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. 
