UNITED STATES DEPARTMENT OF AGRICULTURE 

 BULLETIN No. 934 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 16, 1921 



DAMPING-OFF IN FOREST NURSERIES 



By , . 



CARL HARTLEY, formerly Pathologist, Office of 

 Investigations in Forest Pathology 



CONTENTS 



Page 



Damping-Off in General 1 



Damping-Off of Conifers ........ 7 



Causal Fungi •. 27 



Relative Importance of the Damping-Off 



Fungi on Conifers 65 



Damping-Off Fungi as Causes of Root- 

 Rot and Late Damping-Off 70 



Relation of Environmental Factors to 



Damping-Off 73 



Page 



Density of Sowing 74 



Moisture and Temperature Factors ... 75 



Chemical Factors 79 



Biologic Factors 82 



Acknowledgments 86 



Summary 86 



Literature Cited 91 



WASHINGTON 

 GOVERNMENT PRINTING OFFICE 



1921 



