188 DISEASES OF TROPICAL PLANTS OH. 



These mycelial threads are variously coloured, and run 

 over the branches and stems. They are closely appressed 

 to the bark, and sometimes spread over the leaves, 

 forming a delicate web-work. They penetrate the host 

 and cause the death of the leaves and buds. These 

 diseases have been reported on cacao from Trinidad, 

 Dominica, Tobago, and British Guiana, and on tea and 

 nutmeg in Ceylon. The writer has seen the same or a 

 similar disease on other hosts in Cuba, but not on the 

 cacao. 1 It is most severe in damp, shady places, and 

 should be treated in the same manner as the pink 

 disease. 



Another blight, which is said to be due to an unde- 

 termined species of Crepidotus, has been reported from 

 some localities. The writer has been unable to find 

 any very satisfactory information concerning it, other 

 than that the fully developed stage can be found on 

 twigs which have fallen and commenced to decay. 



Black Rot. This disease is caused by the fungus 

 Phytophtliora faberi? Maub, a species which is very 

 closely related to the P. infestans, the cause of late 

 blight of the potato in the north temperate zone. The 

 pod darkens, beginning at the end, and then becomes 

 covered with a white mycelium which carries the 

 conidiophores and resembles a mould. It completely 

 destroys both rind and seed. In its last stages the 

 fruit may fall and rot. or may harden and hang on the 

 tree for a long time. The oospores are produced 

 abundantly in the decaying parts, and are released by 

 the decay. It is much more severe in shady, damp 

 places. This fungus is also common on the seedlings. 



This disease occurs on the cacao in Trinidad, 

 Philippines, Samoa, Kamerun, Java, St. Lucia, British 

 Guiana, Surinam, Martinique, Barbadoes, and Ceylon, 

 and probably has a very much wider range. 



The soil should be well drained, and the shade 



1 A cacao blight has been reported from the Philippines, but the writer 

 cannot say whether it is or is not the same. 



2 Rorer believes that this fungus is also the cause of a stem canker of the 

 cacao. 



