Vascular streak dieback (VSD)

Ceratobasidium theobromae is an important fungal disease in the South-East Asia and Pacific region, infection causes dieback of the branches.

The disease is particularly dangerous for seedlings, but also capable of killing mature trees of susceptible varieties. This is another ‘new encounter’ disease on cocoa, from an endemic host in the region which as yet has not been identified.

In addition to leaf chlorosis, internal staining and dieback new symptoms have recently been seen in Indonesia, including leaf necrosis and spore production on the leaf veins and stems, leading to the suspicion that there may be a more severe strain of the disease.

Vascular streak dieback (VSD) — Symptoms of VSD: staining in the tissue of the leaf scar-three brown dots (left) and white fungal growth on the leaf veins and stalk (right). Curtesy Phil Keane

Management of VSD has centred around planting resistant/tolerant materials, monitoring and phytosanitary pruning to remove affected branches.
Suitable fungicides are still being investigated to primarily protect young plants in the field and seedlings in nurseries when disease pressure is at its highest – fungicide application to mature trees is not effective or economical at this time.
Biocontrol is not thought to be an option for management in the field, however, there is a Trichoderma product commercially available in Indonesia for application to the soil which requires further investigation.