The control of cocoa swollen shoot disease in Ghana.

Abstract Eradication measures have been used in Ghana for over 40 years in attempts to control, or at least to contain, the spread of cocoa swollen shoot virus. This paper considers the effectiveness of the various procedures that have been, or could be, used in the campaign and discusses their advantages and limitations. Removing only trees found with symptoms is shown to be an inefficient method of control, unless outbreaks are very small. It is more effective to remove not only those trees with symptoms, but also all apparently healthy trees adjacent to them. More drastic measures are justified in dealing with large outbreaks and, where these are numerous, the most effective procedure is to clear whole areas and replant in large compact blocks. There is little evidence to justify coppicing trees around treated outbreaks; routine eradication measures could be made more effective if a suitable insecticide were introduced for controlling mealybug vectors. The adoption of virus-resistant varieties has important implications for the effectiveness of the eradication campaign but the full impact cannot be assessed. Much more information is required on this and other aspects of the campaign before definitive recommendations can be made on the most appropriate treatment and replanting policies to adopt in the different cocoa-growing areas. Meanwhile, current operations could be made more effective by making greater use of the information already available.