January i, 1904] 



THE INDIA RUBBER WORLD 



109 



THE RUBBER TREE DISEASE IN CEYLON. 



THE question of the canker fungus in rubber {Hevea) was 

 discussed at a special meeting of the Kalutara Planters' 

 Association, at Tebuwana, in Ceylon, on October 31, 

 which was addressed by Mr. J. B.Carruthers, the govern- 

 ment mycologist, who for some months had been making a 

 study of the subject. The details which follow are derived 

 from The Times of Ceylon. 



This disease in rubber trees in Ceylon was first discovered 

 two years ago by a forestry official. During last summer speci- 

 mens cut from rubber trees were sent to Mr. Carruthers from 

 several districts, in some of which he found the nectria or canker 

 fungus. The specimens contained mycelium, and on investiga- 

 tion by means of cultures, Mr. Carruthers found spores belong- 

 ing to a species of nectria. Inoculations were then made on 

 trees, this being the only way to prove the guilt of an individ- 

 ual parasitic fungus as the cause of any disease. Nectria grow 

 on apple trees, cacao, tea, etc., and eventually affect and kill 

 many kinds of trees. 



After preliminary investigations at the botanic garden at 

 Peradeniya, Mr. Carruthers visited fifteen or more estates — 

 practically all the rubber plantations of any size — in the Kalu- 

 tara district, with the result that it is estimated that about one 

 tree in every 200 is affected. On the other side of the river, 

 about 40 per cent, of the rubber trees on the Yatiporua estate 

 and 20 per cent, of those on the Edengoda estate are affected. 

 The canker has existed on these two estates for five years or 

 more. The address of Mr. Carruthers ran, in part : 



" Coming now to observe the aspect of the disease on trees, 

 as a general rule the external appearances on the rubber tree 

 are roughened and swollen places in the stem and branches. 

 These, on cutting off the outer bark, show discolored tissue, at 

 first a neutral tint color, and afterwards brownish andclaret 

 color. When shaved the whole of the diseased parts are 

 shown up like an outline colored map in the lighter colored 

 healthy tissue. When the canker fungus has been growing in 

 such a spot for some time— I cannot definitely say how long, as 

 this depends on physiological conditions — the fruits are pro- 

 duced, at first pink or whitish spores, and later round red fruits 

 like cayenne pepper, which look, on examination under a mag- 

 nifying lens, like crystallized strawberries. The structure of 

 these red fruits is the means of identifying the fungus as a 

 nectria. The canker spreads through the agency of the wind 

 in dry weather, by water, and by insects such as red ants which 

 carry the spores on their legs and bodies in travels over the 

 trees. The only conditions necessary for spores to grow are 

 damp and moisture, both of which Kalutara always has. 



" As regards the general health of rubber in the district, it is 

 good — very good, notwithstanding the dropping of leaves, dry- 

 ing back of young branches, and irregular deciduity in certain 

 rubber trees. The preventive methods I would recommend are 

 inspection by gangs of coolies, cutting out the canker, and the 

 entire excision of affected portions, and the burning of all bark 

 cut off and dead branches. The burning of dead branches is a 

 most important matter. Personally speaking, I believe — though 

 I am perhaps rather rash to speak on this matter to planters 

 who have practical experience of these things — the best way to 

 tackle a disease like this is not only to look out for this nectria 

 canker disease, but to observe any and all diseases that may 

 arise. With regard to the cultivation of rubber — as also in the 

 case of other products — a regular inspection should be made 



during a considerable time of the year, so that the moment 

 anything unusual is noticed in the way of disease it can be 

 treated by simple means at the initial stage. 



" As regards the time of the year for observing the disease, I 

 think dry weather is the best. You can see it better and also 

 observe the effect of the same. The disease is better seen in 

 dry weather; it is much more easy to spot then than in wet 

 weather. If you cut out a portion of your tree when the 

 weather is damp and moist and leave a small portion of the 

 disease in the area cut out, the fungus will struggle on and re- 

 gain a foothold, but if you did that in dry weather it would 

 completely drive out the fungus. So that there are two rea- 

 sons to show that dry weather is the best for observing and 

 for dealing with the disease. 



'• With regard to the applying of mixtures on diseased parts, 

 there is no doubt that theoretically and practically it is sound, 

 but I have reasons for not recommending this. In my expe- 

 rience the farmers in England and planters out here very often, 

 if any wash is recommended, show a tendency not to carefully 

 cut out any portion of the diseased bark, but to simply smear 

 the bark with the mixture in a general sort of way, and the na- 

 tural result is that the fungus goes on in its fell work under the 

 wash, so that the treatment is of no avail. If you cut out the 

 diseased portion of the bark and smear the wound with blue- 

 stone, the result would be advantageous, that is, if there is no 

 slovenly work done with regard to rubber disease— as in the 

 case of cacao cultivation. The Tamil cooly can be shown in a 

 very short space of time how to spot the diseased trees. When 

 it comes to cutting off portions of the bark in the trunk or 

 branches there should be no hesitation. The whole of the af- 

 fected portion is full of the mycelium of the fungus and will not 

 produce latex, so that you are not damaging your tree to any 

 extent by cutting off such portion as is affected. After opera- 

 tion on the affected portion the tree will go on as usual. The 

 rubber tree, gentlemen, has a wonderful power of growing and 

 producing new tissues. 



"Too much importance cannot be attached to this gang in- 

 spection. Whenever the bark of the tree is rough, and has a 

 larger corky layer than the average bark, I find that where you 

 scrape the bark there is no disadvantage to the living tissues 

 of the tree, and it seems probable that they are even stimulated 

 by this treatment and the amount of latex increased. With re- 

 gard to the production of an abnormal or corky bark it would 

 be well to groom it and see whether there is any unhealthy tissue 

 right behind. There is one thing that I ought to have touched 

 on, viz., with regard to the scare raised by people which your 

 chairman has referred to; and in this connection some people 

 seem to be scared on observing rubber trees in some places 

 dropping their leaves. 



" This dropping of leaves, and even branches, I think is due 

 to climatic or unforseen reasons. During the short time I was 

 in this district I saw trees which had previously dropped their 

 leaves and had dead branches on them recovering, producing 

 buds, and pushing on, and I am quite certain that this nectria 

 fungus was not responsible for the abnormal dropping of leaf 

 and drying of certain branches. This is a question which I 

 should wish to have gone into rather more fully, but you will 

 understand that when one has something in hand to deal with, 

 it is better to devote one's attention solely to the point in ques- 

 tion. Therefore I have not very closely studied this question 



