2 MANUAL OF FRUIT DISEASES 
often overlooked, bring the total dollar loss far above the fancy 
of fruit-growers. It would be difficult to set a figure which 
would represent, accurately or even approximately, the losses 
incurred each year. A few well-known examples may be tabu- 
lated in order that some notion of the gravity of this source of 
waste may be gained. One authority estimates from reliable 
figures that there is an average annual loss of more than 
$40,000,000 in the United States due to the failure to spray 
apples. Such devastation, of course, is brought about both by 
diseases, chiefly caused by fungi, and by insects, and it would 
be quite impossible to assign the losses to the proper offender 
in every case. Individual examples of losses follow: (1) bitter- 
rot wrought damage to the apple-crop of the United States in 
1900 amounting to $10,000,000 ; (2) black-rot canker induces an 
annual loss of $750,000 in New York; (3) blotch is said to have 
caused in one county in Arkansas, in 1906, a loss of $950,000 ; 
(4) rust, in 1912, was so destructive in West Virginia that actual 
fruit-losses ranged from $2000 to $3000 an orchard. 
Apple diseases are important because of the nature of the 
injury inflicted. Losses do not stop with damage to, or destruc- 
tion of, the fruit. Blossoms may be killed ; the set of fruit may 
be dropped; woody parts including twigs, limbs, trunks and 
roots may be blighted, cankered or rotted; leaves may be 
spotted and even dropped prematurely. It is indeed fortunate 
that most of these types of troubles may be reduced to a point 
where fruit-growing may still be carried on with pleasure and 
profit. 
Most apple diseases are caused by fungi, but a few result from 
the detrimental action of bacteria, and certain environmental 
factors. The best-known, the most cosmopolitan, and the most 
important of apple troubles generally is without question the 
fungous disease known as apple-scab. Other diseases and ‘in- 
juries affecting this fruit are discussed somewhat in order of 
their general prevalence and importance. 
