity. The phytochemical analysis of the promising methanolic extract of the seed extract was positive for carbohydrates, saponins, terpenoids, tannins, and proteins. In conclusion, bioassay-guided fractionation of effective extracts may result in identification of a useful molecule for the control of mosquito vectors.     

Mosquito larvicidal, pupicidal, adulticidal, and repellent activity of Artemisia nilagirica (Family: Compositae) against Anopheles stephensi and Aedes aegypti

Mosquito-borne diseases have an economic impact, including loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates; however, no part of the world is free from vector-borne diseases. The aim of the present study, to evaluate the larvicidal, pupicidal, repellent, and adulticidal activities of methanol crude extract of Artemisia nilagirica were assayed for their toxicity against two important vector mosquitoes, viz., Anopheles stephensi and Aedes aegypti (Diptera: Culicidae). The fresh leaves of A. nilagirica were washed thoroughly in tap water and shade dried at room temperature (28?±?2?°C) for 5?C8?days. The air-dried materials were powdered separately using commercial electrical blender. From the plants, 500?g powdered was macerated with 1.5?L organic solvents of methanol sequentially for a period of 72?h each and filtered. The larval and pupal mortality was observed after 24?h of exposure; no mortality was observed in the control group. The first- to fourth-instar larvae and pupae of A. stephensi had values of LC₅₀?=?272.50, 311.40, 361.51, 442.51, and 477.23?ppm, and the LC₉₀?=?590.07, 688.81, 789.34, 901.59, and 959.30?ppm; the A. aegypti had values of LC₅₀?=?300.84, 338.79, 394.69, 470.74, and 542.11?ppm, and the LC₉₀?=?646.67, 726.07, 805.49, 892.01, and 991.29?ppm, respectively. The results of the repellent activity of plant extract of A. nilagirica plants at five different concentrations of 50, 150, 250, 350, and 450?ppm were applied on skin of fore arm in man and exposed against adult female mosquitoes. In this observation, the plant crude extract gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. The adult mortality was found in methanol extract of A. nilagirica, with the LC₅₀ and LC₉₀ values of 205.78 and 459.51?ppm for A. stephensi, and 242.52 and 523.73?ppm for A. aegypti, respectively. This result suggests that the leaf extract have the potential to be used as an ideal eco-friendly approach for the control of vector mosquito as target species.     

Identification and characterization of a novel marine Bacillus cereus for mosquito control

Entomopathogenic bacteria to control mosquitoes are a promising environmentally friendly alternative to synthetic pesticides. In the present study, a novel mosquitocidal bacterium was isolated from marine soil collected from east coastal areas at Pondicherry (India). 16S rRNA gene sequence alignment depicted that this isolate belonged to Bacillus cereus VCRC-B520 (NCBI: KC-119192). Biochemical studies on bacterial growth, biomass, and toxin production have revealed that this strain could possibly be helpful in the production of a biopesticide in mosquito control. Toxicity assay with B. cereus against mosquito larvae has shown that the filariasis vector, Culex quinquefasciatus, is more susceptible than the other two species (Anopheles stephensi and Aedes aegypti). The LC₅₀ and LC₉₀ values for C. quinquefasciatus were 0.30 and 2.21 mg/L, respectively. No effect of B. cereus was found on nontargeted organisms. SDS-PAGE analysis and protein purification result from the cell mass of B. cereus have shown that a well-perceptible polypeptide was the dependable factor (85 kDa) for mosquitocidal action. Protein characterization (M/S MALDI-TOF) has shown that it is an endotoxin-specific insecticidal protein, namely “Cry4Aa”. Phylogenetic analyses of 16S rDNA gene sequence from this marine isolate have revealed the presence of homology among closely related Bacillus strains. Therefore, considerable interest has been shown on the identification of a potential mosquitocidal bacterium from marine environment (B. cereus), which was not reported earlier in view of the current scenario of the rapid development of resistance to Bacillus sphaericus in mosquito vector control program.     

Larvicidal, oviposition, and ovicidal effects of Artemisia annua (Asterales: Asteraceae) against Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus (Diptera: Culicidae)

This study focuses on the larvicidal, oviposition, and ovicidal effects of a crude extract of Artemisia annua against Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus. Dried cells of Artemisia annua from cell suspension cultures were extracted using hexane. The extract showed moderate larvicidal effects against mosquitoes. At 24-h post treatment, the LC₅₀ values for Anopheles sinensis, Aedes aegypti, and Culex quinquefasciatus were recorded as 244.55, 276.14, and 374.99 ppm, respectively. The percentage mortality of larvae was directly proportional to the tested concentration. Anopheles sinensis was found to be the most susceptible species, whereas Culex quinquefasciatus was the most tolerant to the Artemisia annua extract. The results indicated that the Artemisia annua extract showed concentration-dependent oviposition deterrent activity and had a strong deterrent effect. At 500 ppm, the percentage effective repellency was more than 85 % compared with the control group for all the species, with oviposition activity index values of ?0.94, ?0.95, and ?0.78 for Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus, respectively. In the ovicidal assay, the percentage hatchability of eggs after treatment with 500 ppm of Artemisia annua extract was significantly lower than the control, with values of 48.84?±?4.08, 38.42?±?3.67, and 79.35?±?2.09 % for Aedes aegypti, Anopheles sinensis, and Culex quinquefasciatus, respectively. Artemisia annua was found to be more effective against Aedes aegypti and Anopheles sinensis compared with Culex quinquefasciatus. This study indicated that crude extract of A. annua could be a potential alternative for use in vector management programs.     

Mosquito larvicidal, ovicidal, and repellent properties of botanical extracts against Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus (Diptera: Culicidae)

Mosquito-borne diseases have an economic impact, including loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates; however, no part of the world is free from vector-borne diseases. In mosquito control programs, botanical origin may have the potential to be used successfully as eggs, larvae, and adult. The larvicidal, ovicidal, and repellent activities of crude benzene and ethyl acetate extracts of leaf of Ervatamia coronaria and Caesalpinia pulcherrima were assayed for their toxicity against three important vector mosquitoes, viz., Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in benzene extract of E. coronaria against the larvae of Anopheles Stephensi, Aedes aegypti, and Culex quinquefasciatus with the LC₅₀ and LC₉₀ values were 79.08, 89.59, and 96.15 ppm and 150.47, 166.04, and 174.10 ppm, respectively. Mean percent hatchability of the ovicidal activity was observed 48 h posttreatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. The leaf extract of E. coronaria was found to be most effective than Caesalpinia pulcherrima against eggs/egg rafts of three vector mosquitoes. For E. coronaria, the benzene extract exerted 300, 250, and 200 ppm against Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus, respectively. The results of the repellent activity of benzene and ethyl acetate extract of E. coronaria and Caesalpinia pulcherrima plants at three different concentrations of 1.0, 2.5, and 5.0 mg/cm² were applied on skin of fore arm in man and exposed against adult female mosquitoes. In this observation, these two plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal ecofriendly approach for the control of mosquitoes. This is the first report on the mosquito larvicidal, ovicidal, and repellent activities of the reported E. coronaria and Caesalpinia pulcherrima plants.