122418 research outputs found
Sort by
Genèse et vie de l'arbre qualité de l'unité Contrôle des maladies animales exotiques et émergentes (UMR CMAEE)
No full textRelations between Wallace plasticity and Mw for natural rubber
No full textWallace plasticity and the weight-average molar mass (Mw) were measured on natural rubber samples of different origins. A sigmoidal model describes the relations between Wallace plasticity and Mw (0.872 > r[puissance 2] > 0.992) for given families of samples. The families of samples analyzed differed through their clonal origin, collection method (cup lumps or latex), and type of processing (CV or non-CV). This study showed that two samples of natural rubber can be identical in terms of plasticity, but very different in terms of the average polyisoprene chain length or Mw
Les ressources en sol des régions soudano-sahéliennes
No full textEn liaison avec l'influence de roches variees, les paleoclimats, tantOt tres humides, tantbt h yperarides. sont responsables de I 'organisation spatiale et des caracteristiques des couvertures pedologiques des regions soudano-saheJiennes. Les taxonomies pedologiques sont insuffisantes pour assurer Ie transfert des connaissances sur les ressources en sol. L 'evaluation de ces dernieres depend des facteurs du milieu autres que pedologiques, tels que des contraintes socio-economiques et politiques. 1/ convient donc d 'adopter des demarches d 'evaluation interdiscipJinaires pour en completer l'inventaire qui est pratiquement acheve a petite echeIJe pour bien des pays de la region. Les problemes de classification des sols semblent depasses et non prioritaires. Pour assurer Ie transfert des resultats des recherches agronomiques, la connaissance des relations spatiales, temporelJes et dynamiques entre les resultats experimentaux et les autres facettes de la couverture pedologique locale et d:gionale. est indispensable. La classification necessite des cartographies et etudes de sols interdisciplinaires a differents niveaux
L'unité de purée de mangue aseptique d'Orodara (Burkina Faso) : DAFANI / Assistance technique Cirad 2010 - 2011
No full textLes conditions de déroulement de la campagne 2010, l'impossibilité de mettre en oeuvre les résolutions prises dès 2009 ainsi que les ruptures de stocks dues à une trésorerie défaillante, ont irrémédiablement entraîné un arrêt temporaire de la production en menaçant les emplois et un débouché prometteur pour les producteurs de mangues. Après une cessation quasi-totale d'activité de seize mois, un rééchelonnement de la dette, l'injection de capitaux et la nomination d'un nouveau Directeur général, la campagne 2011 a permis la fabrication d'un stock de 1 200 tonnes de purée aseptique de mangue destinées à la formulation de nectars pour le marché local
The Lokoundje-Nyong oil palm project in Cameroon: Report on a mission from March 20th to 26th
No full textSummary: The Lokoundje-Nyong project aims at creating a new oil palm agribusiness complex 12 km east of Fifinda, which is 74 km south of Edea, along Edea-Kribi road. This area has been identified suitable for oil palm cultivation as early as in 1963 and various projects have been successively planned in 1992, 1995 and 2000 without any start of implementation. On November 1st, 2012 the decree n° 2012/3509 degazetted a 21,552 ha forest concession which was part of a bigger domain of 125,568 ha belonging to the private domain of the State, the Lokoundje-Nyong forest, and attributed it to Biopalm. The LN forest is a production forest registered under UFA 00-003 and a logging permit for its exploitation has been issued to MMG in July 2000 following a bidding process. But the forest has been regularly logged since 1958 and previous loggers (legal and illegal) have harvested the main species of commercial value, so that the present operator can only remove one or two species common on the market. LN forest is undergoing a change in its species composition and it will never recover the state of a pristine forest, except when closed to any further exploitation for a century or more. Human activities include collection of NTFP and hunting by surrounding populations. But animals become rare and distances to meet game increase. Hunting has been banned in the northern part of the forest. The overall economic output of the forest is far below that of a plantation (about 100 times), but national interest in converting 17% of the area of the LN forest to oil palm is not only financial. The country has got short of edible oils and fats, and the situation is getting worse over years. Current deficit is about 40,000 tons and is increasing by 3,250 tons a year. Climate and soil conditions indicate that an average yield close to 22 t FFB/ha could be attained if plantation development is restricted to the most suitable soils, over 60% of the concession. Assuming 24% OER, a 10,000 ha palm plantation will yield 52,800 t CPO a year by 2025. This will not be enough to compensate the whole deficit at that time, but it will greatly reduce it and contribute to alleviate the country's dependence on south-east Asian imports of oils and fats
Root-induced decomposer growth and plant N uptake are not positively associated among a set of grassland plants
No full textIt is known that plant species can induce development of different soil decomposer communities and that they differ in their influence on organic matter decomposition and N mineralization in soil. However, no study has so far assessed whether these two observations are related to each other. Based on the hypothesis that root-induced growth of soil decomposers leads to accelerated decomposition of SOM and increased plant N avail- ability in soil, we predicted that (1) among a set of grassland plants the abundance of soil decomposers in the plant rhizosphere is positively associated with plant N uptake from soil organic matter. To test this, we established grassland microcosms consisting of two plant individuals, a natural soil decomposer community and 15 N-labelled plant litter as organic N source, and compared the rhizosphere decomposer communities and litter-N uptake of a grass Holcus lanatus , an herb Plantago lanceolata and a leguminous herb Lotus corniculatus .We further predicted that (2) in terms of litter-N uptake those plant species that induce lower abundance of decomposers benefit from sharing soil with species inducing higher decom- poser abundance. To test this, we grew the three plant species in two-species combinations and compared the ability of each species to acquire litter-N when living in the monoculture and in the species combinations. We found that the three plant species induced develop- ment of different soil decomposer communities and that they acquired different amounts of litter-N. However, while L. corniculatus induced the highest abundance of decomposers, H. lanatus had the highest uptake of N from the litter, which refuted our first prediction. Since this prediction was falsified, we could not properly test the second one, but we found that litter-N uptake of H. lanatus and P. lanceolata were not significantly affected by the presence of L. corniculatus and the higher abundance of decomposers induced by L. corniculatus roots. Our results show that among the three plant species tested root-induced decomposer growth and plant N uptake from soil organic matter were not positively associated. It appears that plant traits such as competitive ability for soil mineral N were more important for plant uptake of litter-N than those that directly affected the growth of soil decomposers
Eight principles of integrated pest management
No full textThe use of pesticides made it possible to increase yields, simplify cropping systems, and forego more complicated crop protection strategies. Over-reliance on chemical control, however, is associated with contamination of ecosystems and undesirable health effects. The future of crop production is now also threatened by emergence of pest resistance and declining availability of active substances. There is therefore a need to design cropping systems less dependent on synthetic pesticides. Consequently, the European Union requires the application of eight principles (P) of Integrated Pest Management that fit within sustainable farm management. Here, we propose to farmers, advisors, and researchers a dynamic and flexible approach that accounts for the diversity of farming situations and the complexities of agroecosystems and that can improve the resilience of cropping systems and our capacity to adapt crop protection to local realities. For each principle (P), we suggest that (P1) the design of inherently robust cropping systems using a combination of agronomic levers is key to prevention. (P2) Local availability of monitoring, warning, and forecasting systems is a reality to contend with. (P3) The decision-making process can integrate cropping system factors to develop longer-term strategies. (P4) The combination of non-chemical methods that may be individually less efficient than pesticides can generate valuable synergies. (P5) Development of new biological agents and products and the use of existing databases offer options for the selection of products minimizing impact on health, the environment, and biological regulation of pests. (P6) Reduced pesticide use can be effectively combined with other tactics. (P7) Addressing the root causes of pesticide resistance is the best way to find sustainable crop protection solutions. And (P8) integration of multi-season effects and trade-offs in evaluation criteria will help develop sustainable solutions
Life-history traits of Encarsia guadeloupae, a natural enemy of the invasive spiralling whitefly Aleurodicus dispersus
No full textOn south-west Indian Ocean islands, many crops and ornamental plants are threatened by the spiralling whitefly Aleurodicus dispersus (Hemiptera: Aleyrodidae), which is a polyphagous pest that is native to the Caribbean region. Aleurodicus dispersus causes economic damage to various crops on all the islands in the south-west Indian Ocean. The hymenopteran parasitoid Encarsia guadeloupae (Hymenoptera: Aphelinidae) is a natural enemy of A. dispersus on the Caribbean islands. In this study, we assessed the geographical distribution of the parasitoid in La Réunion, an island in the south-west Indian Ocean where the parasitoid was first observed in 2004. We also investigated its main life-history traits. Field surveys indicated that the parasitoid is widespread in most of the low-lying areas of the island and exhibits high parasitism rates on A. dispersus populations. At 25°C, E. guadeloupae adults had a mean longevity of 33.6 days, and its pre-imaginal development required 23 days. The lower temperature threshold and thermal constant were estimated to be 7.9°C and 132 degree-days, respectively. Females of E. guadeloupae preferred to deposit eggs in early rather than in late instars of A. dispersus, and oviposition rates were highest in the second larval instar. Females of E. guadeloupae were able to oviposit in larvae of other species of whiteflies found in La Réunion (Bemisia tabaci and Dialeurolonga simplex), although subsequent development of the parasitoid was not monitored. Finally, we discuss the potential use of E. guadeloupae for the control of whitefly populations on islands in the south-west Indian Ocean
Projet de relance de la caféiculture en Nouvelle Calédonie
No full textLe Programme Café du CIRAD a été sollicité pour participer à l'élaboration d'un programme de recherche-développement pour la relance de la caféiculture en Nouvelle-Calédonie. Les demandes exprimées par les collectivités et les opérateurs locaux permettent de dégager des thèmes d'action qui prennent en compte le contexte agronomique et socioculturel de chaque province. Ces thèmes d'action adressés à la recherche sont indispensables à plusieurs titres. Ils vont servir pour la mise au point de référentiels techniques adaptés, mais également ils vont permettre le développement de la caféiculture en harmonie avec les autres spéculations. Les objectifs fixés à la production caféière sont, d'une part la satisfaction des besoins territoriaux de façon à diminuer les importations, et d'autre part l'exportation de café de haute qualité vers des marchés cibles (niches commerciales). La situation de la caféiculture en Nouvelle-Calédonie est différente suivant les régions, tant par la structure des exploitations que par la nature de la production caféière. Une synthèse de la situation pour chaque province a été établie, fondée sur l'expérience des agents Ciradiens en poste ces dernières années, les publications et les missions récentes sur le Territoire. Cette synthèse met en relief les problématiques qui vont permettre de proposer des axes de recherche-développement répondant aux préoccupations des acteurs de la filière