UGANDA: Cassava disease threatens food supplies in a country, where 70 per cent feed on the root
KAMPALA, 20 May 2010 (IRIN): Agriculture officials and researchers in Uganda have warned of a serious threat posed by a new strain of Cassava Mosaic Disease, saying it could wipe out the entire crop.
Farmers in the central district of Mukono have been hardest-hit by the Cassava Brown Streak Disease (CBSD), a devastating viral infection that affects the edible parts – the tuberous roots and sometimes leaves – leading to a total loss of yields in most cases. It is spread by white flies.
Mike Thresh, a consultant on cassava viral diseases, said the disease was now occurring in areas previously believed to be immune, such as high altitude areas away from the Indian Ocean coastal belt of Kenya, Tanzania and Mozambique.
– Initially there was a sort of dogma that built up in scientists that there is an altitude ceiling and that the disease was not a problem once one exceeded 1.000 meters above sea level, Thresh said, adding:
– The gravity of the situation is that almost all varieties bred or selected for resistance to Cassava Mosaic Disease [CMD] are susceptible to the “new strain” of CBSD occurring in Uganda, inland areas of Tanzania and Western Kenya.
– Unlike the case of mosaic disease where the plant is affected as well as the yields, in the case of CBSD, the plant remains extremely vigorous (livlig) and you pass by it and conclude that it is okay, but the problem comes when you look at the roots. What is more worrying is that it takes about 10 years to develop a variety, Thresh said.
The symptoms include root constriction and a dry hard rot when the root is cut. It also causes cracks and discolouration in the tubers while the harvested roots have corky, yellow-brown spots. It causes patches of yellow mixed with normal green on the leaves, a phenomenon commonly referred to as chlorosis.
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