STUDIES FOR DETERMINATION OF WHEAT HARVEST LOSSES DUE TO YELLOW AND BLACK STEM RUST INFECTION
FORT DETRICK FREDERICK MD
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Yellow rust and stem rust were used on varieties of variable susceptibility to determine yield depression in contrast to control plots. Moderately strong yellow rust for four weeks, end May and June, depressed grain yield by 14 in a susceptible summer variety in 1930. In 1931 three susceptible winter varieties were depressed 11 - 18 by a moderately severe yellow rust attack of four weeks, mid May - mid June. In the summer of 1933 grain weight was reduced 25 by severe yellow rust for five weeks. This was Heines Kolben summer wheat. Under the same conditions Oregon wheat variety lost only 14. Stem rust tests in 1930 reduced yield by 24 during two weeks of relatively severe infection of Rote Schlanstedter summer wheat. The damage coefficient in the per cent depression in yield which a certain intensity of rust can cause during one week aside from quantitative losses is considered. Decrease in grain quality was noted for yellow rust and stripe rust.