Ovicidal Activity Research Articles

Evaluation of Artemisia absinthium L. Essential Oil as a Potential Novel Prophylactic against the Asian Citrus Psyllid Diaphorina citri Kuwayama

Interest in developing novel crop protectants has increased in the recent decade due to the harmful effects of synthetic pesticides on humans and the environment. Diaphorina citri threatens the citrus industry worldwide and is the primary vector of phloem-limited bacterium (HLB). However, there is no available cure for HLB. Diaphorina citri management mainly depends on the use of synthetic insecticides, but their massive application leads to resistance in pest populations. Therefore, alternative pest management strategies are needed. Our results indicated that fewer D. citri adults settled on plants treated with AAEO than on control 48 h after release. The psyllids fed on citrus leaves treated with AAEO significantly reduced the honeydew production compared to the control. The AAEO showed potent ovicidal activity against the D. citri eggs with LC50 5.88 mg/mL. Furthermore, we also explored the fitness of D. citri on AAEO-treated and untreated Citrus sinensis by using two-sex life table tools. Our results revealed that the intrinsic rate of increase (r) was higher on untreated seedlings (0.10 d−1) than those treated with an LC20 concentration of AAEO (0.07 d−1). Similarly, the net reproductive rate (R0) was higher for untreated seedlings (14.21 offspring) than those treated (6.405 offspring). Furthermore, the AAEO were safer against Aphis mellifera, with LC50 35.05 mg/mL, which is relatively higher than the LC50 24.40 mg/mL values against D. citri. The results indicate that AAEO exhibits toxic and behavioral effects on D. citri, which can be a potential candidate for managing this pest.

Ovicidal Effect on Haemonchus contortus of Extract Partitions Shrubby Plants of the Tropical Dry Forest and Potentially Active Compounds Identification by UHPLC-Q/Orbitrap/MS/MS

The in vitro anthelmintic effect of the extracts on Haemonchus contortus (H. contortus) of three forage species in the tropical dry forest is known; however, there is no information about the effects of the extract partitions, nor their chemical composition. The objectives of this study were to evaluate the in vitro ovicidal activity of H. contortus in extract partitions of the species Gliricidia sepium, Leucaena leucocephala, and Pithecellobium dulce, and to identify the compounds present in the extract partitions with the highest activity by employing ultra HPLC Quadrupole orbitrap mass spectrometry. Four extract partitions, hexane, dichloromethane, ethyl acetate, and hydroethanolic from the three forage species were assessed in an inhibition of egg hatching (IEH) assay. The extract partitions with the highest anthelmintic activity (AA) were subjected to analysis, from which the tentative identification of the compounds was established. The extract partitions, including dichloromethane from Gliricidia sepium, ethyl acetate from Leucaena leucocephala, and hydroethanolic from Pithecellobium dulce showed a greater anthelmintic effect, with IC50 values of 0.39, 0.86, and 0.27 mg/mL for the IEH, respectively. Metabolites with in vitro AA potential included flavonoids, fatty acid esters, hydroxycinnamic acids, organic oxygenated compounds of the benzene class and substituted derivatives, phenolic glycosides, and phenols.

In vitro ovicidal effect of p-coumaric acid from Acacia bilimekii aerial parts against Haemonchus contortus

Acacia bilimekii is a plant with a high content of protein, fibre, and condensed tannins, making it an excellent feed for small ruminants with anthelmintic potential. This study aimed to evaluate the ovicidal activity of a hydroalcoholic extract (Ab-HA) and fractions from A. bilimekii aerial parts on Haemonchus contortus. The ovicidal activity of the Ab-HA extract and its fractions obtained by chromatographic fractionation were evaluated through the egg hatching inhibition (EHI) test. The results showed that the Ab-HA extract had 91% EHI at 20,000 µg/mL with a mean effective concentration (EC50) of 9260 µg/mL. After liquid–liquid fractionation of Ab-HA extract, the aqueous fraction (Ab-Aq) did not show ovicidal activity, whereas the organic fraction (Ab-EtOAc) showed a better EHI than the Ab-HA extract (98.9% at 2500 µg/mL). Then, the chemical fractionation of Ab-EtOAc allowed obtaining six bioactive fractions (AbR12–17) with an EHI greater than 90% at 1500 µg/mL. The best treatment was AbR15 (98.7% EHI at 750 µg/mL). Chemical analysis by HPLC-PDA of AbR15 indicated the presence of p-coumaric acid and the flavone luteolin as major compounds. Additionally, the commercial p-coumaric acid standard was evaluated in the EHI assay and showed an EHI of 97% at 62.5 µg/mL. Meanwhile, the confocal laser scanning microscopy analysis demonstrated a colocalization effect between p-coumaric acid and the H. contortus embryonated eggs. These results indicate that due to their major chemical compounds (including p-coumaric acid), the aerial parts of the plant A. bilimekii, could be considered as natural potential tool for controlling haemonchosis in small ruminants.

Ovicidal Activity and Phytochemical Analysis of some Spontaneous Plants Extracts Against Ectomyelois ceratoniae (Zeller) Lepidoptera: Pyralidae

The use of aqueous extracts as alternative solutions that significantly reduce to the damage caused by pests like Ectomyelois ceratoniae. This work presents in-vitro tests that are successfully applied to evaluate the ovicidal activity of four spontaneous plants aqueous extracts, as, Rosmarinus officinalis, Peganum harmala, Thymus vulgaris and Artemisia herba-alba againt the moth eggs. The results showed a highly significant effect for T. vulgaris and A. herba-alba, sometimes reaching 100%, followed by R. officinalis, then P. harmala which was not present any effect on this pest eggs. T. vulgaris and A. herba-alba showed a strong inhibition of egg hatching. It exceeds 93 % mortality for a concentration of 0.12 mL/mL. For R. officinalis at 0.18 mL/mL concentration present a 72% mortality. While at 0.12 mL/mL, the mortality was 40%.The lethal doses to inhibit 50 and 90 % of the eggs were estimated to confirm the efficiency of the aqueous extracts , stronger results shows, respectively (0.014 mL and 0.062 mL) from T. vulgaris and (0.019 mL and 0.069 mL) from A. herba-alba. This work originally explores the benefits of some kinds of plants that are largely available and inexpensive for the biotreatment of carob motheggs.

Ovicidal potential of plant extract mixtures against the Asian spongy moth (Lymantria dispar asiatica)

The Asian spongy moth (ASM, Lymantria dispar asiatica) is a destructive pest of forests, agricultural fields, and urban areas. Plant extract mixtures were evaluated as alternative tools for integrated pest management targeting the overwintering eggs of ASM. When formulated with an adjuvant able to penetrate the hairy egg mass, plant extract mixtures inhibited egg hatching. The extract mixture (cinnamon extract 5% + citronella oil 10% + citrus oil 30% + derris extract 10% + neem extract 20% + penetrating surfactant 25%) with the highest ovicidal activity (97.6% mortality) is a potential botanical insecticide for use against ASM eggs. Susceptibility to mortality from plant extract mixtures increased with egg maturation. Optimal timing for control of overwintering ASM eggs corresponded to the period in spring when larvae inside eggs were fully differentiated. These results will help improve control efficacy with a day-degree model that predicts egg hatch as well as future development nano-formulations.

Brief report first report of the in vitro ovicidal activity of camel milk and its fractions on zoonotic-liver fluke (Fasciola gigantica) eggs

Fasciola gigantica is one of the worldwide parasites that cause livestock and human illnesses. Chemotherapy is now the primary therapeutic option for its treatment. Drug abuse has led to the emergence of drug-resistant strains. As a result, there is an urgent need to discover natural and efficient anthelmintics against Fasciola spp. The study aims to evaluate the ovicidal activities of camel milk and its fractions on F. gigantica eggs. In the in vitro assay of F. gigantica eggs were submitted to different concentrations (0.5% and 1%) of camel milk fractions; Camel Milk Whey (CMW), Camel Milk Casein (CMC), and Skimmed Camel Milk (SCM) as well as a positive control (PC) of Nitroxynil (100 mg/ml) and a negative control (NC) with physiological saline. The Egg Hatching Assay (EHA) results showed that camel milk fractions exhibited ovicidal activity, especially CMW, and CMC, which showed 97.58 ± 0.58 and 96.9 ± 1.99 ovicidal activity, respectively, at a concentration of 1% after 15 days of treatment compared to PC, which exhibited 91.75 ± 4.95 ovicidal activity. The egg hatching ratios were 1.67% and 2.33% for CMW and CMC, respectively, compared to 70.17% for the NC and 6% for the PC. The LC50 values for CMW and CMC on the 15th day of treatment were 0.20 and 9.13, respectively. From the results above, we can infer that camel milk and its fractions are promising as a new alternative for fascioliasis control.

Toxicity, Ovipositional Behaviour and Electrophysiological Response of Rice Moth <i>Corcyra cephalonica</i> (Stainton) Adults to Essential Oils

Rice moth Corcyra cephalonica (Stainton) is a serious pest on storage commodities. The management of C. cephalonica relies on the use of chemical pesticides. Insecticide resistance and its effect on nontarget demand for compounds that are clean, and green. Essential oils (EOs) viz., Trachyspermum ammi (Ajowan), Piper betle (betel), Eucalyptus citriodora (citridora), Cymbopogan nardus (citronella), Pelargonium graveolens (geranium), Rosmarinus officinalis (rosemary) and Ocimum basilicum (sweet basil) were investigated for their cidal activities against the egg and adult stages of C. cephalonica. On ovicidal action, among the EOs tested P. betle was found to have higher cidal action to eggs (EC50 3.79 mg/ dm3), followed by T. ammi EO (EC50 4.17 mg/ dm3). P. graveolens and P. betle EOs caused the highest fumigant toxicity in adults with the lowest LC50 values (12.58 and 18.01 mg/ dm3). All the EOs tested caused an antennal response in C.cephalonica female adults. Among the Eos, R. officinalis and P. graveolens elicited the highest antennal response in female moths (1.3 mV and 0.84 mV). In the behavioural assay, the female moths showed reduced preference for the oviposition substrate treated with EOs. The desirable cidal, physiological and behavioural response of EOs on C. cephalonica adults makes them a viable alternative to synthetic pesticides.

Artemisia vulgaris anthelmintic activities to ova and adult stages of Fasciola gigantica in vitro.

Fasciolosis due to Fasciola gigantica is endemic to tropical countries and Fasciola hepatica in temperate climates, highly detrimental to livestock and known as foodborne zoonotic diseases. The strategic control of the disease is mainly the use of chemical anthelmintic. This study aimed to evaluate the anthelmintic properties of Artemisia vulgaris extract on the ova and adult stages of F. gigantica. Samples were collected from the Ampel Abbatoir, Boyolali District, Central Java, Indonesia. The ova from 20-gallbladders of cattle which were naturally infected with F. gigantica and 270 living F. gigantica worms were used in this study. The ovicidal assay was performed by incubating the ova with A. vulgaris in different concentrations, that is, 5%, 2.5%, and 1.25% for 5, 9, 11, 14, and 16 days. The efficacies were evaluated by quantification of ova degeneration during developmental stages in different time points and egg-hatch assay. The flukicidal effects were observed by mortality assay in 5, 10, 20, 40, 80, 160, 320, and 640 min incubations followed by scanning electron microscopy for surface morphology and histology of the fluke's transversal sections. The concentration of 5% A. vulgaris showed the strongest ovicidal activities. The percentage of hatching ova on day 16 at concentrations of 5%, 2.5%, and 1.25% were 3.33%, 6.67%, and 16.67%. These ova hatch assay showed a significant reduction (p < 0.001) compared to untreated control. The flukicidal effect was significant (p < 0.001) at a concentration of 20%, with a mortality rate reaching 66.67% in the 40 min of incubation time. The surface properties of the adult worms, including the spine, tegument, acetabulum, intestine, and vitelline follicles, were disintegrated. The results showed that A. vulgaris has the potential ovicidal and flukicidal properties to F. gigantica. The active compounds remained necessary to be elucidated further and its modes of action would be interesting to be predicted by molecular docking modeling.

Mosquito larvicidal, pupicidal and ovidical effects of the different extracts of the leaves of Peltophorum pterocarpum against Aedes aegypti and Culex quinquefasciatus

BackgroundMosquitoes are vectors for several diseases like dengue, chikingunea, malaria etc. The three important mosquito species in India are Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. Several plant extracts and phytoconstituents have been tested for antimosquito activity. In our present investigation, we have studied, the mosquito larvicidal, pupicidal and ovicidal activities of the successive n-hexane, chloroform and methanol extracts of leaves of Peltophorum pterocarpum (Fabaceae).ResultsThe two mosquito species studied were Ae. agypti and Cx. quinquefasiatus. The larvicdial activity on both mosquitoes was in the order methanol > chloroform > n-hexne. The LC 50 values for these extracts were 111.77 and 158.93 ppm (methanol extract), 170.74 and 169.18 ppm (chloroform extract), 219.14 and 203.48 ppm (n-hexane) respectively for both mosquitoes. The pupicidal activity was in the order chloroform > methanol > n-hexne. The LC50 values for these extracts were 226.01 and 204.041 ppm (chloroform extract), 235.40 and 239.50 ppm (methanol extract), 303.07 and 284.04 ppm (n-hexane,) respectively. The ovicidal activity of the extracts against both the mosquitoes studied was not appreciable.ConclusionThe methanol extract revealed higher larvicidal activity, while the chloroform extract showed higher pupicidal activity for both the mosquitoes. Hence, the methanol and chloroform extracts of the leaves of the plant may be taken up for further studies. This is the first detailed report on the antimosquito activity of the successive extracts of the leaves of Peltophorum perocarpum against the two mosquito species Ae. aegypti and Cx. quinquefasciatus.

Potential control of the infective stage of Taenia pisiformis using Bacillus thuringiensis GP526 strain

The GP526 strain of Bacillus thuringiensis has been referred as an in vitro helminthicide on various stages of Dipylidium caninum and Centrocestus formosanus. Our study addresses the in vitro ovicidal activity of GP526 strain spore-crystal complex on Taenia pisiformis eggs, evaluating induced damage microscopically. The eggs exposed to the total extract containing spores and crystals show damage after 24 hours, with loss of integrity on the eggshell, and an ovicidal activity of 33% at 1mg/ml. The destruction of the embryophore was observed after 120 h with a 72% of ovicidal activity at 1 mg/ml. The LC50 was 609.6 μg/ml, dose that causes a 50% of lethality on the hexacanth embryo, altering the oncosphere membrane. The spore-crystal proteins were extracted, and the protein profile was obtained by electrophoresis, finding a major band of 100 kDa suggestive of an S-layer protein, since an S-layer was immunodetected in both, spores and extracted proteins. The protein fraction containing the S-layer protein presents adhesion to the T. pisiformis eggs, and 0.4 mg/ml of the protein induces a lethality of 21.08% at 24 h. The characterization of molecular mechanisms of ovicidal activity will be an important contribution, so the characterization of the proteins that make up the extract of the GP526 strain, would be useful to support the biological potential for control of this cestodiasis and other parasitosis. B. thuringiensis is shown as a potent helminthicide on eggs, with useful potential for biological control of this cestodiasis.

Molluscicidal activities of green-synthesized Alstonia congensis silver nanoparticles

Objective: To evaluate the efficacy of Alstonia congensis green-synthesized nanoparticles as a molluscicide against snail hosts of trematodes. Methods: The ethanolic leaf extract of Alstonia congensis was used to synthesize silver nanoparticles. The formulation was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, and scanning electron microscope/energy-dispersed X-ray. The ovicidal and molluscicidal activities of the Alstonia congensis extract and its nanoparticles were tested against Physa acuta and Bulinus forskalii at different concentrations. Results: The green-synthesized nanoparticles inhibited embryonic development within the egg masses of the two snails in all the tested concentrations. Alstonia congensis extract did not show molluscicidal properties against adult Physa acuta but showed a very weak activity against Bulinus forskalii. Moreover, the synthesized nanoparticles showed significantly high molluscicidal activity against adult snails within 5-40 min of exposure in a concentration-dependent manner (P&lt;0.05). Conclusions: The Alstonia congensis-based nanoparticles show molluscicidal activities against adults and embryos of Physa acuta and Bulinus forskalii, and can be further explored as a potent molluscicide for the control of intermediate host of trematode parasites.

Toxic Effects of Perilla frutescens (L.) Britt. Essential Oil and Its Main Component on Culex pipiens pallens (Diptera: Culicidae).

Sustainable control of mosquitoes, vectors of many pathogens and parasites, is a critical challenge. Chemical insecticides are gradually losing their effectiveness because of development of resistance, and plant metabolites are increasingly being recognized as potential alternatives to chemical insecticides. This study aimed to analyze the main components of Perilla frutescens essential oil (PE-EO), investigate the specific activity of PE-EO as a botanical insecticide and mosquito repellent, and explore whether its main constituents are potential candidates for further research. The larvicidal activity assay showed that LC50 of PE-EO and 2-hexanoylfuran was 45 and 25 mg/L, respectively. In the ovicidal activity assay, both 120 mg/L PE-EO and 80 mg/L 2-hexanoylfuran could achieve 98% egg mortality. Moreover, PE-EO and 2-hexanoylfuran showed repellency and oviposition deterrence effects. Notably, 10% PE-EO maintained a high rate of protection for 360 min. Although PE-EO and its main component had certain toxic effects on zebrafish, no significant harmful effects were detected in human embryonic kidney cells. Therefore, perilla essential oil is an effective agent for mosquito control at several life stages and that its main component, 2-hexanoylfuran, is a potential candidate for developing novel plant biopesticides.

Susceptibility of Pre-adult Biological Stages of Mythimna separata (Walker) (Lepidoptera: Noctuidae) to Three Entomopathogenic Fungi (Hypocreales)

Armyworms are polyphagous insect pests of agricultural crops. Their population is usually managed below threshold level using insecticides. However, a single control measure is insufficient to attain a sustainable pest management. Hence, this research was conducted to assess the three species of entomopathogenic fungi as potential biological control agents against Mythimna separata (Walker) or paddy armyworm. Dose mortality assays were conducted to determine the pathogenicity of Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metschn.) Sorokin, and Metarhizium rileyi (Farlow) Kepler, S.A. Rehner and Humber against various biological stages of M. separata including egg, 1st to 6th larval instars, prepupa, and pupa. These entomopathogenic fungi did not have ovicidal activity but affected the survivorship of the resulting neonates. Exposure of eggs to B. bassiana, M. anisopliae, and M. rileyi infected 64, 60, and 70 % of the resulting neonates, respectively. Adult emergence was also reduced in fungal-treated (29% in B. bassiana, 10% in M. anisopliae, and 10% in M. rileyi) as compared with 64% in control. At 7 d after treatment, M. rileyi applied at 1 x 105 to 1 x 109 conidia/mL was the most pathogenic causing a mean larval mortality of up to 70% as compared to B. bassiana and M. anisopliae with less than 10% mortality. Among the larval instars, the 1st, 2nd, and 3rd were the most susceptible to fungal infection. Conidial concentrations (1 x 108 and 1 x 109 conidia/mL) induced the highest larval mortalities as compared to the lower conidial concentrations (1 x 105 and 1 x 107 conidia/mL) of the entomopathogenic fungi. The prepupal and pupal stages were also slightly susceptible to the entomopathogenic fungi. These findings showed the pathogenic effect of the entomopathogenic fungi particularly M. rileyi to M. separata.

The efficacy of Pajanelia longifolia (Willd.) K. Schum leaf extracts against the malaria vector Anopheles stephensi Liston (Diptera: Culicidae)

Pajanelia longifolia (Willd.) K. Schum is a medicinal deciduous tree with a history of traditional use. The use of biologically active plant materials with mosquitocidal characteristics has piqued the curiosity of scientists worldwide. The goal of this study was to see if P. longifolia crude extracts (in petroleum ether, chloroform, and methanol) had any ovipositional deterrent, ovicidal, larvicidal, or pupicidal activity against Anopheles stephensi Liston. The LC50 and LC90 values were determined by varying the concentrations of the leaf extracts. The highest oviditerrence activity (98.58% at 900 ppm), 100% ovicidal activity at 1700 ppm, 100% larvicidal activity at 1300 ppm, and pupicidal activity at 2100 ppm were found in the methanol extract. This study's findings suggest that the methanol extract of P. longifolia could be used to control mosquitoes. These discoveries could aid in the development of a potential alternate source of mosquito control. These kinds of biological insect control methods reduce the need for synthetic pesticides. The study proves that controlling mosquitoes in their infancy is easier and more effective than controlling the adult mosquitoes.

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.

Encapsulation of silver nano crystals using Salvinia molesta against the Anopheles stephensi and oxidative stress enzyme activity of larvivorous fish

Anopheles mosquitoes, which are the main carriers of the disease throughout India, Asia, and the Middle East, are the ones that cause malaria. The role of water predators in mosquito aquatic stage regulation is still recognized. With the use of synthetic insecticides, the environment became contaminated and insects developed high resistance to chemical pesticides. Based on our outline, we anticipated an innovative technique of bioencapsulated silver nanoparticles (AgNPs) using Salvinia molesta, which would perform as a reducing and stabilizing agent. Bioencapsulated-AgNPs existed and were classified using a variety of physiochemical techniques. In bioassays, the LC50 values of S. molesta aqueous extract against Anopheles stephensi range from 240.247 (1st instar larvae) - 428.851 ppm (pupae), LC50 of S. molesta-encapsulated AgNPs ranges from 20.010 (1st instar larvae) to 35.676 ppm (pupae). An experiment with S. molesta extract and encapsulated AgNPs was conducted in the open environment, and the larval reduction of mosquitoes was 100% after 72 h. In the ovicidal activity of An. stephensi, hatched eggs were reduced by 100% when treated with 40 ppm of encapsulated AgNPs and 500 ppm of S. molesta extract and encapsulated AgNPs, which significantly reduced the life span of malarial mosquito adults. Furthermore, we investigated the predatory ability of the larvivorous fish Aplocheilus blockii against third and fourth instar larvae of An. stephensi in laboratory conditions using ultra-low doses of bioencapsulated-AgNPs. Regarding non-target impact, in a conventional laboratory environment, the predation efficacy of the larvivorous fish A. blockii, was 58.58% and 54.78% against the 3rd and 4th instar larvae of An. stephensi, respectively. In bioencapsulated AgNPs-contaminated circumstances, fish predation was amplified to 78.18% and 75.54%, respectively. A. blockii was exposed to sublethal concentrations of AgNPs, namely 5, 10, and 15 g/ml, in enzymatic assays to assess changes in GST and AChE activity after 16 days. This study advances our understanding of the contagiousness of water-floating fern-conveyed insecticides and bioencapsulated AgNPs against therapeutically important insects, allowing us to recommend the proven materials as effective candidates to evolve the most recent and cost-effective pest management tools, and the long-term use of this larvivorous fish during wetlands and associated An. stephensi larval ecologies in various parts of the country is proposed.

Antihelminthic Activity of Lophira Lanceolata on Heligmosomoides polygyrus Using an Automated High-Throughput Method.

There are about 13 parasitic infections that are responsible for significant morbidity and mortality but have not received the attention they deserve; thus, they are now known as "neglected tropical diseases" (NTDs). This study was aimed at evaluating the antihelminthic activities of Lophira lanceolata using an automated high-throughput method. The antihelminthic activity effect of the extracts against H. polygyrus was determined using an automated high-throughput method. For the egg-hatching test, 100 μL of embryonated egg suspension (60 eggs) was added to 100 μL of various concentrations of extracts, levamisole, and 1.5% DMSO in a 96-well round-bottom microtitre plate. After mixing, the 96-well microplate was placed in WMicroTracker and incubated for 24 h at 25°C; the movements were recorded every 30 minutes. The same procedure was used for the larval motility assays, where 100 μL of L1 or L2 larvae (50 larvae) were put in contact with 100 μL of various concentrations of extracts. The ovicidal activity (hatching) had an IC50 of 1.4 mg/mL for the ethanol extract. The aqueous and ethanol extracts of L. lanceolata showed larvicidal activity on the L1 larvae with IC50 of 1.85 mg/mL and 2.4 mg/mL, respectively, as well as on the L2 larvae with IC50 values of 1.08 mg/mL and 1.02 mg/mL for the aqueous and ethanol extracts, respectively. These results showed that the aqueous extract exhibited a stronger inhibitory power on the hatching rate of parasites than ethanol extracts, while the contrary effect was observed for the larval motility assays. This study provides scientific data on the use of L. lanceolata by the local population for the treatment of helminthiases. However, in vivo and toxicity tests are necessary to assess its activity and safety.

Insecticidal activities of Streptomyces sp. KSF103 ethyl acetate extract against medically important mosquitoes and non-target organisms

A potentially novel actinobacterium isolated from forest soil, Streptomyces sp. KSF103 was evaluated for its insecticidal effect against several mosquito species namely Aedes aegypti, Aedes albopictus, Anopheles cracens and Culex quinquefasciatus. Mosquito larvae and adults were exposed to various concentrations of the ethyl acetate (EA) extract for 24 h. Considerable mortality was evident after the EA extract treatment for all four important vector mosquitoes. Larvicidal activity of the EA extract resulted in LC50 at 0.045 mg/mL and LC90 at 0.080 mg/mL for Ae. aegypti; LC50 at 0.060 mg/mL and LC90 at 0.247 mg/mL for Ae. albopictus; LC50 at 2.141 mg/mL and LC90 at 6.345 mg/mL for An. cracens; and LC50 at 0.272 mg/mL and LC90 at 0.980 mg/mL for Cx. quinquefasciatus. In adulticidal tests, the EA extract was the most toxic to Ae. albopictus adults (LD50 = 2.445 mg/mL; LD90 = 20.004 mg/mL), followed by An. cracens (LD50 = 5.121 mg/mL; LD90 = 147.854 mg/mL) and then Ae. aegypti (LD50 = 28.873 mg/mL; LD90 = 274.823 mg/mL). Additionally, the EA extract exhibited ovicidal activity against Ae. aegypti (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), Ae. albopictus (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), and An. cracens (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), evaluated up to 168 h post-treatment. It displayed no toxicity on the freshwater microalga Chlorella sp. Beijerinck UMACC 313, marine microalga Chlorella sp. Beijerinck UMACC 258 and the ant Odontoponera denticulata. In conclusion, the EA extract showed promising larvicidal, adulticidal and ovicidal activity against Ae. aegypti, Ae. albopictus, An. cracens, and Cx. quinquefasciatus (larvae only). The results suggest that the EA extract of Streptomyces sp. KSF103 has the potential to be used as an environmental-friendly approach in mosquito control. The current study would serve as an initial step toward complementing microbe-based bioinsecticides for synthetic insecticides against medically important mosquitoes.

Larvicidal, Ovicidal, Ovipositional deterrent and adulticidal activity of Tagetes erecta and Cymbopogon nardus against Culex quinquefasciatus and their GCMS analysis

Culex quinquefasciatus (C. quinquefasciatus) is found in tropical and warm temperate regions and can transmit several viral diseases like Elephantiasis or Filariasis, West Nile fever, St. Louis encephalitis, and Japanese encephalitis causes millions of deaths every year. Long term use of synthetic pesticides to control mosquitoes, has led to the emergence of insecticide resistant vector, ecological imbalance, and harm to mammals, water contamination, toxicity to non-target organisms and residual effects. Therefore, plant based products are being searched and evaluated all over the world as an alternative control. The present study evaluated the efficacy of essential oil of Tagetes erecta (T. erecta) and Cymbopogon nardus (C. nardus) as a larvicidal, ovicidal, ovipositional deterrency and adulticidal agent against C. quinquefasciatus. Various bioassays against the IVth instar larvae, eggs and adults of C. quinquefasciatus were carried out. Five different concentrations of 10, 20, 40, 80,160, 320, 640 ppm was prepared for T. erecta whereas 20, 40, 80,160,320, 640, 1280 ppm concentrations were prepared for C. nardus essential oil to get LC50. Mortality data was calculated by Logprobit method of Finney using SPSS 16 (SPSS 2010) following Abbott method. The GCMS analysis of the essential oil of T. erecta and C. nardus was also conducted to estimate the presence of bioactive compunds in the essential oils. The essential oil of T. erecta and C.nardus, showed LC50 at 42.02 ppm and 160.29 ppm respectively after 24 hours. Whereas LC50 after 48 hrs is recorded at 39.25 ppm in T. erecta and 94.39 ppm in C. nardus against C. quinquefasciatus. At 40 ppm, T.erecta showed ovicidal activity with 40.99%, ovipositional activity with 57.80% and adulticidal activity with 88.00%. On the other hand, C. nardus at 160.29 ppm exhibited ovicidal activity with 77.63%, ovipositional activity with 73.33% and adulticidal activity with 73.6%. Many active phytochemicals was also found in the essential oil of T. erecta and C. nardus. It is concluded that the essential oil of both T. erecta and C. nardus are very effective mosquitocidal agent against C. quinquefasciatus. However T. erecta shows more effective results in comparision to C. nardus.

Phytochemical prospection, hemagglutinating and insecticidal activity of saline extracts from the seeds of Tamboril (Enterolobium contortisiliquum) Vell. Morong (Fabaceae) on Aedes aegypti (Diptera: Culicidae).

This study evaluated the insecticidal activity of crude extracts from Enterolobium contortisiliquum (Vell.) seeds on eggs and larvae of A. aegypti, and also verified the phytochemical profile and the presence of lectins in the extract. The 0.15 M NaCl saline solution was used as the extracting substance. For tests with eggs and larvae, the crude extract was used in its raw form (RCE) and boiled at 100º C for 5 min (BCE). Concentrations of 4.68; 9.37; 18.75; 28.13; 37.13 and 46.89 mg/mL, with distilled water as a negative control. Assays were performed in triplicate. The results were subjected to analysis of variance, Tukey's test and Log-Probit analysis to determine LC50 and LC90. BCE showed better results on eggs than RCE, managing to prevent the hatching of larvae in 81.66% ± 10.40 of treated eggs, at a concentration of 46.89 mg/mL. The LC50 and LC90 were set at 35.95 and 52.67 mg/mL, respectively. In tests with larvae, concentrations of 46.89 and 37.13 mg/mL, for RCE and BCE, caused 100% mortality in 24 hours of exposure. Larval mortality at the other concentrations increased with exposure time extending to 48 h. RCE, at 48 h exposure is the most promising extract on larvae (E = 72.77%, LC90 = 10.86 mg/mL). In RCE, the presence of lectins and secondary metabolites: flavonoids, xanthones and phenols, were detected. The results demonstrate the potential of E. contortisiliquum seed extracts with ovicidal and larvicidal action on A. aegypti.