Some short-term investigations into the management of vascular streak dieback disease on young cocoa in Giram estate, Sabah, Malaysia
Vascular Streak Dieback (VSD) disease is the most serious malady of cocoa in Sabah. In 1984, due to frequent and heavy rainfall, the disease attained epidemic proportions making the establishment of nurseries and the field planting of cocoa extremely difficult. In some estates, seedling mortality in both nurseries and field plantings ranged from 56 - 100 per cent. In view of the seriousness of the situation, research was initiated to find immediate and long term solutions to this problem. A trial initiated in Giram Estate suggested that isolation may no longer be a pre-requisite for the establishment of disease-free nurseries. Cocoa seedlings can be raised successfully under polythene roof shelters which keep cocoa leaves rain-free, denying fungal spores the moisture necessary for germination and infection. Another study confirmed previous findings that the earliest and most consistent symptom of VSD infection in young cocoa was a deformed chlorotic flush and the simultaneous appearance of raised lenticels on the stem. Symptoms can appear as early as six weeks, although in the majority of seedlings, symptoms appear 9 - 13 weeks after infection. Using this as a guide, workers can be trained to detect infected material at an early stage thus, preventing the build-up of inoculum in the nursery itself and reducing the amount of infected material being field planted. Five fungicide trials conducted in Giram over a period of 18 months, revealed two new systemic fungicides (triadimenol and PP969) to be highly consistent in conferring protection against VSD infection. In nurseries, foliar sprayings of both compounds at weekly and fortnightly intervals, could provide 82 - 100 per cent seedling protection. In the field, monthly soil drenches of triadimenol at 50 - 100 mg a.i. per seedling provided 95 per cent protection to 15-month old cocoa bushes grown in an environment of high VSD inoculum pressure. The cocoa, being now well advanced in canopy formation and vigour, was less likely to succumb to the disease
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| Format: | biblioteca |
| Published: |
1987
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| Subjects: | MARCHITEZ DESCENDENTE, THEOBROMA CACAO, PLANTULAS, ONCOBASIDIUM THEOBROMAE, VIVEROS, CONTROL DE ENFERMEDADES, FUNGICIDAS, MALASIA, |
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| Summary: | Vascular Streak Dieback (VSD) disease is the most serious malady of cocoa in Sabah. In 1984, due to frequent and heavy rainfall, the disease attained epidemic proportions making the establishment of nurseries and the field planting of cocoa extremely difficult. In some estates, seedling mortality in both nurseries and field plantings ranged from 56 - 100 per cent. In view of the seriousness of the situation, research was initiated to find immediate and long term solutions to this problem. A trial initiated in Giram Estate suggested that isolation may no longer be a pre-requisite for the establishment of disease-free nurseries. Cocoa seedlings can be raised successfully under polythene roof shelters which keep cocoa leaves rain-free, denying fungal spores the moisture necessary for germination and infection. Another study confirmed previous findings that the earliest and most consistent symptom of VSD infection in young cocoa was a deformed chlorotic flush and the simultaneous appearance of raised lenticels on the stem. Symptoms can appear as early as six weeks, although in the majority of seedlings, symptoms appear 9 - 13 weeks after infection. Using this as a guide, workers can be trained to detect infected material at an early stage thus, preventing the build-up of inoculum in the nursery itself and reducing the amount of infected material being field planted. Five fungicide trials conducted in Giram over a period of 18 months, revealed two new systemic fungicides (triadimenol and PP969) to be highly consistent in conferring protection against VSD infection. In nurseries, foliar sprayings of both compounds at weekly and fortnightly intervals, could provide 82 - 100 per cent seedling protection. In the field, monthly soil drenches of triadimenol at 50 - 100 mg a.i. per seedling provided 95 per cent protection to 15-month old cocoa bushes grown in an environment of high VSD inoculum pressure. The cocoa, being now well advanced in canopy formation and vigour, was less likely to succumb to the disease |
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