THE GENUS DENDROCTONUS. 151 



masses on the surface, traces of primary galleries under the bark or 

 on the wood, or round holes in the loose dead bark over the wound. 

 The commercial value of the trees attacked by this beetle is not 

 materially affected until after the injury has been extended into the 

 trunk by fire, wood-boring insects, decay, etc., to a point where the 

 vitality is greatly reduced or the tree becomes worthless. 



FAVORABLE AND UNFAVORABLE CONDITIONS FOR THE BEETLE. 



Favorable conditions for the multiplication of this beetle and its 

 injury to living timber are found in sections where for several years 

 a large amount of pine timber has been killed or injured by insects, 

 or felled and broken by storms, lumbering operations, etc., followed 

 by a year in which no timber dies or is injured or killed. Under 

 these conditions the vast numbers of this insect which have bred in 

 the injured and dying trees will, through necessity, attack the living 

 trees and cause serious and widespread damage the first year. This 

 will usually be followed by little or no damage in succeeding years, 

 unless favorable conditions are again presented for their multipli- 

 cation. The first year after the disappearance of the southern pine 

 beetle in West Virginia the swarms of the red turpentine beetle 

 caused extensive injuries to the base of living trees, but for many 

 years thereafter the species was rare and did no harm. Unfavor- 

 able conditions for injury to living trees by this insect are found in 

 healthy forests under a system of forest management which requires 

 more or less continuous timber-cutting operations to utilize the older 

 matured, injured, and dying trees. 



METHODS OF CONTROL. 



Since the habits of this beetle and the character of the injury 

 caused by it are in marked contrast to those of nearly all other 

 species of the genus, the problem of control is quite different. The 

 principal injury is to the base of living trees, which, in itself, may be 

 slight, but when aggravated and extended by subsequent and quite 

 different causes may become quite extensive. Therefore the object 

 should be to prevent the primary injury by preventing the undue 

 multiplication of the beetle, or by furnishing a continuous supply of 

 more attractive breeding places, as in the case of continued lumber- 

 ing operations. The first may be accomplished if within quite an 

 extensive area the infested bark is removed from the base of insect- 

 killed, lightning-struck, and otherwise injured or dying trees, as well 

 as from the stumps of those felled during local or sporadic timber- 

 cutting operations. This work should be done during the fall and 

 winter following infestation, beginning with the first of September 

 and ending with the first of March. Where only a few trees in a lawn 



