vi Preface 



given to render the inforniatiou more accessible and to avoid 

 repetition. 



The common names selected are those that are in general 

 use. 



Diseases due to insects comjirise a group which involves 

 knowledge of the classification of insects and of their life- 

 habits. Such diseases are set aside in the special field of 

 the Entomologist and are not here treated. The diseases 

 due to adverse inanimate environmental conditions, the 

 sickening of plants due to lack of soil fertility, to excess of 

 some element, to overabundance or lack of water or to im- 

 proper physical condition of soil, etc., are recognized as 

 properly belonging in the field of Agronomy and are treated 

 in this book only in exceptional cases. 



During the decade that has elapsed since the publica- 

 tion of the first edition there have come into prominence 

 in the United States numerous diseases at that time un- 

 known in America. Therefore the present edition includes 

 discussion of several scores of diseases of major importance, 

 some of minor importance, as well as many modifications of 

 treatment that did not appear in the earlier edition. 



The author desires to express his especial thanks for 

 aid in the preparation of this volume as follows: To R. 

 J. Haskell of the Plant Disease Survey of the U. S. Depart- 

 ment of Agriculture, who has kindly read the proof with 

 particular reference to the usage of common and scientific 

 names and as to the estimates of losses and statements 

 regarding geographic distribution; to H. W. Anderson of 

 the University of Illinois for valuable aid in the preparation 

 of the sections treating of fruit disease; to E. C. Stakman 

 of the University of Minnesota in connection with the cereal 

 diseases; to G. L. Peltier of the Alabama Experiment 

 Station and W. A. Ruth of the University of Illinois for the 

 preparation of special articles. 



F. L. Stevens. 



Urbana, Illinois, 

 August, 1920. 



