. Diseases of economic plants. Plant diseases. Vegetable and Field Crops 221 furrovvetl or cracked. Mites often follow scab, making the pits much deeper. The scab at first appears as a minute reddish or brownish surface spot, often when the potato is very young. It ex- tends outward, deepens in color, and is attended with the development of an irregular, corky incrustation. The disease is often prevalent to such an extent as to pro- hibit successful potato culture. The chief loss comes from de- preciation in sale value, though there is also loss in Fig. 121.—^ Potato common-scab. After


. Diseases of economic plants. Plant diseases. Vegetable and Field Crops 221 furrovvetl or cracked. Mites often follow scab, making the pits much deeper. The scab at first appears as a minute reddish or brownish surface spot, often when the potato is very young. It ex- tends outward, deepens in color, and is attended with the development of an irregular, corky incrustation. The disease is often prevalent to such an extent as to pro- hibit successful potato culture. The chief loss comes from de- preciation in sale value, though there is also loss in Fig. 121.—^ Potato common-scab. After Melhus. Estimates show that from 5 to 75 per cent of the potato crop is unsalable on account of scab. The loss in California in one county alone is placed at $300,000 yearly. Common-scab is most prevalent in alkaline soils and is favored by moisture. Wood ashes, potash, soda, stable manure, lime, etc., increasing alkalinity, favor the growth of the fungus, and cause increase in the amount of scab in soil already infested. Materials which tend to decrease scab are commercial fertilizers, potash salts (except carbonate), land plaster, and ammonium sulfate. Rotation of crops tends. 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