245 



fungus had bjen commenced before my departure from England and 

 were practically completed by the end of the year, the establishment 

 of the identity between this fungus and the "die-back" fungus on 

 cacao in other parts of the tropics has been made, and a fairly 

 accurate knowledge of its life-history has been obtained. A preli- 

 minary note on these points was issued in the Agricultural Bulletin 

 of December, 1910. 



An account of a bacterial disease of potato and tomato was 

 published in the same issue of the Agricultural Bulletin. 



Greater attention has been paid to the diseases of Hevea brasi- 

 liensis than to those of other plants. To review the diseases of this 

 plant from a general aspect, it may justly be said that the plant com- 

 pares most favourably with the staple plant industries of other 

 tropical countries. It must, however, be admitted that the continued 

 cultivation of one plant in pure culture over large areas, without the 

 intervention of other crops or, in many cases, of belts of natural jungle, 

 lends itself somewhat readily to the development and spread of 

 fungus disease. It should not, therefore, be surprising if there were 

 an increase of its parasitic fungi, both in quantity and in number; 

 this will call for the application of methods of treatment other than 

 those which are employed at the present day. 



Some danger may arise both from the importation of pests and 

 from the absence of proper treatment of disease in native cultivations. 



DISEASES OF PARA RUBBER. 



Root Diseases. — Fames semitostus, Berk., appears to be more 

 prevalent in this country than in Ceylon. The amount of the fungus 

 which is present on young clearings is directly proportional to the 

 amount which is present in the original jungle. The fungus, there- 

 fore, continues to make its presence felt among younger rubber, 

 where a death-rate of as many as 16 per cent, of the trees has been 

 recorded in 18 months. Consequent upon the removal of timber, the 

 isolation of diseased areas b}^ a system of trenches, the removal of 

 trees which have succumbed, the digging over and subsequent liming 

 of diseased areas, the fungus gradually disappears as the rubber 

 grows older, until on those estates where careful treatment has been 

 practised it is practically absent among the older rubber. The rate 

 of spread of the fungus mycelium in the soil is directly proportional 

 to the water-content of the soil or, in other words, to its capacity for 

 drainage. Whereas on the lighter soils there is no appreciable spread 

 of mycelium independently of actual contact with roots, on the lowly- 

 ing, damp, heavy and badly drained soils an independent spread of 

 the mycelium occurs, and the rate of growth, and consequent period 

 of retention of the fungus by the soil, are much increased. This is a 

 factor which has not hitherto been brought to light and which should 

 be borne in mind in the opening up of land for planting and in the 

 drainage and removal of timber of the heavy, lowlying soils. The 



