DISEASES AND PESTS 41 



death of diseased trees does not take place so rapidly," 

 taking nine to twelve months. 



It would appear probable that the disease may spread : 



(1) By mycelium through the soil from root to root. 



(2) By spores blown from tree to tree. 



(3) By germinating tubes of spores from petioles attacking 

 either the roots of the same tree or the roots of another. 



(4) By germinating " chlamydospores " from decaying 

 petioles. 



There are six principal ways in which we may hope to 

 attack this disease. They are : 



(1) Destruction of all diseased material. 



(2) Isolation of diseased areas (by a trench 30-45 centi- 

 metres deep). 



(3) Besting of infested land before planting " supplies." 



(4) Spraying and application of chemicals. 



(5) Improved cultivation and drainage. 



(6) Searching for and propagating disease-resistant varieties. 



The first of these ways is the most important. If 

 chemicals are to be used, unslaked lime is recommended 

 for the soil and Bordeaux mixture for the leaves. 



While it has not been found possible positively to 

 identify the fungus on the roots in Trinidad, a fungus 

 infesting the roots in Travancore has been cultivated 

 by Butler, and found to develop as a Botryodiplodia. 

 It is highly probable, but not certain, that this is the 

 same fungus which causes the root disease in Trinidad. 



The disease has long been known in Travancore, 

 but has only of late years been recognized as the cause 

 of great damage. 



Very recently Hart has inoculated a healthy cacao 

 pod with the Botryodiplodia from coco-nut petioles, 

 and produced all the symptoms of the " brown rot " of 

 the cacao. The fungus growing on this infection differs 

 from Diplodia cacaoicola, the specific cause of the 

 brown rot, only in having slightly larger spores. It is 

 not yet possible to state positively that the brown rot 

 of cacao is identical with the coco-nut disease. But it 

 is certain that they are very nearly related, and that in 

 at least one direction an infection may pass from one 



