A systematic study of the storage diseases of apples includes the consideration of two general groups: (a) the functional, and (b) the parasitic diseases. Although most kinds of parasitic diseases are seldom found on good grades of apples, occasionally some of these escape inspection and develop considerably on ripe, fruit in storage. The fruit grower who is concerned with producing sound fruit is familiar with such parasitic diseases as apple scab, apple blotch and cedar-apple rust. The fruit dealer, storage operator and consumer, on the other hand, more frequently come in contact with the functional diseases such as Jonathan spot, apple scald, bitter pit and breakdown.