Fourth Instar Larvae Of Ae Research Articles

Evaluation of larvicidal activity of the essential oil of Allium macrostemon Bunge and its selected major constituent compounds against Aedes albopictus (Diptera: Culicidae).

BackgroundDuring the screening programme for new agrochemicals from Chinese medicinal herbs and local wild plants, the essential oil of dried bulbs of Allium macrostemon Bunge (Liliaceae) was found to possess larvicidal activity against mosquitoes. The aim of this research was to determine the larvicidal activity of the essential oil and its major constituent compounds against the larvae of the Culicidae mosquito, Aedes albopictus.MethodsEssential oil of A. macrostemon was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mass spectrometry (GC-MS). The activity of the essential oil and its two major constituents were evaluated, using World Health Organization (WHO) procedures, against the fourth instar larvae of Ae. albopictus for 24 h and larval mortalities were recorded at various essential oil/compound concentrations ranging from 9.0 - 150 μg/ml.ResultsThe essential oil of A. macrostemon exhibited larvicidal activity against the early fourth instar larvae of Ae. albopictus with an LC50 value of 72.86 μg/ml. The two constituent compounds, dimethyl trisulfide and methyl propyl disulfide possessed strong larvicidal activity against the early fourth instar larvae of Ae. albopictus with LC50 values of 36.36 μg/ml and 86.16 μg/ml, respectively.ConclusionThe results indicated that the essential oil of A. macrostemon and its major constituents have good potential as a source for natural larvicides.

Clerodendron inerme Gaertn. plant as an effective natural product against dengue and filarial vector mosquitoes

ObjectiveTo investigate insecticidal properties of organic solvent extracts of Clerodendron inerme (C. inerme) leaves against larval stages of Aedes aegypti (Ae. aegypti) and Culex quinquefasciatus (Cx. quinquefasciatus) mosquito species. MethodsThe sundried leaf powder of C. inerme was subjected for extraction using organic solvents viz. methanol, chloroform, petroleum ether and hexane extract, and were tested against third/fourth instar larvae of Ae. aegypti and Cx. quinquefasciatus species in accordance with WHO standard methods. Experiments were conducted in four replicates with control group containing water alone and positive control group containing respective solvent (dimethylsulfoxide/acetone) used for dissolving the extracts. ResultsAmong the four solvent extracts, hexane extract has effective growth disruptive activity against Ae. aegypti, and showed positive tests for presence of four groups of phytochemical constituents viz. tanin, phytosteriod, terpenoid and cardiac glycoside. The hexane extract was tested against field collected filarial vector Cx. quinquefasciatus larvae for growth disruptive activity. Adult emergence inhibition values for 50 percent suppression (EI50) of the tested population for methanol, chloroform, petroleum ether and hexane extracts treated against third instar larvae of Ae. aegypti were found to be 37.45, 14.79, 2.56 and 1.96 mg/L respectively, while hexane extract treated against Cx. quinquefasciatus was found to be equally effective with EI50 value of 3.74 mg/L. Hexane extract treated against fourth instar larvae of Ae. aegypti and Cx. quinquefasciatus showed EI50 values of 8.07 and 19.55 mg/L respectively in comparison with that of standard insect growth regulator methoprene demonstrating EI50 value of 0.05 mg/L. Besides, the hexane extract was also found to possess toxic effect against non-target organism Gambusia affinis (a bio-control agent), however, the lethal concentration (LC50=172.7 mg/L for 24 h) against Gambusia affinis was much higher in comparison with that of tested concentrations against Ae. aegypti and Cx. quinquefasciatus. ConclusionsWe conclude from the present investigation that the hexane extract of C. inerme has positive implications for its consideration in integrated control of dengue/filarial vectors due to their ecological distinctness in comparison with non-target organism and further due to ecofriendly nature of the extract in terms of easy biodegradability.

Larvicidal and irritant activities of hexane leaf extracts of Citrus sinensis against dengue vector Aedes aegypti L.

Objective To assess the larvicidal and irritant activities of the hexane extracts of leaves of Citrus sinensis ( C. sinensis) against the early fourth instars and female adults of Aedes aegypti ( Ae. aegypti) Methods The larvicidal potential of the prepared leaf extract was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 h and LC 50 and LC 90 values were calculated. The efficacy of extract as mosquito irritant was assessed by contact irritancy assays. Extract-impregnated paper was placed on a glass plate over which a perspex funnel with a hole on the top was kept inverted. Single female adult, 3-day old unfed/blood-fed, was released inside the funnel. After 3 min of acclimatization time, the time taken for the first take-off and total number of flights undertaken during 15 min were scored Results The citrus leaf extracts from hexane possessed moderate larvicidal efficiency against dengue vector. The bioassays resulted in an LC 50 and LC 90 value of 446.84 and 1 370.96 ppm, respectively after 24 h of exposure. However, the extracts were proved to be remarkable irritant against adults Ae. aegypti, more pronounced effects being observed on blood-fed females than unfed females. The extract-impregnated paper was thus proved to be 7-11 times more irritable as compared with the control paper. Conclusions The hexane extracts from C. sinensis leaves are proved to be reasonably larvicidal but remarkably irritant against dengue vector. Further studies are needed to identify the possible role of extract as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the extract could help in formulating strategies for mosquito control.

Bioefficacy of Mentha piperita essential oil against dengue fever mosquito Aedes aegypti L

Objective To assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant, Mentha piperita ( M. piperita) against the larval and adult stages of Aedes aegypti ( Ae. Aegypti). Methods The larvicidal potential of peppermint oil was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 and 48 h, and LC 50 and LC 90 values were calculated. The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique. The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol. The mosquito bites on both the arms were recorded for 3 min after every 15 min. The experiment continued for 3 h and the percent protection was calculated. Results The essential oil extracted from M. piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC 50 and LC 90 value of 111.9 and 295.18 ppm, respectively after 24 h of exposure. The toxicity of the oil increased 11.8% when the larvae were exposed to the oil for 48 h. The remarkable repellent properties of M. piperita essential oil were established against adults Ae. aegypti. The application of oil resulted in 100% protection till 150 min. After next 30 min, only 1-2 bites were recorded as compared with 8-9 bites on the control arm. Conclusions The peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.

Insecticidal and Cytotoxic Activities of Extracts of <I>Cacalia tangutica</I> and Its Two Active Ingredients Against <I>Musca domestica</I> and <I>Aedes albopictus</I>

The insecticidal activities of extracts from different parts of Cacalia tangutica (Franch.) H.-M. and two active ingredients, friedelin and stigmasterol, against Musca domestica L., Aedes albopictus (Skuse), and Spodoptera litura (F.) cells (SL cells) are reported. Extracts from leaves, flowers, and roots are highly active against adult M. domestica and the fourth-instar larvae of Ae. albopictus. The foliar extract was the most active with LC50 values of 1.74 mg/g and 196.94 microg/ml against adult M. domestica and fourth-instar larvae of Ae. albopictus, respectively. Extracts from stems were the least active. Friedelin and rotenone were highly active and equitoxic to these two insect species. The LC50 value of friedelin in adult M. domestica 48 h after treatment was 129.27 microg/g. The activity of stigmasterol on these two insect species was not obvious. However, the cytotoxicity of stigmasterol to S. litura cells was significantly greater than that of either friedelin or rotenone. At 25 microg/ml, the mortality of cells 24 h after treatment with stigmasterol was 23.0%. In contrast, friedelin and rotenone at the same concentration produced 16 and 18% mortality, respectively. Our results indicate differences between cytotoxicity in vitro and insect toxicity in vivo.

Insecticidal activities of leaf and twig essential oils from Clausena excavata against Aedes aegypti and Aedes albopictus larvae

The current study investigates, for the first time, the mosquito larvicidal activities of leaf and twig essential oils from Clausena excavata Burm. f. and their individual constituents against Aedes aegypti L. and Aedes albopictus Skuse larvae. The yields of essential oils obtained from hydrodistillation were compared, and their constituents were determined by GC-MS analyses. The LC(50) values of leaf and twig essential oils against fourth-instar larvae of Ae. aegypti and Ae. albopictus were 37.1-40.1 microg mL(-1) and 41.1-41.2 microg mL(-1) respectively. This study demonstrated that C. excavata leaf and twig essential oils possess mosquito larvicidal activity, inhibiting the growth of mosquito larvae for both species at a low concentration. In addition, results of larvicidal assays showed that the effective constituents in leaf and twig essential oils were limonene, gamma-terpinene, terpinolene, beta-myrcene, 3-carene and p-cymene. The LC(50) values of these constituents against both mosquito larvae were below 50 microg mL(-1). Among these effective constituents, limonene had the best mosquito larvicidal activity, with LC(50) of 19.4 microg mL(-1) and 15.0 microg mL(-1) against Ae. aegypti and Ae. albopictus larvae respectively. The findings suggested that the essential oils from Clausena excavata leaf and twig and their effective constituents may be explored as a potential natural larvicide.