Larvae Of Mosquito Culex Pipiens Research Articles

Chemical composition and bio-efficacy of agro-waste plant extracts and their potential as bioinsecticides against Culex pipiens mosquitoes

Mosquitoes are considered one of the most lethal creatures on the planet and are responsible for millions of fatalities annually through the transmission of several diseases to humans. Green trash is commonly employed in agricultural fertilizer manufacturing and microbial bioprocesses for energy production. However, there is limited information available on the conversion of green waste into biocides. This study investigates the viability of utilizing green waste as a new biopesticide against Culex pipiens mosquito larvae. The current study found that plant extracts from Punica granatum (98.4 % mortality), Citrus sinensis (92 % mortality), Brassica oleracea (88 % mortality), Oryza sativa (81.6 % mortality), and Colocasia esculenta (53.6 % mortality) were very good at killing Cx. pipiens larvae 24 h post-treatment. The LC50 values were 314.43, 370.72, 465.59, 666.67, and 1798.03 ppm for P. granatum, C. sinensis, B. oleracea, O. sativa, and C. esculenta, respectively. All plant extracts, particularly P. granatum extract (14.93 and 41.87 U/g), showed a significant reduction in acid and alkaline phosphate activity. Additionally, pomegranate extract showed a significant decrease (90 %) in field larval density, with a stability of up to five days post-treatment. GC–MS results showed more chemical classes, such as terpenes, esters, fatty acids, alkanes, and phenolic compounds. HPLC analysis revealed that the analyzed extracts had a high concentration of phenolic and flavonoid components. Moreover, there are many variations among these plants in the amount of each compound. The docking interaction showed a simulation of the atomic-level interaction between a protein and a small molecule through the binding site of target proteins, explaining the most critical elements influencing the enzyme's activity or inhibitions. The study's findings showed that the various phytochemicals found in agro-waste plants had high larvicidal activity and provide a safe and efficient substitute to conventional pesticides for pest management, as well as a potential future in biotechnology.

Photocatalytic activity of TiO2-Carbon nanocomposite films against Culex pipiens mosquito larvae under sunlight irradiation

Recent research has focused on developing eco-friendly nanomaterials to combat mosquito infestations. This study demonstrates the enhancement of titanium dioxide (TiO2) nanoparticles through the addition of carbon nanoparticles (C-NPs), significantly boosting their photocatalytic efficiency. This enhancement allows TiO2 to purify water and act as an effective pesticide. Formulated TiO2-carbon (TiO2–C) nanocomposite films showed increased photocatalytic activity against third-instar larvae of Culex pipiens under natural sunlight. The addition of C-NPs improved sunlight absorption and reduced electron-hole recombination rates compared to pristine TiO2 (P–TiO2), making it more effective for mosquito control. The superior performance of the TiO2–C nanocomposite was confirmed through X-ray Photoelectron Spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), and Photoluminescence emission (PL). These analyses confirmed successful carbon incorporation, expanding the absorption spectrum and enhancing optical properties. The UV–vis DRS spectra showed a decrease in the bandgap energy (Eg) of P–TiO2 from 3.2 eV to 3.1 eV, improving its photocatalytic effectiveness under natural sunlight. Bioactivity tests, including catalase activity, reduced glutathione (GSH) colorimetric assay, and superoxide dismutase (SOD) assay, along with microscopic and histological examinations of treated larvae, indicated that the TiO2–C nanocomposite effectively reduces the mosquito population and causes significant physiological damage and abnormalities in larval structures and midgut cells. These findings highlight the enhanced photocatalytic capabilities of the TiO2–C nanocomposite, making it a novel and effective solution for mosquito control with significant public health and environmental benefits.

Integrated de novo transcriptome of Culex pipiens mosquito larvae as a resource for genetic control strategies

We present a de novo transcriptome of the mosquito vector Culex pipiens, assembled by sequences of susceptible and insecticide resistant larvae. The high quality of the assembly was confirmed by TransRate and BUSCO. A mapping percentage until 94.8% was obtained by aligning contigs to Nr, SwissProt, and TrEMBL, with 27,281 sequences that simultaneously mapped on the three databases. A total of 14,966 ORFs were also functionally annotated by using the eggNOG database. Among them, we identified ORF sequences of the main gene families involved in insecticide resistance. Therefore, this resource stands as a valuable reference for further studies of differential gene expression as well as to identify genes of interest for genetic-based control tools.

Mutational analysis of the transmembrane α4-helix of Bacillus thuringiensis mosquito-larvicidal Cry4Aa toxin

Cry4Aa, produced by Bacillus thuringiensis subsp. israelensis, exhibits specific toxicity to larvae of medically important mosquito genera. Cry4Aa functions as a pore-forming toxin, and a helical hairpin (α4-loop-α5) of domain I is believed to be the transmembrane domain that forms toxin pores. Pore formation is considered to be a central mode of Cry4Aa action, but the relationship between pore formation and toxicity is poorly understood. In the present study, we constructed Cry4Aa mutants in which each polar amino acid residues within the transmembrane α4 helix was replaced with glutamic acid. Bioassays using Culex pipiens mosquito larvae and subsequent ion permeability measurements using symmetric KCl solution revealed an apparent correlation between toxicity and toxin pore conductance for most of the Cry4Aa mutants. In contrast, the Cry4Aa mutant H178E was a clear exception, almost losing its toxicity but still exhibiting a moderately high conductivity of about 60% of the wild-type. Furthermore, the conductance of the pore formed by the N190E mutant (about 50% of the wild-type) was close to that of H178E, but the toxicity was significantly higher than that of H178E. Ion selectivity measurements using asymmetric KCl solution revealed a significant decrease in cation selectivity of toxin pores formed by H178E compared to N190E. Our data suggest that the toxicity of Cry4Aa is primarily pore related. The formation of toxin pores that are highly ion-permeable and also highly cation-selective may enhance the influx of cations and water into the target cell, thereby facilitating the eventual death of mosquito larvae.

PENGENDALIAN LARVA NYAMUK Culex pipiens DENGAN EKSTRAK BIJI SRIKAYA (Annona squamosa L)

The Culex pipiens mosquito is one of the insects that carries diseases, especially filariasis. Mosquito control can be done using insecticides, either in the form of mosquito coils, electricity, or anti-mosquito lotion. However, the safety of insecticides on the market needs to be questioned because they contain chemicals. Therefore, alternative methods based on natural ingredients are needed, one of which is srikaya seeds. Therefore, this research was carried out to measure the biolarvicidal activity of sugar apple seed extract against Culex pipiens mosquito larvae. This research is an experimental study with treatment in the form of a concentration of srikaya seed extract, consisting of 0%, 3%, 6%, 9%, 12% and 15% with 3 repetitions. The data obtained was the average number of Culex pipiens mosquito larvae that died as a result of the treatment given. The percentage of larval death data was then calculated and the data was analyzed statistically using one-way anova with calculations using SPSS 23 software. The results of the study showed that differences in the concentration of sugar apple seed extract had a significant influence on the mortality of Culex pipiens mosquito larvae, where a concentration of 15% gave the highest average larval death. but not significantly different from concentrations of 12%, 9%, and 6%.

Random Mutational Analysis Targeting Residue K155 within the Transmembrane β-Hairpin of the Mosquitocidal Mpp46Ab Toxin.

Mpp46Ab is a mosquito-larvicidal pore-forming toxin derived from Bacillus thuringiensis TK-E6. Pore formation is believed to be a central mode of Mpp46Ab action, and the cation selectivity of the channel pores, in particular, is closely related to its mosquito-larvicidal activity. In the present study, we constructed a mutant library in which residue K155 within the transmembrane β-hairpin was randomly replaced with other amino acid residues. Upon mutagenesis and following primary screening using Culex pipiens mosquito larvae, we obtained 15 mutants in addition to the wild-type toxin. Bioassays using purified proteins revealed that two mutants, K155E and K155I, exhibited toxicity significantly higher than that of the wild-type toxin. Although increased cation selectivity was previously reported for K155E channel pores, we demonstrated in the present study that the cation selectivity of K155I channel pores was also significantly increased. Considering the characteristics of the amino acids, the charge of residue 155 may not directly affect the cation selectivity of Mpp46Ab channel pores. Replacement of K155 with glutamic acid or isoleucine may induce a similar conformational change in the region associated with the ion selectivity of the Mpp46Ab channel pores. Mutagenesis targeting the transmembrane β-hairpin may be an effective strategy for enhancing the ion permeability of the channel pores and the resulting mosquito-larvicidal activity of Mpp46Ab.

Behavioral and histopathological changes of Clarias gariepinus as a predatory fish against Culex pipiens larvae following exposure to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide

Summary Clarias gariepinus is one of the widespread culturable freshwater fish species in Africa, which is prevalent in various natural and human-made aquatic habitats including rice-fish system. This fish species displays predation potential on the aquatic stages of mosquitoes. Bensulfuron-methyl and quinclorac are herbicide active substances that have been extensively applied in rice culture in Egypt and other countries worldwide. This study assessed the adverse effects of sublethal concentration of a commercial herbicide formulation containing quinclorac and bensulfuron-methyl on the predation potential of C. gariepinus female and male predatory fish on Culex pipiens mosquito larvae. Also, stomach and intestine histopathology of the treated fish was investigated. The exposure of C. gariepinus to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide produced detrimental effects on prey consumption and histopathological changes in the stomach and intestine of the fish. The mosquito consumption by the treated female and male fish decreased significantly compared to the untreated fish of both sexes. The histological changes in the intestines were hyperplasia of the intestinal epithelium and goblet cells; edema of lamina propria and broad intestinal villi, and distortion in intestinal villi in comparison to control. The stomach histopathology changes were necrosis and sloughing of mucosal epithelium with severe damage of sub-mucosa. Thus, the tested herbicide at sublethal concentration on C. gariepinus decreased the prey consumption on mosquito larvae and caused histopathological alterations in the fish that may impair its digestive physiology. These findings suggest a threat of the tested herbicide to C. gariepinus survival and potential as a native successful biocontrol agent against Cx. pipiens larvae.

Larvicidal Effects of Citrus Peels Extracts against Culex Pipiens Mosquitoes

Background: Mosquitoes transmit severe diseases such as malaria, lymphatic filariasis, dengue fever, and yellow fever. These diseases result in significant morbidity and mortality in humans around the world. This study aimed to provide information on the larvicidal potential of different Citrus species peels against Culex mosquito larvae.Methods: Ethanol extracts of the peels of four Citrus species, such as Citrus sinensis (sweet orange), Citrus reticulata (tangerine), Citrus latifolia (lime), and Citrus paradisi (grape) fruits were tested for larvicidal properties against Culex pipiens at different concentration (3 mg, 5 mg, 7 mg and 8 mg in 100 mL) on 25 larva per concentration. Percentage mortality was recorded for each of the concentrations used. Results: Only Culex latifolia induced the death of all the mosquito larvae (100%) at 5 mg/mL concentration of the extract, meanwhile Culex reticulata resulted in the lowest mortality rate (80%). However, a hundred percent (100%) mortality of the larvae, was observed at 8 mg/mL of all the types of extracts evaluated.Conclusion: The result indicates that the peels of these Citrus species, especially Culex latifolia, hold potential for control of Culex pipiens mosquito larvae.

The membrane transport of lemon grass palladium metallic nanoparticles and their synergistic action on plasma membrane integrity concerning endosmosis and fatality in Culex pipiens mosquito larvae

The membrane transport of lemon grass palladium metallic nanoparticles and their synergistic action on plasma membrane integrity concerning endosmosis and fatality in Culex pipiens mosquito larvae

Comparative toxicity of cinnamon oil, cinnamaldehyde and their nano-emulsions against Culex pipiens (L.) larvae with biochemical and docking studies

The larvicidal activity of cinnamon oil and its main component, cinnamaldehyde, was compared with their nano-emulsions (NEs) against Culex pipiens mosquito larvae. Oil-in-water (O/W) NEs preparation was based on the coarse emulsion followed by high-energy ultra-sonication. The droplet size, polydispersity index (PDI), viscosity, zeta potential, and pH of NEs were investigated. The droplet sizes of the NEs were 95.67 nm for cinnamon oil and 174.59 nm for cinnamaldehyde. The NEs recorded high negative zeta potentials (-30.0 and -21.20 for cinnamon oil and cinnamaldehyde, respectively). The larvicidal activity results showed that the cinnamaldehyde (LC50 = 94.46 and 72.91 mg/l for T and NE, respectively) had higher activities than cinnamon oil (LC50 = 154.08 and 123.13 mg/l for T and NE, respectively) after 24 h of exposure against C. pipiens larvae. These results proved that NE formulation enhanced the activity of tested compounds against larvae. The in vitro effect on the acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and gamma-aminobutyric acid transaminase (GABA-T) were demonstrated, and the data proved that the NEs formulations were higher than their pure compounds. Non-formulated cinnamon oil and cinnamaldehyde caused 17.26% and 30.83% of AChE, respectively, while their NEs caused 46.40% and 60.59% inhibition. Furthermore, the molecular docking studies indicated that the affinity binding of cinnamaldehyde on AChE and GABA-T was higher than ATPase. This work describes bio-products with potential use against C. pipiens larvae as eco-friendly products.

Characteristics of channel pores formed by Bacillus thuringiensis mosquito-larvicidal Cry4Aa toxin

Cry4Aa toxin produced by Bacillus thuringiensis subsp. israelensis exhibits specific toxicity to larvae of medically important mosquito genera. In the present study, we analyzed the characteristics of channel pores formed by recombinant Cry4Aa in a solvent-free planar lipid bilayer. Stable channel currents were observed in electrophysiologic measurements, and the single-channel conductance was 187 ± 10 pS in symmetrical buffer containing 150 mM KCl. The channel pores formed by Cry4Aa were cation-selective, with an estimated PK/PCl permeability ratio of 4.9. In addition, Cry4Aa channel pores exhibited apparent cation preference in the order Na+ > K+, Na+ > Ca2+, and K+ > Ca2+. Although the effect was limited, the cation preference of Cry4Aa channel pores seemed to be correlated with toxicity. Culex pipiens mosquito larvae reared in NaCl solution exhibited greater sensitivity to Cry4Aa, particularly early period after exposure. The presence of cations that preferentially translocate through Cry4Aa channel pores may facilitate excessive influx of water into the midgut cells, leading to colloid-osmotic lysis. Whereas CaCl2 had some effect on the mosquito-larvicidal activity of Cry4Aa, KCl had no effect. The effect of some cations may be mitigated by the variety of ion channels present on the midgut cell membrane.

Toxicological and biological effects of some plant extracts on the house mosquito Culex pipiens, the dominant species in Jeddah governorate

AbstractMosquitoes are a vector of dangerous diseases that kill millions of people annually. The traditional methods of control depend on the use of pesticides, which leads to the emergence of resistance against them over time, in addition to the pollution they leave in the environment and the targeting of beneficial organisms. Therefore, this study aimed to use extracts of natural products from Juniperus procera and Dodonaea viscosa plants in the control of mosquito larvae of Culex pipiens, as well as their applications in nanoparticle synthesis and effectiveness on mosquito larvae. These nanoparticles were determined and confirmed using multiple techniques, including UV–visible spectrometry, Fourier transform infrared spectroscopy and scanning electron microscopy. The IC50 values of the extracts plus silver nanoparticles were 20.871 and 105.166 ppm, a 5.03‐ and 2.17‐fold increase over the individual extracts, with IC50 values of 105.166 and 228.271 ppm, respectively. In addition, some morphological deformations were observed on the treated larvae through the stage of larval development into a pupa and the stage of emergence from a pupa into a complete insect.

The Insecticidal Activity of Entomopathogenic Bacteria Isolated from Musca domestica, Chrysomya albiceps and Lucilia sericata against the Mosquito Larvae of Culex pipiens

The present study evaluated the toxicity of different bacterial strains isolated from the outer surface of adult flies associated with carrions at Al – Mansoureya, Giza Governorate, Egypt against Culex pipiens larvae. 11 different bacterial strains were isolated and identified from the adults of Musca domestica, Chrysomya albiceps and Lucilia sericata. Only five strains caused mortality in C. pipiens larvae more than 50 %. The highest larval mortality was caused by the bacterial strains; Klebsiella oxytoca and Staphylococcus sciuri. The results indicated that entomopathogenic bacterial strains could have the potential for the biological control of mosquitoes.

Channel-pore cation selectivity is a major determinant of Bacillus thuringiensis Cry46Ab mosquitocidal activity.

Cry46Ab from Bacillus thuringiensis TK-E6 is a new mosquitocidal toxin with an aerolysin-type architecture, and it is expected to be used as a novel bioinsecticide. Cry46Ab acts as a functional pore-forming toxin, and characteristics of the resulting channel pores, including ion selectivity, have been analyzed. However, the relationship between channel-pore ion selectivity and insecticidal activity remains to be elucidated. To clarify the effects of charged amino acid residues on the ion permeability of channel-pores and the resulting insecticidal activity, in the present study, we constructed Cry46Ab mutants in which a charged amino acid residue within a putative transmembrane β-hairpin region was replaced with an oppositely charged residue. Bioassays using Culex pipiens mosquito larvae revealed that the mosquitocidal activity was altered by the mutation. A K155E Cry46Ab mutant exhibited toxicity apparently higher than that of wild-type Cry46Ab, but the E159K and E163K mutants exhibited decreased toxicity. Ions selectivity measurements demonstrated that the channel pores formed by both wild-type and mutant Cry46Abs were cation selective, and their cation preference was also similar. However, the degree of cation selectivity was apparently higher in channel pores formed by the K155E mutant, and reduced selectivity was observed with the E159K and E163K mutants. Our data suggest that channel-pore cation selectivity is a major determinant of Cry46Ab mosquitocidal activity and that cation selectivity can be controlled via mutagenesis targeting the transmembrane β-hairpin region. KEY POINTS: • Cry46Ab mutants were constructed by targeting the putative transmembrane β-hairpin region. • Charged residues within the β-hairpin control the flux of ions through channel pores. • Channel-pore cation selectivity is correlated with insecticidal activity.

Silver Nanoparticles affect biochemical parameters in tissues of mosquitos’ larvae

This work is concerned with studying the effect of Green synthesized Silver Nanoparticles (GSNPs) on the mosquito larvae of Culex pipiens. The lethal concentration Lc10, Lc50 and Lc90 were obtained from the established regression log concentrate-response lines after 24 hours of exposure. Results implied significant increasing mortality rate upon increasing the lethal concentrations of GSNPs which recorded 0.576 ppm, 1.719 ppm and 5.129 ppm for Lc10, LC50, and Lc90 respectively. For investigating the root cause of mortality, data indicated that there was a significant increase of lipid peroxidation level in tissue homogenates of larvae previously treated with the increasing of above mentioned lethal concentrations of GSNPs, which recorded 17.25 nmol/g.tissue, 18.0 nmol/g.tissue and 25.0 nmol/g.tissue for LC10, LC50, and LC90 respectively, compared to control sample which recorded 16.0 nmol/g. tissue. At the meantime, data also revealed a significant increase in levels of total protein, albumin and globulin levels in tissue homogenates of larvae previously treated with the increasing of above mentioned lethal concentrations of GSNPs , which recorded, 0.231 g/dl , 0.109 g/dl and 0.122 g/dl for Lc10, 0.735 g/dl, 0.115 g/dl and 0.62 g/dl for Lc50, 0.93 g/dl ,0.125 g/dl and 0.805 g/dl for Lc90 for total protein, albumin and globulin, respectively, compared to control samples which recorded 0.21 g/dl , 0.089 g/dl and 0.121 g/dl, respectively.

Selection of cypermethrin resistance in mosquito Culex pipiens larvae in Assiut, Egypt

To induce cypermethrinresistance in Culex pipiens larvae, about 20000 4th instar larvae of Cx. pipiens were collected from Assiut field and exposed to cypermethrin selection pressure for fifteen generations using dipping method. This study revealed that the resistance ratio (RR50) of the parent strain (G0) was 14.49-fold as compared with susceptible strain. This RR50 value increased gradually from each generation to the next one as a result of selection pressure with cypermethrin. The regression line for cypermethrin against the parent field strain showed slope value 2.38 which indicate a moderate level of heterogeneity of parent strain to cypermethrin. The first five generations during the course of cypermethrin selection showed that resistance ratio (RR50) was increased gradually from one generation to the next (The RR50 increased from 14.49-fold in G0 to 135.40-fold resistance in G5). By the 6th generation, the rate of resistance development to cypermethrin was fairly rapid where; the RR50 to cypermethrin increased from 135.40-fold in G6 to 272.00-fold resistance in G11. With the beginning of the 12th generation, the development of resistance to cypermethrin was increased very slowly during the last four generations from 279.92-fold in G12 to 295.52-fold resistance in G15 (plateau phase). Finally, the slope values were volatile until the eleventh generation (2.38 – 3.63) and then relatively proven in the last four generations (4.55 – 4.52). This is evidence of increasing homogeneity of selected strain in the last five generations.

Larvicidal and Inhibition Activities of Marine Algae Ulva lactuca Extracts on Culex pipiens Mosquito النشاط الإبادی الیرقی والتثبیطی لمستخلصات الطحلب البحری Ulva lactuca علی بعوضة Culex pipiens

This study aimed to investigate the larvicidal activity and inhibition effect of Sea lettuce Ulva lactuca extracts using various organic solvents (acetone, ethanol, and petroleum ether), against mosquito larvae of Culex pipiens (L.). The results revealed that all the extracts showed varied levels of larvicidal activity and inhibition effect against C. pipiens. Among them, the maximum efficacy was observed in the acetone extract which resulted in the strongest inhibition effect in the adult emergence (95%) and showed larvicidal activity (LC50=5.004 and LC90=9.76 mg/ml). Moreover, the three extracts of U. lactuca caused a reduction in the egg-laying capacity of mosquito females. Besides, the acetone extract caused the highest decrease (P < 0.05) on the mean number and hatchability of eggs produced by mosquito females. Thus, the present study suggested that using acetone, ethanol, and petroleum ether extracts of U. lactuca could be an effective method, somewhat easier, safe, and less expensive for controlling C. pipiens mosquito.

Mosquito larvae that survive a heat spike are less sensitive to subsequent exposure to the pesticide chlorpyrifos

While extreme high temperatures are an important aspect of global warming, their effects on organisms are relatively understudied, especially in ecotoxicology. Sequential exposure to heat spikes and pesticides is a realistic scenario as both are typically transient stressors and are expected to further increase in frequency under global warming. We tested the effects of exposure to a lethal heat spike and subsequently to an ecologically relevant lethal pulse exposure of the pesticide chlorpyrifos in the larvae of mosquito Culex pipiens. The heat spike caused direct and delayed mortality, and resulted in a higher heat tolerance and activity of acetylcholinesterase, and a lower fat content in the survivors. The chlorpyrifos exposure caused mortality, accelerated growth rate, and decreased the heat tolerance and the activity of acetylcholinesterase. The preceding heat spike did not change how chlorpyrifos reduced the heat tolerance. Notably, the preceding heat spike did lower the lethal effect of the pesticide, which makes an important novel finding at the interface of ecotoxicology and global change biology, and adds a new dimension to the “climate-induced toxicant sensitivity” (CITS) concept. This may be due to both survival selection and cross-tolerance, and therefore likely a widespread phenomenon. Our results emphasize the importance of including extreme high temperatures as an important transient global change stressor in ecotoxicology.

Chemical Composition and Larvicidal Activity of Mentha pulegium ssential Oil from Central Morocco Against Larvae of Mosquito Culex pipiens (Diptera: Culicidae)

Background: In Morocco, the species Culex pipiens (Diptera: Culicidae) has developed resistance to the synthetic insecticide. Therefore, there is an urgent need to find alternatives to the insecticides, as natural herbal biocides. Objective: The essential oil of Mentha pulegium grown the North center of in Morocco has been analyzed and their larvicidal activity on Culex pipiens was determined. Methods: The analysis and the identification of the various constituents of essential oilobtained by hydro-distillation of the aerial part were carried out by Gas Chromatography coupled with Mass Spectrometry (GC/MS). Biological tests were realized according to a methodology inspired from standard World Health Organization protocol. The larvicidal activity of medicinal plant extracts were tested against early fourth-instar larvae of Culex pipiens. The repellent efficacy was determined against of mosquito species (Culex pipiens) at six concentration’s (5, 10, 20, 40, 80 and 160 ppm) under the laboratory condition. The mortality was observed 24h after treatment; data were subjected to probit analysis to determine the Lethal Concentrations (LC50 and LC90) to kill 50 and 90 percent of the treated larvae of tested species. Results: The major constituents of Mentha pulegium essential oil were identified as pulegone (53.23%), α-pinene (12.1%), piperitone (9.62%), menthone (9.26) and piperitenone (6.6%). The LC50 and LC90 were estimated at 25.45 ppm and 98.66 ppm respectively. Conclusion: This investigation indicates that the Mentha pulegium essential oil could serve as a potential larvicidal and could be used as an ideal ecofriendly approach for the control of the Culex pipiens.

Bacillus thuringiensis Cry11Ba works synergistically with Cry4Aa but not with Cry11Aa for toxicity against mosquito Culex pipiens (Diptera: Culicidae) larvae

A 2,175-bp modified gene (cry11Ba-S1) encoding Cry11Ba from Bacillus thuringiensis subsp. jegathesan was designed and the recombinant protein was expressed as a fusion protein with glutathione S-transferase in Escherichia coli. The recombinant Cry11Ba was highly toxic against Culex pipiens mosquito larvae, being nine and 17 times more toxic than mosquitocidal Cry4Aa and Cry11Aa from Bacillus thuringiensis subsp. israelensis, respectively. Interestingly, a further increase in the toxicity of the recombinant Cry11Ba was achieved by mixing with Cry4Aa, but not with Cry11Aa. These findings suggested that Cry11Ba worked synergistically with Cry4Aa, but not with Cry11Aa, in exhibiting toxicity against C. pipiens larvae. On the other hand, the amount of Cry toxin bound to brush border membrane vesicles (BBMVs) did not significantly change between individual toxins and the toxin mixtures, suggesting that the increase in toxins binding to BBMVs was not a reason for the observed synergistic effect. It is generally accepted that synergism of toxins is a potentially powerful tool for enhancing insecticidal activity and managing Cry toxin resistance in mosquitoes. The mixture of Cry4Aa and Cry11Ba in order to increase toxicity would be very valuable in terms of mosquito control.