For over a thousand years, sericulture in Thailand has been the rearing of native polyvoltine varieties of the bombyx morisilkworm. These worms subsist entirely on mulberry, and regenerate silkworm eggs several times a year. Native polyvoltine silkworms are hardy, resistant to the hourly lasting of local temperature and humidity and have adapted to the environment in which they have been reared over the years. This kind of silk yarns is the Thai indigenous silk yarn and is the only factor responsible for the uniqueness that contributes to what is called Thai silk, a national heritage.
Native sericulture is produced primarily in the Northeast of the country by farmers and their families during their spare times after the rice farming. Many farmers rear silkworms, hand reel silk yarns for home consumption. Some sell the excess to outside buyers, while others produce silk yarns mainly to supplement their income, and especially where it is a poor rain fed highland, many farmers and families make their living solely by this primitive sericulture.
Silkworm rearing, for the most part, is carried out on the poor Korat plateau. Farmers grow their own plot of mulberry and rearing the silkworm under their houses and reeling is done by hand by the women in the family. Production practically begins at the early raining days of May or as late in August, and ends when the raining day is over in December, when the entire mulberry leaves cease to grow. Any drought in a year often diminishes every production and years of heavy rainfall again give survival with more crops and more yields.
The cocoons they produce are bright yellow, oval shaped, and relatively smaller than white cocoons that originate in China and Japan. They are totally covered with silk filament and silk yarns can be reeled from the very beginning of the reeling process. The filament of this native cocoon can be hand reeled to give three different sizes of silk yarn. Namely, the outer part of the cocoon where the filament is heavier and coarser is reeled to give a third grade coarse silk. The middle part of the cocoon gives a medium size of yarn which is reeled to give a second grade silk and the very inner part, practically over 60% of the total silk yield, produces a very fine and even silk filament which is reeled to give first grade silk. Today farmers produce the first grade and the second grade combined and do not allow the second grade to be separated. The second grade therefore is no longer produced. Production of the second grade can only be done by reeling silk yarns without differentiating the third grade from the first grade. Farmers combine the third grade with the rest and call what they produce the second grade.
In order to increase productivity, the government silk stations set up by the Ministry of Agriculture have researched and developed high quality polyvoltine silkworm eggs and introduced them to the farmers for their traditional sericulture..
The official survey records about 300,000 traditional sericulture farmers in the country with an annual production of 400 to 900 tons subjected the amount of rainfall of the year.
Native polyvoltine is known for its luster, loftiness and dyeability.