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DISEASES. 



"It is often relatively easy to successfully grow a small number 



of plants in any particular district without their suffering from 



the ravages of innumerable insects and fungi. But if the same 



crop is grown on a large scale matters often take a different 



turn There are already several insects and fungi which 



live on the leaves of the Para rubber trees, but none of them are 

 very harmful. To a very limited extent the annual fall of leaf 

 that takes place on all Para rubber trees after they have passed 

 their second or third year is an advantage when dealing with leaf 

 pests, as the foliage can be easily and regularly collected and 

 burnt. . , . 



"Fruit disease. — Para rubber planters in many parts of Ceylon 

 have occasionally been alarmed at the curious behaviour of certain 

 fruits ; some dry up and remain attached to the twigs, and others 

 of all ages fall to the ground without expelling the seeds. The 

 fall of the unexploded fruits is often due to wind, and there is no 

 parasitic fungus to be found in the tissues. It has been stated that 

 the fruits are subject to the attack of a parasitic fungus belonging 

 to the genus Nectria, and Carruthers reports having successfully 

 inoculated Para rubber fruits with this fungus, but was not certain 

 as to whether it attacked the fruits when on the tree or only when 

 they fell to the ground. 



"Themosteffective way of fighting the fruit disease is to collect 

 all dried fruits which are on the trees and those which have fallen 

 to the ground and burn the lot on the spot. On the average 

 rubber estate there can be no real objection to burning such small 

 quantities of fruits as this treatment involves. 



" Stem Disease. Fungus. — In his account of canker (Nectria) of 

 Para rubber, Carruthers points out that a parasite fungus occurs 

 on the stems and branches, which may prove fatal to the trees. 

 The area attacked by the fungus can be detected often by the 

 change of colour of the bark or by the exudation of the latex. 

 When, however, the fungus has got a firm hold of any local patch 

 of tissue, the latex tubes become quite empty and dry up, so that 

 it not only threatens the life of the tree, but also robs the planter 

 of the latex or rubber for which the tree is being cultivated. It is 

 necessary that all cankered areas should be excised and the tissue 

 burnt on the spot. All the discoloured areas should be removed, 

 even if the woody tissues below the cambium are permanently 

 damaged in the operation. In some cases it is true that the 

 cankered area is, by means of a layer of cork, prevented from 

 extending to other parts of the stem, but it is unwise to leave the 

 matter to chance. 



" Root Disease. Fungus. — A root disease due to a fungus has 

 already been mentioned as occurring in the Straits and Ceylon 

 in association with white ants, but probably preceding them. 

 Patch has shown that the Ceylon fungus can spread underground 

 on roots of grasses, &c., and that it is a species of Polyporus 

 (Fomes semitostus). The hyphae are described as occurring on 

 the first six inches of the trunks as well as the roots. Any trees 



