Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), 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 non target 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 non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Plant extracts as potential mosquito larvicides

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.

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

Low-cost and eco-friendly phyto-synthesis of silver nanoparticles using Cocos nucifera coir extract and its larvicidal activity

Larvicidal activity of synthesized silver nanoparticles using Eclipta prostrata leaf extract against filariasis and malaria vectors

Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. The present study was based on assessments of the antiparasitic activities to determine the efficacies of synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Mimosa pudica Gaertn (Mimosaceae) against the larvae of malaria vector, Anopheles subpictus Grassi, filariasis vector Culex quinquefasciatus Say (Diptera: Culicidae), and Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae). Parasite larvae were exposed to varying concentrations of aqueous extract of M. pudica and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of M. pudica 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 larvae of A. subpictus, C. quinquefasciatus, and R. microplus (LC50 = 13.90, 11.73, and 8.98 mg/L, r2 = 0.411, 0.286, and 0.479), respectively. This is the first report on antiparasitic activity of the plant extract and synthesized AgNPs.

Evaluation of green synthesized silver nanoparticles against parasites

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.

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

This study investigates the larvicidal potential of indigenous plant extracts from commonly used medicinal herbs as an environmentally safe measure to control the filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae). The early fourth-instar larvae of C. quinquefasciatus, reared in the laboratory, were used for larvicidal assay with water, hot water, acetone, chloroform, and methanol leaf, stem-bark, and flower extracts of Acacia arabica Willd. Sans, Cedrus deodara Roxb, Hibiscus rosa-sinensis L., Mangifera indica L., Nerium indicum Mill., Nicotiana tabacum Linn., Pongamia pinnata (L.) Pierre, and Solanum nigrum Linn. All plant extracts showed moderate larvicidal effects after 24 h of exposure at 1,000 ppm; however, the highest larval mortality was found in stem-bark hot water, acetone, and methanol extracts of C. deodara (LC50 = 133.85, 141.60, and 95.19 ppm, LC90 = 583.14, 624.19, and 639.99 ppm) and leaf hot water, acetone, methanol, and chloroform extracts of N. tabacum (LC50 = 76.27, 163.81, 83.38, and 105.85 ppm, LC90 = 334.72, 627.38, 709.51, and 524.39 ppm) against the larvae of C. quinquefasciatus, respectively. This is an ideal ecofriendly approach for the control of lymphatic filariasis vector, C. quinquefasciatus.

Evaluation of indigenous plant extracts against larvae of Culex quinquefasciatus Say (Diptera: Culicidae).

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.

Evaluation of larvicidal and nymphicidal potential of plant extracts against Anopheles subpictus Grassi, Culex tritaeniorhynchus Giles and Aphis gossypii Glover.

G. Pandiyan

Papers

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

Evaluation of indigenous plant extracts against larvae of Culex quinquefasciatus Say (Diptera: Culicidae).

Evaluation of larvicidal and nymphicidal potential of plant extracts against Anopheles subpictus Grassi, Culex tritaeniorhynchus Giles and Aphis gossypii Glover.