. Diseases of economic plants. Plant diseases. Small Fruits 123 Oregon, and California, it is regarded as the most important grape disease. Powdery-mildew attacks all parts of the plant except the roots, showing first upon both the upper and lower surface of young leaves as whitish circular spots, which ap- pear somewhat as though dusted with flour. These spots enlarge, coalesce, and may cover the whole leaf. The af- fected leaf is retarded in growth and becomes distorted. Mildewed blossoms fail to set their fruit, and fruit that. Fig. 62. — Black-rot as it shows on the leaves. After Anderson.
. Diseases of economic plants. Plant diseases. Small Fruits 123 Oregon, and California, it is regarded as the most important grape disease. Powdery-mildew attacks all parts of the plant except the roots, showing first upon both the upper and lower surface of young leaves as whitish circular spots, which ap- pear somewhat as though dusted with flour. These spots enlarge, coalesce, and may cover the whole leaf. The af- fected leaf is retarded in growth and becomes distorted. Mildewed blossoms fail to set their fruit, and fruit that. Fig. 62. — Black-rot as it shows on the leaves. After Anderson. is mildewed soon ceases growth and falls, or develops ir- regularly and fails to ripen. The mildew fungus is strictly superficial and may be rubbed off, leaving a discolored spot. In late stages perithecia may be recognized as very small black bodies, about mm. in diameter, lying within the diseased areas. The disease develops in most destructive form in shaded, damp, poorly ventilated situations. Rain and fogs favor it, while very dry weather inhibits it. The American vines are less susceptible than the European 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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Keywords: ., bookauthorstevensf, bookcentury1900, bookdecade1920, bookyear1921
