. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. I BULLETIN No. 934 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief. S^fr'^LTU 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 Corticium vagum 27 Fusarium spp 34 Pythium debaryanum 35 • Kheosporangium aphanider- matus 55 Phytophthora spp 59 Miscellaneous phycomyeet
. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. I BULLETIN No. 934 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief. S^fr'^LTU 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 Corticium vagum 27 Fusarium spp 34 Pythium debaryanum 35 • Kheosporangium aphanider- matus 55 Phytophthora spp 59 Miscellaneous phycomyeetes 61 Other fungi 64 Relative importance of the damping- off fungi on conifers 65 Page. Damping-off fungi as causes of root- rot and late damping-off__ 70 Relation of environmental factors to damping-off 73 Density of sowing 74 Moisture and temperature factors 75 Chemical factors 79 Biologic factors 82 Acknowledgments 86 Summary 86 Literature cited 91 DAMPING-OFF IN GENERAL. Damping-off is the commonest English name for a symptomatic group of diseases affecting great numbers of plant species of widely separated phylogenetic groups. It is commonly used for any disease which results in the rapid decay of young succulent seedlings or soft cuttings. Young shoots from underground rootstocks may also be damped-off before they break through the soil (66).x The same term is even used for diseases affecting the prothallia of vascular crypto- gams (2). The name apparently originated in the fact that the dis- ease is usually most prevalent under excessively moist conditions. In those cases in which the disease becomes serious without the pres- ence of unusual amounts of moisture the term is a misnomer. It is, however, so thoroughly established in practical use that it would be impossible, even if desirable, to establish any other name. 1 The serial numbers in parentheses refer to " Literature cited," at the end of this bulletin. 19651°—Bull. 934—21 1. Please note that the
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