10 DEPARTMENT CIECULAR 411, U. S. DEPT. OF AGRICULTCTRE 



SPRUCE SLASH 



SPRUCE IN THE NORTHEAST 



Several species of bark beetles breed in the stumps, logs, or tops 

 of spruce {Picea canadensis, P. rubens and P. mariana), and attack 

 and kill living trees. 



The eastern spruce beetle (Dendrodonus piceaperda Hopk.) is a 

 particularly destructive species which breeds in stumps and cull logs. 

 It has destroyed large areas of mature spruce forests in the past, and 

 active epidemics are now in progress in Canada, even in second- 

 growth stands. Recent observations by Craighead indicate that it 

 is most destructive only when accompanied by one or more species of 

 Ips, which combine with it and attack the upper stems. 



Several species of Ips (/. horealis Sw., /. perturhatus Eichh., and 

 /. chagnoni Sw.) have in two cases been observed by Craighead breed- 

 ing in slash, and in the following year attacking and killing near-by 

 living trees. From these, however, scanty broods developed, and in 

 the third year the outbreaks completely died out. 



Special methods of slash disposal do not appear to be justified 

 from the entomological standpoint, but cull logs and larger debris 

 should not be left in the woods {16, p. 85). The increasingly closer 

 utilization practiced in this region with the development of the 

 pulp industry will undoubtedly tend to minimize such losses. 



SPRUCE IN THE GREAT LAKES REGION 



There is no specific evidence to prove that spruce slash in the 

 Lake States has any entomological significance, although there is 

 justification for suspecting that the larger pieces may be of some 

 importance. Most of the spruce {Picea canadensis and P. mariana) 

 cut in this region finds its way to pulp mills, a fact which makes 

 for close utilization. A comparatively small quantity of material 

 suitable for the breeding of potentially injurious insects is left in the 

 woods after logging operations. 



ENGELMANN SPRUCE IN THE ROCKY MOUNTAIN REGION 



The Engelmann spruce beetle {Dendroctonus engelmanni Hopk.) 

 breeds in the cuUs and stumps of the Engelmann spruce {Picea engel- 

 manni) and also attacks and kills living trees. The small quantity 

 of timber of this species which is now being cut makes of small 

 importance the danger from this source. No opportunity has yet 

 presented itself for the study of the effect of extensive logging on 

 this insect. 



DOUGLAS FIR SLASH 



There are several insects which breed in the large pieces of slash 

 of Douglas fir {Pseudotsuga taxifolia) and are capable of killing liv- 

 ing trees, though they rarely do so. The more important of these 

 are Dendroctonus pseudotsugae Hopk., Scolytus unispinosus Lee, and 

 MelanopJiila drummondi Kirby. 



In the region along the Pacific coast reports on observations of the 

 death of Douglas fir from the attack of insects that breed in slash are 

 so infrequent that they can be disregarded. This fact may be due to 



