Correspondence. 



412 



[June 1907. 



complains. He thoroughly agreed with me on this point, and considered it worth 

 while for Ceylon planters to make an experimental shipping of rubber which had 

 not been exposed to strong sunlight before being shipped, and had practically no 

 cleaning at all. He would be very glad to receive and report on ?.ny sent him, and I 

 should strongly suggest that somebody should take this up. 



Yours faithfully. 

 WALTER COURTNEY, 

 Ceylon Tea Commissioner, U.S. America. 



CANKER IN PARA RUBBER TREES. 



Upcountry, April 27th. 

 Dear Sir,—" A stitch in time saves nine," and I would sound a note of 

 warning, as recent experience points to the possibility of canker, or bark -disease, 

 being carried from one tree to another by the medium of the tapping-knife, and 

 would suggest that the knife be disinfected after operation on each tree in cankered 

 or suspicious areas. This could be easily done by the tapper carrying a bow-handled 

 can of water in which to cleanse the knife, and within it a smaller can of some 

 disinfecting fluid into which to dip the knife when clean. Happily, bark-disease 

 is not very prevalent yet in our Para rubber trees, and so far it does not seem to 

 have the virulent effect on the vitality of the tree that Cinchona canker had, but 

 it effectually stops tapping operations in the infected bark area for many months, 

 till the under renewal of bark grows thick enough to cut a channel in. And as 

 individual cankered trees may be found on almost any rubber estate, there would 

 seem to be danger of inoculating many healthy trees from these solitary ones. 

 More than that : tapping seems to increase the virulence and spread of the disease 

 over the bark of trees already infected. Some months ago a friend took me to a 

 small isolated group of Para trees which were all more or less suffering from canker. 

 He had been tapping these for some time, and about one inch of excision had been 

 got through on the tapping lines. He had observed that the canker began on one 

 particular tree which had previously been severely bark-damaged by cooly children, 

 and that for some unsuspected reason had spread to the other trees in the group. 

 The tapping had been done in thin parings very carefully with but few cambium 

 injuries, and these only over the warts ; but at this time tapping had been stopped 

 a few weeks. In no instance had the canker taken hold at the point of cambium 

 injury. In some cases the canker had spread right up to the tapping line and 

 there stopped short, the bark above it being quite sound and full of latex. In 

 others it had spread down to the renewed bark and there stopped, the bark below 

 the last cut being also quite sound. When we picked off the diseased bark in dry 

 plates or scales it was found that renewal was taking place healthily on the inner or 

 laticiferous bark, through which the disease had not apparently gone. We drew 

 the deduction that the obvious way to treat the cankered area would be to cut a 

 channel right round it and clear of it and down to the laticiferous inner cortex, 

 and treat the enclosed area by excision and disinfectants. I would respectfully 

 invite the Government Mycologist's criticism of the above and his advice to rubber 

 planters in general on the subject, and ask for information on the following 

 points :— 



(1) Is the laticiferous or inner bark of the Para tree immune from canker ? 

 (It does not seem to be the case with Ceara, for the tapping knife occasionally shows 

 up an infected area, especially near the base of the tree, with the whole of the 

 inner bark down to the cambium brown and disintegrated, under apparently 

 healthy " cherry" or outer bark.) 



