Cotton

I

Introduction

Cotton, natural vegetable fiber of great economic importance as a raw material for cloth. Its widespread use is largely due to the ease with which its fibers are spun into yarns. Cotton’s strength, absorbency, and capacity to be washed and dyed also make it adaptable to a considerable variety of textile products.

II

Cotton Plants

Cotton is produced by small trees and shrubs belonging to the mallow family, which also includes hibiscus, okra, and the swamp mallow. The immature flower bud, called a square, blossoms and develops into an oval boll that splits open at maturity, revealing a mass of long white seed hairs, called lint, that cover a large number of brown or black seeds. When fully mature and dry, each of these hairs is a thin flattened tubular cell with a pronounced spiral twist and is attached to a seed. The length of the individual fibers ranges from 1.3 to 6 cm (0.5 to 2.5 in). Shorter fibers that grow from the seeds are called linters.

A few species are grown commercially; these range from a small tree of Asia, to the common American Upland cotton, a low, multibranched shrub that is grown as an annual. Another species includes the long-fiber Egyptian and Sea Island cottons botanically derived from the Egyptian species brought to the United States about 1900. Sea Island cotton thrives in the unique climate of the Sea Islands, located off the southeastern coast of the United States, and on the islands of the West Indies such as Barbados. As with Egyptian cotton, the fiber is white and lustrous but its fiber length is longer than that of any other type of cotton, which permits the spinning of extremely fine yarns. Pima, originally called American-Egyptian cotton, is a hybrid type. It is the only variety of long-fiber cotton now grown in commercially significant quantities in the United States, where it is cultivated under irrigation in the Southwest. Genetically modified cotton seeds have also been introduced, resulting in greater yields.

It is almost impossible to determine the original habitats of the various species of cotton. Scientists have determined fiber and boll fragments from the Tehuacán Valley of Mexico to be about 7,000 years old. The plant has certainly been grown and used in India for at least 5,000 years and probably for much longer. Cotton was used also by the ancient Chinese, Egyptians, and North and South Americans. It was one of the earliest crops grown by European settlers, having been planted at the Jamestown colony in 1607.

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III

Cultivation

Successful cultivation of cotton requires a long growing season, plenty of sunshine and water during the period of growth, and dry weather for harvest. In general, these conditions are met within tropical and warm subtropical latitudes in the northern and southern hemispheres. The U.S. Cotton Belt stretches from northern Florida to North Carolina and westward to California.

In the United States, production of the crop for a given year starts soon after harvesting the preceding fall, when many cotton farmers chop or shred the stalks with machines. The residue is plowed under and the land usually left rough until spring tillage. Planting time varies from the beginning of February in southern Texas to the beginning of June in the northern sections of the Cotton Belt.

A number of methods, chemical and mechanical, have been used to control weeds and grass, including intensive spraying of herbicide before and after planting. The cultivator, rotary hoe, and flame cultivator are also used to destroy weeds.

Nearly all cotton grown in the United States is now harvested mechanically with spindle-type pickers or strippers. Pickers are used extensively in irrigated lands. The picker has vertical drums equipped with wire spindles that engage and pull the cotton from open bolls. Strippers are used primarily in western Texas and western Oklahoma. They are “once over” machines that pull the bolls from the plant.

IV

Cotton Insects and Diseases

In addition to the flowers, the underside of each leaf of the cotton plant contains a small cuplike structure holding nectar. These deposits and the succulent stem make the plant attractive to a variety of insect pests. Chief among these is the boll weevil. The use of early maturing strains of cotton plus the application of several chemicals and control methods have greatly reduced losses from boll-weevil infestation. The bollworm, the pink larva of a small moth, is believed to have been a native of India but is now parasitic on cotton all over the world. The larvae burrow into the bolls and eat the seeds. In the United States the pink bollworm is largely confined to Texas and the western sections of the Cotton Belt. Quarantine, fumigation of seed, and destruction of trash removed from the cotton in ginning are control measures. The bollworm-tobacco budworm also is one of the most damaging cotton pests in terms of losses and control costs. Armyworm, thrips, lygus, and red spider are among other significant pests.

Among the serious diseases to which the cotton plant is subject is the wilt caused by a fungus that enters the roots from the soil and manufactures a poison. No treatment is known, but wilt-resistant strains of cotton have been developed. Another fungus disease is boll rot or anthracnose, caused by sac fungus. The best control is using seed from fungus-free fields.

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