UNITED STATES DEPARTMENT OF AGRICULTURE 



jr^?*^Vi. 



BULLETIN No. 722 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



October 22, 1918 



A STUDY OF HEART-ROT IN WESTERN HEMLOCK. 



By James R. Weir, Forest Pathologist, and Ernest E. Hubert, Scientific Assist- 

 ant, Office of Investigations in Forest Pathology. 



CONTENTS. 



Page. 



Introduction 1 



Present status of western hemlock in the 



trades 2 



Echinodontium tinctorium 3 



The fungus and its hosts. 3 



Geographic distribution 5 



The disease caused by Echinodontium 



tinctorium 6 



Outward signs of the disease 6 



General characteristics of the rot 9 



Areas studied and field methods used 11 



Page. 



Methods used in presenting data 14 



Infection age 1(3 



Relation of decay to site and to age 18 



Relation of decay to vigor, crown rating, size, 



and volume 22- 



Relation of decay to injury and to sporo- 



phores 24 



Theory of infection 30 



Discussion of results 31 



Methods of control 24 



Summary 36 



INTRODUCTION. 



From the fact that the experience and methods of the European 

 countries have been worked out and are at present practiced under 

 an entirely different set of conditions, forestry in America is con- 

 fronted with the necessity of formulating its own fundamentals as 

 regards forest organization, working plan, and general silvicultural 

 procedure in the virgin forests of the Northwest. Since a large 

 number of the basic principles of an ideal forest organization depend 

 upon a proper understanding and appreciation" of the progress of 

 decay in the forest and the general deterioration of the stand and of 

 individual trees, the problem is largely one of a pathological nature. 

 The need of reliable figures from which an adequate conception of 

 the loss to the forest through the death and disease of individual 

 trees or stands and through various other causes instrumental in 

 reducing the maximum annual increment is self-evident when any 

 attempt is made to establish a rotation or cutting age for any one 

 specieso It is necessary also to concentrate the collection of these 

 data upon a single tree species or upon a single type in order to secure 



63424°— 18— Bull. 722 1 



