UNITED STATES DEPARTMENT OF AGRICULTURE 



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1 BULLETIN No. 255 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



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Washington, D. C. 



PROFESSIONAL PAPER 



July 22, 1915. 



DOUGLAS FIR PITCH MOTH. 



By Josef Brunner, 

 Entomological Assistant, Forest Insect Investigations. 



NATURE AND CAUSE OF DAMAGE. 



Pitch seams, gum check, windshake, or whatever these defects may 

 be termed locally, have ever been recognized as a serious depreciating- 

 factor in the utilization of Douglas fir {Pseudotsuga taxifolia). 

 These defects have heretofore been variously charged to windshake 

 (mechanical strain), lightning, frost, blazes, fires, and various other 

 unavoidable causes, but investigation of the trouble and its causes 

 makes it evident that the work of the larvee cf the Douglas fir pitch 

 moth {.Sesia novaroensis Hy. Edw.) is the primary cause of a large 

 percentage of these defects. 



DISTRIBUTION AND EXTENT OF DAMAGE. 



In the northern Rocky Mountain and Pacific coast regions it has 

 been definitely determined that the Douglas fir pitch moth is re- 

 sponsible for at least 90 per cent of this damage. 



A very similar larva, 2 found working in Douglas fir in the south- 

 ern Rocky Mountain district, makes it quite certain that the same 

 species is responsible for what similar depreciation in timber value 

 may be existing there. 



The loss occasioned by the work of this class of insects causes the 

 difference in price between absolutely clear lumber and the lower 

 grades or " dimension stuff." These insects work in the portion of the 

 trunk which later clears itself of branches; hence only logs are 

 affected which, were it not for previous infestation by them, would 

 yield only the better grades of lumber. 



Extensive correspondence with mill managers in various parts 

 of the northern Rocky Mountains and Pacific coast range has dieted 

 the fact that no accurate record i Kept of the extent of the prevalence 



- Is My. Kdw. ; order Lepidoptera, family Seslidir, Identification bj Mr. 

 B 

 • The in-.'-i-i from the outhern Rocky Mountains, after the rearing uf three specimens, 

 • la not ai in imln. 



Interest to i ntomologji ts m n '■nnirii.ni [on io i belr (special tj , 

 .■mil to 'i manufai ■ busim proposition 



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