Ovicidal and repellent activities of botanical extracts against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi (Diptera: Culicidae)

Insecticidal bisindole alkaloids from leaves of Tabernaemontana divaricata 'Dwaft'

Six undescribed bisindole alkaloids, namely taberdisines A-F (1-6), were isolated from the leaves of Tabernaemontana divaricata 'Dwaft'. Among them, alkaloids 1 and 2 were the first examples of strychnos-iboga type alkaloid with both C-C linkage patterns. Alkaloid 3, a new type of aspidosperma-iboga with a furan-ring, as well as other three undescribed ones was disclosed. Their structures were elucidated by comprehensive spectroscopic analyses. Alkaloids 1 and 5 showed insecticide activity on Sf9 cell and eggs of Spodoptera frugiperda in vivo, which might explain the potential of the plants for insect resistance.

Methanolic Extracts of Chiococca alba in Aedes aegypti Biorational Management: Larvicidal and Repellent Potential, and Selectivity against Non-Target Organisms

The use of formulations containing botanical products for controlling insects that vector human and animal diseases has increased in recent years. Plant extracts seem to offer fewer risks to the environment and to human health without reducing the application strategy's efficacy when compared to synthetic and conventional insecticides and repellents. Here, we evaluated the potential of extracts obtained from caninana, Chiococca alba (L.) Hitchc. (Rubiaceae), plants as a tool to be integrated into the management of Aedes aegypti, one of the principal vectors for the transmission of arborviruses in humans. We assessed the larvicidal and repellence performance against adult mosquitoes and evaluated the potential undesired effects of the extracts on non-target organisms. We assessed the susceptibility and predatory abilities of the nymphs of Belostoma anurum, a naturally occurring mosquito larva predator, and evaluated the C. alba extract's cytotoxic effects in mammalian cell lines. Our chromatographic analysis revealed 18 compounds, including rutin, naringin, myricetin, morin, and quercetin. The methanolic extracts of C. alba showed larvicidal (LC₅₀ = 82 (72-94) mg/mL) activity without killing or affecting the abilities of B. anurum to prey upon mosquito larvae. Our in silico predictions revealed the molecular interactions between rutin and the AeagOBP1 receptor to be one possible mechanism for the repellent potential recorded for formulations containing C. alba extracts. Low cytotoxicity against mammalian cell lines reinforces the selectivity of C. alba extracts. Collectively, our findings highlight the potential of C. alba and one of its constituents (rutin) as alternative tools to be integrated into the management of A. aegypti mosquitoes.

Essential oil of Piper purusanum C.DC (Piperaceae) and its main sesquiterpenes: biodefensives against malaria and dengue vectors, without lethal effect on non-target aquatic fauna

The mosquito vectors of the genera Aedes and Anopheles present resistance to several commercial insecticides, which are also toxic to non-predator targets. On the other hand, essential oils are a promising source of insecticides. Thus, in this work, the essential oil from the leaves of Piper purusanum was characterized by gas chromatography-based approaches and evaluated as biodefensive against malaria and dengue vectors. The main compounds of P. purusanum essential oil were β-caryophyllene (57.05%), α-humulene (14.50%), and germacrene D (8.20%). The essential oil inhibited egg hatching (7.6 ± 1.5 to 95.6 ± 4.5%), caused larval death (LC₅₀ from 49.84 to 51.60 ppm), and inhibited the action of acetylcholinesterase (IC₅₀ of 2.29 µg/mL), which can be related to the mechanisms of action. On the other hand, the biological activities of β-caryophyllene, α-humulene, and germacrene D were higher than that of essential oil. In addition, these sesquiterpenes and essential oil did not show a lethal effect on Toxorhynchites splendens, Anisops bouvieri, Gambusia affinis, and Diplonychus indicus (LC₅₀ from 2098.80 to 7707.13 ppm), although D. indicus is more sensitive (SI/PSF from 48.56 to 252.02 ppm) to essential oil, representing a natural alternative against these relevant vectors.

Contribution of Meliaceous plants in furnishing lead compounds for antiplasmodial and insecticidal drug development

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria remains one of the greatest threats to human life especially in the tropical and sub-tropical regions where it claims hundreds of thousands of lives of young children every year. Meliaceae represent a large family of trees and shrubs, which are widely used in African traditional medicine for the treatment of several ailments including fever due to malaria. The in vitro and in vivo antiplasmodial as well as insecticidal investigations of their extracts or isolated compounds have led to promising results but to the best of our knowledge, no specific review on the traditional uses, phytochemistry of the antiplasmodial, insecticidal and cytotoxic lead compounds and extracts of Meliaceae plants has been compiled.

AIMS

To review the literature up to 2021 on the Meliaceae family with antiplasmodial, insecticidal and cytotoxic activity.

MATERIALS AND METHODS

A number of online libraries including PubMed, Scifinder, Google Scholar and Web of Science were used in searching for information on antiplasmodial metabolites from Meliaceous plants. The keywords Meliaceae, malaria, Plasmodium, Anopheles and antiplasmodial were used to monitor and refine our search without language restriction.

RESULTS

The phytochemical investigations of genera of the family Meliaceae led to the isolation and characterization of a wide range of structural diversity of compounds, 124 of which have been evaluated for their antiplasmodial potency against 11 chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum strains. A total of 45 compounds were reported with promising insecticidal potentials against two efficient vector species, Anopheles stephensi Liston and A. gambiae Giles. Limonoids were the most abundant (51.6%) reported compounds and they exhibited the most promising antiplasmodial activity such as gedunin (3) which demonstrated an activity equal to quinine or azadirachtin (1) displaying promising larvicidal, pupicidal and adulticidal effects on different larval instars of A. stephensi with almost 100% larval mortality at 1 ppm concentration.

CONCLUSION

Studies performed so far on Meliaceae plants have reported compounds with significant antiplasmodial and insecticidal activity, lending support to the use of species of this family in folk medicine, for the treatment of malaria. Moreover, results qualified several of these species as important sources of compounds for the development of eco-friendly pesticides to control mosquito vectors. However, more in vitro, in vivo and full ADMET studies are still required to provide additional data that could guide in developing novel drugs and insecticides.

Impact of Cymbopogon flexuosus (Poaceae) essential oil and primary components on the eclosion and larval development of Aedes aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L^-1 and larvae with 3 or 6 mg L^-1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L^-1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L^-1: 6 ± 0.0 mm; 6 mg L^-1: 6 ± 0.7 mm) and head width (3 mg L^-1: 0.8 ± 0 mm; 6 mg L^-1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

A review on the efficacy of Ocimum gratissimum, Mentha spicata, and Moringa oleifera leaf extracts in repelling mosquito

Abstract

@@@In recent times, repellents and synthetic drugs have been identified as having negative toxicity effects on humans and the environment. Apart from the unfavourable effects on man and livestock caused by these chemicals-based (synthetic) repellents, they are also expensive, non-biodegradable, and no more effective because mosquitoes are getting adapted. With these drawbacks, an eco-friendly plant-based insecticide as a substitute is needed urgently. This paper reviews the extraction and use of essential oil from the leaves of Mentha spicata, Ocimum gratissimum, and Moringa oleifera as mosquito repellent. Carvone, Eugenol, and 9-Octadecenoic acid were discovered to be the most active components in the M. spicata, O. gratissimum, and M. oleifera extracts, respectively, using gas chromatography-mass spectrometry (GC-MS).

Highlights

Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.

Toxicity of Essential Oils Nanoemulsion Against Aphis Craccivora and Their Inhibitory Activity on Insect Enzymes

Essential oils are widely used as botanical insecticides rather than chemically synthesized pesticides which led to catastrophic effects on humans, the environment, and eutrophication. Here, encapsulation of four essential oils Basilicum ocimum, Cuminum cyminum, Origanum marjorana, and Matricaria chamomilla were utilized in the presence of 3% v/v ethanol, as anti-insect against Aphis craccivora and compared to traditional insecticides dinotefuran and pymetrozine. Different tools were used to characterize the prepared nanoemulsion such as TEM, SEM, and Zeta potential analyzer. Besides, selected B. ocimum and C. cyminum were analyzed by gas chromatography-mass GC/mass spectrometry. The results reveal that nanoemulsion exhibited considerable toxic activities against laboratory and field strains of cowpea aphid. In the toxicity bioassay test of essential oils, moderate mortality was observed at 10,000 mg/L against aphid with lethal concentration that kills 50% of insects (LC50) values of basil 992 mg/L and marjoram 3162 mg/L. Else, nanoemulsion provided the highest mortality rate at 625 mg/L and the LC50 values of basil nanoemulsion (NE) 45 mg/L, and marjoram NE 188 mg/L in laboratory strains. The systemic effects of the tested substances acetylcholine esterase, alkaline phosphatase, β-esterases, glutathione S-transferase (GST), and mixed-function oxidase (MFO) enzymes on insects were found to be significantly decreased and increased when compared with control groups. Overall, these results highlight that the nanoemulsion is potential tools to control cowpea aphid and could be useful in developing integrated insect management in faba bean fields.

Plant Natural Products for the Control of Aedes aegypti: The Main Vector of Important Arboviruses

The mosquito species Aedes aegypti is one of the main vectors of arboviruses, including dengue, Zika and chikungunya. Considering the deficiency or absence of vaccines to prevent these diseases, vector control remains an important strategy. The use of plant natural product-based insecticides constitutes an alternative to chemical insecticides as they are degraded more easily and are less harmful to the environment, not to mention their lower toxicity to non-target insects. This review details plant species and their secondary metabolites that have demonstrated insecticidal properties (ovicidal, larvicidal, pupicidal, adulticidal, repellent and ovipositional effects) against the mosquito, together with their mechanisms of action. In particular, essential oils and some of their chemical constituents such as terpenoids and phenylpropanoids offer distinct advantages. Thiophenes, amides and alkaloids also possess high larvicidal and adulticidal activities, adding to the wealth of plant natural products with potential in vector control applications.

Historical Perspective and Biotechnological Trends to Block Arboviruses Transmission by Controlling Aedes aegypti Mosquitos Using Different Approaches

Continuous climate changes associated with the disorderly occupation of urban areas have exposed Latin American populations to the emergence and reemergence of arboviruses transmitted by Aedes aegypti. The magnitude of the financial and political problems these epidemics may bring to the future of developing countries is still ignored. Due to the lack of effective antiviral drugs and vaccines against arboviruses, the primary measure for preventing or reducing the transmission of diseases depends entirely on the control of vectors or the interruption of human-vector contact. In Brazil the first attempt to control A. aegypti took place in 1902 by eliminating artificial sites of eproduction. Other strategies, such as the use of oviposition traps and chemical control with dichlorodiphenyltrichlorethane and pyrethroids, were successful, but only for a limited time. More recently, biotechnical approaches, such as the release of transgenics or sterile mosquitoes and the, development of transmission blocking vaccines, are being applied to try to control the A. aegypti population and/or arbovirus transmission. Endemic countries spend about twice as much to treat patients as they do on the prevention of mosquito-transmitted diseases. The result of this strategy is an explosive outbreak of arboviruses cases. This review summarizes the social impacts caused by A. aegypti-transmitted diseases, mainly from a biotechnological perspective in vector control aimed at protecting Latin American populations against arboviruses.

Efficacy of essential oil from Clausena anisata and its impact on biochemical changes of Sitophilus oryzae

Essential oil (EO), from Clausena anisata, was evaluated for their efficacy (fumigant and repellent activities) against Sitophilus oryzae. Result revealed that C. anisata showed 82% fumigant toxicity (insect mortality) at 160 μL/L concentration after 24h observation period. C. anisata exhibited LC₅₀ value of 17.84 μL/L concentration for fumigant toxicity. The insect movement behaviour (repellent) was observed in two different concentrations of 10 and 50 μL for a period of 3 h. Maximum repellent activity (- 0.25) was observed at 50 μL/L concentration against S. oryzae after 3-h observation. At 3, 6 and 12 μL/L concentrations of C. anisata oil significantly reduced the protein content and total esterase activity of S. oryzae.

Repellency and larvicidal activities of Azadirachta indica seed oil on Anopheles gambiae in Nigeria

Despite the recent decline in the global prevalence of malaria, the disease continues to be one of the major causes of morbidity and mortality among pregnant women and under-five children in Nigeria. The adoption of an integrated approach to malaria control including the use of bio-insecticide will further reduce the burden of malaria. This study determined the repellency and bio-insecticidal effects of Azadirachta indica oil on Anopheles gambiae in Ibadan, Nigeria. The study was experimental in design. Oil was extracted from the ground seed kernel of Azadirachta indica plants using N-hexane as a solvent. Larvicidal tests were carried out on 600 third and fourth instar stages of Anopheles gambiae using an aliquot of extracted oil emulsified with a surfactant (Tween 80) at concentrations ranging from 100 to 500 ppm. Mortality was recorded every 24 h for five days. Repellency tests were carried out by exposing Guinea pigs that were previously treated with the oil mixed with paraffin at 10–40%v/v concentrations, to 70 adult female Anopheles gambiae in netted cages. Data were analysed using descriptive statistics and ANOVA. The oil yield accounted for 40.0% weight of the ground seed kernel. The larvicidal effect was significant across the concentration of the emulsified Azadirachta oil ranging from 91.6-100.0%, compared to the control experiment ranging from 5-15% (LC50 and LC90: -1666.86 ppm and -2880.94 ppm respectively). A 100.0% larval mortality of Anopheles gambiae was recorded within three days at 500 ppm. All the concentrations of the oil solution also caused 100% inhibition of pupae formation. The repellent effect of adult Anopheles was significant (p < 0.05) across the concentrations but with varying degrees of protection. The highest repellent effect was observed at 40.0% (v/v). The possibility of using Azadirachta indica as bio-insecticide against Anopheles gambiae was established in this study.

Effectiveness of plant-based repellents against different Anopheles species: a systematic review

Plant-based repellents have been applied for generations in traditional practice as a personal protection approach against different species of Anopheles. Knowledge of traditional repellent plants is a significant resource for the development of new natural products as an alternative to chemical repellents. Many studies have reported evidence of repellant activities of plant extracts or essential oils against malaria vectors worldwide. This systematic review aimed to assess the effectiveness of plant-based repellents against Anopheles mosquitoes. All eligible studies on the repellency effects of plants against Anopheles mosquitoes published up to July 2018 were systematically searched through PubMed/Medline, Scopus and Google scholar databases. Outcomes measures were percentage repellency and protection time. A total of 62 trials met the inclusion criteria. The highest repellency effect was identified from Ligusticum sinense extract, followed by citronella, pine, Dalbergia sissoo, peppermint and Rhizophora mucronata oils with complete protection time ranging from 9.1 to 11.5 h. Furthermore, essential oils from plants such as lavender, camphor, catnip, geranium, jasmine, broad-leaved eucalyptus, lemongrass, lemon-scented eucalyptus, amyris, narrow-leaved eucalyptus, carotin, cedarwood, chamomile, cinnamon oil, juniper, cajeput, soya bean, rosemary, niaouli, olive, tagetes, violet, sandalwood, litsea, galbanum, and Curcuma longa also showed good repellency with 8 h complete repellency against different species of Anopheles. Essential oils and extracts of some plants could be formulated for the development of eco-friendly repellents against Anopheles species. Plant oils may serve as suitable alternatives to synthetic repellents in the future as they are relatively safe, inexpensive, and are readily available in many parts of the world.

Insecticidal Activity of Compounds of Plant Origin on Mahanarva spectabilis (Hemiptera: Cercopidae)

The damage caused by spittlebugs varies according to the species of grass, and the losses can reach alarming levels. Measures for population control are currently restricted to the use of resistant grasses and the diversification of pastures. Therefore, alternative control measures are necessary, such as the use of botanical insecticides. The aim of this study was to evaluate the insecticidal activities of thymol, carvacrol, eugenol, cinnamaldehyde, and trans-anethole on Mahanarva spectabilis eggs, nymphs, and adults under laboratory conditions. In the egg tests, treatments with eugenol, carvacrol, and thymol showed the highest mortalities, presenting efficiencies higher than 85% after 48 h of application. In the nymph tests, the treatments with thymol and carvacrol at 2.5% and eugenol at 2.0% and 2.5% showed intermediate efficiencies, with values above 61%. The highest mortality was observed in the treatment with trans-anethole at 2.5%, with an efficiency of 95%. In the tests with adults, only treatment with trans-anethole at 2.5% obtained an efficiency reaching 90%; in the other treatments, the efficiency did not exceed 51%. These results showed that, at these concentrations, trans-anethole presents a high rate of insecticidal activity on M. spectabilis nymphs and adults and, therefore, is recommended as a potential natural insecticide for the control of this pest.

Target and non-target botanical pesticides effect of Trichodesma indicum (Linn) R. Br. and their chemical derivatives against the dengue vector, Aedes aegypti L

The effects of crude ethanol derived leaf extract Trichodesma indicum (Linn) (Ex-Ti) and their chief derivatives were accessed on the survival and development of the dengue mosquito Ae. aegypti also their non-toxic activity against mosquito predator. T. indicum is recognized to be the vital weed plant and a promising herb in the traditional ayurvedic medicine. In this study, the GC-MS chromatogram of Ex-Ti showed higher peak area percentage for cis-10-Heptadecenoic acid (21.83%) followed by cycloheptadecanone (14.32%). The Ex-Ti displayed predominant mortality in larvae with 96.45 and 93.31% at the prominent dosage (200 ppm) against III and IV instar. Correspondingly, sub-lethal dosage against the enzymatic profile of III and IV instar showed downregulation of α,β-carboxylesterase and SOD protein profiles at the maximum concentration of 100 ppm. However, enzyme level of GST as well as CYP450 increased significantly dependent on sub-lethal concentration. Likewise, fecundity and hatchability of egg rate of dengue mosquito decreased to the sub-lethal concentration of Ex-Ti. Repellent assay illustrates that Ex-Ti concentration had greater protection time up to 210 min at 100 ppm. Also, activity of Ex-Ti on adult mosquito displayed 100% mortality at the maximum dosage of 600, 500 and 400 ppm within the period of 50, 60 and 70 min, respectively. Photomicrography screening showed that lethal dosage of Ex-Ti (100 ppm) produced severe morphological changes with dysregulation in their body parts as matched to the control. Effects of Ex-Ti on the Toxorhynchites splendens IV instar larvae showed less mortality (43.47%) even at the maximum dosage of 1500 ppm as matched to the chemical pesticide Temephos. Overall, the present research adds a toxicological valuation on the Ex-Ti and their active constituents as a larvicidal, repellent and adulticidal agents against the global burdening dengue mosquito.

Efficiency of Tinospora crispa against Culex quinquefasciatus larva

Tinospora crispa stem aqueous extractions for various time durations were determined regarding their total phenolic content and their larvicidal abilities. The results revealed that the total phenolic content in 1-, 3-, 5-, 10-, and 24-h extracts were 8.26, 8.43, 13.57, 12.52, and 12.43 mg/g gallic acid equivalent, respectively. The 5-h extract of T. crispa was evaluated against Culex quinquefasciatus mosquito larva in concentrations 3.125, 6.25, 12.5, and 25 mg/l, by determining the lethal concentration (LC) within 24 h and by histopathological analysis. The 24-h LC₅₀ and LC₉₀ values were 16.95 and 30.12 mg/l, respectively. The histopathological lesions after exposure to 50% of the 24-h LC₅₀ were observed primarily in the midgut of the larva. The lesions observed were for the example epithelial cells lifting from the basement membrane, cell elongation protruding into the lumen, brush border disrupting with absent microvilli, and vesicle appearance. The present study indicated that the aqueous extract of this herb may have a suitable property for a larvicidal natural product and may replace harmful chemical pesticides.

Evaluation of larvicidal, adulticidal, and anticholinesterase activities of essential oils of Illicium verum Hook. f., Pimenta dioica (L.) Merr., and Myristica fragrans Houtt. against Zika virus vectors

Aedes aegypti is the vector responsible for transmitting pathogens that cause various infectious diseases, such as dengue, Zika, yellow fever, and chikungunya, worrying health authorities in the tropics. Due to resistance of mosquitoes to synthetic insecticides, the search for more effective insecticidal agents becomes crucial. The aim of this study was to verify the larvicidal, adulticidal, and anticholinesterase activities of the essential oils of the Illicium verum (EOIV), Pimenta dioica (EOPD), and Myristica fragrans (EOMF) against Ae. aegypti. The essential oils (EOs) were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The larvicidal and adulticidal activities of EOs were evaluated against third instar larvae and Ae. aegypti adult females, respectively, using the procedures of the World Health Organization (WHO) and the anticholinesterase activity of the EOs by the modified Ellman method. The following major components were identified: (E)-anethole (90.1%) for EOIV, methyl eugenol (55.0%) for EOPD, and sabinene (52.1%) for EOMF. All EOs exhibited larvicidal and adulticidal activity against Ae. aegypti. The highest larval mortality was observed in EOMF with LC₅₀ = 28.2 μg mL^-1. Adult mortality was observed after 1 (knockdown) and 24 h exposure, with the highest potential established by the EOIV, KC₅₀ = 7.3 μg mg female^-1 and LC₅₀ = 10.3 μg mg female^-1. EOIV (IC₅₀ = 4800 μg mL^-1), EOMF (IC₅₀ = 4510 μg mL^-1), and EOPD (IC₅₀ = 1320 μg mL^-1) inhibited AChE. EOMF (4130 μg mL^-1) and EOPD (IC₅₀ = 3340 μg mL^-1) inhibited BChE whereas EOIV showed no inhibition. The EOs were toxic to larvae and adults of Ae. aegypti, as well as being less toxic to humans than the currently used insecticides, opening the possibility of elaboration of a natural, safe, and ecological bioinsecticide for vector control.

Biosurfactants produced by Bacillus subtilis A1 and Pseudomonas stutzeri NA3 reduce longevity and fecundity of Anopheles stephensi and show high toxicity against young instars

Anopheles stephensi acts as vector of Plasmodium parasites, which are responsible for malaria in tropical and subtropical areas worldwide. Currently, malaria management is a big challenge due to the presence of insecticide-resistant strains as well as to the development of Plasmodium species highly resistant to major antimalarial drugs. Therefore, the present study focused on biosurfactant produced by two bacteria Bacillus subtilis A1 and Pseudomonas stutzeri NA3, evaluating them for insecticidal applications against malaria mosquitoes. The produced biosurfactants were characterized using FT-IR spectroscopy and gas chromatography-mass spectrometry (GC-MS), which confirmed that biosurfactants had a lipopeptidic nature. Both biosurfactants were tested against larvae and pupae of A. stephensi. LC₅₀ values were 3.58 (larva I), 4.92 (II), 5.73 (III), 7.10 (IV), and 7.99 (pupae) and 2.61 (I), 3.68 (II), 4.48 (III), 5.55 (IV), and 6.99 (pupa) for biosurfactants produced by B. subtilis A1 and P. stutzeri NA3, respectively. Treatments with bacterial surfactants led to various physiological changes including longer pupal duration, shorter adult oviposition period, and reduced longevity and fecundity. To the best of our knowledge, there are really limited reports on the mosquitocidal and physiological effects due to biosurfactant produced by bacterial strains. Overall, the toxic activity of these biosurfactant on all young instars of A. stephensi, as well as their major impact on adult longevity and fecundity, allows their further consideration for the development of insecticides in the fight against malaria mosquitoes.

Beauveria bassiana (Clavicipitaceae): a potent fungal agent for controlling mosquito vectors of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti (Diptera: Culicidae)

The efficacy of bioactive compounds identified from Beauveria bassiana extracts as effective larvicidal and pupicidal agents against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti mosquito vectors under laboratory conditions are studied.

Acute toxicity and repellent activity of the Origanum scabrum Boiss. & Heldr. (Lamiaceae) essential oil against four mosquito vectors of public health importance and its biosafety on non-target aquatic organisms

The recent outbreaks of dengue, chikungunya, and Zika virus highlighted the pivotal importance of mosquito vector control in tropical and subtropical areas worldwide. However, mosquito control is facing hot challenges, mainly due to the rapid development of pesticide resistance in Culicidae and the limited success of biocontrol programs on Aedes mosquitoes. In this framework, screening botanicals for their mosquitocidal potential may offer effective and eco-friendly tools in the fight against mosquitoes. In the present study, the essential oil (EO) obtained from the medicinal plant Origanum scabrum was analyzed by GC-MS and evaluated for its mosquitocidal and repellent activities towards Anopheles stephensi, Aedes aegypti, Culex quinquefasciatus, and Culex tritaeniorhynchus. GC-MS analysis showed a total of 28 compounds, representing 97.1 % of the EO. The major constituents were carvacrol (48.2 %) and thymol (16.6 %). The EO was toxic effect to the A. stephensi, A. aegypti, C. quinquefasciatus, and C. tritaeniorhynchus larvae, with LC₅₀ of 61.65, 67.13, 72.45, and 78.87 μg/ml, respectively. Complete ovicidal activity was observed at 160, 200, 240, and 280 μg/ml, respectively. Against adult mosquitoes, LD₅₀ were 122.38, 134.39, 144.53, and 158.87 μg/ml, respectively. In repellency assays, the EOs tested at 1.0, 2.5, and 5.0 mg/cm² concentration of O. scabrum gave 100 % protection from mosquito bites up to 210, 180, 150, and 120 min, respectively. From an eco-toxicological point of view, the EO was tested on three non-target mosquito predators, Gambusia affinis, Diplonychus indicus, and Anisops bouvieri, with LC₅₀ ranging from 4162 to 12,425 μg/ml. Overall, the EO from O. scabrum may be considered as a low-cost and eco-friendly source of phytochemicals to develop novel repellents against Culicidae.

Larvicidal and repellent potential of Zingiber nimmonii (J. Graham) Dalzell (Zingiberaceae) essential oil: an eco-friendly tool against malaria, dengue, and lymphatic filariasis mosquito vectors?

Mosquitoes (Diptera: Culicidae) are important vectors of terms of public health relevance, especially in tropical and sub-tropical regions. The continuous and indiscriminate use of conventional pesticides for the control of mosquito vectors has resulted in the development of resistance and negative impacts on non-target organisms and the environment. Therefore, there is a need for development of effective mosquito control tools. In this study, the larvicidal and repellent activity of Zingiber nimmonii rhizome essential oil (EO) was evaluated against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti, and the lymphatic filariasis vector Culex quinquefasciatus. The chemical composition of the EO was analyzed by gas chromatography-mass spectroscopy (GC-MS). GC-MS revealed that the Z. nimmonii EO contained at least 33 compounds. Major constituents were myrcene, β-caryophyllene, α-humulene, and α-cadinol. In acute toxicity assays, the EO showed significant toxicity against early third-stage larvae of An. stephensi, Ae. aegypti, and Cx. quinquefasciatus, with LC50 values of 41.19, 44.46, and 48.26 μg/ml, respectively. Repellency bioassays at 1.0, 2.0, and 5.0 mg/cm(2) of Z. nimmonii EO gave 100 % protection up to 120, 150, and 180 min. against An. stephensi, followed by Ae. aegypti (90, 120, and 150 min) and Cx. quinquefasciatus (60, 90, and 120 min). Furthermore, the EO was safer towards two non-target aquatic organisms, Diplonychus indicus and Gambusia affinis, with LC50 values of 3241.53 and 9250.12 μg/ml, respectively. Overall, this research adds basic knowledge to develop newer and safer natural larvicides and repellent from Zingiberaceae plants against malaria, dengue, and filariasis mosquito vectors.

Repellent properties of Cardiospermum halicacabum Linn. (Family: Sapindaceae) plant leaf extracts against three important vector mosquitoes

OBJECTIVE

To determine repellent activity of hexane, ethyl acetate, benzene, chloroform and methanol extract of Cardiospermum halicacabum (C. halicacabum) against Culex quinquefasciatus (Cx. quinquefasciatus), Aedes aegypti (Ae. aegypti) and Anopheles stephensi (An. stephensi).

METHODS

Evaluation was carried out in a net cage (45 cm×30 cm×25 cm) containing 100 blood starved female mosquitoes of three mosquito species and were assayed in the laboratory condition by using the protocol of WHO 2005; The plant leaf crude extracts of C. halicacabum was applied at 1.0, 2.5, and 5.0 mg/cm(2) separately in the exposed area of the fore arm. Only ethanol served as control.

RESULTS

In this observation, the plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity was dependent on the strength of the plant extracts. The tested plant crude extracts had exerted promising repellent against all the three mosquitoes.

CONCLUSIONS

From the results it can be concluded the crude extract of C. halicacabum was potential for controlling Cx. quinquefasciatus, Ae. aegypti and An. stephensi mosquitoes.

Synthesis and characterization of silver nanoparticles using Gmelina asiatica leaf extract against filariasis, dengue, and malaria vector mosquitoes

Mosquitoes are blood-feeding insects and serve as the most important vectors for spreading human diseases such as malaria, yellow fever, dengue fever, and filariasis. The continued use of synthetic insecticides has resulted in resistance in mosquitoes. Synthetic insecticides are toxic and affect the environment by contaminating soil, water, and air, and then natural products may be an alternative to synthetic insecticides because they are effective, biodegradable, eco-friendly, and safe to environment. Botanical origin may serve as suitable alternative biocontrol techniques in the future. The present study was carried out to establish the larvicidal potential of leaf extracts of Gmelina asiatica and synthesized silver nanoparticles using aqueous leaf extract against late third instar larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. Larvae were exposed to varying concentrations of plant extracts and synthesized AgNPs for 24 h. The results were recorded from UV-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy analysis support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the larvae of An. stephensi (lethal dose (LC₅₀) = 22.44 μg/mL; LC₉₀ 40.65 μg/mL), Ae. aegypti (LC₅₀ = 25.77 μg/mL; LC₉₀ 45.98 μg/mL), and C. quinquefasciatus (LC₅₀ = 27.83 μg/mL; LC₉₀ 48.92 μg/mL), respectively. No mortality was observed in the control. This is the first report on mosquito larvicidal activity of plant-synthesized nanoparticles. Thus, the use of G. asiatica to synthesize silver nanoparticles is a rapid, eco-friendly, and a single-step approach and the AgNps formed can be potential mosquito larvicidal agents.

Laboratory evaluation of Indian medicinal plants as repellents against malaria, dengue, and filariasis vector mosquitoes

Mosquito-borne diseases have an economic impact, including loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates; however, no part of the world is free from vector-borne diseases. Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikungunya fever, West Nile virus, and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticides, in the present study, the repellent activity of crude hexane, ethyl acetate, benzene, chloroform, and methanol extracts of leaf of Erythrina indica and root of Asparagus racemosus were assayed for their repellency against three important vector mosquitoes, viz., Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The crude extract was applied on a membrane used for membrane feeding of unfed mosquitoes in a 1-ft cage. About 50 unfed 3-4-day-old laboratory-reared pathogen-free strains of A. stephensi, A. aegypti, and C. quinquefasciatus were introduced in a 1-ft cage fitted with a membrane with blood for feeding with temperature maintained at 37 °C through circulating water bath maintained at 40-45 °C. Three concentrations (1.0, 2.0, and 5.0 mg/cm(2)) of the crude extracts were evaluated. Repellents in E. indica afforded longer protection time against A. stephensi, A. aegypti, and C. quinquefasciatus than those in A. racemosus at 5.0 mg/cm(2) concentration, and the mean complete protection time ranged from 120 to 210 min with the different extracts tested. In this observation, these two plant crude extracts gave protection against mosquito bites; also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf extract of E. indica and root extract of A. racemosus have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This is the first report on the mosquito repellent activity of the reported A. racemosus and E. indica plants.

Evaluation of plant-mediated synthesized silver nanoparticles against vector mosquitoes

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Heliotropium indicum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. Adult mosquitoes were exposed to varying concentrations of aqueous extract of H. indicum and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of H. indicum, and the formation of nanoparticles was observed within 6 h. The results recorded from UV-vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the adult of A. stephensi (lethal dose (LD)₅₀ = 26.712 μg/mL; LD₉₀ = 49.061 μg/mL), A. aegypti (LD₅₀ = 29.626 μg/mL; LD₉₀ = 54.269 μg/mL), and C. quinquefasciatus (LD₅₀ = 32.077 μg/mL; LD₉₀ = 58.426 μg/mL), respectively. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H.indicum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.

Larvicidal, ovicidal, and oviposition-deterrent activities of four plant extracts against three mosquito species

In mosquito control programs, insecticides of botanical origin have the potential to eliminate eggs, larvae, and adults. So, the larvicidal, ovicidal, and oviposition-deterrent activities of petroleum ether and ethyl acetate extracts of the leaves of Eugenia jambolana, Solidago canadensis, Euodia ridleyi, and Spilanthes mauritiana were assayed against the three vector mosquito species, namely Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The larval bioassay was conducted following the World Health Organization method. The maximum larval mortality was found with ethyl acetate extract of S. mauritiana against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus with LC50 values of 11.51, 28.1, 14.10 ppm, respectively. The mean percent hatchability of the ovicidal activity was observed at 48-h post-treatment. The percent hatchability was found to be inversely proportional to the concentration of the extract and directly proportional to the number of eggs. The flower head extract of S. mauritiana gave 100% mortality followed by E. ridleyi, S. canadensis, and E. jambolana against the eggs of the three mosquito vectors. For oviposition-deterrent effect, out of the five concentrations tested (20, 40, 60, 80, and 100 ppm), the concentration of 100 ppm showed a significant egg laying-deterrent capacity. The oviposition activity index value of E. jambolana, E. ridleyi, S. canadensis, and S. mauritiana against A. aegypti, A. stephensi, C. quinquefasciatus at 100 ppm were -0.71, -0.71, -0.90, -0.93, -0.85, -0.91, -1, -1, -0.71, -0.85, -1, and -1, respectively. These results suggest that the leaf/flower extracts of certain local plants have the potential to be developed as possible eco-friendly means for the control of mosquitoes.

Chemical Composition, Larvicidal and Repellency Properties of Cionura erecta (L.) Griseb. Against Malaria Vector, Anopheles stephensi Liston (Diptera: Culicidae)

BACKGROUND

Application of plant derivatives have been suggested as alternative sources for mosquito control.

METHODS

The root essential oil and methanol extract of Cionura erecta (L.) Griseb was tested under laboratory conditions for larvicidal and skin repelleny activities against Anopheles stephensi. The chemical compositions of essential oils were analyzed using gas chromatography- mass spectrometry.

RESULTS

Among the five concentrations tested, the 320 ppm of essential oil and 1280 ppm of methanolic extract had the most toxic effects yielding 100% mortality. The LC50 values of C. erecta for both essential oil and methanolic extract were 77.30 and 250.38 ppm, respectively. A total of 19 compounds were identified in essential oil of root. The major components were detected in root essential oil including Cedren-9-one (7.89%), alpha cadinol (5.67%), eugenol (4.02%) and alpha muurolene (3.58%). The protection time of 50% solution of essential oil against bites of An. stephensi was 2.28 hour on white rabbit and the ED50 and ED90 values of the essential oil were 10.12 and 23.01 ppm respectively.

CONCLUSION

The findings suggest that C. erecta oil has a potential source as larvicidal and repellency properties against An.stephensi.

Bioefficacy of crude extract of Cyperus aromaticus (Family: Cyperaceae) cultured cells, against Aedes aegypti and Aedes albopictus mosquitoes

OBJECTIVE

To evaluate the growth inhibition activity of the crude extract of Cyperus aromaticus (C. aromaticus) cultured cells against the 3rd instar larvae of Aedes aegypti (Linn.) and Aedes albopictus Skuse (Ae. albopictus) under laboratory conditions, and determine the sublethal effects (EI50) of the crude extract of C. aromaticus cultured cells on some biological and morphological parameters of both Aedes mosquito species during two generations as well.

METHODS

The cell suspension cultures of C. aromaticus were activated from five callus lines (P4, Pa, Z1, Z6 and Ml) derived from the root explants of in vitro plantlets. The cultured cells were extracted in chloroform and used as plant material for the present study. For detection of juvenile hormone III, the crude extracts were analyzed by HPLC. Then the crude extracts of the three C. aromaticus cultured cell lines which contained varied amounts of juvenile hormone III [high level (P4 cell line), medium level (Z1 cell line) and low level (Ml cell line)] were tested against Aedes mosquito species. Laboratory evaluation was performed against late third instar larvae of the Vector Control Research Unit strains of Ae. aegypti and Ae. albopictus using the standard WHO method. The effects of EI50 of the C. aromaticus cultured P4 cells on fecundity, fertility, growth period, sex ratio, adult size and longevity of Aedes mosquitoes were assessed.

RESULTS

Bioassay tests presented the remarkable growth inhibition activity of the crude extracts of C. aromaticus cultured cells against the two Aedes mosquitoes. Between the two mosquito species, Ae. albopictus was more susceptible to the crude extracts with lower EI50 values. EI50 of the crude extract of C. aromaticus cultured cells (P4) increased the sterility indices in the parental generation females in both Aedes mosquito species. A significant delay in the pupal formation and adult emergence were observed in the parental generation of the both mosquito species. The sex ratio of the adult population either parental or F1 generation of the Aedes mosquito species was not significantly affected by the EI50 dosage of the crude extract of C. aromaticus cultured P4 cells. A significant decrease in the wing length of the treated adult (female and male) of Aedes aegypti as well as the treated female of Ae. albopictus were observed. Longevity of the adult female of the parental generation of both Aedes mosquitoes as well as females of F1 generation of Ae. albopictus were significantly decreased.

CONCLUSIONS

The present study revealed the potential of the crude extract of C. aromaticus cultured cells in controlling vector mosquito populations in the effort to reduce the transmission of vector borne diseases.

Mosquito larvicidal activity of thymol from essential oil of Coleus aromaticus Benth. against Culex tritaeniorhynchus, Aedes albopictus, and Anopheles subpictus (Diptera: Culicidae)

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have a worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. However, the indiscriminate use of conventional insecticides is fostering multifarious problems like widespread development of insecticide resistance, toxic hazards to mammals, undesirable effects on nontarget organisms, and environmental pollution. The aim of this research was to evaluate the toxicity of mosquito larvicidal activity of essential oil from Coleus aromaticus and its pure isolated constituent thymol against larvae of Culex tritaeniorhynchus, Aedes albopictus, and Anopheles subpictus. The chemical composition of the essential oil was analyzed using gas chromatography-mass spectroscopy. A total of 14 components of the essential oil of C. aromaticus were identified. The major chemical components identified were thymol (82.68%), terpinen-4-ol (3.2%), and trans-Caryophyllene (3.18%). Twenty-five early third instar larvae of C. tritaeniorhynchus, A. albopictus, and A. subpictus were exposed and assayed in the laboratory. Thymol and essential oil were tested in concentrations of 10, 20, 30, 40, and 50 and 30, 60, 90, 120, and 150 ppm, respectively. The larval mortality was observed after 24 h of treatment. The thymol had a significant toxic effect against early third-stage larvae of C. tritaeniorhynchus, A. albopictus, and A. subpictus with an LC50 values of 28.19, 24.83, and 22.06 μg/mL respectively, whereas the essential oil of C. aromaticus had an LC50 values of 72.70, 67.98, and 60.31 μg/mL, respectively. No mortality was observed in controls. The Chi-square values were significant at p < 0.05 level. The result indicated that the essential oil of C. aromaticus and the isolated constituent have a potential for use in control of C. tritaeniorhynchus, A. albopictus, and A. subpictus larvae and could be useful in search of newer, safer, and more effective natural compounds as larvicides.

Ovicidal, repellent, adulticidal and field evaluations of plant extract against dengue, malaria and filarial vectors

Mosquitoes are insect vectors responsible for the transmission of parasitic and viral infections to millions of people worldwide, with substantial morbidity and mortality. Infections transmitted by mosquitoes include malaria, yellow fever, chikungunya, filariasis and other arboviruses. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The adulticidal activities of crude hexane, benzene, ethyl acetate, acetone and methanol leaf extracts of Acalypha alnifolia were assayed for their toxicity against three important vector mosquitoes, viz., Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The adult mortality was observed after 24 h of exposure. All extracts showed moderate adulticide effects; however, the highest adult mortality was found in methanol extract were observed. The LC(50) values of A. alnifolia leaf extracts against adulticidal activity of (hexane, benzene, ethyl acetate, acetone and methanol) A. aegypti, A. stephensi and C. quinquefasciatus were the following: A. aegypti values were 371.87, 342.97, 320.17, 300.86 and 279.75 ppm; A. stephensi values were 358.35, 336.64, 306.10, 293.01 and 274.76 ppm; C. quinquefasciatus values were 383.59, 354.13, 327.74, 314.33 and 291.71 ppm. The results of the repellent activity of hexane, benzene, ethyl acetate, acetone and methanol extract of A. alnifolia plant at three different concentrations of 1.0, 3.0, and 5.0 mg/cm(2) were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, this plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. Mean percent hatchability of the ovicidal activity was observed 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100 % with methanol extract of A. alnifolia was exerted at 125 and 300 ppm. The larval density was decreased after the treatment of plant extracts at the breeding sites (water bodies system) of vector mosquitoes, and hence, these plant extracts are suitable alternatives of synthetic insecticides for mosquito vector management.These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes. This study provides first report on the mosquito ovicidal, repellent and adulticidal activities of these plant extracts against mosquito vector species from India.

Ovicidal activity of Atalantia monophylla (L) Correa against Spodoptera litura Fab. (Lepidoptera: Noctuidae)

OBJECTIVE

To evaluate the efficacy of Atalantia monophylla (A. monophylla) leaf in different solvent crude extracts and fractions against eggs of Spodoptera litura (S. litura).

METHODS

Hexane, ethyl acetate and chloroform solvent extracts of A. monophylla leaf and 12 fractions from hexane extract were screened at 5.0%, 2.5%, 1.0% and 0.5% for crude extracts and 1 000, 500, 250 and 125 mg/kg for fractions against the eggs of S. litura for the ovicidal activity. LC50 and LC90 were calculated using probit analysis.

RESULTS

Hexane crude extract showed maximum ovicidal activity of 61.94% at 5.0% concentration with a correlation value of r (2)=0.81, and least LC50 value of 3.06%. Hexane extract was fractionated using silica gel column chromatography and 12 fractions were obtained. Fraction 9 was active which showed maximum ovicidal activity of 75.61% at 1 000 mg/kg with the LC50 value of 318.65 mg/kg and LC90 value of 1 473.31 mg/kg. In linear regression analysis, significant and high correlation (r (2)=0.81%) was seen between concentration and ovicidal activity of hexane crude extracts and its active fraction.

CONCLUSIONS

As per our knowledge, this is the first report for ovicidal activity of A. monophylla against S. litura, A. monophylla could be used for the management of S. litura and other insect pests.

Larvicidal, ovicidal and pupicidal activities of Gliricidia sepium (Jacq.) (Leguminosae) against the malarial vector, Anopheles stephensi Liston (Culicidae: Diptera)

OBJECTIVE

To investigate the potentiality of mosquitocidal activity of Gliricidia sepium (G. sepium) (Jacq.) (Leguminosae).

METHODS

Twenty five early third instar larvae of Anopheles stephensi (An. stephensi) were exposed to various concentrations (50-250 ppm) and the 24 h LC(50) values of the G. sepium extract was determined by probit analysis. The ovicidal activity was determined against An. stephensi to various concentrations ranging from 25-100 ppm under laboratory conditions. The eggs hatchability was assessed 48 h post treatment. The pupicidal activity was determined against An. stephensi to various concentrations ranging from 25-100 ppm. Mortality of each pupa was recorded after 24 h of exposure to the extract.

RESULTS

Results pertaining to the experiment clearly revealed that ethanol extract showed significant larvicidal, ovicidal and pupicidal activity against the An. stephensi. Larvicidal activity of ethanol extracts of G. sepium showed maximum mortality in 250 ppm concentration (96.0±2.4)%. Furthermore, the LC(50) was found to be 121.79 and the LC(90) value was recorded to be 231.98 ppm. Ovicidal activity of ethanol extract was assessed by assessing the egg hatchability. Highest concentration of both solvent extracts exhibited 100% ovicidal activity. Similarly, pupae exposed to different concentrations of ethanol extract were found dead with 58.10% adult emergence when it was treated with 25 ppm concentration. Similarly, 18.36 (n=30; 61.20%); 21.28(70.93) and 27.33(91.10) pupal mortality was recorded from the experimental pupae treated with 50, 75 and 100 ppm concentration of extracts. Three fractions have been tested for their larvicidal activity of which the Fraction 3 showed the LC(50) and LC(90) values of 23.23 and 40.39 ppm. With regard to the ovicidal effect fraction 3 showed highest ovicidal activities than the other two fractions. Furthermore, there were no hatchability was recorded above 50 ppm (100% egg mortality) in the experimental group. Statistically significant pupicidal activity was recorded from 75 ppm concentration.

CONCLUSIONS

From the results it can be concluded the crude extract of G. sepium is an excellent potential for controlling An. stephensi mosquito. It is apparent that, fraction 3 possess a novel and active principle which could be responsible for those biological activities.

Integration of botanicals and microbials for management of crop and human pests

Insect pests inflict damage to humans, farm animals, and crops. Human and animal pests put more than 100 million people and 80 million cattle at risk worldwide. Plant pests are the main reason for destroying one fifth of the world's total crop production annually. Anopheles stephensi is the major vector of human malaria in Middle East and South Asian regions. Spodoptera litura is a polyphagous pest of vegetables and field crops. Because of its broad host range, this insect is also known as cluster caterpillar, common cutworm, cotton leafworm, tobacco cutworm, tobacco caterpillar, and tropical armyworm. The toxic effects of methanolic extract of Senna alata and microbial insecticide, Bacillus sphericus, were tested against the polyphagous crop pest, S. litura (Fab.), and the malarial vector, A. stephensi. Results from the present study states that B. sphericus is more toxic than S. alata to both the crop pest and mosquito. The malarial vector, A. stephensi, was found to be susceptible than the crop pest, S. litura. Both the botanical and microbial insecticide showed excellent larvicidal, pupicidal, longevity, fecundity, and growth regulatory activities. Median lethal concentrations of B. sphericus and methanolic extract of S. alata observed to kill the third instar of S. litura were 0.52 and 193.09 ppm and A. stephensi were 0.40 and 174.64 ppm, respectively.