CHARACTERISTICS OF SOME FORAGE-GRASS DISEASES 



Brown Spot 



Brown spot, caused by Pyrenophora (Helmin- 

 thosjwrium) bromi (Died.) Drechsl., is a fungus 

 disease that attacks smooth bromegrass. Initial 

 symptoms appear as small, dark spots on the 

 first blades formed early in spring. As lesions 

 enlarge, a yellow halo forms around each spot 

 (fig. 6). Severely infected leaves yellow and 

 wither. Conidia of the fungus develop either Oji 

 the lesions or on the withered blades. The co_ 

 nidia are light yellowish, with 1 to 10 septations. 

 Ordinarily this stage is rarely found. At this time, 

 however, small black bodies can be discerned 

 embedded in the dry, diseased leaves. These 

 bodies are the initials of the perfect or perithecial 

 stage of the fungus and carry it through the rest 

 of the growing season and through the winter. 

 They do not mature and release the perfect spore 

 stage until very early in the spring of the follow- 

 ing year. Ascospores are light brown, with com- 

 monly 3 transverse septations, which are further 

 divided by a longitudinal septation. Brown spot 

 develops during periods of wet, cool weather and 

 is most prevalent very early in spring. 



Figure 6. — Brown 

 spot on smooth 

 bromegrass. 



Leaf Spot 



Leaf spot, a fungus disease caused by 

 Selenophoma bromigena (Sacc.) Sprague and 

 A. G. Johnson, attacks smooth bromegrass. 

 Initital infections appear as small, brown 

 specks on the leaves early in spring. As 

 lesions enlarge they become irregular in shape 

 and size. Mature lesions are translucent in 

 appearance, and black fruiting bodies develop 

 at random in them (fig. 7). These are the 

 pyenidia of the fungus, and in them masses 

 of conidia are produced. The conidia are 

 small, hyaline, slightly sickle-shaped, and are 

 nonseptate. Mature pyenidia often drop out 

 of the lesions, leaving pinhole perforations. 

 The disease is favored by periods of moist, 

 cool weather and diminishes in severity as 

 the season progresses, all but disappearing 

 during the hot, dry period of midsummer. 



Figure 7. — Leaf spot on 

 smooth bromegrass. 



