Fourth Instar Larvae Of Ae Research Articles

Biological Control of Aedes aegypti Larvae using Sea Shell Powder

Background: The Aedes aegypti mosquito is a primary vector for several arboviral diseases, including dengue, Zika, chikungunya and yellow fever, posing significant public health challenges, especially in tropical and subtropical regions. Traditional chemical insecticides have been the mainstay for controlling Aedes aegypti populations, but their extensive use has led to the development of insecticide resistance, environmental pollution and adverse effects on non-target organisms. This study explores the potential of sea shell powder as a natural larvicide against Aedes aegypti larvae. Methods: Sea shell powder, derived from the calcified exoskeletons of marine mollusks, was tested for its larvicidal activity against fourth instar larvae of Ae. aegypti at concentrations ranging from 100 to 600 ppm. Result: The results demonstrated a concentration and time-dependent increase in larval mortality, with LC50 values of 407.01 ppm at 24 hours and 327.55 ppm at 48 hours. The findings suggest that sea shell powder could serve as an effective, environmentally sustainable alternative to chemical insecticides, offering advantages such as biodegradability, low cost and reduced risk of resistance development. This study supports the potential inclusion of sea shell powder in integrated mosquito management programs, particularly in areas with prevalent insecticide resistance.

Evaluation of Larvicidal Properties of Zingiber officinale Rhizome and Allium Sativum Bulbs against Aedes aegypti

This study evaluates the larvicidal potential of methanolic extracts derived from Zingiber officinale (ginger) rhizome and Allium sativum (garlic) bulbs against the 4th instar larvae of Aedes aegypti, a key vector responsible for transmitting diseases such as dengue, yellow fever, chikungunya, and Zika. Due to the increasing resistance of mosquitoes to conventional insecticides, there is a pressing need for alternative, eco-friendly vector control methods. Botanical extracts, known for their pesticidal properties, offer a promising solution. Methanolic extracts were collected from the selected test plant parts and different test solutions were prepared to test their larvicidal efficacy against the fourth instar larvae of Ae. aegypti. The results indicated a significant dose-dependent increase in larval mortality for both extracts. The extracts of Z. officinale consistently showed better larvicidal effects than outperformed the extracts of A. sativum at all tested concentrations, with mortality rates ranging from 14.29% at 62.5 ppm to 79.22% at 500 ppm. In contrast, A. sativum exhibited mortality rates from 11.69% at 62.5 ppm to 76.62% at 500 ppm. The LC50 values further highlighted the greater efficacy of ginger extract, with an LC50 of 219.10 ppm compared to 237.39 ppm for garlic. These results suggest the usage of extracts of ginger rhizomes and garlic bulbs as eco-friendly larvicides against Ae. aegypti mosquitoes.

Identification of fourth-instar larvae of Aedes albopictus (Skuse) (Diptera: Culicidae) employing scanning electron microscopic tool.

Aedes albopictus is a vector of numerous viruses in tropical and subtropical regions worldwide, including encephalitis and dengue fever. Although the identification keys depend exclusively on the characteristics of the fourth larval instar, the studies were carried out using scanning electron microscopy (SEM) on the morphology of Ae. albopictus are still insufficient, and more research is required. Therefore, the purpose of this study was to present a comprehensive description of Ae. albopictus mosquitoes based on the morphological features of their fourth-instar larvae to distinguish them from other mosquito species. Antennae, feeding mouth brushes, mandibles, maxillae, labia, comb scales, anal papillae, siphon, respiratory spiracles, and pecten teeth were among the morphological features specifically described using SEM. The sensilla trichoidea and the sensilla basiconica are the sensory spicules found on the antennal integument. The labrum is a tessellated membrane with two movable brushes on the sides and one middle brush. The mandibles have four sellar setae on the anterolateral side, and the maxillae, which have a thumb-like structure and a palp located laterally and about four-fifths of the way from the maxillary brush base to the maxillary notch, are the articulating appendages. On the apex of the palp, there are five sensilla. The eighth abdominal segment is a tiny pentagonal structure with 12 comb scales laterally and a respiratory siphon dorsally. The siphon has two rows of pectin teeth, with 12 teeth per row. Four pairs of siphonal tufts and five perispiracular lobes surround the respiratory spiracles. The anal segment has four anal papillae, a ventral brush, a dorsal brush, and an incomplete saddle. The findings demonstrate that the fourth-instar larvae of Ae. albopictus have distinctive morphological features, which are crucial for understanding their key characteristics and identifying them, preventing inaccurate identification, and facilitating the control of diseases transmitted by the mosquito vector. RESEARCH HIGHLIGHTS: A detailed description of various taxonomical interest structures for the fourth-instar larvae of Aedes albopictus is included in this study. Scanning electron microscopy is considered a helpful technique for identifying Ae. albopictus larvae in their fourth instar.

Mosquitoes' larvicidal activity of Phoenix dactylifera Linn extracts against Aedes aegypti

Aedes aegypti mosquitoes are inducers of viruses such as DENV and ZIKV when they bite a person, which could lead to clinical symptoms like fever, headache, and rashes. This contemporary study aspired to examine the insecticidal potency of different extracts of the seed of Phoenix dactylifera on larvae of Aedes aegypti. The cold maceration process was used for the extraction of an accurately weighed 100 g of the finely powdered seed of P. dactylifera plant using hexane, petroleum ether, and methanol with strong handshaking for 48 hours. Methanolic extract of P. dactylifera showed 52% mortality at 1000 ppm and 20% dead at 500 and 250 ppm, respectively, and showed no larvicidal potency at 125 ppm against the fourth instar larvae of Ae. aegypti. Whereas hexane and petroleum ether seed plant extracts were found to be equally less effective against the fourth instar larvae of Ae. aegypti species, both showed 20% and 12% at 1000 and 500 ppm, respectively. The various concentrations of P. dactylifera extracts of hexane, petroleum ether, and methanol induced the larvicidal potency (LC50) after 24 h against IV instar larvae of Ae. aegypti were 2049.229, 2049.229, and 984.488 ppm, respectively. It was concluded that the seed extracts of P. dactylifera are potential candidates to be utilized as novel plant insecticides in curbing the spread of DENV and ZIKV disease vectors.

Larvicidal Activity of Methyl Benzoate, a Volatile Organic Compound, Against the Mosquitoes Aedes albopictus and Culex pipiens (Diptera: Culicidae).

Methyl benzoate (MBe) is a volatile organic molecule found in various plants; it is used as an insect semiochemical. MBe also has a biorational insecticidal effect against various agricultural and urban arthropod pests. The present study was the first to assess the larvicidal potential of MBe against fourth-instar larvae of the mosquitoes Aedes albopictus (Skuse) and Culex pipiens (L.). A positive association was observed between MBe concentrations and larval mortality in both the species. The highest mortality recorded was 100% for Ae. albopictus and 56% for Cx. pipiens after 24 h of exposure to 200 ppm MBe. The lethal median concentration (LC50) values of MBe against fourth-instar larvae of Ae. albopictus and Cx. pipiens were 61 ppm and 185 ppm, respectively. These results suggest that MBe has great potential for use as an environmentally friendly larvicidal agent for mosquito control.

BIOEFFICACY OF SESBANIA GRANDIFLORA LEAVES SILVER NANOPARTICLES AGAINST AEDES AEGYPTI LARVAE

The present study evaluated the green synthesis of silver nanoparticles using the leaf extract Sesbania grandiflora and charecterized by the UV-Vis Spectrophotometry, Particle size analyzer and Fourier Transform Infra-Red Spectroscopy (FTIR) and also evaluated its killing effect against larval and pupal stages of Aedes aegypti. The production of silver nanoparticles was observed by the colour changes from yellow to dark brown and further confirmed by UV-Vis spectroscopy showed an absorption band at 340.8nm; the size of the nanoparticles is around 723 nanometer according to particle size analysis. FTIR analysis showed that functional group of synthesized silver nanoparticles belongs to free amino or carboxyl group. FTIR analysis showed the functional group of synthesized silver nanoparticles and the absorption bands were seen at 518.82cm-1, 730.01cm-1, 873.69cm-1, 1093.56cm-1, 1139.85cm-1, 1640.35cm-1, 2088.76cm-1, 3446.56cm-1. The effect of leaf extract of S. grandiflora on the survival and development of fourth instar larvae of Ae. Aegypti was sudied. LC50 values of aqueous leaf extract of S. grandiflora against Ae. aegypti and silver nanoparticles synthesized from aqueous leaf extract of S. grandiflora were 293.87 ppm and 5.548ppm respectively. The killing effect increased along with the increasing concentration of aqueous and silver nanoparticles synthesized from leaf extract of S. grandiflora. The synthesized silver nanoparticles from the leaf extract S. grandiflora were more efficient than the aqueous leaf extract. Thus the present study also suggested that the S. grandiflora leaf mediated silver nanoparticles could be used as an effective larvicidal and pupicidal agents.

Behavior of Aedes albifasciatus (Diptera: Culicidae) larvae from eggs with different dormancy times and its relationship with parasitism by Strelkovimermis spiculatus (Nematoda: Mermithidae).

Aedine mosquitoes go through unfavorable periods as dormant eggs. However, extended dormancy times lead to a depletion of egg reserves, which might be partially compensated by changes in larval-feeding behavior. Changes in larval behavior may also be induced by parasitism by mermithids probably as a strategy to reduce the impact of the parasite on the host. The most abundant floodwater mosquito in southern South America is Aedes albifasciatus (Diptera: Culicidae), a species naturally parasitized by Strelkovimermis spiculatus (Nematoda: Mermithidae). This study aimed to evaluate the behavior of fourth-instar larvae of Ae. albifasciatus from eggs with 2, 4, and 6months of dormancy, parasitized or not by S. spiculatus. To achieve this, eight categories of behavior were defined, and then, each individual was observed for 5min, and its behaviors and their duration were recorded. The behaviors with the highest percentage of observation time were still (50.1%) and wriggle swimming (33.6%), while those with the lowest percentage of observation time were those involving active foraging (less than 8%). A great variability in the behaviors was observed among individuals within the same treatment. The type and duration of each behavior did not vary in relation to egg dormancy time or parasitism, but parasitism affected the level of larval activity. Parasitized larvae performed, on average, fewer behaviors than non-parasitized larvae. This result supports the hypothesis that S. spiculatus parasitism affects the behavior of Ae. albifasciatus larvae by reducing their level of activity.

A strategy to decrease vectorial competence of dengue mosquito Aedes aegypti by alteration of its gut microbiota using Indian traditional medicinal plants

In the present study, the sensitivity of the gut microbes of dengue fever mosquito Aedes aegypti to Indian traditional medicinal plants was evaluated. The microbes were isolated from the midgut of laboratory-reared fourth instar larvae of Ae. aegypti and grown on Luria-Bertini agar plates at an optimum temperature of 27oC. The microbial colonies were differentiated based on their characteristics such as size, shape, opacity, elevation, consistency, and rate of growth. The axenic culture of different strains was obtained by streaking method. Ten different types of microbial clones were identified up to species level using Biolog’s advanced phenotypic technology. Five Indian traditional plants: Ocimum sanctum, Azadirachta indica, Catharanthus roseus, Curcuma longa, and Syzygium aromaticum and an invasive obnoxious weed Lantana camara were used in the present study. The extracts of the specific parts of individual plants were prepared in ethanol and hexane using ‘Soxhlet apparatus’. The extracts were screened for their antimicrobial activities by disc diffusion assay. The results indicate that the plants used in the present study possessed antimicrobial activities against gut microbes of Ae. aegypti. However, the sensitivity of different microbes to the extracts varied. The zone of inhibition observed after 24 h of incubation revealed that ethanol extract of A. indica has the most potent antibacterial activity; followed by that of S. aromaticum, C. longa and O. sanctum. L. camara and C. roseus were least effective against gut microbes of Ae. aegypti.

Mannosylerythritol Lipids Mediated Biosynthesis of Silver Nanoparticles: An Eco-friendly and Operative Approach Against Chikungunya Vector Aedes albopictus

Recently the bioactive products of microbes and their nanoformulation particles have been remarkably studied in insecticides. In the present study, the Mannosylerythritol lipids (MELs) biosurfactant produced from Ustilago maydis has been employed in the rapid synthesis of silver nanoparticles (AgNPs). UV–Vis spectrum was initially confirmed the bio-fabricated AgNPs and further characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, X-ray diffraction, and Fourier transform infrared. The mosquitocidal potency of MELs and AgNPs were assessed against larvae and pupae of Aedes albopictus. The AgNPs exhibited maximum toxicity against Larvae and pupae of Ae. albopictus with LC50 values ranging from 1.03 μg/ml (I) to 1.19 μg/ml (pupae) compared to the MELs toxicity which showed LC50 values ranging from 31 μg/ml (I) to 59 μg/ml (pupae). Further investigations of oxidative stress effects exerted by the tested materials against fourth instar larvae of Ae. albopictus showed an alteration in the levels of total protein, superoxide dismutase, peroxidase, and catalase enzyme activity. Interestingly, the TEM images of the midgut cells of treated larvae explored AgNPs accumulation in the rough endoplasmic reticulum and other cell organelles. Overall, this study suggests that AgNPs could be employed as an efficient tool in mosquito vector control strategies.

Toxicity of the aqueous leaf and Stem-bark extracts of <em>Annona muricata </em>to the 4<sup>th</sup> instar larvae of <em>Aedes aegypti</em>

The crude aqueous extracts were tested against the fourth instar larvae of Aedes aegypti (Diptera: Culicidae) at five concentrations of the technical material ranging from 12.5-200 µg/ml, including control. The bioassays were carried out in the laboratory at temperature of 29◦C ± 2 and 29.5 ± 5% relative humidity. Four replicates of each concentration of the respective toxicants in a Completely Randomised Design (CRD) were introduced with ten fourth instar larvae of Ae. Aegypti. Mortality resulting from eclosion inhibition was monitored at 3-hours interval for a period of 3, 6, 9, 12- and 24-hours post treatment. Data collected were analyzed using log-probit regression and analysis of variance. Results showed that mortality increased with increase in time and concentration and these were significantly different (P<0.05). Results indicated 65% and 87.1% mortality at the highest concentration (200 µg/ml) of the leaf and stem-bark aqueous extract respectively while the least concentration (12.5 µg/ml) resulted in 19.4% and 38.7% respectively. The LC50 values were 92.5 µg/ml and 26.5 µg/ml for the leaf and stem-bark aqueous extract respectively while the LT50 values were 29.7hr and 53.9hr respectively for the leaf and the stem-bark aqueous extract. The study suggests that Annona muricata leaf and stem-bark aqueous extract has shown promise as biopesticide for Ae. Aegypti larvae control. However, the stem-bark was found to be more effective compared to the leaf aqueous extract.

Synthesis, characterization and efficacy of silver nanoparticles against Aedes albopictus larvae and pupae

Silver nanoparticles have been studied in a wide range of medical and entomological research works due to their eco-friendly aspects. In our study salicylic acid (SA) and its derivative, 3,5-dinitrosalicylic acid (DNS), were used in a one-step synthesis of silver nanoparticles (AgNPs). First, UV–vis absorption spectroscopy was used to detect the formation of AgNPs. Second, the synthesized nanoparticles were characterized using scanning electron microscope, transmission electron microscope; energy-dispersive spectroscopy, X-ray diffraction analysis and Fourier transform infrared spectroscopy. I, II, III and IV Instar larvae and pupae of Ae. Albopictus were exposed to various concentrations of SA, DNS and synthesized AgNPs for 24h to evaluate the larvicidal and pupicidal effect. In larvicidal bioassay of SA, moderate mortality was observed at 180ppm against Ae. Albopictus with LC50 values of 86, 108, 135 and 141ppm for instar larvae I, II, III and IV, respectively. Synthesized AgNPs showed highest mortality rate at 12ppm and the LC50 values of SAAgNPs were 1.2ppm (I), 1.4ppm (II), 1.8ppm (III), 2.0ppm (IV) and 1.4ppm (pupae). Whereas LC50 values of DNSAgNPs were 1.2ppm (I), 1.5ppm (II), 1.8ppm (III) 2.3ppm (IV) and 1.4ppm (pupae). Moreover, the investigations toward the systemic effect of the tested substances on the fourth instar larvae of Ae. albopictus was evaluated and the levels of total proteins, esterases, acetylcholine esterase, and phosphatase enzymes were found to be significantly decreased as compared with the control. These results highlight that SA-AgNPs and DNS-AgNPs are potential tools to control larval populations of mosquito.

Growth inhibitory effect of phenolic extracts of Ziziphus jujuba Mill. in dengue vector Aedes aegypti(L) in parent and F1 generation.

To evaluate the lethal and emergence inhibitory effect of alkaloid, phenolic and terpenoid extracts of Ziziphus jujuba (Rhamnaceae) against Aedes aegypti (Diptera: Culicidae), and to explore the effect of the most effective fraction on developmental and biochemical parameters of the dengue vector. The fourth instar larvae of Ae. aegypti were exposed to alkaloid, phenolic and terpenoid extracts from Z. jujuba leaves to test their toxicity and emergence inhibitory effects. Phenolic extract, being the most effective was further tested against the mosquitoes for their growth inhibitory effect supported by biochemical changes in the parent and F1 generation. While the different secondary metabolite fractions i.e., alkaloid, phenolics and terpenoid caused mortality at larval and pupal stages, the LC50 value was the lowest for phenolic fraction. Further study carried out with the phenolic fraction revealed that it affected growth by decreasing adult life span, fertility and fecundity of the mosquitoes. The reduction in growth was also accompanied by decrease in carbohydrate and lipid levels. It is concluded that the phenolic extract of the leaves of Z. jujuba is a potential candidate for control of Aedes mosquitoes.

Controlling Aedes albopictus and Culex pipiens pallens using silver nanoparticles synthesized from aqueous extract of Cassia fistula fruit pulp and its mode of action

Mosquitoes act as key vector for transmission of devastating parasites and pathogens which affect millions of people globally. In this research, the green synthesis of silver nanoparticles of Cassia fistula fruit pulp as an innovative and operative tool against vector mosquitoes is presented. Silver nanoparticles were characterized by a series of techniques including Fourier transform infrared spectroscopy, Transmission Electron Microscope and confirmed by Scanning Electron Microscope, UV-Vis spectrophotometry and X-ray diffraction. Silver nanoparticles were highly effective against the larvae (I–IV instar) and pupae of Aedes albopictus and Culex pipiens pallens after 24, 48 and 72 h of treatment. Ae. albopictus had LC50 values ranging from 8.3 mg/L (I instar) to 17.3 mg/L (pupae) and LC50 ranging from 1.1 mg/L (I instar) to 19.0 mg/L (pupae) against Cx. pipiens pallens. The systemic effect of AgNPs was further assessed in the fourth instar larvae of Ae. albopictus and Cx. pipiens pallens by measuring the levels of total proteins and activity of two important marker enzymes: Acetylcholinesterase and α- and β-carboxylesterase. Overall, the findings of the study suggest that the use of Cassia fistula-fruit pulp extract mediated synthesis of silver nanoparticles can be used for controlling vector mosquitoes. This is the first report on the mosquito larvicidal and pupicidal activity of AgNPs synthesized by Cassia fistula fruit pulp and its possible mechanism of action.

IdentificationofLarvicidalConstituentsofthe EssentialOilofEchinopsgrijsii Rootsagainstthe ThreeSpeciesofMosquitoes.

The screening of Chinese medicinal herbs for insecticidal principles showed that the essential oil of Echinops grijsii Hance roots possessed significant larvicidal activity against mosquitoes. The essential oil was extracted via hydrodistillation and its constituents were determined by gas chromatography-mass spectrometry (GC-MS) analysis. GC-MS analyses revealed the presence of 31 components, with 5-(3-buten-1-yn-1-yl)-2,2′-bithiophene (5-BBT, 27.63%), α-terthienyl (α-T, 14.95%), 1,8-cineole (5.56%) and cis-β-ocimene (5.01%) being the four major constituents. Based bioactivity-directed chromatographic separation of the essential oil led to the isolation of 5-BBT, 5-(4-isovaleroyloxybut-1-ynyl)-2,2′-bithiophene (5-IBT) and α-T as active compounds. The essential oil of E. grijsii exhibited larvicidal activity against the fourth instar larvae of Aedes albopictus, Anopheles sinensis and Culex pipiens pallens with LC50 values of 2.65 μg/mL, 3.43 μg/mL and 1.47 μg/mL, respectively. The isolated thiophenes, 5-BBT and 5-IBT, possessed strong larvicidal activity against the fourth instar larvae of Ae. albopictus (LC50 = 0.34 μg/mL and 0.45 μg/mL, respectively) and An. sinensis (LC50 = 1.36 μg/mL and 5.36 μg/mL, respectively). The two isolated thiophenes also had LC50 values against the fourth instar larvae of C. pipiens pallens of 0.12 μg/mL and 0.33 μg/mL, respectively. The findings indicated that the essential oil of E. grijsii roots and the isolated thiophenes have an excellent potential for use in the control of Ae. albopictus, An. sinensis and C. pipiens pallens larvae and could be used in the search for new, safer and more effective natural compounds as larvicides.

Impact of Terminalia chebula Retz. against Aedes aegypti L. and non-target aquatic predatory insects

Aedes aegypti Linn is one of the most important mosquito species. The vectors are responsible for causing deadly diseases like dengue and dengue hemorrhagic fever. Several chemical pesticides used to control these dengue vectors caused severe toxic significances on human health and other non-target beneficial insects. Therefore the current investigation has been made to access the bio-efficacy of the crude seed extracts of T. chebula against the dengue vector Ae. aegypti. The GC-MS analysis of crude seed extracts of T. chebula identified nine chemical compounds with major peak area in the 1,2,3-Benzenetriol (61.96%), followed by Tridecanoic acid (09.55%). Ae. aegypti larvae showed dose dependent mortality rate was observed between the treatments. Prominent protection rate at greater concentrations of 100ppm and moderate protection at 75 and 50ppm was observed in the repellent assay. Lethal concentration (LC50 and LC90) of fourth instar larvae of Ae. aegypti was observed in 138 and 220ppm concentration respectively. Similarly, the seed extracts showed 100% adulticidal activity at the concentration of 400ppm at 30min of exposure time. Phytochemicals present in the seed extracts of T. chebula significantly affects the major portions of the midgut tissues of Ae. aegypti at the concentration of 100ppm. The toxicological evaluation of seed extracts also proved non-toxic towards the A. bouvieri and Tx. splendens aquatic predatory insects. Hence, the present result suggest that bio-rational plant derived T. chebula could be incorporated in the dengue vector control and have no adverse effects on non-target beneficial insects.

Phytochemical constituents and larvicidal activity of Tragia involucrata Linn. (Euphorbiacea) leaf extracts against chikungunya vector, Aedes aegypti (Linn.) (Diptera: Culicidae)

Objective: To determine the phytochemical and larvicidal activity of Tragia involucrata (T. involucrata) leaf extracts against fourth instar larvae of Ae. aegypti. Methods: Phytochemical analysis of hexane leaf extract was performed and larvicidal activity was determined against Ae. aegypti at concentrations of 50, 100, 150, 200 and 250 mg/L. Larval mortality was assessed after 24 h. Results: The hexane extracts of T. involucrata was found to be higher mortality against the larvae of Ae. aegypti with a LC50 value of 153.51 mg/L. Conclusions: These results suggested that the leaf extracts of T. involucrata showed potential to be used as an ideal ecofriendly approach for the control of the Ae. aegypti.

Larvicidal activity and GC–MS analysis of Leucas aspera against Aedes aegypti Anopheles stephensi and Culex quinquefasciatus

The mosquitocidal activity of aqueous, ethanol, methanol, chloroform and petroleum ether plant extracts of Leucas aspera against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus was analyzed. The larval mortality of fourth instar larvae of Ae. aegypti, An. stephensi and Cx. quinquefasciatus after 24h and 48h of treatment was observed separately in control 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500ppm concentrations. The plant extracts were screened to identify the phytochemical bioactive compounds. Ae. aegypti was found to be most susceptible than the other species. Based on probit analysis the 24h and 48h methanol extracts of L. aspera showed pronounced larvicidal activity when compared with the other extracts. An LC50 and LC90 value of methanol extracts against Cx. quinquefasciatus was found to be 37.649ppm and 27.855ppm (24h), 79.150ppm and 73.284ppm (48h) respectively. LC50 and LC90 values were 35.624ppm and 20.897ppm (24h), 64.260ppm and 60.096ppm (48h) against Ae. aegypti. The 24h and 48h LC50 and LC90 values of ethanol extracts of L. aspera were found to be 40.877ppm and 34.359ppm, 72.903ppm and 67.355ppm against An. stephensi. The extracts of this plant showed potent larvicidal efficacy and can be considered for further investigation.

Laboratory Evaluation of Larvicidal Activity of the Essential oil of Allium tuberosum Roots and its Selected Major Constituent Compounds Against Aedes albopictus (Diptera: Culicidae).

The aim of this research was to evaluate larvicidal activity of the essential oil of Allium tuberosum Rottler ex Sprengle roots and its constituents against larval mosquitoes (Aedes albopictus Skuse). Essential oil of A. tuberosum was obtained by hydrodistillation and analyzed by gas chromatography and gas chromatography-mass spectrometry. The major constituents of the oil were found to be sulfur-containing compounds, including allyl methyl trisulfide (35.19%), diallyl disulfide (28.31%), diallyl trisulfide (20.91%), and dimethyl trisulfide (12.33%). The essential oil of A. tuberosum exhibited larvicidal activity against the fourth-instar larvae of Ae. albopictus, with an LC50 value of 18 μg/ml. The constituents compounds-diallyl trisulfide (LC50 = 4 μg/ml) and diallyl disulfide (LC50 = 6 μg/ml)-possessed stronger larvicidal activity than allyl methyl trisulfide (LC50 = 27 μg/ml) and dimethyl trisulfide (LC50 = 35 μg/ml) against the fourth-instar larvae of Ae. albopictus. The results indicated that the essential oil of A. tuberosum and its major constituents have good potential as a source for natural larvicides.

Mosquito larvicidal and pupaecidal potential of prodigiosin from Serratia marcescens and understanding its mechanism of action

Mosquitoes spread lethal diseases like malaria and dengue fever to humans. Considering mosquito vector control as one of the best alternatives to reduce new infections, here we have analyzed the effect of purified pigment prodigiosin extracted from Serratia marcescens (NMCC 75) against larval and pupal stages of Aedes aegypti and Anopheles stephensi mosquitoes. Mosquito larvicidal activities of purified prodigiosin revealed LC50 values of 14 ± 1.2, 15.6 ± 1.48, 18 ± 1.3, 21 ± 0.87 µg/ml against early IInd, IIIrd, IVth instar and pupal stages of Ae. aegypti, respectively. LC50 values for An. stephensi were found to be 19.7 ± 1.12, 24.7 ± 1.47, 26.6 ± 1.67, 32.2 ± 1.79 µg/ml against early IInd, IIIrd, IVth instar and pupae of An. stephensi, respectively. Further investigations toward understanding modes of action revealed variations in the activities of esterases, acetylcholine esterases, phosphatases, proteases and total proteins in the fourth instar larvae of Ae. aegypti indicating intrinsic difference in biochemical features due to prodigiosin treatment. Although there was no inhibition of enzymes like catalase and oxidase but may have profound inhibitory effect on carbonic anhydrase or H+-V-ATPase which is indicated by change in the pH of midgut and caeca of mosquito larvae. This reduced pH may be possibly due to the proton pump inhibitory activity of prodigiosin. Pure prodigiosin can prove to be an important molecule for mosquito control at larval and pupal stages of Ae. aegypti and An. stephensi. This is the first report on the mosquito pupaecidal activity of prodigiosin and its possible mechanism of action.

Effect of Polygonum hydropiper L. against dengue vector mosquito Aedes albopictus L.

The present study aimed to evaluate the essential oil and an isolated compound from the leaves of Polygonum hydropiper L. against dengue vector mosquito Aedes albopictus L. The plant material was macerated and steam distilled using clavenger apparatus for oil extraction. The essential oil was tested at different concentrations of 100, 50, 25, 12.5 and 6.25 ppm concentrations against the larvae of Ae. albopictus. The isolated compound was tested for larvicidal, ovicidal, repellent, oviposition deterrent and adulticidal activities at 10, 5, 2.5, 1.25 and 0.625 ppm concentrations. The essential oil exhibited LC₅₀ values of 194.63 and 199.65 and confertifolin exhibited LC₅₀ values of 2.02 and 3.16 against the second and fourth instar larvae of Ae. albopictus, respectively. The ovicidal activity of 100% on 0- to 6-h-old eggs, repellent activity of 320.6 min, oviposition deterrent activity of 98.51% and adulticidal activity of 100% at 10 ppm concentration of confertifolin were recorded. No mortality of was observed in negative control. To the best of our knowledge, this is the first report on the potential mosquitocidal activities of confertifolin against Ae. albopictus.