UNITED STATES DEPARTMENT OF AGRICULTURE 
SWTSfL 
BULLETIN No. 871 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
■fZ&^J-u 
Washington, D. C. 
PROFESSIONAL PAPER 
November 10, 1920 
THE DRY-ROT OF INCENSE CEDAR. 
By J. S. Boyce, Assistant Pathologist, Office of Investigations in Forest Pathology. 
CONTENTS. 
Page. 
Importance of incense cedar 1 
Total-loss factors 2 
Method of collecting data 4 
Secondary rots 7 
The dry-rot , 8 
Page. 
Application of results 49 
Relative importance of dry-rot 49 
Control of dry-rot 49 
Summary 55 
Literature cited 57 
IMPORTANCE OF INCENSE CEDAR. 
Incense cedar (Lihocedrus decurrens) is of considerable economic 
importance on the Pacific coast. The available supply of this species, 
which never occurs alone but always in mixture, chiefly with yellow 
pine, Jeffrey pine, sugar pine, Douglas fir, and white fir, averaging 
about 8 per cent of the stand, although often forming as high as 30 
to 50 per cent, is estimated at 11 billion feet, 10 billion of which 
occurs in California (17, pp. 9-10). 1 That the wood is very valuable 
for special purposes on account of certain qualities has been clearly 
pointed out by Mitchell (17, pp. 2-9) recently and was mentioned by 
Von Schrenk (26, p. 69) 20 years ago. However, in spite of the well- 
known value of the wood, only about 30 million feet is cut annually 
in California. The stumpage rate is low and the price for the finished 
product often little more than pays the cost of logging and manufac- 
ture, according to Mitchell (1 7, p. 6) . 
The reason for this is obvious. The heartwood of incense cedar is 
commonly rendered totally worthless by the so-called dry-rot caused 
by Polyporus amarus. An idea of the quantity of timber rendered 
unmerchantable by this dry-rot may be obtained from Mitchell's 
statement (17, p. 3) that so common is this defect that it is the usual 
practice to cut estimates of this species from 30 to 50 per cent on ac- 
i The serial numbers in parentheses refer to " Literature cited " at the end of the bulletin. 
182803°— 20— Bull. 871 1 
