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I. WEEDS, FUNGOUS DISEASES* AND INSECT ENEMDIS.
138. Weeds.—A great variety of weeds occur in the wheat field which may reduce the yield or injuriously affect the quality of the grain. In general they are to be avoided by those conditions which best promote the growth of wheat, and by sowing wheat that is free from foreign seeds.
There are a few species of plants that are so associated with the raising of wheat as to deserve special mention. The presence of a considerable quantity of any of these weeds in a wheat field must, of course, somewhat reduce the yield of wheat . But the principal injury, perhaps, is in the reduction in the quality of the grain, due to the presence of the weed seeds.
(1) Chess or cheat (Bromus secalinus L.)
(2) Darnel (Lolium temulentum L.)
(3) Cockle (Agrostemma githago L.)
(4) Wild garlic (Allium vineale L.)
(5) Wheat-thief (Lithospermum arvense L.)
139. Chess.—Chess belongs to a different tribe (Festuceae) of the grass family from that of wheat (Hordeae), which includes, also, some of our best known pasture and meadow grasses. It is an annual and so closely resembles wheat while young as not to be distinguished from it by the ordinary observer. It will stand more cold than the wheat plant, is not attacked by insects especially injurious to wheat, is a less vigorous grower than the wheat plant, but is much more prolific than wheat when its development is not prevented by the growth of the more vigorous wheat plant. The author sowed one pound of chess on one-twentieth of an acre and reaped ninety-nine pounds of seed. A single plant has been known to produce 3,000 seeds. The seeds which adhere to the paleae are so small that a pound of chess may contain as many seeds as a bushel of wheat. Experiment has shown that chess seed will grow when sown, and that the young plants can be distinguished from wheat plants. It has also been shown that when wheat only is sown in clean ground only wheat is obtained; that when wheat and chess are sown both wheat and chess
Chess. ( One-fourth natural size.)
are obtained, and when chess only is sown only chess is obtained. It has been shown further that in order to obtain seed from chess, chess must be sown the preceding falL When sown in the spring it does not produce seed for the same reason that winter rye and winter wheat do not. It is not found, therefore, in any but fall sown crops, and is less abundant in rye than wheat, because of the greater hardiness of rye as compared with wheat. The above habits are sufficient to explain the abundant development of this plant in wheat which has been injured by winter killing or by the Hessian fly when the sowing of clean seed has not been continuously practiced. The introduc tion of chess seed in the grain seriously injures its market value, as the chess must be removed before the wheat is ground. The machinery for this purpose in large milling establishments has reached great perfection. Hackel says that flour containing an admixture of chess will be da rk colored, remain moist and is narcotic. 1 Chess can be removed rather readily from the seed wheat by the ordinary fanning mills. When wheat is treated for smut, if the grains arestirred in the solu tion, any remaining chess seeds will come to the surface and can be skimmed off.
140. Darnel.—Darnel belongs to the same tribe of grasses as wheat, to the same genus as perennial and Italian rye grass. Unlike these grasses, however, it is an annual. It occurs in grain crops of Europe and is also reported occurring in wheat fields of California, where it is known as chess. This plant is supposed to be the "tares'" spoken of in the Bible. Like chess it is said to contain a narcotic principle which causes eruptions, trembling and confusion of sight in man, and in flesh-eating animals, and very strongly in rabbits, but does not affect swine, horned cattle or ducks.* Darnel may be removed from wheat intended for seed by the same method as chess.
1 The True Grasses, p. 168.
» Ibid, p. 17*
141. Cockle.—Cockle is a widely and anciently distributed weed of the wheat field, belonging to the pink family (CaryophyUaciat). It grows from one to two feet high and is readily distinguished by its large pink blossom. Its seeds are black, angular, kidney-shaped, one-half to one-eighth of an inch across, marked with spiny reticulations arranged in rows around the curved side of the seeds. They are quite injurious to flour, and as they are readily seen in the grain, reduce the commercial value of the wheat. They are so near the size and weight of wheat grains as to be removed with difficulty. They may remain in the ground several years without germinating. As the plant is rather conspicuous and its number usually not relatively large, they may be pulled from the growing wheat.
142. Wild Garlic.—This weed is sometimes found in the wheat fields of eastern United States. It grows one to three feet high and bears a cluster of bulblets in place of seed. "When these bulblets are ground with the wheat the flour is spoiled. Careful screening will remove the bulblets from the wheat. If the land is badly infested, it should be put into cultivated crops for at least two years.
143. Wheat-thief.—This winter annual is also known as bastard alkanet, corn gromwell, redroot, pigeonweed. It grows six to twelve inches high and has narrow rough hairy leaves. It bears a large number of inconspicuous whitish flowers in a leaf cluster in March and April. The seeds are hard and stony, dark, one-tenth of an inch long, roughened, conical with a narrow base, and borne in fours in the axils of the leaves. The plant is very hard to destroy, without destroying the wheat crop, which may in some cases be advisable. It is probably less of a pest to the wheat than it is to the subsequent meadows. Badly infested fields should be put into cultivated crops.
144. Wild Mustard.—There are two mustards, black mustard (BraaUa nigra, (L.) Koch) and wild mustard or charlock (B. sinaphtrum L.) found growing in spring
Wild garlic. (One-fourth natural size.)
sown cereals, ot 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 tlie cereal.1 The treatment is most effective if made in clear bright weather.
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.3 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 teUutospores, which may pass the winter upon the ripened plant. It is believed
the black rust on wheat. that the rllst 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 no
1 Cornell Bui. 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 saubineUii (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 1330 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.
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 1330 F.; then cool quickly by immers ing in cold water or by stirring thoroughly while drying.
1 Ohio Bui. 97, p. 42. * Ohio Bui. 42, p. 93. S Ohio Bui. 97, p. 60.