PROTECTION FROM THE LOCUST BORER. 7 
few root sprouts occur in this tract. They are now producing a more 
dense shade and natural pruning is taking place. At an earlier date, 
when the trees were less; dense, borers attacked, but as the density 
increased they probably were repelled before the trees were seriously 
injured. 
The diameter of the stand on the south side averages several inches 
more than that of the standing trees on the north side. If these trees 
on the south side had been planted several feet closer, say 6 by 6 in- 
stead of 8 by 10 feet, it is the writer's opinion that they would now 
have unbranched steins with practically no borer defects. 
11. On the low-grade freight line between Martic Forge and Co- 
lumbia, Pa., are five plantations set out in 1906 containing about 
150,000 trees. None of these have ever received any attention in the 
way of pruning. They present conditions varying from such as 
described at Kinzers (example 8) to almost perfect stands free from 
borer injury. In no single plantation are the trees all destroyed or 
all in good condition, but the extremes are found in different parts 
of each tract. Another factor has been responsible here. A definite 
correlation exists between those parts of the plantation that have been 
run over by fire and those parts which were by nature of their posi- 
tion less subject to fire. Where fire has burned over repeatedly, kill- 
ing the undergrowth, the worst destruction by borers is found. In 
many places the locusts themselves have been killed. One tract near 
Shenks Ferry attracted particular attention. It extends from the 
roadbed across a bottom and up over a hillside. Fire no doubt has 
gone through the part near the tracks repeatedly, as evidenced by the 
different ages of scars on the standing trees. Here there is little 
undergrowth; the locusts are scattered (many have been fire-killed), 
and all are severely infested. On the hillside and over the crest, fires, 
for some reason, have not gone through. The locusts have grown up 
in a dense stand mixed with much underbrush, and oak and chestnut 
sprouts from the original stumpage. These trees are now in excel- 
lent condition ; they are tall, straight, thrifty, not branched, and free 
from borer defects. -In some parts the shade of the mixed stand has 
become so dense that all weeds, briers, and underbrush have been 
shaded out. 
12. Along the railroad between Harrisburg and Huntingdon, Pa., 
much locust has been planted, and many natural stands occur. The 
condition of the locust in this region is generally so much better and 
so much more thrifty that the first examination gave the impres- 
sion that it is an exceptionally favorable situation for the growth of 
the tree. It is no doubt true that certain localities are better adapted 
to the growth of black locust, but the essential factor in this location 
is considered to be more than purely a favorable situation. The 
locusts are growing in a narrow belt of river terrace from a few 
