Aspects of the epidemiology of vascular streak dieback of cocoa in Malaysia

Eradicative pruning of vascular streak dieback (VSD) at three weekly intervals was compared with an unpruned control, in a well replicated trial, in mature monoculture cocoa on an inland soil. Pruning had no appreciable limiting influence on numbers of new infections during, the first four months. During the subsequent eight months, there was an increase in the number of new infections in pruned trees, compared to the control. This indicated that regular pruning at three weekly intervals was not acceptable. A marked increase in infections were recorded coinciding with rainfall above 200 mm two to three months prior to symptom expression and assessment. The above observations suggested a possible new approach to limit VSD infections in mature cocoa, by pruning affected branches twice per year just before disease favourable periods - heavy rain associated with flushing and in increase in susceptible sites for infection, and a peak for sporulation of the fungus. In the nursery, initially, VSD symptoms appeared sporadically in seedlings. Infections increased rapidly in the next three months reading up to 50%.