Post Harvest Technology / Value Addition/ Marketing

According to Chinese records, the discovery of silk production from B. mori occurred about 2,700 B.C. Chinese legend states that the great prince, Hoang-ti, directed his wife, Si-ling-chi, to examine the silkworm and test the practicability of using the thread. Thereafter, Si-ling-chi discovered not only the means of raising silkworms, but also the manner of reeling the silk, and of employing it to make garments. Is-lingo-chi was later deified for her work and honored with the name Seine-Than, or "The Goddess of Silk Worms". Sericulture during the following centuries spread through China and silk became a precious commodity highly sought by other countries. In 139 B.C., the world's longest highway was opened, and stretched from Eastern China to the Mediterranean sea. In addition to tangible commodities such as gold and jade, new ideas and religions also passed along this road. This road was the historically famous "Silk Road," named after its most important commodity. By the middle of the first century A.D., writers in Rome were complaining about the sumptuous silk garments that rendered women naked in the streets. But the Chinese had guarded the secrets of sericulture so closely the early Romans never learned it, and Virgil thought the thread was derived from combing the fuzz off leaves.

In spite of their secrecy, however, the Chinese were destined to lose their monopoly on silk production. Sericulture reached Japan through Korea, but not before the early part of the third century A.D. Shortly after 300 A.D., sericulture traveled Westward and the cultivation of the silkworm was established in India. According to tradition, the egg of the insect and the seed of the mulberry tree were carried to India concealed in the headdress of a Chinese princess. The emperor Justinian gained the secrets of sericulture for the Roman Empire in 522 A.D., with the smuggling of the silk worm eggs form China by Persian monks. With China's monopoly on sericulture broken, silk importations from China became smaller and smaller. In 877 A.D., the rebel chief Biachu captured Canfu, the center of foreign silk trade, put to death all its inhabitants, destroyed all of the mulberry trees and silkworms of the region, and levied heavy and cruel taxes on all foreign trade. These actions stopped foreign commerce in China for more than 60 years. However, by this time, silk production was so well established in western Asia and eastern Europe that this wholesale destruction hardly effected the price of silk in the rest of the world. During the 18th and 19th centuries, Europeans also produced several major advancements in silk production. England by the 18th century led Europe in silk manufacturing because of English innovations in the textile industry. These innovations included improved silk-weaving looms, power looms and roller printing. In 1801, A Frenchman named Joseph Jacquard exhibited his new machine foe figured-silk weaving and gradually spread through the industry. The great French scientist, Louis Pasteur, rescued the silk industry in 1870 by showing that the then epidemic Pebrine disease of silk-worms could be controlled by prevention through simple microscopic examination of adult moths. These advances set the trend for a more mechanized and scientific approach to silk production than existed previously.

Sericulture has also been attempted in the United States, but these endeavors have been sporadic and largely unsuccessful. Sericulture was carried on to some extent by the early colonists of Virginia, South Carolina, and Georgia, and was introduced into New England about 1660. In 1831, a manual on sericulture was published by J.H. Cobb, copies of which were purchased by the Congress of the United States for distribution by members. Following publication of this book, there was a determined effort to establish silk culture on a firm basis in the United States. This interest in silk culture soon led to what was known as the "Mormus multicaulis craze." Anticipating a most profitable investment, if not speedy riches, thousands of individuals purchased mulberry plants of the M. multicaulis species and planted large areas of valuable land. The investments far exceeded possible returns, and heavy frosts destroyed plantations of trees. In the course of a few years, many failures and great disappointments caused so complete a revulsion of feeling that silk culture was practically abandoned all through the States. However, because confederate cotton was unavailable during and shortly after the Civil War, the Union States were forced to seek a new source of fiber. Thus in 1869, Professor L. Trouvelot, an American naturalist, brought eggs of the gypsy moth, Lymantria dispar (L.), from France to Massachusetts. Trouvelot had hoped to produce a commercial source of silk by developing a hardy race of silk-producing insects, crossing the gypsy moth with the silkworm moth, in order to control wilt disease (or flancheria) then causing severe problems in some silkworm industries. However, during the course of his experiments, some of the eggs were lost and some of the caterpillars escaped from his home. Although this accident was made public at the time it did not receive much attention even though the gypsy moth was immediately recognized as a pest. Since its introduction into the Boston area over a century ago, the gypsy moth has greatly expanded its range and become one of North America's most serious forest pests, defoliating large areas of canopy every year.

In spite of these earlier failures at sericulture in the United States, several more attempts at sericulture were made in California from the 1860's through the early 1900's. California sericulturists even advocated the commercial rearing of the native ceanothus silk moth, Hyalophara euryalus (Boisduval), as a possible source of silk until Felix Gillet in 1879 showed that the cocoons could not be reeled satisfactorily. Although some silk was produced in California during this time, most sericulture attempts failed and sericulture never became permanently established in the state.

Silk production today is a blend of ancient techniques and modern innovations. The first stage of silk production is hatching the silkworm eggs, which have been previously examined and shown to be free from disease. Larvae are then fed cut-up mulberry leaves and after the fourth molt climb a twig placed near them and spin their silken cocoons. The silk is a continuous-filament fiber consisting of fibroin protein secreted from two salivary glands in the head of each larvae, and a gum called sericin, which cements the two filaments together. Pupae within cocoons are killed by steam or fumigation to prevent adult emergence, which would cut and tangle the silk filaments. Cocoons are latter softened in hot water to remove the sericin, thus freeing silk filaments for reeling. Single filaments are drawn from cocoons in water bowls and combined to form yarn. This yarn is drawn under tension through several guides and eventually wound onto reels. The yarn is dried, packed according to quality, and is now raw silk ready for marketing.

World silk production has approximately doubled during the last 30 years in spite of man-made fibers replacing silk for some uses. China and Japan during this period have been the two main producers, together manufacturing more than 50% of the world production each year. China during the late 1970's drastically increased its silk production and became the world's leading producer of silk. The 1970's were a period of tumultuous political and social upheaval in China, resulting in various economic reforms. Undoubtedly, these reforms are partially responsible for China's increased silk production. Thus the country that first developed sericulture approximately 4,700 years ago has again become the world's main producer of silk