118 THE PARA RUBBER TREE 



Leaf Diseases. — The leaf diseases which have appeared 

 on Hevea brasiliensis up to the present time are not of 

 much importance to the planter, as they do Httle damage 

 and are chiefly confined to seedlmgs in the nurseries. 

 It is stated that they can be effectively treated in the 

 nurseries by spraying the plants with a boiled lime- 

 sulphur mixture. 



Stem Diseases. — The principal stem diseases of Hevea 

 brasiliensis are : (1) a so-called canlcer, caused by Phytoph- 

 thora Faheri, Maubl., which kills the portion of the 

 cortex affected, but does not form an open wound ; (2) 

 a true canker caused by a species of ConiothjTium ; (3) 

 a " pink disease " due to Corticium salmonicolor , B. and 

 Br. (0. javanicum, Zimm.), which is easily recognised 

 by the formation of a pink fihn on the stem ; and (4) 

 " die back," the chief cause of which is a Diplodia form 

 of fungus which has been described under various names. 



In the case of " canker " and " die back," the affected 

 portions must be removed and the cut surfaces protected 

 until they have healed. Spraying the stems with 

 Bordeaux mixture is useful in dealing with all these 

 diseases, as it destroys the spores and consequently 

 prevents the spread of the fungus. 



Boot Diseases. — Three forms of root disease have been 

 recorded as attacking Hevea brasiliensis : ( 1 ) Fomes 

 semitostus, Berk., M^hich covers the roots with white 

 threads ; (2) Hymenochaete noxia, Berk., which covers 

 the roots with brown or black threads ; and (3) Sphaero- 

 stilbe repens, B. and Br., which gives no outward sign 

 of its presence, but forms dark red or black strands 

 between the cortex and wood of the root. When attacked 

 by root disease, a tree gradually dies back, owing to 

 the inability of the roots to perform their proper func- 

 tions, and very frequently it is finally blown over. 



Fomes semitostiLS is by far the most important of the 

 diseases which attack Hevea trees, and on some estates 

 in Malaya and Ceylon considerable losses have been 

 caused by it. A similar, if not identical, fungus attacks 

 Hevea brasiliensis in West Africa. As a general rule it is 

 not possible to save the affected trees, and the usual 

 remedial measures consist in cutting them down and 

 digging out the roots, together with any adjacent jungle 

 stumps, and burning the whole. A trench about 2^ ft. 



