Mouen Bedimo J.A.,IRAD |
Bieysse D.,CIRAD - Agricultural Research for Development |
Notteghem J.L.,Montpellier SupAgro |
Cilas C.,CIRAD - Agricultural Research for Development
Plant Pathology | Year: 2010
The development of coffee berry disease (CBD) epidemics (caused by Colletotrichum kahawae) in Cameroon was monitored over two successive years (2004 and 2005) on coffee trees protected from rainfall by transparent plastic sheets and on unprotected control trees. This work was done to assess how rain affected disease development when it did not fall directly onto the coffee trees and to determine the influence of primary inoculum on the severity of CBD. Weekly observations over the 2 years showed that there were 1·1% diseased berries on coffee trees completely protected from rainfall, compared with 45% diseased berries on unprotected coffee trees. Disease severity on unprotected trees during the 2 years of the experiment was estimated at 53% diseased berries, compared with 27% on trees only protected in the first year. These results confirmed rainfall as one of the key physical factors in the development of Arabica CBD. They also provided evidence of a subsequent effect of protecting coffee trees from rainfall in 2004 on the severity of CBD in 2005. This suggested some practices that might lead to very effective cultural control of CBD in regions where severe epidemics of the disease occur. Journal compilation © 2010 British Society for Plant Pathology.
Noutcheu R.,University of Douala |
Snook L.K.,Third University of Rome |
Tchatat M.,IRAD |
Taedoumg H.,Bioversity International |
And 2 more authors.
Forest Ecology and Management | Year: 2016
Many species of timber trees in Cameroon are exploited by logging companies for timber and by forest-dependent communities for non-timber forest products (NTFPs). Quantitative analyses were conducted within and near forest concessions in Cameroon to determine the density of multiple use tree species that provide both timber for industry and foods consumed by local populations (fruit and oil or edible caterpillars), and how this has been affected by logging. Individuals of the three species (Moabi, Baillonella toxisperma; Sapelli, Entandrophragma cylindricum; and Tali, Erythrophleum suaveolens), including their stumps, were identified and measured on 5 ha (100 m × 500 m) sample plots around 4 villages and in 2 concessions. Around each village 21 sample plots, stratified by distance, were laid out along three transects extending 10 km towards the concession, each oriented 45° from the other. In concessions, 20 plots were established within the 2012 cutting unit after timber harvesting, using a stratified random system. Moabi trees occurred at the lowest densities: around villages, 22.8 ± 3.3/100 ha of precommercial individuals and 5.0 ± 1.4/100 ha of individuals of harvestable size (⩾80 cm dbh); on concessions, 7.5 ± 2.4 precommercial trees/100 ha, and 0–2.0 ± 1.4/100 ha harvestable individuals. Densities of Sapelli trees were not significantly different between villages and concessions, averaging 32.6 ± 3.8/100 ha and 37.5 ± 5.5/100 ha, respectively, for precommercial sizes and 9.5 ± 2.2/100 ha and 6 ± 1.6/100 ha, respectively, for harvestable trees (⩾100 cm dbh). Pre-commercial Tali trees occurred at lower densities (3.8 ± 0.9/100 ha) around villages, as compared to 11.5 ± 3.1/100 ha on concessions. Harvestable Tali trees (⩾60 cm dbh) occurred at the same densities around villages and on concessions (56.0 ± 7.2/100 ha). Half, or more, of commercial-sized trees of caterpillar-hosting species were left standing after harvest on concessions (89–94% of Tali; 50–79% of Sapelli), reflecting constraints due to timber quality, market demand and inaccessibility. No harvestable Moabi trees were logged from the 2012 cutting areas, reflecting agreements between communities and concessionaires to leave them for fruit and oil, but densities were so low it will be important that villagers conserve those around their villages. Stumps of all three species were found around villages, revealing that mechanisms for negotiation are also needed among villagers with interests in either timber or non-timber resources obtained from the same tree species. © 2016 The Authors
Efole Ewoukem T.,Agrocampus Ouest |
Efole Ewoukem T.,University of Dschang |
Mikolasek O.,CIRAD - Agricultural Research for Development |
Aubin J.,Agrocampus Ouest |
And 3 more authors.
International Journal of Agricultural Sustainability | Year: 2016
In Sub-Saharan Africa, fish ponds are often an integral part of farming systems but have suffered from a lack of viability and sustainability. The present study aims to understand the strategies used by fish farmers to overcome economic and environmental constraints. In 2008 and 2009, fish farmers were surveyed in Central and Western Cameroon, and the fish production systems were classified by cluster analysis. Four broad types were identified according to the complexity of household operations. The development of extensive systems (large-scale and low-input) in rural areas of central Cameroon is induced mainly by abundant available land. For semi-intensive systems in both regions (small-scale and high-input in the Western Region, large-scale and high-input in peri-urban areas of the Central Region), horizontal integration is not sufficient to make fish production profitable and sustainable. More intensive fish farms tend towards vertical integration, in which farmers establish close links with input suppliers. Main causes of low productivity of semi-intensive systems (1–2 t/ha/yr) are both lack of knowledge of fish farming principles by farmers and lack of technical improvement by extension agents and researchers which need to consider the local complexity of farming systems to develop and intensify fish production. The adaptation of development strategies to socio-economic and environmental contexts is a necessity to hope for an increase in fish pond aquaculture production in Africa. © 2016 Informa UK Limited, trading as Taylor & Francis Group
Esong R.N.,University of Yaounde I |
Etchu K.A.,Ekona Regional Agricultural Research Center |
Bayemi P.H.,IRAD |
Tan P.V.,University of Yaounde I
Tropical Animal Health and Production | Year: 2015
Twenty seven mixed-breed growing rabbits (1.2–1.3 kg body weight) aged 10–12 weeks were used to study the effects of the dietary replacement of maize with sun-dried cocoa pod husks on the performance of growing rabbits in a 6-week trial. Three treatment diets were compounded whereby sun-dried cocoa pod husks replaced maize at 0, 50, and 100 %, respectively. The animals were divided among the three treatment diets so that each diet had 3 replicates of 3 animals each. Feed intake and weight gain were recorded; faeces were also collected for digestibility trials, and cost analysis was also carried out. Results showed a significant difference (P < 0.05) in daily feed intake between the dietary treatments. However, there was no significant difference (P > 0.05) in the final metabolic weights, total metabolic weight gain, daily growth rate, and feed conversion ratio between the treatments. The digestibility study showed a decrease in the digestibility of dry matter and metabolisable energy with the increase in cocoa pod husk inclusion. Cost analysis indicate that significant net gains can be made by incorporating 200 g sundried cocoa pod husks per kg of the diet of growing rabbits compared with the same proportion of maize. These results suggest that sun-dried cocoa pod husks can totally replace maize and provide a cheap source of energy in the diets of growing rabbits. © 2015, Springer Science+Business Media Dordrecht.
Yede,University of Yaounde I |
Babin R.,CIRAD - Agricultural Research for Development |
Djieto-Lordon C.,University of Yaounde I |
Cilas C.,CIRAD - Agricultural Research for Development |
And 3 more authors.
Journal of Economic Entomology | Year: 2012
The real impact of true bug damage on cocoa pods has never been assessed precisely. We conducted a 2-yr study on 1,080 cocoa trees on 36 farms in Cameroon to assess the contribution of true bugs to fruit mortality and production loss. The cocoa fruiting cycle, fruit mortality, and damage caused by true bugs as well as other pests and diseases were monitored on a weekly basis. True bug damage also was described on 2,500 ripe pods per year. Pod weight, bean number, and bean weight were measured and compared for different degrees and types of damage on the ripe pods. Our results showed that true bugs were the main external cause of young fruit abortion. They reduced the abundance of young fruit by up to 10%. In contrast, although one-third of the ripe pods sampled had true bug lesions, only 4% were moderately to heavily damaged. The mean weight of ripe pods was reduced by 12% when there was medium to heavy damage. While the mean weight of wet beans was reduced significantly (by 310%), the number of beans per pod was not changed by damage. Despite the reduction in mean weight, the overall weight of beans for the pods sampled was reduced by <2%. Therefore, our study confirmed the common assumption that the economic impact of true bug damage on mature pods is negligible on cocoa farms in Cameroon. However, true bugs have a significant impact on young fruit mortality. © 2012 Entomological Society of America.
Achaleke J.,IRAD |
Brevault T.,CIRAD - Agricultural Research for Development |
Brevault T.,University of Arizona
Pest Management Science | Year: 2010
Background: The cotton bollworm Helicoverpa armigera (Hübner) has developed esterase-mediated resistance to pyrethroids in Central Africa. To gain a better understanding of how quickly this resistance can evolve, its genetic basis and stability were examined in a field-derived strain of H. armigera (474-fold resistant to cypermethrin). Results: Genetic crosses between susceptible, resistant and F1 hybrids indicated that resistance was inherited as a dominant trait (DLD = 0.86) and conferred by a single autosomal gene. The dominance of resistance decreased as the cypermethrin dose increased, so that resistance was incompletely dominant (DML = 0.73) at the highest dose tested. Resistance (DL50) of the F1 hybrid progeny significantly decreased over five generations in the absence of pyrethroid exposure. Conclusion: Rapid selection of resistance alleles due to dominance supports the ability of H. armigera to develop resistance to pyrethroids in Central Africa. However, associated fitness costs provide useful information for managing the evolution of resistance. © 2009 Society of Chemical Industry.
Snoeck D.,CIRAD - Agricultural Research for Development |
Abolo D.,IRAD |
Agroforestry Systems | Year: 2010
In Cameroon, cocoa trees are mostly grown in forests and without fertilization. Our aim was to learn more about the temporal dynamics of soils in cocoa agroforests by comparing young (1-4years old) and old (over 25years old) cocoa agroforests. Short fallow and secondary forest were used as treeless and forest references. The numbers and diversities of soil vesicular arbuscular mycorrhizal (VAM) fungi on 60 cocoa producing farms in the Central province of Cameroon were assessed based on the classical morphotyping of spore morphology. We also observed the soil organic matter, nitrogen and major soil nutrients. VAM spore density was significantly lower in the young cocoa agroforests (16 sporesg-1 dry soil) than in the old cocoa agroforests (36 sporesg-1 dry soil). Levels in the nearby secondary forest (46 sporesg-1 dry soil) were not significantly different from old cocoa. The spore density was significantly highest in the short fallow (98 sporesg-1 dry soil). The Shannon-Weaver index also showed significantly lower biodiversity in young cocoa (0.39) than in old cocoa agroforests (0.48), secondary forest (0.49) and short fallow (0.47). These observations were supported by significant differences in the C:N ratio, Ca, Mg, and cation exchange capacity between young and old cocoa agroforests. We concluded that unfertilized cocoa agroforests could be sustainable, despite a decrease in some soil characteristics at a young stage, due to traditional land-conversion practices based on selective clearing and burning of secondary forest. © Springer Science+Business Media B.V. 2009.
Brevault T.,CIRAD - Agricultural Research for Development |
Brevault T.,University of Arizona |
Nibouche S.,CIRAD |
Achaleke J.,IRAD |
Carriere Y.,University of Arizona
Evolutionary Applications | Year: 2012
Non-cotton host plants without Bacillus thuringiensis (Bt) toxins can provide refuges that delay resistance to Bt cotton in polyphagous insect pests. It has proven difficult, however, to determine the effective contribution of such refuges and their role in delaying resistance evolution. Here, we used biogeochemical markers to quantify movement of Helicoverpa armigera moths from non-cotton hosts to cotton fields in three agricultural landscapes of the West African cotton belt (Cameroon) where Bt cotton was absent. We show that the contribution of non-cotton hosts as a source of moths was spatially and temporally variable, but at least equivalent to a 7.5% sprayed refuge of non-Bt cotton. Simulation models incorporating H. armigera biological parameters, however, indicate that planting non-Bt cotton refuges may be needed to significantly delay resistance to cotton producing the toxins Cry1Ac and Cry2Ab. Specifically, when the concentration of one toxin (here Cry1Ac) declined seasonally, resistance to Bt cotton often occurred rapidly in simulations where refuges of non-Bt cotton were rare and resistance to Cry2Ab was non-recessive, because resistance was essentially driven by one toxin (here Cry2Ab). The use of biogeochemical markers to quantify insect movement can provide a valuable tool to evaluate the role of non-cotton refuges in delaying the evolution of H. armigera resistance to Bt cotton. © 2011 Blackwell Publishing Ltd.
Awa D.N.,IRAD |
Adakal H.,CIRDES Center International Of Recherche Développement Sur L'elevage En Zone Sub Humide |
Luogbou N.D.D.,IRAD |
Wachong K.H.,IRAD |
And 2 more authors.
Ticks and Tick-borne Diseases | Year: 2015
In most parts of the world, ticks are rapidly developing resistance to commonly used acaricides thus rendering control difficult. This constraint is further compounded by the introduction of new species in areas where they did not exist before. Such is the case with the introduction into and rapid spread of Rhipicephalus (Boophilus) microplus in some countries of West Africa. With the looming threat of its further spread in the region, the objective of the present study was to update knowledge on cattle ticks in Cameroon. Among 19,189 ticks collected monthly from 60 animals in 5 herds from March 2012 to February 2013, Rh. (B.) decoloratus was the most abundant species with a relative prevalence of 62.2%, followed by Amblyomma variegatum (28.4%), Rh. (B.) annulatus (0.2%), Rh. (B.) geigyi (0.03%), other Rhipicephalus spp. (8.4%) and Hyalomma spp. (0.3%). Rh. (B.) decoloratus and A. variegatum were also the most widely distributed in space. Infestation rate was generally high, with average tick count/animal of about 80 during peak periods. Tick distribution and abundance in the different sites was as varied as the underlying factors, among which the most important were management systems and climatic factors. The effects of rainfall and temperature were confounded by other factors and difficult to evaluate. However, it appears tick development depends among other factors, on a humidity threshold, above which there is not much more effect. Rh. microplus was not found during this study, but more extensive tick collections have to be done to confirm this. In conclusion, cattle tick infestation in Cameroon remains an important cause for concern. Farmers need assistance in the use and management of acaricides in order to increase their efficiency and reduce the development of resistance. Although Rh. microplus was not found, its introduction from other West African countries is imminent if adequate measures, especially in the control and limitation of animal movements, are not taken. © 2014 Elsevier GmbH.
Saj S.,CIRAD |
Jagoret P.,Montpellier SupAgro |
Todem Ngogue H.,IRAD
Agroforestry Systems | Year: 2013
In Central Cameroon cocoa is mainly produced by household farming systems based on complex associations between cocoa and companion trees. Setup either on native/remnant forest or savannah, these agroforestry systems (AFS) are managed according their geographical position and local pedoclimatic conditions. In this paper, we investigated the effects of local management strategies on carbon (C) storage of live trees in three different cocoa production zones of Central Cameroon. In the 58 fields studied, 8,996 cocoa trees and 1,258 companions were surveyed. Tree sampling was non-destructive and to estimate C storage we used allometric models for above- and belowground biomasses. We measured abundance, height, diameter at breast height and determined species of companion trees. We distinguished between four cocoa plantation age categories (immature, young, mature and senescent) and three preceding systems (forest, forest gallery and savannah). We surveyed farmers' use of each associated tree, allocated it to a functional category and asked if it had been introduced or conserved. Total C content of live trees was on average close to 70 t ha-1. We found that it mostly relied on associated trees-cocoa trees contribution being ac. 2-12 % of live trees total C. The level of contribution to C storage of companions from different use categories differed between sites-trees producing food had contributed most in Bokito and Obala while trees used for shading or fertility contributed most in Ngomedzap. Dynamics of C storage in live trees was found to be independent from cocoa trees growth and age. When aging, AFS continuously lost companion trees and especially conserved ones putatively because of farmers' selective logging. Yet, AFS apparently maintained equivalent C storage abilities with time. Hence, even if cocoa do not contribute significantly to C storage in our study, the systems into which they are included are able to significantly store C and may also contribute to other ecological services such as conservation. © 2013 Springer Science+Business Media Dordrecht.