WAYNESBORO, Va. -- Armed with a shovel and a machete, two men entered a lush stand of corn ripening on a rolling Shenandoah Valley farm and began digging up stalks to examine the roots. The corn looked healthy, and entirely normal.

But below ground, something with potentially great implications was happening: An especially destructive and widespread pest, the corn rootworm, was being killed without the use of chemical pesticides. Genetic engineering was employed instead, and the men were there to study the results.

"Farmers don't like using soil insecticides," agronomist James Haldeman said as he tramped through the stand. "Some of them stink and they're nasty."

The sponsor of the field test, Monsanto Co., believes the new corn will be the next big development in crop biotechnology, transforming the way farmers control the worst pest of the nation's largest crop. If it does, genetic engineering could finally begin to realize one of its most tantalizing promises: helping the environment by allowing farmers to cut their need for chemical pesticides as never before.

"The issue of pesticide use is clearly a key concern for farmers, consumers and regulatory agencies," said Robert Fraley, the company's chief technology officer. "All three groups want to find alternatives to the current approaches. It's our strong belief that biotechnology offers a better approach, with considerably less impact on the environment than current insecticide use."

While some environmentalists are concerned about its safety and worried that it will quickly be overused -- saying Monsanto is more interested in making a profit than a safer world for corn growers and consumers -- even some who are usually skittish about tinkering with the genes of plants acknowledge the corn's possible benefits. Federal regulators, who are still studying its safety and effectiveness, are enthusiastic about its environmental advantages as well.

This response has raised hopes in the biotechnology industry that the corn can help ease the public's general queasiness about genetically engineered crops, which are highly controversial in Europe and increasingly so in the United States. Rootworm-resistant corn, the industry hopes, will refocus attention away from potential problems to the technology's ability to reduce the use of environmentally destructive farm practices and help feed the world's hungry.

"It's time for people to acknowledge that genetic engineering can lead to the use of fewer pesticides or less dangerous pesticides," agreed Michael Jacobson of the public interest group Center for Science in the Public Interest. "Environmentalists have been rightly concerned about chemical pesticides since Rachel Carson and 'Silent Spring,' and here is a real potential alternative."

Like many genetically engineered farm crops, the rootworm-control corn is created by splicing into seeds a gene from Bacillus thuringiensis (Bt) -- a family of soil bacteria that produces toxins fatal to many pests, but not to humans. The Bt genes produce different Bt toxins that kill different pests, essentially endowing the engineered plants with their own "biological" insecticide.

Pesticide Dependence

Research has generally concluded that Bt toxins are less harmful to the environment than chemical pesticides. While many chemical pesticides do a good job of killing harmful pests and weeds, they can also harm a broad range of insects (and sometimes birds and fish). If misused, they can affect people in and around farms as well. For decades, organic farmers have sprayed mixtures of Bt toxins as a natural insecticide.

Modifying crops to produce Bt toxins has helped reduce insecticide use in some crops, most notably cotton, and has allowed the widespread use of less harmful herbicides. But overall, federal statistics show, American farmers now spread about the same amount of pesticides as they did before the biotechnology revolution began.

That would clearly change if federal regulators approve the new corn modified to resist the rootworm, which costs farmers an estimated $1 billion a year and is the target of well over half of the 10 million pounds of insecticides used annually by corn growers. Monsanto hopes the new corn will be available in time for next spring's planting.

"We only have estimates now, but as much as 8.5 million pounds of insecticides would not be used if the [rootworm] technology lives up to the promise it's showing" in experimental test plots, said Stephen Johnson, assistant EPA administrator for the Office of Prevention, Pesticides and Toxic Substances. "That affords some rather dramatic decreases in insecticide use that would have a tremendous impact on both the environment and farm workers themselves."

An extensive review by the National Academy of Sciences last year found that pest control through biotechnology generally killed fewer creatures unintentionally and so was preferable to chemical pesticides. The use of genetic engineering, the report concluded, "could lead to greater biodiversity in [farmland] where they replace the use of insecticides."

Officials at Dow AgriSciences, which produces one of the most widely used chemical pesticides for controlling the corn rootworm -- Lorsban -- agree that genetically engineered rootworm control is the wave of the future. The firm, a unit of Dow Chemical Co., is developing a modified alternative to its own chemical insecticide that it hopes to have available by 2004.

"A good amount of rootworm control will go to that market because it's so effective and easy to use. That comes as no shock to us," said Stan Howell, a Dow vice president for insect management. "Actually, we hope to displace ourselves with our own [genetic modification] technology."

Doubters Persist

But some environmentalists do not agree that modified Bt crops are benign, and they are trying to block the new corn's approval. They say the rootworm-destroying corn is particularly troublesome because it is designed to produce Bt toxin at higher levels than in almost any other genetically engineered crop plant. They also worry that large amounts of Bt toxin could be released through the roots into the soil -- where it breaks down more slowly than the Bt toxins sprayed onto plant leaves in the sunshine. As a result, the modified corn could prove more harmful to beneficial bugs and worms.

And they are concerned that as more Bt variations are engineered into corn seeds to kill a range of pests, unforeseen effects could appear that each single use avoids. Their conclusion: Organic and other "sustainable" types of farming are the only long-term solution to pest control.

"While future genetically engineered crops could significantly shift or reduce pesticide use, they mean trading one set of inadequately researched and regulated health and environmental risks for another," said Skip Spitzer of the Pesticide Action Network, an environmental group. "They are not a sensible alternative."

Regulators are still examining the long-term impact of anti-rootworm corn on creatures living in the soil. Monsanto researchers have exposed many of them to large amounts of the rootworm-killing Bt and have reported that they were not harmed, or faced a risk far smaller than with most chemical pesticides.

Despite their concerns, some researchers and environmentalists acknowledge the especially great potential for pesticide reduction with the new anti-rootworm corn.

For instance, Charles Benbrook, a former agriculture specialist for the National Academy of Sciences, opposed the Monsanto rootworm application on behalf of the Union of Concerned Scientists on the grounds that there were too many environmental risks and unresolved technical questions. But he also said that "this is the first application of biotechnology to manage crop pests where there is some substantial potential to move away from chemical pesticide use, with all its negative environmental impacts."

The corn rootworm -- the larval stage of a beetle -- is widespread in the Corn Belt and very damaging if left untreated. The larvae eat the roots of plants and leave them unable to absorb water and nutrients. The insecticide DDT was widely used against the rootworm until it was taken off the market because of environmental concerns.

The pest is most common in states such as Nebraska where farmers plant corn year after year, rather than alternating it with other crops such as soybeans. Until recently, the rotation to other crops generally killed off the rootworm, but in some areas the pest has developed an ability stay alive in soybean fields. That, in turn, has increased the use of chemical pesticides.

Fears of Overuse

The prevalence of the corn rootworm and the tons of chemicals used to control it are what make it a potential textbook case in pesticide replacement. But the fact that it is so widespread also leaves farm specialists worried that the new biotech control could quickly become overused and ineffective.

Just as the rootworm developed an ability to withstand chemical treatments and to live in previously fatal soybean fields, they say, it can develop a resistance to the toxin in rootworm-resistant corn. The potential for Bt resistance is especially troubling to organic farmers, who depend on natural Bt varieties as their primary insecticide.

Michael E. Gray of the University of Illinois, a member of an EPA advisory panel on the issue, said he worries that farmers will see the new product as a "silver bullet."

"There is a definite concern that it will be embraced by producers in a way that will undermine its usefulness," Gray said. "The rootworm has a remarkable ability to adapt, and it will adapt to Bt quickly unless we are thoughtful and careful."

One possible brake on the use of the Bt corn for rootworm is that Monsanto says it will not sell the seed here until Japanese regulators have also given their approval. American public opinion will play a role as well, and consumer uneasiness has already stopped or reduced the development of genetically modified potatoes and corn-on-the-cob. "Farmers tell us they would like to grow it, and that it would cut back on [insecticide] applications a lot," said Greg Neusley of the University of Florida, who field-tested the sweet corn for Syngenta, an agribusiness company. "But their buyers don't want genetically modified corn, and they have to do what their customers want."

The Environmental Protection Agency, however, says it is actively looking for alternatives to chemical pesticides. It has a program to analyze and rank pesticide risks and to limit the more toxic ones, and Johnson, an assistant administrator, said genetically modified crops are expected to play a large role in future replacements.

Biotech critic Benbrook, who directs the Northwest Science and Environmental Policy Center in Idaho, said the Bt corn for rootworm will provide an "acid test" of the agency's sincerity about pesticide reduction.

"If they approve Bt corn for rootworm, they should restrict the use of organophosphates," a particularly toxic class of insecticides, Benbrook said. "That will show whether they're really serious about pesticide reduction."

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