PEOTECTIO]Sr 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 stems 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 betAveen 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 foimd. 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 

 sliaded 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 



