Cassava Brown Streak Disease threatens African food security as virus spreads beyond East Africa

Key facts

• Cassava Brown Streak Disease causes root necrosis and can lead to total crop loss in infected cassava plants.
• About 33.7 per cent of Africa — roughly 10.2 million sq km — is at risk of CBSD spread.
• The virus is primarily transmitted by the whitefly Bemisia tabaci, with Sub-Saharan Africa 1 and 2 populations highly efficient vectors.
• CBSD remained largely endemic for more than 70 years along coastal Tanzania and Mozambique before spreading to Uganda and other East and Central African areas.
• Scientists fear westward expansion into major cassava producers Nigeria and Ghana if control measures are not strengthened.
• Weak formal clean-seed systems and farmer reuse of infected cuttings perpetuate disease spread across smallholder farms.
• Dual-resistant varieties are under evaluation in Democratic Republic of Congo, Tanzania, Uganda, Mozambique, Malawi, Cameroon, Zambia, Brazil and Vietnam.
• Ethiopia has not reported CBSD or its whitefly vector; local studies show field spread via whiteflies is limited to around 17 metres per season.