. Diseases of economic plants. Plant diseases. VEGETABLE AND FIELD CBOPS 195 neath. This, the summer stage, is chiefly responsible for the hibernation of rust in the east. Later in the season the sori become black instead of rusty col- ored, thus constituting the winter stage of the rust. In the spring still an- other stage, the spring stage, may occasionally be seen, though it is rare east of the Rocky Mountains. This con- sists of small, oval, pale spots upon the branches or leaves. In the cen- ters of these spots small round pustules develop in concentric lines. Soon each pustule opens, con
. Diseases of economic plants. Plant diseases. VEGETABLE AND FIELD CBOPS 195 neath. This, the summer stage, is chiefly responsible for the hibernation of rust in the east. Later in the season the sori become black instead of rusty col- ored, thus constituting the winter stage of the rust. In the spring still an- other stage, the spring stage, may occasionally be seen, though it is rare east of the Rocky Mountains. This con- sists of small, oval, pale spots upon the branches or leaves. In the cen- ters of these spots small round pustules develop in concentric lines. Soon each pustule opens, constituting a very minute cup which is sunken into the leaf. From these cups issues a powder quite similar to that from the sori of the summer stage, though more orange in color. All three stages of rust — spring, summer, and winter — may occur simultaneously upon the same plant. The disease spreads rapidly throughout the field during the spring and summer stages. The winter stage is the. Fig. 86. — Sori of the asparagus rust upon the stems, enlarged. 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 Stevens, Frank Lincoln, 1871-1934; Hall, John Galentine, 1870-. New York, Macmillan
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