995 research outputs found

    Evaluation de l’effet repulsif d’extraits de neem (Azadirachta indica A. Juss., 1830) sur le charançon de la patate douce (Cylas puncticollis Boheman, 1833) en condition de laboratoire a Korhogo, nord de la Cote d’Ivoire

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    Une stratĂ©gie de gestion intĂ©grĂ©e des insectes nuisibles Ă  la culture de la patate douce a Ă©tĂ© Ă©laborĂ©e pour rĂ©duire les pertes dues Ă  ceux-ci. Ainsi, les propriĂ©tĂ©s rĂ©pulsives des extraits de feuilles et d’amandes de neem ont Ă©tĂ© Ă©valuĂ©es sur Cylas puncticollis, un charançon de la patate douce. Pour ce faire, quatre concentrations d’extraits ont Ă©tĂ© prĂ©parĂ©es Ă  raison de quatre rĂ©pĂ©titions par concentration. Le test a consistĂ© Ă  la dĂ©termination du pourcentage de charançons prĂ©sents dans la zone traitĂ©e. Chacune des concentrations d’extraits a Ă©tĂ© appliquĂ©e sur la moitiĂ© d’un papier buvard placĂ© dans une boite de PĂ©tri de 9 cm de diamĂštre et sur lequel 10 charançons ont Ă©tĂ© posĂ©s. Les effets rĂ©pulsifs des extraits ont Ă©tĂ© comparĂ©s Ă  ceux d’un insecticide chimique et l’eau distillĂ©e. Le test avec 20 cL/L d’extraits de feuilles a causĂ© 85 % de rĂ©pulsion contre 45 % pour les amandes Ă  25 g/L. Les extraits ont significativement causĂ© plus de rĂ©pulsion que l’eau distillĂ©e et l’insecticide chimique. Les tests ont rĂ©vĂ©lĂ© un potentiel plus rĂ©pulsif des extraits de feuilles comparĂ© Ă  celui des amandes. Les extraits de neem pourraient constituer une alternative crĂ©dible Ă  la lutte chimique pour la protection de la patate douce contre ce charançon. English title: Evaluation of the repellent effect of neem extracts (Azadirachta indica A. Juss., 1830) on the sweet potato weevil (Cylas puncticollis Boheman, 1833) under laboratory conditions in Korhogo, northern CĂŽte d’Ivoire Abstract An integrated pest management strategy for sweet potatoes has been developed to reduce pest losses. Thus, the repellent properties of neem leaf and kernel extracts were evaluated on Cylas puncticollis, a sweet potato weevil. For this purpose, four concentrations of extracts were prepared with four replicates per concentration. The test consisted of determining the percentage of weevils in the treated area. Each of the extract concentrations was applied to half of a blotting paper placed in 9 cm diameter Petri dishes on which 10 weevils were placed. The repellent effects of the extracts were compared to those of a chemical insecticide and distilled water. Test with 20 cL/L leaf extract caused 85% repellence compared to 45% for almonds at 25 g/L. Compared to the chemical insecticide and distilled water, the extracts caused significantly more repellence. The tests revealed a higher repellent potential of the leaf extracts compared to those of almonds. Neem extracts could be a credible alternative to chemical control for the protection of sweet potato against this weevil. Keywords: Neem extracts, Repellent effect, Sweet potato, Cylas puncticolli

    Contamination aux metaux lourds de la matrice eau-sediment et muscle du tilapia Oreochromis niloticus de trois fermes piscicoles en Cote d’Ivoire

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    La prĂ©sente Ă©tude a pour objectif de dĂ©terminer le niveau de contamination du mercure, du cadmium, de l’arsenic et du plomb dans l’eau, les sĂ©diments et le muscle du tilapia Oreochromis niloticus dans trois fermes piscicoles en CĂŽte d’Ivoire. L’eau, les sĂ©diments et les spĂ©cimens de poisson ont Ă©tĂ© prĂ©levĂ©s par mois de fĂ©vrier Ă  juillet 2017 en cage dans la lagune Aghien (ST1), en Ă©tang continental (ST2) Ă  Agboville et en cage dans le barrage de Taabo (ST3). Les paramĂštres physico-chimiques mesurĂ©s ont montrĂ© qu’à l’exception de la conductivitĂ©, des matiĂšres en suspension et des solides totaux dissous, aucune variation saisonniĂšre n’a Ă©tĂ© observĂ©e. En revanche, les valeurs moyennes des paramĂštres physico-chimiques calculĂ©es sont significativement diffĂ©rentes entre les fermes. Les valeurs de chaque mĂ©tal mesurĂ©es dans la matrice eau-sĂ©diment-muscle varient significativement entre les deux saisons dans toutes les fermes. Cependant, aucune diffĂ©rence entre les fermes Ă©chantillonnĂ©es n’a Ă©tĂ© observĂ©e. Les concentrations des mĂ©taux lourds mesurĂ©es dans le muscle sont infĂ©rieures aux valeurs seuils Ă©tablies par l’OMS Ă  l’exception de l’As. Cette contamination Ă©levĂ©e en arsenic pourrait porter atteinte Ă  l’intĂ©gritĂ© biologique et Ă  la santĂ© humaine.Mots clĂ©s : MĂ©taux lourds, Accumulation, Oreochromis niloticus, Ferme piscicole ivoirienn

    Extreme events prediction from nonlocal partial information in a spatiotemporally chaotic microcavity laser

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    The forecasting of high-dimensional, spatiotemporal nonlinear systems has made tremendous progress with the advent of model-free machine learning techniques. However, in real systems it is not always possible to have all the information needed; only partial information is available for learning and forecasting. This can be due to insufficient temporal or spatial samplings, to inaccessible variables or to noisy training data. Here, we show that it is nevertheless possible to forecast extreme events occurrence in incomplete experimental recordings from a spatiotemporally chaotic microcavity laser using reservoir computing. Selecting regions of maximum transfer entropy, we show that it is possible to get higher forecasting accuracy using nonlocal data vs local data thus allowing greater warning times, at least twice the time horizon predicted from the nonlinear local Lyapunov exponent

    Amelioration de la viscosite et de la densite energetique des bouillies infantiles preparees a partir de farines composees a base de riz, de niebe, de soja et d’arachide

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    L’aliment de complĂ©ment de la majoritĂ© des enfants maliens est la bouillie des cĂ©rĂ©ales dont la viscositĂ© est trĂšs Ă©levĂ©e pour les enfants ĂągĂ©s de 6 Ă  9 mois. Leur densitĂ© Ă©nergĂ©tique infĂ©rieure Ă  celle du lait maternelle (70 Kcal/100 ml) variait entre 35 Ă  45 kcal/100 ml (Bauer et al., 1997). Pour faciliter leur dĂ©glutition et amĂ©liorer la densitĂ© Ă©nergĂ©tique, la nĂ©cessitĂ© de les liquĂ©fier par l’utilisation de source d’amylase s’impose (TrĂšche 1995, RĂ©seau TPA, 1998). Les farines de complĂ©ment ont Ă©tĂ© dĂ©veloppĂ©es Ă  partir du riz NERICA 4 auquel l’arachide, le niĂ©bĂ©, le soja, le pain de singe ont Ă©tĂ© incorporĂ©s suivant la formule souhaitĂ©e. La farine de riz a Ă©tĂ© obtenue aprĂšs mouture du riz NERICA 4 blanchi. Les graines de soja et celles d’arachide ont Ă©tĂ© torrĂ©fiĂ©es sĂ©parĂ©ment, dĂ© pelliculĂ©es puis rĂ©duites en farine. Le niĂ©bĂ© a Ă©tĂ© dĂ©cortiquĂ©, lavĂ©, sĂ©chĂ© puis rĂ©duit en farine. Le maltage a consistĂ© respectivement Ă  tremper le riz pendant 12 heures et le mil pendant 07 heures dans l’eau tiĂšde. Les grains ont Ă©tĂ© Ă©gouttĂ©s sĂ©parĂ©ment et mis en germination dans un panier couvert pendant 3 jours au cours desquels, ils ont Ă©tĂ© arrosĂ©s matin et soir. La germination des grains est interrompue par le sĂ©chage. Les grains germĂ©s de riz et de mil ont Ă©tĂ© rĂ©duits sĂ©parĂ©ment en farine (malt). Dans chaque formule, 95 % de la farine composĂ©e ont Ă©tĂ© ajoutĂ©s Ă  5 % de malt de mil ou de riz. La viscositĂ© et la densitĂ© Ă©nergĂ©tique des bouillies infantiles ont Ă©tĂ© dĂ©terminĂ©es. La viscositĂ© de la bouillie contenant le malt de riz a Ă©tĂ© plus fluide (13 cm) que celle contenant le malt de mil (11 cm). Les densitĂ©s Ă©nergĂ©tiques des bouillies ont variĂ© de 52,19 Kcal Ă  117 Kcal/100 ml de bouillie. Les bouillies contenant le soja et le malt de riz ou de mil ont prĂ©sentĂ©s des densitĂ©s Ă©nergĂ©tiques similaires mais supĂ©rieures Ă  celles des autres bouillies. L’objectif de la recherche est de rĂ©duire la viscositĂ© des bouillies de complĂ©ment et d’amĂ©liorer leur densitĂ© Ă©nergĂ©tique en vue de lutter contre la malnutrition infantile.Mots clĂ© : Riz, bouillies de complĂ©ment, malt, viscositĂ©, densitĂ© Ă©nergĂ©tiqu

    Serological Evaluation of Onchocerciasis and Lymphatic Filariasis Elimination in the Bakoye and Falémé foci, Mali

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    In Mali, ivermectin-based onchocerciasis elimination from the Bakoye and FalĂ©mĂ© foci, reported in 2009–2012, was a beacon leading to policy shifting from morbidity control to elimination of transmission (EOT). These foci are also endemic for lymphatic filariasis (LF). In 2007–2016 mass ivermectin plus albendazole administration was implemented. We report Ov16 (onchocerciasis) and Wb123 (LF) seroprevalence after 24–25 years of treatment to evaluate if onchocerciasis EOT and LF elimination as a public health problem (EPHP) have been achieved

    Stacking tolerance to drought and resistance to a parasitic weed in tropical hybrid maize for enhancing resilience to stress combinations

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    Open Access JournalMaize is a food security crop cultivated in the African savannas that are vulnerable to the occurrence of drought stress and Striga hermonthica infestation. The co-occurrence of these stresses can severely damage crop growth and productivity of maize. Until recently, maize breeding in International Institute of Tropical Agriculture (IITA) has focused on the development of either drought tolerant or S. hermonthica resistant germplasm using independent screening protocols. The present study was therefore conducted to examine the extent to which maize hybrids simultaneously expressing resistance to S. hermonthica and tolerance to drought (DTSTR) could be developed through sequential selection of parental lines using the two screening protocols. Regional trials involving 77 DTSTR and 22 commercial benchmark hybrids (STR and non-DTSTR) were then conducted under Striga-infested and non-infested conditions, managed drought stress and fully irrigated conditions as well as in multiple rainfed environments for 5 years. The observed yield reductions of 61% under managed drought stress and 23% under Striga-infestation created desirable stress levels leading to the detection of significant differences in grain yield among hybrids at individual stress and non-stress conditions. On average, the DTSTR hybrids out-yielded the STR and non-DTSTR commercial hybrids by 13–19% under managed drought stress and fully irrigated conditions and by −4 to 70% under Striga-infested and non-infested conditions. Among the DTSTR hybrids included in the regional trials, 33 were high yielders with better adaptability across environments under all stressful and non-stressful testing conditions. Twenty-four of the 33 DTSTR hybrids also yielded well across diverse rainfed environments. The genetic correlations of grain yield under managed drought stress with yield under Striga-infestation and multiple rainfed environments were 0.51 and 0.57, respectively. Also, a genetic correlation between yields under Striga-infestation with that recorded in multiple rainfed environments was 0.58. These results suggest that the sequential selection scheme offers an opportunity to accumulate desirable stress-related traits in parents contributing to superior agronomic performance in hybrids across stressful and diverse rainfed field environments that are commonly encountered in the tropical savannas of Africa

    Rethinking water management in the Volta basin

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