. Diseases of economic plants. Plant diseases. 166 Diseases of Economic Plants turnips, rutabagas, radish, black mustard, charlock, and other members of the cress family are affected. Black-rot was first noted on turnips in 1892 in Iowa, and on cabbage in 1895 in Wisconsin, and is now very dis- astrous in its effects in practically ail sections of the United States east of the Mississippi River, as well as in the more western states. Infection arises from the causal bacteria which are often present in the soil from preceding years. These bac- teria gain access to the drops of water at the wate
. Diseases of economic plants. Plant diseases. 166 Diseases of Economic Plants turnips, rutabagas, radish, black mustard, charlock, and other members of the cress family are affected. Black-rot was first noted on turnips in 1892 in Iowa, and on cabbage in 1895 in Wisconsin, and is now very dis- astrous in its effects in practically ail sections of the United States east of the Mississippi River, as well as in the more western states. Infection arises from the causal bacteria which are often present in the soil from preceding years. These bac- teria gain access to the drops of water at the water pores on the leaf edge. The first sign of the disease appears as a blackening of the veins upon the edges of the leaves. The affected region rapidly enlarges, the blackening ex- tending toward the stalk, and throughout the vascular system. Soon this blacken- ing reaches the stem of the plant and proceeds up and down the stem, thus gaining Fig. 89. — Portion of cabbage stem entrance to other leaves, showing blackened veins. Re- gj^^u reaching the entire drawn after Russell. i - tt n i plant. Usually many leaves are infected simultaneously. Affected leaves soon yellow and wilt, owing to the obstruction of the water channels, then dry, become parchment-like, and fall to the ground. General infection of the plant is followed by death. Reliable diagnostic characters are the blackened vein areas of the leaf, blackened veins as seen in cross sections of the leaf stalk or of the stem of the plant. Other rots may supervene, giving offensive odors. If plants with the smallest amount of dis- ease are placed in storage, the disease continues to develop,. 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
