PREFACE 



The steadily accumulating knowledge of the diseases of 

 trees in the United States has never been brought together and 

 made available to the general public. The intention of this 

 Manual is to describe and suggest means of control for the 

 tree diseases that have been most studied- Much remains to 

 be learned about many of these diseases, and still many more 

 have never been investigated. Therefore, in the treatment of 

 this subject there are many unavoidable limitations which the 

 trained reader will perceive. The diseases of fruit-trees, and of 

 field and vegetable crops, have received the attention of plant 

 pathologists in most parts of the country for many years. 

 The results of these investigations have been made available 

 to the growers of these crops in various ways. On the other 

 hand, the diseases of forest, shade, and ornamental trees have 

 been largely, neglected until very recently. 



Tree diseases cause enormous losses in the large tracts of 

 forests on which we depend for timber. The timber owner 

 has been slow to adopt the fundamentals of scientific forest 

 practice, and so far methods for the control of forest-tree 

 diseases have not begun to operate in reducing losses. The 

 owners of shade and ornamental trees are constantly con- 

 fronted with diseases which they wish to control. They have 

 become accustomed to controlling insects, but the funda- 

 mentals involved in the appearance of a disease and the meas- 

 ures necessary to protect trees from further damage are largely 

 puzzling to them. 



An understanding of the cause of disease is essential to the 

 undertaking of adequate control measures. That the tree is 



