Further Experiments on the Control of Barley Smuts

In 1930 the writer (7Y presented the results of early experiments on the control of barley covered smut (Ustilago hordei (Pers.) Kell, and Sw.) with dust fungicides, together with a rather comprehensive review of the pertinent literature on the subject up to that time. The development since then of new fungicidal dusts, some of which were effective in controlling barley stripe (Helminthosporium gramineum Rabh.) (9) and black loose smut (Ustilago nigra Tapke) (S),' made it seem desirable to continue experiments on the control of covered smut with dust fungicides. The principal difficulty encountered in work with barley covered smut lies in securing seed that will produce plants with a high percentage of smutted heads, and in growing a crop, especially during arid shortly after emergence (3), under conditions highly conducive to infection, so as to furnish an adequate test for the fungicides used or for the varieties being studied. The failure to secure infection through seed inoculation has been mentioned by Aamodt and Johnson (1), Briggs (2), Tisdale (16), and others. Blackening the seed with spores of covered smut usually does not bring about heavy infection. Furthermore, control under these conditions is not always a reUable criterion of the effectiveness of a fungicide, because in nature much of the inoculum is found under the glumes