Agriculture Reference
In-Depth Information
•
The current pandemic provides an example of the way in which the occurrence
and control of a disease is closely associated with the vulnerability of the
varieties being grown and the availability of resistant varieties.
•
Experience with CMD in Uganda demonstrated the advantages of adopting an
ecological approach in seeking to explain the main features of the epidemic in
the country and of the pandemic in the region and their effects on the amount
and type of cassava grown.
•
Research on CMD and the viruses responsible has benefited greatly from
collaboration between virologists in the tropics and those in developed
countries of Europe and North America with access to sophisticated laboratory
equipment and techniques.
•
The highly successful outcome of the research and extension activities mounted
in Uganda in response to the epidemic provides a striking example of the
benefits to be gained from such investments in agriculture, as evident from the
very favourable benefit/cost ratios reported.
This chapter briefly considers the main features of CMD and its history, distribution
and importance in Africa. The recent epidemic in Uganda is then discussed together
with the approaches that were adopted to achieve control. Additional information
and further details of the control measures introduced and deployed in Uganda are
presented elsewhere (Otim-Nape
et al.,
2000). The emphasis here is on the main
features of general epidemiological interest.
20.2 CASSAVA AND CASSAVA MOSAIC DISEASE IN AFRICA
Cassava (
Manihot esculenta:
Euphorbiaceae) is a semi-woody perennial that is not
known in the wild. The crop is considered to have evolved from wild
Manihot
species in South/Central America, where it has been cultivated for millennia.
Cassava is still widely grown in the neotropics, which currently account for
c
. 18%
of total world production - estimated to be
c.
185 million tonnes per annum (FAO,
2003).
The tropical areas of sub-Saharan Africa now form the main region of cassava
production, even though cultivation did not begin there until comparatively recent
times following the introduction of the crop to coastal areas of West Africa in the
sixteenth century and to coastal East Africa in the eighteenth century (Jones, 1969).
Cassava soon spread inland from the coastal areas, but does not seem to have been
widely grown until the twentieth century. Production then expanded rapidly in many
countries and in very diverse agroecologies. The total area cultivated is currently
estimated to be 11.2 million hectares (M. ha) and the leading producers are Nigeria
(3.5 M. ha), Democratic Republic of Congo (DRC) (1.8 M. ha), Mozambique (0.9
M. ha) and Ghana (0.8 M. ha). However, the area exceeds 50 000 ha in each of 17
other African countries (FAO, 2003).
In Africa, cassava is grown mainly for the tuberous roots, which are used for
human consumption in diverse forms. The leaves are also consumed in DRC and
some other countries as an important component of dietary protein and vitamins.
