Cassava Mosaic Disease

Infected leaves show a characteristic mosaic of yellow and green patches, often with distortion, twisting, and reduction in leaf size. Severely affected plants are stunted, with small, misshapen leaves and reduced canopy, and produce fewer and smaller storage roots. Symptom severity varies with the virus involved, the variety, the age of the plant at infection, and whether the plant grew from an infected cutting or was infected later by whitefly.

Cassava mosaic viruses are transmitted from plant to plant by whiteflies and are carried over in infected cuttings used for propagation. When a grower plants a cutting taken from an infected plant, the resulting plant is infected from the start. Whiteflies then acquire the virus from infected plants and transmit it to healthy ones, allowing the disease to build up within and spread between fields.

• Infected stem cuttings carry the virus directly into new plantings
• Whiteflies transmit the virus between plants in the field
• High whitefly populations accelerate field-to-field spread
• Volunteer and neighbouring infected cassava act as virus reservoirs

Cassava is the primary host of concern. The disease is favoured by abundant whitefly populations, the routine use of cuttings from unselected or infected plants, and continuous cassava cultivation that maintains virus reservoirs. Warm conditions that favour whitefly activity increase transmission.

• High whitefly populations and conditions that favour the vector
• Use of cuttings taken from infected or unselected plants
• Continuous cassava with nearby infected plants as reservoirs
• Susceptible varieties that express severe symptoms

Because the virus spreads through both cuttings and whiteflies, management combines resistant varieties, clean planting material, and removal of infected plants. Using healthy cuttings and improved varieties has been central to reducing the impact of the disease in affected regions.

• Plant resistant or tolerant varieties recommended for the local area
• Use clean, virus-tested planting material from healthy mother plants
• Select cuttings only from symptom-free plants
• Remove and destroy infected plants (roguing) to reduce virus sources
• Manage whitefly populations and nearby infected reservoirs where feasible