49 



vegetation from attacks of insects by killing the young 

 when they begin to bore into the tissues . Such a wash 

 should be applied early in the spring before the beetles 

 emerge, and should be renewed from time to time as long 

 as there is danger of beetles being about, i. e. until the 

 middle of July. 



A good many years ago a French authority on forestry 

 recommended the scraping and cutting away of the bark 

 of trees attacked by borers as one of the most satisfactory 

 remedies known to him . His idea was that this treat- 

 ment encouraged the flow of sap to the scored bark so 

 that the grubs were unable to mine it. It is well known 

 that trees do defend themselves under some circum- 

 stances by filling up the burrows of insects as fast as 

 these are made, and on some fruit trees one may find 

 scores of burrows thus started and afterwards abandoned 

 because of a gummy exudation which fills them. The 

 experiments of the Frenchman, M. Robert, were made 

 chiefly on elms, but with reference to beetles belonging 

 to a different family from that of the American elm 

 borer. Both bore into the inner bark and sap wood 

 however, and it is probable therefore that the treatment 

 he recomends will serve as well for our elms. He began 

 by cutting out long strips of bark about 2-2.50 inches 

 wide, extending from the ground to the branches. A 

 new growth of bark was at once formed here which 

 projected as a longitudinal ridge in which the sap cir- 

 culated so vigorously, that the grubs in the immediate 

 neighborhood were destroyed, and the tree itself showed 

 an increase in general vigor. His next experiment was to 

 remove from infested trees all the'outer bark of the trunk 

 usually styled the corky layer. It was found that the 

 grubs in the inner bark quickly perished, either from the 

 increased flow of sap, or from more complete exposure_to 

 jihe aotaon of the sun. He claimed that this treatment 



