262 Diseases of Truck Crops 



Rust 

 Caused by Uromyces appendiculatus (P.) L. 



Rust is seldom serious enough to warrant treat- 

 ment. The disease attacks all parts of the bean 

 plant except the roots. On the foliage, it appears as 

 little brown pimples or sori (fig. 47 a) the size of a 

 pin's head. These pimples soon appear on the pods 

 (fig. 47 b) , petioles, and stems, being more numerous 

 however on the leaves and pods. The pimples as 

 they get older turn from brown to black in color. 

 The powder discharged from the sori is made up of 

 countless numbers of the fungus spores. Rust does 

 not live over on the seed, but rather on the dead re- 

 fuse of the bean plants. Bean rust has the aecidio- 

 spores, uredospores (fig. 47 d), and teleutospores (fig. 

 47 c) on the same host. 



Clean culture, burning of trash and dead plants, 

 and selection of resistant strains or varieties is re- 

 commended. 



Powdery Mildew 



Caused by Erysiphe polygomi D. C. 



Powdery mildew is serious on fall beans in many of 

 the Southern States, and on beans grown for the early 

 market. It is characterized by white, mealy patches 

 on the surface of the leaves and stems. The foliage 

 soon turns yellow and dry. Powdery mildew may be 

 controlled by dusting the plants with flowers of sul- 



