4 MANUAL OF FRUIT DISEASES 



well apply to other varieties. And finally, the evolution of the 

 pathogene often keeps pace with that of the host. With the 

 development of resistant or immune strains or varieties come 

 eventually strains of the pathogene capable of attacking them. 



While this disease is generally known to American growers as 

 scab or apple-scab, it is frequently called the fungus. In 

 Australia and South Africa it is spoken of as black-spot. The 

 disease is unquestionably of foreign origin and probably has 

 been peculiar to the apple since that fruit was brought under 

 cultivation. The first records came from Europe in 1819. It 

 was subsequently reported from France in 1829, having since 

 attracted attention in nearly all countries where apples are 

 grown. The disease was first recorded in America from Penn- 

 sylvania and New York in 1834. For a time apple-scab was 

 reported to be absent in the apple-growing valleys of the Pacific 

 Coast and Rocky Mountain states, but within the last ten years 

 it has in those regions become an important factor in apple- 

 culture. While now having a general geographical range over 

 the United States wherever the apple is grown, it is most destruc- 

 tive in the cooler regions of eastern and northern United States, 

 the northern Mississippi Valley, the northern Pacific Coast 

 regions, in the apple-sections of Idaho and Montana, and in 

 the mountainous regions of Virginia, Arkansas, and certain other 

 southern states. 



Apple-scab may be said to be the most important disease of 

 this fruit in northern United States and in southern Canada. 

 In the Mississippi Valley, north to central Illinois, Indiana and 

 Ohio, other diseases, especially bitter-rot and apple-blotch, are 

 close competitors, and in many seasons are far more important 

 than scab. It has been estimated that the average annual loss 

 in New York State due to failure to spray the apple-crop is not 

 less than three millions of dollars, and for the United States there 

 is a corresponding loss of over forty millions. Not infrequently 

 there is a total loss from failure of fruit to set due to this disease. 



