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Worms having cocoons attached to them, resembling grains of rice, should not be killed, as these cocoons belong to a family of parasites called Microgaster congregate, which destroy the horn worms in great numbers.
Catching the moths in traps, or poisoning the blossoms of petunia and Jamestown weeds with the sweetened solution of cobalt (water one pint, molasses or honey one-fourth pint, cobalt one ounce), diminishes the number of worms, but there will always be left enough to be troublesome. A drove of turkeys kept in the tobacco field will destroy a great number of the worms, but the only safety is in going over the field at least once a week, or oftener, picking off the worms and destroying them. The worms usually stay on the underside of the leaf; if a hole is seen in the leaf, no matter how small, a worm will usually be the cause of it. The work cannot be done too carefully, for if one or two worms remain on a plant, they will completely riddle it in a very short time. If they are well cleaned out when they first appear, much time and labor would be saved.
Spraying tobacco with Paris green to destroy the tobacco horn worm has engaged the special attention of the Kentucky experiment station. The proportion used was one pound green to 160 gallons of water. Plants were thoroughly sprayed July 27 and August 3. There were fewer worms on sprayed than on unsprayed plants. As to the amount of arsenic, only one-third of one grain of arsenious oxide per pound of tobacco was the largest quantity recovered by careful chemical examination. Only four per cent of the arsenic originally applied was recovered. As two to three grains of arsenic are required for a fatal dose for an adult man, the station officials see no harm in making these sprayings during a dry season.
There are usually what farmers call two "showers" of these worms, one coming about the last of June and the other about the middle of August, or, rather, during the light of the moon in August, at which time the moth is most industrious in depositing its eggs on the plants. The first influx is easily destroyed, for the tobacco is then small and there are but few hiding places for the worms, until the suckers begin to put out. It is the second influx that is to be dreaded. The large size of the tobacco leaves at this time, the presence of the suckers and the disposition of the worms, as they grow older, to shift their places, all makes it very difficult to-rid the tobacco of this devouring and destructive enemy late in the season.
3. OTHER TROUBLES WITH THE CROP.
Broom Rape.—In central Kentucky, there is a parasitic flowering plant called broom rape, that attaches itself to the roots of hemp and tobacco and derives its nutriment from that source. It is known to botanists as Phelipwa ramosa, and grows to the hight of about ten inches. As described by the botanist of the Kentucky experiment station, "The stems are thick, whitish, fleshy, pubescent, generally branched and bear small scale like bracts, in place of leaves, which, when old, turn brown at the tips. The flowers are white with a faint purplish tinge; sometimes of a decidedly purple color. They are borne in loose spikes in the axiles of the bracts. The flowers are all perfect, and as many as forty are produced on a single branch." A section through a young plant and the root to which it is attached, shows that thef are very closely united. The young broom rape pushes an elongated cell into the root of the host plant, and soon spreads out into a fibrous bundle, robbing the host plant of the nutritive elements which it derives from the soil and atmosphere. The result is an enfeeblement of the infested plants, shown in retarded growth, weakness of the stems, and reduced yield and quality of leaf.
When the land is badly infested with broom rape, the director of the Kentucky station thinks that a rotation with crops which are not attacked by it is the best means of avoiding injury. The seeds of the broom rape are very small, far smaller, indeed, than tobacco seeds, and they seem to possess great vitality, remaining several years in the ground without losing their power of germination, which appears only to take place when brought near the host plant. This parasite cannot be removed by hand, for its roots are so intimately intertwined with the roots of the host plant, that one may not be pulled up without pulling up the other. It is said that an application of gas lime to the soil will sometimes prove successful in destroying the seed of the noxious plants. The lime looses this property after being exposed to the air for some time. The application should be made to the land in the fall of the year, at the rate of two tons per acre, and plowed, or harrowed, into the ground. A stimulating manure applied to the land will aid the hemp or tobacco plant in resisting the onslaught of the broom rape. The station does not recommend stable manure, however, for this purpose. Whatever renders the soil friable, stimulates the broom rape to greater activity, when its host plant is present. It does not push its way readily through a closely compacted soil. The danger to tobacco on infested land is greatly increased when the soil is loose and porous. Rolling the land with a heavy roller is recommended when the land is infested with* the broom rape. This should be done immediately before setting out the tobacco plants.
Hail is a much dreaded enemy from which there is no escape, as it is not practicable to cover a field so that a hail storm would not cut the leaves. The best plan is for growers to mutually insure against damage by hail or wind, through a cooperative insurance company
organized for this special purpose. Such insurance is usually cheap, and is limited to the actual loss incurred. After a hail or wind storm, it is well to go through the field and prop up all plants that have been beaten down, removing the leaves that are most badly cut and stained with earth. Make the most of a bad situation and save all that can be saved.
Wind whipped tobacco is much injured. It can only be insured against as just stated. But where severe wind storms are common, a hedge, or some tall and close crop, to break the wind's force, is advisable next to the tobacco field.
Early Frost.—Since the perfect quality of the tobacco depends upon curing it at proper maturity, and since such maturity may not be reached until danger of frost, it is highly important to guard against this contingency. Even the slightest frost will destroy the intrinsic quality and market value of an otherwise perfect crop. The more valuable the crop and the greater the risk of frost, the more effort and expense may be safely put into means of protecting against frosts. A famous California orange grove is equipped with a system of iron pipes, through which water is conducted to nozzles at frequent intervals, the idea being that the spray will ward off light frosts. Barrels of tar and rubbish, in different parts of the orchard, are available for making a smudge of smoke, which is the most practicalble means yet devised. In the case of a freeze, neither of these methods is of much avail. Smoke is good against all light frosts, and is easily obtained. Strawy manure, leaves, rubbish, etc., should be piled in the lowest places and about the sides, and covered with hay caps, or ducking (previously painted with two coats of linseed oil, and dried), so as to be always dry. Have a barrel of kerosene oil handy, some cans, and torches. When frost threatens, set a night watch to inspect