The plant louse gives off a sweetish fluid of which some ants are very fond. You may often see the ants stroking these lice to induce them to give off a freer flow of the "honey dew." This is really a method of milking. However friendly and useful these "cows" may be to the ant, they are enemies to man in destroying so many of his plants.
_Treatment._ These are sucking insects. Poisons therefore do not avail.
They may be killed by spraying with kerosene emulsion or a strong soap solution or with tobacco water. Lice on cabbages are easily killed by a mixture of one pound of lye soap in four gallons of warm water.
[Ill.u.s.tration: FIG. 166. A CHEAP SPRAYING OUTFIT]
=The Squash Bug.= The squash bug does its greatest damage to young plants. To such its attack is often fatal. On larger plants single leaves may die. This insect is a serious enemy to a crop and is particularly difficult to get rid of, since it belongs to the cla.s.s of sucking insects, not to the biting insects. For this reason poisons are useless.
[Ill.u.s.tration: FIG. 167. A SQUASH BUG]
_Treatment._ About the only practicable remedy is to pick these insects by hand. We can, however, protect our young plants by small nettings and thus tide them over the most dangerous period of their lives. These bugs greatly prefer the squash as food. You can therefore diminish their attack on your melons, cuc.u.mbers, etc. by planting among the melons an occasional squash plant as a "trap plant." Hand picking will be easier on a few trap plants than over the whole field. A small board or large leaf laid beside the young plant often furnishes night shelter for the bugs. The bugs collected under the board may easily be killed every morning.
=The Flea-Beetle.= The flea-beetle inflicts much damage on the potato, tomato, eggplant, and other garden plants. The accompanying figure shows the common striped flea-beetle which lives on the tomato. The larva of this beetle lives inside of the leaves, mining its way through the leaf in a real tunnel. Any substance disagreeable to the beetle, such as plaster, soot, ashes, or tobacco, will repel its attacks on the garden crops.
[Ill.u.s.tration: FIG. 168. FLEA-BEETLE AND LARVA _a_, larva; _b_, adult. Lines on sides show real length of insects]
=The Weevil.= The weevil is commonly found among seeds. Its attacks are serious, but the insect may easily be destroyed.
_Treatment._ Put the infected seeds in an air-tight box or bin, placing on the top of the pile a dish containing carbon disulphide, a tablespoonful to a bushel of seeds. The fumes of this substance are heavy and will pa.s.s through the ma.s.s of seeds below and kill all the weevils and other animals there. The bin should be closely covered with canvas or heavy cloth to prevent the fumes from being carried away by the air. Let the seeds remain thus from two to five days. Repeat the treatment if any weevils are found alive. Fumigate when the temperature is 70 Fahrenheit or above. In cold weather or in a loose bin the treatment is not successful. _Caution:_ Do not approach the bin with a light, since the fumes of the chemical used are highly inflammable.
=The Hessian Fly.= The Hessian fly does more damage to the wheat crop than all other insects combined, and probably ranks next to the chinch bug as the second worst insect enemy of the farmer. It was probably introduced into this country by the Hessian troops in the War of the Revolution.
[Ill.u.s.tration: FIG. 169. THE HESSIAN FLY]
In autumn the insect lays its eggs in the leaves of the wheat. These hatch into the larvae, which move down into the crown of the plant, where they pa.s.s the winter. There they cause on the plant a slight gall formation, which injures or kills the plant. In the spring adult flies emerge and lay eggs. The larvae that hatch feed in the lower joints of the growing wheat and prevent its proper growth. These larvae pupate and remain as pupae in the wheat stubble during the summer. The fall brood of flies appears shortly before the first heavy frost.
_Treatment._ Burn all stubble and trash during July and August. If the fly is very bad, it is well to leave the stubble unusually high to insure a rapid spread of the fire. Burn refuse from the threshing-machine, since this often harbors many larvae or pupae. Follow the burning by deep plowing, because the burning cannot reach the insects that are in the base of the plants. Delay the fall planting until time for heavy frosts.
=The Potato Beetle; Tobacco Worm.= The potato beetle, tobacco worm, etc., are too well known to need description. Suffice it to say that no good farmer will neglect to protect his crop from any pest that threatens it.
The increase, owing to various causes, of insects, of fungi, of bacterial diseases, makes a study of these pests, of their origin, and of their prevention a necessary part of a successful farmer"s training.
Tillage alone will no longer render orchard, vineyard, and garden fruitful. Protection from every form of plant enemies must be added to tillage.
[Ill.u.s.tration: FIG. 170. SPRAYING THE ORCHARD One way of increasing the yield of fruit]
In dealing with plants, as with human beings, the great object should be not the cure but the prevention of disease. If disease can be prevented, it is far too costly to wait for it to develop and then to attempt its cure. Men of science are studying the new forms of diseases and new insects as fast as they appear. These men are finding ways of fighting old and new enemies. Young people who expect to farm should early learn to follow their advice.
=EXERCISE=
How does the squash bug resemble the plant louse? Is this a true bug? Gather some eggs and watch the development of the insects in a breeding-cage. Estimate the damage done to some crops by the flea-beetle. What is the best method of prevention?
[Ill.u.s.tration: FIG. 171. AN APPLE TREE SHOWING PROPER CARE]
Do you know the large moth that is the mother of the tobacco worm?
You may often see her visiting the blossoms of the Jimson weed.
Some tobacco-growers cultivate a few of these weeds in a tobacco field. In the blossom they place a little cobalt or "fly-stone" and sirup. When the tobacco-worm moth visits this flower and sips the poisoned nectar, she will of course lay no more troublesome eggs.
SECTION x.x.xIV. THE COTTON-BOLL WEEVIL
So far as known, the cotton-boll weevil, an insect which is a native of the tropics, crossed the Rio Grande River into Texas in 1891 and 1892.
It settled in the cotton fields around Brownsville. Since then it has widened its destructive area until now it has invaded the whole territory shown by the map on page 177.
[Ill.u.s.tration: FIG. 172. ADULT COTTON-BOLL WEEVIL Enlarged]
This weevil is a small gray or reddish-brown snout-beetle hardly over a quarter of an inch in length. In proportion to its length it has a long beak. It belongs to a family of beetles which breed in pods, in seeds, and in stalks of plants. It is a greedy eater, but feeds only on the cotton plant.
The grown weevils try to outlive the cold of winter by hiding snugly away under gra.s.s clumps, cotton-stalks, rubbish, or under the bark of trees. Sometimes they go down into holes in the ground. A comfortable shelter is often found in the forests near the cotton fields, especially in the moss on the trees. The weevils can stand a good deal of cold, but fortunately many are killed by winter weather. Moreover birds destroy many; hence by spring the last year"s crop is very greatly diminished.
In the spring, generally about the time cotton begins to form "squares,"
the weevils shake off their long winter sleep and enter the cotton fields with appet.i.tes as sharp as razors. Then shortly the females begin to lay eggs. At first these eggs are laid only in the squares, and generally only one to the square. The young grub hatches from these eggs in two or three days. The newly hatched grub eats the inside of the square, and the square soon falls to the ground. Entire fields may at times be seen without a single square on the plants. Of course no fruit can be formed without squares.
[Ill.u.s.tration: FIG. 173. EGGS AMONG THE ANTHERS OF A SQUARE AT THE POINT INDICATED BY THE ARROW]
[Ill.u.s.tration: FIG. 174. CROSS SECTION SHOWING ANTHERS OF A SQUARE WITH EGG OF WEEVIL, AND SHOWING THE HOLE WHERE THE EGG WAS DEPOSITED Greatly enlarged]
In from one to two weeks the grub or larva becomes fully grown and, without changing its home, is transformed into the pupa state. Then in about a week more the pupae come out as adult weevils and attack the bolls. They puncture them with their snouts and lay their eggs in the bolls. The young grubs, this time hatching out in the boll, remain there until grown, when they emerge through holes that they make. These holes allow dampness to enter and destroy the bolls. This life-round continues until cold weather drives the insects to their winter quarters. By that time they have increased so rapidly that there is often one for every boll in the field.
[Ill.u.s.tration: FIG. 175. THE LARVA OF THE COTTON-BOLL WEEVIL INJURING A SQUARE]
This weevil is proving very hard to destroy. At present there seem but few ways to fight it. One is to grow cotton that will mature too early for the weevils to do it much harm. A second is to kill as many weevils as possible by burning the homes that shelter them in winter.
[Ill.u.s.tration: FIG. 176. PUPA OF COTTON-BOLL WEEVIL FROM ABOVE AND BELOW Greatly enlarged]
[Ill.u.s.tration: FIG. 177. THE PUPA OF THE COTTON-BOLL WEEVIL IN A SQUARE]
The places best adapted for a winter home for the weevil are trash piles, rubbish, driftwood, rotten wood, weeds, moss on trees, etc. A further help, therefore, in destroying the weevil is to cut down and burn all cotton-stalks as soon as the cotton is harvested.
[Ill.u.s.tration: FIG. 178. A COTTON BOLL WITH FEEDING-HOLES OF WEEVIL, AND BEARING THREE SPECIMENS OF THE INSECT]
[Ill.u.s.tration: FIG. 179. THE MEXICAN COTTON-BOLL WEEVIL, SHOWING STRUCTURE]
This destroys countless numbers of larvae and pupae in the bolls and greatly reduces the number of weevils. In addition, all cornstalks, all trash, all large clumps of gra.s.s in neighboring fields, should be burned, so as to destroy these winter homes of the weevil. Also avoid planting cotton near trees. The bark, moss, and fallen leaves of the tree furnish a winter shelter for the weevils.
[Ill.u.s.tration: FIG. 180. A SERIES OF FULL GROWN WEEVILS, SHOWING VARIATIONS IN SIZE]
A third help in destroying the weevil is to rotate crops. If cotton does not follow cotton, the weevil has nothing on which to feed the second year.
[Ill.u.s.tration: FIG. 181. MAP SHOWING DISTRIBUTION OF THE COTTON-BOLL WEEVIL IN 1913]
In adopting the first method mentioned the cotton growers have found that by the careful selection of seed, by early planting, by a free use of fertilizers containing phosphoric acid, and by frequent plowing, they can mature a crop about thirty days earlier than they usually do. In this way a good crop can be harvested before the weevils are ready to be most destructive.
CHAPTER VIII