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Insects of The Field And Garden

( Originally Published 1915 )

The Corn Root Worm.—Professor Holden estimates that the ravages of the corn root worm cause an annual loss of 200,000,000 bushels of corn in the Corn Belt States alone. He says, " Next to poor seed corn, the corn root worm is the greatest source of loss to the corn crop." This so-called worm is a small white larva about half an inch in length and a little larger than a pin. The eggs laid by a beetle are somewhat larger than a double pin-head. They are laid at the roots or foot of a growing corn stalk during August and September. The eggs hatch during June and July. In case the field is not planted a second time to corn, the larvae starve, but if they can get at corn they eat their way into the roots and thus cut off the root, the plant's sup-port and its source of food supply. Trained observers easily detect the presence of the worm by the peculiar bend in the corn stalks. The lack of support causes the corn to lean decidedly at the ground but heliotropism causes the tops to seek the sun and hence the double curve. The remedy for the control of the corn root worm, as suggested earlier in this chapter, is a wide rotation of crops, clean culture, fall plowing, the presence of birds and the planting of strong, vigorous seed that will enable the plants to withstand some damage and yet produce a crop.

Next to the corn root worm, the corn root louse or aphis causes the greatest loss. The aphides are generally associated with ants which use the aphides for their cows. The ants carry the aphides to pasture at the foot of some growing corn. The aphides live on the sap of the roots and the ants make regular trips to their cows in order to suck the secretion which the aphides exude on being disturbed by the ants. As the aphides cannot live on other crops, especially the clovers, the first remedy to be suggested is rotation of crops. The second remedy is clean culture. It has been found by experiment that the number of root lice can be reduced between 80 and 95 per cent by disking the ground each week before planting, as. recommended in the chapter on soil, for the conservation of spring moisture. That is, where ground was disked as soon as the surface dried in the spring and then was disked once each week until planting time, the root lice were found to be only 5 to 15 per cent as numerous as on adjacent soil left undisked. The use of the weeder or harrow after planting helps to confuse the ants as to where their cows are and helps to expose the aphides to the destruction of birds.

Other. Aphidae.—Besides the corn root louse, there are many other species of the Aphidce. They frequently make frightful devastations on all kinds of grain and vegetables, even the trees are at times stripped of their leaves, and foliage is taken from the rose bushes by these little green plant lice. These aphid have some peculiar habits and characteristics. The young that do the injury to the crops are born in insect form directly from the body of the mother. But these young have no wings and hence would spread very little were it not for the fact that the sexual forms pair and then the female, which may or may not have wings, lays two or three eggs from which winged insects hatch. In the egg form the species live through the winters of the northern States.

Right at this point may be given a series of lessons on the wonderful adjustment or equilibrium of nature. The successful agriculturist must be a better geographer than our schools have turned out in the past. The multiplication of these insects and the weather are closely related. These insects live in a temperature as cold as 8 ° F. above zero. Now these insects are held in check by a small fly-like insect that deposits its egg through the skin and into the vitals of the plant lice. But the plant lice's enemies do not live with a temperature down to the freezing point. The lice live during the late fall and warm winter days, and go on giving birth to young. But their enemies stop activities early in the fall and do not begin until late in the spring. Fortunately the enemy lays many more eggs. But this climatic control explains why after a warm winter and a late cold spring the plant lice can destroy the wheat crop over whole states before they are destroyed by their enemies. To many people the plant lice seem to come and go mysteriously, but the good geographer sees order in it all and that is the first step toward learning how to control these enemies.

The aphidae may be held in check on fruit trees by increasing the number of lady beetles, small birds, and by spraying with a soap-tobacco solution, the formula and directions for which are given in the spray calendar sent by your Experiment Station. But there is a little white, or woolly louse which one should be very, very careful not to introduce with nursery stock. It is most harmful to the apple trees. If it is once introduced there is nothing better to do than to cut down and burn every affected tree, twig, leaves and all. As the man said of his mother-in-law, " cremate, embalm, and bury; take no chances whatever."

The late Professor Slingerland, in his excellent treatment in Bailey's " Cyclopedia of Agriculture," says : " In this warfare that man must wage against his insect foes, he should not forget that nature has provided active and often very effective destroyers without which man could not grow crops, or even exist himself. Were it not for the many little enemies of plant-lice these insignificant creatures, with their wonderful powers of multiplication, would soon overrun the earth and destroy all vegetation, thus robbing man of his primary food supply. Among the forces of nature which thus aid man in his insect warfare may be mentioned strong winds, sudden changes of temperature in winter, rains, and forest and prairie fires. Then among the plants and animals there are some very efficient insect destroyers. Bacteria and fungi often kill a large proportion of army worms or chinch bugs that are devastating crops. Many of the birds feed largely on insects and should be encouraged to stay on every farm, for they are among the most efficient of nature's insect destroyers.

" But it is among their own kind, the insects, that insect pests find their most destructive foes. Vast numbers of insects, some so tiny that several of them can live inside an insect egg (codling-moth egg) not larger than a pin's head, are constantly preying on the insect enemies of man's crops. . . . A little lady-bird beetle (Fig. 102) saved the citrous industry of California. . . . And it would be impossible to grow wheat in many parts of the United States were it not for the tiny insect parasites of the hessian fly."

Experiment Stations and the National Department of Agri-culture are spending thousands of dollars each year to discover natural insect and plant disease enemies. Shall we allow a boy to become a man and the man to become a farmer without his school putting him in touch with this information ?

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