6 BULLETIN 1046, U. S. DEPARTMENT OF AGRICULTURE. 



In 1914 only two urediniospore sprays were applied, one on April 

 19 and the other on May 23. Neither of these sprays was followed 

 by any noticeable rust infection. Canvas covers were not used. In 

 1915 urediniospore sprays were given on April 20, 21, 27, and 29, 

 and on May 7, 10, 20, 22, and 31. Inoculated seedhngs were trans- 

 planted into the soil in vacant rows, which were left for that purpose, 

 this being the first attempt to use the infection-center method. 

 Canvas covers were used and a severe epidemic was caused, as shown 

 by the data on rust infection. In 1916 urediniospore sprays were 

 given on April 6, 13, 14, 20, 25, 26, and 29, and on May 1, 4, 16, 19, 

 and 27. Canvas covers were used. In addition to these sprays the 

 infection-center method was employed. A severe epidemic resulted. 

 In 1917 sprays of urediniospores were given on May 23 and 29, and 

 on June 6. A few hand inoculations in the field were made in the 

 spring, but the efforts were mostly directed toward establishing in- 



I' "J 



H 



111 



m 



A, 5 per cent. B, 10 per cent. C, 2.5 per cent. D, 40 per cent. E, 65 per cent. F, 100 per cent. 



Fig. 1. — Scale for estimating rust, illustrating six degrees of rustiness used in estimating the percentage of 

 stem-rust infection. The shaded spots represent rust, and the figures represent approximately the rust 

 percentages computed on the basis of the maximum of surfaces covered by rust as shown in the 100 

 per cent figure (F). Figure F in the diagram represents 37 per cent of actual rust-covered surface and 

 is arbitrarily selected as 100 per cent. The other percentages are in terms of figure F. 



fection centers. It was evident from the results obtained that the 

 latter method was sufficiently dependable to warrant the discontinu- 

 ance of urediniospore sprays. 



The common barberry {Berheris vulgaris L. ; see PL I, fig. 2) , planted 

 south of the rust nursery plats, furnished some secial infection in 

 1915, 1916, and 1917. Straw, bearing telia of stem rust, was placed 

 around each shrub in the fall, so as to provide the necessary telio- 

 spore material to infect the barberry leaves in the spring. 



The final field notes were taken during the latter part of June or 

 early in July, at the time the nursery was harvested. These included 

 the percentage of stem rust, estimated in accordance with the scale 

 shown in figure 1 and used by the Office of Cereal Investigations of 

 the Bureau of Plant Industry, United States Department of Agri- 

 culture. Notes on the type of head, plumpness of grain, and other 

 characters also were recorded. 



