Vascular streak dieback of cocoa in West Malaysia [fungal diseases]
1982
Zainal Abidin Mior Ahmad
The causal pathogen was isolated and the symptomatology relating to infection of mature cocoa and seedling in the nurseries described. Morphological studies of the local isolates have confirmed the close similarity of the VSD fungus to Oncobasidium theobromae Talbot and Keane. Techniques useful for isolation of the pathogen in routine and sequential samplings were investigated. A survey of the disease undertaken confirmed incidence of VSD in mature plantings in Trengganu, Johor, Perak and Malacca; cocoa nurseries in Perak and Johor; and clonal plantings in Negeri Sembilan. In all cases, the percentage incidence and severity varied from locality to locality. Generally, the survey of clonal plantings provided information on the relative susceptibility within clones. The fungus hitherto recorded to grow poorly on artificial media was found to grow satisfactorily on Corticium culture medium and on Leonian's solution agar. Epidemiological investigations showed significant correlation between disease incidence and rainfall. The effects of systematic fungicides for controlling VSD in the nursery were studied
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