8 BULLETIN 787, U. S. DEPAKTMEISTT OF AGRICULTURE. 



yards to a mile wide between the foot of the mountain and the 

 Susquehanna and Juniata Rivers. There is much humidity, and all 

 vegetation is vigorous. 



It is believed that the good condition of these locusts and the 

 decided absence of injury by borers are due to the fact that the 

 situation is conducive to a rapid growth of underbrush and plants 

 characteristic of river shores wliich have afforded protection to the 

 locusts. This is further emphasized by the fact that in other localities 

 are found trees of equal size and good appearance, as described at 

 Shenks Ferry (example 11), of. the same age. Also in the same 

 locality we find trees deformed and aborted by borer injury, as de- 

 scribed in the following paragraph. 



13. Along the Juniata River between Newport and Old Ferry, 

 Pa., a continuous plantation of locust set out in 1904 extends for a 

 distance of 2 miles. These trees, especially that part near Newport, 

 show the best stand of all the plantations. After planting no atten- 

 tion was given them until 1914, when they were thinned to afford a 

 view of the, river from the trains. At this time most of the stems 

 had reached a sufficient size to be immune from borer attack. The 

 trees nearest Newport now average 5 to 8 inches in diameter. They 

 are straight, free from branches, and about as tall as the telegraph 

 poles near by. The bark is ridged naturally, showing absence of 

 borer injury in the past. Nothing definite as to how these trees 

 grew in the period intervening between planting and first pruning 

 could be ascertained, but from a study of many plots of all ages 

 along the river it is certain that they were intermixed with a dense 

 growth of other shrubs and weeds. Natural pruning and thinning 

 have taken place to such an extent that few living branches are 

 found below the crown, and manj^ trees have been suppressed and 

 killed. Farther back from the railroad, where no pruning at all 

 was done, the dead, suppressed trees and shaded-out branches give 

 a good idea as to how rapidly this process takes place in the tree. 



In this 2-mile strip of locusts the borers are serious in two places 

 and have caused many trees to break off or have stunted the gTowth 

 badly. In one of these places fire has gone through ; the other was 

 evidently pruned (as shown by scars) to afford a view of a pond just 

 behind. These last trees were also isolated in the sense that the rows 

 were only two trees deep. These trees average scarcely half the 

 diameter of those in the better parts of the grove. 



CONDITION OF TREE NECESSARY FOR BORER ATTACK. 



All trees and all parts of the tree are not subject to attack by the 

 borer to the same degree. 



Moderately rough bark seems to be an essential condition, since it 

 provides the necessary crevices in which the adults deposit their eggs. 



