DISEASES 165 



Canker 



(Phytophthora faberi.) 



This parasite attacks both Hevea and Cocoa, 

 causing injury to the stem and the pods in both 

 instances. The fungus itself cannot be seen with- 

 out the aid of a microscope. The external symp- 

 toms of its presence are not very obvious in Hevea. 

 The ordinary indications of a canker are absent, 

 the bark not being rough or cracked in any way. 

 In fact, Fetch states that a tree may be killed and 

 all its bark decayed without showing any rough- 

 ness or open wounds. The same author states that 

 a sudden stoppage in the yield of latex often 

 suggests the disease. Under these circumstances, 

 if, when the outer layer of brown bark is scraped 

 off, a black layer is seen, and the cortex below this 

 is found to be discoloured, the presence of the 

 disease may be taken as fully established. 

 Diseased patches of bark should be removed at 

 once, and the exposed wood protected by a coat of 

 gas-tar, care being taken that the tar does not 

 spread over the living bark. The fruit is also 

 attacked, the symptoms being a water-logged, 



