]70 Ustiilina Zunata {Lev.) Sacc. on Hevea Brasiliensis 



plantations by means of the spores after the thinning-out period. The 

 fungus enters permanent trees attacked by boring beetles and quickly 

 kills them, and the stumps and felled logs form excellent material in 

 which the beetles and fungus may work together. But the fuiigus alone 

 can enter and grow through any soft-wood timber without the aid of the 

 insects. 



All trees attacked by boring beetles should be immediately cut out 

 and destroyed, as they represent one of the worst sources of infection. 

 Strict attention should be given to trees scorched by fire, and if borers 

 attempt to enter, a coating of tar and crude oil (80 per cent.-20 per cent.) 

 should be applied over the scorched surfaces. In the case of scorched 

 trees resulting from leaf fires, the burnt areas are usually situated near 

 ground level, and can be easily treated with the tar mixture. A second 

 coating should c|uickly follow the first. Scorching of higher branches 

 resulting from burning of piles of timber is not so easily treated, but as 

 far as observation goes, these branches are not often attacked by the 

 insects; in any case they can be cut away from the main stem quite 

 easily. 



The cases of leaf fires noted this year — 1916 — support the observa- 

 tions made in 1915 and given above. One interesting case was noted: an 

 estate was visited four days after the fire and borers were already at 

 work on half a dozen trees not badly scorched; latex was exuding freely 

 from the boreholes. 



At the time of thinning-out a tremendous increase of suitable food 

 material for the fungus becomes available. Practically all stumps and 

 felled logs of rubber if left lying about the plantation for any length of 

 time show signs of Ustulina zonata. The fructifications develop on the 

 surface of these logs and stumps, and for a short period corresponding to 

 the weekly one observed in the Laboratory, a copious supply of spores 

 (conidia) is produced and blown about the plantation by the wind. 

 Later, the ascospores ripen, and these are distributed amongst the trees 

 by various agencies. 



The spores come to rest in wounds in the collar and lateral roots of 

 the permanent trees and under suitable conditions germinate. The fungus 

 develops slowly, and several years later when the trees are passing the 

 ten years' limit, some begin to show a thin crown of leaves. If the collar 

 is now cut open, the characteristic dry-rot will be found. 



The fungus is also found on rotting jungle timber and on old jungle 

 stumps left in the plantations after burning-oft'. It is not so common in 

 the early years as it is during or after the thinning-out period, though 



