Cassava Mosaic Disease in Kenya
In Kenya cassava is grown in over 90,000 ha. with an annual production of about
540,000 tons. Cultivation is mainly in western Kenya comprising of Nyanza and Western
provinces (60%), Eastern (10%) and Coast Provinces (30%). The crop is grown by small
holder poor households for subsistence and it is an important food security crop.
Major constrains of cassava production include pests and diseases, poor agronomic
practices, low yielding varieties, high cyanide levels, lack of clean planting materials
and long maturity periods.
Cassava mosaic disease (CMD) is the most important, as it results in highest yield
losses. CMD was for over a century recognized on cassava, but was not considered
a major problem. In the mid 1990s the situation changed dramatically when an unusually
severe form of CMD caused yield losses of 80-100% on farmers’ fields. Between 1995-1998
annual yield losses of cassava was approximated at 150,000 metric tons valued at
US$ 10 million. In Nyanza province alone, yields declined from 7-10 t/ha to less
than 3 t/ha while the area under production has declined from 25,000 to 17,000 ha.
The disease initially spread from Uganda to the neighboring Kenyan districts of
Teso, and Busia, and has now spread to other districts in Western and Nyanza provinces
forcing farmers to abandon cassava cultivation. All the local varieties have been
devastated and affected farmers are experiencing acutely reduced incomes and general
insecurity at the household level.
The International Institute of Tropical Agriculture (IITA) through the East African
Root Crops Research Network (EARRNET) in collaboration with the Kenya Agricultural
Research Institute (KARI) initiated a program in 1997 to mitigate the effects of
CMD in western Kenya. Gatsby Charitable Foundation (UK), Office of Foreign Disaster
Assistance (OFDA, USA) and Rockefeller Foundation pooled resources to restore cassava
cultivation in the region. The main objective was to develop and distribute CMD
resistant, high yielding varieties with good tuber qualities to farmers. This involved
germplasm enhancement and exchange from Uganda. A total of 1404 clones have been
introduced from Uganda to Kenya through Alupe Open Quarantine station for evaluations
and 22 clones so far are under multiplication in 12 sites in Nyanza and western
Provinces. The clones have been introduced and evaluated in KARI centers in preliminary
yield trials, and advanced to on-farm trials through participatory evaluation in
To accelerate the multiplication and distribution of high yielding CMD resistant
varieties, a three-tier (primary, secondary and tertiary) multiplication system
was adopted to allow all classes of farmers’ access the clean planting materials.
The selected clones are first bulked at primary sites which are usually government
controlled sites (Farmer Training Centers, Government Prison Farms, Research Institute
farms), then moved to secondary sites at district levels which are managed by the
district steering committees especially lead by the Ministry of Agriculture Extension
Staff. The materials then trickle to tertiary multiplication sites managed by individual
farmers, farmer groups and other partners (NGOs, CBOs etc).
Although large quantities of planting materials have been produced at primary level,
this has not translated to farmers planting large areas, which indicates losses
of planting materials as they move from primary, secondary, and finally to tertiary
sites and the farmers. Although most primary bulking sites have irrigation facilities
secondary and tertiary bulking sites rely on rainfall. Low and poorly distributed
rainfall leads to poor sprouting and growth of the cassava cuttings, reducing the
number of cuttings available for the
next stage. In some of the secondary and tertiary
bulking sites the establishment has been less than 60%.
At the tertiary sites , farmers do not usually conserve cassava planting materials
after harvesting the roots during the dry spell. In some cases livestock are allowed
to graze in the cassava fields. This results in the cassava planting materials drying
and being used as fire wood or destroyed by grazing livestock. The multiplication
of CMD free planting materials requires phytosanitary measures such as roging or
uprooting of diseased plants. Poor food insecure households involved in bulking
at tertiary levels are sometimes reluctant to rogue the diseased plants resulting
in the spread the disease, reducing the amount of planting materials.
In Kenya, there have been two important trends concerning the status of CMD. Since
the onset, promotion of CMD free planting material has been concentrated mainly
in western Kenya districts of Busia, Teso and Siaya where symptoms were noted first
- Data from areas of Western Kenya towards the border with Uganda showed reduction
in both incidence and severity of CMD in comparison with the previous years1 (Legg
- There is evidence for continued movement of the severe CMD infection into
southern Nyanza (Homabay , Kuria, Migori, Rachuonyo, Suba and Gucha districts)