56 



SPHAERONEMA SP. (MOULDY ROT OF THE 

 TAPPED SURFACE). 



By A. R. SANDERSON, F.L.S. and H. SUTCLIFFE, A.R.C.S. 



{Mycologists to the Rubber Growers' Association, 

 Federated Malay States.) 



(With 4 Plates.) 



The treatment to which the rubber tree (Hevea brasiliensis) is subjected 

 in order to obtain the latex, viz. excision of bark and the major portion 

 of the cortex in the form of thin shavings at frequent and regular 

 intervals (this constitutes the operation known as "tapping"), leaving 

 only a thin cover of the inner cortex overlying the cambium, is such 

 that there is little cause for wonder when one learns that the exposed 

 tissue is attacked by fungoid pests, some of which are capable of estab- 

 lishing themselves as parasites in the cortical tissue. Some indeed go 

 further than this and pass through to the wood elements beneath and 

 becoming firmly established there, spread up or down in a vertical 

 direction, killing the cambium and the cortical tissues outside. 



One of the most dangerous of these parasites, since it destroys the 

 cortical tissue and thus ruins the tree so far as the production of revenue 

 is concerned, is a species of Sphaeronema which is the responsible agent 

 in causing the rotting or destruction of the tapped surface, i.e. this 

 fungus utterly destroys the thin skin of cortex remaining after tapping, 

 hence delaying the renewal, and in fact making it almost or quite im- 

 possible for tapping to be carried on over that section again. Normally 

 a tapped surface can be tapped over again in from 5-6 years or even 

 sooner, as by that time the regenerated cortex is sufficiently mature to 

 yield an amount of latex which is remunerative. 



In the Agricultural Bulletin of the Federated Malay States, Vol. vi, 

 No. 1, October 1917, Messrs Belgrave and de la Mare Norris writing on 

 Bark Cankers and their treatment, describe a bark canker as "Mouldy 

 Rot of recently Tapped Surface." Though stating that inoculation ex- 

 periments indicate Sphaeronema as the causal fungus they apparently 

 had not definitely determined the point. 



