MARKET DISEASES OF VEGETABLES. 59 



line and in the more irregular plane of separation between 

 killed and sound tissue. At certain seasons, it may be very 

 difficult to make this differentiation positive without rather 

 careful inspection of car lots. Freezing injury, however, 

 should be accompanied by other unmistakable symptoms. 



Scald of potato is probably caused by exposure of newly 

 dug tubers to the hot sun in the field. 



Scald is of the highest importance from the market point 

 of view. The killed tissue is very subject to the attacks of 

 rot-producing organisms such as Fusarium and especially 

 the bacteria of slimy soft rot. In the Chicago market in the 

 summer of 1918, there were enormous losses due to slimy 

 soft rot following scald in shipments of potatoes from the 

 South and the entire Mississippi Valley. 



It is not advisable to ship potatoes showing scald because 

 of their extreme predisposition to slimy soft rot during 

 transit. 



POTATO: SALT INJURY. 



Cause : Contact of potatoes with the floor or walls of a 

 car in which fertilizers, salt, or salted hides have been 

 shipped. 



Usually the side of the potato in contact with the floor or 

 wall is flattened, and the injured tissue is soft and flabby 

 and at times semi-watery. At times the injured tissue is firm 

 and leathery. Before the air has free access to the tissue it 

 usually is colorless. After a short exposure to the air if not 

 infected the injured tissues become brown to black, and 

 begin to dry out. The exterior of the injured region gener- 

 ally is black. Frequently the injured tissue has a distinct 

 salty taste, and salt injury may be thus diagnosed. 



Tubers affected with salt injury are predisposed to slimy 

 soft rot, and generally become infected and soupy if not 

 removed promptly from the car. 



POTATO: SUNBURN. 



Cause : Exposure of tubers to light, either in the field, or 

 during harvest, shipment and storage. 



Sunburn is marked by a green discoloration of the surface 

 layers, and in severe cases, of the interior portions of the 

 tuber. 



Sunburn occurs in potatoes of all varieties upon prolonged 

 exposure to the light. It is common in eastern stock shipped 

 in midsummer. 



Affected stock is bitter and unfit for food. 



POTATO: BRUISES, CUTS, AND SPLITS. 



Cause: Mechanical injury. 



Bruises may be superficial or internal. The most common 

 type of bruise occurs in immature potatoes whose tissues 

 are very tender and crisp, and consequently are easily 

 broken either by pressure or by friction. Often an immature 



