u 



DISEASES OF THE LEAVES AND STEM OP HEVEA 

 BRASILIENSIS IN THE MALAY PENINSULA. 



By E. M. Richards, a.r.c.sc. 

 (Mycologist, M.P.A. Association.) 



TZriTHERTO the tree from which plantation rubber is obtained 

 has not suifered from any sei-ious epidemic disease. Only a 

 purely parasitic fungus which would favour Hevea as a host is 

 likely to cause an epidemic disease and it is those parts of the tree 

 above ground which would be subject to infection. Root diseases 

 have been and are serious enough on some estates but it is a fact that 

 the various fungi, which cause diseases of the root system of Hevea 

 in tliis country are preventable — that is to say, by certain means, 

 whether they be considered impracticable or otherwise, it is possible 

 to create conditions which exclude the chance of infection. 



It is quite another matter, however, to prevent air-borne spores 

 of a parasitic fungus from affecting parts of the tree above ground. 

 I do not wish to infer that it is. not possible to prevent serious loss 

 from attacks of air-borne diseases for no unsurmountable difficulty 

 has been encountered in dealing with the diseases of the leaves and 

 stem known to us up to the present time. 



The Para rubber tree in this country has so far shown itself to 

 be a particularly healthy plant, but let it be realized that only by the 

 treatment of diseases as they appear can we hope to keep up to this 

 standard. The planting of enormous tracts of contiguous areas with 

 the one kind of plant renders conditions ideal in this country for the 

 rapid propagation of disease and only by careful vigilance in the 

 treatment of disease and by the immediate adoption of I'emedial 

 measures can the rubber plantation industry keep its position of 

 security. 



Where planted areas have suffered severe loss tlirough disease 

 up to the present time, in the majority of cases this loss has been 

 due to carelessness or indifference, to the adoption of unsound 

 methods of plant sanitation owing, possibly, to false ideas of economy, 

 to the want of expert assistance at the time when the trouble arose 

 or to begrudging money for treating disease. 



In Ceylon a species of Phytophthora causes an abnormal leaf- 

 fall during the wet weather from July to September. The fungus is 

 said to spread from diseased fruit pods to the leaf stalk. The 

 attacks on the leaf stalk appear to cause the production of an 

 abscission layer at the base of the leaf stalk and so cause the fall of 

 the leaf. In wintering seasons the abscission layer is normally 



