42 



METHODS OF REDUCING THE NUMBER OF BEETLES. 



The fact that a large number of beetles must attack a living, healthy 

 tree in order to inflict injury sufficient to cause its death, ami thus 

 offer the best conditions for its future multiplication and spread, is 

 of special importance since, if their numbers can be reduced below 

 that necessary to kill the trees, their depredations on the living tim- 

 ber must end. The insect can then only survive in weakened, dying, 

 or felled trees. It would thus remain harmless until some specially 

 favorable condition would enable it to accumulate, or migrate from a 

 distance, in sufficient numbers to again successfully invade the living 

 timber. 



The facts which have been determined regarding the habits and life 

 history of the beetle suggest three methods by which their numbers 

 can be reduced : 



I. To regulate the winter logging operations so that as many of the 

 dying and infested trees as possible can be cut and the logs therefrom 

 placed in rivers, ponds, or lakes between October 1 and June 1. 



Different stages of the Dendroctonus remain in the bark during the 

 summer, cease active work about the middle of October, remain in the 

 bark over winter and until about the middle of June before the adults 

 emerge. The part of the trees that is infested is that which is util- 

 ized for logs. Therefore, if the trees are cut any time after they 

 become thoroughly infested, and the logs are hauled to the landings 

 in the winter, placed in the water and driven out of the woods in the 

 spring, vast numbers of the insects will be either drowned or so far 

 removed from the larger standing spruce that they can do no harm. 

 There are eight months in which to do the work; so if the regular 

 logging operations are (as suggested by Mr. Gary) turned in the direc- 

 tion of the worst infested areas there will be little additional expense 

 in the practical application of this method. 



II. To regulate the summer operations so that as many of the 

 infested trees as possible can be cut while the bark will peel, by the 

 removal of which from the logs and stumps of such trees most of the 

 insects will be destroyed. 



It is the practice in some sections to cut the spruce at a time when 

 the bark can be readily removed, thus facilitating transportation to 

 the mills; therefore, if the cutting can be turned in the direction of 

 the dying and infested spruce, there will be little or no additional 

 expense in cutting and removing the bark from such trees, and thus 

 all of the eggs and young stages of the beetle will be effectually 

 destroyed by the exposure and the drying of the bark. Another 

 advantage of this method, it would seem, lies in the fact that trees 

 peeled either in the winter or summer can, if necessary, be left in the 

 woods for several years, probably without serious detriment. The 

 preservation of such peeled logs could be facilitated by placing some 

 of the removed bark along the tops of the logs to prevent undue 



