INSECT INJURY TO CHESTNUT AND PINE TREES IN VIRGINIA 

 AND NEIGHBORING STATES. 



By F. H. Chittenden. 



Recent years have witnessed extensive destruction of the pine and 

 spruce forests in the United States, particularly in that portion of the 

 South east of the Blue Ridge Mountain range, and to a lesser extent 

 of chestnut trees in the same and other regions. This injury has been 

 very generally attributed to insects, and there is evidence that certain 

 wood and bark boring species have largely contributed to the work of 

 demolition. The death of the chestnuts has been laid to the account 

 of the buprestid, Agrilus bilineatus Weber, while the destruction of 

 the coniferous trees has in like manner been credited to the scolytid 

 bark-beetle, Dendroctonus frontalis Zimm. 



The writer has always felt a certain degree of skepticism as to 

 whether perfectly healthy forest growth would, save in exceptional 

 cases like the present, succumb to insect attack, and were not this view 

 shared by others it might sound like heresy to say that the insects 

 mentioned are perhaps not the original cause of the injury. There is 

 more than a suspicion that a predisposing agency has been at work in 

 causing a weakened condition of the timber of the infested region. 

 Whatever has brought this about, there is every appearance that the 

 insects in question have multiplied in such numbers that they were 

 forced to attack living, if not healthy, plants or perish, as they belong 

 to groups that do not develop in timber that has been dead long enough 

 for the bark to become separated from the wood. 



Such an enfeebled condition as suggested might be caused by bacte- 

 rial or fungous disease; or it might be due to a variety of other ele- 

 ments, among which might be numbered too close growth, detective 

 drainage, insufficiency or a superabundance of subterranean moisture, 

 too great dryness, or, again, it might be produced by a dry spell sud- 

 denly following an unusually wet one, or vice versa. In the present 

 case it seems more than probable that the soil had undergone some 

 change that has interfered with the growth of the trees, or that a com- 

 bination of unfavorable atmospheric and soil conditions lias accom- 

 plished the supposed predisposing debility. The withering ami dying 

 of leaves induced by a spell of hot, dry weather following cool, moist 

 weather, and known as sun scald, might be provocative of the debili- 

 tated condition favorable to the attacks of these borers. Possibly 

 "pine blight," or what is known as winter desiccation, the latter occur- 

 ring in mild, dry winters following autumn droughts, ami particularly 

 affecting conifers, might explain the original injury to this class of i 



