CHARACTERISTICS OF SOME FORAGE-GRASS DISEASES 



Rusts 



Leaf rust, a fungus disease caused by Puccinia 

 poae-sudeticae (West.) Jorstad, attacks blue- 

 grass. Initial symptoms first appear on the leaf 

 blades as small chlorotic spots. These soon 

 develop into typical rust pustules (fig. 2). 

 Orange-colored spores are produced in large 

 numbers in each pustule and are liberated when 

 the pustules rupture. Leaf rust is prevalent each 

 year but, like mildew, it is seasonal in its de- 

 velopment. It first appears late in spring, 

 diminishes somewhat during the dry, hot period 

 of summer, and becomes very abundant early 

 in fall. Leaf -rust development is favored by 

 periods of warm, humid weather. 



Stem rust, caused by Puccinia graminis 

 Pers., the destructive rust common on cereal 

 crops, attacks several grasses, including blue- 

 grass. On bluegrass it can be distinguished 

 from leaf rust only by microscopic examination 

 of the pustule and spores. Stem rust is not so 

 prevalent on bluegrass as leaf rust; it occurs in 

 abundance only late in summer and in fall. 

 Physiologic races of stem rust occur commonly 

 in nature. 



-,. 





Figure 2. — Leaf rust 

 on Kentucky blue- 

 grass. 



