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The Supplement to the Tropical Agriculturist 



where the tree has healed itself, that is, where 

 the cankered bark is scaling off, all scales of 

 dead bark should be shelled out. The fungus in 

 those scales is dead, but there may be resting 

 spores there, and I have seen cases in which the 

 disease has commenced again under the old 

 scale. Of course, that may have been a rein- 

 fection ; water lodges behind these scales, and 

 in that way they form admirable points of attack 

 for the fungus. It is often necessary to cut 

 away any healthy bark in such cases; the scales 

 shell out, and that removes all the dead diseased 

 tissue. It would be well to paint the wounds 

 with Bordeaux mixture, made according to the 

 usual formula. If the wound does not extend 

 to the wood, there is no necessity to cover it 

 with anything : the tree very soon forms a 

 protective layer of cork over it. If the wood 

 is exposed, the wound should be covered with 

 cowdung and clay. Very large wounds should 

 bo tarred in the middle, and plastered wi'th 

 cowdung and clay round the edges. We are 

 badly in need of some protective [Which can be 

 applied to exposed wood without injury to the 

 surrounding healthy bark. Tar undoubtedly 

 kills the surrounding bark and to some extent 

 retards healing ; consequently, I do not think 

 it can bo safely applied to small exposures on 

 the tapping surface. There appears to be some 

 hope of success with the sediment from Bor- 

 deaux mixture, made adhesive by means of a 

 resin compound. At present, 1 should advise 

 painting small wounds with Bordeaux mixture, 

 and then covering with cowdung and clay. 

 When the wood has begun to decay it is often 

 difficult to keep out boring beetles. Some 

 flowers of sulphur mixed with the cowdungaud 

 clay will prevent their attack to some extent. 

 Some planters have used kerosone or bulk cil 

 for that purpose, but my experience is that 

 all oily subtances soak into healthy Hevea 

 bark and kill it. The treatment described 



MUST BE ADOPTED IN ALL OASE3 OF OANKEU. 



The only other point is whether anything can 

 be done to prevent the attacks of the fungus. 

 The fungus attacks the fruit, and may be ex- 

 pected to do so every wet year. It is impracti- 

 cable to treat the fruit ; but after a serious 

 outbreak of the fruit disease, fallen fruit should 

 be collected and burnt. It is rather a mat- 

 ter for congratulation that tapping, so far 

 as the evidence goes, reduces the number 

 of fruits. Some years ago a planter patented 

 a latex protector, intended to prevent rain 

 water falling into the cup?. More recently 

 a rain gutter has been brought out, to 



prevent the rain water running over the tapped 

 surface. The patentee of the latter claims that 

 he can continue the tapping through the wet 

 weather and obtain more rubber per annum. Ite 

 chief recommendation from the present point of 

 view is that it stops the constant flow of water 

 down the stem from the crown, and in that way 

 may prevent decay on the tapped surface, and 

 canker. The germination of any fungus spore 

 depends upon the presence of moisture, but in 

 the case of Phytophthora is especially necessary 

 that the sporangium should fall on a wet sur- 

 face. If the 6tem could be kept dry, there 

 would be practically no canker. Of course, I 

 know that it is impossible to keep the stem dry, 

 owing to the lateral drive of the rain, but these 

 rain gutters would keep off some of the water. 

 I am strongly of opinion that it would be worth 

 while to experiment with these on a fairly large 

 area. I have already 



INSTITUTED SPKAYING EXPERIMENTS 



with Bordeaux mixture. Our chief aim should 

 be to protect the potential tapping area from 

 canker, because the wounds made in excising 

 diseased bark interfere with future tapping 

 operations ; and the best method of protection 

 would be to spray the stem in the dry weather 

 just before the monsoon to a height of six or 

 eight feet. I recommended that to South Indian 

 planters for several years as a preventive of "Pink 

 Disease," and it has now been carried out at a 

 small cost. There is no doubt of its efficacy 

 against any fungus which attacks the tree above 

 ground: the only qrrescion is whether it will 

 have any effect on the rubber through traces of 

 copper compounds washing into the latex. Ex- 

 periments have been begun to decide that point. 

 Bordeaux mixture dries on the tree, and the 

 copper compounds, which are gradually dis- 

 solved by the rain, kill the fungus sporos which 

 may alight on it. The amount of copper on the 

 tree is very small, and the quantity brought 

 into solution at any given time is infinitesimal. 

 Hence it would seem improbable that any ap- 

 preciable quantity would get into the latex. 

 Rough barked trees appear to be attacked by 

 canker more than those with a smooth bark, and 

 the deposit of Bordeaux mixture in the cracks 

 would be an effectual preventitive. Spraying 

 does not increase the proportion of scrap, nor 

 does it stain the rubber, but I must wait until 

 the rubber has been analysed before deciding 

 whether it can be unreservedly recommended. 

 In case spraying can be recommended, the fol- 

 lowing details may be given now. Solutions con- 

 taining copper compounds must be made in 

 wooden vessels. Only a few weeks ago I came 



