In cooperation with the Minnesota, North Dakota, South Dakota, Wyoming, Nebraska, Kansas, Texas, Iowa, Wisconsin, and Michigan Agricultural Experiment Stations and the Dominion of Canada Dept. of Agriculture.

Black stem rust probably causes greater losses to the spring-wheat crop than all other diseases combined. Nearly all of the hard red spring-wheat varieties now grown are very susceptible to rust. Some varieties of durum wheat are much more susceptible than others. Uniform spring-wheat nurseries were sown at 39 experiment stations in the United States and Canada during one or more of the six years from 1919 to 1924, inclusive. The percentages of infection of stem rust of the 33 varieties of wheat which were grown in all or some of the uniform nurseries are reported in this circular. Percentage estimates of rust infection were recorded in 107 of the 113 station years during which the nurseries were grown. Heavy rust infection occurred at most stations each year. The durum wheats were much more resistant as a class than the hard red spring wheats. Pentad, Monad, Acme, and Nodak are the most resistant. Kota and a few nevr hybrid wheats are much more resistant to rust than Marquis. Marquis escapes rust slightly better than Power, Preston, and Haynes Bluestem. Except for the resistant varieties, the average rust infection on the common wheats increased with the lateness of the average date of maturity of the varieties. Early varieties evade rust better than Marquis. The two varieties of spring emmer were nearly immune to rust. The reduction of losses from stem rust of v\'heat by growing resist- ant varieties is a certain and feasible method. The varieties to grow depend upon local adaptation and market value as well as rust resistance.

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