MARKET DISEASES OF VEGETABLES. 53 



Brown rot may be followed by slimy soft rot as a result 

 of which large cavities are formed in the interior of the 

 tuber. The decayed tissue often is so viscous that it can be 

 pulled like very soft taffy. 



Slimy soft rot is prevalent as a surface rot in potatoes 

 shipped from Florida, Louisiana and Texas. It is favored 

 by wet, hot conditions in the field, in transit or in storage. 

 After the rot has once started, the temperature is of less 

 importance than the humidity. This rot occurs also in 

 northern potatoes. Tubers affected with black-leg or with 

 scald or freezing injury are predisposed to slimy soft rot. 

 In fact, slimy soft rot commonly follows freezing injury if 

 the temperature after thawing is high enough to permit the 

 growth of the bacteria. 



The control measures are careful sorting of stock which 

 has been subjected to unfavorable conditions before it is put 

 into transit or storage, and improvement of handling meth- 

 ods to avoid wounds and scald. The rot progresses and 

 spreads very rapidly in transit and storage, but can be 

 checked by rapid drying of affected stock. 



POTATO: SURFACE MOLD. 



Cause : Various fungi. 



Under transit or storage conditions, potatoes often show 

 a superficial development of mold growth which is abso- 

 lutely non-injurious to the tubers except as it affects their 

 appearance. Various fungi are concerned, including blue 

 mold and Rhizoctonia, and their growth is favored by the 

 presence of moisture, especially the juice from nearby 

 frozen or rotted tubers. Wet, dirty tubers and cut or bruised 

 areas are likely to become covered with surface molds. 



Surface molds are objectionable in bulk shipments be- 

 cause of the bad appearance of the stock. 



Proper ventilation to dry the surfaces of the potatoes will 

 aid in preventing this trouble. 



POTATO: HOLLOW HEART. 



Cause : Rapid growth. 



Hollow heart is a more or less irregular cavity in the 

 center of the tuber, varying in size and often lined by tissue 

 which is browned and glassy. 



Hollow heart occurs most frequently in large, coarse, 

 rapid-growing varieties, particularly when these are grown 

 in very fertile soils. It also is common in red varieties grown 

 in the sand hills region of Nebraska. 



Hollow heart and black heart may be confused since 

 cavities occasionally develop in tubers affected with black 

 heart ; but these differ from those of hollow heart by their 

 association with discolored tissue. 



Usually hollow heart cannot be detected until the affected 

 potatoes are cut. It does not affect their keeping quality. 



Affected stock is very undesirable for table use. 



Ref. (49). 



