Section II— Diseases of Permanent Crops 

 CHAPTER XVII 



DISEASES OF CACAO 



According to Humboldt the home of the cacao tree is the forest 

 of the basins of the Orinoco and the Amazon. The evergreen 

 habit, the large thin leaves, the ability to endure shade and the 

 intolerance shown towards wind are in accord with a moist forest 

 habitat though it would be quite unsafe to conclude on this 

 evidence that such a situation is necessary or even most advan- 

 tageous for the commercial production of cacao from the tree. 



When the factors which most directly affect cacao under 

 cultivation are distinguished it is seen that no single combina- 

 tion of them can be regarded as necessary for its well-being, for 

 within limits a deficiency in one may be compensated for by the 

 surplus of another. 



There can be no doubt that a rainfall regularly distributed 

 throughout the year best suits the vegetative habit of the tree 

 and leads to full and rapid development. But where frequent 

 rain is associated with cloudy weather without a dry and sunny 

 season the crop will usually be far less than in situations less 

 favourable to vegetative growth. On the other hand a cloudy 

 sky may be a great advantage when the rainfall is scanty. Any 

 prolonged dry period, unless the soil is particularly deep and 

 retentive, or very well protected, is highly unfavourable. 



Cacao is naturally a deep-rooted plant, and, in situations where 

 soil and subsoil permit this habit to be developed to the full, 

 it enables the tree to pass with little harm through a dry season 

 which would defoliate it in less favourable conditions. Deep 

 draining is thus clearly indicated, in order that full penetration 

 may not be hindered by subsoil waterlogged in the wet season. 

 Equally clear is the disadvantage of planting over impenetrable 

 subsoil where marked periods of dry weather are liable to occur. 

 In the absence of such periods cacao is grown in Surinam, accord- 

 ing to C. J. van Hall, in soil i| to 2 feet deep. In the coast 

 lands of Venezuela the dry season is tided over by irrigation. 

 While the main roots will penetrate great depths to get in 

 touch with subsoil water, the feeding roots are largely developed 

 in the soil proper. Under some circumstances a dense layer of 

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