248 COCOA CHAP. 



prevalent in the rainy season. A moist soil and stand- 

 ing water should therefore be avoided by efficient 

 drainage, and the humidity in the fields should be 

 reduced by thinning out where the trees are planted 

 closely, by pruning where the foliage system is too 

 dense, and by removing as much of the shade as seems 

 necessary. 



The direct treatment of the trees by excising the 

 affected parts has great drawbacks ; the trees generally 

 suffer considerably, and the remedy is not completely 

 effective. Shaving off the bark superficially is more to 

 be recommended ; when this treatment has been applied, 

 the spot generally dries out quickly and the fungus 

 dies. Experiments are now being made in treating the 

 diseased parts with a disinfectant, but satisfactory results 

 have not yet been obtained. 



Finally, it must be remembered that the canker 

 spots are in some countries favourite places for the 

 attacks of insects, e.g. the " bubuk " beetle (Xyleborus) 

 in Java. If treatment with a disinfectant be successful, 

 the effect must be not only to kill the fungus and stop 

 its further growth, but also to make the dead bark 

 poisonous to the insects in question. 



Wounds also favour the development of canker, 

 especially those made by borers. In order to get rid 

 of canker, therefore, it is also necessary to fight the 

 borers and to close the wounds by a layer of tar. 



Die-back disease. "Die-back disease" (caused by 

 a fungus, Diplodia cacaoicola] is probably very widely 

 spread throughout the cocoa -growing world. It has 

 been observed in the Antilles (Trinidad, St. Vincent, 

 Grenada, St. Lucia, Dominica), Guiana (Surinam, 

 Demerara), Kamerun, Ceylon ; probably in Samoa ; and 

 perhaps also in Java and Ecuador. 



When trees are attacked by this fungus, the leaves 

 become yellow and fall off, with the result that the tree 

 is completely defoliated before it dies. The disease 

 generally begins at the extremity of a branch, attacking 

 twigs which have been weakened by some cause or 



