Cassava viruses threaten food security

Written by Joao Junior, Plantwise Knowledge Bank Intern.

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Cassava farmer. Copyright CABI.

Known as the poor people’s crop, cassava (Manihot esculenta Crantz) is one of the most important subsistence crops in Africa, particularly in sub-Saharan Africa and West Africa being consumed fresh, cooked or processed. It is estimated that cassava contributes to nearly 40% of the total daily calories consumed by poor smallholders in marginal and sub-marginal areas. The significant contribution to daily calories is due to its efficient production and storage of starch on the roots.

As a food security crop, cassava has many advantages when compared to other important food crops such as maize and rice. On production level, it can be grown in low quality and acidic soils, is tolerant to drought, and does not require expensive inputs, fertilizers and seeds making it affordable to resource-poor farmers. Also, cassava is wide adapted to a range of agro-ecological zones.

According to FAO, more than 70 million people in eastern, central and southern Africa rely on cassava as their staple food and therefore, poor production and post-harvest losses have a significant impact on food supply and availability.

The FAO estimate that the production of cassava has doubled in Sub-Saharan Africa, reaching 140 million tonnes in 2010. Approximately ninety percent of the production is for own consumption and ten percent processed for animal feed. However, despite this significant increase in production in the last decades, environmental degradation and disease pressure is threatening the sustainability and resilience of the system particularly for small farmers.

Disease pressure caused by pests and viruses is considered the most important factor causing low productivity and deterioration of cassava roots because successful production of cassava depend on healthy and virus free propagation material. According to Patil, 2015, Cassava is susceptible to over twenty different types of viruses and the most important are cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The FAO estimates that new cassava diseases are identified every 7-10 years, which makes the fight against it more difficult.

The impact of viruses on cassava plants range from morphological distortion of leaves to significant decrease on root yield. A study conducted by Olufemi (2011) on CMD in sub-Saharan Africa suggests yield losses between 15-24% and economic losses of approximately US$1 billion every year.

The FAO believe that at the community level, lack of information about the causes of diseases and methods of prevention, poor plant health and extension services are the main areas that need attention in order to improve productivity. The Plantwise Knowledge Bank contains 361 Factsheets and Photosheets on cassava to ensure that extension services around the world have access to locally relevant, effective, and safe advice on how to prevent, diagnose, and manage cassava pests and diseases. This content is free and available to all online on the Knowledge bank website or offline on the Plantwise Factsheets Library App.

References

Food and Agriculture Organization. 2010. Cassava diseases in AFRICA a major threat to food security-Cassava diseases in central, eastern and southern Africa (CaCESA) Strategic programme framework 2010-2015.

Alabi, O. J., Kumar, P. L., and Naidu, R. A. 2011. Cassava mosaic disease: A curse to food security in Sub-Saharan Africa. Available at: http://www.apsnet.org/publications/apsnetfeatures/Pages/cassava.aspx (Accessed: 12 July 2016).

Patil, B.L., Kanju, E., Legg, J.P. and Fauquet, C.M. 2015. Cassava brown streak disease: A threat to food security in Africa’, Journal of General Virology, 96(5), pp. 956–968.

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