MANUAL OF TREE DISEASES 



CHAPTER I 



SEEDLING DISEASES AND INJURIES 



From the very beginning of the life of a tree, the seedling is 

 subject to many more or less serious diseases. Damping-off 

 may cause death, even before the tiny plant has grown above 

 the surface of the soil. Later, if damping-off is avoided, va- 

 rious blights are common in the seed- and transplant-bed. 

 Although many pathogenes are known to cause seedling dis- 

 eases, it is very difficult for the layman to identify the trouble 

 any more accurately than by the general symptoms of damping- 

 off or blight. Damping-off symptoms are mostly due to the 

 activities of specific soil-harbored fungi. Blight symptoms 

 may be produced by various rapidly spreading fungi, or by 

 adverse moisture and temperatm-e conditions. After a careful 

 comparison of the blight symptoms produced by environmental 

 conditions, with the usual symptoms caused by parasites, 

 the layman should be able to distinguish between these two 

 general types of seedling blights. In some cases, the seedlings 

 of certain kinds of trees are affected by well-known specific 

 leaf-, stem- or root-parasites which cause blight. These dis- 

 eases are described in the chapter on the diseases of the species 

 of tree affected. Otherwise, the damping-off and blights such 

 as sun-scorch, winter-drying and freezing-to-death of seedlings 

 of both coniferous and deciduous trees, are treated below. 

 B 1 



