51 
Bark canker. — The fungus causing this disease appears to be 
Phytophthora Faberi ; there being then two distinct forms of disease 
apparently caused by different species of the same genus. The 
fungus was known to cause a canker on Hevea as long ago as 
1903 in Ceylon. In this country, however, as far as I am aware the 
disease has only recently been found. 
Certainly on estates I visit I had not been able to attribute any 
pathological condition to the fungus Phytophthora until March of 
this year. The disease starts in patches usually on or near the 
tapped bark but they may appear at a higher level. It is possible 
that the first indication may be that the tree ceases to yield latex. 
If undiscovered at an early stage the decaying tissue will attract 
borers and the appearance of boring beetles may be the first visible 
sign. In all cases when latex ceases to flow the bark should be 
lightly scraped ; if a green layer is found the tree is healthy. 
Sometimes, in the case of trees with a very scaly outer bark, the 
green layer is not very obvious. If the tree is attacked by the 
fungus Phytophthora. Faberi a black layer is found on lightly scraping 
and the cortex beueath is variously coloured, greyish, brown or dirty 
red or purple red according to the stage in the attack, i.e., it may be 
greyish in the early stage or may be very dirty red which changes 
to purple red on exposure in advanced cases. 
The diseased patch usually has a well-defined dark border. 
No latex will flow from patches of cankered bark but surrounding 
bark may yield extraordinary quantities. It must be understood 
that the colour of the bark only applies to the internal layers of 
bark and that it can only be detected by scraping away outer layers. 
Usually there is no external indication of the disease. The disease 
is capable of spreading and may kill the whole bark from the point 
of attack to the position of origin of first branches or higher or all 
the bark of the main stem. Boring beetles are attracted by a 
peculiar smell, which appears to be characteristic of the cankered 
bark, and they may possibly cause more injury than the canker itself. 
Treatment. — The red canker patches of bark canker must be 
excised or scraped if patches can be found where the disease has not 
affected the inner tissue to the cambium and the wounds so caused 
painted with a 20 per cent, solution of brunolinum in water and soft 
soap and later covered with coal tax*. It is useless trying to apply 
any form of treatment in the case of badly affected trees where 
boxing beetles have made their entiy into the wood. These ti’ees 
should be cut out and burnt. 
As regards the treatment of “ black thread disease 15 or the 
“bark rot” of the tapping surface I will here indicate methods 
advised by other economic mycologists in various countries. 
Rutgers and Ai*ens in Java suggest that “ tapping be stopped 
and the cuts treated every five days with a 20 per cent, solution of 
