152 Diseases of Truck Crops 



Slime Mold 



Caused by Fuligo violacea Pers. and Physarum 

 plumbeum Fries. 



Very often the plants in the seed beds are covered 

 with white, yellowish, or purple jellylike growths. 

 These patches may vary from three to six inches or 

 more in diameter and cover the foliage, peduncles, 

 and stems. In 12 to 24 hours this slime thickens and 

 becomes covered with a white or yellowish crust 

 which readily cracks and liberates the spores in the 

 form of a dark brown powder. The growth, which 

 is a slime mold, has been determined as Fuligo 

 violacea Pers. (fig. 25 a). The organism is not a 

 parasite on the sweet potato plant; nevertheless its 

 presence in a seed bed is not desirable. The slime 

 mold covers the plant, shutting off light which is es- 

 sential for its proper nutrition. There is another 

 slime mold, Physarum plumbeum Fries., which often 

 grows on the foliage (fig. 25 b). These molds are 

 seen only in seed beds in the open or on sweet potato 

 beds in the greenhouse. 



"Soil Rot," "Pox," or "Pit" 



Caused by Cystospora batatas E. 



The term soil rot is somewhat misleading, as the 

 disease does not produce a rot. The name "pox" 

 or "pit" is a better description of the disease. 



