sown cereals, of which the wild mustard is the most common. It is so common in spring wheat that the seed has become a by-product of flouring mills. The mustards are tall prickly plants with large leaves and bright yellow flowers. The wild mustard is distinguished from the black mustard on account of its long knotted pod being a stout two-edged beak. Seeds are dark brown to black, commonly spherical, one-twentieth of an inch in diameter, slightly granular-roughed. It has been found that by spraying wheat or oat fields with a three per cent solution of copper sulphate (about ten pounds to the barrel, or forty gallons, of water) at the rate of fifty gallons of solution to the acre, the mustard may be killed without injury to the cereal. The treatment is most effective if made in clear bright weather.

The black rust on wheat

145. Fungous Diseases. The more important fungi which attack the wheat plant are given below:

(1) Rust (Puccinia graminis Pers. and P. rubigo-vera (D C.))

(2) Wheat scab (Fusarium roseum Lk.) (3) Loose smut (Ustilago tritici Jensen.)

(4) Stinking smut (Tilletia foetens B. & C.)

Another little studied fungus causes rather conspicuous dark spots upon the glumes of wheat, and has been given the name of "glume spot." There is no known remedy.

146. RUST.-The rusts of wheat in the United States belong to two closely allied species, black stem rust and orange leaf rust, only the latter of which it is believed can pass the winter in the wheat plant.2 There are two stages of rust found on the wheat plant: (1) the red rust, caused by one-celled spherical uredospores, which commonly does not survive the winter, and (2) the black rust, caused by elongated two-celled teleutospores, which may pass the winter upon the ripened plant. It is believed that the rust plant may enter the wheat plant at the time of germination, or later if opportunity offers.

The loss caused from rust is difficult to estimate, but it is undoubtedly very large. It is encouraged by hot moist weather during the ripening period. There is nc

1 Cornell Bul. 216 (1904), p. 107.

2 P. rubigo-vera (D C.)

known remedy. A great deal of study has been given to the discovery or production of rust proof varieties of wheat, with as yet little if any success.

147. WHEAT SCAB.-The scab fungus is believed to be the conidial stage of a fungus which in its ascigerous stage is called Gibberella saubinettii (Mont.) Sacc. The fungus attacks the glumes, causing dead sections of the spike, whose brown color is in striking contrast with the green healthy glumes. At times the whole spike is destroyed. It may be identified by the pink incrustations at the base of the dead glumes and covering the rachis.

Usually the losses are inconsiderable, although under conditions favorable to the fungus, it may amount to ten per cent or more. There is no remedy known, but where wheat is to follow scabby wheat the burning of the stubble has been recommended.1

148. LOOSE SMUT.-This fungus belongs to the same genus as the smut so commonly found on maize. The spores adhering to the grain germinate and enter the young wheat plant through the sheath of the first leaf. The fungus grows within the wheat plant without external manifestation until the wheat plant is about to flower, when the whole spike except the rachis is reduced to a mass of black smut spores. The loss from loose smut is rarely large, although as high as eight per cent has been reported.2 The remedy is known as the modified hot water treatment and is as follows:

Soak the seed grain for four hours in cold water, let stand for four hours more in the wet sacks, then immerse for five minutes in water at a temperature of 133° F.; then dry and sow.3 Since this treatment injures the germinating power of the seed, one-half more seed per acre is required. The purchase of non-infected seed is also to be recommended.

Wheat spike with

scab: Upper portion has been destroyed by the pink fungus. Onehalf natural size, (After Selby.)

149. STINKING SMUT.-Stinking smut is closely allied to the loose smut of wheat, in form and habit, although differing from it in the character and extent of its injury. It affects only the grains, which are considerably enlarged, the interior being converted into blackish, offensive smelling masses of spores, which, when they find their way into the flour, make it unfit for food. The glumes being unaffected, the disease often escapes observation until after the grain is threshed. Losses from this smut are rather general and often considerable, amounting in some instances to at least forty per cent, which, practically speaking, ruins the crop.

Any one of the following remedies has been found effective:

(1) Hot water: Place seed in any bag or basket which will readily admit water and immerse for ten minutes in hot water at 133° F.; then cool quickly by immers ing in cold water or by stirring thoroughly while drying.

1 Ohio Bul. 97, p. 42.

2 Ohio Bul. 42, p. 93. 8 Ohio Bul. 97, p. 60.

(2) Blue stone or copper sulphate: Immerse for ten minutes in a solution of copper sulphate at the rate of one pound to five gallons of water. Allow to stand for ten minutes in bag or basket to drain; then spread and dry. Or the seed may be sprinkled at the rate of one gallon of the solution to four bushels of the grain sprinkling and stirring until thoroughly wet. At the end of an hour dry.

Stinking smut. Single grain much enlarged on the right. (After Kellerman.)

(3) Formalin: Treat seed by sprinkling o immersion for thirty minutes with a solution of one pound of formalin (forty per cent solution of formaldehyde) to fifty gallons of water.

In all treatments it is desirable first to stir seed into a tub of cold water and skim off the smut balls which rise to the surface. After treatment, the drying may be hastened by using slaked lime, but the lime is not essential.

150. Insect Enemies of Growing Wheat. More than one hundred species of insects are known to feed upon the growing wheat plant, but very few are sufficiently injurious to be of economic importance. These few, however, do enormous damage.

The chinch bug has been estimated to cause a loss of over a hundred million dollars to wheat alone in the

United States in a single year.1

The five most important insect enemies of wheat are as follows:

(1) The chinch bug (Blissus leucopterus Say.)

(2) The Hessian fly (Cecidomyia destructor Say.)

(3)

The wheat bulb-worm (Meromyza americana Fitch.) (4) The wheat midge (Diplosis tritici Kirby.)

(5) The wheat plant-louse (Nectarophora cerealis Kalt.) Of the above, the chinch bug and the Hessian fly are by far the most destructive, although the others frequently do considerable damage. Among the wheat insects of secondary importance

1C. L. Marlatt: The Principal Insect Enemies of Growing Wheat. U. S. Dept. of Agr., Farmers' Bul. 132, p. 6.

are the wheat straw worms, army worms, wheat sawflies. In the past, grasshoppers, especially the migratory species, have done enormous damage to wheat, but at present this class of insects usually do their greatest injury to meadows and pastures.

There are two general causes for the great damage done tc wheat and other grain crops by insects. The long hot summers and the present practice of growing somewhat continuously large areas of wheat on the same land produce favorabie conditions for their rapid multiplication. The rotation of crops and a more thorough and more intensive system of agriculture will tend to hold these insects in check.

151. THE CHINCH BUG.-The appearance of the six different stages from the egg to the adult chinch bug is shown in this paragraph. The newly hatched larva is of a pale reddish color

with a yellow band across the first two abdominal segments. As the insect changes from one stage to another it changes somewhat in appearance by becoming increasingly darker in color and finally in the adult form by the white wings. So that while

in the first larval stage

The chinch bug: Adult on the left; eggs upon the right; fou larval stages between. (Adapted from Riley and Webster.)

the color was principally red and yellow, in the adult form it is black and white There is also an adult form with short wings.

The chinch bug passes the winter in the adult form under any object which may offer protection from wet and cold. The grass stools of pastures and meadows, talks of maize, straw, rubbish in fence and hedgerows furnish them a winter home. 1ne eggs for the spring brood are deposited on the plants beneath the soil not far from May 1st. These eggs reach the adult stage during July; while the second brood reaches its maximum damage in August and its adult stage in September and October. It is the first brood that does the most damage to the wheat, rye or barley, and less frequently to oats, during the last few weeks of the growth of the crop. In the early part of July this brood migrates to maize fields, thereby injuring this crop also.

Preventive measures aside from those already mentioned (150) are the clean. ing up or burning of all rubbish or vegetation in fields and fence rows under which the chinch bugs may hibernate. There is no remedy for them while in the wheat

crop, but they may be trapped while migrating to maize fields by means of barriers of various sorts. Millet or Hungarian grass is probably the most effective. After the chinch bugs have congregated in the millet, they should be plowed under deeply,-preferably after spraying with pure kerosene oil. Usually, however, the chinch bug has migrated to the maize fields before protective measures have been inaugurated. The best remedy then is to spray with pure kerosene in the early morning when the chinch bugs will be congregated at the base of the maize plants. The kerosene will do some injury to the maize but not nearly so much as the chinch bugs.

The chinch bug is attacked by two parasitic fungi which tend to hold it in check. A number of experiment stations have propagated and distributed these fungi to farmers for the purpose of spreading them among healthy insects. It has been found, however, that this method is practically effective only during the moist cool weather when the insects are destroyed without the introduction of the disease germs. While the insects are young, even after they have wings, they are migratory in habit, but when the time for the union of sexes comes they take to wing and are no longer noticed by the casual observer. It happens that this occurs from one to three weeks after they migrate to maize fields. Frequently remedies have been reported effective, when in fact the disappearance of the chinch bugs was due to their midsummer flight.

152. THE HESSIAN FLY.-The Hessian fly is a small, two-winged, dusky-col

1 x h

Hessian fly: A, adult, about three times natural size;

B, flaxseed, slightly enlarged; C, larvae, slightly enlarged. (After Washburn.)

ored insect, about oneeighth of an inch long. It is distinctly a wheat pest, but it will also feed upon barley and rye. On account of its small size, the adult insect is seldom observed, and less seldom identified. Crane flies, much larger insects, often swarm about wheat fields and may be mistaken for the Hessian fly.

The Hessian fly is usually two-brooded, although it may be one-brooded in the northern spring wheat districts, or in the more southerly section of the United States may be three-brooded, the third brood living upon voluntary wheat in the summer months. When two-brooded, the fall brood reaches the adult stage during the latter part of August, during September and the first days of October, depending upon latitude and other seasonal conditions. The adults probably disappear with the first sharp frost. At any rate, the condition which is most favorable to the

'Cornell Bul. 194, p. 255.