. Bulletin of the Department of Agriculture. Agriculture; Agriculture. ^J^-'^fsj-u 1 BULLETIN No. 255 Contribution from the Bureau of Entomology L. O. HOWARD, Chief. jr&?'<&j-<~ 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 here
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. ^J^-'^fsj-u 1 BULLETIN No. 255 Contribution from the Bureau of Entomology L. O. HOWARD, Chief. jr&?'<&j-<~ 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 ; 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 Le
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