MARKET DISEASES OF VEGETABLES. 19 



on onion bulbs can be checked by rapid curing of the onions 

 as soon as they are dug. 

 Ref. (48).* 



RHIZOPUS ROT. 



OF BEAN, BEET, CABBAGE, CARROT, ONION, SQUASH, SWEET POTATO, 

 TOMATO, AND OTHER VEGETABLES. 



Cause: A fungus (Rhizopus). 



In its early stages, Rhizopus rot consists of soft, water- 

 soaked areas. These enlarge rapidly and often lead to a 

 leaky condition of affected stock. Under proper moisture 

 conditions, there is produced a coarse, white, stringy mycel- 

 ium bearing white, glistening heads or sporangia, which 

 later turn brown or black. This mycelium is often called 

 "whiskers" because of the long, loose growth of hyphae. 



Generally the rot is accompanied by a sour, acid odor, 

 noticeable when the diseased tissue is freshly broken. In 

 carrots, sweet potatoes, and other crops which are rich in 

 starches and sugars, acetic acid is produced, giving rise to 

 a vinegar-like odor. In cabbage lactic acid is produced and 

 an odor of sauer kraut is the result. 



This rot is distinguishable from watery soft rot by its sour 

 odor and by the presence of the fluffy, stringy mycelium 

 with its sporangia. The mycelium of Sclerotinia is white 

 and cottony or matted. In advanced stages, the Rhizopus 

 mycelium collapses, becomes matted, and appears gray or 

 brown, but lacks the black sclerotia of Sclerotinia. 



The sporangia, the color of the mycelium, and the sour 

 odor of the rot distinguish it from gray mold rot, and the 

 presence of the mycelium distinguishes it from slimy soft rot. 



Rhizopus rot is favored by high temperatures. In this 

 respect it differs from watery soft rot or gray mold rot, 

 both of which develop best at moderate temperatures. It 

 is common in overheated, humid cars, especially in the sum- 

 mer, or in refrigerated cars in which the ice was allowed 

 to run low. 



Usually the fungus gains entry through wounds. The 

 original infections may take place in the field, in transit, or 

 in storage since the spores of the fungus seem to be every- 

 where present. The rot develops and spreads very rapidly. 

 Like Sclerotinia, Rhizopus spreads from affected to healthy 

 stock by contact. 



Sorting out of bruised stock, drying of moist surfaces, 

 and proper ventilation and refrigeration will act as effec- 

 tive control measures in transit and storage. 



SLIMY SOFT ROT. 



OF BEAN, BEET, CABBAGE, CARROT, CELERY, LETTUCE, MUSTARD, ONION, 

 POTATO, RADISH, RUTABAGA, SHALLOTS, SPINACH, TURNIP, AND OTHER 

 VEGETABLES. 



Cause: Bacteria (Bacillus carotovorus group and other 

 bacteria). 



*Reference is made by number to "Literature cited," pp. 13-17. 



