APPLE SCALD. 27 



the flesh, but it detracts from the appearance of the fruit and reduces 

 its commercial value. This trouble is commonly called "apple scald." 

 It may appear in fruit held in common or in cold storage. 



The exact nature of scald is not well understood, though apple men 

 have many theories by which its appearance is popularly explained. 

 The most common theory gives rise to the name of scald — that is, the 

 brown, cooked appearance is thought to be due to the overheating of 

 the fruit when it is stored, or to a temperature too low for the variety, 

 or to picking the fruit when too ripe; and other matters relating to the 

 growth and handling of the fruit are thought to develop it. 



As the scald is an important commercial problem it has been con- 

 sidered from several standpoints in the fruit-storage investigations of 

 the Department. The nature of the scald, the influence of the degree 

 of rnaturhVy of the fruit when picked, of commercial methods of hand- 

 ling, of fruit wrappers, of different temperatures, and of cultural 

 conditions on its development are among the problems investigated. 



NATURE OF THE SCALD. 



Apple scald is not a contagious disease. According to Dr. A. F. 

 Woods, Pathologist and Physiologist of the Department of Agricul- 

 ture, it is a physiological disturbance not connected in any way with 

 the action of parasitic or saprophytic organisms such as molds or bac- 

 teria. Briefly, it is the mixing of the cell contents or premature death 

 of the cells and their browning by oxidation through the influence of 

 the normal oxidizing ferments of the cell. There are many conditions 

 which influence the development of this trouble. It appears to be 

 closely connected with the changes that occur in ripening after the 

 fruit is picked, and is most injurious in its effects as the fruit approaches 

 the end of its life. Several of the factors that influence it will be dis- 

 cussed. Plate V shows the scald on a Rhode Island Greening apple. 

 The cross section shows that scald does not extend deep into the flesh. 



INFLUENCE OF MATURITY OF THE FRUIT ON SCALD. 



The scald always appears first on the green or less mature side of an 

 apple, and if the fruit is only partly ripe it may spread entirely over 

 it; but the portions grown in the shade and undercolored are first and 

 most seriously affected. The upper figure in Plate I (frontispiece) 

 .-hows the distribution of scald on an immature York Imperial apple. 

 The apples that are more mature and more highly colored when picked 

 are less susceptible to injury, and the side grown in the sunlight 

 may remain entirely free from it. The lower figure in Plate I shows 

 a w T ell-colored York Imperial apple and its freedom from the scald is 

 noticeable. 



When the apple crop is picked before it is mature the fruit is more 

 ' susceptible to scald than it would have been later in the season. The 



