Etude comparative des performances des plateformes de compostage de Siteu et de Ngui à Dschang (Cameroun)

A Dschang, le compostage artisanal est le mode de traitement de la fraction fermentescible majoritaire dans les déchets locaux. Qualifié d’activité à haute intensité de main d’œuvre (HIMO), il permet de créer trois emplois directs par tonne/jour de déchets traités. Les deux plateformes fonctionnelles de nos jours à Dschang occupent une quarantaine de personnes et permettent de traiter en moyenne 3 000 tonnes de déchets chaque année. Afin d’entrevoir leur autonomie, les équipes ont été évaluées par la méthode du bilan main d’œuvre. Cette méthode est pratique et permet d’exprimer la productivité des agents afin d’évaluer le coût de production et d’identifier les leviers d’optimisation. En ce sens, l’augmentation des quantités de déchets traités par agent afin de diminuer le coût de production et l’amélioration de la qualité de compost produit afin de faciliter son utilisation ont été identifiées comme les leviers internes. Cependant, s’il est aisément admis que la qualité obtenue est surtout conditionnée par la nature des déchets initiaux ; la quantité obtenue l’est tout aussi. En effet, l’étape de tri ainsi que l’étape d’affinage (criblage), nécessaires pour l’obtention d’un compost de qualité, représentent aussi les étapes les plus chronophages et qui déterminent objectivement leur productivité. A Dschang, ces deux étapes représentent en moyenne 84% (66% pour le tri et 18% pour le criblage) du temps de travail. Les performances de compostage mesurées diffèrent de 22% en faveur de Ngui où la productivité se situe à 10,41 ttraitées/homme.mois tandis qu’elle se situe à 8,53 ttraitées/homme.mois à Siteu. Les facteurs majeurs justifiant ces variations sont la qualité des déchets entrants (à 46,2%) et l’aménagement des sites (à 34,3%). Aussi, quelques retours négatifs, liés à la présence d’indésirables, ont été enregistrés auprès des utilisateurs du compost produit à Siteu. Donc, du fait de la meilleure qualité des déchets entrants et de la concentration des activités sur un espace limité à Ngui par rapport à Siteu, la consolidation des emplois créés et la pérennisation de l’activité de compostage seraient assurées sur le site de Ngui car il a été établi que ces dernières passeraient, entre autres, par l’atteinte d’une productivité minimale de 10 ttraitées/homme.mois. Ceci renforce l’argument de développer le compostage de proximité (au plus près de la production des déchets) et questionne sur la construction de grands sites.   Artisanal composting is the method of treating the waste’s fermentable fraction in Dschang. Qualified as a high intensity workforce, it provides three direct jobs per ton of daily treated waste. Around 40 people work in the two nowadays operational platforms and treat an average of 3,000 ton of waste each year. To foresee their autonomy, the guarantee of the sustainability of activities and consolidation of these jobs, the teams were assessed using the workforce assessment method. It’s a practical method for expressing the productivity of workers to express the cost of production and identify optimization levers. In this vein, the increase in the quantities of waste treated per agent in order to reduce the production cost and the improvement of the quality of the compost produced in order to facilitate its use have been identified as the internal levers. However, if it is readily accepted that the quality of compost is mainly conditioned by the nature of the initial waste; so is the quantity of compost obtained. In fact, the sorting stage as well as the screening stage, necessary to obtain good quality compost, also represent the most time-consuming stages and which objectively determine the worker’s productivity. In Dschang, these two stages represent 84% (66% for sorting and 18% for screening). Ngui’s team with a monthly productivity of 10.41 ton of waste treated/person performs 22% more than Siteu’s team with a monthly productivity of 8.53 ton of waste treated/person. The major factors justifying these variations are the quality of incoming waste (at 46.2%) and site development (at 34.3%). Some negative feedback due to the presence of unwanted items were also recorded among users of the compost produced in Siteu. Therefore, due to the better quality of incoming waste and the concentration of activities on a limited space on the Ngui platform compared to that of Siteu, the consolidation of the jobs created and the sustainability of the composting activity would be ensured at Ngui. It was established that continuation of activities would require, among other things, the achievement of a minimum monthly productivity of 10 ton of waste treated/person. This strengthens the argument for developing local composting (as close as possible to waste production) and raises questions about the construction of large sites.vvv

Linking spatial distribution of Rhipicephalus appendiculatus to climatic variables important for the successful biocontrol by Metarhizium anisopliae in Eastern Africa

Cattle production is constantly threatened by diseases like East Coast fever, also known as theileriosis, caused by the protozoan parasite Theileria parva which is transmitted by ticks such as the brown ear tick, Rhipicephalus appendiculatus. To reduce the extensive use of chemical acaricides, fungal-based microbial control agents such as Metarhizium anisopliae have been tested and show promising results against R. appendiculatus both in field and in semi-field experiments in Africa. However, no known endeavors to link the spatial distribution of R. appendiculatus to climatic variables important for the successful application of M. anisopliae in selected East African countries exists. This work therefore aims to improve the successful application of M. anisopliae against R. appendiculatus by designing a temperature-dependent model for the efficacy of M. anisopliae against three developmental stages (larvae, nymphs, adults) of R. appendiculatus. Afterward a spatial prediction of potential areas where this entomopathogenic fungus might cause a significant epizootic in R. appendiculatus population in three selected countries (Kenya, Tanzania, Uganda) in Eastern Africa were generated. This can help to determine whether the temperature and rainfall at a local or regional scale might give good conditions for application of M. anisopliae and successful microbial control of R. appendiculatus.publishedVersio

Diuretic Activity of the Aqueous Extract Leaves of Ficus glumosa

Experiments were carried out to validate the use of F. glumosa extract as a diuretic in the treatment of hypertension as claimed by traditional healers. The experiments were performed under the same conditions with two synthetic pharmacological diuretics considered as check (Furosemide and Amiloride hydrochlorothiazide). The aqueous extract leaves of F. glumosa accelerated the elimination of overloaded fluid. At the maximum of diuretic response, urinary osmolarity decreased significantly when compared with controls. The single dose treatment of the aqueous extract leaves of F. glumosa has significantly increased urine volume 24 h after administration of the extract. The stability of aldosterone level, the absence of correlation with the plasma levels of sodium, and the increased clearance of free water in the animals receiving the extract show that increased diuresis and natriuresis moderate elevation are tubular in origin. The increase in Na+, K+, and Cl− induced by the extract caused alkalinization of the urine and showed a strong inhibitory effect of carbonic anhydrase and saluretic. These effects were mainly observed at the dose of 375 mg/kg. These observations confirm the traditional use in the treatment of hypertension and support the importance of the conservation of local knowledge as well as the conservation of Cameroonian biodiversity

Compatibility between Calpurnia aurea leaf extract, attraction aggregation, and attachment pheromone and entomopathogenic fungus Metarhizium anisopliae on viability, growth, and virulence of the pathogen

Metarhizium anisopliae sensu stricto (ss) (Metsch.) Sorok. isolate ICIPE 07 is being developed as biopesticide for the control of ticks. In addition, leaf extracts of Calpurnia aurea Benth, and the attraction aggregation and attachment pheromone (AAAP) are being used as ticks’ attractant. The three agents are being considered for use in combination in an autodissemination approach, whereby ticks that are attracted to semiochemicals are infected with the inoculum. Experiments were therefore conducted to evaluate in vitro the compatibility between C. aurea, AAAP, and the M. anisopliae on vegetative growth, conidial production, and spore viability. Calpurnia aurea leaf extract was compatible with the fungus at all the concentrations tested, whereas AAAP inhibited all the fungal growth parameters. The virulence of M. anisopliae formulated in emulsifiable extracts of C. aurea was also tested against different developmental stages of Rhipicephalus appendiculatus in laboratory bioassays. No significant differences in virulence were observed between M. anisopliae applied alone and M. anisopliae formulated in different concentrations of C. aurea leaf extracts. These results suggest that C. aurea leaf extracts is compatible with M. anisopliae and could be mixed together for “spot-spray” treatments as low-cost and environmental-friendly technology to control ticks in grazing field, while AAAP should be used separately.Bioscience Eastern and Central Africa Network (BecANet) and the Canadian International Development Agency (CIDA).http://link.springer.com/journal/10340hb2013mn201

Advances in crop insect modelling methods—Towards a whole system approach

A wide range of insects affect crop production and cause considerable yield losses. Difficulties reside on the development and adaptation of adequate strategies to predict insect pests for their timely management to ensure enhanced agricultural production. Several conceptual modelling frameworks have been proposed, and the choice of an approach depends largely on the objective of the model and the availability of data. This paper presents a summary of decades of advances in insect population dynamics, phenology models, distribution and risk mapping. Existing challenges on the modelling of insects are listed; followed by innovations in the field. New approaches include artificial neural networks, cellular automata (CA) coupled with fuzzy logic (FL), fractal, multi-fractal, percolation, synchronization and individual/agent based approaches. A concept for assessing climate change impacts and providing adaptation options for agricultural pest management independently of the United Nations Intergovernmental Panel on Climate Change (IPCC) emission scenarios is suggested. A framework for estimating losses and optimizing yields within crop production system is proposed and a summary on modelling the economic impact of pests control is presented. The assessment shows that the majority of known insect modelling approaches are not holistic; they only concentrate on a single component of the system, i.e. the pest, rather than the whole crop production system. We suggest system thinking as a possible approach for linking crop, pest, and environmental conditions to provide a more comprehensive assessment of agricultural crop production.Peer reviewe

Collecte et évacuation des boues de vidange dans la ville de Bafoussam, Cameroun (Afrique centrale)

L’objectif de ce travail est de décrire le système de collecte et d’évacuation des boues de vidange à Bafoussam, et d’en relever les insuffisances en vue de proposer une méthode pour une meilleure gestion. Les acteurs et leurs rôles dans la chaîne de gestion des boues de vidange ont été identifiés. Les boues ont été collectées, caractérisées et leurs effets potentiels sur les populations environnantes du site de la décharge ont été évalués. Les principaux résultats ont montré que les boues de vidange sont gérées de manière autonome dans deux types d’ouvrages : les fosses septiques (49 %) et les latrines (59 %). Les acteurs intervenant dans la collecte et l’évacuation des boues de vidange sont : la population, la communauté urbaine et une entreprise privée. Les caractéristiques physico-chimiques des boues sont très élevées par rapport aux normes de rejet exigées par l’Organisation mondiale de la santé (DCO, 60 500 mg/l ; NH4+, 1472 mg/l ; PO43-, 1044 mg/l). Près de 1440 m3 de boues de vidange en moyenne sont pompés par an par des camions-citernes et déversées sans traitement au bord de la rivière Noun.The aim of this study is to describe the system of collection and evacuation of faecal sludge in Bafoussam (Cameroon), to raise the insufficiencies in order to propose a method for a better management. The actors and their roles in the chain of management of faecal sludge were identified. Faecal wastes were collected, characterized in the lab and their potential effects on the surrounding populations of the site of the discharge were evaluated. The principal results showed that faecal wastes are managed autonomously in the septic tanks (49 %) and the latrines (59 %). The actors involved in the collection and evacuation of faecal sludge are : population, urban community and a private company. The physicochemical characteristics of muds are very high compared to the norms of rejection required by the World Health Organization (DCO, 60 500 mg/l ; NH4+, 1472 mg/l ; PO4-3, 1044 mg/l). A volume of about 1440 m3 of faecal waste are pumped per year by tankers and are poured without treatment at the edge of the Noun river

Self-organization of plasticity and specialization in a primitively social insect.

Biological systems have the capacity to not only build and robustly maintain complex structures but also to rapidly break up and rebuild such structures. Here, using primitive societies of Polistes wasps, we show that both robust specialization and rapid plasticity are emergent properties of multi-scale dynamics. We combine theory with experiments that, after perturbing the social structure by removing the queen, correlate time-resolved multi-omics with video recordings. We show that the queen-worker dimorphism relies on the balance between the development of a molecular queen phenotype in all insects and colony-scale inhibition of this phenotype via asymmetric interactions. This allows Polistes to be stable against intrinsic perturbations of molecular states while reacting plastically to extrinsic cues affecting the whole society. Long-term stability of the social structure is reinforced by dynamic DNA methylation. Our study provides a general principle of how both specialization and plasticity can be achieved in biological systems. A record of this paper's transparent peer review process is included in the supplemental information

Compatibility between Calpurnia aurea leaf extract, attraction aggregation, and attachment pheromone and entomopathogenic fungus Metarhizium anisopliae on viability, growth, and virulence of the pathogen

Metarhizium anisopliae sensu stricto (ss) (Metsch.) Sorok. isolate ICIPE 07 is being developed as biopesticide for the control of ticks. In addition, leaf extracts of Calpurnia aurea Benth, and the attraction aggregation and attachment pheromone (AAAP) are being used as ticks’ attractant. The three agents are being considered for use in combination in an autodissemination approach, whereby ticks that are attracted to semiochemicals are infected with the inoculum. Experiments were therefore conducted to evaluate in vitro the compatibility between C. aurea, AAAP, and the M. anisopliae on vegetative growth, conidial production, and spore viability. Calpurnia aurea leaf extract was compatible with the fungus at all the concentrations tested, whereas AAAP inhibited all the fungal growth parameters. The virulence of M. anisopliae formulated in emulsifiable extracts of C. aurea was also tested against different developmental stages of Rhipicephalus appendiculatus in laboratory bioassays. No significant differences in virulence were observed between M. anisopliae applied alone and M. anisopliae formulated in different concentrations of C. aurea leaf extracts. These results suggest that C. aurea leaf extracts is compatible with M. anisopliae and could be mixed together for “spot-spray” treatments as low-cost and environmental-friendly technology to control ticks in grazing field, while AAAP should be used separately.Bioscience Eastern and Central Africa Network (BecANet) and the Canadian International Development Agency (CIDA).http://link.springer.com/journal/10340hb2013mn201