Insects are the most numerous of all the animal species. In spite of their vast number perhaps not more than five per cent do any great harm to the farmer, yet the burden. is terrific. In 1894 there appeared in the southern counties of Texas a small beetle-like animal known as the boll weevil. It takes but fourteen days to develop from egg to adult and the progeny of a single pair may reach in a season 134 million. For some years it attracted little attention but, as was later discovered, kept spreading to the extent of some fifty miles a year. By 1912 it had crossed the Mississippi River, by 1915 had reached Georgia, and it is certain now to spread throughout the entire cotton-growing South. It feeds on the cotton bolls, the eggs being deposited in the unripe boll which is destroyed as the insect develops. It hibernates in cotton stalks or other plants. By 1903 it was thought that the damage done to the Texas cotton crop was some $15,000,000, but this was a wet season and particularly favorable to the weevil. Suffice it to say that in this immigrant the cotton planter finds his greatest enemy, and as yet no 19 Year Book of Department of Agriculture, 1904, p. 464. enemy has been found to check it. The natural enemy of the weevil in its own home, an ant, apparently will not live in our country, hence the plague. The total loss charged to its account down to 1914 is some $500,000,000 or 10,000,000 bales of cotton. Seven Mississippi counties in 1907 produced 171,790 bales. The boll weevil entered and the production in 1909 was 89,577 bales; in 1910, 61,432; 1911, 37,816, and in 1912, 30,909. The larvæ of the corn-root worm feed upon the roots of young corn and sometimes cause the loss of the entire field. This worm and a few similar species probably destroy two per cent of the crop year by year. The ear worm eats the kernels - particularly of sweet corn of which some 90 per cent of the ears are attacked and destroys not less than two per cent of the entire crop. Another two per cent goes to the chinch-bug. About fifty species of insects attack the corn and, in addition to the work of the three mentioned, probably reduce the crop another two per cent, making a total of eight per cent of the entire crop. Of the cereals wheat suffers most. The Hessian fly, chinch-bug and grain louse are its worst enemies. In some years over one-half of the acreage planted has been abandoned because of the Hessian fly alone. In 1900 Indiana and Ohio are estimated to have lost not less than $24,000,000 on account of this pest. The productiveness of the apple tree is reduced 5 per cent by the woolly aphis which attacks its roots, 2 per cent by the borers, and 10 per cent by the plant lice, scale insects and those that destroy the leaves. The codling moth, which lays its eggs in the young fruit through the country at large, causes a loss of not less than 20 per cent of marketable apples, while some estimates place the loss at 40 per cent. Add to this loss the $8,250,000 spent yearly for spraying and the codling moth has caused us a loss of nearly $20,000,000 yearly. The damage to stored products is greater than is realized. Tobacco, truck crops and cereals are attacked by worms, beetles, weevils and moths. The food waiting consumption at the house is visited by larder and ham beetles, various flies and moths. Mr. Marlatt is then justified in his statement: "The losses resulting from the depredations of insects on all the plant products of the soil, both in their growing and in their stored state, together with those of live stock, exceed the entire expenditures of the National Government, including the enormous pension roll and the maintenance of the Army and Navy." The damage done to domestic animals by such insects as gadflies, botflies, screw-worm flies, ticks and lice is put at $175,000,000 yearly.20 We must also keep in mind the enormous burden imposed upon agriculturists by the growth of weeds, the yearly loss in the United States being estimated at $100,000,000. Weeds affect agriculture in many ways. If plowed under they may furnish humus and thus be valuable. When growing in cultivated fields, however, they are injurious. They may form a dense mat on the ground which holds moisture, invites insects and may introduce disease. In other cases they may use water needed for crops. If it takes several hundred pounds of water to produce one pound of dry stalks the loss may be serious for the crop. Furthermore, weeds may appropriate a considerable part of the plant food in the soil and finally they may smother the crop by their dense rank growth. The wild plants, native or introduced, frequently 20 Year Book of Department of Agriculture, 1904, p. 461 ff. show such virility that their destruction is extremely difficult. Whenever man plows a field and plants his crop, he destroys thereby the bulk of the native flora. Now it may be that some one or two species are so persistent that they find the new conditions with the soil mellow and only the cultivated plants as competitors most favorable, and develop to the extent of occupying the ground and balking the farmer's hopes. In the Eastern states this frequently takes place whenever the native honeysuckle starts in a grass field. Even more common perhaps is the introduction of some new plant, frequently with the seed of the desired species. A very large part of the weeds in our country have been introduced from Europe. Chickweed, dandelion, plantain, Canada thistle and burdock are a few which every farmer knows. Gray's Botany of 1887 listed 2,893 species of native plants and 405 introduced — a goodly percentage of the latter must be classed as weeds. Weeds, incidentally, are plants for which we have no use, or are useful plants growing where they are not wanted. In the South, Johnson grass, a species of sorghum, is one of the most valuable fodder plants. In a cultivated field it is however the despair of the planter. Man engages therefore in a ceaseless warfare to protect his plants and insure crops. He must move his strawberry bed every year or two, not alone because of the rapid increase of the plants, but because of the growth of grass; he must change his hayfields, not merely for the sake of rotating crops, but chiefly to get rid of the weeds. The expert tells from the weeds on a farm the grade of the farmer. To keep undesired species from growing is thus a very important part of agriculture. Animals have food preferences, but what they actually eat is often more or less a matter of chance or necessity. It is interesting to note that the alimentary canal in carnivora is from three to five times as long as the body, while in herbivora it is from eleven to twenty-six times as long as the body. The fact that in man it is but seven times the body length may indicate that he is likely to cling to a meat diet. Fortunately for man seeds and insects are the chief food supply of many animals, especially the birds. Some oneThe great family of finches and sparrows find seventy-five per cent of their food in seeds of weeds. The proven record of the bob-white is amazing. seventh of our birds are primarily seed eaters. Number of Seeds Eaten by a Bob-white in One Day Barnyard grass 2,500 rose ..... Crab grass Dodder Evening prim ....... 600 Milkweed 10,000 Plantain 12,500 quar Round-headed 15,000 bush clover. 1,800 770 Smartweed 2,250 2,000 2,000 Peppergrass 1,560 Rabbit-foot 2,400 Water smart 12,000 weed White vervain 18,750 One hundred and twenty-nine different weeds are known to furnish food to the bob-white. "In Bulletin No. 21, Biological Survey, it is calculated that if in Virginia and North Carolina there are four bob-whites to every square mile, and if each bird consumes one ounce of seed per day, the total destruction to weed seeds from September 1st to April 30th in those states alone will be 1,341 tons." 21 Bob-white is partial to insects also. It is known to eat 145 species including such harmful varieties as the Colorado potato beetle, chinch-bug, wireworm, May beetle, 21 HORNADAY, W. T. Our Vanishing Wild Life, p. 220. |