40 TECHNICAL BULLETIN 17 



were recorded : the number of culms which developed heads ; the num- 

 ber of tillers which did not mature; the degree of infection (designated 

 as heavy, moderate, or light) on the roots, the foot, and the nodes. 

 After harvesting, the weight of the straw and of the threshed grain 

 was recorded, and from this the yield per acre was calculated. The 

 infection of. Lion barley was slightly more pronounced than on the other 

 hosts. These data for Lion barley are summarized in Table XII. 



In order to arrive at a simple factor which would express the total 

 infection for the roots, the foot, and the nodes for a single plot and 

 would also take into account the severity of infection as well as the 

 percentage of plants infected, the number of heavy infections was 

 multiplied by 10, the number of moderate infections by 5, and the num- 

 ber of light infections by I, and the three products were summed. This 

 was taken as an arbitrary index of the infection. In order to make 

 comparison more simple, these summations were reduced to unity by 

 dividing each by the lowest sum. This is the factor designated as total 

 infection in Table XII. In order to compare the combined effect of 

 root- and foot-rot, the summation for each was added and these sums 

 in turn were reduced to unity. 



In order to bring out the relation of infection to fertilizers and 

 yields, the arbitrary indices of infection were grouped into three 

 classes and the yields per acre into three classes, and the fertilizer plots 

 were arranged according to their infection and yield in the various 

 classes as shown in Table XIII. From this summary table it is quite 

 clear that the amount of foot- and root-rot is not correlated with any 

 particular fertilizer. 



The disease did not appear in its severest form on any of the plots. 

 Under the conditions of this experiment, there was no evidence of 

 severe stunting of the plants or of excessive tillering. 



COMPARISON OF SEVERAL ROOT-ROT CAUSING 

 ORGANISMS 



In order to obtain comparative results on the pathogenic effect of 

 different soil organisms on Marquis wheat and Lion barley, a culture 

 of Helminthosporium isolated from the foot-rot of wheat in Illinois by 

 F. L. Stevens and a culture of Fusarmm culmorum (W. Sm.) 

 Saccardo isolated from scabby wheat, were compared with the Helmin- 

 thosporium sativum isolated from barley foot-rot in Minnesota. 



