UNITED STATES DEPARTMENT OF AGRICULTURE 



| BULLETIN No. 871 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



SL&*^&L 



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 



rotal-loss factors 2 



Method of collecting data 4 



Secondary rots 7 



rhe 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 (Libocedrus 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). * 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 (17, 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- 



1 The serial numbers in parentheses refer to " Literature cited " at the end of the bulletin. 

 182803°— 20— Bull. 871 1 



