148 Diseases of Truck Crops 



terized by whitish blisters or sori on the leaves. 

 When these blisters are mature, they burst open, liber- 

 ating a white dust composed of the spores of the para- 

 site. In badly infected plants diseased leaves turn 

 black and split and tear lengthwise. The rust at- 

 tacks leaves only, resulting indirectly in small and 

 dwarfed roots. To keep this trouble in check salsify 

 should be planted on new land. 



RUST 



Caused by Puccinia tragopogoni (Pers.) Cda. 



This rust resembles the white rust in appearance, 

 except that the blisters here are brown instead of 

 white. It is found wherever salsify is grown, but it 

 does not seem to have caused considerable damage. 

 The life history of the fungus is little known. 



SOUTHERN BLIGHT (FIG. 24), see PEPPER, p. 305 



DISEASES OF THE SUNFLOWER 

 (Helianihus annuus) 



The sunflower can hardly be considered a truck 

 crop. Nevertheless, this plant finds a place in truck- 

 ing, as it is often grown for its seed as a poultry 

 feed. Sunflower seedlings are subject to damping 

 off, Pythium de Baryanum Hesse. For a detailed 

 description of this trouble, see pages 42-44. 



DOWNY MILDEW (Plasmopora Halstedii Farl.) 

 of the sunflower is not different from the same dis- 

 ease on Jerusalem artichoke, p. 138. v 



