12 CIRCULAR 74 7, U. S. DEPARTMENT OF AGRICULTURE 



DISEASES OF ANNUAL GRASSES 



SUDAN GRASS 



Bacterial Spot 



Bacterial spot, caused by Pseudomonas syringae 

 Van Hall (Bacterium hold Kenclr.), attacks several 

 grasses and is common on Sudan grass {Sorghum 

 vulgar e Pers., var. sudanensis Piper and Hitchc). 

 Initial infections appear as circular to elliptical 

 water-soaked spots on the lower leaves. These 

 spots soon become dry and papery and are light- 

 colored (fig. 12). The disease appears soon after 

 . seedlings emerge in spring and progresses with 

 plant development throughout the entire growing 

 period, gradually spreading from the lower leaves 

 over all the others. Disease development is favored 

 by periods of warm, moist weather. 



Figure 12. — Bacterial 

 spot on Sudan 

 grass. 



Bacterial Stripe 



Bacterial stripe, caused by Pseudomonas an- 

 dropogoni (E. F. Sm.) Stapp, attacks several 

 grasses and is common on Sudan grass. Initial 

 infections appear on the leaves as long, narrow, 

 irregular stripes (fig. 13). These soon dry, be- 

 come pigmented, and are covered with an abun- 

 dance of dry exudate. Severely infected leaves 

 dry and wither. Stripe first appears about 

 midsummer and continues until plant maturity. 

 Disease development is favored by periods of 

 warm, moist weather. 



Figure 13. — Bacterial 



stripe on Sudan 

 grass. 



