CONTROL OF PLANT DISEASES 



473 



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Diagram 2. Showing Inter-state Migration of some Important Diseases. 

 1, asparagus rust : New Jersey, 1896 ; South Carolina, 1897 ; Michigan, 1898 ; 

 Illinois, 1899 ; Dakota, Nebraska, Texas, 1900 ; California, 1901. 2, fire blight : the 

 Hudson, 1792 ; California, 1895-7, 3, peach yellows : Philadelphia, 1806 ; Ontario, 

 Michigan, Illinois, Maine, 1886. 



first encroachment in South Carolina and an agressive campaign 

 against it with remedies which had recently proved efficient against 

 smuts of other cereals checked it and completely subjugated it, so that 

 it is no longer known in the Palmetto State. The cucumber mildew, 

 which causes blanched spots on the leaves and often entire loss of crop, 

 has rendered unprofitable the culture of cucumbers and cantaloupes in 

 many sections. The two grape mildews are notorious in their destruc- 

 tiveness and have driven vineyardists to large expense in spraying or 

 sulphuring. 



Perhaps the most striking importation is that of the potato wart. 

 This disease causes large unsightly knotty excrescences on the potato, 

 rendering them worthless. It was first reported in England in 1902, 

 found its way to Newfoundland, and it is known that two consignments 

 of Newfoundland potatoes, probably infected, were shipped last year, 

 one to New York, one to Boston. The spread of this disease in our 

 states is an event to be predicted with confidence, especially as many 

 sections of the country depend upon New England for their seed 

 potatoes. 



The large increase in aggressiveness of plant diseases has been met 

 by a campaign of increased knowledge leading to new modes of subju- 

 gation. Though a few plant diseases are mentioned in early writings, 

 (II. Chronicles 6-28, Shakespear's King Lear, III., Sc. 4; I. Kings 

 8-37; Moses 28, 22), the real significance of their presence, their na- 

 ture and causes may be said to have been first recognized between the 



