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obtain any material to work on for all the affected trees had been 
subjected to treatment. In February again, through the kind 
permission of the manager, I was able to visit another estate 
200 miles away from the first where apparently a disease of a similar 
nature had occurred. Sharpies, the Government Mycologist, was 
visiting this estate and he isolated the fungus Phytophthora from 
the diseased bark. Within a day or two I visited an estate which it 
is my privilege to visit regularly and there found a considerable 
number of trees with this same disease. I have now isolated the 
fungus from material collected. From evidence collected it appears 
that the fungus is not Phytophthora Faberi. but another species of 
the same genus. 
The disease is undoubtedly the same as that known as “ bark 
rot ” in Ceylon, “ black thread disease of Hevea” in Burma, and one 
form of canker (vertical black line) in Java. Infection only takes 
place on the most recently tapped sux*face and, therefore, the fungus 
appears to be a wound parasite. Essentially the disease is a decay 
of the tapped surface. The most recently tapped bark immediately 
above the tapping cut shows vertical black lines varying in 
length up to one inch or more, and these on removal of the bark 
are shown to continue into the wood. This “ bark rot ” may spread 
and several “lines” of decay may coalesce to form small 
blackened or sometimes greyish, roughly rectangular areas of dead 
bark. Further, as the fungus develops several areas may coalesce, 
producing a decayed area of bark just above the tapping cut and 
right across the tapped area. Superficially the lines often appear 
as slits or vertical depressions some little distance above the tapping 
cut, but frequently, at an early stage, the lines may only be 
discovered by removing the thin outer-layer. As Dastur has pointed 
out the depressions may be due to the collapse of the cell walls of 
the outer tissues. Rutgers in Java, Dastur in Burma, and Macrae in 
India have proved that the decay of the tapped surface or “ bark rot ” 
is due to an infection of Phytophthora. That a species of this 
fungus is the actual cause of the decay is beyond all doubt since 
these three independent workers obtained positive results by infection 
experiments. That work has also been done in this country by 
Messrs. Belgrave and Norris in the Agricultural Department. 
In Ceylon, Petch has shown that there are four diff extent diseases 
caused by Phytophthora Faberi— namely, stem canker, “ bark rot ” of 
the tapping surface, abnormal leaf fall and pod disease, but recent 
evidence goes to show that more than one species of Phytophthora 
is responsible for these diseases. 
Until January last I had not seen any sign of a disease caused 
by Phytophthora on any of the estates 1 visit regularly but I am 
inclined to think that the “ bark rot ” of the tapping sxirface is now 
extremely common in the country. 
