Cacao swollen shoot virus

Cacao swollen shoot virus (CSSV) is a serious viral disease caused by members of the Caulimoviridae family. It is recognized as one of the most destructive threats to cocoa production globally, specifically targeting the vascular systems of host plants.

The disease primarily affects Theobroma cacao, the plant from which cocoa beans are harvested. It is particularly prevalent in West Africa, where it has caused massive losses in productivity, often requiring the eradication of millions of infected trees to prevent wider outbreaks.

The hallmark symptoms include characteristic swellings or nodules on the stems and roots of the tree. Infected leaves often display striking patterns, such as mosaic chlorosis, red-vein banding, and general deformation. Over time, the canopy thins, dieback occurs, and the tree ceases to produce pods effectively.

Transmission occurs through insect vectors, primarily mealybugs (Pseudococcidae), which transmit the virus while feeding on the phloem of host trees. The virus can persist within the vector for a limited time, and its spread is highly correlated with the movement of these insects between interconnected canopies.

Management strategies are focused on the removal of infected trees (the "cut-out" method) to reduce the viral inoculum in the environment. Additionally, researchers are developing cocoa varieties with genetic resistance to the virus, and integrated pest management (IPM) is employed to control mealybug populations in vulnerable areas.