. Diseases of economic plants. Plant diseases. 68 Diseases of Economic Plants Scab ^^''^^ (Venturia pyrina Aderh., Fusicladium).—This scab much resembles that of the apple and is often accom- panied by a peculiar cracked appearance of the skin. This symptom, however, is secondary and is not necessarily present. Rough cankers are formed upon the twigs. Pear scab is generally distributed throughout the United States and Europe. The use of a dormant spray followed by two appli- cations of Bordeaux mixture, while the buds are unfolding, is recommended. Leaf-spot "^^ {Mycosphce- rella sentina
. Diseases of economic plants. Plant diseases. 68 Diseases of Economic Plants Scab ^^''^^ (Venturia pyrina Aderh., Fusicladium).—This scab much resembles that of the apple and is often accom- panied by a peculiar cracked appearance of the skin. This symptom, however, is secondary and is not necessarily present. Rough cankers are formed upon the twigs. Pear scab is generally distributed throughout the United States and Europe. The use of a dormant spray followed by two appli- cations of Bordeaux mixture, while the buds are unfolding, is recommended. Leaf-spot "^^ {Mycosphce- rella sentina (Fr.) Schr., Sep- toria). — Leaf-spot, while rarely completely destructive to foliage or crop, does inter- fere with the general pro- ductiveness and health of the tree by diminishing its green surface, often causing defoli- ation. It is known over a wide range and is common, especially in the Eastern United States and in Europe. Leaf-spot may be distin- guished from scab and blight by the fact that the diseased area is rather sharply defined and characteristically angular in outline. The center of the spot, usually ashen in color, is surrounded by a narrow brown zone, and this in turn by one of purplish hue. The ashen center bears several minute, dark-colored pycnidia. The treatment recommended for pear scab is preventive. Leaf-blight ^^ {Fabrcea maculata (Lev.) Atk., Entomos- porium).—This leaf-blight, more serious than leaf-spot, is almost as widely distributed as is the pear itself, though. Fig. 33. — Pear leaf-spot. After 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- [from old catalog]; Hall, John Galentine, 1870- [from old catalog] joint author. New York, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade1920, bookpublishernewyo, bookyear1921
