106 DISEASES AND THEIR CURE 



less regular in shape, occur scattered about the 

 surface. " These spots more frequently appear 

 first on the under sides of the leaves," says the 

 authority already quoted, " they extend in area, 

 and often run into another forming irregular 

 blotches. As they increase in size, they change from 

 a yellowish colour to a greyish-white in the centre, 

 and are bordered by a distinct margin, usually a 

 deep greenish-brown colour. Finally, small greyish- 

 black pustules are seen in the grey parts of the 

 spots on the upper surface of the leaves. These are 

 the fructifications of the causative fungus. When 

 a large number of spots have collected on a leaf, 

 it assumes a yellowish appearance and becomes 

 grey and withered. It may remain hanging on 

 the tree for some time, but it finally drops. As a 

 result of the diseased condition of the leaves, the 

 number of nuts borne on consecutive flower stalks 

 diminishes and finally no flowers are set. In very 

 bad cases, the terminal bud is left standing alone 

 and eventually this falls over and the tree dies." 



The remedial measures are : 



1. The destruction of the spores of the fungus to 

 prevent its spread. This is effected by cutting away 

 and burning all the outer, badly -attacked leaves, 

 while all dead trees are destroyed. When the attack 

 is severe it may become necessary to spray the 

 infected trees, and even adjacent healthy trees, 

 with Bordeaux mixture or some other fungicide. 



