SB 608 
c" v B i MITED STATES DEPARTMENT OF AGRICULTURE 
Wash'r.gbr, D. C. _▲ July 21, 1923 
A STUDY OF DECAY IN DOUGLAS FIR IN THE PACIFIC NORTHWEST. 
By J. S; Boyce, Pathologist , Office of Investigations in Forest Pathology , Bureau 
of Plant Industry. 
CONTENTS. 
Page. 
Importance of decay in Douglas fir. 1 
Method of collecting data. 2 
Fungi causing decay. 3 
Position of the decays in the tree. 4 
Relative importance of the decays. 4 
Mechanical injuries. 5 
Page. 
Entrance of the decays. 7 
Indications of decay In living trees. 10 
Extent of incipient decay. 15 
Summary. ig 
Outlook.17 
Literature cited.19 
IMPORTANCE OF DECAY IN DOUGLAS FIR. 
Douglas fir is the most important timber tree in the Pacific North¬ 
west, covering, as it does, the greater part of the foothills and lower 
slopes of the Cascade Mountains and the Coast Range in practically 
pure stands of great density. The stand of this species in Oregon and 
Washington is estimated at 505 billion feet ( 6 , p. 23), 1 or nearly one- 
fourth of the remaining merchantable timber in the United States. 
The loss through decay in Douglas fir in this region is very high. 
While some overmature stands are relatively sound a loss of 20 per 
cent in such stands is not uncommon. In certain cases the cull figure 
may reach 50 per cent or more, so high that in timber on difficult 
ground it becomes impossible to log at a profit. It is only in young 
stands of second growth that Douglas fir is uniformly sound. Plate 
I shows defective trees left uncut after logging in an overmature 
stand. In this instance about 25,000 feet board measure per acre 
was left standing. Where clear cutting is practiced numerous logs 
and entire trees remain on the ground after logging, absolutely worth¬ 
less on account of decay. This is illustrated in Plate II. Practically 
all the large pieces were left because of rot. 
Recognizing the importance of this question, foresters and lumber¬ 
men in the Douglas fir region have repeatedly felt the need for exact 
information on decay in Douglas fir. This bulletin presents obser¬ 
vations by the writer and the results of a preliminary study. 1 2 
1 The serial numbers (italic) in parentho-ej refer to “ Literature cited ” at the end of this bulletin. 
2 This study was made in the summer of 1917 under the direction of Dr. E. P. Meinecke. To him the 
writer is indebted for supervision and assistance throughout the course of the field work. The project 
was a cooperative one avith the Forest Service of the United States Department of Agriculture, and 
acknowledgment is made to Forest Examiner F. B. Kellogg for his part in collecting the field data. A 
much more detailed study of decay in Douglas fir is now in progress, but will not be completed for several 
years. 
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42198—23-1 
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