Section I -General Diseases 

 CHAPTER XV 



ROOT DISEASES 



RosELLiNiA Diseases 



In the West Indies as in other parts of the tropics where forest 

 land has been opened up to agriculture, destructive diseases 

 make their appearance as the result of infections arising from 

 native fungi which occur on buried roots, on logs, and on other 

 debris remaining from the forest. A number of different fungi are 

 responsible in various parts of the world for diseases arising in 

 this way but the characters of the affections produced are essen- 

 tially the same. 



In the West Indies the fungi concerned are mainly species of 

 Rosellinia. Other forms occur but are comparatively rare. In 

 cultivations of an open nature where sun and wind have access to 

 the soil, and especially in those of arable crops, there is a rapid 

 dissipation of the decaying material necessary for the develop- 

 ment of the fungus and the diseases as a rule soon disappear. 

 They can persist, however, in cultivations such as that of cacao 

 in which the conditions, especially where shade trees are abundant, 

 approach to those of the forest in respect of shade and humidity. 

 They also occur in windbreaks and hedges of certain susceptible 

 trees and shrubs in wet or sheltered districts. The causative 

 fungi infect shaded soil rich in decaying vegetable matter and 

 spread slowly through it, destroying every plant with which 

 they come in contact. 



The existence of such diseases is traditional in the West 

 Indies, and those under discussion have in all probability been 

 met with from the time of the first settlement. A description of 

 disease of this type occurring on coffee in the French Antilles was 

 published in Paris as early as 1842. The first account seen 

 having reference to the British West Indies is that by C. A. 

 Barber, in 1893, of root disease of cacao in Dominica, which 

 contains a list of twelve hosts observed. The disease has been 

 from time to time described by agricultural officers since the 

 formation of the Imperial Department of Agriculture. F. W. 

 South (1909-13) was the first to recognise the genus of the causa- 

 tive fungi. Five species have been met with by the present 

 writer, of which three have been found associated with root 

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