218 Some Diseases of Plantation Rubber in Malaya 



5. Hymenochaete noxia, Berk. 



As pointed out by Brooks and Sharpies (8) the Brown Root disease 

 of plantation rubber is not of frequent occurrence in Malaya where it 

 is commoner on trees about one-and-a-half or two years old than on 

 mature trees. Petch (10) states that it is probably the commonest 

 root disease of rubber in Ceylon although it causes less damage than 

 Forties lignosus. It is specially prevalent there in old cacao land. Many 

 Malayan estates on the other hand have never been troubled with a case 

 of Hymenochaete. As is well known, roots affected by this fungus 

 are invested with masses of soil and small stones which become cemented 

 to the bark. Patches of brown mycelium are frequently found inter- 

 mixed with the debris on the exterior of the root, hence the popular 

 name of the disease. The fungus does not produce mycelial strands 

 which travel through the soil, so infection must result either through 

 the roots coming into contact with other material containing the 

 fungus or directly from spores. The fructifications of this fungus 

 have not yet been found in Malaya, and Petch (10) states that its fruit- 

 bodies have only occasionally been seen in Ceylon. 



Trees affected by Hymenochaete noxia should be burnt, and in order 

 to act on the safe side the area around them should be isolated by a 

 trench. If the ground is to be replanted it should be dug over, freed 

 from timber, and well limed. 



Although it is customary to refer the brown mycelium associated 

 with this disease in Malaya to Hymenochaete noxia, Berk., I have not 

 seen the fructifications of this fungus and therefore cannot confirm its 

 identification. 



6. Ustulina zonula (Lev.), Sacc. 



It has been thought desirable to include in this paper a summary 

 of my investigations upon the root disease of plantation rubber caused 

 by Ustulina zonala, a full account of which has appeared elsewhere (5). 



This disease had not previously been recorded on rubber in Malaya, 

 but Petch (ii) had recently noted its occurrence in Ceylon estates 

 especially where Hevea had been planted amongst tea which had been 

 subsequently allowed to die out. In Ceylon this fungus causes a serious 

 root disease of tea. 



In Malaya this disease by no means infrequently attacks old rubber 

 trees, although it is only in the few estates where groups of trees have 

 been killed that serious damage has yet been done by this fungus. 



