F. T. Brooks -215 



4. Sphaerostilbe repens, B. and Br. 



During 1914 a considerable number of rubber trees were found 

 to be affected by the fungus Sphaerostilbe repens which attacks the root 

 system and advances upwards into the lower part of the trunk. The 

 only previous record of this disease of rubber in Malaya was made by 

 Richards (12) who mentions its occurrence in his report for 1912-13. 

 According to the experience of the present writer this disease is by 

 no means rare in older rubber planted on low-lying land in Malaya ; 

 it has been found in Northern Perak, in the district around Teluk 

 Anson, and in the coast lands of Selangor. Only a few trees on 

 undulating land were seen to be affected by it. The disease was first 

 found on rubber estates in Ceylon in 1907 by Petch (10), who states 

 that it is not confined there to the low country. 



The foliage of rubber trees affected by Sphaerostilbe repens becomes 

 thin and the branches gradually die back. The progress of the fungus 

 being slow, a considerable time may elapse before the whole of the 

 collar or all the lateral roots are affected and the tree succumbs. 



If the roots of a tree affected by Sphaerostilbe repens are examined, 

 the disease can be readily distinguished from the troubles caused by 

 Fomes lignosus and by Hymenochaete noxia on account of the absence 

 of external mycelium and by the presence of characteristic mycelial 

 strands or rhizomorphs between the bark and the wood. These strands 

 are usually flattened, are about \ inch in diameter, and vary in colour 

 according to age from grey to dark brown or black; they are spread 

 irregularly between the bark and the wood and sometimes occur also 

 in the bark (cf. Plate XXXIII, fig. 1). 



Even when the rhizomorphs have decayed, their former position 

 is indicated by the presence of corresponding dark lines on the surface 

 of the wood. I did not observe any tendency for these strands to 

 spread independently through the soil. The affected trees were not 

 usually contiguous to one another. The finer mycelium of this fungus 

 permeates all parts of the bark and wood of the affected roots, the wood 

 becoming discoloured and the bark often assuming a bluish purple colour 

 when cut open. The roots of rubber trees affected by Sphaerostilbe 

 repens often have a particularly foul smell, but this may be a secondary 

 phenomenon induced by other agents of decay. The fungus advances 

 up the tap root or along the laterals to the collar of the tree. On several 

 occasions I observed it making considerable progress up the trunk, 

 especially in the wood (cf. Plate XXXIV, fig. 3), and in these trees 



