282 Diseases of Economic Plants 



wheat loose-smut, and the same treatment, i. e., rogueing, 

 combined with a modified Jensen hot-water treatment, is 

 effective. See p. 272. 



Covered-smut^-^ (Ustilago hordei (Pers.) K. & S.). — 

 In the covered-smut, the smut masses replacing the grains 

 and glumes are at first covered by a membrane composed of 

 the outer surface of the glumes of the spikelet. This mem- 

 brane retains the spores for some time after harvest. The 

 spores, as seen en masse, after the rupture of this cover are 

 very dark to purplish black, with no tint of olive. 



The formalin treatment applies here. 



Ergot. See rye. 



Black-stem-rust (Puccinia graminis Pers.). — The forms oc- 

 curring on both wheat and rye develop equally well on barley, 

 and severe attacks of either form are common. See wheat. 



Dwarf -leaf-rust {Puccinia simplex (Koern.) E. & H.). — 

 Reported from Iowa in 1896, later from California, Minne- 

 sota, Virginia, Wisconsin, Wyoming, and Maryland, this rust 

 seems to be of recent introduction and generally of minor 

 importance, though serious in the extreme West. 



Blight ^^° (Pseudomonas translucens J. J. & R.). — Water- 

 soaked areas appear on the leaves extending in longitudinal 

 stripes or blotches between the veins. Later they turn brown. 

 Small, gray drops of exudate appear on either leaf surface. 

 Distortion of the head may be caused by disease of the en- 

 veloping leaf. It has been observed in nine states from 

 Ohio to Oregon, on many varieties of barley. Infection ap- 

 pears to be by means of the seed. 



Stripe-disease (Pleospora graminewn Diet., Helmintho- 

 sporium) . — This leaf blight was discovered in America 

 by Pammel in 1890. It is characterized by longitudinal, 

 yellowish-green spots in parallel rows upon the leaves. The 

 plants die prematurely, and the yield is thus reduced. It is 

 reported from many states. The loss in some fields amounts 

 to from 10 to 50 per cent of the crop. Stripe is almost en- 

 tirely prevented by formalin seed treatment (1 pt. to 30 gals., 

 2 hrs.). 



