UNITED STATES DEPARTMENT OF AGRICULTURE 

 BULLETIN No. 722 



Contribntion f^om the Bureau of Plant Indnatry 

 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 

 ScientilSc Assistant, Office of Investigations in Forest Pathology 



CONTENTS 



Introdaction .....^ 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 ...-. 16 



Relation of Decay to Sigte and to Age . IS 

 Relation of Decay to Vigor, Croivn Rat- 

 ing, 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 . 34 



Summary ............ 36 



WASHINGTON 

 GOVERNMENT PRINTING OFFICE 



1918 



