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the spread of fungous diseases of the bark and wood of the main trunk 

 than do such diseases to the spread and ravages of insects. 



The most striking example of insects contributing to the spread of 

 fungous diseases was observed in the white fir throughout the region 

 traversed; the heartwood of which is commonly rendered worthless 

 by decay as the result of wounds in the living bark made by Scolytus 

 bark beetles. 



Interrelations of forest fires, insects, and fungous diseases. — It will be 

 seen from the foregoing references to the relation of forest fires to 

 insect ravages, insects to forest fires, diseases of trees to insects, and 

 insects to fungous diseases, that there is a close interrelation, and, to a 

 certain extent, interdependence of all of these factors in the destruc- 

 tion of valuable forest products. While I had made some observations 

 along this line in the forests of West Virginia, I had little conception 

 of the magnitude and importance of the problem previous to my trip 

 through the forests of the Northwest, where quite conclusive evidence 

 was found that had it not been for previous depredations by insects 

 and consequent rapid decay of the standing and felled timber, far less 

 destruction by forest fires, or need for trouble and expense in efforts 

 toward the prevention and control of this prevalent evil, would have 

 occurred. It was also evident from the conditions observed in some 

 sections that practical means of greatly mitigating the destructive 

 effects of these separate and combined causes of prevailing troubles 

 could be had through a better knowledge of some of the leading 

 features of this problem. 



CONSIDERATION OF PREVENTIVES AND REMEDIES. 



The object of the trip was to study insect enemies of forests and 

 causes of prevalent unhealthy conditions, rather than the subject of 

 preventives and remedies. Indeed, much additional and detailed 

 investigation relative to the life histories and habits of the more 

 destructive enemies, and of the conditions which affect them is neces- 

 sary in order to obtain evidence on which to base reliable conclusions. 



The fact that the Western destructive pine-bark beetle is attracted 

 to girdled trees, suggested girdled and felled trap trees as a practical 

 method of preventing and checking destructive outbreaks of this and 

 other insects with similar habits, especially in forest reserves, and I 

 think some experiments should be conducted in order to determine 

 whether or not this would prove effectual. 



The discontinuance, so far as possible, of the common practice of 

 settlers and farmers girdling pine and spruce trees and leaving them 

 standing in the clearing from year to year was suggested by the con- 

 ditions observed as a most important precaution against the multipli- 

 cation and destructive outbreaks of certain dangerous enemies of 

 conifers. On the other hand if such girdled conifers could be felled 



