and Magazine of the Ceylon Agricultural Society. 



377 



NEW DISEASES OF RUBBER. 



Addrbss by the Government Mycologist : 

 Before the Kelani Valley Planters' 

 As sociatio n. 



The Chairman: — Gentlemen, I have now the 

 greatest pleasure in introducing MrPetch, who has 

 kindly consented to come down and give a lecture 

 on diseases of rubber trees. (Loud applause.) 



After a short interval for refreshments, Mr 

 Petch began his lecture, during which quite a 

 number of specimens of stem and root diseases 

 were exhibited. and the diseases explained. 



Mr T Petch — addressing the meeting, said : 

 — Mr Chairman, and gentlemen,— I think the 

 Secretary has sent round a circular, the latest 

 one, on Hevea disease, "pink disease," of which 

 you have got so many specimens in this room. It 

 is distinguished by a pink coating on the outside 

 of the bark. Whenitisthereitkillsthe bark and 

 ruins your tree. It becomes yellowish when 

 old. That disease was called the "writing fungus" 

 in the Straits because it breaks up into fragments 

 like Sanskrit or something of that sort. If it is wet, 

 it may be whiter than this ; it is fairly pink here, 

 but it is nearly white on this side. (Specimen 

 shown.) If you have any doubt when you see 

 what you think is the fungus on your tree cut 

 out the bark and send it for report. 



Mr Scott :— Does it kill the tree ? 



Mr Petch :— It kills the bark of the tree; but 

 if it rings the tree far enough, 



then the tree dies. 

 If it comes on one side, it will not kill the tree. 

 There is another case here (specimen shown) 

 where it developed on one side of the branch. 

 The other lateral branch is not dead, but above 

 it it has died oft'. You will find the "pink dis- 

 ease " here below. Here is another specimen. 

 It usually starts near the top of the tree so that 

 if you cut off the diseased top the tree will go on 

 growing. But in this case the disease has been 

 allowed to come down the tree. This part below 

 is quite sound. So that if you cut off there, you 

 will save the rest of the tree which will sprout 

 from below. 



Mr. Bontor :— Is that the same disease you 

 referred to before? 



Mr. Petch :— Yes. The easiest name to re- 

 member it by is "pink disease," because there is 

 a pink colour outside. The only additional fact 

 beyond what has appeared in the circular is that 



the disease will grow on crotalaria. 

 If you plant up Crotalaria in Rubber and let it 

 grow for a year, or a year-and-a-half, you will 

 then get more of the pink disease on the Crot- 

 alaria than you would get it on your Rubber. 

 In fact, your Crotalaria will serve as a source of 

 disease for your Rubber. They are finding that 

 out in South India, where they planted their 

 plantations with Crotalaria and let it grow for 

 nine months before it flowered and got a fairly 

 good stem like this (shown.) The whole of the 

 stem gets attacked in the South West Monsoon 

 with this disease and from that Crotalaria it 

 spreads to the rubber. In some places in South 

 India they have Rubber two years old in the 

 field and as soon as it is of that age it is attacked 

 by the "pink disease." In some of their fields 

 at present they cannot get a stora more than 

 two years old. 



Mr Duncan :— Do you get it from the jungle F 

 Mr Petch :— You will find most of the spores 

 blown out of the jungle. The disease flourishes 

 most in wet weather, and during that time the 

 spores are blown out from the jungle and infect 

 your trees. Now we will leave that disease and 

 go on to the next, about which nothing has 

 been written yet— the chief disease which is 

 awaiting a circular, which we hope to get out 

 in a week or two, and that is what is known as 



THE "DIE BACK" DISEASE. 



The trees usually attacked are about two years 

 old but this year it is found on trees from four 

 to nine years of age. The name supplies you 

 with the nature of the disease — the branches 

 attacked "die back" from the top shoot and 

 the disease works itself down to the base. Un- 

 fortunately that does not distinguish it from 

 anything else. Your leading shoot may die back 

 from many causes apart from the disease, as 

 for instance, wind, damage by rain, shade, or 

 over-tapping. If you get the root disease, too, the 

 tree dies back. The chief feature in the "die 

 back" disease is that the top shoot dies back while 

 the rest of the tree is green. In the case of 

 root disease generally the tree dies back all 

 through at the same time. Then in the case of 

 leaf disease generally the leaves fall all over the 

 tree ; but in the case of the "die back" disease 

 you get it from the top shoot which gradually 

 dies off — and if it is not cut off, and the disease 

 checked, the dying off process continues and the 

 section just below succumbs next. If you cut it 

 off below, the rest of the tree will flourish, but 

 if you neglect to do so the tree will further die 

 back till the disease reaches the base and the 

 tree is killed out-right. (Position demonstrated 

 on black-board.) You have practically to watch 

 it going on. Of course 



YOU CAN CUT IT OFF 



if you see the top shoot attacked. Here we have 

 an example (shown) where the tree has died 

 back to a certain stage below which you get 

 fresh shoots. Here is another case where the 

 disease has gone right down the stem to the 

 base, while three branches at the top are green. 

 The disease may come straight down the stem 

 and leave some branches near the top green. In 

 this case it is dead low. You can get the whole tree 

 killed in a month. (Laughter and cries of "Oh oh.") 

 You may confuse it with root disease or general leaf 

 fall, but in those cases the tree will not be green, 

 while in the case of the pink disease referred to, it 

 will show itself in colour. It is a simple thing to 

 determine. Remove the earth from the baseofthe 

 tree and you will see, if the top dies and you 

 are not sure, whether it is the root disease." If 

 any fresh shoots arise it is "die back" disease, but 

 if they do not, it is root disease. If you lop 

 off the trees that die back they will thrive with- 

 out any ill eftect. This is the first stage, the 

 beginning of the " die back " (specimen shown). 

 The shoot turns brown and soft ; and here, a 

 later stage, it becomes hard and grey. Ihe fun- 

 gus, however, does not attack the stem in 

 which the wood is already formed. But after the 

 death of the leading shoot another fungus 

 secures a footing and carries on the destruction 

 right to the base of the tree, and the tree is 

 killed off. The 



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