1. Uganda: Cassava Brown Streak Disease threatens yields (IRIN, New Vision)

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Sarah Nassiwa is a cassava farmer in Mukono district, central Uganda. She cultivates two hectares of cassava. Cassava is a staple crop for her and her family, and provides them with both food and income. But this year she has lost most of her crop to Cassava Brown Streak Disease. “The whole crop is rotten,” she says. She does not know how she will continue to feed and educate her children.

Over the last four or five years, the disease has spread fast. In 2005, it was found in three districts. By 2009, it was reported in 23 districts.

Cassava Brown Streak Disease is a new strain of Cassava Mosaic Disease. According to researchers, almost all varieties of cassava bred to be resistant to mosaic disease are susceptible to Cassava Brown Streak Disease. It has also been found in Tanzania and western Kenya.

The disease affects the edible parts of the plant. When tubers are cut, you see a dry, hard rot with yellowish-brown streaks. But the leaves may be unaffected. You might think your crop is doing fine unless you looked at the roots. Many farmers, like Mrs. Nassiwa, have lost their whole crop. She was happy to have a big garden, but got a nasty surprise when she discovered most of her tubers were rotten.

Farmers in the district of Mukono, like Mrs. Nassiwa, have been hardest hit. Almost the entire crop in the district has been affected. But the disease has also been found in regions previously thought immune. Agriculture officials and researchers say the disease could wipe out the entire Ugandan crop. This could pose a serious threat to food security. In the early 1990s, Ugandan cassava production was wiped out by mosaic disease. Officials in the Ministry of Agriculture are keen to avoid a repeat situation.

Cassava Brown Streak Disease is spread by the whitefly. This insect is found almost everywhere that the crop is grown in Africa. The disease is also spread by planting infected cuttings. For this reason, extension agents are advising farmers to burn or destroy infected plants. Farmers are also being advised to seek clean planting materials, although agricultural officials admit these are costly to buy.