Efficacy of larvicidal botanical extracts against <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> Say (Diptera: Culicidae)

The present study explored the effects of crude leaf acetone, chloroform, hot water, methanol, petroleum ether (60–80°C), and water extracts of Calotropis procera (Ait) R. Br., Canna indica L., Hibiscus rosa-sinensis Linn., Ipomoea carnea Jacq. spp. fistulosa Choisy, and Sarcostemma brevistigma Wight that were selected for investigating larvicidal potential against second and fourth instar larvae of the laboratory-reared mosquito species, Culex quinquefasciatus Say, in which the major lymphatic filariasis was used. All plant extracts showed moderate larvicidal effects after 24 h of exposure at 1,000 ppm; however, the highest larval mortality was found in leaf acetone, chloroform, methanol, and petroleum ether of C. indica (LC₅₀ = 29.62, 59.18, 40.77, and 44.38 ppm; LC₉₀ = 148.55, 267.87, 165.00, and 171.91 ppm) against second instar larvae (LC₅₀ = 121.88, 118.25, 69.76, and 56.31 ppm; LC₉₀ = 624.35, 573.93, 304.27, and 248.24 ppm) and against fourth instar larvae and acetone, hot water, methanol, and petroleum ether extracts of I. carnea (LC₅₀ = 61.17, 41.07, 41.82, and 39.32 ppm; LC₉₀ = 252.91, 142.67, 423.76, and 176.39 ppm) against second instar larvae (LC₅₀ = 145.37, 58.00, 163.81, and 41.75 ppm; LC₉₀ = 573.30, 181.10, 627.38, and 162.63 ppm) and against fourth instar larvae of C. quinquefasciatus, respectively. These results suggest that the acetone, methanol extracts of C. indica and hot water, petroleum ether extracts of I. carnea have the potential to be used as an ideal eco-friendly approach for the control of the major lymphatic filariasis vector, C. quinquefasciatus.     

Differential larvicidal efficacy of four species of <Emphasis Type="Italic">Vitex</Emphasis> against <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> larvae

The early fourth instar larvae of Culex quinquefasciatus, reared in the laboratory were used for larvicidal assay with leaf extracts of Vitex negundo, Vitex trifolia, Vitex peduncularis and Vitex altissima. The methanol extracts of the four species possessed varying levels of larvicidal nature. The highest larvicidal activity was found with the extract of V. trifolia (LC₅₀ = 41.41 ppm) followed by V. peduncularis (LC₅₀ = 76.28 ppm), V. altissima (LC₅₀ = 128.04 ppm) and V. negundo (LC₅₀ = 212.57 ppm).     

Synthesis of silver nanoparticles using Nelumbo nucifera leaf extract and its larvicidal activity against malaria and filariasis vectors

The aim of this study was to investigate the larvicidal potential of the hexane, chloroform, ethyl acetate, acetone, methanol, and aqueous leaf extracts of Nelumbo nucifera Gaertn. (Nymphaeaceae) and synthesized silver nanoparticles using aqueous leaf extract against fourth instar larvae of Anopheles subpictus Grassi and Culex quinquefasciatus Say (Diptera: Culicidae). Nanoparticles are being used in many commercial applications. It was found that aqueous silver ions can be reduced by aqueous extract of plant parts to generate extremely stable silver nanoparticles in water. The results recorded from UV–vis spectrum, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared support the biosynthesis and characterization of silver nanoparticles. Larvae were exposed to varying concentrations of plant extracts and synthesized silver nanoparticles for 24 h. All extracts showed moderate larvicidal effects; however, the maximum efficacy was observed in crude methanol, aqueous, and synthesized silver nanoparticles against the larvae of A. subpictus (LC₅₀ = 8.89, 11.82, and 0.69 ppm; LC₉₀ = 28.65, 36.06, and 2.15 ppm) and against the larvae of C. quinquefasciatus (LC₅₀ = 9.51, 13.65, and 1.10 ppm; LC₉₀ = 28.13, 35.83, and 3.59 ppm), respectively. These results suggest that the leaf methanol, aqueous extracts of N. nucifera, and green synthesis of silver nanoparticles have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

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.     

Laboratory study on larvicidal activity of indigenous plant extracts against <Emphasis Type="Italic">Anopheles subpictus</Emphasis> and <Emphasis Type="Italic">Culex tritaeniorhynchus</Emphasis>

Anopheles subpictus and Culex tritaeniorhynchus 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 leaf acetone, chloroform, ethyl acetate, hexane, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees., Andrographis paniculata (Burm.f.) Wall. ex Nees., Cocculus hirsutus (L.) Diels, Eclipta prostrata L., and Tagetes erecta L. were tested against fourth-instar larvae of malaria vector, A. subpictus Grassi and Japanese encephalitis vector, C. tritaeniorhynchus Giles (Diptera: Culicidae). All plant extracts showed moderate larvicidal effects after 24 h of exposure at 1,000 ppm; however, the highest larval mortality was found in leaf ethyl acetate of A. marmelos, E. prostrata, hexane, methanol of A. paniculata and C. hirsutus against the larvae of A. subpictus (LC₅₀ = 167.00, 78.28, 67.24, 142.83 ppm; LC₉₀ = 588.31, 360.75, 371.91, and 830.01 ppm) and against the larvae of C. tritaeniorhynchus (LC₅₀ = 99.03, 119.89, 88.50, 105.19 ppm; LC₉₀ = 479.23, 564.85, 416.39, and 507.86 ppm), respectively. These results suggest that the leaf hexane extract of A. paniculata and ethyl acetate extract of E. prostrata have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. tritaeniorhynchus. Therefore, this study provides first report on the mosquito larvicidal activity of plant extracts against vectors from Southern India.     

Evaluation of larvicidal nature of fleshy fruit wall of Momordica charantia Linn. (family: cucurbitaceae) in the management of mosquitoes

In view of the recently increased interest in developing plant-based insecticides as an alternative to chemical insecticides, this study was undertaken to assess the larvicidal potential of the various fruit wall extracts of Momordica charantia (cucurbitaceae) against two species of mosquito vectors, Anophels stephensi and Culex quinquefasciatus. Among the extracts tested, petroleum ether (LC₅₀ = 27.60; 17.22 ppm and 41.36; 15.62 ppm) extract was found more effective than carbon tetrachloride (LC₅₀ = 49.58; 16.15 ppm and 80.61; 27.64 ppm) and methanol (LC₅₀ = 142.82; 95.98 ppm and 1,057.49; 579.93 ppm) extracts towards anopheline and culicine larvae after 24 and 48 h of exposure respectively. Thus, all fruit wall extracts of M. charantia are toxic to both the larval species. M. charantia may, therefore, act as an effective biolarvicide against mosquitoes in the future.     

Evaluation of medicinal plant extracts against blood-sucking parasites

The present study was based on assessments of the antiparasitic activities to determine the efficacies of acetone, chloroform, ethyl acetate, hexane, and methanol dried leaf, flower, and seed extracts of Cassia auriculata L., Rhinacanthus nasutus KURZ., Solanum torvum Swartz, Terminalia chebula Retz., and Vitex negundo Linn. were tested against larvae of cattle tick Rhipicephalus (Boophilus) microplus Canestrini, 1887 (Acari: Ixodidae), adult of Haemaphysalis bispinosa Neumann, 1897 (Acarina: Ixodidae), hematophagous fly Hippobosca maculata Leach (Diptera: Hippoboscidae), nymph of goat-lice Damalinia caprae Gurlt (Trichodectidae), and adult sheep parasite Paramphistomum cervi Zeder, 1790 (Digenea: Paramphistomatidae). All plant extracts showed moderate parasitic effects after 24 h of exposure at 3,000 ppm; however, the highest parasite mortality was found in leaf ethyl acetate, flower methanol of C. auriculata, leaf and seed methanol of S. torvum, seed acetone of T. chebula, and leaf hexane extracts of V. negundo against the larvae of R. microplus (LC₅₀ = 335.48, 309.21, 297.43, 414.99, 167.20, and 611.67 ppm; LC₉₀ = 1571.58, 1111.82, 950.98, 1243.64, 595.31, and 1875.50 ppm), the leaf and flower methanol of R. nasutus, leaf and seed methanol of S. torvum, and seed methanol extracts of T. chebula against the nymph of D. caprae (LC₅₀ = 119.26,143.10,164.93,140.47, and 155.98 ppm; LC₉₀ = 356.77, 224.08, 546.20, 479.72, and 496.06 ppm), the leaf methanol of R. nasutus, leaf and seed methanol of S.torvum, and seed acetone of T. chebula against the adult of H. bispinosa (LC₅₀ = 333.15, 328.98, 312.28, and 186.46 ppm; LC₉₀ = 1056.07, 955.39, 946.63, and 590.76 ppm), the leaf methanol of C. auriculata, the leaf and flower methanol of R. nasutus, the leaf ethyl acetate of S. torvum against the H. maculata (LC₅₀ = 303.36, 177.21, 204.58, and 211.41 ppm; LC₉₀ = 939.90, 539.39, 599.43, and 651.90 ppm), and the leaf acetone of C. auriculata, the flower methanol of R. nasutus, the seed methanol of S. torvum, and the seed acetone of T. chebula were tested against the adult of P. cervi (LC₅₀ = 180.54, 168.59, 200.89, and 87.08 ppm; LC₉₀ = 597.51, 558.65, 690.37, and 433.85 ppm), respectively. Therefore, this study provides first report on the veterinary parasitic activity of plant extracts from Southern India.     

Larvicidal efficacy of <Emphasis Type="Italic">Jatropha curcas</Emphasis> and bacterial insecticide, <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>, against lymphatic filarial vector<Emphasis Type="Italic">, Culex quinquefasciatus</Emphasis> Say (Diptera: Culicidae)

The present study explored the effects of Jatropha curcas leaf extract and Bacillus thuringiensis israelensis larvicidal activity against the lymphatic filarial vector, Culex quinquefasciatus. Wights were selected for investigating the larvicidal potential against the first to fourth instar larvae of the laboratory-reared mosquito species, C. quinquefasciatus Say, in which the major lymphatic filariasis was used. The medicinal plants were collected from the area around Bharathiar University, Coimbatore. The dried plant materials were powdered by an electric blender. From the powder, 100 g of the plant materials was extracted with 300 ml of organic solvents of methanol for 8 h, using a Soxhlet apparatus, and filtered. The crude plant extracts were evaporated to dryness in a rotary vacuum evaporator. The plant extract showed larvicidal effects after 24 h of exposure; however, the highest larval mortality was found in the leaf extract of methanol J. curcas against the first to fourth instar larvae of values LC₅₀ = 1.200%, 1.290%, 1.358%, and 1.448% and LC₉₀ = 2.094%, 2.323%, 2.444%, and 2.544% and B. thuringiensis israelensis against the first to fourth instar larvae of values LC₅₀ = 9.332%, 9.832%, 10.212%, 10.622% and LC₉₀ = 15.225%, 15.508%, 15.887%, and 15.986% larvae of C. quinquefasciatus, respectively. No mortality was observed in the control. These results suggest methanol extracts of J. curcas and B. thuringiensis israelensis have potential to be used as an ideal eco-friendly approach for the control of the major lymphatic filarial vector, C. quinquefasciatus.     

Insecticidal and larvicidal activities of medicinal plant extracts against mosquitoes

In recent years, use of environment friendly and biodegradable natural insecticides of plant origin have received renewed attention as agents for vector control because they are rich in bioactive chemicals, active against a limited number of species including specific target insects, and biodegradable. The present study was carried out to evaluate the adulticidal, repellent, and larvicidal activity of crude hexane, ethyl acetate, and methanol extracts of eight plants, viz. Aristolochia indica L., Cassia angustifolia Vahl, Diospyros melanoxylon Roxb., Dolichos biflorus L., Gymnema sylvestre (Retz) Schult, Justicia procumbens L., Mimosa pudica L., and Zingiber zerumbet L., were tested against adult and early fourth instar larvae of Culex gelidus Theobald and Culex quinquefasciatus Say (Diptera: Culicidae). The effective adult mortality was observed in methanol extract of A. indica, ethyl acetate extract of D. biflorus, and ethyl acetate and hexane extract of Z. zerumbet against C. gelidus and C. quinquefasciatus (LD₅₀ = 37.75, 78.56, 129.44, 86.13, 80.06, 112.42, 53.83, and 46.61; LD₉₀ = 166.83, 379.14, 521.50, 289.83, 328.18, 455.72, 181.15, and 354.50 ppm, respectively). Complete protections for 150 min were found in hexane and methanol extract of A. indica and Z. zerumbet at 1,000 ppm against mosquito bites. The highest larval mortality was found in the hexane extract of Z. zerumbet, ethyl acetate extract of D. biflorus, and methanol extracts of A. indica against C. gelidus (LC₅₀ = 26.48, 33.02, and 12.47 ppm; LC₉₀ = 127.73, 128.79, and 62.33 ppm) and against C. quinquefasciatus (LC₅₀ = 69.18, 34.76, and 25.60 ppm; LC₉₀ = 324.40, 172.78, and 105.52 ppm), respectively, after 24 h. The plant extracts are potential to be used as an ideal eco-friendly approach for the control of the Japanese encephalitis vector, C. gelidus, and lymphatic filariasis vector, C. quinquefasciatus.     

Mosquito larvicidal activity of oleic and linoleic acids isolated from Citrullus colocynthis (Linn.) Schrad

In mosquito control programs, botanical origin may have the potential to be used successfully as larvicides. The larvicidal activity of crude acetone, hexane, ethyl acetate, methanol, and petroleum ether extracts of the leaf of Centella asiatica Linn., Datura metal Linn., Mukia scabrella Arn., Toddalia asiatica (Linn.) Lam, extracts of whole plant of Citrullus colocynthis (Linn.) Schrad, and Sphaeranthus indicus Linn. were assayed for their toxicity against the early fourth instar larvae of Culex quinquefasciatus (Diptera: Culicidae). The larval mortality was observed after 24 h exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in whole plant petroleum ether extract of C. colocynthis. In the present study, bioassay-guided fractionation of petroleum ether extract led to the separation and identification of fatty acids; oleic acid and linoleic acid were isolated and identified as mosquito larvicidal compounds. Oleic and Linoleic acids were quite potent against fourth instar larvae of Aedes aegypti L. (LC₅₀ 8.80, 18.20 and LC₉₀ 35.39, 96.33 ppm), Anopheles stephensi Liston (LC₅₀ 9.79, 11.49 and LC₉₀ 37.42, 47.35 ppm), and Culex quinquefasciatus Say (LC₅₀ 7.66, 27.24 and LC₉₀ 30.71, 70.38 ppm). The structure was elucidated from infrared, ultraviolet, ¹H-nuclear magnetic resonance, ¹³C-NMR, and mass spectral data. This is the first report on the mosquito larvicidal activity of the reported isolated compounds from C. colocynthis.     

Larvicidal potential of medicinal plant extracts against Anopheles subpictus Grassi and Culex tritaeniorhynchus Giles (Diptera: Culicidae)

Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The acetone, chloroform, ethyl acetate, hexane, methanol and petroleum ether extracts of leaf, flower and seed of Cassia auriculata L., Leucas aspera (Willd.), Rhinacanthus nasutus KURZ., Solanum torvum Swartz and Vitex negundo Linn. were tested against fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest mortality was found in leaf petroleum ether, flower methanol extracts of C. auriculata, flower methanol extracts of L. aspera and R. nasutus, leaf and seed methanol extracts of S. torvum and leaf hexane extract of V. negundo against the larvae of A. subpictus (LC₅₀ = 44.21, 44.69, 53.16, 41.07, 35.32, 28.90 and 44.40 ppm; LC₉₀ = 187.31, 188.29, 233.18, 142.66, 151.60, 121.05 and 192.11 ppm, respectively) and against the larvae of C. tritaeniorhynchus (LC₅₀ = 69.83, 51.29, 81.24, 71.79, 44.42, 84.47 and 65.35 ppm; LC₉₀ = 335.26, 245.63, 300.45, 361.83, 185.09, 351.41 and 302.42 ppm, respectively). These results suggest that the leaf petroleum ether, flower methanol extracts of C. auriculata, leaf and seed methanol extracts of S. torvum and leaf hexane extract of V. negundo have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. tritaeniorhynchus. This is the first report on the mosquito larvicidal activity of the medicinal plant extracts.     

Screening for antifeedant and larvicidal activity of plant extracts against <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hübner), <Emphasis Type="Italic">Sylepta derogata</Emphasis> (F.) and <Emphasis Type="Italic">Anopheles stephensi</Emphasis> (Liston)

Plant extracts, especially botanical insecticides, are currently studied more and more because of the possibility of their use in plant protection. Biological activity of five solvent plant extracts were studied using fourth instar larvae of gram pod borer Helicoverpa armigera (Lepidoptera: Noctuidae), cotton leaf roller Sylepta derogata (Lepidoptera: Pyralidae) and malaria vector Anopheles stephensi (Diptera: Culicidae). Antifeedant and larvicidal activity of acetone, chloroform, ethyl acetate, hexane and methanol peel, leaf and flower extracts of Citrus sinensis, Ocimum canum, Ocimum sanctum and Rhinacanthus nasutus were used in this study. During preliminary screening, the extracts were tested at 1,000 ppm concentration. The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in peel chloroform extract of C. sinensis, flower methanol extract of O. canum against the larvae of H. armigera (LC₅₀ = 65.10,51.78, LC₉₀ = 277.39 and 218.18 ppm), peel methanol extract of C. sinensis, flower ethyl acetate extract of O. canum and leaf acetone extract of O. sanctum against the larvae of S. derogata (LC₅₀ = 20.27,58.21,36.66, LC₉₀ =113.15,285.70 and 668.02 ppm), peel methanol extract of C. sinensis, leaf and flower ethyl acetate extracts of O. canum against the larvae of A. stephensi (LC₅₀ = 95.74,101.53,28.96, LC₉₀ = 303.20,492.43 and 168.05 ppm), respectively. These results suggest that the chloroform and methanol extract of C. sinensis, ethyl acetate flower extracts of O. canum and acetone extract of O. sanctum have the potential to be used as an ideal eco-friendly approach for the control of the agricultural pests H. armigera, S. derogata and medically important vector A. stephensi.     

Larvicidal efficacy of five cucurbitaceous plant leaf extracts against mosquito species

Larvicidal activity of crude hexane, ethyl acetate, petroleum ether, acetone, and methanol extracts of the leaf of five species of cucurbitaceous plants, Citrullus colocynthis, Coccinia indica, Cucumis sativus, Momordica charantia, and Trichosanthes anguina, were tested against the early fourth instar larvae of Aedes aegypti L. and Culex quinquefasciatus (Say) (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 petroleum ether extract of C. colocynthis, methanol extracts of C. indica, C. sativus, M. charantia, and acetone extract of T. anguina against the larvae of A. aegypti (LC₅₀ = 74.57, 309.46, 492.73, 199.14, and 554.20 ppm) and against C. quinquefasciatus (LC₅₀ = 88.24, 377.69, 623.80, 207.61, and 842.34 ppm), respectively. The petroleum ether extract of C. colocynthis and methanol extract of M. charantia were more effective than the other extracts. This is an ideal eco-friendly approach for the control of the dengue vector, A. aegypti, and the lymphatic filariasis vector, C. quinquefasciatus.     

Mosquito larvicidal activities of Solanum nigrum L. leaf extract against Culex quinquefasciatus Say

The present study was carried out to establish the larvicidal activities of crude and solvent extracts of Solanum nigrum L. leaves against Culex quinquefasciatus Say as target species. The results indicated that the mortality rates at 0.5% concentration were highest amongst all concentrations of the crude extracts tested against all the larval instars at 24, 48 and 72 h of exposure. Result of log probit analysis (at 95% confidence level) revealed that lethal concentration LC₅₀ and LC₉₀ values gradually decreased with the exposure periods in bioassay experiment with the crude plant extract. The results of regression analysis of crude extract of S. nigrum revealed that the mortality rate is positively correlated with the concentration of the extracts. Mature leaves of S. nigrum were also extracted with six different solvents [viz. petroleum ether, benzene, ethyl acetate, chloroform: methanol (1:1 v/v), acetone and absolute alcohol] to determine the best extractant for subsequent isolation and characterization of active ingredient. Mortality rate with ethyl acetate extract was significantly higher (p < 0.05) than other extracts when 50-ppm doses were used. The corresponding LC₅₀ value of acetone, absolute alcohol, petroleum ether, chloroform: methanol (1:1 v/v), benzene and ethyl acetate extracts were 72.91 ppm, 59.81 ppm, 54.11 ppm, 32.69 ppm, 27.95 ppm and 17.04 ppm, respectively, after 24 h of exposure period. Results of this study show that the ethyl acetate extract of S. nigrum may be considered as a potent source of a mosquito larvicidal agent.     

Evaluation of larvicidal and nymphicidal potential of plant extracts against <Emphasis Type="Italic">Anopheles subpictus</Emphasis> Grassi, <Emphasis Type="Italic">Culex tritaeniorhynchus</Emphasis> Giles and <Emphasis Type="Italic">Aphis gossypii</Emphasis> Glover

The acetone, chloroform, ethyl acetate, hexane and methanol extracts of peel and leaf extracts of Citrus sinensis, Ocimum canum, Ocimum sanctum and Rhinacanthus nasutus were tested against fourth instar larvae of malaria vector, Anopheles subpictus Grassi, Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae) and feeding deterrence to nymphs of cotton pest, Aphis gossypii Glover (Homoptera: Aphididae). The larval and nymph mortality were observed after 24 h of exposure. All extracts showed moderate larvicidal and nymphicidal effects; however, the highest mortality was found in peel chloroform extract of C. sinensis, leaf ethyl acetate extracts of O. canum and O. sanctum and leaf chloroform extract of R. nasutus against the larvae of A. subpictus (LC₅₀ = 58.25, 88.15, 21.67 and 40.46 ppm; LC₉₀ = 298.31, 528.70, 98.34 and 267.20 ppm), peel methanol extract of C. sinensis, leaf methanol extract of O. canum, ethyl acetate extracts of O. sanctum and R. nasutus against the larvae of C. tritaeniorhynchus (LC₅₀ = 38.15, 72.40, 109.12 and 39.32 ppm; LC₉₀ = 184.67, 268.93, 646.62 and 176.39 ppm), peel hexane extract of C. sinensis, leaf methanol extracts of O. canum and R. nasutus and leaf ethyl acetate extract of O. sanctum against the nymph of A. gossypii (LC₅₀ = 162.89, 80.99, 73.27 and 130.19 ppm; LC₉₀ = 595.40, 293.33, 338.74 and 450.90 ppm), respectively. These results suggest that the peel methanol extracts of C. sinensis and O. canum, ethyl acetate leaf extract of O. sanctum and leaf chloroform and ethyl acetate extract of R. nasutus have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus, C. tritaeniorhynchus and A. gossypii.     

Efficacy of medicinal plant extracts against malarial vector, <Emphasis Type="Italic">Anopheles subpictus</Emphasis> Grassi

Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The aim of this study was to evaluate the adulticidal activity and adult emergence inhibition (EI) of leaf hexane, chloroform, ethyl acetate, acetone, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees., Andrographis paniculata (Burm.f.) Wall. ex Nees., Cocculus hirsutus L. Diels, Eclipta prostrata L., and Tagetes erecta L. tested against malarial vector, Anopheles subpictus Grassi (Diptera: Culicidae). All plant extracts showed moderate adulticidal activity and EI effects after 24 h of exposure at 1,000 ppm; however, the highest adulticidal activity was observed in ethyl acetate extract of A.lineata, chloroform extract of A.paniculata, acetone extract of C.hirsutus, and methanol extract of T.erecta (LD₅₀ = 126.92, 95.82, 109.40, and 89.83 ppm; LD₉₀ = 542.95, 720.82, 459.03, and 607.85 ppm); and effective EI was found in leaf acetone extract of the A. marmelos, ethyl acetate extract of A.lineata, methanol extracts of C. hirsutus, and T.erecta, (EI₅₀ = 128.14, 79.39, 143.97, and 92.82 ppm; EI₉₀ = 713.53, 293.70, 682.72, and 582.59 ppm), respectively, against A. subpictus. These results suggest that the leaf methanol extract of C. hirsutus and T.erecta have the potential to be used as an ideal eco-friendly approach for the control of A. subpictus. Therefore, this study provides first report on the mosquito adulticidal activity and EI of plant extracts against malaria vector.     

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.     

Laboratory determination of efficacy of indigenous plant extracts for parasites control

The present study was based on assessments of the antiparasitic activities to determine the efficacies of acetone, chloroform, ethyl acetate, hexane, and methanol dried leaf, flower, and seed extracts of Achyranthes aspera L., Anisomeles malabarica (L.) R. Br., Gloriosa superba L., Psidium guajava L., Ricinus communis L., and Solanum trilobatum L. tested against the larvae of cattle tick Rhipicephalus (Boophilus) microplus (Canestrini 1887) (Acari: Ixodidae), sheep internal parasite Paramphistomum cervi (Zeder 1790) (Digenea: Paramphistomatidae) at 2,000 ppm and fourth instar larvae of Anopheles subpictus Grassi and Culex tritaeniorhynchus Giles (Diptera: Culicidae) at 1,000 ppm. All plant extracts showed moderate effects after 24 h of exposure; however, the highest parasite mortality was found in the leaf ethyl acetate extract of A. aspera, leaf methanol extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis against the larvae of R. microplus (LC₅₀ = 265.33, 95.97, 153.73, and 181.49 ppm; LC₉₀ = 1,130.18, 393.88, 1,794.25, and 1,829.94 ppm); leaf acetone and chloroform of A. malabarica, flower acetone extract of G. superba, and leaf chloroform and methanol of R. communis against the adult of P. cervi (LC₅₀ = 108.07, 106.69, 157.61, 69.44, and 168.24 ppm; LC₉₀ = 521.77, 463.94, 747.02, 256.52, and 809.45 ppm); leaf ethyl acetate extract of A. aspera, leaf chloroform extract of A. malabarica, flower methanol of G. superba, and leaf methanol extract of R. communis against the larvae of A. subpictus (LC₅₀ = 48.83, 135.36, 106.77, and 102.71 ppm; LC₉₀ = 225.36, 527.24, 471.90, and 483.04 ppm); and leaf ethyl acetate extract of A. aspera, leaf chloroform extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis against the larvae of C. tritaeniorhynchus (LC₅₀ = 68.27, 95.98, 59.51, and 93.94 ppm; LC₉₀ = 306.88, 393.83, 278.99, and 413.27 ppm), respectively. These results suggest that the leaf ethyl acetate extract of A. aspera, leaf acetone and chloroform extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis have the potential to be used as an ideal eco-friendly approach for the control of the R. microplus, P. cervi, A. subpictus, and C. tritaeniorhynchus. Therefore, this study provides the first report on the larvae and adult parasitic activity of crude solvent extracts, indigenous plants consumed by the natives in southern India.     

Evaluation of botanical extracts against Haemaphysalis bispinosa Neumann and Hippobosca maculata Leach

In the current study, in vitro evaluation of crude hexane, chloroform, ethyl acetate, acetone, and methanol extracts of Anisomeles malabarica (L.) R. Br., Gloriosa superba L., Psidium guajava L., Ricinus communis L., and Solanum trilobatum L. exhibited acaricidal and insecticidal activities against the adult of Haemaphysalis bispinosa Neumann (Acarina: Ixodidae) and hematophagous fly Hippobosca maculata Leach (Diptera: Hippoboscidae). All plant extracts showed moderate toxic effect on parasites after 24 h of exposure; the complete inhibition (100%) at the maximum concentration tested (3,000 ppm) was obtained in acetone, methanol, hexane, and chloroform extracts of A. malabarica; methanol, chloroform, and ethyl acetate extracts of G. superba; acetone extract of P. guajava; methanol extract of R. communis; and leaf hexane extract of S. trilobatum; and the lowest inhibition (38%) was recorded for the seed hexane extract of S. trilobatum. The highest parasite dead was found in leaf acetone and methanol extracts of A. malabarica, seed methanol of G. superba, leaf methanol of R. communis against H. bispinosa (LC₅₀ = 466.15, 719.78, 476.06, and 243.87 ppm; LC₉₀ = 1,837.96, 2,014.47, 1,904.36, and 2,692.15 ppm), leaf hexane and chloroform extracts of A. malabarica, seed chloroform and ethyl acetate of G. superba, leaf acetone of P. guajava, leaf methanol of R. communis, and leaf hexane extract of S. trilobatum against H. maculata (LC₅₀ = 495.61, 414.81, 360.02, 479.37, 646.30, 506.13, and 432.77 ppm; LC₉₀ = 1,914.84, 1,956.59, 1,598.54, 1,636.41, 2,192.73, 1,982.66, and 1,872.33 ppm), respectively. These results suggest that the leaf methanol of R. communis, chloroform extracts of A. malabarica, and chloroform extract of G. superba have the potential to be used as an ideal eco-friendly approach for the control of the H. bispinosa and H. maculata. Therefore, this study provides first report on the parasitic activities of plant extracts from Southern India.     

Larvicidal, repellent, and ovicidal activity of marine actinobacteria extracts against Culex tritaeniorhynchus and Culex gelidus

The purpose of the present study was to assess the effect of crude extracts of marine actinobacteria on larvicidal, repellent, and ovicidal activities against Culex tritaeniorhynchus and Culex gelidus (Diptera: Culicidae). The early fourth instar larvae of C. tritaeniorhynchus and C. gelidus, reared in the laboratory, were used for larvicidal, ovicidal, and repellent assay with crude extracts of actinobacteria. Saccharomonospora spp. (LK-1), Streptomyces roseiscleroticus (LK-2), and Streptomyces gedanensis (LK-3) were identified as potential biocide producers. Based on the antimicrobial activity, three strains were chosen for larvicidal activity. The marine actinobacterial extracts showed moderate to high larvicidal effects after 24 h of exposure at 1,000 ppm and the highest larval mortality was found in extract of LK-3 (LC₅₀ = 108.08 ppm and LC₉₀ = 609.15 ppm) against the larvae of C. gelidus and (LC₅₀ = 146.24 ppm and LC₉₀ = 762.69 ppm) against the larvae of C. tritaeniorhynchus. Complete protections for 240 min were found in crude extract of LK-2 and LK-3 at 1,000 ppm, against mosquito bites of C. tritaeniorhynchus and C. gelidus, respectively. After 24-h treatment, mean percent hatchability of the ovicidal activity was observed. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Crude extracts of LK-1 and LK-3 showed no hatchability at 1,000 ppm against C. tritaeniorhynchus and C. gelidus, respectively. This is an ideal ecofriendly approach for the control of Japanese encephalitis vectors, C. tritaeniorhynchus and C. gelidus.