Ovicidal Agent Research Articles

The ethanol extract of Sargassum duplicatum as an ovicidal agent against Aedes aegypti

Dengue hemorrhagic fever (DHF) is a major health concern in tropical and subtropical countries. Indonesia has DHF cases perennially every year. On the other hand, Indonesia is abundant with seaweed (Sargassum duplicatum), which can be found across its seashore. The macroalgae contains secondary metabolites with ovicidal activity; hence, it has the potential to be utilized in suppressing the Aedes aegypti. The aim of this study was to determine the ovicidal activity of S. duplicatum against the Ae. aegypti eggs. The algae were macerated with ethanol 70% before being subjected to qualitative phytochemical screenings. The ovicidal tests were conducted with an extract concentration of 50 ppm, 100 ppm, 500 ppm, 1000 ppm, and 1500 ppm, while distilled water was used as the control. The hatchability of Ae. aegypti was observed 24 hours a day for 4 days and the larval development was investigated under a microscope. Phytochemical screenings revealed that the extract was positive containing alkaloids, flavonoids, steroids, saponins, and phenols. The hatchability of Ae. aegypti eggs were significantly reduced following the S. duplicatum extract exposure for four days (p=0.000). The extract had LC50 of 828.653 ppm and LC50 of 1786.09 ppm for the ovicidal activity against Ae. aegypti eggs. The concentration of ethanol extract of S. duplicatum did not affect the mosquito development from larvae to adult stage (p=0.263). Further research is needed to explore the effect of specific compounds contained in the S. duplicatum and investigate their ovicidal potential.

Ovicidal toxicity of plant essential oils and their major constituents against two mosquito vectors and their non-target aquatic predators

Plant essential oil (EO) is a natural alternative to synthetic chemical insecticides for mosquito control. EOs from Citrus aurantium L., Cymbopogon citratus (Stapf.), and Cinnamomum verum (J. Presl.) were selected for topical assay of their ovicidal activity against Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse). Their efficacy was compared to that of 1% (w/w) temephos. In addition, their non-toxicity against aquatic mosquito predators, Poecilia latipinna and Poecilia reticulata, was tested. Found by GC–MS analysis, the major constituent of C. verum EO was trans-cinnamaldehyde, of C. aurantium EO was d-limonene, and of C. citratus EO was geranial. Both C. verum EO and trans-cinnamaldehyde at a high concentration (30,000 ppm) exhibited high ovicidal activity against Ae. aegypti and Ae. albopictus eggs after 48 h of incubation with an inhibition rate of 91.0–93.0% for C. verum EO and 96.7–95.2% for trans-cinnamaldehyde. The combination of C. verum EO + geranial exhibited the strongest synergistic inhibition activity (100%) against the two mosquito vectors and was five times more effective than temephos. Moreover, they were not toxic to the non-target fishes. As a safe ovicidal agent for mosquito egg control, the combination of C. verum EO + geranial has excellent potential.

Myracrodruon urundeuva leaf lectin damages exochorionic cells and binds to the serosal cuticle of Aedes aegypti eggs.

In recent years, lectins have been identified as alternative agents against Aedes aegypti during the aquatic phases of its life cycle. For example, chitin-binding lectin from Myracrodruon urundeuva leaf (MuLL) can function as a larvicide. In this study, we investigated whether MuLL can also act as an ovicide against this insect. Aedes aegypti eggs were incubated with MuLL for 72h to determine the concentration at which the hatching rate reduces by 50% (EC50). The effects of MuLL on the egg surface structure were evaluated using scanning electron microscopy (SEM), and the possible interaction of MuLL with the internal structures of eggs and embryos was investigated using MuLL-fluorescein isothiocyanate (FITC) conjugate. MuLL acted as an ovicidal agent with an EC50 of 0.88mg/mL. The SEM analysis revealed that eggs treated with MuLL for 24 and 48h no longer had tubercles and did not show a well-defined exochorionic network. In addition, deformation and degeneration of the surface were observed after 72h. Fluorescence microscopy showed that MuLL penetrated the eggs 48h after incubation and was detected in the upper portion of the embryo's gut. After 72h, MuLL was observed in the serosal cuticle and digestive tract. In conclusion, MuLL can function as an ovicidal agent against A. aegypti through damage to the surface and internal structures of the eggs.

Activity of terpenes derived from essential oils against Sarcoptes scabiei eggs

BackgroundThe limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment. Several essential oils or their respective components have proved to be active against the eggs of arthropods, mainly lice and ticks. Information on the activity of these oils and/or components against the eggs of mites remains very limited. The aim of this study was to assess the activity of six terpenes (carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool) commonly found in essential oils against the eggs of Sarcoptes scabiei.MethodsSarcoptes eggs were exposed to paraffin oil containing 1, 2.5, or 5% of each terpene tested. After a 12-h exposure period, the eggs were washed and placed in paraffin oil for hatching. Embryonic development following treatment was assessed every day to determine the stage of developmental arrest.ResultsThe median effective concentration to obtain 50% egg mortality (EC50) was 0.5, 0.9, 2.0, 4.8, 5.1 and 9.8% for carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool, respectively. The microscopic images of eggs after each treatment indicated that these six terpenes may act by penetrating through the aeropyles on the egg surface.ConclusionsIn conclusion, carvacrol, eugenol and geraniol possess significant ovicidal activities, which should be considered as promising ovicidal agents for the treatment of scabies.Graphical

Polyphenolic extracts from the olive mill wastewater as a source of biopesticides and their effects on the life cycle of the Mediterranean fruit fly Ceratitis capitata (Diptera, Tephriditae)

The Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) (Diptera, Tephriditae) is an important pest in the Mediterranean region causing severe economic losses. Currently, pyrethroids are the most common insecticides used in the control of the Medfly. However, the demand for biopesticides is growing due to the necessity to limit the use of hazardous chemical pesticides in the context of the integrated pest management. In this context, a valid alternative is the use of plant derived pesticides with a selective action against target pests and a shorter persistence in ecosystems.Among plant products, olive tree phenolic and polyphenolic compounds show potent bioactive properties as insecticides and growth regulators. The olive mill wastewater is an important source of these compounds.We are reporting here that the polyphenolic fractions of the olive mill wastewater, show ovicidal effects in terms of reduction of the hatching rate, whereas the larval development is not affected by the treatments.On the adults, we show that selected fractions induce a complete block of the fecundity of the females probably due to an induced disruption of the oogenesis.These results suggest that the polyphenolic fractions derived from the olive mill wastewater can be used as a strong natural chemosterilant against the Mediterranean Fruit fly and can be considered as a putative ovicidal agent.

Toxicology study of fraxinellone as ovicidal agents against Mythimna separata Walker and Bombyx mori Linaeus.

Fraxinellone is a naturally occurring degraded limonoid isolated from many species of plants in Meliaceae and Rutaceae. Besides structural modification of the lead compounds, the toxicology study of the lead compounds is also a very important procedure to develop insecticidal agents. Herein the toxicology study of fraxinellone was carried out as the ovicidal agent against the eggs of two lepidopteran insects Mythimna separata Walker and Bombyx mori Linaeus. Fraxinellone selectively exhibited an ovicidal activity against the eggs of M.separata. After treatment with fraxinellone, the eggshells of M.separata were shrinked, whereas those of B.mori had no obvious change. The dynamic process of M.separata embryo development demonstrated that the distinct difference between the treated eggs and the control ones was obvious at the second day after treatment, especially, the control embryo finished blastokinesis, whereas the treated ones were still laid at pre-reversion status and a lot of yolk can be seen around the embryo. It ultimately resulted in the eggshell withered and the egg hatching inhibited.

Lemongrass (Cymbopogon citratus) oil: A promising miticidal and ovicidal agent against Sarcoptes scabiei.

BackgroundEssential oils may represent an alternative strategy for controlling scabies, a neglected tropical disease caused by the infestation of mite from the species Sarcoptes scabiei. Lemongrass (Cymbopogen citratus) oil is reported to possess pharmacological properties including antiparasitc, antioxidant, antimicrobial and anti-inflammatory. The aim of the present study was to assess the potential efficacy of lemongrass oil against the mites and eggs of Sarcoptes scabiei.Methodology/Principal findingsMass spectrometry analysis confirmed that the main component presented in lemongrass oil was citral. Lemongrass oil at concentrations of 10% and 5% killed all Sarcoptes mites within 10 and 25 min, respectively. The median lethal concentration value was 1.37%, 1.08%, 0.91%, 0.64%, and 0.48% at 1, 3, 6, 12, and 24 h, respectively. Lemongrass oil at all concentrations (10%, 5%, 1%, 0.5%, 0.1%) was able to significantly decrease the hatching rate of Sarcoptes eggs.Conclusions/SignificanceLemongrass oil should be considered as a promising miticidal and ovicidal agent for scabies control.

ОРГАНИЗАЦИЯ И ПРОВЕДЕНИЕ ЭКСПЕРИМЕНТАЛЬНОГО ИССЛЕДОВАНИЯ ПО ОПРЕДЕЛЕНИЮ ОВИЦИДНОЙ АКТИВНОСТИ ДЕЗИНВАЗИОННОГО СРЕДСТВА

Developed and implemented methodological approaches to the experimental determination of the effectiveness (ovicidal activity) of agents proposed for disinfection of environmental components. It is shown that the study can contribute to the creation of unified documented procedures (regulations) for the study and assessment of the ovicidal activity of disinfectants and their compliance with the stated requirements, which, in turn, will make it possible to form a national register of ovicidal agents used for disinfection of environmental objects (objects).

PSII-37 Determining the possible anthelmintic properties of allicin and pumpkin seed oil for mitigation of anthelmintic resistance found in gastrointestinal nematodes infecting ruminants

Abstract Anthelmintics are a widely utilized treatment option for gastrointestinal nematodes infecting ruminants. Recently, these parasites have exhibited increasing resistance towards these drugs. Haemonchus controtus, a gastrointestinal nematode commonly found in small ruminants, has developed resistance towards multiple classes of anthelmintics, leading to huge economic losses worldwide. There are few novel drugs currently being developed, but certain plant-derived products have demonstrated anthelmintic properties when administered in various forms to ruminants. By utilizing these plant products, producers have the opportunity to decrease the rate of development of anthelmintic resistance, and prevent eggs from hatching when excreted by infected livestock. Therefore, it is hypothesized that specific plant-derived products will act as ovicidal agents in H. contortus eggs. The objective of this study was to determine the ovicidal activity of allicin (from Allium sativum) and pumpkin seed oil (PSO). H. contortus eggs were extracted from a pooled fecal sample of Boer and Spanish goats naturally infected with H. contortus. The eggs were then exposed to allicin or PSO at different concentrations. Experiments were replicated four times per concentration. To determine ovicidal activity, samples were observed for unhatched eggs and hatched worms for 24 hours. The 1:100 allicin dilution treatment tended (P = 0.053) to inhibit hatching more than the control. Furthermore, any worms that hatched in allicin treatments exhibited limited signs of motility. Pumpkin seed oil does not appear to possess the same ovicidal potency as allicin, but may still have potential as a larvicidal agent. Based on the current results, allicin is a potential ovicidal agent that may be used independently or incorporated with current treatment methods for H. contortus control.

Culex quinquefasciatus Egg Membrane Alteration and Ovicidal Activity of Cipadessa baccifera (Roth) Plant Extracts Compared to Synthetic Insect Growth Regulators.

BackgroundInsecticide resistance among mosquito vectors for synthetic insecticides still remains a major problem for control efforts. This study assessed the ovicidal potential of crude solvent extracts from the medicinal plant Cipadessa baccifera comparatively to standard registered synthetic insect growth regulators (IGR) on freshly laid eggs of Culex quinquefasciatus.MethodFive plant extracts were prepared using different solvents. The batches of eggs were exposed to different concentrations of each solvent extract comparatively to synthetic IGR. The hatched eggs of Cx. quinquefasciatus were subjected to different concentrations. The first instars that emerged from the eggs were counted daily. The egg hatching inhibition was observed 24, 48 and 72 hrs post treatment. The desiccation median time (DT50 and DT90) was calculated.ResultsThe percent egg hatching inhibition was inversely proportional to the concentration of extracts. The morphological damage to the eggs was observed. Among five solvent extracts, acetone extracts showed the highest ovicidal activity. The changes in eggshell morphology were observed. The maximum ovicidal activity was observed in acetone extracts with DT50 value of 1.70 hrs (0.91–2.22). The methanol plant extract using gas chromatography-mass spectrometry identified 14 compounds.ConclusionThese results suggest that the acetone extracts of C. baccifera have the potential to be used as an ovicidal agent for controlling mosquito populations in aquatic stages. The biodegradability of the extracts has the advantage of being eco-friendly.

Ovicidal lectins from Moringa oleifera and Myracrodruon urundeuva cause alterations in chorionic surface and penetrate the embryos of Aedes aegypti eggs.

Lectins from Moringa oleifera seeds (WSMoL), Myracrodruon urundeuva bark (MuBL), and heartwood (MuHL) are larvicidal agents against Aedes aegypti; in addition, WSMoL is an ovicidal agent against this mosquito. In this work, we evaluated the ovicidal activity of MuBL and MuHL by determining the concentrations that reduce the hatching rates by 50% in 72 h (EC50 ). The effects of WSMoL, MuBL, and MuHL on the ultrastructure of the eggs' surface were assessed by scanning electron microscopy (SEM). In addition, the ability of these lectins to penetrate the eggs was investigated by using conjugates of the lectins with fluorescein isothiocyanate (FITC). MuBL and MuHL were ovicidal agents with EC50 of 0.26 and 0.80 mg/mL (260 and 800 ppm), respectively. SEM images of eggs treated with WSMoL for 24 h revealed discontinuity of the exochorionic network and the absence of the exochorionic cells and their tubercles. After 48 and 72 h of incubation, strong deformation and degeneration of egg surfaces were observed. In MuBL and MuHL-treated eggs, the presence of lumps on the surface of the eggs, disappearance of the exochorionic network and the decrease and deformation of tubercles were observed. Lastly, fluorescence microscopy revealed that the three lectins were able to enter the eggs and reach the digestive tract of the embryos. WSMoL, MuBL, and MuHL are ovicidal agents on A. aegypti that have differing efficiencies in terms of how they cause alterations in the chorionic surface and in terms of their ability to penetrate the eggs. © 2019 Society of Chemical Industry.

Ovicidal effect of essential oils from Zingiberaceae plants and Eucalytus globulus on eggs of head lice, Pediculus humanus capitis De Geer

BackgroundHead lice infestation is an important public health problem worldwide. Chemical pediculicides have lost their efficacy because lice have developed resistance to them. Therefore, alternative pediculicides such as essential oils and herbal products have been proposed for treating head lice infestation. Study designTo determine the efficacy of essential oils from three Zingiberaceae plants (Curcuma xanthorrhiza, Curcuma zedoaria and Zingiber zerumbet) against head lice eggs and to investigate an augmenting substance (Eucalyptus globulus EO) for improving the efficacy of these essential oils in killing head lice eggs, especially on the inhibition of their hatching process. Permethrin pediculicide, soyabean oil, and drinking water were used as positive, negative, and neutral controls, respectively. MethodsAn immersion test was used to evaluate the ovicidal activity of 12 essential oil formulations. Head lice eggs were immersed for 1, 5 and 10 min in the treatments. Mortality rate was observed on day 7 and day 14; mortality was checked under a stereomicroscope. ResultsAll head lice eggs that were immersed in a combination of 10% C. zedoaria EO and 10% E. globulus EO for 5 min did not hatch at all for 7–14 days of incubation. All head lice eggs that were immersed in soyabean oil and drinking water for 1, 5, and 10 min showed 100% hatching rate in 7–14 days of incubation. All head lice eggs that were immersed in permethrin pediculicide for 1, 5 min, showed 100% hatching rate, but when they were immersed for 10 min, permethrin provided 4.0–6.0% inhibition rate with 94.0–96.0% hatching rate for 7–14 days of incubation. All combinations of Zingiberaceae EOs and E. globulus EO at low and high concentrations (5 and 10%) exhibited high ovicidal activities against head lice eggs, and the combinations showed a synergistic effect with an increase in the inhibition rate of more than 50%. ConclusionThese results demonstrated that Zingiberaceae EOs augmented with E. globulus EO are promising ovicidal agents for head lice control.

Chemistry and Biology of Cyperus scariosus: An Overview

In recent times, plant extracted oils have been proved more beneficial in pharmaceutical industries in comparison to the synthetic products as these plants contain biologically active substances which have shown a varied variety of therapeutic effects. The sideeffects of synthetic drugs and their resistance in various pathogens have led to a gradual increase in the use of plants in traditional medicinal methods. All encompassing research has been conducted to explore the medicinal value of the plant extracts. Extracts of Cyperus scariosus have been widely used as anti-hyperglycemic, anti-nociceptive, hepato-protective, anti-fungal, plant growth regulator, insecticidal and ovicidal agent, etc. Its main constituents are terpenoids, steroids, hydrocarbon, flavonoids and saponin which are imperative ingredients of several medicaments used in aboriginal system of medicine. This review article will provide an overview on the compounds isolated from C. scariosus and convincing pharmaceutical properties exhibited by the plant. Keywords: Cyperene, Cyperus scariosus, isopatchoulenone, sesquiterpene.

Bioefficacy of Caesalpinia bonducella extracts against tobacco cutworm, Helicoverpa armigera (Hub.) (Lepidoptera: Noctuidae)

Objective: To evaluate the antifeedant, oviposition deterrent, ovicidal and larvicidal activities of benzene, dichloromethane, diethylether, ethyl acetate and methanol extracts of Indian medicinal plant, Caesalpinia bonducella (C. bonducella) at different concentrations against Lepidopteran agricultural field pest Helicoverpa armigera (Lepidoptera: Noctuidae). Methods: Antifeedant activities of the selected plant extract were studied using leaf disc no- choice method and oviposition deterrent, ovicidal and larvicidal activities were also assessed by adapting the standard protocols. Results: The antifeedant activity of C. bonducella showed significant antifeedant activity in methanol extract. Oviposition deterrency is higher in methanol extract than the other solvent extracts. Similarly, maximum egg mortality was observed in methanol leaf extract of C. bonducella Lethal concentration, LC50 value of benzene, diethylether, dichloromethane, ethyl acetate and methanol extract of C. bonducella were 470.02, 469.00, 465.47, 460.52 and 443.87 mg/L respectively. The Chi-square values are significant at P< 0.05 level. Among five solvent extracts, the methanol extract was responsible for strong lethal activity observed against selected pest species. Conclusions: Results of this study show that the selected Indian medicinal plant C. bonducella could be a potent source of natural antifeedant, oviposition deterrent, ovicidal and larvicidal agent against the field pest Helicoverpa armigera. journal homepage: www.jclmm.com

Ovicidal activity of Ageratum houstonianum Mill. (Asteraceae) leaf extracts against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae)

ObjectiveTo study the ovicidal activity of Ageratum houstonianum (A. houstonianum) leaf extracts against the eggs of vector mosquitoes and to develop additional tools for the control of mosquito-borne diseases. MethodsThe ovicidal activity of crude hexane, ethyl acetate and methanol leaf extracts of A. houstonianum were assayed for their toxicity against the eggs of three important vector mosquitoes, viz., Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus at concentrations of 2.5, 5.0, 10.0 and 20.0 mg/L of the crude extract. ResultsAll extracts showed activity. The minimum concentration at which maximum egg mortality rate of 80% and above obtained was 10.0 mg/L in the case of methanol and ethyl acetate against Anopheles stephensi and Aedes aegypti respectively and 5.0 mg/L in ethyl acetate extract against Culex quinquefasciatus. One hundred per cent egg mortality was obtained only in ethyl acetate extract at 20.0 mg/L against Aedes aegypti. ConclusionsThe crude leaf extracts of A. houstonianum did not exhibit potential ovicidal activity against the vector species studied. Among the crude leaf extracts tested, the activity of ethyl acetate extract was more effective. More research on the screening of phytochemicals as a potential ovicidal agent is warranted to add more tools in the control of mosquitoes.

Oviposition-Stimulant and Ovicidal Activities of Moringa oleifera Lectin on Aedes aegypti

BackgroundNatural insecticides against the vector mosquito Aedes aegypti have been the object of research due to their high level of eco-safety. The water-soluble Moringa oleifera lectin (WSMoL) is a larvicidal agent against A. aegypti. This work reports the effects of WSMoL on oviposition and egg hatching of A. aegypti.Methodology/Principal FindingsWSMoL crude preparations (seed extract and 0–60 protein fraction), at 0.1 mg/mL protein concentration, did not affect oviposition, while A. aegypti gravid females laid their eggs preferentially (73%) in vessels containing isolated WSMoL (0.1 mg/mL), compared with vessels containing only distilled water (control). Volatile compounds were not detected in WSMoL preparation. The hatchability of fresh eggs deposited in the solutions in the oviposition assay was evaluated. The numbers of hatched larvae in seed extract, 0–60 protein fraction and WSMoL were 45±8.7 %, 20±11 % and 55±7.5 %, respectively, significantly (p<0.05) lower than in controls containing only distilled water (75–95%). Embryos were visualized inside fresh control eggs, but not within eggs that were laid and maintained in WSMoL solution. Ovicidal activity was also assessed using stored A. aegypti eggs. The protein concentrations able to reduce the hatching rate by 50% (EC50) were 0.32, 0.16 and 0.1 mg/mL for seed extract, 0–60 protein fraction and WSMoL, respectively. The absence of hatching of stored eggs treated with WSMoL at 0.3 mg/mL (EC99) after transfer to medium without lectin indicates that embryos within the eggs were killed by WSMoL. The reduction in hatching rate of A. aegypti was not linked to decrease in bacteria population.Conclusions/SignificanceWSMoL acted both as a chemical stimulant cue for ovipositing females and ovicidal agent at a given concentration. The oviposition-stimulant and ovicidal activities, combined with the previously reported larvicidal activity, make WSMoL a very interesting candidate in integrated A. aegypti control.

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.

Impact of Parthenium hysterophorus leaf extracts on the fecundity, fertility and behavioural response of Aedes aegypti L.

Different extracts of 1,000 ppm were prepared from the leaves of Parthenium hysterophorus using acetone, benzene, petroleum ether, diethyl ether and hexane as the solvents. The efficacy of each extract was assessed against dengue fever vector, Aedes aegypti by evaluating the variations in fecundity, fertility and behavioural response of the female adults. The leaf extracts could cause 70-100% repellency in the oviposition behaviour of the adults. The diethyl ether extract was found to be the most effective extract resulting in maximum effective repellency (99.7%) leading to the highest levels of reduced fecundity and 100% egg mortality followed by benzene extracts causing 93.8% reduced oviposition and 100% ovicidal effect. Hexane and acetone extracts with the least oviposition deterrence of 70-74% and negligible egg mortality (8-9%) proved to be the least effective extracts. The petroleum ether extract had a moderate impact resulting in 93.2% diminished fecundity and 41% ovicidal effect. The behavioural response of female adults of A. aegypti was evaluated by performing spatial repellency and contact irritancy assays. The most significant spatial repellency behaviour was elicited by acetone extracts leading to escape of 80% mosquitoes. Hexane and diethyl ether extracts could cause moderate response with 50-60% escape, while a slight and no reaction was observed on exposure to petroleum ether and benzene extracts, respectively. An interesting observation was the knocked-down activity caused by the hexane extracts with no recovery even after 24 h. A significant contact irritancy response was noticed in the mosquitoes on exposure to acetone leaf extracts resulting in first flight only after 4 s and a total of 12 flights during exposure. No irritancy behaviour was observed on exposure to diethyl ether and benzene leaf extracts. However, as against controls, a slight irritability response was noticed on exposure to hexane leaf extracts resulting in relative irritability of 1.2. Our results suggest the selective efficiency of Parthenium leaf extracts against A. aegypti, as the most effective oviposition deterrent and ovicidal agent was least effective as irritant extract and vice-versa. Further detailed research is needed to identify the active ingredient in the extracts and implement the effective mosquito management programme.

Larvicidal and ovicidal activity of Cassia fistula Linn. leaf extract against filarial and malarial vector mosquitoes

Methanolic leaf extract of Cassia fistula was tested for larvicidal and ovicidal activity against Culex quinquefasciatus and Anopheles stephensi. The extract was found to be more lethal to the larvae of A. stephensi than C. quinquefasciatus with LC(50) values of 17.97 and 20.57 mg/l, respectively. Mean percent hatchability of the ovicidal activity was observed 120 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. The egg raft of C. quinquefasciatus was found to be more hatchable than A. stephensi. The results show that the leaf extract of C. fistula is promising as a larvicidal and ovicidal agent against C. quinquefasciatus and A. stephensi.