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.     

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.     

Insecticidal potency of bacterial species Bacillus thuringiensis SV2 and Serratia nematodiphila SV6 against larvae of mosquito species Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus

The tremendous worldwide efforts to isolate novel mosquito larvicidal bacteria with improved efficacy present significant promise to control vector-borne diseases of public health importance. In the present study, two native bacterial isolates, Bacillus thuringiensis (Bt SV2) and Serratia species (SV6) were evaluated for mosquito larvicidal potential against the early fourth instar larvae of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus with reference to B. thuringiensis subsp. israelensis (Bti) H 14. The native Gram-positive, spore-forming Bt SV2 isolate showed 100% mortality against early fourth instars of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus, in parallel to Bti H14 strain. After 24 h, Bt SV2 showed 98%, 89%, and 80.67%, and Bti H14 showed 92%, 98.33%, and 60% mortality against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus, respectively. Serratia SV6 showed highest activity against Culex quinquefasciatus (100%) followed by Anopheles stephensi (95%) and Aedes aegypti (91%) after 48 h of exposure. The Gram-negative Serratia SV6 showed delayed toxicity compared to Bti H14 and Bt SV2 against early fourth instars of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. The relative mortality of all treatments after 12-h exposures showed the varied toxicity with respect to exposure time, bacterial treatment, and mosquito species. Genetic relatedness of the strains was confirmed on the basis of phylogenetic reconstructions based on alignment of 16S rRNA gene sequences which indicated a strong clustering of the strain SV2 with B. thuringiensis and the strain SV6 with Serratia nematodiphila. In conclusion, the native isolate B. thuringiensis SV2 showed significant toxicity while Serratia SV6 showed less and delayed toxicity against several mosquito species compared with BtiH14. They may be used as novel bacterial insecticidal agents in mosquito vector-borne disease control. To our knowledge, this is the first report on mosquito larvicidal potential of Serratia species.     

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.     

Green synthesis of silver nanoparticles using Murraya koenigii leaf extract against Anopheles stephensi and Aedes aegypti

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 activity of silver nanoparticles (AgNPs) synthesized using Murraya koenigii plant leaf extract against first to fourth instars larvae and pupae of Anopheles stephensi and Aedes aegypti was determined. Range of concentrations of synthesized AgNPs (5, 10, 20, 30, and 40 ppm) and ethanol leaf extract (50, 200, 350, 500, and 650 ppm) were tested against the larvae of A. stephensi and A. aegypti. The synthesized AgNPs from M. koenigii leaf were highly toxic than crude leaf ethanol extract in both mosquito species. The results were recorded from UV–Vis spectrum, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analysis. Larvae were exposed to varying concentrations of aqueous extract of synthesized AgNPs for 24 h. The maximum mortality was observed in synthesized AgNPs, and ethanol leaf extract of M. koenigii against A. stephensi had LC₅₀ values of 10.82, 14.67, 19.13, 24.35, and 32.09 ppm and 279.33, 334.61, 406.95, 536.11, and 700.16 ppm and LC₉₀ values of 32.38, 42.52, 53.65, 63.51, and 75.26 ppm and 737.37, 843.84, 907.67, 1,187.62, and 1,421.13 ppm. A. aegypti had LC₅₀ values of 13.34, 17.19, 22.03, 27.57, and 34.84 ppm and 314.29, 374.95, 461.01, 606.50, and 774.01 ppm and LC₉₀ values of 36.98, 47.67, 55.95, 67.36, and 77.72 ppm and 777.32, 891.16, 1,021.90, 1,273.06, and 1,509.18 ppm, respectively. These results suggest that the use of M. koenigii 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.     

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.     

Mosquitocidal properties of nereistoxin against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae)

Emergence of resistance among mosquitoes is a recent problem. Safe and eco-friendly agents from biological origins are the need of the hour. Nereistoxin, a naturally occurring substance, was first isolated from the marine annelid Lumbriconereis heteropoda and stored in the freezer. In the present study, the toxicity of nereistoxin was evaluated against vector mosquitoes. The larvicidal, ovicidal and adulticidal activities of nereistoxin were assayed for their toxicity against three important vector mosquitoes, viz., Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae). The nereistoxin was inversely proportional to the concentration and directly proportional to the mosquitoes. The larvicidal activity after 24 h LC₅₀ value was observed at 0.467, 0.535 and 0.601 ppm for A. stephensi, A. aegypti and C. quinquefasciatus, respectively. The ovicidal activity after 120 h zero percentage of egg hatchability was observed at a concentration of 0.8 ppm for A. stephensi and 1.0 ppm for A. aegypti and C. quinquefasciatus. The results of the adulticidal activity after 24 h LD₅₀ value were observed at 0.022, 0.028 and 0.034 ppm for A. stephensi, A. aegypti and C. quinquefasciatus, respectively. The extracted nereistoxin was characterized and identified by ultraviolet, infrared, nuclear magnetic resonance, mass spectroscopic methods and high pressure liquid chromatography. These results clearly reveal that the nereistoxin served as a potential larvicidal, ovicidal and adulticidal activity against vector mosquitoes.     

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.     

N-substituted methyl maleamates as larvicidal compounds against Aedes aegypti (Diptera: Culicidae)

Parasitology Research - Severe human arboviral diseases can be transmitted by the mosquito Aedes aegypti (L.), including dengue, chikungunya, zika, and yellow fever. The use of larvicides in...     

Larvicidal efficacy of the Citrus limetta peel extracts against Indian strains of Anopheles stephensi Liston and Aedes aegypti L.

The extracts from the peels of Citrus limetta were prepared using hexane and petroleum ether as the solvents. The larvicidal potential of each extract was assessed against dengue fever vector, Aedes aegypti, and malarial vector, Anopheles stephensi, by evaluating the toxicity effects on early fourth instars. Both the extracts were found effective against both the species. The bioassay with hexane extracts resulted in LC(50) values of 132.45 and 96.15 ppm against A. stephensi and A. aegypti, respectively; while the petroleum ether extracts from the C. limetta peels showed LC(50) values of 244.59 and 145.50 ppm, respectively. It revealed that the hexane extracts possessed 1.9-fold more larvicidal potential against A. stephensi and 1.5-fold more efficacy against A. aegypti as compared to the extracts obtained using petroleum ether as solvent. The data further revealed that the extracts were 1.4-1.7 times more effective against A. aegypti as compared to A. stephensi. The qualitative phytochemical study of the extracts showed the presence of terpenoids and flavonoids as the common phytochemical constituents in the extracts suggesting their possible role in the toxicity. Other constituents tested were not detected except alkaloids which were found to be present only in the petroleum ether extract. Further studies are needed to isolate and identify the active principles involved, their mode of action, formulated preparations for enhancing potency and stability, toxicity, and effects on non-target organisms and the environment. This could help in formulating efficient strategies for mosquito control.     

Strong larvicidal potential of Artemisia annua leaf extract against malaria (Anopheles stephensi Liston) and dengue (Aedes aegypti L.) vectors and bioassay-driven isolation of the marker compounds

Malaria and dengue are the two most important vector-borne human diseases caused by mosquito vectors Anopheles stephensi and Aedes aegypti, respectively. Of the various strategies adopted for eliminating these diseases, controlling of vectors through herbs has been reckoned as one of the important measures for preventing their resurgence. Artemisia annua leaf chloroform extract when tried against larvae of A. stephensi and A. aegypti has shown a strong larvicidal activity against both of these vectors, their respective LC50 and LC90 values being 0.84 and 4.91 ppm for A. stephensi and 0.67 and 5.84 ppm for A. aegypti. The crude extract when separated through column chromatography using petroleum ether-ethyl acetate gradient (0–100 %) yielded 76 fractions which were pooled into three different active fractions A, B and C on the basis of same or nearly similar R _f values. The aforesaid pooled fractions when assayed against the larvae of A. stephensi too reported a strong larvicidal activity. The respective marker compound purified from the individual fractions A, B and C, were Artemisinin, Arteannuin B and Artemisinic acid, as confirmed and characterized through FT-IR and NMR. This is our first report of strong mortality of A. annua leaf chloroform extract against vectors of two deadly diseases. This technology can be scaled up for commercial exploitation.     

Chemical composition and larvicidal activity of the essential oil of Plectranthus amboinicus (Lour.) Spreng against Anopheles stephensi: a malarial vector mosquito

Essential oil of Plectranthus amboinicus was studied for its chemical composition and larvicidal potential against the malarial vector mosquito Anopheles stephensi. Totally 26 compounds were identified by GC and GC-MS. The major chemical compounds were carvacrol (28.65%) followed by thymol (21.66%), α-humulene (9.67%), undecanal (8.29%), γ-terpinene (7.76%), ρ-cymene (6.46%), caryophyllene oxide (5.85%), α-terpineol (3.28%) and β-selinene (2.01%). The larvicidal assay was conducted to record the LC₅₀ and LC₉₀ values and the larval mortality was observed after 12 and 24 h of exposure period. The LC₅₀ values of the oil were 33.54 (after 12 h) and 28.37 ppm (after 24 h). The LC₉₀ values of the oil were 70.27 (after 12 h) and 59.38 ppm (after 24 h). The results of the present study showed that the essential oil of P. amboinicus is one of the inexpensive and eco-friendly sources of natural mosquito larvicidal agent to control/reduce the population of malarial vector mosquito.     

Larvicidal activity of silver nanoparticles synthesized using Pergularia daemia plant latex against Aedes aegypti and Anopheles stephensi and nontarget fish Poecillia reticulata

In present study, the bioactivity of latex-producing plant Pergularia daemia as well as synthesized silver nanoparticles (AgNPs) against the larval instars of Aedes aegypti and Anopheles stephensi mosquito larvae was determined. The range of concentrations of plant latex (1,000, 500, 250, 125, 62.25, and 31.25 ppm) and AgNPs (10, 5, 2.5, 1.25, 0.625, and 0.3125 ppm) were prepared. The LC(50) and LC(90) values for first, second, third, and fourth instars of synthesized AgNPs-treated first, second, third, and fourth instars of A. aegypti (LC(50)?=?4.39, 5.12, 5.66, 6.18; LC(90)?=?9.90, 11.13, 12.40, 12.95 ppm) and A. stephensi (LC(50)?=?4.41, 5.35, 5.91, 6.47; LC(90)?=?10.10, 12.04, 13.05, 14.08 ppm) were found many fold lower than crude latex-treated A. aegypti (LC(50)?=?55.13, 58.81, 75.66, 94.31; LC(90)?=?113.00, 118.25, 156.95, 175.71 ppm) and A. stephensi (LC(50)?=?81.47, 92.09, 96.07, 101.31; LC(90)?=?159.51, 175.97, 180.67, 190.42 ppm). The AgNPs did not exhibit any noticeable effects on Poecillia reticulata after either 24 or 48 h of exposure at their LC(50) and LC(90) values against fourth-instar larvae of A. aegypti and A. stephensi. The UV-visible analysis shows absorbance for AgNPs at 520 nm. TEM reveals spherical shape of synthesized AgNPs. Particle size analysis revealed that the size of particles ranges from 44 to 255 nm with average size of 123.50 nm. AgNPs were clearly negatively charged (zeta potential -27.4 mV). This is the first report on mosquito larvicidal activity P. daemia-synthesized AgNPs.