Cocoa swollen shoot virus disease (CSSVD)

CSSVD is endemic to West Africa and is a new encounter on cocoa. Several different strains of the virus exist, and the most severe strains cause drastic yield losses and tree death in susceptible trees within 5 years. 

Following a countrywide survey In Ghana in the 1940’s, a campaign was implemented to try to eradicate the virus by ‘cutting out’ or destroying 50 million infected trees. 

The campaign was ultimately unsuccessful and CSSVD is widespread today in both Ghana and Côte d’Ivoire. Due to the lack of effective control methods for this disease, a similar eradication programme is again underway in West Africa to try and stop the spread of the virus.

The virus is transmitted by several different species of mealybugs (Pseudococcidae) which are tended and redistributed on plants by black ants. 

As there are currently no direct methods to control the virus itself (apart through breeding for resistance), management strategies have concentrated on control of the mealybug vectors.

Systemic organophosphate insecticides (that are no longer permitted under EU regulations) have been tested for control of the mealybugs, but they were hazardous and had little effect. 

Although modern insecticides are under test, it is too early to recommend them as an effective control technique, and current research on managing this virus is focused on breeding resistant varieties.

Biocontrol using predators, parasitoids and entomopathogenic fungi has been explored, but not successfully. 

Classical biocontrol of papaya mealybug has been a success in Ghana using parasitoids from Central America, the area of origin of the pest, but the situation is more complex with CSSVD as the main vector is an indigenous mealybug. 

Barrier crops (non-host) have been used to try and restrict the movement of the juvenile mealybugs [1], but this requires long-term planning, land and is expensive. 

Without adequate control measures, eradication being the best current option and a lack of resistant/tolerant cocoa planting material to replace the susceptible plants, it may only be a matter of time before cleared and replanted areas become re-infected again.