CHARACTERISTICS OF SOME FORAGE-GRASS DISEASES 



Leaf Spot 



The leaf spot disease caused by Helmintho- 

 sporium vagans Drechsl., occurs only on 

 bluegrass. Initial infections appear as chlor- 

 otic specks on the blades. These rapidly 

 develop into ovate, straw-colored lesions with 

 reddish margins (fig. 4). A single lesion may 

 cover the entire width of a blade, and severely 

 infected leaves wither and die. Conidia of 

 the fungus are borne on the lesions or on with- 

 ered leaf tips. Conidia are characteristically 

 dark olivaceous, cylindrical, or slightly tapered, 

 with five to eight septations. The disease 

 occurs from late in spring until fall and attains 

 its greatest severity during midsummer. Leaf 

 spot development is favored by periods of 

 humid, hot weather. 



Figure 4. — Leaf spot 

 on Kentucky blue- 

 grass. 



