PREFACE 



The present edition of this text-book is designed primarily 

 for college students, but it is hoped that it may serve also 

 as a useful handbook for others who may wish to recognize 

 plant diseases or to apply treatments. It aims to give a 

 comprehensive view of the field and its importance, with 

 diagnostic symptoms and suggested treatment of all of the 

 more important diseases prevalent on the crop plants of the 

 continental United States with brief notes or mere mention 

 of those less serious. A few of the more important diseases 

 not of the United States are also discussed briefly. Diag- 

 nostic characters are limited in the descriptions to those that 

 may be recognized without the aid of the microscope. For 

 further discussion of morbid histology, or of the morphology 

 of the parasites concerned, the reader is referred to other 

 books on these subjects. Descriptions and discussions of 

 treatment are as full as the space admits and the reader who 

 desires more complete information is referred to the pertinent 

 literature cited. 



Since conditions are so diverse as to geographic loca- 

 tion, climate, and soils the treatment here suggested must 

 be more or less general. Crop growers should in all cases 

 endeavor to secure from the nearest Agricultural Experi- 

 ment Station the information best applicable to local con- 

 ditions. 



The segregation of certain diseases under the caption 

 "Minor diseases" is arbitrary and it is quite possible that 

 diseases here included may locally or seasonally be of major 

 importance, and conversely that certain major diseases may 

 be of but minor importance. The aim, however, is to in- 

 dicate to the student those which in general are less wide- 

 spread or less likely to be serious. Ample cross references are 



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