. Bulletin of the Department of Agriculture. Agriculture. riv. insects.' UNITED STATES DEPARTMENT OF AGRICULTURE. f BULLETIN No. 255 mmh Contribution from the Bureau of Entomology \J^J^- JZPp'^&U I- O. HOWARD, Chief .yC^^Wi. Washington, D. C. PROFESSIONAL PAPER July 22, 1915. DOUGLAS FIR PITCH By Josef Brunnee, 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 {Pseudotsug
. Bulletin of the Department of Agriculture. Agriculture. riv. insects.' UNITED STATES DEPARTMENT OF AGRICULTURE. f BULLETIN No. 255 mmh Contribution from the Bureau of Entomology \J^J^- JZPp'^&U I- O. HOWARD, Chief .yC^^Wi. Washington, D. C. PROFESSIONAL PAPER July 22, 1915. DOUGLAS FIR PITCH By Josef Brunnee, 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 taxlfol'/a). 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 larva? cf the Douglas fir pitch moth {Sesia novaroensh 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 Avhat 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 elicted the fact that no accurate record is kept of the extent of
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