DISEASES OFl^BANANA 



251 



of these diseases as it is quite probable that they will be met with 

 sooner or later. 



Black Spot of Leaves. 



This leaf disease has been reported from several localities 

 in Jamaica, where it is confined to good soils containing a high 

 proportion of marl. It begins with tiny black spots on the 

 main veins of the leaf-blade, which increase in size and become 



Fig. 96 



Cercospora Musarum 



Bull. 6, Dept. Agri., Jamaica 



lenticular and are then often surrounded by a narrow bright 

 yellow border. As the disease advances dry pale brown areas 

 extend from the largest spots fanwise to the edge of the blade. 

 Later the patches so formed unite and may give rise to a broad 

 zone of dry tissue extending round the outer half of the blade. 

 No fungus has been found in very young spots, but in the later 

 stages hyphae are found in the tissue round them and the coni- 

 diophores of a Cercospora break through the epidermis in large 

 numbers. This fungus regularly accompanies the black spot 

 disease in its occurrence on healthy dark-green leaves and has 



