PREFATORY NOTE vii 



so that their methods of entry and their vuhier- 

 able periods could become known. The develop- 

 ment of fungicides, especially Bordeaux mixture, 

 was a natural result of the realization that fungi 

 are the causes of most plant diseases. The newest 

 researches now attempt to correlate what Is known 

 of the life history of the parasite and of its manner 

 of entering the host with the facts learned as to 

 the relation of the weather to Infection, and to 

 plan the application of fungicides accordingly. 

 Another line of research Is the development of 

 the resistant types of crops, but this is for the 

 plant breeder, primarily. 



In the present book, the author attempts to 

 present. In a form capable of being understood 

 both by students and by agriculturists, a brief 

 discussion of each of the more important diseases 

 of the common field and garden crops. Of 

 necessity such a book cannot be complete as to 

 all diseases known on all crops. Indeed, such a 

 work would be undesirable and so bulky as to 

 be almost useless. The author has approached 

 the subject with a practical understanding of what 

 is wanted in such a book by the agriculturist 

 who frequently lacks the technical knowledge to 



