Agriculture Reference
In-Depth Information
maize rust (caused by
Puccinia polysora
) and cacao swollen shoot virus disease in
West Africa and sugarcane mosaic virus disease, which greatly stimulated research
on these important crops and led ultimately to the introduction of improved
genotypes and enhanced crop productivity (Thresh, 1990). Such benefits are
emerging already with cassava in Uganda and elsewhere and will be even more
apparent if the latest CMD-resistant varieties fulfil their early potential.
20.4.9 The situation in adjoining countries
Kenya:
As the epidemic spread across Uganda in the 1990s it became inevitable that
the neighbouring countries of Kenya, Tanzania and Rwanda would soon be affected.
The threat first became a reality in 1995, when the severe effects of the epidemic
were evident in Mbale and Tororo districts of eastern Uganda along the border with
western Kenya, south of Mt Elgon (R.W. Gibson, unpublished report). Surveys in
adjacent parts of Kenya then revealed a high incidence of recent infection associated
with unusually large infestations of
B. tabaci
. Western Kenya was at the time the
most important cassava-producing area of the country and accounted for
c.
63% of
total national production. CMD had occurred previously in the region, but the
incidence and severity of the disease were generally low and there was considerable
use of infected cuttings as planting material and little spread by whiteflies.
Subsequent surveys of western Kenya in 1997 and 1998 showed a progressive
spread of the epidemic westwards to reach Kakamega and Kisumu on Winam Gulf
of Lake Victoria. As in adjacent parts of Uganda, the farmer-selected varieties being
grown were extremely vulnerable to infection. Severe damage occurred and there
were few suitable cuttings available for new plantings. This led to a drastic decline
in production as farmers lacked access to CMD-resistant varieties, except where
these were acquired by farmers from adjacent parts of Uganda. Losses in western
Kenya in 1998 alone were estimated at more than 140,000 t, worth US$10 million
(Legg, 1999).
The eastward spread of the epidemic in western Kenya was restricted by an
extensive area of high ground that is mainly forested and unsuitable for cassava
cultivation. In contrast, areas south of Kisumu along the eastern side of Lake
Victoria were considered to be at serious risk in 1997 to 1998 (Legg
et al.,
1999).
There has since been continued spread southwards towards the Tanzania border.
However, spread has been less rapid than expected and seems to have been impeded
by the natural barriers of the Winam Gulf and the Nyando Plain that separate north
from south Nyanza Province.
Monitoring operations in western Kenya have been funded by grants from the
US AID Office for Foreign Disaster Assistance (OFDA), which has also supported
similar activities in north-west Tanzania and Burundi. Moreover, OFDA, Gatsby,
Rockefeller and other donors have supported attempts to restore production in the
areas of western Kenya that were first affected. Initially, Nase 3 and Nase 4 (SS4)
were introduced from Uganda and multiplied for release to farmers. Subsequently,
other selections were made from CMD-resistant material introduced from the IITA
regional cassava breeding programme based at Serere in Soroti district of Uganda.
