Cassava mosaic disease

Cassava mosaic disease is caused by a complex of geminiviruses belonging to the genus Begomovirus. These viruses possess circular single-stranded DNA and are considered the most significant biological constraint to cassava production worldwide. They impact the economic stability of regions dependent on cassava as a primary calorie source and industrial starch supplier.

The host range is primarily limited to cassava (Manihot esculenta). The disease is transmitted via infected stem cuttings used for propagation, which allows the virus to persist from one generation to the next. In the field, the virus is efficiently transmitted by the whitefly Bemisia tabaci, which acquires the pathogen while feeding on phloem sap and spreads it to healthy plants during subsequent feeding bouts.

Symptoms are diverse but typically include chlorotic mosaic patterns on leaf blades, which often appear as yellow-green interveinal spots. Affected leaves are frequently reduced in size, curled, and distorted, giving the plant a stunted, bushy appearance. In severe cases, the entire plant canopy shows signs of chlorosis, severely limiting the photosynthetic efficiency and energy production.

Environmental conditions that favor the proliferation of whitefly populations, such as warm and humid climates, directly correlate with the spread of the virus. The virus spreads rapidly through both primary transmission (via infected cuttings) and secondary transmission (via whiteflies). Once a plantation is infested, the disease quickly spreads to neighboring fields if control measures are not implemented.

The economic impact is severe, with yield losses often ranging between 30% and 90% depending on the susceptibility of the variety and the timing of infection. Beyond simple weight reduction, the quality of storage roots is compromised, making them less suitable for traditional food processing and industrial starch extraction. Cumulative impact leads to a total collapse of yield in susceptible cultivars over repeated cultivation cycles.

• Deployment of resistant or tolerant cassava varieties.
• Usage of virus-indexed, certified clean planting materials.
• Implementation of strict phytosanitary practices and sanitation.
• Management of whitefly populations using integrated pest management.
• Rogueing: systematic removal of symptomatic plants from the field.