44 
DISEASES OF THE LEAVES AND STEM OF HEVEA 
BRASILIENSIS IN THE MALAY PENINSULA. 
By R. M. Richards, a.r.c.sc. 
(Mycologist, M.P.A. Association.) 
TXITHERTO the tree from which plantation rubber is obtained 
“ L " L has not suffered from any serious 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 this 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 unsurmoun table 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 b} r the 
treatment of diseases as they appear can we hope to keep up to this* 
standard. The planting of enormous tracts o£ 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 remedial 
measures can the rubber plantation industry keep its position of 
security. 
Where planted areas have suffered severe loss through 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 Phyiophthora causes an abnormal leaf- 
fail during the wet weather from J uly 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 
