60 Pink Disease of Plantation Rubber 



trees in the neighbourhood of rubber estates in Southern India. The 

 fungus has probably spread from native hosts to plants that have been 

 introduced, such as rubber, coffee, tea, and cinchona. There is one 

 doubtful record of it on a jungle tree in Malaya, but one cannot say at 

 present whether it occurs to any appreciable extent in the forests. 

 Unfortunately Corticium salmonicolor has shown a considerable liking 

 for rubber trees, and as far as Malaya is concerned Hevea brasiliensis is 

 by far the commonest host for the disease. The disease is much more 

 prevalent in some parts of the country than in others and there are 

 some large areas where the disease has not yet been found. The disease 

 is most abundant at present in the districts of heaviest rainfall and 

 where large tracts of jungle remain. 



Field Observations. 



Pink Disease attacks rubber trees of various ages though it is not 

 often seen on trees less than two years old. An attack often begins in 

 a fork of a tree on account of the accumulation of water there, but 

 sometimes the disease affects a branch in the middle and it has been 

 seen occasionally to attack the main stem. The disease develops most 

 rapidly during periods of heavy rain. In dry weather obvious signs 

 of the fungus frequently disappear to appear again when the rains come. 



The manifestations of Pink Disease on rubber trees are extremely 

 variable. The disease is so called because the fungus often causes a 

 pink incrustation on the branches or main stem, which is more specially 

 developed on the under or shady side (shown on the right-hand side 

 of Plate XVI, fig. 2). In this condition the disease is very striking 

 and cannot be mistaken. The incrustation cracks irregularly after a 

 time and the bright pink colour rapidly fades to a dingy white. There 

 are, however, at least three other forms in which the fungus appears 

 on rubber trees: 



(a) Pink Disease frequently assumes the form of white or pale 

 pink pustules arranged more or less in lines parallel with the branches. 

 This is the "Hockerchen" form of Kant (10). 



(b) At other times part of the fungus on the exterior consists of 

 white or pale pink strands of a cobweb-like texture which rim irregu- 

 larly downwards over the surface, the strands being sometimes so 

 delicate as to be overlooked (cf. Plate XVI, fig. 1). This is the 

 "Spinnegewebe" form of Rant (10) and is usually the first stage to 

 appear on an affected tree. 



