DISEASES OF SUGAR CANE 289 



is rare, and the deficiencies encountered in different situations and 

 circumstances lead to wide diversities in agricultural practice. 



The primitive method of growing sugar-cane, still practised 

 where good forest soil is available, is to plant up the cleared land 

 and take off a long succession of ratoon crops, then perhaps letting 

 the land relapse for a time to bush. Sooner or later this method 

 has to be replaced by a more permanent system of agriculture, 

 with more frequent replanting, more careful cultivation, the 

 use of manures, and eventually the interposition of rotation crops 

 or fallow. The extent to which these measures have to be adopted 

 to get an average crop with average ability of management is a 

 measure of the general suitability of the conditions for cane 

 production. 



On good soils in Trinidad, where heavy dews and humid air 

 supplement the effects of the actual rainfall, it is still possible 

 in some places to pursue a system of continuous cropping and 

 long ratooning. The opposite extreme is reached in the arid sea- 

 board districts of Barbados, where plant canes only can be grown 

 and these have to be alternated every third or even in some cases 

 every second period with a rotation crop, in addition to the land 

 being thoroughly prepared well ahead of each planting season 

 and each crop heavily manured. 



Between these extremes there is a variety of practice, with a 

 general tendency in recent years to the further reduction of 

 ratoons, which is variously interpreted as the result of less efficient 

 cultivation owing to shortage and increased expense of labour, 

 the substitution of chemical for organic manures, and the demand 

 for increased tonnage under the system of central factories. 



It is more than usually necessary in the case of sugar-cane 

 that an understanding of agricultural practice should precede 

 the study of its diseases, for the manner in which any defect in 

 the adaptation of agricultural methods to conditions of soil and 

 climate finds expression is in the prevalence of the general condi- 

 tion known as root disease. It is thus permissible from one 

 point of view to regard all the modifications of practice referred 

 to above as measures for the avoidance of this condition. 



Excepting injuries of insect origin, root disease is at the 

 present time the only serious affection of sugar-cane in these 

 islands, and the effects of insect injury are often so entangled 

 with those of root disease that they cannot be studied apart. 



Root Disease : General Type. 



The Nature of Root Disease. 



In its application to sugar-cane the term root disease in its 

 general sense is an expression for the form which is taken by 

 failure due in the first instance to adverse conditions of soil, 

 climate, or insect infestation. It owes its recognition as a disease 



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