6 



CIRCULAR 7 4 7, U. S. DEPARTMENT OF AGRICULTURE 



Scald 



Scald, caused by Rhynchosporium 

 secalis (Oud.) J. J. Davis, is a fungus 

 disease common on smooth bromegrass. 

 Specialized races of the parasite attack 

 several grasses. Initial symptoms ap- 

 pear on the leaf blades as irregular 

 water-soaked areas, which within a few 

 days dry, and each lesion takes on a char- 

 acteristic scalded appearance (fig. 8). 

 Dried lesions are typically grayish green, 

 and conidia are borne on them in concen- 

 tric rings. Conidia are hyaline, short- 

 cylindric, with one septation, and have 

 a short oblique beak. Severely infected 

 leaves wither and die. Scald appears 

 late in spring and early in summer, and 

 its development is favored by periods of 

 humid, warm weather. 



Figure 



8. — Scald on smooth 

 bromegrass. 



