Cassava Brown Streak Disease: Identification A Problem Among African Farmers
African farmers find it difficult to identify cassava brown streak disease, a virus-related cassava disease, perhaps until the harvest of the crop, as compared to the cassava mosaic disease, say African scientists.
To this end, there is the need to involve farmers in the preparation of policies on how to control the disease, says Philip Abidrabo, plant pathologist at Uganda's National Crops Resources Research Institute.
"The fight against cassava black streak disease requires collective effort, it requires all the stakeholders, first of all the research has to identify varieties that resistant, then we need policy on how a seed or another plant part - a leaf, a piece of stem (germplasm) should be moved within the country and across Africa, as well as the involvement of plant health inspectors", he adds in an interview in Kampala, Uganda during an organised field trip by Biosciences for Farming in Africa (B4FA) for selected Ghanaian journalists.
The exchange trip forms part of the media development fellowship programme of the B4FA being run in four countries, Ghana, Nigeria, Uganda and Tanzania to deepen the knowledge of journalists on issues of biosciences such as biotechnology, among others.
Even though the disease can easily be detected based on the symptoms via diagnostic methods, Abidrabo emphasises that building the capacity of extension workers is also paramount in the identification of the disease.
Cassava brown streak disease is a virus disease that damages the starch-bearing tuberous roots of cassava. The disease is endemic in the coastal lowlands of Eastern Africa such as Uganda, Kenya, Rwanda, Tanzania, Malawi and Mozambique. The insect that causes the disease can be found on cassava almost everywhere in Africa that the crop is grown.
There are a number of different symptoms in the cassava brown streak disease syndrome. On the leaves the disease appears as a feathery loss of the normal green coloration of leaves of plants on either side of the smaller veins. The economically damaging symptom occurs on the tuberous roots as a yellow/brown, the death of most of the plant in the starch-bearing tissues due to the disease.
Cassava experts fear that the increased spread of Cassava Brown Streak Disease could cause a 50 percent drop in production of the crop that provides a significant source of food and income for 300 million Africans.
In Africa, cassava provides a basic daily source of dietary energy. Roots are processed into a wide variety of granules, pastes, flours, etc., or consumed freshly boiled or raw. In most of the cassava-growing countries in Africa, the leaves are also consumed as a green vegetable, which provides protein and vitamins A and B.
Since the outbreak of the disease eight years ago, currently there is no variety that is resistant to cassava brown streak disease, however, there is a variety which is tolerant that can get the disease but the incidence is very low and research mainly focuses on that, Abidrabo notes.
In spite of the fact that cassava brown streak has yet to be reported in west Africa, he believes more vigilance is needed in undertaking monitoring surveys of the disease in addition to collaboration with other African research institutes.
The head of the National Cassava Research Programme at the National Agricultural Research Organisation, Titus Alicai says given that Sub Saharan Africa is the world's leading producer of cassava, prevention of the disease needs to be given great attention.
"We need to do everything possible to prevent introduction of the disease, so there is vigilance that is required with the plant quarantine services in West Africa, they need to make sure this disease is not introduced into West Africa cassava stems".
Alicai says if there is any introduction of cassava from east Africa those materials need to be thoroughly checked and screened for the viruses that cause the disease.
"But the region can also begin to proactively prepare in case nature moves it there because these things are moved by insects through breeding efforts taking into accounts breeding for resistant cassava which are common in east Africa which can be carefully into west Africa, " he adds.
Claude Fauquet, a scientist at the International Center for Tropical Agriculture (CIAT), who heads the Global Cassava Partnership for the 21st Century (GCP21) says cassava is already incredibly important for Africa and is poised to play an even bigger role in the future, hence the need to move quickly to contain and eliminate the cassava brown streak disease.
"We are particularly concerned that the disease could spread to West Africa and particularly Nigeriathe world's largest producer and consumer of cassavabecause Nigeria would provide a gateway for an invasion of West Africa where about 150 million people depend on the crop," he states.