532 THE SMALL GRAINS 



when the greatest infection takes place. The developing 

 kernels are immediately injured from direct infection, 

 and not from infection in the seedling reaching the spike 

 through permeation of the stem, as in loose smut of wheat. 

 It is found, however, that an abundance of conidia is 

 produced on the dying roots of infected seedlings, and this 

 is a source from which, no doubt, later spores are carried 

 by the wind or insects and reach the spikes at flowering 

 time. Johnson conducted inoculation experiments with 

 this fungus on oats in sterilized soil, and was able to 

 entirely destroy oat seedlings from artificially infected 

 seed (Fig. 166). 



Seed treatment for smut by the formalin method will 

 also kill many adhering spores of scab. Thorough screen- 

 ing and cleaning with the fanning mill will not only elim- 

 inate small kernels, but will blow out the scab-infected 

 kernels, which are always lighter. 



574. Stripe disease of barley (Helminthosporium gra- 

 mineum, Rabh.). This disease was so called by Rostrup 

 because of the long, discolored stripes produced on the 

 leaves, leaf-sheaths, and culms. Prillieux has given the 

 name helminthosporiosis to this and the other diseases 

 caused by Helminthosporium. Inoculation experiments 

 thus far have shown that H. gramineum affects barley 

 only and will not transfer to other cereals. The disease 

 caused by H. gramineum was studied by Pammel (1909), 

 who called it the " yellow leaf disease " of barley and 

 showed that the infection is transmitted through the 

 germinating seed. Later Bakke (1912) reported the 

 same manner of transmission of infection as a result of 

 his investigations of another species (H. teres) which he 

 calls " late blight " of barley. Johnson (1913) has studied 

 H. gramineum, H. teres, and H. sativum, and found that 



