PESTS AND DISEASES Cocoa is host to a large number and variety of organisms, for example, numerous insect species are known to feed 011 the tree. Others are vectors of fungal and viral diseases, and new pests are continually being introduced to the region. This emphasises the need for strict quarantine precautions to limit further spread, The distribution of important pests and diseases of cocoa are summarised in Table 6. Modification of Environment Maintenance of a complete canopy and overhead shade minimises mirid damage. The incidence of black pod may be reduced by light access pruning to reduce humidity within the plantation. Chemical Control A wide variety of insecticides and fungicides are in use, for instance organochlorines to contain mirids in West Africa and world-wide application of copper-based sprays against black pod. Wax poison baits, incorporating an anticoagulant, have proved very efficient in rat control. The use of toxic compounds requires careful management: personal and environmental contamination must be avoided, and some pests have developed resistance after prolonged, exposure to some compounds. Methods of biological control appear to have had little attention, although certain ant species have been introduced to drive out mirids and Pantorhytes, weevils.
Unit 6: Production of Plantation Crops 6.58 Selection and Breeding Some varieties show some resistance or tolerance to some of these pests and diseases, and these characteristics are likely to be increasingly incorporated into selection and breeding programmes. Harvesting Like most tropical crops, fruit ripening in cocoa is not confined to a short harvest period. Pods are borne year round, but most cocoa is harvested in two flushes during the year. These peak harvest periods may each last about three months. Pods are suitable for harvesting for a period of 2-3 weeks; beans from unripe pods give a poor ferment, while over-ripe beans may germinate in the pod. Cocoa is often harvested fortnightly, although weekly harvests may be undertaken during the main flush period to minimise losses to pod rots and animals. In harvesting, pod stalks should be cut with a sharp blade. Care is required to avoid damaging the flower cushion, as future flowers and pods will develop at these sites.
Unit 6: Production of Plantation Crops 6.59 CONCLUSION Cocoa is an important crop in many tropical countries where it provides a supplementary income for subsistence farmers and makes an important contribution to the national economy. The agronomy of cocoa is 'perhaps more complex than of most other crops. Variation in cocoa response is increased by wide genetic variation within as well as between varieties and by the complex interacting effects of shade on nutrition, growth and production. References Allen, J.B., and R.A. Lass. 1983. London cocoa trade Amazon project: final report phase 1.
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