'210 Some Diseases of Plantation Rubber in Malaya 



boring beetles had begun to penetrate the diseased tissues. The shot- 

 hole borer usually attacks portions of rubber trees which have been 

 previously injured by some fungus: the region attacked by these 

 insects is often not affected by a fungus advancing from the root 

 system but in the specimens now referred to there was clearly a 

 connection between the attack of the borers and the advance of 

 Sphaerostilbe repens into the trunk. As the writer has pointed out 

 elsewhere (5), rubber trees affected by the fungus Ustulina zonula 

 advancing upwards from the collar are sometimes attacked by borers 

 in the same manner. 



Most of the trees seen to be affected by Sphaerostilbe repots were 

 magnificent specimens of plantation rubber, 15 to 20 years old; the 

 other trees had been recently brought into the tapping round or were 

 ready for tapping. 



The fructifications of Sphaerostilbe repens are of two kinds, both 

 being minute. The first form to appear is the conidial stage which 

 consists of white or pinkish white blobs about the size of a pin's head 

 borne at the ends of pink stalks which are about T ^ to ^ inch long and 

 are hairy when young (cf. Plate XXXIII, fig. 2). This is the Stilbum 

 stage and it arises from portions of the host permeated by the fungus 

 or directly from the rhizomorphs ; the conidial fructifications have also 

 been seen on clayey soil lying in contact with diseased roots. These 

 reproductive bodies have occasionally been found below the surface of 

 the ground. The spores which arise at the extremities of the Stilbum type 

 of fructification are hyaline, oval, and 10-20/x x 5-9/a in size. Another 

 Stilbum is an exceedingly common saprophyte on dead portions of rubber 

 trees. This is Stilbum, cinnabarinum, the conidial stage of Megalonectria 

 pseudotrichia, readily distinguishable from the conidial stage of Spliaero- 

 stilbe repens by its red colour and smaller size. After the formation 

 of conidia the fungus sometimes produces small, dark red peritheci;) , 

 but 1 found these only rarely. 



Sphaerostilbe repens sometimes lives entirely as a saprophyte on 

 dead plant tissues and doubt has been expressed whether it is really 

 parasitic on the roots of Hevea. In rubber trees affected by it thai 

 I was able to examine it was undoubtedly advancing into living tissues 

 and therefore acting as a parasite. The actual means by which infection 

 of the roots is effected by this fungus are unknown. The roots may 

 sometimes have been already injured by adverse conditions such as 

 bad drainage, and if the fungus entered such roots it might easily pass 

 thence into healthy tissues. 



