62 Pink Disease of Plantation Rubber 



thrown off, but the fungus sometimes develops again over the bark 

 which began to close the wound. Where the cankered areas have 

 entirely thrown oft the disease, the region around them is frequently 

 blackened on account of oxidation of the rubber exuded when the 

 disease was active. 



Investigation of Hevea wood affected by Corticium salmonicolor. 



Before the appearance of Rant's paper (10), Petch (9) stated that 

 Corticium salmonicolor does not enter the wood to any appreciable 

 extent. Rant noticed in cinchona that the fungus invaded the wood 

 and the pith. 



Branches of Hevea brasiliensis attacked by Pink Disease die in 

 a manner characteristic of those attacked by a fungus which grows 

 vigorously in the wood. Young branches are more often affected in 

 this manner than are old ones. The rapid death of the leaves in such 

 branches is a sure sign that the water supply is checked ; this restriction 

 is probably due to the activities of the fungus in the wood. It soon 

 became clear that the fungus entered the wood of such branches, so a 

 detailed investigation of the manner in which it invaded these tissues 

 was made. Wood affected by Corticium salmonicolor is only slightly 

 discoloured and differs greatly in this respect from wood permeated by 

 Diplodia cacaoicola. 



During the early part of 1914 a large branch of a - rubber tree attacked 

 by Pink Disease was obtained from an estate in Negri Sembilan in which 

 the transition between healthy and diseased wood could be clearly 

 t raced. The branch was covered with the pink incrustation which ran 

 out below into the cobweb-like form of the fungus. The cortical layers 

 were dead and could be easily stripped oft' exposing the wood beneath. 



When split longitudinally, the wood was seen to be sound for about 

 two feet from the top of the branch, but the part below was dry and 

 obviously diseased, except for a length of about nine inches which 

 ma iked the transition between the healthy and diseased wood. This 

 transition region had a moist, almost transparent, appearance and 

 gradually passed below into tin' dry, diseased wood and above into 

 the moist, heall hy wood. 



Diplodia cacaoicola. I\ Hennings, is a common wound parasite of 

 Hevea brasiliensis and lias been found in some branches attacked by 

 Pink Disease. A careful search for Diplodia vavaoicoUt was therefore 

 made before investigating the mode of attack of Corticium salrnonicolor. 

 No externa] sign of Diplodia was observed and microscopical examination 



