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(see Page 216). Wagner declares that "if the leaf is
picked before it is ripe, it needs a process of subsequent ripening to give it a good quality. This is impossible if the leaf is separated from the stalk, but it takes place to perfection under the American method" (the leaves cured while still attached to the stalk); but if the leaf process is used, the leaf would certainly not be picked before it is ripe. German authorities maintain that the weight of tobacco leaves cured on the stalk is 15 per cent greater than that of leaves cured separate from the stalk, due to the translocation of matter from stalk to leaf during ripening after the harvest. Behrens, however, has shown that the current of solids is from leaf to vein, thence to rib, and thence to stalk, and not the reverse. Frear found nothing to indicate any marked gain in weight as the result of slow ripening or curing on the stalk. Results by Carpenter, in North Carolina, on yellow leaf, point in the same direction. Nessler long ago pointed out that the leaf cured on the stalk, and separate from it, showed no appreciable difference in weight. At the Pennsylvania station, 1000 leaves cured on the stalk weighed, when stemmed, 116 ounces; 1000 leaves harvested more nearly ripe, and cured leaf by leaf, yielded 151 ounces of stemmed leaf, the precise gain varying with the ripeness of the leaves.
It will be seen, therefore, that opinions are widely divergent, among both practical tobacco growers and scientists, concerning the good and bad points of the single leaf system. Yet the fact that it is but little employed in the seedleaf sections is no argument against it. Frear found that the ripest of the stalk-cured leaves were thinner than the less mature leaves harvested separately. CHAPTER XL
PESTS OF TOBACCO—DISEASES, INSECTS, THE ELEMENTS.
Following the chapter on curing, we will first discuss the troubles or diseases that are met with in curing tobacco. Chief among these is pole burn. "This trouble," says E. S. Goff, "appears as dark spots near the midrib or vein; under favorable conditions it spreads rapidly, discoloring and rotting the whole leaf, and often destroying the entire crop in 24 to 36 hours. It is caused by two fungous enemies: First, a sort of mold, which attacks the outside of the leaf and lays the interior open to the invasion of bacteria, which (second) then develop rapidly, causing the principal mischief. The development of the disease is chiefly controlled by atmospheric conditions, being most probable in rather warm, very humid air. A nearly cured, dry leaf is not liable to attack. A temperature above 100° F., or below 40°, greatly retards its activity; but one of ?0°-90° is most favorable. If we can control moisture and temperature conditions, we can prevent injury from this otherwise menacing enemy." Examination shows that the leaves have changed from a greenish-yellow to a iark brown or almost black color, that the fine texture has disappeared, and that instead of being tough and elastic, the whole leaf is wet and soggy, and tears almost with a touch, falling of its own weight from the stalk.
Something has been done at the Wisconsin experiment station to combat this disease (as described in the preceding chapter), and considerable has been accomplished at the Connecticut station by Dr. W. C. Sturgis. It appears from his work, as well as from the experience
of practical growers, that a crop is very seldom cured at the North without showing some traces of disease. Even during the most favorable seasons, the disease makes its appearance in the center of the curing barn, where the temperature is higher, and the moisture more retained in and about the leaves, whereas, in unfavorable seasons, the loss often amounts to practically the entire crop. Nor is it confined to the seedleaf sections, being common in the heavy shipping and yellow districts. It is not the mold (Cladisporium) that does the mischief so much as the bacteria, which cause the rapid decay. Sturgis found that warmth as well as moisture is conducive to pole burn, and this fact emphasizes the necessity of securing good circulation of air in the curing barn, and especially when artificial heat is employed. All attempts to inoculate thoroughly cured tobacco with bacteria of pole burn were failures. Sturgis regards this as partial confirmation of the generally expressed view, that when tobacco has cured to a certain degree, the period varying from ten days to three weeks after hanging, there is very little danger of polo burn.
The remedy for pole burn has already been described in the chapter on curing. It is to get rid of the excess of warmth and moisture, which can only be done by a complete system of ventilation. For this purpose, Sturgis strongly endorses horizontal ventilators near the ground, a similar row for each tier of tobacco and one or more large ventilators along the ridgepole. The ventilators in the walls should open horizontally at intervals of about four feet, as shown in Fig. 59. They should be from five to ten feet long, one foot high, hung from the upper edge by strap hinges, so as to be raised and hooked up, and occupying the full length of the building. When these are all open, the air will enter freely, not only near the ground, but also just below each tier of tobacco. Free ventilation in the roof is absolutely essential to allow of the escape of warm, moist air, any of the systems outlined in the chapter on barns being available for this purpose.
"White Vein" or "Stein Rot" appears in the latter stages of curing cigar leaf, in the form of white, velvety patches of long-piled mold, first affecting stalk and rib, and later destroying the tissue near the veins and ribs and causing the peculiar white veins. This disease is also due to a fungus (Botrytis longibrachiata) that thrives upon drying vegetation. "The fungus seldom reaches maturity on the curing stalks," says Sturgis, "for it requires some days and considerable moisture for
FIG. 65. RED-LEGGED GRASSHOPPER (Pezotetthc femnr-rutmtm). Enlarged one-fourth.
its complete development, hence by the time its vegetative threads are ready to produce the fruiting branches, the stalks are too far dried to afford the requisite nutriment. After the curing process is completed, however, the tobacco is taken down, and the stalks and leaves most seriously affected with stem rot are thrown down on the floor with the refuse which always remains after the curing of a crop of tobacco. Here on the damp, earth floors and in company with decaying stalks and leaves, the stem rot fungus finds all the conditions favorable to its further development. The fungus spreads among the refuse, and produces its spores in enormous quantities. It is not unusual upon entering a barn, even during this process of curing, to find the floor partially covered with the refuse of the previous year's crop, the latter often looking as though a fall of snow had whitened it, so densely is it covered with the mold and spores of this fungus. The slightest current of air serves to separate the spores from their attachment, and carry them through the barn, some finding lodgment upon and at once infecting the curing stems and leaves, others being deposited on the beams or walls of the barn and there remaining to propagate the disease another year.
"Against such a pest, absolute cleanliness is the best and simplest precaution. After the crop is cured, all the diseased stems and leaves should be carefully collected and at once burned, before the fungus has reached maturity. All the refuse remaining on the floor of the barn should then be thoroughly gathered together and burned, and the floor should be liberally sprinkled with a mixture consisting of equal parts of dry, air-slaked lime and sulphur. If the floor is of earth, covering it to the depth of an inch with clean, dry earth would prevent the dissemination of the spores through the air. A more effectual method of reaching the spores in all parts of the barn would be fumigation by means of sulphur, kept boiling for two or three hours in any iron vessel over a small kerosene stove. In the larger barns it would be advisable to have three or four such stoves, and keep the sulphur boiling simultaneously in different parts of the barn; of course during the process of fumigation the building must be kept tightly closed, so that the fumes may thoroughly penetrate every part. If this were done once, after the removal of the cured tobacco, and again the following season, a fortnight before the tobacco is harvested, the danger from stem rot or white vein would be largely decreased, if not entirely obviated."