Abstract:

Cassava (Man/hot esculenta, Crantz) is a major staple crop, providing carbohydrates for about 80% of the Ugandan population. It is grown in many parts of Uganda, with the Eastern and Northern regions as the largest producers. The ability of cassava to better survive under low rainfall and poorer soils than other crops, partly contributes to expansion of areas growing cassava in Uganda. In 2011, Uganda produced 4,753,430 tonnes of cassava, of which 63-72% was consumed as food, 22-27% was processed as feed and about 2-7% used for other purposes such as raw material for starch, brewing alcohol and local construction. 22.2% of the total cassava produced was sold at farm level. At farm level, cassava yields at only 12.5 t/ha, far below the average yield of 25 t/ha achieved on research stations. The actual genetic potential of cassava is 80— 90t/ha. Pests and diseases are the main reason for low yields of cassava in Uganda. Cassava pests in the Uganda include cassava mealybug (Phenacoccus manihoti Mat-Ferr), cassava green mite (Monychellus tanajoa Bondar) and whitefly (Bemisia tabaci Genn.). The major diseases of cassava in Uganda are cassava mosaic disease (CMD), cassava brown streak disease (CBSD) and cassava bacterial blight (CBB). CBSD has been recognized as one of the seven most dangerous plant diseases globally for their impact on food and economic security. Yields in individual farmers' fields can drop up to 100% as a result of CBSD. By 2003 just at the beginning of the current epidemic, economic losses of cassava due to CBSD already totalled more than $100 million per year (CGIAR, News 2003). From this, it is reasonable to estimate much higher losses under current conditions of higher CBSD prevalence. Significantly, the disease has become an extremely serious constraint to cassava production in Eastern Africa and has been linked to Africa's biggest threat to food security. Concerted efforts are therefore needed to manage it. Here we present the trends in the spread of CBSD from our annual pest and disease surveys of 2008 to 2011 in Uganda.