i88 RUBBER AND 



eruptive outgrowth such as is usually associated with 

 the name of canker. The disease consists in a softening 

 and rotting of the inner layers of bark, which may 

 be scarcely visible from the exterior, or may betray its 

 presence by the oozing out of a dark red liquid. The 

 softened and discoloured area is occupied by the hyphae 

 of the destructive fungus. The rotting bark may soon 

 become the breeding ground for other fungi, but the 

 Phytophthora is the primary cause of the mischief. On 

 shaving off the outer layers of bark with a sharp knife, 

 the diseased area becomes recognisable as a brownish or 

 claret coloured patch, with well defined edges separating 

 it from the surrounding healthy bark. 



The only remedy is excision. If the disease is dis- 

 covered whilst the patch is still small, the whole of the 

 diseased tissue can be cut away. The healthy bark 

 should be trimmed all round the exposed area of wood 

 with a very clean cut, and if much wood is exposed the 

 latter should be tarred. In the course of time the bark 

 will heal over the wounded area and the tree will 

 recover. The disease is specially serious, owing to the 

 fact that it generally attacks the lower part of the trunk 

 where tapping is in progress. Tapping must therefore 

 be suspended until the recovery of the tree is well 

 advanced. In cases where the disease has already 

 spread far round the circumference, it is better to cut 

 down the tree at once. Any diseased portions cut away, 

 and, in the case of felling, the whole tree, should always 

 be destroyed by fire. 



