xvi PREFACE 



tural conditions of the host. In other 

 words, the attack of most plant diseases 

 depends on some weak point in the cul- 

 tural methods which has weakened the 

 host at some phase in its life history. If 

 we accept the definition of disease as any 

 serious deviation from the normal; and 

 admitting as we do that proper cultural 

 conditions are necessary to maintain the 

 proper balance of health of a plant, it be- 

 comes self evident that a discussion of 

 culture requirements goes hand in hand 

 with any discussion on plant diseases. To 

 be more specific, it is very apparent that 

 the man who understands plant life in all 

 its aspects will be in a much better posi- 

 tion to also cope intelligently with any 

 problem of disease which may confront 

 him at any time. Since growers as a rule 

 must be their own plant doctors they can- 

 not be provided with too much informa-^ 



