No. 6. DEPARTMENT OF AGRICULTURE. 241 



supposed to be caused by the action of a saliva introduced into the 

 phuit tiissuc, and it undoubtedly causes something like a true poison- 

 in*^. The injury caused by a single insect is as nothing to a tree; 

 but when this is multiplied by many thousand it becomes a serious 

 matter. The surface of the twigs becomes irregular and pitted; the 

 bark dies, cracks and the upper layers become lifeless. The purp- 

 lish red stain in the bast extends and gets even into the sap-wood. 

 The tree loses vigor and in late summer some twigs may die at the 

 tip. During the winter an entire branch may die. A start is usually 



Fifj. 3 — Section of apple, natural size, 

 closely set with scales ; a bit of scaly 

 bark enhir3:ed, at left, above, i From How- 

 ard, Circ. 3, 2d scr., Div. Eiit., U. S. Dept. 

 Agr.) 



made in the spring; but when the first drain is made by a dry spell 

 upon the circulation of the tree, it fails to respond. The poison- 

 ed bast and sap-wood prove unable to meet the demand and the tree 

 dies. Often a tree may go into the winter in apparent fair condi- 

 tion; but will break down suddenly in early summer. Peach trees 

 are especially apt to do this, and many a dead tree has been charged 

 to the insecticide employed when, as a matter of fact, it was al- 

 ready doomed when the application was made. It is important, 

 therefore, to make whatever remedial api)llcations are intended, be- 

 fore the tree or plant is so badly injured that it is unable to recover 

 when the insects are killed. 



16—6—1902 



