Treatment and comparative analysis of the properties of aqueous extracts of seed kernel of Azadirachta indica A. Juss (neem) was carried out on Aedes aegypti larvae. The aim of this work was to evaluate lethal effects of neem products (1% Suneem, formulated neem oil and neem powder) on A. aegypti larvae. Assays showed that A. indica was toxic to larvae of A. aegypti. For 1% Suneem, 1% formulated neem oil and neem powder, the lethal concentrations and lethal time at 50% (LC 50 and LT 50 ) for A. aegypti were 2 and 8 mg/l after 24 h and 3 mg/l after 120 h, respectively. Assays showed that Suneem and Formulated neem oil were more toxic to A. aegypti than Neem powder. Both products of the neem (A. indica, A. juss) have a remarkable influence on the development of A. aegypti larvae, causing an inhibition of nymphs and adults emergency. The Histopathological results revealed a serious damage on the epithelial columnar cells, a perturbation of alimentary flow, slightly hypertrophied cells, a beginning of vacuolisation on apical level, and a bursting of some cells in posterior part of the gut. However, nuclei, adipose tissue and muscles seem to keep normal appearance.

RésuméDes produits de neem (Azadirachta indica) (huile de neem formulée 1 % et poudre de neem 0,3 %) fabriqués par une industrie sénégalaise (SENCHIM), ont été appliqués sur des larves et nymphes du moustique (Culex quinquefasciatus). Les doses ont été de 0,02 à 0,038 % (v/v) et de 0,2 à 2 % (p/v) respectivement pour l'huile de neem formulée et la poudre de neem. Les résultats dans les conditions du laboratoire ont montré que la poudre de neem était plus toxique au stade larvaire (mortalités entre 86,1 et 100 %) qu'au stade nymphal (entre 14,5 et 95,9 % d'adultes envolés). Cependant, l'huile de neem formulée a été efficace aussi bien au stade larvaire (mortalité entre 52,1 et 80 %) qu'au stade nymphal (entre 0 et 14 % d'adultes envolés). L'étude histopathologique a montré que les produits agissent au niveau du système digestif des larves après ingestion alors qu'au niveau des nymphes seul l'effet contact est observé. L'huile de neem formulée 1 % apparaît plus efficace que la poudre de neem 0,3 % pour le contrôle des moustiques en milieu aquatique.Mots-clés : neem, Azadirachta indica, stade préimaginal, Culex quinquefasciatus. AbstractComparative study of two neem products (oil and powder) on preimaginal stages of Culex quinquefasciatus mosquito (Diptera: Culicidae) Neem (Azadirachta indica) products (neem oil formulated 1 % and neem powder 0.3 %), manufactured by a Senegalese industry (SENCHIM), were applied to mosquito (Culex quinquefasciatus) larvae and nymphs. The doses products were from 0.02 to 0.038 % Fawrou Seye et al. 212Afrique SCIENCE 02(2) (2006) 212 -225 (neem oil) and 0.2 to 2 % (powder). In laboratory conditions, results showed that neem powder was more toxic at larval stage (mortalities between 86.1 and 100 %) than nymphal stage (between 14.5 and 95.9 % adults flow away). Neem oil formulated was effective as well as larval stage (mortality between 52.1 and 80 %) than nymphal stage (between 0 and 14 % adults flown away). The histopathological study reveals that neem products act upon larval digestive system after ingestion, whereas for nymphs only contact effects are showed. Neem oil formulated 1 % appears more effective than neem powder 0.3 % for mosquitoes control in aquatic environment.

Mosquitoes in general and Culex quinquefasciatus in particular have for a long time constituted a source of nuisance due to the diseases they transmit, stings and annoying buzzing. They are also a public health problem. This is why this study is aimed at finding a biopesticide that can fight effectively but also be an alternative to chemical residual pesticides in the environment. Concentrations of biopesticides used are ranged from 2.5 10 8 to 12.5 10 8 spores/ml with intervals of 2.5 10 8 spores/ml for Metarhizium anisopliae. Concentrations ranging beetween 8 10-4 g/ml to 40 10-4 g/ml with intervals of 8 10-4 g/ml of Azadirachta indica (Suneem 1%) were used to fight against 100 three instars larvae of Culex quinquefasciatus. Concentrations of the mixture of Azadirachta indica (Sunnem 1%) and Metharhium anisopliae ranging from 0.02 ml +2 10 8 spores/ml to 0.02 ml + 1 10 8 spores/ml were used to study synergic effects of these two biopesticides. One hundred (100) of three instars larvae of Culex quinquefasciatus are used as control and placed in the same jars with 500 ml of distilled water. Metarhizium anisopliae (green muscle) have caused 50% mortality of three instars larvae of Culex quinquefasciatus after 3 days. Azadirachia indica (Suneem 1%) have gaved a mortality more than 60% after 2 days. The mixture Azadirachta indica (Suneem1%) and Metarhizuim anisopliae caused a high mortality with a rate that exceeds 90% in 3 days. The mixture also prevented a larval moult thus stopping their growth and development. In summary, both Metharizium anisopliae and Azadirachta indica (Suneem 1%) are effective against three instars larvae of Culex quinquefasciatus. Their mixture caused a synergic effect and thus increased their individual efficacy of two biopesticides.

Morphometric data is a useful complement of information that allows precise identification of the different parts of Rastrococcus invadens in Senegal. This study was carried out in four farms (Diatock and Oussouye) all located in natural Casamance and (Santhie and Khay) in the region of Thies. The work took place in February 2016 where citrus production is important. In each farm, we chose the lemon tree and the orange tree which are host plants of R. invadens.From each plant we collected 10 specimens. This enabled us to get 40 specimens from Casamance and 40 other specimens from Thies. Specimens were coded with regard to both the area and the type of plant they were collected from. The average measurements of the different parts of the insect showed a difference between the populations of the two agro-ecological zones with homogeneity of the populations of Thies and a heterogeneity of the populations of Casamance with a large zone of introgression. The results of this study should allow easier recognition of the different parts of R. invadens.

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Rastrococcus invadens (Homoptera, Pseudococcidae) or mealybug is an insect pest of mango and several other fruit trees including citrus. The cochineal is native to Southeast Asia and was first identified in Senegal in Dakar in 1995. Since then, it has been widely distributed throughout the country and more particularly in the two most fruit-producing areas: Casamance and Thies. To properly conduct our study, we chose the four most infested mango varieties namely Kent, Keitt, Sewe and Boukodiekhal. All these populations are from the locality of Pout (Thies region). On each plant we collected 10 people. This allowed us to have a total of 40 individuals. The individuals harvested are coded according to the zone and the type of plant in which they were harvested. This study revealed almost two more or less distinct morphometric groups made up on the one hand by populations from improved varieties (Kent and Keitt) and on the other by those from local varieties (Sewe and Boukodiekhal).

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Pest insects are a major constraint on fruit production in Senegal. In order to find an alternative to the chemical control of these pests, the insecticidal effect of neem derivatives (Azadirachta indica) formulated at different doses on the mango mealybug (Rastrococcus invadens) was studied. The powders obtained from the different parts of the neem were mixed with distilled water in different proportions, namely for 100ml 0g (control), 1g, 2g, 4g, 8g, 16g, 32g, 64g and 124g. The whole, consisting of water and powders of the different parts of neem, was homogenized. For each treatment, 5 repetitions were made over 5 days. The results obtained show that neem significantly reduced the populations of mealybug on the mango tree. The results also showed that neem is a very effective insecticide against these pests. This effectiveness is all the more important with almond derivatives (100% mortality at a dose of 32g per 100ml) compared to other neem derivatives.