WHEAT INSECTS. In Europe fifty-three species of insects are recorded by Kaltenbach to feed upon wheat; in North America the number is surely much larger. Except the ehinch.laug and the Hessian Ily (qq.v.), which are the most dreaded, the following are the most important species.
The wheat-midge (Diplosis tritici) was prob ably imported into the United States from Europe, first into the Province of Quebec, spread ing gradually through the New England States into New York and westward throughout the Mississippi Valley. The orange or yellow adult insect, which appears in early smnmer and is one-tenth of an inch long, lays small and pale red eggs singly or in clusters in the crevices in the wheat-heads, from the kernels of which the small orange-yellow larva- extract the milky juice, causing the grain to shrivel and the heads to blight. When full-grown the larva-, which live about three weeks, descend to the ground and form small cocoons, in which they hibernate. Deep plowing of wheat fields and the prompt burning of chaff and screenings after threshing are the best remedies.
The joint-worm of wheat (Isosoina tritici), true gall-insect of the family Chaleiclid:r, most species of which are parasites, is a small, black, four-winged fly, a little over an eighth of an inch long. Its eggs are laid in the wheat-stalk, where the larvae produce little oblong galls, usu ally in groups of three or four, at or near the joints. (See Jonyr-Woam.) The Nvhent straw warm (Isosoma granite), a close relative which produces no galls, but lives on the inner surface of the stems, is of great interest, since it has an alternation of the generations, the sexual genera tion being wingless and rather small and the summer generation large, winged, and composed entirely of parthenogenetic females. Burning the stubble during the fall or winter is recom mended as a control for both these species. Several species of plant-lice are occasionally found upon wheat ; the wheat plant-louse (Nee tarophora cercalis), probably a European spe cies, is frequently troublesome.
The wheat bulb-worm (1/erontyza Amerieana) is, in the adult stage, a small, greenish, black striped fly of the family Oseinidar, which also attacks other cereals, timothy, and the blue grass throughout the wheat belt, where it develops three or more generations annually. The flies
lay their eggs upon the young plants, and the pale-green maggots work their way down to the crown and feed upon the central part of the stem, cutting it off and causing the central blade to wither. Prompt burning of the straw and stubble after harvest and rotation of crops are recommended.
The army-worm and the grass-worm (qq.v.) are dangerous enemies of the wheat crop, and there are several sawflies which do a lesser amount of damage.
The principal European insect enemies of Ole crop are the frit-fly (Oscinis frit), the Hessian fly, the wheat-midge. and a stem-borer—one of the-sawflies (Ceph us Dygmalts) just mentioned, which appears as an adult in April and deposits eggs in the stems of young wheat. The larvae bore through the joints and work up and down the stem, and when full-grown cut and almost saw the straw circularly on the inside near the ground, forming a cocoa]] in which they pass the winter as larvae, transforming to pupae and issu ing as adults the following summer. This in sect has been imported, and is known in Canada and New York, lint is rather scarce and does little damage; in Europe it is ranked as one of the principal enemies.
Stored wheat suffers from the attacks of sev eral insects. The granary weevil, the rice weevil, the Augonmois grain moth. the wolf moth, the Alediterranean mum moth, the Indian meal moth, the meal snout-moth, and several species of flour-beetles and meal-worms, as well as certain of the grain-beetles (see RAIN-1 NSECTS ), feed upon wheat in storage and after it is round. The remedies for all of these insects are practi cally identical, and comprise cleanliness and the treatment of bins or establishments with the vapor of hisulphide of carbon, or with hydrocyanic acid gas, both of which, however, should be applied with great care, and in aeeordanee with specific rules laid down by economic entomologists.
Consult: Marlatt, The Principal Insect Ene mies of Growing Wheat (Department of Agri culture, Washington, 1901); Chittenden, Some Insects Injurious to Stored Grain (ib., 1897).