Common beans in Africa and their constraints

Beans are grown in Africa in a wide range of environments, mainly in the cool highlands of central and tropical eastern Africa, leading to a diversity of cropping systems and agronomic constraints to production. Beans are cultivated for large-scale production or home consumption either in monoculture or in association. The main constraints to production are poor agronomic practices, soil infertility, lack of improved cv., water stress, weed competition, and diseases and pests. Main diseases affecting bean crops in Africa include viral diseases (BCMV, SBMV, BGMV, and BYMV), bacterial diseases (bacterial wilt and bacterial brown spot), and fungal diseases (angular leaf spot, anthracnose, rust, Ascochyta blight, and floury leaf spot). Suggestions for disease management are given, highlighting the use of integrated control. Estimates of annual production per region and crop losses due to pathogens are given in table form. (CIAT)El frijol se cultiva en Africa en un amplio rango de ambientes, principalmente en las areas montanosas templadas de las regiones central y oriental tropical de Africa, lo cual supone diversos sistemas de cultivo y limitaciones agronomicas a la produccion. El frijol se cultiva para produccion en gran escala o para consumo domestico, sea en monocultivo o en asociacion. Las principales limitaciones a la produccion son practicas agronomicas inadecuadas, infertilidad del suelo, falta de cv. mejorados, estres hidrico, competencia de malezas y plagas y enfermedades. Las principales enfermedades que afectan el cultivo del frijol en Africa son las de tipo viral (BCMV, SBMV, BGMV y BYMV), las bacterianas (anublo bacteriano y mancha parda bacteriana) y las fungicas (mancha angular, antracnosis, roya, anublo por Ascochyta y mancha harinosa). Se dan sugerencias para manejo de enfermedades, destacando el uso de control integrado. Se incluyen en forma de tabla estimativos de produccion anual por region y perdidas de cosecha por patogenos. (CIAT

The use of common bean (Phaseolus vulgaris ) traditional varieties and their mixtures with commercial varieties to manage bean fly (Ophiomyia spp .) infestations in Uganda

The bean fly (Ophiomyia spp.) is considered the most economically damaging field insect pest of common beans in Uganda. Despite the use of existing pest management approaches, reported damage has remained high. Forty-eight traditional and improved common bean varieties currently grown in farmers’ fields were evaluated for resistance against bean fly. Data on bean fly incidence, severity and root damage from bean stem maggot were collected. Generalized linear mixed model (GLMM) revealed significant resistance to bean fly in the Ugandan traditional varieties. A popular resistant traditional variety and a popular susceptible commercial variety were selected from the 48 varieties and evaluated in pure and mixed stands. The incidence of bean fly infestation on both varieties in mixtures with different arrangements (systematic random versus rows), and different proportions within each of the two arrangements, was measured and analysed using GLMMs. The proportion of resistant varieties in a mixture and the arrangement type significantly decreased bean fly damage compared to pure stands, with the highest decrease in damage registered in the systematic random mixture with at least 50 % of resistant variety. The highest reduction in root damage, obvious 21 days after planting, was found in systematic random mixtures with at least 50 % of the resistant variety. Small holder farmers in East Africa and elsewhere in the world have local preferences for growing bean varieties in genetic mixtures. These mixtures can be enhanced by the use of resistant varieties in the mixtures to reduce bean fly damage on susceptible popular varieties

Towards a collaborative research: A case study on linking science to farmers' perceptions and knowledge on Arabica coffee pests and diseases and its management

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed. (Résumé d'auteur

Epidemiology in pure stands and varietal mixtures: overview

A review is presented on disease development in bean var. mixtures and in pure stands, the effect on diseases of adding resistance components to susceptible mixtures, and the potential on nongenetic methods to control diseases in mixtures. Four mechanisms seem to reduce disease incidence in var. mixtures: the decrease in spatial density of susceptible plants, the barrier provided by resistant plants, the replacement of susceptible plants with resistant components, and induced resistance. (CIAT