CHAPTER IX 

 GRAPE DISEASES 



IN most regions of grape-culture, the vine is as much subject 

 to destructive diseases as any other of the less important fruits. 

 But on the Pacific slope vines are notably free from fungous 

 troubles, owing to the light rainfall of the summers. This 

 dependence of disease-producing organisms on weather condi- 

 tions is also exhibited by fungi on other crops, so that the free- 

 dom from grape-disease in the region mentioned is not peculiar. 



The serious attention of American plant pathologists was 

 not given to grape diseases prior to 1887. In earlier days 

 these troubles were so detrimental to grape-production that 

 efforts to grow this fruit, almost without exception, were un- 

 successful. 



Grape-culturists, in America and Europe alike, are prone to 

 censure each other for their imported troubles. But it should 

 be remembered that while the powdery-mildew and the an- 

 thracnose fungi were being sent to us by Europeans, the black- 

 rot and downy-mildew pathogenes were carried from the United 

 States to European vineyards. A knowledge of these historical 

 facts has a practical application in the control-program. For 

 it is now well-known that native fruit-varieties are more re- 

 sistant to indigenous fungi than to introduced fungi. European 

 stock may therefore be satisfactorily grown in conditions favor- 

 able to introduced fungi, like those causing the powdery-mil- 

 dew and anthracnose, but such stock is highly susceptible to 

 black-rot and downy-mildew. Similarly, it may be expected 

 that varieties native with us will succumb less readily under 



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