A. Sharples 157 



the number of cases reported to the Department of Agriculture, and there 

 has been a corresponding increase in the districts in which it now occurs. 

 It is instructive to find that all estates which are affected were either 

 thinning-out the number of trees to the acre or had just finished this 

 work." 



The practice of planting trees to the number of 150-200 an acre on 

 rubber plantations renders necessary the cutting out of large numbers 

 when they reach the age of 6-7 years. During the thinning, attacks by 

 boring beetles on the permanent trees become prevalent. Early in 1915 

 a living specimen of a rubber tree attacked by borers was obtained. This 

 specimen {A) showed the insects active along one side of the stem ex- 

 tending from three feet above ground level to a height of twelve feet. 

 The roots were healthy. Sections through the attacked parts showed that 

 the borers were penetrating through rotten wood. Running irregularly 

 through the rotten wood were black lines very similar to those observed 

 in a typical case of dry collar-rot (PI. Ill, figs. 3 and 4). 



Immature fructifications of an Ustulina sp. were obtained on the 

 surface of the attacked parts. On a neighbouring dead tree (B) attacked 

 by borers, typical specimens of Ustulina fructifications bearing a conidial 

 layer were observed in various stages of growth upon the bark ; in close 

 proximity numerous saprophytic fungi were growing. Sections of this 

 tree showed more advanced symptoms than those found in specimen (A) ; 

 these symptoms were identical with those found in the dry collar-rot of 

 Hevea hrasiliensis caused by U. zonata. A fungus was isolated from the 

 affected wood in specimen {A) which proved to be practically identical 

 with cultures established from typical dry collar-rot trees. 



It would appear from the above that there is some connection be- 

 tween TJ. zonata and attacks by boring beetles. Much evidence to support 

 a close connection can be advanced. Several estates in the F. M. S. were 

 troubled during 1915 with leaf fires. Owing to a heavy wintering the 

 leaves formed a layer several inches thick on the ground, and when dry 

 the leaves are easily fired. In the areas through which the fires passed 

 the bark of the trees was scorched and boring beetles quickly entered, 

 though the latex streamed freely. On one estate, every tree in a nine- 

 acre block of rubber, nine years old, had to be removed; four other 

 estates encountered the same trouble on a smaller scale. In every tree 

 entered by the borers the same symptoms described for specimen {A) 

 were observed; the insects were penetrating actively a rotting portion of 

 the wood through which black lines ran irregularly. Some time was spent 

 trying to find scorched trees attacked by the fungus only. Specimens 



