Biopesticides from botanicals are nowadays strongly encouraged for use in the program of controlling insect vectors of diseases and other harmful insects. The present study had the objective of determining the chemical composition of the essential oil of Mentha x piperita L. (Lamiaceae). We also evaluated the larvicidal and ovicidal activities of EO against Culex pipiens L. according to the World Health Organization (WHO) protocol. The chemical composition of EO from the aerial parts of peppermint was analyzed by gas chromatography-mass spectrometry GC/MS. The main components were menthol (28.66 %), limonene (19.01 %), and p-cymene (15.82 %). Also, this research found that M. x piperita EO showed larvicidal activity against fourth-instar larvae. Mortalities were recorded after 24, 48, and 72 h of treatment. It has potent larvicidal activity with increasing concentration and exposure time (LC50 values were 448.74; 181.97 and 152.05 ppm). Besides, EO showed excellent ovicidal activity, the results of which indicated that the hatchability of eggs treated with LC50 and LC25 is 18.13 % and 53.67 %, respectively. Furthermore, the study examines the efficacy of this oil on the glutathione S-transferase (GST) and acetylcholinesterase (AChE) activity of Cx. pipiens larvae treated with LC50 and LC90. This experiment has led to neurotoxic activity and stimulation of the detoxification system, as shown by AChE inhibition and GST induction respectively. In conclusion, M. x piperita EO is a natural larvicide and promising ovicide against Cx. pipiens. Therefore, it is recommended for use as a natural biocide in the implementation of effective mosquito control programs.

Background: Plant extracts constitute an alternative to conventional insecticides. Culex pipiens is the most abundant mosquito species in Algeria . This research aimed to investigate the eficacy of essential oils from Mentha rotundifolia against the fourth instar larvae of Cx pipeins . Materials and Methods: The aerial parts of the plant were harvested in the Annaba region (Northeast of Algeria) between March and June 2017, the essential oils EOs) were extracted by a Clevenger hydrodistiller andanalyzed by gas chromatography-mass spectrometry (GC-MS). The larvicidal activities of EOs were tested against fourth instar larvae of Culex pipiens following the procedure of the World Health Organization under laboratory conditions. Furthermore, the effect of EO was examined on the activity of glutathione S-transferase (GST) and acetylcholinesterase (AChE), biomarkers of oxidative stress and neurotoxicity, respectively. Results: GC-MS analyses revealed sixteen compounds in M. rotundifolia EO and the main components are: Carvacrol (60.54%), Pulegone (5.95%) and M-cymene (5.25%). The larvicidal assay showed that the EO exhibited insecticidal activity against the fourth instar larvae of C. pipiens (LC 50 = 62.08 ppm and LC 90 = 178.64 ppm at 72 hour exposure).When applied at it’s LC 50 and LC 90 EOwas found to present a neurotoxic activity and a stimulation of the detoxification system, as evidenced by an inhibition of AChE and an induction of GST, respectively. Conclusion: M . rotundifolia EO presents an efficacy against Cx pipiens larvae and could be considered as a potential alternative to conventional insecticides for mosquito control.

Introduction : The mosquito Culex pipiens L is a common and abundant species in the world. This species serve as bridge vectors of the West Nile virus from birds to humans. Objective: Under the laboratory conditions, toxicological evaluation of two compounds Azadirachtin and Bacillus thuringiensis israelensis ( B.t.i ) against eggs of mosquito Cx. pipiens and biological effect of these compounds on larvae, pupae and adult emergence Methods : The ovicidal activity was determined after 24 h of exposure to concentrations of Azadirachtin and B.t.i . Results: indicated high reduction in percentage of egg hatch resulted from treated eggs by azadirachtin, estimated by 31.41% at 1mg /L and 91.51% at 0.125 mg /L, the obtained results show a high mortality with the increase in the concentration, and prolongation in larval and pupal developments resulted from treated eggs by azadirachtin, estimated by 4.55 days at 0.125mg/L and 7.66 days at 1 mg/L in first instar , larval and pupal duration increased with the increase in the concentration of azadirachtin. The results indicated high augmentation in the percentages of the malformations with the decrease in the concentration of azadirachtin. In contrast, in adult stage, the results indicated high reduction in total eggs laid, percentage of hatchability and longevity. No effect was observed after treated eggs by B.t.i. Conclusion: From the results, it can be concluded the Azadirachtin are excellent potential for controlling the mosquito Culex pipiens .

The secondary effects emerging from the use of conventional pesticides on environmental and human health were lead scientists to look for other safety products. Natural pesticides are promising in pest control, especially those derived from plants. In this study, the larvicidal activity and their effect on the reproduction potency of the essential oils of Ruta chalepensis and Eucalyptus camaldulensis were evaluated against the mosquito species Culex pipiens. Newly exuviated larvae of third and fourth instar larvae were exposed to various concentrations of Ruta chalepensis (150-700 ppm) and Eucalyptus camaldulensis (100-600 ppm). The results, for both plants, showed a toxic effect of the treated larval series with dose-response relationship. For Ruta chalepensis oil bioassay the lethal concentrations (LC50 and LC90) were estimated at 95ppm and 550 ppm for the third-instar larvae, respectively, while these respective values were 245ppm and 830ppm for the fourth-instar larvae of Culex pipiens. For Eucalyptus camaldulensis oil the LC50 and LC90 values of were 185 and 580ppm for the third-instar larvae, and 280 and 1050 ppm for the fourth-instar larvae respectively. In other experiments the compound was applied at LC50 and LC90 against the fourth instars larvae and its effects was investigated on fecundity of female emerged from larval treated series with lethal concentrations. The results showed that the two oils reduced significantly the laying egg number and the percentage of fecundity.

Aims: Insect growth regulators (IGRs) offer alternatives to conventional chemical larvicides that pose problem of resistance and environmental safety. However, only a limited number of IGRs have been approved for use in mosquito control. The present investigation was to evaluate the insecticidal activity of a non -steroidal ecdysteroid agonist, methoxyfenozide (RH-2485), against last -instar larvae ofCuliseta morsitans (Culicidae: Diptera) under the laboratory conditions, and its effect on fecundity and fertility of females. Methodology: Based on preliminarybioassays, five concentrati ons ranging from 0.012 to 0.072mg/L were tested. The larvicidal test was made according to the World Health Organization(WHO) protocol standard by exposing newly ecdysed fourth -instar larvae for 24h. CL50value of methoxyfenozide value was determined by probit analysis. Results: The insecticidal activity of methoxyfenozide result in a dose - dependent reduction in adult emergence. In addition, larval mortality was relatively importan t compared with the mortality recorded for the other following developmental stages. The larval mortality varies betw een 16.84±3.89 % and 66.24±3.50 % for 0.012 mg/L and 0.072 OriginalResearch Article

13T P Abstract Azadirachtin was tested for its effects against First P P and second instars larvae of mosquito Culex pipiens pipiens (Diptera: Culicidae), laboratory reared larvae were exposed to 0.125 ; 0.250; 0.500 and 0.750 mg/ L of azadirachtin in laboratory of biology animal application, biology Department , university of Badji Mokhtar, Annaba, Algeria. Larvicidal assays were conducted according to standard World Health Organization (WHO) .The results have been exploited according to classic statistical methods. A linear correlation was revealed between concentration and larval mortality. At first stage, larval mortality increased from 45.83 % at 0.125 mg /L to 94.44 % at concentration 0.750mg /L of Azadirachtin in direct effect. The lethal concentration LC R

The molting hormone (ecdysteroids) in whole body extracts of 4th-instar larvae ofCulex pipiens L. (Diptera, Culicidae) was measured by an enzyme-immunoassay (EIA) using two specific antibodies, the rat monoclonal EC 19 antibody showing a high affinity for 20-hydroxyecdysone (20E) and the rabbit polyclonal B antibody six times more sensitive to ecdysone (E) than to 20E. EIA measurements revealed the presence of the two main hormones seen in C. pipiens: E (ca. 30 %) and 20E (ca. 70 %). Furthermore, change in ecdysteroid amounts during the 4th-larval stage was down using only a rat monoclonal because 20E was the major hormone. The ecdysteroid amounts presented a single peak that occurred at day three during the last larval development. In a second series of experiment, the cuticle cycle was determined by a histological study of the larval integument in order to establish temporal correlations with the hormonal levels. Thus, the ecdysteroid peak recorded during the last larval stage coincides with the apolysis and could be related with the induction of a new cuticle secretion. Key words: Mosquitoes, Culex pipiens, hormone, ecdysteroids, enzyme-immunoassay (EIA), histology, cuticle.

An insecticide containing azadirachtin, a tree ﺮﻴﺛﺄﺗ ﺔﺳارد ﺚﺤﺒﻟا اﺬه لوﺎﻨﺗ (Azadirachta indica) extract, was tested against Culex pipiens mosquito larvae and pupae in east of the Republic of Algeria under laboratory conditions. First, after treatment of larval stage, LC50 and LC90 values for Azadirachtin were 0.35 and 1.28 mg/L in direct effect and 0.3-0.99 mg/l in indirect effect, respectively. Second, after treatment of the pupal stage, the LC50 and LC90 in direct effect were measured as0.42 -1.24mg/l and in indirect effect was 0.39mg/l-1.14mg/l respectively. Mosquito adult fecundity were markedly decreased and sterility was increased by the Azadirachtin after treatment of the fourth instar and pupal stage. The tretment also prolonged the duration of the larval stage. The results show that the Azadirachtin is promising as a larvicidal agent against Culex pipiens, naturally ocurring biopesticide could be an alternative for chemical pesticides.

Andalin, a benzoylphenylurea (BPU) derivative, was evaluated on Culex pipiens L. (Diptera: Culicidae). Treatment was made on newly 3rd- and 4th instar larvae for 24 h. The compound exhibited insecticidal activity and mortality occured after earlier inhibition of their development or by their inability to complete their ecdysis. Treatment resulted in a significant larvicidal effect and in a inhibition of adult emergence. Moreover, the compound disturbed growth and development since several morphological types and an increase in the duration of larval stage were observed. Histological study conducted on 4th instar larval integument, showed that Andalin caused a significant reduction in the thickness of cuticles secreted compared to controls. Thus, Andalin prevent molting in C. pipiens by interfering with cuticle deposition confirming the primary mode of action of this BPU insecticide.