Disease threatens to wipe out cassava in East Africa

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By EA Trade Review Reporter

Agricultural experts and researchers in sub Saharan Africa have raised alarm over a cassava disease that poses to wipe out thousands of acres of cassava in the region.

The experts say the outbreak  now poses a food security threat to over 200 million people in Sub Saharan Africa who depend on the tuber for food and income.

The outbreak of the Cassava Brown Streak Disease, which causes dry rot in the roots rendering them inedible, has defied existing research wisdom, with the disease that was traditionally believed to be confined to lowland coastal areas of Tanzania, now spreading rapidly to even relatively high altitude areas of Uganda and Kenya around the shores of Lake Victoria.


The regional emergency officer of the UN Food and Agricultural Organization (FAO), Jan Helsen, predicts dire consequences to the region if the spread of the disease is not now contained.

“Let's say if nothing happens, if there is no continued support technical, breeding or community-based or sanitisation and, or institutional, then the risk is very high,” Helsen said in a press conference, when announcing the effects of the disease.

“The risk that we'll have an epidemic is very real and the potential impact of food security on millions of people,"

He said the disease has now infected up to 30 per cent of crops in Rwanda and Burundi, and up to 80 per cent in eastern Uganda.

Yet eradicating it poses a major challenge because affected plants show different symptoms in different places. At times, a totally healthy looking plant may be found to have spoiled roots only when harvested, while a plant that looks diseased may actually be healthy.

Other noticeable signs of an infected cassava plant include the plant producing yellow or necrotic vein banding on leaves, which may enlarge and join to form comparatively large yellow patches.

The patches are more prominent on mature, bottom leaves than on younger top leaves. Advanced symptoms are when the leaves become an irregular yellow colour mixed with the normal green colour of the leaves, most often on the edge of lower leaves.

Farmers in western Kenya are already losing over Sh10 million a month in revenue to the disease. Grappling with late detection of the disease, the farmers went to harvest the cassava in October this year only to find they had lost over 70 per cent of their tubers, which were not edible.

The Mwomo Farmers’ Sacco in Bungoma has farmed cassava since 2004 and has steadily moved into value addition, supplying manufacturing industries that make adhesives, and contracted by supermarkets to make cassava bread, snacks and flour.

The proceeds saw them buy modern machinery that has increased their value added output and provided hundreds of community members a source of income through working in the factory.

Today, however, the machines lay idle, a pin-drop silence dominating the factories and the factory workers are idle in their homes as a result of the devastating effects of the cassava streak.

“Our biggest undoing was our inability to detect the disease early. Since we started cassava farming in 2004 we have never had a loss this devastating,” said Matthew Wesonga, a farmer with the Sacco.

“Thousands of tubers now lie in our farmlands, destroyed and there is nowhere to take them. And it now means we have to wait longer for the next season before we can get any more income.”

Scientists blame the spread of the disease on poor agronomic practice like poor cleaning of the planting materials, which further fuels the spread.

Short-term measures to stop the further spread of the disease include early detection, with the FAO advocating increased disease surveillance and regular inspections, increased sensitization of communities to the disease and hands-on training for farmers, including farmer field days.

Other quick interventions include banning the distribution of infected plants between districts and zones, and coping strategies such as the early harvest of cassava, before symptoms appear and significant damage can be done.

According to the FAO, the cassava plant provides up to one-third of the daily calorie intake for people in the countries where the disease is most prevalent.  It is also a relatively cheap source of nutrition for the urban poor.

It has also become an increasingly important export.  The International Food Policy Research Institute estimates that world cassava production will reach 279 million metric tons by 2020 - about 60 per cent of which will come from Africa.

The Cassava brown streak disease was first reported in Amani, Tanzania in 1936 but was confined to the low lands of Eastern Africa and around Lake Malawi.

However, from 2004, it started spreading to mid-altitude areas and has drastically affected cassava production in Central and South-Western Uganda, North Western Tanzania, Western Kenya, and North Western DR Congo.



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