RUBBER 599 



Grevillea and tea have furnished suggestions which may 

 explain this spread of the disease to fresh centres in the 

 apparent absence of any fructification and spores, but 

 these have not yet been completed. 



Of the stem diseases, " pink disease " and " dieback " 

 are of minor importance in Ceylon. The former is 

 apparently exceedingly common in Java, where it has 

 been fully investigated by Zimmermann, Zehntner, and 

 Rant. 



Pink disease is caused by Cofticium salmonicolor, B. 

 and Br. (Corticium javanicum, Zimm.). The fungus is 

 widely distributed through the Eastern tropics, but the 

 damage caused by it varies considerably. In Java, Dr. 

 Rant has enumerated 141 species of wild and cultivated 

 plants which are known to be attacked by it; but on the 

 mainland, in the Federated Malay States, it appears to 

 be scarcely known. In Ceylon and India the conditions 

 are reversed, for it has caused much loss in South India, 

 but very little in Ceylon. It occurs on various plants in 

 Ceylon up to an elevation of 5,000 ft., but only sporadic- 

 ally. To the list of hosts given by Rant, Ceylon can 

 add camphor and Poly alt hia longi folia. 



In Hevea the disease usually attacks the main stem at 

 or immediately below a fork. The bark dies and splits 

 away from the wood, sometimes all round the stem, 

 sometimes over a limited patch. In the former case the 

 tree is ringed and the crown dies; in the latter the dead 

 bark scales off and an open wound is left. The difference 

 is probably due to weather conditions. 



The fungus makes its appearance on the diseased bark 

 in three forms. In one form minute pink cushions are 

 produced in small cracks in the bark; this form has been 

 described as a different fungus (Necator decretus, Mass.). 

 In the early stages of this form the minute cracks 

 resemble large lenticels, and this, before the pink 

 cushions appear, has been styled the " measles " stage. 

 In a second form the hyphse of the fungus extend over 

 the surface of the bark in long, silky strands which may 

 coalesce and form a thin shining plate of fungus tissue. 

 The third form is the fully developed fructification, a thin 

 pink sheet overlying the bark, and ultimately . splitting 



