by Busani Bafana

New Agriculturist, May 2009

With international demand for silk outstripping world production by 12%, communities in rural southern Zimbabwe could find themselves earning a significant income by commercialising wild silk from cocoons usually only collected to prevent livestock eating them.

Thanks to a pilot project initiated by a team of researchers at the National University of Science and Technology (NUST) and funded by the British Council, collecting wild silk cocoons-Tussah-could be a simple, yet lucrative venture for poor and ill-resourced villagers in Matabeleland South province.

Outbreaks of cocoons of the wild silk moth Gonometa postica have for many years posed a serious problem to commercial and rural livestock-farmers in Zimbabwe. The cocoons look very similar to the pods of the Acacia tree, but the silk is indigestible and gathers in the rumen of multiple-stomach animals, causing starvation. Therefore, rural communities have collected wild silk cocoons to prevent ingestion by livestock, especially during dry spells. Once collected, the wild silk cocoons were crafted by villagers into traditional leg rattles, unaware they were wasting a valuable natural resource.

When it was found that these cocoons were composed of wild silk, a new industry was pioneered to collect and degum the spent cocoons. "Wild silk is an important source of very expensive and sought-after silk threads, but until recently many villagers have not attached such value to them," says Dr. Abraham Nyoni, leader of the team researching wild silk, and Chairman of the Department of Textile Technology at NUST.

Rains may bring more silk worms

"Promoting the gathering of the cocoons has had the double benefit of ensuring that people realise the cash value from them whilst protecting the health of their animals. Unfortunately, wild silk is dependent on weather patterns: when there is no rain it does not occur," continues Nyoni. "Therefore, following heavy rains in some parts of Matabeleland South, there is now a good possibility of abundance of silk worms in areas where there have not been large numbers in the last ten years.

Nyoni explains that his research team will help communities to commercialise wild silk, which has to be prepared, cleaned and processed. The preparation involves immersing the cocoons in hot water to soften the sericin or gum holding the silk filaments to each cocoon, brushing the outside of the cocoons so that the end of the filament can be detected, and then unwinding the silk from a cocoon and combining the strands. The filaments from several cocoons are then combined.

Although the principle is simple, much skill and labour are required. Reeling is usually entirely manual, but in modern filature (the process of extracting silk from cocoons) steam power is used to rotate the reels, onto which the silk is wound, and automatic brushes brush the outside of the cocoons. The silk is then processed into a form suitable for weaving or knitting through what is known as 'silk-throwing'.

The wild silk project was initiated by Zimbabwe's national trade promotion body, Zimtrade, which had to suspend the project due to limited funding. Yet regionally, there is a ready demand for the unprocessed and semi-processed silk in South Africa with unprocessed cocoons fetching about US$1 per kilogram. However, the ultimate target market must be the tourism industry: a silk scarf can sell for up to US$90 at regional airports and fashion silk garments for substantially more.

Local de-gumming plant planned

Through the utilisation of this naturally occurring renewable resource, it is hoped that collecting cocoons and processing the wild silk locally will not only continue to alleviate livestock losses but also improve rural livelihoods through job creation and income generation. Already plans are in place to construct a local de-gumming plant and supply machinery in order to improve processing and silk quality. Training in spinning and weaving techniques is also being offered.

In addition, NUST is working with the Nelson Mandela Metropolitan University in Port Elizabeth in South Africa to investigate the characteristics of wild silk fibres and to look at their physical and chemical properties, while entomologists are being sought to help identify the different silk types. Wild silk can be used to produce high-value products, including sutures for use in hospitals, and sericin, the by-product of de-gumming, can be used in the cosmetics industry. This should ensure that this industry is not only environmentally but also economically sustainable.

This story, originally entitled Going wild for silk in Zimbabwe, appeared in the May 2009 issue of The New Agriculturist, an online magazine published by WRENmedia with support from the UK Department for International Development (DFID). Photographs: (top) wild silk cocoons (photo credit: Abraham Nyoni; (bottom) training in spinning and weaving techniques is being provided to improve processing and silk quality (photo credit WRENmedia). Both photographs appeared with the original story on the New Agriculturist website.