Farmers count 110bn/- losses as brown streak disease ravages cassava

ABDUEL ELINAZA

CASSAVA farmers in the country lose billions of shillings annually to cassava brown streak disease (CBSD), which researchers have been battling for the past two years.

The disease, believed to exist since 1931, is a virus which remained idle for decades until some ten years ago when it went viral. However, hopes are on the horizons since researchers at International Institute of Tropical Agriculture (IITA) in Tanzania are close to the solution.

IITA’s Plant Virologist, Dr James Legg, said yesterday that researchers are working on finding host-plant resistance or deployment of less-susceptible cultivars. “The disease is devastating. Currently, farmers are losing some 50 million US dollars (about 110bn/-), a year to the disease,” Dr Legg said.

Dr Legg was briefing journalists who toured the IITA research lab as part of celebrating its 50 years of serving farmers. He added: “This is a major problem as farmers cannot reap the fruits of their hard labour.

” Though researchers can easily recognise CBSD on cassava leaves, farmers can only identify the problem during harvesting time. The affected cassava always has its roots rotten. “We have managed to control cassava mosaic disease by producing quality and clean seeds and educating farmers to avoid using harvested plant as seeds.

This time around, we are fighting CBSD,” Dr Legg said. IITA Cassava Breeder, Dr Edward Kanju said, in his paper named ‘CBSD in East Africa the fight continues,’ that by developing four disease tolerant varieties IITA is optimistic of curbing the diseases.

“These varieties (out of 30 highly promising breeding lines) have been proposed for a oneyear evaluation under National Performance Trials. (This is) final step towards full official release,” Dr Kanju said. Dr Kanju believes that once these four varieties are released, they will have dual resistance or tolerance for CBSD and CMD for the Lake Zone areas.

He said Lake Zone is among most affected areas. To accelerate the findings, IITA breeders have borrowed nine Nigerian cultivars by tissue culture where they were evaluated for CBSD resistance in the field for three seasons at Chambezi - a known disease hotspot.

Initial findings have shown that two cultivars had either a significantly higher marketable yield of fresh roots or recorded same performance as ‘kiroba’ which is the improved control variety.

“If they performed well, these two cultivars will be used as new sources of resistance to generate new varieties that are truly resistant to CBSD,” Dr Kanju’s paper shows. IITA researchers said the viral disease has caused many farmers, especially in the Lake Zone to abandon cassava farming altogether.

Farmers are said to produce around 8 tonnes per hectare.

The main production areas of cassava are Mwanza, Mtwara, Lindi, Shinyanga, Tanga Ruvuma, Mara, Kigoma, the coastal regions and Zanzibar.

CBSD and CMD together cause production losses worth more than one billion US dollars (2.2tri/-) every year and are a threat to food and income security for over 30 million farmers growing cassava in East and Central Africa.