Vegetable and Field Crops 241 



PUMPKIN. See cucumber. 

 RADISH. See cabbage. 

 RAPE. See cabbage. 



RHUBARB 



Anthracnose '-'" {C olletotrichum erumpens Sa,cc.) . —Rotted, 

 sunken, soft spots, often several centimeters long, are pro- 

 duced on the petioles, and are thickly set in the older portions 

 with black acervuli. Though reported as yet only from 

 Illinois, the disease is probably widespread, and causes 

 considerable loss in the field, and additional loss in shipment. 



Leaf-spot '-^^ {Phyllosticta sirarninella Bres.). — Irregular, 

 brownish, diseased spots, often several centimeters in diam- 

 eter, occur on the leaf blade and bear numerous, minute, 

 black p3^cnidia. Older spots become torn and ragged. 



Crown-rot. — This soft rot of crown and petiole, probably 

 due to bacteria, has caused large loss in southern Illinois. 



ROSELLE (Hibiscus sabdariffn) 



Powdery-mildew {Microsphcera euphorbice B. & C, 

 Oidiiun). — This mildew of characteristic white, flour-like, 

 circular patches has been noted in Florida. 



Flowers of sulfur has proved effective in preventing its 

 spread. 



RUTABAGA. See cabbage. 



SALSIFY 



White-rust {Albugo tragopogonis (DC.) Gray). — White, 

 rustlike blisters (sori) upon the leaf indicate this disease. 

 In late stages of the disease the leaf, near the sori, blackens 

 and withers, often tearing lengthwise. 



Soft-rot. — A soft-rot of the loots, resulting in loss of 

 green color and prostration of the plants, is attributed to 



