MARKET DISEASES OF VEGETABLES. 63 



RUTABAGA: GRAY MOLD ROT; BOTRYTIS ROT. 



(See Gray Mold Rot) . 



RUTABAGA: SLIMY SOFT ROT; BACTERIAL ROT. 



(See Slimy Soft Rot). 



RUTABAGA: WATERY SOFT ROT; SCLEROTINIA ROT. 



(See Watery Soft Rot). 



RUTABAGA: NEMATODE DISEASE. 



(See Nematode Disease). 



SALSIFY: WATERY SOFT ROT; SCLEROTINIA ROT. 



(See Watery Soft Rot and Beet Watery Soft Rot). 



SPINACH: SLIMY SOFT ROT; BACTERIAL ROT. 



(See Slimy Soft Rot). 



SQUASH: RHIZOPUS ROT. 



(See Rhizopus Rot). 



SWEET POTATO: BLACK ROT. 



Cause: A fungus (Sphaeronema fimbriatum). 



Black rot is characterized by greenish to nearly black, 

 circular, depressed spots, varying in size from y% to 2 inches 

 in diameter. At times the spots are very irregular, occur- 

 ing in bruises and injured places. The lesions are shallow, 

 rarely penetrating to the heart of the root, and the affected 

 tissue is quite firm and tough. Often at the center of the 

 spots small, black bodies are developed, which appear at 

 times as dense masses of small, black bristles. These are the 

 fruiting bodies or pycnidia of the fungus. Wetting the sur- 

 face of the lesion will bring out better these distinguishing 

 characteristics. 



Black rot is of common occurrence in all sweet potato 

 regions. The roots become infected in the field, often 

 through wounds. The diseased areas may enlarge in stor- 

 age or transit, where overheating and lack of ventilation 

 favor the progress of the disease. "Generally, affected stock 

 is culled out and is not sent to the markets. 



Affected stock is unfit for table use since the diseased 

 tissue is very bitter. When cooked, the entire root has a 

 bitter flavor. Diseased sweet potatoes also are unsuitable 

 for seed purposes, since black rot is spread by planting in- 

 fected seed roots. 



Ref. (24); (27); (70). 



SWEET POTATO: SOIL ROT. 



Cause: A slime mold (Cystospora batata). 

 The symptoms of this disease are small, circular, sunken 

 spots about one-half inch in diameter in which the tissue 



