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White veins, as a disease, is confined to the seedleaf and Havana-seed varieties, and is much dreaded, because it greatly impairs the value of the tobacco in which it occurs. White veins in the districts growing yellow tobacco are desired, because they add to the beauty and value of the yellow product.
Leprosy is the common name applied to a greenish fungous growth that attacks curing tobacco in the lower
Via. 66. TOBACCO MINER.
a, Adult moth; 6, worm; and r, part of leaf damaged by tins worm.
Ohio districts of Kentucky. The fungi increase with amazing rapidity, and they extend even to sound, dry tobacco in proximity, seriously damaging it. This is a disease that is doubtless propagated from spores, whicn find congenial lodgment in badly kept barns or tobacco sheds, or packing houses. All old trash left in such places should be either hauled out and spread upon the fields, or burned, while the disinfecting of barns as just described for stem rot or white vein, is also advised.
DISEASES OF THE GROWING PLANTS.
There is probably no crop produced of the same magnitude that suffers so little from disease as does tobacco, and nearly all these diseases may be avoided by proper care in the selection of the soils, in the judicious application of manure, and in the cultivation of the crop. The greatest number of diseases to which the tobacco is liable, come from a want of drainage in the soil. The diseases rarely affect more than a fraction of one per cent of the plants in a field. . These diseases are largely of a fungous nature, and are now being tardily studied by scientific experts. Their efforts will ultimately give us a scientific explanation of the form or cause of the various diseases, but this book being mainly of a practical nature, for popular use, we content ourselves with a popular rather than a mycological and physiological treatment of the subject.
Bust or Fire Blight.—The most common disease of tobacco is known as "Brown rust" or "Red field fire." This arises from three causes, viz: First, overripeness in the plant; second, a deprivation of moisture while the plant is in vigorous growth, making the leaf perish in spots for want of sustenance, and, third, the use of too much heating manure applied in the hills, with supervening dry weather.
Another field fire called "Black fire," which is totally different from the red field fire, is caused by excessive humidity, and occurs only after continued rains of several days' duration, with hot weather. This black fire is much more to be dreaded than the brown rust or red field fire, for it attacks the plant while immature, involving all the leaves, and necessitates the
catting of it before it is ripe. Sometimes this disease will spread over a field in two or three days and ruin the crop, making black, deadened spots as large as a silver dollar, but this rarely happens. Good drainage and a sufficient depth of soil to'carry off all superfluous rain water, are the only safeguards against the blighting effects of this disease.
Spotted Leaf.—There is another disease, similar to the last, called "Frog eye" or "White speck," often occurring in tobacco thoroughly ripe. It is sometimes caused by too much potash in the soil, and sometimes from the taproot of the plant coming in contact with an impervious water plane. This disease is most frequently seen in the tobacco grown in Florida. It was once regarded as a sure indication of the fineness of texture in the leaf. Forty years ago the Florida wrappers affected with this blemish commanded the highest price with the manufacturers of domestic cigars. A similar trouble at the North causes what are called "calico plants," in cigar tobacco.
Frenching (from the French word /riser, to curl) attacks tobacco grown upon old, clayey lands inclined to be wet, that have been much compacted by the tramping of stock, or through other means. Rainy weather is also a predisposing cause to this disease, and it sometimes manifests itself over a considerable area, but if the tobacco is closely plowed and a vigorous pull is given to the plants so as to break the taproots, a large majority of them will recover, if treated before the disease has gone too far. The first appearance of the disease is seen in the buds of the plants, which turn to a honey-yellow color. As the leaves expand, they become thick and fleshy, growing in long, irregular, narrow strips with ragged outlines, the leaves often cupping downward. When cut and cured, such leaves are lifeless, with a dingy, dead color, and are very light in weight. "Frenched" tobacco is worthless for any purpose except as a substitute.
Walloon or Walerloon, is a disease that affects the appearance of tho plant and causes the leaves, instead of curving in graceful outlines, to stick up like "foxes' ears," by which name the disease is known in some localities. This disease, though akin to Frenching, does not injure the tobacco to the same extent, though it reduces the weight of the cured product and impairs its quality and color. It results probably from deficient drainage.
Hollow Stalk.—The overflowing of any part of a tobacco field, though the water may stand on it for only a few hours, will produce "Hollow stalk" and "Sore shin." Some careful observers think hollow stalk results from the attack of the wireworm or the cutworm; others think it arises from the bruising of the young plant or of injury done to the epidermis, so that the sap is not able to ascend in full force. It most probably arises from the absorption by the pith of an undue amount of water, while partially overflowed, and the effects of the subsequent exposure to the hot sun. The disease is rarely seen upon a well-drained or porous soil. The plants attacked with it should be cut at once, for they will never grow or improve in any respect thereafter.
A New Disease of tobacco is described by J. Van Breda de Haan (in Med.'* Lands Plantentuin, No. 15, pp. 107, pl. 1.). It has appeared in Java. The leaves become dark spotted and greatly depreciate in value. The cause is attributed to the fungus, Phytophora nicotiana n. sp. A study of the biology of the parasite has been made and various attempts undertaken for the repression of the disease. The author thinks it can be prevented from spreading, by careful attention to, and frequent change of, the plant beds, and by spraying the