6 



white pine reproduction. These cases are of such sporadic occur- 

 rence and of such minor importance that they are neghgible. 



SUGAR PINE IN THE PACIFIC COAST REGION 



The bark beetle Dendroctonus monticolae Hopk. is also the principal 

 enemy of the sugar pine (Pinus lambertiana) in the forests of the 

 Pacific coast. As in white pine, it breeds both in cull logs and in 

 standing trees. This species of pine is not, however, subject to 

 heavy epidemics of infestation such as occur in yellow pine, and no 

 heavy killings have yet been traced to the slash of logging operations. 

 On the Yawkey tract, near Fort Klamath, Oreg., in 1922 and 1923, 

 Patterson, Keen, and Hauge noted a considerable increase in the 

 numbers of standing trees killed shortly after many trees were blown 

 down by a high wind. In general, the considerations applying to 

 utilization and slash disposal in the case of white pine apply to this 

 species as well. 



WESTERN YELLOW PINE 



In California and Oregon the western pine beetle, Dendroctonus 

 hrevicomis Lee, is the principal insect enemy of the western yellow 

 pine {Pinus ponderosa). Besides attacking living trees this insect 

 breeds in the trunks of fallen trees which are more than 6 inches 

 in diameter. 



In some cases it has been noted that heavy losses by insects have 

 followed logging operations, whereas in other cases logging areas have 

 been singularly exempt from such injury. Keen reports that on the 

 southern Oregon-northern California project two of the cleanest areas 

 were adjacent to areas where continuous logging had been in progress 

 for several years ; that one heavily infested area was adjacent to a 

 logged area where operations had ceased; and that in one unit a 

 reduction of 60 per cent in infestation, equal to the best obtained by 

 artificial control work, followed the beginning of logging operations 

 on 'adjacent ground. 



To determine if possible the reason for this condition, Person 

 carried out some investigations in southern Oregon and central Cali- 

 fornia. Eleven logging slash areas, two road slash areas, and one 

 group of windfalls were studied. By bark counts made on 459 pieces 

 of slash it was found that the average number of attacking beetles 

 per square foot was 9.8, and the number of beetles emerging, 16. 

 Similar studies were made by Patterson in southern Oregon. Five 

 logging areas, one windfall area, and 24 miles of road slash were 

 studied; the last named involved the examination of 1,425 pieces of 

 slash, including the examination of 1 square foot of bark on each of 

 1,075 trees. Bark counts in this material gave 15.6 beetles per square 

 foot attacking and 19 beetles per square foot emerging. Bark counts 

 made on hundreds of standing trees near by showed an average attack 

 of 23 Dendroctonus beetles per square foot, with 54 beetles emerging. 

 It is evident that the attack and emergence on slash material is far 

 below that for standing trees. In all of these studies checks on the 

 surrounding infestation were made before, during, and for several 

 years after the laying down of the slash. 



Usually the first effect of the slash was to increase the infestation 

 in standing trees in the vicinity. In every case, however, this increase 

 occurred simultaneously with the attack on the slash, instead of follow- 

 ing the emergence of the beetles breeding in the slash. 



