Components of coconut fruit susceptibility to Phytophthora katsurae (Pythiaceae) in Côte d’Ivoire

The present study was to evaluate the susceptibility of coconut fruit to Phytophthora katsurae (Ko and Chang) according to their age and the position of lesions. The infection rates of nuts under natural conditions and by inoculation techniques on wounds and deposition of inoculum on the pericarp were compared. Under natural conditions, immature adult nuts between 8 and 11 months old are the most susceptible stage to infection by P. katsurae. The rounder part is the most receptive site. The proximal part is most liable to attack in young 4-8 months old fruits, which are less numerous in the susceptible host stage. Ripe nuts of at least 12 months old are totally immune to infection. The distal part of all categories of nuts is not invaded by the lesions. There is a highly significant difference between the susceptibility of the proximal zone of young and adult wounded nuts at 1% significance level. A non responsiveness of the distal zone of the young nuts was observed on nuts not wounded. Based on artificial inoculations on fruit of different ages, the resistance mechanism in the fruit seems to be much more physically linked to nut anatomy than chemically.Keywords: Immature nutfall, field infection, rough and gentle inoculation, success rate, physical penetratio

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

La présente étude a pour objectif de déterminer le niveau de contamination du mercure, du cadmium, de l’arsenic et du plomb dans l’eau, les sédiments et le muscle du tilapia Oreochromis niloticus dans trois fermes piscicoles en Côte d’Ivoire. L’eau, les sédiments et les spécimens de poisson ont été prélevés par mois de février à juillet 2017 en cage dans la lagune Aghien (ST1), en étang continental (ST2) à Agboville et en cage dans le barrage de Taabo (ST3). Les paramètres physico-chimiques mesurés ont montré qu’à l’exception de la conductivité, des matières en suspension et des solides totaux dissous, aucune variation saisonnière n’a été observée. En revanche, les valeurs moyennes des paramètres physico-chimiques calculées sont significativement différentes entre les fermes. Les valeurs de chaque métal mesurées dans la matrice eau-sédiment-muscle varient significativement entre les deux saisons dans toutes les fermes. Cependant, aucune différence entre les fermes échantillonnées n’a été observée. Les concentrations des métaux lourds mesurées dans le muscle sont inférieures aux valeurs seuils établies par l’OMS à l’exception de l’As. Cette contamination élevée en arsenic pourrait porter atteinte à l’intégrité biologique et à la santé humaine.Mots clés : Métaux lourds, Accumulation, Oreochromis niloticus, Ferme piscicole ivoirienn

Review on Newcastle disease in poultry

Newcastle disease is an infectious disease of poultry caused by an avian Paramyxovirus type I that affects more than two hundred avian species. It is an enzootic disease in parts of Asia, Africa, the Middle East and some countries in South America. Isolated outbreaks of Newcastle disease occur sporadically in some European countries and Central America. This review synthesizes available information on the virus and the disease it causes. The disease is transmitted by direct contact with infected animals or by indirect contact through inanimate carriers. The incubation period of the disease varied from 2 to 15 days. Five pathotypes were distinguished according to the incidence and severity of the clinical signs. Velogenic strains, which are the most virulent, can cause 100% mortality in unprotected herds. Control measures are based on mass vaccination of susceptible animals and the application of biosecurity measures in poultry farms. Regulations are also put in place to prevent the introduction of the virus into countries free of the disease.Keywords: Poultry, paramyxovirus, Newcastle disease, panzootie, mortality. &nbsp

Relative performance of indoor vector control interventions in the Ifakara and the West African experimental huts.

BACKGROUND: West African and Ifakara experimental huts are used to evaluate indoor mosquito control interventions, including spatial repellents and insecticides. The two hut types differ in size and design, so a side-by-side comparison was performed to investigate the performance of indoor interventions in the two hut designs using standard entomological outcomes: relative indoor mosquito density (deterrence), exophily (induced exit), blood-feeding and mortality of mosquitoes. METHODS: Metofluthrin mosquito coils (0.00625% and 0.0097%) and Olyset® Net vs control nets (untreated, deliberately holed net) were evaluated against pyrethroid-resistant Culex quinquefasciatus in Benin. Four experimental huts were used: two West African hut designs and two Ifakara hut designs. Treatments were rotated among the huts every four nights until each treatment was tested in each hut 52 times. Volunteers rotated between huts nightly. RESULTS: The Ifakara huts caught a median of 37 Culex quinquefasciatus/ night, while the West African huts captured a median of 8/ night (rate ratio 3.37, 95% CI: 2.30-4.94, P  4-fold higher mosquito exit relative to the West African huts (odds ratio 4.18, 95% CI: 3.18-5.51, P < 0.0001), regardless of treatment. While blood-feeding rates were significantly higher in the West African huts, mortality appeared significantly lower for all treatments. CONCLUSIONS: The Ifakara hut captured more Cx. quinquefasciatus that could more easily exit into windows and eave traps after failing to blood-feed, compared to the West African hut. The higher mortality rates recorded in the Ifakara huts could be attributable to the greater proportions of Culex mosquitoes exiting and probably dying from starvation, relative to the situation in the West African huts

Analysis of frequency and intensity of European winter storm events from a multi-model perspective, at synoptic and regional scales

This study focuses on the analysis of winter (October-November-December-January-February-March; ONDJFM) storm events and their changes due to increased anthropogenic greenhouse gas concentrations over Europe. In order to assess uncertainties that are due to model formulation, 4 regional climate models (RCMs) with 5 high resolution experiments, and 4 global general circulation models (GCMs) are considered. Firstly, cyclone systems as synoptic scale processes in winter are investigated, as they are a principal cause of the occurrence of extreme, damage-causing wind speeds. This is achieved by use of an objective cyclone identification and tracking algorithm applied to GCMs. Secondly, changes in extreme near-surface wind speeds are analysed. Based on percentile thresholds, the studied extreme wind speed indices allow a consistent analysis over Europe that takes systematic deviations of the models into account. Relative changes in both intensity and frequency of extreme winds and their related uncertainties are assessed and related to changing patterns of extreme cyclones. A common feature of all investigated GCMs is a reduced track density over central Europe under climate change conditions, if all systems are considered. If only extreme (i.e. the strongest 5%) cyclones are taken into account, an increasing cyclone activity for western parts of central Europe is apparent; however, the climate change signal reveals a reduced spatial coherency when compared to all systems, which exposes partially contrary results. With respect to extreme wind speeds, significant positive changes in intensity and frequency are obtained over at least 3 and 20% of the European domain under study (35–72°N and 15°W–43°E), respectively. Location and extension of the affected areas (up to 60 and 50% of the domain for intensity and frequency, respectively), as well as levels of changes (up to +15 and +200% for intensity and frequency, respectively) are shown to be highly dependent on the driving GCM, whereas differences between RCMs when driven by the same GCM are relatively small

Application d’un modèle conceptuel et d’un modèle de réseaux de neurones artificiels à la simulation des débits annuels dans le bassin versant du N’zi-Bandama (Côte d’Ivoire)

Cette étude présente la comparaison de deux approches de modélisation de la transformation pluie-débit à l'échelle annuelle : un modèle conceptuel et un réseau de neurones artificiels (RNA). Les deux modèles sont appliqués sur trois sous-bassins du fleuve N’zi-Bandama en Côte d'Ivoire. L’analyse comparative est basée sur les performances de simulation en termes de critère de Nash-Sutcliffe. Les modèles ont été testés sur deux périodes, l’une sèche (1973-1997) et l’autre humide (1961-1972). Les données d’entrée des deux modèles sont la pluie et l’évapotranspiration potentielle au pas de temps annuel. Les principaux résultats de ce travail montrent que les performances des deux modèles (conceptuel et neuronal) restent en général satisfaisantes avec des critères de Nash-Sutcliffe supérieurs à 60%. Ces modèles se sont révélés aussi robustes et adaptés pour la simulation des débits annuels des rivières. La comparaison des deux modèles a montré que le réseau de neurones a obtenu des résultats significativement meilleurs que le modèleconceptuel.Mots-clés : modélisation pluie-débit, modèle conceptuel, réseaux de neurones artificiels, N’zi-Bandama, Côte d’Ivoir.Application of a conceptual model and a model of artificial neural networks for the simulation of annual flows in the N'Zi-Bandama watershed (Ivory Coast).This study presents the comparison of two approaches of modelisation of the rainfall-runoff transformation on an annual scale: a conceptual model and an artificial neural network. The two models are applied to three watersheds of the N’zi-Bandama river in Ivory Coast. The comparative analysis is based on the performances of simulation in terms of criterion of Nash-Sutcliffe. The models were tested over two periods, one dries (1973-1997) and the other wet one (1961-1972). The data input of the two models are the rain and the potential evapotranspiration with the step of annual time. The principal results of this work show that the performances of the two models (conceptual and neuronal) remain satisfactory in general with criteria of Nash-Sutcliffe higher than 60%. These models appeared also robust and adapted for the simulation of the annual flow of the rivers. The comparison of the two models showed that the network of neurons had results significantly better than the conceptual model.Keywords : rainfall-runoff modelling, conceptual model, artificial neural network, N’zi-Bandama, Ivory Coast

Analyses, calibration and validation of evapotranspirationmodels to predict grass-reference evapotranspiration in theSenegal river delta

Study region: Grass-reference evapotranspiration estimation by the Penman-Monteithmethod (PM-ETo) requires a number of climate variables which are not always availableat all weather stations. Different alternative ETo equations have been developed and theirutilization for various local climate conditions requires analyses of their accuracy as com-pared to the standardized Penman-Monteith method. There is a significant lack of data andinformation on this topic in the Senegal River Delta (SRD). Study focus: The objective of this study was to evaluate, calibrate and validate six EToequations ((Trabert, Mahringer, Penman1948, Albrecht, Valiantzas1 and Valiantzas2) forthe SRD. Although all six equations showed good agreement with the PM-ETo (R2\u3e 0.60)for daily ETo estimates, the Valiantzas2 equation was the best model for the Senegal RiverDelta and had the lowest root mean squared difference (RMSE) of 0.45 mm/day and thelowest percent error of estimate (PE) about 7.1%. New hydrological insights for the region: In the case of data limitations, the equationscalibrated in this study are recommended for ETo estimation in the Senegal River Delta. Theresults of this study could be used by agricultural producers, crop consultants, universityresearchers, policy makers for the agricultural, hydrological, and environmental studies aswell as proper allocation and use and forecasting in the SRD where lowland irrigated riceis predominant

Effets de scenarios de changements climatiques sur la cacaoculture en Cote d’Ivoire

L’influence des scenarios de changements climatiques a été analysée pour les régions Centre et Sud de production cacaoyère en Côte d’Ivoire. A partir des modèles RCP 4.5 et 8.5 de concentration des Gaz à Effets de Serre (GES), les paramètres température et pluviométrie ont été projetés sur les horizons 2021-2050 et 2041-2070 en comparaison à la période de référence 1980-2010. Les résultats ont montré qu’en dehors du nombre élevé de jours chauds qui pourrait provoquer la disparition de la cacaoculture dans les zones marginales de la région Centre, les indices climatiques se situent dans des conditions normales de production du cacaoyer dans les deux régions. Les risques liés aux maladies et ravageurs pourraient être similaires ou potentiellement réduits. En région Sud, les variations climatiques n’auraient aucun impact sur la cacaoculture. Comme stratégies de résilience, les programmes de sélection variétale devront mettre à la disposition des producteurs un matériel végétal tolérant à la sécheresse et aux maladies accompagnée de formations sur les bonnes pratiques agricoles dont l’agroforesterie. Toutefois, l’accès des producteurs à l’information météorologique devra être renforcé.&nbsp; English title: Climate change effects in cocoa cultivation Abstract The influence of climate change scenarios was analyzed for the Center and South regions of cocoa farming in Côte d’Ivoire. From greenhouse gas (GHG) concentration models RCP 4.5 and 8.5, the parameters of temperature and rainfall were projected over the time in years 2021-2050 and 2041- 2070 compared to year 1980-2010 as reference period. The results showed that apart from the high number of hot days which could cause the disappearance of cocoa farming in marginal areas of the Center region, the climatic indices are normal within cocoa production conditions in both regions. Risks on cocoa pests and disease could be similar or potentially reduced. In the South region, climatic variations would have no impact on cocoa farming. As resilience adaptation strategies, tolerant germplasm to drought and pest and disease should be provided to farmers by cocoa research program with training package on good agricultural practices (GAP) including agroforestry. Therefore, theaccess to meteorological information has to be strengthened for smallholders cocoa farmers. Key words: Climate change scenarios, impact, cocoa farming, Côte d’Ivoire