184 SHADE-TREES IN TOWNS AND CITIES 



The injuries to trees by borers are very severe. When 

 they girdle a limb the effect is immediate. The circulation of 

 the sap is cut off from the end of the branch and it soon dies. 

 When a large wound is made on the side of a branch, the 

 bark covering it breaks away, the wood is exposed, it dries 

 and checks, the successive annual layers do not cover up 

 the scar, so that in time the circulation of the sap is re- 

 tarded and the end of the limb dies. The injury to the trees 

 in that case is not immediately apparent, but is none the 

 less fatal. 



The leopard moth is hard to combat. The moths do not 

 feed and the caterpillars feed on the surface only for a short 

 time, when they change their quarters and start in a new 

 place. At the end of July and during August the laivse 

 force great strings of partly digested wood or "sawdust" 

 through the openings by which they entered. At that time 

 they can be readily killed by injecting through the openings 

 of the burrows a few drops of bisulfiid of carbon and clos- 

 ing them with putty. 



When the trees of a city are attacked by borers it would 

 seem that the task of combating them is almost hopeless. 

 Persistence will yield results, however. On August 20, 1909, 

 for example, the Shade-Tree Commission of East Orange 

 began work against the leopard moth. By September 22, 

 about eight thousand trees were treated by a gang of six 

 men. Two methods were used to kill the borers; by in- 

 jecting carbon bisulfid into the burrow and plugging the 

 opening with putty, and also by using a wire. The latter 

 method was found to be more rapid. Badly infested small 

 branches were entirely removed. 



In this work it was possible to cover only the trunks and 

 the main limbs of the trees. The men could not reach the 



