The insecticidal bio-efficacy of Lamiaceae essential oils (LEOs) and its major compounds (MCs) were tested against mosquitoes (Aedes vittatus and Anopheles maculates) and agricultural pests (Spodoptera litura and Helicoverpa armigera). The naturally gained LEOs were confirmed through GC-MS analysis. The larval and pupal toxicity of LEOs and their major compounds LC50/LC90 value was calculated by standard protocol. A total of 54, 47 and 31 compounds were identified from M. officinalis, L. latifolia and O. majorana, respectively. The MCs of LEOs: (M. officinalis) 2,6-Octadienal, 3,7-dimethyl-, (Z)-(29.4354%) and Caryophyllene (20.2749%); (L. latifolia) 1,6-Octadien-3-ol, 3,7-dimethyl-(34.4992%) and 1-Cyclohexyl-2-buten-1-ol (c,t) (38.0339%); (O. majorana) Eucalyptol (57.1278%) and p-menth-1-en-8-ol (17.9683%). The LEOs and their MCs were tested individually against larvae and pupae of Ae. vittatus, An. maculates, S. litura and H. armigera, which produced maximum toxic effects. Predominantly, the MCs were safer to the non-target organisms and target-specific insecticidal properties against selected insect pests. On the whole, our findings highlight that LEOs and their MCs represent promising eco-friendly and target specific insecticidal activities.

Eleven different carbohydrates were evaluated to determine the behavioral response of adult Anopheles quadrimaculatus Say and Aedes albopictus Skuse using an olfactometer. The carbohydrates used in the study are arabinose, fructose, glucose, maltose, melezitose, meliniose, raffinose, rhamnose, sucrose, trehalose, and turanose. The results showed that both species of mosquitoes regardless of the sex had significantly higher attraction to arabinose, maltose, meliniose, and trehalose than other 7 carbohydrates tested. Both sexes and both species responded to maltose and trehalose in considerable numbers, and the least responses were to sucrose except by male Ae. albopictus. These findings may provide insights to the development of more effective sugar-based toxic baits for the operational application in mosquito control programs.

Mosquito vectors are responsible for transmitting diseases such as malaria, dengue, chikungunya, Japanese encephalitis, dengue, and lymphatic filariasis. The use of synthetic insecticides to control mosquito vectors has caused physiological resistance and adverse environmental effects, in addition to high operational cost. Biosynthesis of silver nanoparticles has been proposed as an alternative to traditional control tools. In the present study, green synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Bauhinia variegata by reduction of Ag(+) ions from silver nitrate solution has been investigated. The bioreduced silver nanoparticles were characterized by UV–visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), and X-ray diffraction analysis (XRD). Leaf extract and synthesized AgNPs were evaluated against the larvae of Anopheles subpictus, Aedes albopictus, and Culex tritaeniorhynchus. Compared to aqueous extract, synthesized AgNPs showed higher toxicity against An. subpictus, Ae. albopictus, and Cx. tritaeniorhynchus with LC50 and LC90 values of 41.96, 46.16, and 51.92 μg/mL and 82.93, 89.42, and 97.12 μg/mL, respectively. Overall, this study proves that B. variegata is a potential bioresource for stable, reproducible nanoparticle synthesis and may be proposed as an efficient mosquito control agent.

Mosquitoes are vectors of devastating pathogens and parasites, causing millions of deaths every year. Dengue is a mosquito-borne viral infection found in tropical and subtropical regions around the world. Recently, transmission has strongly increased in urban and semiurban areas, becoming a major international public health concern. Aedes aegypti (Diptera: Culicidae) is the primary vector of dengue. The use of synthetic insecticides to control Aedes mosquitoes lead to high operational costs and adverse nontarget effects. In this scenario, eco-friendly control tools are a priority. We proposed a novel method to synthesize silver nanoparticles using the aqueous leaf extract of Phyllanthus niruri, a cheap and nontoxic material. The UV–vis spectrum of the aqueous medium containing silver nanostructures showed a peak at 420 nm corresponding to the surface plasmon resonance band of nanoparticles. SEM analyses of the synthesized nanoparticles showed a mean size of 30–60 nm. EDX spectrum showed the chemical composition of the synthesized nanoparticles. XRD highlighted that the nanoparticles are crystalline in nature with face-centered cubic geometry. Fourier transform infrared spectroscopy (FTIR) of nanoparticles exhibited prominent peaks 3,327.63, 2,125.87, 1,637.89, 644.35, 597.41, and 554.63 cm−1. In laboratory assays, the aqueous extract of P. niruri was toxic against larval instars (I–IV) and pupae of A. aegypti. LC50 was 158.24 ppm (I), 183.20 ppm (II), 210.53 ppm (III), 210.53 ppm (IV), and 358.08 ppm (pupae). P. niruri-synthesized nanoparticles were highly effective against A. aegypti, with LC50 of 3.90 ppm (I), 5.01 ppm (II), 6.2 ppm (III), 8.9 ppm (IV), and 13.04 ppm (pupae). In the field, the application of silver nanoparticles (10 × LC50) lead to A. aegypti larval reduction of 47.6 %, 76.7 % and 100 %, after 24, 48, and 72 h, while the P. niruri extract lead to 39.9 %, 69.2 % and 100 % of reduction, respectively. In adulticidal experiments, P. niruri extract and nanoparticles showed LC50 and LC90 of 174.14 and 6.68 ppm and 422.29 and 23.58 ppm, respectively. Overall, this study highlights that the possibility to employ P. niruri leaf extract and green-synthesized silver nanoparticles in mosquito control programs is concrete, since both are effective at lower doses if compared to synthetic products currently marketed, thus they could be an advantageous alternative to build newer and safer tools against dengue vectors.

The attraction of female Aedes aegypti to single compounds and binary compositions containing L-lactic acid and an additional saturated compound from a set of ketones, sulfides, and chloroalkanes was studied using a triple-cage dual-port olfactometer. These chemical classes were studied because of their structural relation to acetone, dimethyl disulfide, and dichloromethane, which have all been reported to synergize attraction to L-lactic acid. Human odors, carbon dioxide, and the binary mixture of L-lactic acid and CO₂served as controls for comparison of attraction responses produced by the binary mixtures. All tested mixtures that contained chloroalkanes attracted mosquitoes at synergistic levels, as did L-lactic acid and CO₂. Synergism was less frequent in mixtures of L-lactic acid with sulfides and ketones; in the case of ketones, synergistic attraction was observed only for L-lactic acid combined with acetone or butanone. Suppression or inhibition of attraction response was observed for combinations that contained ketones of C7-C12 molecular chain length (optimum in the C8-C10 range). This inhibition effect is similar to that observed previously for specific ranges of carboxylic acids, aldehydes, and alcohols.

Dengue is an arthropod-borne viral infection mainly vectored through the bite of Aedes mosquitoes. Recently, its transmission has strongly increased in urban and semi-urban areas of tropical and sub-tropical regions worldwide, becoming a major international public health concern. There is no specific treatment for dengue. Its prevention and control solely depends on effective vector control measures. In this study, we proposed the green-synthesis of silver nanoparticles (AgNP) as a novel and effective tool against the dengue serotype DEN-2 and its major vector Aedes aegypti. AgNP were synthesized using the Moringa oleifera seed extract as reducing and stabilizing agent. AgNP were characterized using a variety of biophysical methods including UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and sorted for size categories. AgNP showed in vitro antiviral activity against DEN-2 infecting vero cells. Viral titer was 7 log10 TCID50/ml in control (AgNP-free), while it dropped to 3.2 log10 TCID50/ml after a single treatment with 20 μl/ml of AgNP. After 6 h, DEN-2 yield was 5.8 log10 PFU/ml in the control, while it was 1.4 log10 PFU/ml post-treatment with AgNP (20 μl/ml). AgNP were highly effective against the dengue vector A. aegypti, with LC50 values ranging from 10.24 ppm (I instar larvae) to 21.17 ppm (pupae). Overall, this research highlighted the concrete potential of green-synthesized AgNP in the fight against dengue and its primary vector A. aegypti. Further research on structure–activity relationships of AgNP against other dengue serotypes is urgently required.

Malaria causes extensive morbidity and mortality in humans and results in significant economic losses in India. The distribution of immature malaria-transmitting Anopheles mosquitoes was studied in 17 villages in Coimbatore District as a prelude to the development and implementation of vector control strategies that are intended to reduce the risk of human exposure to potentially infectious mosquitoes. Eight Anopheles species were recorded. The most numerous species were Anopheles vagus, Anopheles subpictus, and Anopheles hyrcanus. The location of mosquito development sites and the density of larvae in each village was evaluated for correlation with selected demographic, biologic, and land use parameters using remote sensing and geographic information systems (GIS) technology. We found the number of mosquito development sites in a village and the density of larvae in such sites to be positively correlated with human population density but not the surface area (km(2)) of the village. The number of mosquito development sites and the density of larvae in each site were not correlated. Data from this study are being used to construct a GIS-based mapping system that will enable the location of aquatic habitats with Anopheles larvae in the Coimbatore District, Tamil Nadu, India as target sites for the application of vector control.

The methanolic extracts of Sida acuta and Vetiveria zizanioides leaves and root was investigated for antimalarial activity against Plasmodium berghei infections in mice. The median lethal dose was determined to ascertain the safety of the extract in mice. The antimalarial activities during early and established infections were evaluated. Phytochemical screening was also investigated to elucidate the possible mechanism of the antimalarial and antivectorial properties. The extracts of Sida acuta and Vetiveria zizanioides leaf and root demonstrated significant antiplasmodial activity in all the three groups (test for root and leaves and one control includes three groups) of the antimalarial evaluations. Plant extracts treatment showed higher mortality against mosquito larvae, lethal dose (Lc(50) and Lc(90)) was also worked out for the larval instars of malarial vector, Anopheles stephensi. Phytochemical screening revealed the presence of some vital insecticidal and antiplasmodial constituents such as terpenoids, flavonoids and alkaloids. The leaf and root extract of S. acuta and V. zizanioides showed markedly significant antimalarial activity and antivectorial activity effects even at low concentrations. o S. acuta and V. zizanioides are promising in mosquito control and also safe for the non-target organisms. This integrated application could be useful as alternative synthetic insecticides. These agents should preferentially to be applied in mosquito control strategies to reduce the mosquito populations and prevent the malaria.

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, this study was undertaken to assess the ovicidal potential of the crude hexane, benzene, chloroform, ethyl acetate, and methanol solvent extracts from the medicinal plant Ageratina adenophora (A. adenophora) against the filariasis vector, Culex quinquefasciatus (Cx. quinquefasciatus) (Diptera: Culicidae). Ovicidal activity was determined against Cx. quinquefasciatus mosquito to various concentrations ranging from 75-450 mg/L under the laboratory conditions. All the five solvents extracts showed moderate ovicidal activity; however, the methanol extract showed the highest ovicidal activity. One hundred percent mortality was observed at 375 mg/L. These results suggest that the 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 activity of A. adenophora plant extracts against filariasis vector, Cx. quinquefasciatus.

In traditional vector surveillance systems, adult mosquito density and the rate of mosquito-human host contact are estimated from the mosquito numbers captured in mechanical traps. But the design of the traps, their placement in the habitat and operating time, microclimate, and other environmental factors bias mosquito responses such that trapped mosquito numbers may be at variance with the numbers actually making human contact. As an alternative to mechanical traps, direct measurement of landing mosquito density enables real-time estimation of the mosquito–human-host-contact parameter. Based on this paradigm, we studied methods to measure mosquito landing responses to a human host. Our results showed: (a) an 18% difference (P<0.0001) in the mean number of female Aedes albopictus (Skuse) making initial contact with the skin (9.11±0.74min–1) compared with the number remaining on the skin for 5s (7.42±0.69min–1); (b) an increase (P<0.05) in the mean per minute (min−1) landing responses of Culex nigripalpus Theobald and Cx. quinquefasciatus Say with increased sampling time; (c) no difference (P>0.55) in the average number of Ae. albopictus landing on the arm (8.6±1.6min–1) compared with the leg (9.2±2.5min–1) of the same human subject; (d) differences among day-to-day landing patterns for the mosquito species we studied but measurable periodicity (P<0.05) in each case when daily patterns were averaged for four or more diel periods; and (e) an effect on landing mosquito density from air temperature (P<0.0001) for Ae. albopictus and Cx. nigripalpus and dew point temperature (P<0.0001) for Cx. quinquefasciatus. Results from this study were used to develop a procedure for safely and accurately measuring mosquito landing density on a human subject.

In recent years the utilization of secondary metabolites from plant extract has emerged as a novel technology for the synthesis of various nanoparticles.The aim of the present study was to evaluate the effect of plant synthesized silver nanoparticles (Ag NPs) using aqueous leaf extract of Calotropis gigantea to control dengue vector Aedes aegypti, malarial vector Anopheles stephensi.The synthesized AgNPs were characterized by UV–vis spectrum, scanning electron microscopy (SEM), Energydispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR). Synthesized silver nanoparticles (AgNPs) particles were confirmed by analysing the excitation of surface plasmon resonance (SPR) using UV–vis spectrophotometer at 410 nm. SEM analysis of the synthesized Ag NPs clearly showed the clustered and irregular shapes, mostly aggregated and having the size of 20– 35 nm. The chemical composition of elements present in the solution was determined by energy dispersive spectrum. The FTIR analysis of the nanoparticles indicated the presence of proteins, which may be acting as capping agents around the nanoparticles. Biosynthesis of nanoparticles may be triggered by several compounds such as carbonyl groups, terpenoids, phenolics, flavonones, amines, amides, proteins, pigments, alkaloids and other reducing agents present in the biological extracts.These results suggest that the synthesized Ag NPs have the potential to be used as an ideal eco-friendly approach for the control of the A. aegypti and A. stephensi. This method is considered as a new approach to control vectors. Therefore, this study provides first report on the mosquito larvicidal activity of synthesized Ag NPs against vectors

Mosquitoes are blood-feeding insects and serve as the most important vectors for spreading human diseases such as malaria, yellow fever, dengue fever, and filariasis. The continued use of synthetic insecticides has resulted in resistance in mosquitoes. Synthetic insecticides are toxic and affect the environment by contaminating soil, water, and air, and then natural products may be an alternative to synthetic insecticides because they are effective, biodegradable, eco-friendly, and safe to environment. Botanical origin may serve as suitable alternative biocontrol techniques in the future. The ovicidal efficacy of different extracts of Ageratina adenophora (A. adenophora) against Anopheles stephensi (An. stephensi) (Diptera: Culicidae). Larvicidal efficacy of the crude leaf extracts of A. adenophora with five different solvents like hexane, benzene, chloroform, ethyl acetate and methanol was tested against the early third instar larvae of An. stephensi. The ovicidal activity was determined against An. stephensi mosquito species to various concentrations ranging from 75-450 mg/L under the laboratory conditions. Among five solvent extracts tested, the methanol extract have most promising ovicidal activity. The methanol extract exerted zero hatchability (100% mortality) at 300 mg/L. From the results it can be concluded the crude extract of A. adenophora was a potential for controlling An. stephensi mosquito eggs.

Variations in the conditions accompanying mosquito development and mating can result in females of variable size that have not been inseminated. In this study, we compared the host finding activity of mated and unmated large and small Aedes albopictus (Skuse) and the repellency to these mosquitoes of 25% DEET. The percentage of females seeking the source of human odor in an olfactometer was significantly influenced by body size (P = 0.007) but not mating status (P = 0.07). Most respondents were large (71%) but 40% of all host seeking females were not inseminated. Landing rates by Ae. albopictus on human skin were influenced in screened cage tests by mating status (P < 0.0001) and body size (P = 0.004). Mated females exhibited the highest landing rates (17.3% [large] and 12.7% [small]) followed by unmated large females (7.3%) and unmated small females (6.4%). The Complete Protection Time (CPT) from mosquito landing provided by 25% DEET was significantly influenced by mating status (P = 0.002) and body size (P = 0.025). Unmated small females were repelled longer (7.5 h) than unmated large females (7.0 h) and longer than small and large mated females (6.3 h and 5.6 h, respectively). CPT using 25% DEET was inversely related to mosquito landing rate in all treatment groups with 75 min more protection on average from bites by unmated females compared with mated females.

The present study was to establish of Acalypha alnifolia leaf extract and microbial insecticide, Metarizhium anisopliae on larvicidal and pupicidal properties of against the malaria fever mosquito, Anopheles stephensi. The leaf extract showed larvicidal and pupicidal effects after 24 h of exposure; however, the highest larval and pupal mortality was found in the leaf extract of ethanol A. alnifolia against the 1st to 4th instar larvae and pupae of values LC(50) value of 1st instar was 5.388%, 2nd instar was 6.233%, 3rd instar was 6.884%, 4th instar was 8.594%, and pupae was 10.073%, respectively, and microbial insecticide, M. anisopliae against the 1st to 4th instar larvae and pupae of values LC(50) value of 1st instar was 7.917%, 2nd instar was 10.734%, 3rd instar was 17.624%, 4th instar was 26.590%, and pupae was 37.908%, respectively. Moreover, combined treatment of values of LC(50) value of 1st instar was 3.557%, 2nd instar was 4.373%, 3rd instar was 5.559%, 4th instar was 7.223%, and pupae was 8.542%, respectively. No mortality was observed in the control. The results that the leaves extract of A. alnifolia and microbial insecticide, M. anisopliae is promising as good larvicidal and pupicidal properties of against malaria fever mosquito, A. stephensi. This is an ideal eco-friendly approach for the control of malarial vector, A. stephensi as a vector control programs. Therefore, this study provides first report on the combined effect of mosquitocidal efficacy of this plant extract and fungal pathogen of M. anisopliae against A. stephensi from Southern India.

A biological method was used to synthesize stable silver nanoparticles that were tested as mosquito larvicides against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Annona squamosa leaf broth (5%) reduced aqueous 1 mM AgNO₃ to stable silver nanoparticles with an average size of 450 nm. The structure and percentage of synthesized nanoparticles was characterized by using ultraviolet spectrophotometry, X-Ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy methods. The median lethal concentrations (LC₅₀) of silver nanoparticles that killed fourth instars of Ae. aegypti, Cx. quinquefasciatus, and An. stephensi were 0.30, 0.41, and 2.12 ppm, respectively. Adult longevity (days) in male and female mosquitoes exposed as larvae to 0.1 ppm silver nanoparticles was reduced by ~30% (p<0.05), whereas the number of eggs laid by females exposed as larvae to 0.1 ppm silver nanoparticles decreased by 36% (p<0.05).

OBJECTIVE:To determine the mosquito larvicidal activities of hexane, chloroform, ethyl acetate, acetone and methanol leaf extract of Orthosiphon thymiflorus (O. thymiflorus) against Anopheles stephensi (An. stephensi), Culex quinquefasciatus (Cx. quinquefasciatus) and Aedes aegypti (Ae. aegypti).METHODS:The larvicidal activity was assayed against three mosquito species at various concentrations ranging from (50-450 ppm) under the laboratory conditions. The LC(50) and LC(90) value of the O. thymiflorus leaf extract was determined by Probit analysis.RESULTS:The LC(50) values of hexane, chloroform, ethyl acetate, acetone and methanol extract of O. thymiflorus third instar larvae of An. stephensi were LC(50)= 201.39, 178.76, 158.06, 139.22 and 118.74 ppm; Cx. quinquefasciatus were LC(50)=228.13, 209.72, 183.35, 163.55 and 149.96 ppm and Ae. aegypti were LC(50)=215.65, 197.91, 175.05, 154.80 and 137.26 ppm, respectively. Maximum larvicidal activity was observed in the methanolic extract followed by acetone, ethyl acetate chloroform and hexane extract. The larval mortality was observed after 24 h exposure. No mortality was observed in control.CONCLUSIONS:The present results suggest that the effective plant crude extracts have potential to be used as an ideal eco-friendly approach for the control of mosquito vectors. This study provides the first report on the larvicidal activity of this plant crude solvent extract of against An. stephensi, Cx. quinquefasciatus and Ae. aegypti mosquitoes.

Ethanolic extracts of Cynodon dactylon, Aloe vera, Hemidesmus indicus and Coleus amboinicus were tested for their toxicity effect on the third-instar larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti. The leaves of C. dactylon, A. vera, H. indicus and C. amboinicus were collected from natural habitats (forests) in Western Ghats, Tamil Nadu, India. A total of 250 g of fresh, mature leaves were rinsed with distilled water and dried in shade. The dried leaves were put in Soxhlet apparatus and extract prepared using 100% ethanol for 72 h at 30–40°C. Dried residues were obtained from 100 g of extract evaporated to dryness in rotary vacuum evaporator. Larvicidal properties of ethanolic leaf extracts showed that the extracts are effective as mosquito control agents. The larval mortality was observed after 24 h exposure. No mortality was observed in the control. The median lethal concentration (LC50) values observed for the larvicidal activities are 0.44%, 0.51%, 0.59% and 0.68% for extracts of C. dactylon, A. vera, H. indicus and C. amboinicus, respectively. The observed mortality were statistically significant at P < 0.05 level. C. dactylon showed the highest mortality rate against the three species of mosquito larvae in laboratory and field. The selected plants were shown to exhibit water purification properties. Water quality parameters such as turbidity, pH and water clarity were analyzed in the water samples (pre-treatment and post-treatment of plant extracts) taken from the different breeding sites of mosquitoes. Water colour, turbidity and pH were reduced significantly after treatment with C. dactylon (13 HU, 31.5 mg/l and 6.9), H. indicus (13.8 HU, 33 mg/l and 7.1), A. vera (16 HU, 33.8 mg/l and 7.4) and C. amboinicus (21 HU, 35 mg/l and 7.5) extracts. The study proved that the extracts of C. dactylon, A. vera, H. indicus and C. amboinicus have both mosquitocidal and water sedimentation properties.

The efficacy of whole plant extracts of Leucas aspera and Bacillus sphaericus has been proven against larvicidal and pupicidal activities of the malarial vector, Anopheles stephensi. The present study investigated the larvicidal and pupicidal activity against the first to fourth instar lavae and pupae of the laboratory-reared mosquitoes, A. stephensi. The medicinal plants were collected from the area around Maruthamalai hills, Coimbatore, Tamil Nadu, India. L. aspera whole plant was washed with tap water and shade dried at room temperature. 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 ethanol for 8 h using a Soxhlet apparatus. The extracts were filtered through a Buchner funnel with Whatman number 1 filter paper. The crude plant extracts were evaporated to dryness in a rotary vacuum evaporator. The plant extract showed larvicidal and pupicidal effects after 24 h of exposure. All larval instars and pupae have considerably moderate mortality; however, the highest larval mortality was the ethanolic extract of whole plant L. aspera against the first to fourth instar larvae and pupae values of LC50 = I instar was 9.695%, II instar was 10.272%, III instar was 10.823%, and IV instar was 11.303%, and pupae was 12.732%. B. spaericus against the first to fouth instar larvae and pupae had the following values: I instar was 0.051%, II instar was 0.057%, III instar was 0.062%, IV instar was 0.066%, and for the pupae was 0.073%. No mortality was observed in the control. The present results suggest that the ethanolic extracts of L. aspera and B. sphaericus provided an excellent potential for controlling of malarial vector, A. stephensi.