. Diseases of small grain crops in Illinois. Grain. BOEWE: DISEASES OF SMALL GRAIN CHOI'S 61 produce still smaller spores which may be carried by the wind to nearby buckthorn bushes. If infection of the buckthorn leaf occurs, cluster cups are formed and in them are produced spores which in turn are carried by the wind back to oats or susceptible. Fig. 20.—Crown rust of oats. Rust pustules occur on the leaves and sheaths. Early in the season they are reddish brown and open, as on the four leaves in the upper part of the figure; but later other pustules appear, which are black and covered, as on
. Diseases of small grain crops in Illinois. Grain. BOEWE: DISEASES OF SMALL GRAIN CHOI'S 61 produce still smaller spores which may be carried by the wind to nearby buckthorn bushes. If infection of the buckthorn leaf occurs, cluster cups are formed and in them are produced spores which in turn are carried by the wind back to oats or susceptible. Fig. 20.—Crown rust of oats. Rust pustules occur on the leaves and sheaths. Early in the season they are reddish brown and open, as on the four leaves in the upper part of the figure; but later other pustules appear, which are black and covered, as on the leaf sheath below the four leaves. grasses. When these are infected, summer spores are formed in pustules on the leaves, and a new season's epidemic is begun. In warm regions the summer spores survive the winter and start the new season's infection, in which case the rust does not need the buckthorn as a bridging host. Importance.—Crown rust is present on the oats crop every year and, like all other epidemic diseases, varies from year to year both in prevalence and in the intensity of its attack. In years favorable to the rust, from 60 to 85 per cent of the plants in the oats fields of the state become diseased, and the presence of the rust in the leaves reduces their effective food manufacturing area by 10 to 30 per cent. In years unfavorable to the rust as little as 15 per cent of the oats plants become infected, with an accompanying reduction in leaf area of about per cent. The average annual prevalence of crown rust in Illinois, based on 12 years of data, is per cent, and the average reduction in leaf area is per Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Boewe, Gideon Herman, 1895-. Urbana
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