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Old Texas shrub the only source of `medical' rubber

This hamlet at the northern edge of the Chihuahuan Desert, just above Big Bend National Park, in the early 1900's was the site of the first US factory to produce rubber from a native source, the desert shrub guayule.

But after two decades the desert was virtually denuded of guayule, the Marathon factory closed in 1926 and the rubber industry turned abroad -- to Malaysia and Thailand and the Brazilian "hevea" rubber tree -- for cheaper, easier production.

Now USDA scientists, agronomists and industry executives are again agog about guayule (pronounced WY-OU-LEE), anticipating its growth by commercial farmers in the Southwest and its marketing to medical manufacturers for urgently-needed non-allergenic gloves, catheters and condoms.

Hevea rubber, it turns out, is fine for rubber tires, but the proteins in hevea latex rubber can cause allergic reactions ranging from contact dermatitis to anaphylactic shock. Up to 17 percent of all health-care workers and 80 to 90 percent of children who undergo numerous operations can be affected, sometimes with disastrous results, according to US government studies.

Efforts to resolve the problem, which broke out in the 1980s but became acute with the AIDS pandemic in the 1990s, "do not look promising" in using alternative synthetic or de-proteinized hevea rubber, according to Dr. Katrina Cornish, who heads the guayule research team at the USDA agricultural research service in Albany, California.

Cornish has begun the first year of a four-year, US$2.3 million research grant that is expected to lead to commercial production of guayule rubber latex. Her partner in the research is Dr. Mike Foster at Texas A&M agricultural research station in Pecos, Texas, and other genetic and agronomic researchers at the University of Arizona, New Mexico State University and the USDA lab in Phoenix, Arizona

According to Jeff Martin, the chief executive officer of Carlsbad, California-based Yulex Corp, which the USDA has licensed to use its guayule technology, there is also widespread interest for guayule from the chemical industry and for adhesives, gums and resins.

Yulex will begin commercialization of 4 to 5 million guayule plants next spring in Arizona and California, and he expects to manufacture and market the first guayule latex products in 2003.

The guayule plant is a yellow-flowered, silvery-leaved shrub that resembles common ragweed and grows about three feet tall in desert limestone soil at elevations of 1300m to 2300m. The plant produces rubber in its woody stems and roots, with considerable amounts contained in the roots.

During the early part of the last century, in Marathon and other guayule factories across the border in Mexico, the plant was harvested by ripping the plant from the rocky desert soil, then crushing the roots and stems with pebbles in a watery bath. John D. Rockefeller, Bernard Baruch and Daniel Guggenheim were among the early industrialists who backed guayule production.

Recently agronomists have discovered the plant will regrow rubber-producing stems for up to eight years if it is topped in the spring.

The plant increases its biosynthetic rate about 100 fold in the winter. Picking three or four times before the final root harvest avoids the labor-intensive replanting or reseeding except every fourth year.
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