European Corn Borer

EUROPEAN CORN BORER (Pyrausta nubilalis), a pyra lid moth of the subfamily Pyraustinae accidentally introduced into the United States from Europe and now considered to be a great potential pest to the principal agricultural crop of the States, namely Indian corn (Zea Mays). The species has a wide geo graphic range in the northern hemisphere, occurs all over Europe as far north as 58°. It occurs also in many parts of Asia, and in Pacific islands as far south as Guam and the Philippines. Its climatic range shows a variation from the dry steppes of south eastern Russia to the moist tropical conditions of Guam. It is known in Europe as an enemy of maize, hops, millet and hemp, and has many other food plants. It was probably introduced into the United States in broom corn coming from Hungary, having been discovered in 1917 near Boston, Mass., in 1919 near Sche nectady, N.Y., and in the same year near Buffalo, N.Y. There seems to have been an independent introduction in Ontario.

The insect spread rapidly, and is now found in Maine, New Hamp shire, Massachusetts, Rhode Island, Connecticut, New York, Pennsylvania, Ohio, Indiana and Michigan. In Massachusetts it has many food plants, known under the popular names pigweed, smartweed, cocklebur, barnyard-grass, lambsquarters, ox-tail, and panic-grass. West of Pennsylvania it is largely confined to the maize plant. There are two generations each year in New Eng land, but only one in its western range.

The female moth measures about an inch from tip to tip of the spread wings. The colour is variable, and ranges from pale yellow to light brown, the wings being marked by zigzag lines. The insect hibernates as a full grown larva in its burrow in the corn plant. In May or early June it transforms to a pupa within the stalk, remaining in this stage from ten days to two weeks. The moths issue, through holes previously cut by the larvae, in late June. They are active fliers, and ]ay their eggs in flat . irregular masses on the underside of the corn leaves, sometimes, however, on the upper sides, sometimes on the stalk or on the husk of the ears Each moth lays an average of 400 eggs. The eggs hatch in four to nine days. The larvae feed for a few days on the surface of the leaf, but soon enter the stem of the plant. In the midwestern States they become nearly full-grown by the middle of August, but remain within their tunnels throughout the winter. In New Eng land the moths issue in June ; their larvae become fully grown toward the end of July, and the moths from the second brood issue during August and early September. Their eggs hatch, and the larvae enter the stalks, becoming full-grown before the appear ance of cold weather. See ENTOMOLOGY : Injurious Insects.

Efforts at Control.

Extraordinary efforts have been made by the Federal Government and by the States to retard the spread of this injurious insect, at first by quarantines enforced by the in spection and seizure of all products likely to carry the borers, but it has been impossible to prevent the spread by the flight of the moths; and by the winter of 1926-27 midwestern farmers and stock-growers became so alarmed at the prospective damage that Congress was induced to pass an appropriation of $1o,000,000 to be spent in an effort to stop further spread in a radical manner; in other words, to enforce along the border of spread the destruc tion during the winter months of all portions of the plant remain ing in the fields. This effort was carried on with the co-operation of the States concerned during the late spring of 1927, and there can be no doubt that the result has been to retard the spread of the pest to a certain extent and to educate the corn planters of that part of the United States concerning the best methods of con trol. The corn borer becomes a serious pest only where corn stalks are allowed to stand in the field through the winter. During seven months of the year the full-grown larva remains in the lower part of the stalk. The mere pulling of the stalks and placing them in piles, as is done in certain parts of southeastern Europe, does not prevent the issuing of many moths in the spring ; the absolute destruction of the stalks and their contents is necessary. A method of corn culture has grown up in the larger part of the United States which is peculiarly favourable to the increase and spread of this pest, and a reform in this method, which seems simple, will prevent the enormous damage that has been feared. The experts of the Federal Government, aided by especial funds appropriated by Congress, have made extensive investigations of this insect since its discovery in Massachusetts and New York, in the effort to find control measures. Some of these investigators have been stationed in Europe and have made careful studies of European methods and conditions. These experts have especially investigated the question of natural control and have sent to the United States many thousands of specimens of European para sites of the borer which have been multiplied in the United States and liberated in the fields. See ENTOMOLOGY : Injurious Insects.

See the publications of the U.S. Department of Agriculture, particu larly Farmers' Bulletin No. and the publications of the State agricultural colleges and experiment stations. (L. O. H.)