Sugar Crops

Some Problems in Growing Sugar Beets

George H. Coons.

Sugar beets are grown for sugar in 22 States Michigan, Ohio, Indiana, Illinois, Wisconsin, Minnesota, Iowa, Kansas, Nebraska, South Dakota, North Dakota, Colorado, Montana, Texas, New Mexico, Utah, Idaho, Oregon, Washington, Arizona, Wyoming, and California. They are grown in New Mexico, Arizona, Utah, Nevada, California, and Oregon for seed.

Almost 20 percent of the national Sugar requirement is obtained from the domestic production of sugar beets. Beet sugar produced in the United States is in demand for food and for the chemical, pharmaceutical, fermentation, and heavy industries.

The byproducts of the sugar beet tops, molasses, and pulp are used chiefly as a feed for livestock. Beet molasses is also highly important in the fermentation industry, particularly for the production . of citric acid. Beet pulp, the slices of beet from which the sugar has been extracted, is fed in wet or dry form to cattle.

Nearly 670,000 acres of sugar beets were harvested in 1952. On that acreage 10,217,000 tons of sugar beets were grown and were processed in 68 factories. The approximately 1,532,000 tons of sugar (raw value) produced from the sugar beet roots contributed nearly 20 percent of the estimated national sugar consumption of 7,900,000 tons. Production in 1951 was much like that of 1952, 700,000 acres being harvested and about 10,500,000 tons of sugar beets being grown. In 1950, on 924,000 acres, 24.5 percent of the national sugar requirement was produced.

Disease-resistant varieties have been used almost exclusively to grow the American sugar beet crop. To obtain the seed for growing the commercial crop of sugar beets for the factories to process, the industry maintains several seed-producing enterprises.

Beet sugar can only be produced in factories equipped to carry on the complicated chemical processes necessary to extract and purify the sugar that is stored in the roots. Usually the beets are grown within a radius of 40 to 6o miles of the factory. A highly intensified culture on the best lands nearby is the result; on the farms themselves, sugar beets are usually the main cash crop, and farmers have been tempted to grow beets on the same fields repeatedly rather than to make them part of a rotation system. Twin problems of diseases and lowered fertility consequently have arisen; indeed, the history of the industry as it moved from the Eastern States westward, and then sought in place after place for suitable production areas, reflects the damage done by curly top, leaf spot, and root diseases.

Curly top by 1926 had caused repeated failures of the sugar beet crop in States west of the Rocky Mountains. In years of outbreak, the average acre yields from some districts dropped from an expected 15 tons to 5 tons or less. The history of sugar beet culture in the Truckee project of Nevada, Salt River project of Arizona, Delta and other areas in Utah, the San Joaquin Valley of California, the Yakima Valley of Washington, and many others is all much the same a brief period of fine prospects and then crop failure because of curly top, with ultimate abandonment of sugar beets by farmers.

Congress in 1929 appropriated funds for investigations of curly top and the beet leafhopper. All aspects of the problem were attacked quickly. Thanks also to some earlier research, progress in the development of varieties resistant to curly top was immediate. By 1933, seed was being increased of the resistant variety that was introduced in 1934 as U. S. 1. Since then, U. S. I and the other resistant sorts that followed in quick succession U. S. 34 U. S. 33, U. S. 12, and U. S. 22 have removed from western agriculture the threat of crop failure from curly top.

It cannot be said that curly top is vanquished. Severe exposure in the worst years still takes its toll. But farmers may now plant the new varieties with confidence that the crop will be carried through to a reasonably high yield despite disease.

Meanwhile the producers farther east were being plagued by sporadic epidemics of leaf spot. Leaf spot, caused by the fungus Cercospora beticola, blights the tops so that root growth is dwarfed and the percentage of sucrose is cut. Its effects are less dramatic than those of curly top, but it occurs more widely and is more damaging to the industry.

Leaf spot is a wasting disease. It can reduce tonnage and sucrose enough to make the beet crop unprofitable to farmer and factory. The blight years are those in which rainy periods are frequent in the early half of the season and total rainfall is abundant the very conditions that should give a bumper crop bring only disappointment as wave after wave of leaf blighting occurs. In epidemic years, leaf spot may kill back the entire foliage bouquet several times in a season. New growth is pushed out only to be blighted in 2 or 3 weeks. Replacement of blighted leaves is at the expense of root growth and stored sugar, hence the crop is lacking in weight and quality. Between 1915 and 1930, blight years were frequent. Factories in the Midwest and in the more eastern districts were in financial distress.

The first leaf spot resistant variety, U. S. 217, was introduced in 1938 by the Department of Agriculture. Its average production of sugar was 5 percent more an acre than that of the susceptible European varieties. It was soon replaced by U. S. 200 x 215, a hybrid variety that served the industry from 1940 to 1944. It gave higher root yields than U. S. 217 and was at least 8 to 10 percent superior to European varieties if leaf spot was prevalent. U. S. 215 x 216 was introduced in 1945- It became the leader in the humid area. Without leaf spot, it is as productive as the nonresistant European types; if leaf spot is serious, it is at least 15 percent superior in production of sugar.

Still another disease contributed earlier to the general instability of our beet sugar industry the seedling and root disease complex that farmers call black root. It occurs all over the United States but is worse in the humid area. The primary cause of black root of seedling beets is the water mold, Aphanomyces cochlioides. Other damping-off organisms are associated in the seedling disease complex but are less important or more readily controlled. Black root may kill so many of the seedlings that the stands after thinning are below or on the border line of profitable production. If rainfall in spring is slightly above normal or if the soil is infested with damping-off organisms, the initial stands of seedlings are so reduced by fungi that only gappy stands can be left after thinning.

Heavy planting rates were used formerly in an attempt to have extra large numbers of seedlings from which a fair stand of thinned beets could be saved. In recent years, to save manpower in singling sugar beets, seeding rates have been reduced. Destruction of the meager initial stands by black root thus causes even greater damage than before. According to factory records, parts of Michigan and Ohio often have had average stands in their fields considerably below 70 percent much too low for profitable growing of the crop.

In seasons of severe black root, replanting of 25 percent of the acreage around a factory has been necessary. The sugar beet cannot attain stable production and full mechanization is not possible until disease-safe varieties are available. U. S. 216; a leaf spot resistant inbred was also found to be outstanding in its resistance to black root. The superimposing of resistance to black root upon resistance to leaf spot seems entirely feasible in varieties built around U. S. 216 and its close relatives. A number of selections resistant to black root have been made from varieties resistant to leaf spot. Varieties that were ready for introduction in 1953 combine resistance to leaf spot with moderate resistance to black root. They are equal to nonresistant strains when disease is absent and superior when leaf spot and some black root occur. Plant breeders hope they will solve the problem of black root.

WEATHER CONDITIONS sometimes produce effects on sugar beets that resemble symptoms of disease. Hot, dry winds may cause scorching of the edges of leaves. Such leaf scorch should not be confused with blighting by fungus. Sugar beets are relatively hardy, but early frosts may injure the emerging plants. Such an injury may be distinguished readily from damping-off of seedlings.

Heavy fall frosts kill the upper leaves, which become black and water-soaked and then dry out and turn white. Growers recognize this condition, even though they might not understand the effects of severe freezes and the reduction in sucrose of the roots that may follow. Low temperatures in late October or November may kill all leaves. If warmer weather follows, the killed foliage is replaced by a new growth at the expense of the food reserves in the root, thus lowering the sucrose percentage. Often a farmer is puzzled by sugar tests after a freeze that show a much lower sugar content than the earlier tests. Wherever feasible, after tops are severely frozen the harvest should be delayed to permit the foliage to be replaced and the plant again to store sugar in the roots.

A bolt of lightning may kill all plants in an area 10 to 50 feet in diameter in a field. The plants die suddenly, as if affected by disease. Each day for nearly a week the circle of dead plants widens. The lightning, hitting the field just after the surface soil was wet by rain, distributes itself and grounds through the beet roots, electrocuting them. The least affected plants in the outer parts of the circle die more slowly.

Hail may cut and bruise petioles and crowns of plants but (except when the plants are very young) does not kill the beets. The plants put out new leaf growth. The loss caused by hail is therefore according to the amount of injury to foliage, except that wounds may offer points for the entrance of disease organisms. Because sugar beets can recover from hail injury, farmers in districts subject to frequent hailstorms include this crop in their farming program as a safeguard.

SHORTAGES OF NUTRIENTS in the soil produce definite reactions on the sugar beet plants. A deficiency of phosphate produces telltale effects that are especially marked on the older leaves, which then curl upward and inward. The edges of the leaves and the tissue between the veins die and turn black. An affected plant stands out markedly from its neighbors. A single plant may show this evidence of phosphate deficiency the surrounding plants being apparently normal or a number of plants in a group may be affected. Less severely affected plants show reduction in growth, greater susceptibility to black root, and secondary invasion by weak parasites of the Cercospora beticola spots on the leaves. The enlargement of the lesions by the secondary organisms that follow leaf spot is so striking in fields deficient in phosphate that the cercospora spots, instead of appearing grayish brown, take on the form that growers call black blight.