RUBBER 607 



time during those months. The decaying patches usually 

 run vertically, and first appear on the exposed cortex 

 within an inch of the tapping cut. Narrow sunken 

 vertical lines are seen above the tapping cut, and if the 

 thin layer of original cortex is cut away a narrow black 

 streak is found extending into the wood. If the weather 

 continues wet the black patches extend upwards and 

 downwards, and at the same time increase in width; and 

 if a number of them have arisen close together they may 

 coalesce, so that a wide horizontal strip of renewing bark 

 is destroyed. More usually, however, a number of 

 parallel vertical wounds are formed. When dry weather 

 sets in this decay stops and the wounds begin to heal up; 

 but the renewal is, in any case, rough, and, where several 

 wounds have coalesced, so much cortex is destroyed that 

 renewal cannot be completed for many years. 



This decay of the tapped surface is often attributed 

 to bad tapping. It is, however, distinguished by the fact 

 that the wounds are vertical, whereas tapping wounds 

 are usually horizontal. Moreover, tapping wounds extend 

 to the wood, while in the case now discussed a thin layer 

 of dead cortex is left overlying the wound, and may be 

 detected on close examination six months afterwards. 



Inoculations with various organisms found in these 

 decaying patches in Ceylon have failed to reproduce this 

 effect. In Java it is attributed to canker (Phytophthora 

 Faberi), but we have not been able to obtain any evidence 

 of that. 



A method of treatment which is said to have proved 

 successful in Java is now being tried in Ceylon. As soon 

 as the narrow vertical lines are observed the tree is put 

 out of tapping. The affected tapping surface is then 

 washed every four or five days with a 50 per cent, solution 

 of carbolineum plantarium. According to the reports 

 from Java, the tree can be tapped again after about four 

 weeks. If a large patch has decayed, the dead cortex is 

 cut out before treatment with carbolineum. 



