DISEASES AND ENEMIES 235 



respect the cocoa tree is not like the sugar-cane, for 

 instance, for the diseases which attack the latter are so 

 different in their manifestation that in many cases the 

 external symptoms alone enable the cause to be ascer- 

 tained. The cocoa diseases, however, generally need a 

 thorough investigation before a definite opinion can be 

 formed as to their real character. 



Koot and stem diseases of the cocoa are usually 

 indicated by a yellowish colour, followed by a more or 

 less general falling-off of the leaves. The way in which 

 this takes place may often enable the initiated patho- 

 logist to say whether the tree is attacked by canker, die- 

 back, stem-borers, root-fungus, or other stem or root 

 diseases, but closer investigation is almost always 

 necessary to decide this with certainty. It will there- 

 fore be best first to make a classification based upon the 

 different causes of the diseases : 



A (1). Diseases of the Root caused by Fungi. 



Only a few root diseases are known, and 

 these are not very important. 



In Java a fungus sometimes occurs which 

 covers the roots with a white mycelium, with 

 the result that the tree usually dies more or 

 less suddenly ......" White - root fungus " 



(Forties semitostus). 



In Samoa, New Guinea, Ceylon, and West 

 Africa, a dangerous root fungus has been 

 observed . . . . . . " Brown - root disease " 



(Hymenochaete noxia). 



In Kamerun a characteristic root fungus 

 was observed by von Faber . . . (Not yet identified.) 



In Trinidad and the other Antilles, and also 

 in Ceylon, root diseases have been observed (Not yet identified.) 



A (2). Diseases of the Root caused by Insects. 



In South America and the Antilles the 

 roots of young plants, especially at the point 

 of junction of stem and root, are not seldom 

 damaged by ...... The " mole cricket " 



(Scapteriscus didactylus). 



B (1). Diseases of the Stem and Branches caused by Fungi. 



A widely spread disease occurring in 

 America (Trinidad, Surinam, etc.), Africa 



