PEOTECTIO:^" FROM THE LOCUST BORER. 9 



Likewise, "until they become 1^ to 2 inches in diameter at the base, 

 trees are not subject to attack unless the bark is rough. On younger 

 trees the borers are found concentrated at the base and near crotches. 



For some unknown reason trunks of trees reaching 5 to 6 inches in 

 diameter and over (excepting old brood trees) rarely are fomid to 

 contain borers. On such trees the larger branches frequently are 

 infested, but such injury is seldom common enough to do much harm 

 or even attract attention. It can be said, therefore, that protection 

 from borer injury is necessary for only a comparatively short period 

 during the tree's growth. Under good growing conditions this time 

 should not exceed 10 years. 



In every locust grove that has borers present, certain trees will be 

 found on which they have concentrated. These are called brood 

 trees. The thick, irregularly barked, gnarled appearance and stunted 

 growth will distinguish such individuals. They are often continu- 

 ously infested until they reach an old age, or 12 to 18 inches in 

 diameter. 



HOW TO RECOGNIZE TREES CONTAINING NO BORER DEFECTS. 



The larval mine made by the locust borer destroys a certain amount 

 of the growing tissue or cambiimi and makes a serious defect in the 

 wood. This injury to the cambium accelerates growth to heal it over 

 and produces a swollen or gnarly appearance. Many such defects 

 give the entire stem a roughened, distorted shape. The bark is ir- 

 regular and scaly. On the other hand, trees that have not been in- 

 jured by the borer are characterized by very regular bark, which is 

 grooved longitudinally between thick, dark ridges. With a little 

 experience these features can be quickly recognized and until the 

 tree reaches 10 to 12 inches in diameter it is possible to determine 

 accurately whether the borer defect will be found in the wood. 



CHARACTER OF GROWTH OF UNINFESTED STANDS. 



Not only is the appearance of uninjured individual trees charac- 

 teristic but pure stands of such trees have a different appearance 

 from those that are damaged. The tops of isolated natural stands 

 have a domelike outline, the innermost trees growing taller and 

 straighter, while root sprouts continuously coming up around the 

 borders form smaller and younger trees which give additional pro- 

 tection to those within. These younger trees are at first too small 

 for infestation, and when they have reached a susceptible size are 

 protected in their turn. The crowns are uniformly shaped and no 

 branches project to break the contours. Planted stands, where the 

 trees are of the same age, are uniform in height, the tops forming a 

 flat outline. No large branches are found on the trunks, but many 



