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 conditions is also exhibited by fungi on other crops, so that the freedom 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 unsuccessful.
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 resistant to indigenous fungi than to introduced fungi. European stock may therefore be satisfactorily grown in conditions favorable to introduced fungi, like those causing the Powdery Mildew 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 the attacks of the Black Rot and Downy Mildew pathogenes than when besieged with Powdery Mildew and anthracnose fungi. From these facts it is clear that the pedigree of a variety is an essential indication of the probable susceptibility to disease.