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-OflF 
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 
