Canadicfii Forestrx Journal. June, IQ16. 



563 



Ravages of Insects in Canadian 

 ^^-^— Forests =.==..^..^^— ^= 



An Expert's Discussion of the Enormous Damage Annually 

 Caused to Standing" Timber and Logs 



By J. M. Sivaine. 

 In Charge of Forest Insect Inzrstigation, Entomological Branch, Ottai<'a. 



"The insect injury to Canadian Forests certainly amounts to many 

 millions of dollars annually, probably varying between twenty-five and 

 seventy-five millions." 



Injuries by forest insects, through 

 which trees are weakened or killed, 

 logs are reduced in value or render- 

 ed unfit for use, and forest products 

 ruined by boring grubs, are causing 

 a very great annual loss in Canadian 

 forests and to consumers of our for- 

 est products. All our forest areas 

 are subject to such losses, although 

 not all to a like degree. 



It is impossible to make an exact 

 or even very valuable estimate of 

 the money value of the losses in- 

 curred in this way. ■Much of the in- 

 jury occurs in northern or mountain 

 areas, or other sections beyond the 

 present boundaries of the timber 

 limits, where the young growth is 

 of more importance than mature 

 timber. Timber killed by insects 

 may enable fires to obtain great 

 headwaA^ and thus contribute to- 

 ward more extensive injuries. Seri- 

 ous injuries to reproduction are 

 quite as important as the destruc- 

 tion of grown timber, but the money 

 value of the loss can be estimated 

 only very roughly. The majority of 

 our fires, like extensive bark-beetle 

 outbreaks, kill the timber without 

 destroying or greatly injuring it for 

 lumber. The lumber in these stand- 



ing trees would be sound and good 

 for many years, unless burned 

 again, were it not for the insects, 

 which almost immediately proceed 

 to riddle the trunks with holes, and 

 the parasitic fungi thereby given 

 access to the inner layers of wood. 

 The destructive agent in such cases 

 is not the fire but the boring grub, 

 and the prevention or quelling of 

 ground fires is merely a very eft'ec- 

 tive method of forest insect control. 

 The outline to be given will make it 

 plain that the annual loss in Can- 

 adian forests from insect injuries is 

 very great. In American forests it 

 has been estimated that "the amount 

 of insect killed and damaged timber 

 left in the woods, plus the reduction 

 in value of that utilized to be 

 charged to insects is not far from an 

 equivalent of 10 per cent of the 

 value of the annual output of forest 

 products of all kinds in the rough." 

 This would make the annual loss 

 from insect depredations in United 

 States forests approximately of the 

 value of S 100.000.000. 



Canada's Enormous Loss. 



The insect injury to Canadian for- 

 ests is probably somewhat less than 



