Instar Larvae Of Ae Research Articles

Marching towards bioeconomy: Larvicidal effect of three indigenous plant extracts from Sri Lanka—Garcinia quaesita, Garcinia zeylanica, and Coleus hadiensis on dengue vector Aedes aegypti

AbstractBioeconomy would be a beneficial solution for funding through the rational use of finances and human resources in order to achieve better productivity and fruitfulness of mosquito control programs. Synthetic insecticides are widely used to repress mosquitoes. However, it instigates problems such as insecticide resistance among mosquitoes such as developing resistance, bio‐accumulation, and ecosystem destabilization. Natural plant‐based products are a healthy alternative to use as mosquito larvicides. The country has to spend a considerable cost for buying synthetic insecticides too. Therefore, the present study was undertaken to evaluate larvicidal efficacy of Garcinia zeylanica, Garcinia quaesita, and Coleus hadiensis against Aedes aegypti mosquito larvae. Fresh leaves of plants were collected, and the aqueous crude extract was prepared. Phytochemicals were extracted using refluxing technique. A concentration series of crude extract of leaves were prepared separately from 20 to 100 mg/L. Batches of each containing 100 third instar larvae of Ae. aegypti were used for larval bioassays. Ae. aegypti mosquito larvae were evaluated in accordance with the guidelines of World Health Organization. The experimental setup was repeated four times at each concentration. Probit analysis was used to evaluate the relationship of mortality with the concentration of aqueous crude extract. The G. zeylanica and G. quaesita leaf extracts showed a dose‐dependent effect against Ae. aegypti larvae after the 24 and 48 h exposure period. Interestingly, C. hadiensis did not show any dose‐dependent effect against A. aegypti mosquito larvae. The percentage mortality rates have shown a significant variance among different concentrations (P = 0.000). The recorded LC50 and LC90 for aqueous crude extract of G. zeylanica were 27.167 and 52.861 g/L, respectively, and LC50 and LC90 for aqueous crude extract of G. quaesita were 36.841 and 76.036 g/L, respectively, after 24 h of exposure period. The G. zeylanica and G. quaesita plant's high larvicidal activity is supported by the presence of phytochemicals such as saponins, steroids, flavonoids, and phenol, which showed combination effects in terms of larvicidal action to mosquito larvae. Hence, there is a potential of G. zeylanica and G. quaesita aqueous leaf extracts as a key source for the development of an environment‐friendly plant‐based larvicide against Ae. aegypti. Hence, this warrants vector control entities to re‐think “biological wealth for economic prosperity” with environmentally friendly country‐wide control approaches for medically important disease vectors.

Larvicidal activity and chemical composition of four essential oils against Aedes aegypti (Diptera: Culicidae).

The use of botanical insecticides has increased in recent years due to the demand for effective products, particularly against insects resistant to conventional insecticides. Among these is Aedes aegypti, a well-adapted mosquito to urban environments that opportunistically feeds on humans and animals, contributing to the spread of virus. We evaluated the potential of essential oils (EOs) extracted from Eucalyptus citriodora, Eucalyptus staigeriana, Eucalyptus caryophyllus, and Mentha arvensis in terms of their larvicidal activity against Ae. aegypti. EOs' compounds were determined using gas chromatography-mass spectrometry (GC-MS). Bioassays were performed on third instar larvae of Ae. aegypti to evaluate the larvicidal effects of EO dilutions in dimethyl sulfoxide (DMSO) at different concentrations. Mortality rates were observed over a 72-hour period to determine the efficacy of the treatments. Citronellal (86.64) predominated in E. citriodora, limonene in E. staigeriana (41.68), eugenol in E. caryophyllus (87.76), and menthol in M. arvensis (51.53%). EOs exhibited larvicidal activity from 10 ppm, with notable efficacy at 85 ppm, in which those from E. staigeriana and M. arvensis caused maximum mortality to Ae. aegypti larvae. Results revealed distinct efficacy patterns among EOs, with E. staigeriana displaying high toxicity within 24 h, achieving LC50 and LC95 values of 47.04 ppm and 97.35 ppm, respectively. Larvicidal effects within 1 h were observed for E. citriodora and E. caryophyllus. This study underscores larvicidal efficacy against Ae. aegypti, notably E. staigeriana, which had the lowest LC50 value. The findings indicate that the tested samples have potential for use as bioinsecticides.

Potency of Secondary Metabolites from Salacca zalacca, Sonchus arvensis, and Carica papaya against Aedes aegypti L.

Dengue infection is still as a major public health in the world including Indonesia, wherein from January to June showed about 45,387 cases and 432 deaths. There are many prevention and control activities that have been carried out but have not given contented results despite using insecticides. Plants secondary metabolites are confirmed have biological activity and can protecting the plants from an insect pest and diseases. This study proposed that secondary metabolites in several plants have the potential as biolarvicide. This study aimed to determine the potency of secondary metabolites in Salacca zalacca, Sonchus arvensis, and Carica papaya as biolarvicide. Each extract was test in five concentrations of treatment and two controls, negative control using aquadest and positive control using temephos 1%. The third instar larvae of Ae. aegypti mosquito were used in biolarvicide test, with 10 larvae for each treatment and 3 replications for 24 hours. This study revealed that C. papaya extract showed the highest potency as biolarvicide compared to S. zalacca and S. arvensis. The LC50 and LC90 for 24 hours of C. papaya extract were 2.62% and 5.49% respectively.

Impact of larvae of the Asian tiger mosquito Aedes albopictus on larvae of the Culex pipiens complex from Germany in laboratory co-breeding studies.

Since the first detection of the Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) eggs in Germany in 2007, several populations of this species have established in Germany. Although colloquially Ae. albopictus is called an 'invasive species', it is not considered 'invasive' and therefore to be controlled according to the European Union (EU) Environmental and Nature Protection Act since evidence of displacement of native species is missing. To test the competitive potential of Ae. albopictus towards mosquito species native to Germany, laboratory experiments were conducted with larvae of this species and indigenous Cx. pipiens complex species/biotypes. First instar larvae of Ae. albopictus and of one of the native taxa were exposed to different temperatures and fed with different food sources. The ratio of individuals developing into adults as well as the time the larvae needed for development were taken as a measure of competitive outcome. In addition, the size of emerging adults was compared between control and experimental groups. Regarding developmental time, no significant differences were found between treatments and controls while significant differences were found regarding developmental rate and average wing size of individuals. Because no evidence of competitive repression of the native species was found, Ae. albopictus cannot be included in the EU list of invasive species.

Effect of ultraviolet radiation on immature stages of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus mosquitoes.

Understanding the influence of ultraviolet light on organisms is important for examining the hazards of exposure to ultraviolet (UV) light. However, little is known about the biological toxicity of ultraviolet light against mosquitoes, which are regularly exposed to UV light. This study was planned to determine the impact of UV radiation on different aquatic stages of Aedes aegypti, Anopheles stephensi and Culex quinquefaciatus mosquitoes. We exposed I/II instar larvae, III/IV instar larvae and pupae of Ae. aegypti, An. stephensi and Cx. quinquefaciatus mosquitoes to UV radiation of 253 nm wavelength in a closed chamber of 30×30 cm. The exposure was done for different time intervals viz. 1, 2, 3, 4 minutes and so on. Development of larvae/pupae to adult stage was monitored daily and mortality, if any, was recorded. Development of I/II instar larvae of Ae. aegypti and Cx. quinquefasciatus to pupal stage was unsuccessful at an exposure time of one minute while only 1.7% pupation occurred in I/II instar larvae of Ae. aegypti upon similar exposure. When III/IV stage larvae were exposed to UV light, pupal development occurred only at 30seconds and one-minute exposure in An. stephensi and Cx. quinquefaciatus but in Ae. aegypti, no pupation occurred with one-minute exposure. With four-minute UV exposure of pupae, no adult emerged in Ae. aegypti; 33.3% adult emerged in An. stephensi and 66.7% adult emerged in Cx. quinquefaciatus. Our results show that UV radiation results in developmental arrest of Ae. aegypti, An. stephensi and Cx. quinquefaciatus mosquitoes.

Swift synthesis of zinc oxide nanoparticles using unripe fruit extract of Pergularia daemia: An enhanced and eco-friendly control agent against Zika virus vector Aedes aegypti

In this study Pergularia daemia unripe fruits were used to synthesize zinc oxide nanoparticles (Pd-ZnONPs). UV-vis Spectroscopy detected the production of ZnONPs. XRD, FTIR, SEM, and TEM studies were used to characterize the synthesized Pd-ZnONPs. Aedes aegypti (Ae. aegypti) third instar larvae were analyzed to diverse concentrations of Pd-unripe fruit extract and Pd-ZnONPs for 24 hours to assess the larvicidal effect. Mortality was also detected in Ae. aegypti larvae under laboratory conditions, with corresponding LC50 and LC90 values of 11.11 and 21.20 µg/ml respectively. As a result of this study, the levels of total proteins, esterases, acetylcholine esterase, and phosphatase enzymes in the third instar larvae of Ae. aegypti were significantly lower than the control. These findings suggest that Pd-ZnONPs could be used to suppress mosquito larval populations.

Late effects of Beauveria bassiana on larval stages of Aedes aegypti Linneo‎, ‎1762‎ (Diptera: Culicidae).

Aedes aegypti is a culicide that has gained relevance over the years due to its ability to transmit various viruses that cause diseases in humans that all the years cause high mortality rates in the world population. The main problem is that Ae. aegypti has managed to establish and maintain a close relationship with humans and their habitat, which is why the search for alternatives to control vector populations becomes imperative. The objective of the present work was to study the effects of two Beauveria bassiana strains on Aedes aegypti. Third instar larvae of Ae. aegypti in 250 mL plastic containers were inoculated with the GHA and NB3 strains at different concentrations (1.5 × 104, 1.5× 105, 1.5 × 106 and 1.5 × 107 conidia/mL). The NB3 strain presented highest mortality values ​​with 63% in the highest concentration i.e., 1.5 × 107, while for the GHA strain the highest mortality value was 30.7% at the same concentration. The results showed significant difference in mortality with respect to the strain and days post treatment (P = 0.0001), but not with respect to the conidial concentration (P = 0.634). The average mortality of larvae per day for the NB3 for different concentrations ranged from 20 to 25 larvae per day, while for the GHA daily mortality ranged from 5 to 12 larvae. In post-treatment mortality, the highest mortality was recorded in the third stage larvae for the NB3, while for GHA the highest percentage mortality was observed in individuals who managed to reach the adult state. The findings of the current research depicted the noteworthy role of B. bassiana for the management of an important vector of human disease.

Insecticidal efficacy of <i>Rubus steudneri</i> and <i>Rubus apetalus</i> against <i>Aedes</i> (Diptera: Culicidae) and <i>Culex</i> (Diptera: Culicidae) mosquitoes

Introduction and Aim: Rubus steudneri Schweinf. and Rubus apetalus Poir. belonging to the family Rosaceae is one of the ethnomedicinal plants used widely in Ethiopia as food, for construction and as medicine. To the best of our knowledge, insecticidal activity of R. steudneri and R. apetalus has not been investigated so far. In this study, we report insecticidal efficacy of R. steudneri and R. apetalus in terms of larvicidal effect against II and III instar larvae of Aedes and Culex mosquitoes.
 Materials and Methods: The shade-dried and powdered leaves were extracted using methanol by maceration process. Insecticidal activity of leaf extract was determined by larvicidal assay against II and III instar larvae of Aedes and Culex species. LC50 and LC90 values were calculated.
 Results: The leaf extract of both Rubus species exhibited concentration dependent larvicidal effect. II instar larvae were shown to be highly susceptible than III instar larvae. Among leaf extracts, extract of R. steudneri exhibited marked insecticidal activity when compared to extract of R. apetalus as revealed by lower LC50 and LC90 values. Culex larvae displayed marked susceptibility to leaf extracts when compared to Aedes larvae.
 Conclusion: Marked larvicidal effect was observed against larvae of Culex species when compared to Aedes species as indicated by lower LC50 and LC90 values. It is evident that the leaf extracts of both Rubus contain insecticidal principles.

Larvicidal activity and GC-MS analysis of Piper longum L. leaf extract fraction against human vector mosquitoes (Diptera: Culicidae)

Mosquitoes are the vectors for transmitting major public health diseases like dengue, filariasis, and malaria. Among the various mosquito larval control agents, plant extracts and isolated phytocompounds are good alternatives to control vector mosquitoes. The objective of this study is to test the efficacy of leaf extract fraction prepared from the locally available plant, Piper longum L in decimating the larvae of Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Piper longum leaf extract fraction was isolated through column chromatographic separation and phytochemical analysis was carried out by standard procedures. The larvicidal assay was carried out following WHO methods, and the P. longum fraction was tested at various concentrations (10-80µg/dl) on the third instar larvae of Ae. aegypti, An. stephensi, and Cx. quinquefasciatus. The 24h LC50, LC90 values were as determined using probit analysis. GC-MS analysis was done for the identification of bio-active compounds present in the specific P. longum leaf fraction. The fraction of P. longum leaf extract contains secondary metabolites such as alkaloids, glycosides, saponins, phytosterols, diterpenes, triterpenes, phenols, tannins, steroids, and terpenoids. The LC50 and LC90 values were 38.96 and 41.53; 45.06, and 71.16; 72.02 and 76.80 µg/dl against Ae. Aegypti, An. stephensi, and, Cx. quinquefasciatus respectively. Twenty-nine phytocompounds were identified by GC-MS. The present results suggested that the fraction of P. longum leaf extract checked for mosquito larvicidal activity had an excellent potential for controlling selected human vector mosquitoes.

Green synthesis of silver nanoparticles from aqueous extract of Ctenolepis garcini L. and assess their possible biological applications

The AgNPs synthesized from aqueous leaf extract of Ctenolepis garcini were observed spectrophotometrically (at 415 nm) reflecting sharp peaks. The X-Ray Diffraction (XRD) data have shown four distinct diffraction peaks that were directly related to the crystal structure of the silver molecule. The noticeable peaks such as the peaks at 1741.51 cm−1, 1630.07 cm−1, 1383.11 cm−1, 769.73 cm−1, and 703.76 cm−1 were noticed in the synthesized AgNPs using Fourier-transform infrared spectroscopy (FTIR). About 20−50 nm sized and cubic shaped nanoparticles were observed under Transmission Electron Microscopy (TEM) analysis. Furthermore, the Energy Dispersive X-ray (EDX) analysis identified the chemical nature of the AgNPs. These synthesized AgNPs had an excellent insecticidal activity against the I-IV instar larvae of Ae. Aegypti. Furthermore, it showed good antibacterial activity against Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa and Shigella boydii. The plant based AgNPs revealed excellent DPPH (71.25 %) and ABTS (64.15%) radical scavenging activities. The MTT assay results stated that the synthesized nanoparticles had the potential to repress the propagation of the HepG2 cell line with an IC50 of 33.78 ± 1.32 μg mL−1. The attained results suggested that the C. garcini based AgNPs would be a potential candidate for various biological applications. This green extract based AgNPs production could be significant to produce low cost and ecofriendly nanoparticles with multi-potentiality.

Repellent, larvicidal and adulticidal activities of essential oil from Dai medicinal plant Zingiber cassumunar against Aedes albopictus

Zingiber cassumunar is an important plant used in traditional medicine and as a natural mosquito repellent. However, the compounds responsible for the repellent activity of the plant are still unknown. The aim of the study is to identify the components of Z. cassumunar essential oil that show repellent activity against Aedes albopictus. We also evaluated the larvicidal and adulticidal activities of Z. cassumunar essential oil against Ae. albopictus. In-cage mosquito repellent experiments showed that Z. cassumunar essential oil possessed moderate repellent activity with a minimum effective dose (MED) of 0.16 ± 0.01 mg/cm2, compared to reference standard N,N-diethyl-3-methylbenzamide (DEET, 0.03 ± 0.01 mg/cm2). Bioassay-guided fractionation identified the major active compound of Z. cassumunar essential oil as (−)-terpinen-4-ol (1) (MED: 0.19 ± 0 mg/cm2). We also found that Z. cassumunar essential oil showed moderate larvicidal activity against first instar larvae of Ae. albopictus with a LC50 (50% lethal concentration) of 44.9 μg/L after 24 h. Fumigation bioassays showed that Z. cassumunar essential oil exhibits moderate adulticidal activity against Ae. albopictus with a LC50 of 5.44%, while (−)-terpinen-4-ol showed significant adulticidal activity with a LC50 of 2.10% after 24 h. This study verifies that the Z. cassumunar essential oil has mosquito repellent activity, and that (−)-terpinen-4-ol is mainly responsible for this activity. Furthermore, this study provides scientific support for the folk usage of Z. cassumunar essential oil as mosquito repellent and indicates that Z. cassumunar essential oil and (−)-terpinen-4-ol can be used as plant-derived repellents and insecticides for mosquito control.

The Effect of Temephos to Mortality and Life Level of Aedes aegypti mosquitoes

Temephos is an insecticide active ingredient often used by a community as Dengue Hemorrhagic Fever (DHF) vector control in imago. The development of Ae aegypti is influenced by biotic and abiotic factors. This study aimed at determining the effects of temephos concentration on mortality and a life level of Ae aegypti at some concentration tests.The experimental design used in this study was Complete Random Design (CRD). This study involved temephos as the active ingredient and third instar Ae. Aegypti larvae originating from Pangandaran Regency. Data analysis used an ANOVA test with 5 treatments and 5 replications. The results showed that there was any influence of concentration towards a number of mortality, a life level, morphology of larvae, pupae and imago, a number of males and females, and a number of eggs hatchability. Temephos concentration affected the mortality of third instar larvae of Ae. aegypti with temephos concentration of 0.019 ppm, 0.069 ppm, 0.105 ppm, and 0.140 ppm and affected a life level of Ae. aegypti with biological parameters.

CHEMICAL COMPOSITION, LARVICIDAL ACTIVITY AND RESIDUAL EFFECT OF Pterodon polygalaeflorus (BENTH.) BENTH. (FABACEAE) FRUIT OIL EXTRACTS AGAINST Aedes aegypti (DIPTERA: CULICIDAE)

The purpose of this study was to investigate the larvicidal activity of Pterodon polygalaeflorus oil extract against the mosquito vector Aedes aegypti. For this, crushed P. polygalaeflorus fruit underwent solvent extraction to obtain the oil extract. The chemical characterization was performed by gas chromatography coupled to mass spectrometry. For the bioassays third instar larvae of Ae. aegypti were utilized. Tests were carried out to determine the larvicidal activity and the residual effect under laboratory conditions, as well as field screening (small scale).The major components of P. polygalaeflorus oil extract were, respectively, E-caryophyllene, germacrene D and bicyclogermacrene. Lethal concentrations of 50% and 90% were 36.5 and 64.8 μg/mL respectively. The solution presented a residual effect for seven days and the efficiency of the product was preserved under field conditions. The results encourage continuing studies with the oil extract of P. polygalaeflorus as a research target for bioinsecticides.KEY WORDS: Bioinsecticide; sucupira; terpenes; vector control.

Mosquito larvicidal efficacy of methanolic extract from seeds of Datura inoxia Mill against Aedes aegypti (Linn.) with insight into GC-MS analysis

The GC-MS analysis revealed the presence of 38 components, the major chemical constituents in the extract were atropine (20.55%), cis-13, 16-docasadienoic acid (19.73) n-hexane (15.67%), 1-chloro-1-fluoro ethane (6.84%), 9, 12-octadecadienoic acid (5.10%), lup-20(29)-en-3-ol, acetate (5.01%), scopolamine (2.87%). Bioassay experiments using methanolic extract from seeds of Datura inoxia Mill showed significant larvicidal activity against third instar larvae of Aedes aegypti with LC50 and LC90 values of 72.44 and 275.42 ppm, respectively.

Aktivitas Larvasida Berbagai Pelarut pada Ekstrak Biji Kayu Besi Pantai (Pongamia pinnata) terhadap Mortalitas Larva Aedes spp.

The use of chemical compound as a way to control DHF may cause harmful effect for humans and environment. It is necessary to develop biological insecticides derived from plants such as Pongamia pinnata. This study was designed to determine the larvicidal activity of P. pinnata seeds extract with various solvent on Aedes spp. This study was an experimental research with post test only control group design. Materials used in the research were P. pinnata seed extracts with water, methanol and chloroform solvents of concentration; 100 ppm, 200 ppm, 300 ppm, 400 ppm and 500 ppm. Larvicidal activity of P. pinnata seed extracts was tested against third instar larvae of Ae. aegypti and Ae. albopictus, 24 hours observation was carried out within each treatment.very test was repeated for 3 times. The result showed that larvae mortality was found in the methanol extract with LC50 value of 141.88 ppm for Ae. aegypti and 108.19 for Ae. albopictus, and in the chloroform extract with LC50 value of 346.06 ppm for Ae. aegypti and 222.29 ppm for Ae. albopictus. The water extract of P. pinnata seed was not effective as a larvicidal, while methanol and chloroform of P. pinnata seed extracts act as potential natural insecticide.

Screening of phytochemical and pharmacological activities of Syzygium caryophyllatum (L.) Alston

BackgroundThe systematic screening of plant species with the purpose of discovering new bioactive compounds is prerequisite for any bioprospecting study. Therefore the present study was carried out to assess the phytochemical content and the evaluation of in vitro antioxidant, antibacterial, larvicidal and antidiabetic activities of the methanol extracts of S.caryophyllatum bark, leaves, fruit pulp and seeds.MethodsThe quantitative estimation of total phenol, flavonoid and tannin content of the extracts of S. caryophyllatum bark, leaf, fruit pulp and seeds were analyzed by using standard methods. The present study also conducted to screen antioxidant (DPPH, ABTS assays), antimicrobial, antidiabetic (in vitro α-amylase and α-glucosidase inhibitory assays) and larvicidal (against fourth instars larvae of Aedes aegypti and Culex quinquefasciatus) activities of methanol extract of S. caryophyllatum.ResultsThe results of quantitative phytochemical analysis revealed the presence of maximum amount of phytoconstituents such as phenol, flavonoids and tannins in the leaf, bark and seed extract when compared to fruit pulp extracts. Free radical scavenging activity indicated that methanol bark, leaves, fruit and seeds extracts has significant free radical scavenging ability on DPPH with percentage inhibition of 88.15%, 81.31%, 75.24% and 83.36% respectively. The in vitro α-amylase and α-glucosidase inhibitory studies of the methanol crude extracts of four different plant parts of S. caryophyllatum (Bark, leaf fruit pulp and seed) showed good inhibitory activities in concentration dependent manner. The maximum percentage inhibitory activity of 78.03% was showed at concentration of 500 μg/ml seed extracts followed by bark (78.03%), leaf (69.4%) and fruit pulp (56.9%) at the same concentration. While the percentage inhibitory activity of four extracts also showed potent inhibition of α-glucosidase; maximum inhibition exhibited at the concentration of 100 μg/ml by bark extract (80.9%) compared with other extracts, leaf (78.2%), seed (77.59%) and fruit pulp (63.35%). The leaf essential oil and four extracts showed significant mortality against fourth instars larvae of Ae. aegypti and Cx. quinquefasciatus respectively.ConclusionThus the present study suggests that S.caryophyllatum plant parts can be used as natural antioxidant source to prevent diseases associated with free radicals. Also, this plant can be a good source for further purification studies for isolation and characterization of compounds related to these antioxidants, antidiabetic and antibacterial activities.

Larvicidal Activity of Silver Nanoparticles Synthesized Using Extracts ofAmbrosia arborescens(Asteraceae) to ControlAedes aegyptiL. (Diptera: Culicidae)

The mosquito speciesAedes aegyptiis the primary vector of dengue, chikungunya, and Zika infections worldwide. Since effective vaccines or drugs are not available for the prevention and/or treatment of these pathologies, vector control has been adopted as the main approach to reduce their transmission. To controlAedespopulations, the most commonly used tool is the application of chemical insecticides and, despite their effectiveness, indiscriminate use of these chemicals has led to high operational costs, appearance of resistant populations, and adverse nontarget effects. Plant-derived insecticides may be an eco-friendly, cost-effective, and safe biocontrol alternative. The present study was carried out to evaluate the larvicidal activity of leaf extracts ofAmbrosia arborescensand green-synthesized silver nanoparticles (AgNPs) using aqueous extracts obtained from this plant against third instar larvae ofAe. aegypti. To test this, larvae were exposed for 24 h to the aqueous plant extract at 1500, 3000, 4500, and 6000 ppm and the plant-synthesized AgNPs at 0.2, 0.3, 0.4, and 0.5 ppm. In laboratory assays, AgNPs were more toxic (LC50 = 0.28 ppm; LC90 = 0.43 ppm) than the plant extract (LC50 = 1844.61 ppm; LC90 = 6043.95 ppm). These results suggest thatA. arborescensaqueous extract and green-synthesized silver nanoparticles produced from those extracts have the potential to be developed into suitable alternative tools useful for the control ofAe. aegyptipopulations.

PUPAL EMERGENCE INHIBITION ACTIVITY OF ACALYPHA INDICA LEAF EXTRACT AGAINST DENGUE VECTOR, AEDES ALBOPICTUS MOSQUITO

Objective: To investigate the larvicidal activities of six varying extracts of Acalypha indica (A. indica) leaves from family Euphorbiaceae against the dengue mosquito vector, Aedesalbopictus (Ae. albopictus) in laboratory.Methods: Leaves from the study plants were separated, air dried in room temperature, grounded and extracted with different solvents (petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous) by solvent apparatus and aqueous extract by maceration method. The extra solvents were evaporated to obtain crude extracts by using rotary evaporator. The crude extracts of six different solvents were dissolved in dimethyl sulphoxide (DMSO) to prepare test dosages of 1000, 2000, 3000, 4000 and 5000 ppm. Third instar larvae of Ae. albopictus were exposed to 1000, 2000, 3000, 4000 and 5000 ppm concentrations of petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous extracts of A. indica and compared with control to determine the larvicidal effects. Larval bioassays were carriedout according to World Health Organisation (WHO) procedures. The rate of larval mortality was recorded after 24h and 48 h of time exposure. Three duplicate trials were made for each tested dosage. IC50 and IC90 values were calculated by using probit analysis.Results: Based on probit analysis result the 24h and 48h LC50 and LC90 of petroleum ether extract of A. indica against Ae. albopictus was found to be 2805.43 ppm and 2376.11 ppm, 3825.14 ppm and 3327.8 ppm, respectively. An LC50 and LC90 value of chloroform extracts of A. indicaa gainst third instar larvae was found to be 2276.5 ppm and 4015.8 ppm (24h), 2213.36 ppm and 3430.43 ppm (48h), respectively. An LC50 value of 4472.17 ppm and 2469.61 ppm, and LC90 value of 4215.84 ppm was obtained on ethylacetate extract treatment against Ae. albopictus for 24h and 48h exposure, respectively. The 24h and 48 h LC50 and LC90 values of n-butanol extracts of A. indica was found to be 2777.88 ppm and 3628.19 ppm, 2225.61 ppm and 2518.86 ppm, respectively. In the present study, the larvicidal bioassays demonstrated that the n-butanolextract was most effective with 100% mortality against larvae of Ae. albopictus at 3000, 4000 and 5000 ppm compared to other extracts. All other extracts (petroleum ether, chloroform and ethyl acetate) of A. indica at high concentration (4000 ppm and 5000 ppm) manifested a significant (P<0.01 and 0.05) knock down effect of 100% moratality after 24h and 48h exposure. While the third instar lavae of Ae. albopictus were found to be most susceptabile and produced no mortality to ethanol and aqueous extract at varying parts per million. Conclusion: A. indica leaf extract was tested for the first time against dengue vector Ae. albopictus and the results revealed that A. indica can be used to control dengue vector. Further this extract needs to be evaluated under field conditions for proper exploitation of Ae. albopictus mosquito larvae. Thus, the present study provided a first report on A. indica as a prompting mosquito larvicidal activity and can be considered for further investiagtions such as formulation of bioinsecticides to control Ae. albopictus populations

Larvicidal activity of some fungal extracts onAedes caspiusandCulex pipiens(Diptera: Culicidae)

AbstractA preliminary study was conducted to evaluate the effects of nine methanol fungal extracts on fourth instar larvae ofAedes caspiusandCulex pipiens(Diptera: Culicidae). None of the extracts tested showed larvicidal activity except for thePaecilomyces lilacinusextract, which showed 100 % mortality against the larvae ofAe caspiusafter 24 h. The LC50values of theP. lilacinusextract after 24 h were 190.66 μg/mL againstAe. caspiusand 254.25 μg/mL againstCx. pipiens, respectively. After 48 h, meanwhile, the LC50values were 65.70 and 164.13 μg/mL, respectively. Histological analysis of the midgut of the treated larvae ofAe. caspiusandCx. pipiensrevealed changes such as cell destruction, spacing between the cells and disruption of the microvilli, resulting in an appearance of vacuolization in the midgut. This article is the first report of the use ofP. lilacinusextract for the control ofAe. caspiusandCx. pipienslarvae and the data obtained may help to provide a better understanding of the mode of action ofP. lilacinusas an insecticide against mosquito larvae.

Predation efficiency of copepods against the new invasive mosquito species Aedes koreicus (Diptera: Culicidae) in Italy

Aedes koreicus (Edwards) (Diptera: Culicidae) is an invasive mosquito species and potential vector of pathogens which has recently colonised a large part of northeastern Italy and other European countries. Several species of cyclopoid copepods are natural predators of mosquito larvae and can be useful biological control agents in artificial containers used as breeding sites by Aedes mosquitoes. However, to ensure behavioural efficiency of these agents, and to avoid the introduction of non-native species, predatory copepods should be selected from the local fauna. In this study, we evaluated the predation efficiency under laboratory conditions of two locally bred populations of cyclopoid copepod species, Macrocyclops albidus (Jurine, 1820) and Mesocyclops leuckarti (Claus, 1857) (Copepoda: Cyclopoida), which are two of the most common European species of cyclopoid copepods, against Ae. koreicus larvae. Predation experiments were also conducted with Aedes (Stegomyia) albopictus (Skuse) as a “reference”. In each predation test, one adult female copepod was placed with 50 first instar larvae of a single mosquito species in a Petri dish filled with 10 mL of water. After 24 hours, the mean number (± standard error) of first instar larvae killed by one M. albidus female was 18.6 ± 1.3 Ae. koreicus and 20.9 ± 1.3 Ae. albopictus, and the mean number killed by one M. leuckarti female was 25.8 ± 2.8 Ae. koreicus and 36.1 ± 4.2 Ae. albopictus. In addition, M. leuckarti was slighly less effective against Ae. koreicus than against Ae. albopictus after 48 hours, probably because first instar larvae of Ae. koreicus were larger than first instar larvae of Ae. albopictus. Our findings indicate for the first time that copepods are effective predators of first instar larvae of Ae. koreicus.