Stretched Too Thin

The development of domestic natural rubber couldn’t be coming soon enough.

It’s been pushed off the front page by stories about our dependency on foreign oil. Yet, our reliance on the often-overlooked natural rubber from far away places is perhaps just as critical an issue to our economy and way of life.

Natural rubber, also called latex, makes up about half the rubber used in the U.S., while man-made varieties comprise the other 50 percent. Yet, synthetic rubber, the manufacture of which requires petroleum, is considered inferior for many uses. For instance, while latex makes up a third of the rubber used in most automotive tires, it’s closer to 90 percent in high-performance and large tires. Without it planes don’t land, trucks don’t roll and tractors don’t farm. Many medical devices, too, such as catheters and surgical gloves, need the higher performance and greater elasticity of natural rubber.

But little known outside the rubber industry is that 93 percent of latex now comes from a little sliver of Southeast Asia. Perhaps, even fewer know how precariously positioned those trees now are.

Geographically, Hevea brasiliensis, usually referred to as the rubber tree, is limited by very specific needs of its tropical habitat. Pathologically, it’s susceptible to the South American leaf blight—the same disease that nearly rendered Hevea extinct in its native Amazon region and sent growers to the relative, and probably temporary, safety of places like Thailand, Indonesia and Malaysia.

The fungus that causes the blight had probably always lurked about in the Amazonian rain forest, yet its victims typically grew scattered or in small clumps, providing various populations a certain amount of protection. But by the latter part of the nineteenth century, industrial tycoons had begun to grow rubber on large South American plantations, where the trees grew in immense numbers in close quarters. It was then that the blight took hold and spread like the proverbial wildfire, wiping out as many as 300 million trees during multiple outbreaks that occurred over a period of about 50 years.

Lucky for the burgeoning industrialized world, British botanists had managed to save Hevea seeds and plant them in Southeast Asia, where the climate is similar to that of its native habitat and is free from the blight, at least so far.

Other outbreaks have occurred there, however, most notably during World War II. It was then that the Japanese took control of lands that grew 95 percent of the world’s latex, cutting off the U.S. and its allies. Rubber was not only needed to keep our jeeps, tractors and trucks rolling, but also our naval ships afloat. According to some historical sources, each Sherman tank used half a ton of rubber, while a U.S. battleship required some 20,000 rubber parts.

The war effort needed rubber to succeed, so the U.S. began recycling and severely restricted the use of rubber for non-essential products. It also launched a massive effort to find a substitute for Hevea, the main focus of which was a program to develop synthetic rubber. It resulted in an astounding increase, having gone from under 10,000 tons produced in the early 1940s to 800,000 by the end of the war.

In the meantime, another classified program had been launched to find and develop other sources of natural rubber, including varieties of Hevea that were immune to the blight and could grow again in Latin America. Even to this day, the effort has had little success. (More on this below.)

Scientists and other government officials also began cultivating a number of other potential rubber-producing plants, including guayule, a little known flowering shrub native to Mexico and the American Southwest. At one point during the war, some 30,000 acres had been planted. While it then produced less latex per acre than Hevea, guayule wasn’t susceptible to any known pests, required less water than most row crops and, most importantly, could be grown here on American soil.

Peacetime, however, heralded the return of Hevea supplies. And while synthetic rubber production was continued, the U.S. government dispensed with its natural rubber replacement programs, even classifying as top secret what it learned about its cultivation and processing. For reasons never fully explained, the files were stuffed away in the dustbins of history, while our concerns about rubber’s tenuous state were lost to our collective short-term memory.

The 70-plus years since the last major outbreak of leaf blight have lulled us into a sense of complacency, say many rubber-industry watchers. Yet, because much of the limited resistance Hevea had in South America has been bred out of those varieties grown in Asia—this to make them more productive—the trees are thought to be even more susceptible to an outbreak of leaf blight today.

There have been efforts to breed some resistance back into varieties of the tree, but they’ve been accompanied by a precipitous drop in rubber productivity. “We’re talking 30 percent lower productivity,” says Colleen McMahan, lead scientist for domestic natural rubber development for the USDA’a Agricultural Research Service (ARS). “That’s huge.”

What’s protected the Asian farms thus far are lots of preventive pesticides and the expanse of ocean between them and South America—the fungus that causes leaf blight has a thin wall and cannot survive a long journey. It could, however, survive the time it takes a modern airplane to travel the distance. That’s why those Asian countries with substantial Hevea farms reportedly do not allow planes from Latin America to even fly in their airspace.

It’s an open secret that an outbreak is possible, if not probable, but no one knows when. What we are able to better predict is that global demand for rubber over the next decade will outpace supply by 3 million to 4 million metric tons, according to the International Rubber Study Group, an intergovernmental organization that, well, studies rubber. That figure, fueled in large part by growth in China and India, represents about a quarter of current production.

So, the question is, even without a leaf blight invasion of Southeast Asia, where will new sources of latex come from?

Here in the States, most in the know agree that development of a domestic rubber program is critical and look to ARS to help. According to McMahan, a number of solutions have been explored over the years, including improvements to Hevea, and the cultivation of lettuces and Ficus, the latter a genus of plants that include everything from fig trees to houseplants. Yet, as she sees it, the two most promising today are Russian dandelion, another source that can be grown here in the States, and guayule.

“Guayule is definitely farther along in terms of commercialization; in terms of the domestication of the crop,” says McMahan. “But I do think that both guayule and Russian Dandelion have promise.

“I think in 10 to 20 years, we’ll have commercial sources, and I think from both. I think market penetration will be small—we’ll still mostly rely on synthetics and imports—but I think it will be a nice growth curve and there’s no doubt it will be used.”

And, says McMahan, the development of domestic natural rubber couldn’t be coming soon enough. The cost of petroleum, which is a key ingredient in synthetic rubber, is on the rise. As for latex, she says, “The price is skyrocketing, it’s at an all time high. It’s not a penny [increase], it’s a nickel every time you look. It’s really taking off.”

While those factors make it difficult for a number of rubber-dependent industries, McMahan notes, “that’s good for domestic rubber. I definitely think the future is the introduction of new crops in the U.S.

“Think about it,” she says. “What the U.S. has that many other countries don’t is land and a resourceful agricultural system. We’ve never had such an opportunity as now to develop these alternative sources.”

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