Proceedings, IIJ"^:! 185 



\v;itiT \'Mll('y. near Mcrritt, wliere a very activt' infestation is now in 

 projii-ess. It is evident that the yellow pine in this wliole forest between 

 Princeton and Kamloops is threatened with ruin by these outbreaks, 

 and that our control operations, now being conducted through the co- 

 operation of the British Columbia Forest Branch, the Dominion Forestry 

 Branch and the Dominion Entomological Branch, offer the only hope of 

 saving- it. Fortunately they promise to be successful. 



There are three types of .I)ark-beetle attack : 



1. An endemic or so-called "normal" infestation exists in almost 

 all forests, in which over-mature or weakened trees or their parts, are 

 killed here and there from bark-beetle attacks. 



2. Sporadic outbreaks frequently develop in the neighbourhood of 

 slash, windfalls or light burns, particularly in bodies of weakened timber, 

 but subside before many trees are killed. 



3. Epidemic outbreaks resultinu- from a more sci-ious disturbance 

 of Nature's ('(juilibrinm. from either natural or artificial causes, spreading 

 rapidly through the forest, killing great numbers of trees in a very short 

 period. 



An endemic infestation need cause little concern, altliougii it effects 

 considerable loss when this is computed over a jieriod of years, and it 

 is, of course, from this normal infestation that the serious outbreaks 

 develop. The sporadic outbreaks, although small, may be important in, 

 stands of valuable timber, and may develop, if not controlled, into the 

 more serious epidemic type. The epidemic outbreak is a serious matter, 

 often killing Oo'/i <if the timber stand, in certain tree species, in the 

 short period of five or six years. Control measures for epidemic out- 

 breaks should be undertaken with tlie least possible delay, under the 

 direction of a competent forest entomologist. 



It a]ipears prol)able that serious bark-beetle outbreaks usually 

 devehip through some notable distui'bance of the natural conditions in 

 the forest, such as windfalls over large areas whei'e man_y trees are 

 Idown down, fires caused by lightning, or through human agency, such 

 as careJesseness with fire, lumbering operations, or slashings of any 

 description. 



In windfalls and fires, we have conditions produced in whieli the 

 bark-beetles are not hampered by the resistance of the healthy trees. 

 The bark-beetles breed freelj- under these conditions and often start 

 outbi-eaks as a result, immediately following the fire or heavy windstorm. 



In logging operations we have a much more prevalent cause of 

 epidepiics. The immense amount of fresh slash, in tiie form of tops and 

 cull logs, affords an ideal breeding ground for the destructive bark- 

 beetles. The method of logging in the winter and not in the summer 

 has been especially favourable to attack upon the standing timbei-. The 

 beetles, completing their life-cycle in the freshly cut material, emerge, 



