three regulatory agencies -- the U.S.D.A., the E.P.A. and the F.D.A. -- have signed off on its products. Speaking of the New Leaf, Dave Stark told me, "This is the most intensively studied potato in history."

Significant uncertainties remain, however. Take the case of insect resistance to Bt, a potential form of "biological pollution" that could end the effectiveness of one of the safest insecticides we have -- and cripple the organic farmers who depend on it. The theory, which is now accepted by most entomologists, is that Bt crops will add so much of the toxin to the environment that insects will develop resistance to it. Until now, resistance hasn't been a worry because the Bt sprays break down quickly in sunlight and organic farmers use them only sparingly. Resistance is essentially a form of co-evolution that seems to occur only when a given pest population is threatened with extinction; under that pressure, natural selection favors whatever chance mutations will allow the species to change and survive.

Working with the E.P.A., Monsanto has developed a "resistance-management plan" to postpone that eventuality. Under the plan, farmers who plant Bt crops must leave a certain portion of their land in non-Bt crops to create "refuges" for the targeted insects. The goal is to prevent the first Bt-resistant Colorado potato beetle from mating with a second resistant bug, unleashing a new race of superbeetles. The theory is that when a Bt-resistant bug does show up, it can be induced to mate with a susceptible bug from the refuge, thus diluting the new gene for resistance.

But a lot has to go right for Mr. Wrong to meet Miss Right. No one is sure how big the refuges need to be, where they should be situated or whether the farmers will cooperate (creating havens for a detested pest is counter-intuitive, after all), not to mention the bugs. In the case of potatoes, the E.P.A. has made the plan voluntary and lets the companies themselves implement it; there are no E.P.A. enforcement mechanisms. Which is why most of the organic farmers I spoke to dismissed the regulatory scheme as window dressing.

Monsanto executives offer two basic responses to criticism of their Bt crops. The first is that their voluntary resistance-management plans will work, though the company's definition of success will come as small consolation to an organic farmer: Monsanto scientists told me that if all goes well, resistance can be postponed for 30 years. (Some scientists believe it will come in three to five years.) The second response is more troubling. In St. Louis, I met with Jerry Hjelle, Monsanto's vice president for regulatory affairs. Hjelle told me that resistance should not unduly concern us since "there are a thousand other Bt's out there" -- other insecticidal proteins. "We can handle this problem with new products," he said. "The critics don't know what we have in the pipeline."

And then Hjelle uttered two words that I thought had been expunged from the corporate vocabulary a long time ago: "Trust us."

Trust" is a key to the success of biotechnology in the marketplace, and while I was in St. Louis, I asked Hjelle and several of his colleagues why they thought the Europeans were resisting biotech food. Austria, Luxembourg and Norway, risking trade war with the United States, have refused to accept imports of genetically altered crops. Activists in England have been staging sit-ins and "decontaminations" in biotech test fields. A group of French farmers broke into a warehouse and ruined a shipment of biotech corn seed by urinating on it. The Prince of Wales, who is an ardent organic gardener, waded into the biotech debate last June, vowing in a column in The Daily Telegraph that he would never eat, or serve to his guests, the fruits of a technology that "takes mankind into realms that belong to God and to God alone."

Monsanto executives are quick to point out that mad cow disease has made Europeans extremely sensitive about the safety of their food chain and has undermined confidence in their regulators. "They don't have a trusted agency like the F.D.A. looking after the safety of their food supply," said Phil Angell, Monsanto's director of corporate communications. Over the summer, Angell was dispatched repeatedly to Europe to put out the P.R. fires; some at Monsanto worry these could spread to the United States.

I checked with the F.D.A. to find out exactly what had been done to insure the safety of this potato. I was mystified by the fact that the Bt toxin was not being treated as a "food additive" subject to labeling, even though the new protein is expressed in the potato itself. The label on a bag of biotech potatoes in the supermarket will tell a consumer all about the nutrients they contain, even the trace amounts of copper. Yet it is silent not only about the fact that those potatoes are the product of genetic engineering but also about their containing an insecticide.

At the F.D.A., I was referred to James Maryanski, who oversees biotech food at the agency. I began by asking him why the F.D.A. didn't consider Bt a food additive. Under F.D.A. law, any novel substance added to a food must -- unless it is "generally regarded as safe" ("GRAS," in F.D.A. parlance) -- be thoroughly tested and if it changes the product in any way, must be labeled.

"That's easy," Maryanski said. "Bt is a pesticide, so it's exempt" from F.D.A. regulation. That is, even though a Bt potato is plainly a food, for the purposes of Federal regulation it is not a food but a pesticide and therefore falls under the jurisdiction of the E.P.A.

Yet even in the case of those biotech crops over which the F.D.A. does have jurisdiction, I learned that F.D.A. regulation of biotech food has been largely voluntary since 1992, when Vice President Dan Quayle issued regulatory guidelines for the industry as part of the Bush Administration's campaign for "regulatory relief." Under the guidelines, new proteins engineered into foods are regarded as additives (unless they're pesticides), but as Maryanski explained, "the determination whether a new protein is GRAS can be made by the company." Companies with a new biotech food decide for themselves whether they need to consult with the F.D.A. by following a series of "decision trees" that pose yes or no questions like this one: "Does ... the introduced protein raise any safety concern?"

Since my Bt potatoes were being regulated as a pesticide by the E.P.A. rather than as a food by the F.D.A., I wondered if the safety standards are the same. "Not exactly," Maryanski explained. The F.D.A. requires "a reasonable certainty of no harm" in a food additive, a standard most pesticides could not meet. After all, "pesticides are toxic to something," Maryanski pointed out, so the E.P.A. instead establishes human "tolerances" for each chemical and then subjects it to a risk-benefit analysis.

When I called the E.P.A. and asked if the agency had tested my Bt potatoes for safety as a human food, the answer was ... not exactly. It seems the E.P.A. works from the assumption that if the original potato is safe and the Bt protein added to it is safe, then the whole New Leaf package is presumed to be safe. Some geneticists believe this reasoning is flawed, contending that the process of genetic engineering itself may cause subtle, as yet unrecognized changes in a food.

The original Superior potato is safe, obviously enough, so that left the Bt toxin, which was fed to mice, and they "did fine, had no side effects," I was told. I always feel better knowing that my food has been poison-tested by mice, though in this case there was a small catch: the mice weren't actually eating the potatoes, not even an extract from the potatoes, but rather straight Bt produced in a bacterial culture.

So are my New Leafs safe to eat? Probably, assuming that a New Leaf is nothing more than the sum of a safe potato and a safe pesticide, and further assuming that the E.P.A.'s idea of a safe pesticide is tantamount to a safe food. Yet I still had a question. Let us assume that my potatoes are a pesticide -- a very safe pesticide. Every pesticide in my garden shed -- including the Bt sprays -- carries a lengthy warning label. The label on my bottle of Bt says, among other things, that I should avoid inhaling the spray or getting it in an open wound. So if my New Leaf potatoes contain an E.P.A.-registered pesticide, why don't they carry some such label?

Maryanski had the answer. At least for the purposes of labeling, my New Leafs have morphed yet again, back into a food: the Food, Drug and Cosmetic Act gives the F.D.A. sole jurisdiction over the labeling of plant foods, and the F.D.A. has ruled that biotech foods need be labeled only if they contain known allergens or have otherwise been "materially" changed.

But isn't turning a potato into a pesticide a material change?

It doesn't matter. The Food, Drug and Cosmetic Act specifically bars the F.D.A. from including any information about pesticides on its food labels.

I thought about Maryanski's candid and wondrous explanations the next time I met Phil Angell, who again cited the critical role of the F.D.A. in assuring Americans that biotech food is safe. But this time he went even further. "Monsanto should not have to vouchsafe the safety of biotech food," he said. "Our interest is in selling as much of it as possible. Assuring its safety is the F.D.A.'s job."

Meeting the Beetles

My Colorado potato beetle vigil came to an end the first week of July, shortly before I went to Idaho to visit potato growers. I spied a single mature beetle sitting on a New Leaf leaf; when I reached to pick it up, the beetle fell drunkenly to the ground. It had been sickened by the plant and would soon be dead. My New Leafs were working.

From where a typical American potato grower stands, the New Leaf looks very much like a godsend. That's because where the typical potato grower stands is in the middle of a bright green field that has been doused with so much pesticide that the leaves of his plants wear a dull white chemical bloom that troubles him as much as it does the rest of us. Out there, at least, the calculation is not complex: a product that promises to eliminate the need for even a single spraying of pesticide is, very simply, an economic and environmental boon.

No one can make a better case for a biotech crop than a potato farmer, which is why Monsanto was eager to introduce me to several large growers. Like many farmers today, the ones I met feel trapped by the chemical inputs required to extract the high yields they must achieve in order to pay for the chemical inputs they need. The economics are daunting: a potato farmer in south-central Idaho will spend roughly $1,965 an acre (mainly on chemicals, electricity, water and seed) to grow a crop that, in a good year, will earn him maybe $1,980. That's how much a french-fry processor will pay for the 20 tons of potatoes a single Idaho acre can yield. (The real money in agriculture -- 90 percent of the value added to the food we eat -- is in selling inputs to farmers and then processing their crops.)

Danny Forsyth laid out the dismal economics of potato farming for me one sweltering morning at the coffee shop in downtown Jerome, Idaho. Forsyth, 60, is a slight blue-eyed man with a small gray ponytail; he farms 3,000 acres of potatoes, corn and wheat, and he spoke about agricultural chemicals like a man desperate to kick a bad habit. "None of us would use them if we had any choice," he said glumly.

I asked him to walk me through a season's regimen. It typically begins early in the spring with a soil fumigant; to control nematodes, many potato farmers douse their fields with a chemical toxic enough to kill every trace of microbial life in the soil. Then, at planting, a systemic insecticide (like Thimet) is applied to the soil; this will be absorbed by the young seedlings and, for several weeks, will kill any insect that eats their leaves. After planting, Forsyth puts down an herbicide -- Sencor or Eptam -- to "clean" his field of all weeds. When the potato seedlings are six inches tall, an herbicide may be sprayed a second time to control weeds.

Idaho farmers like Forsyth farm in vast circles defined by the rotation of a pivot irrigation system, typically 135 acres to a circle; I'd seen them from 30,000 feet flying in, a grid of verdant green coins pressed into a desert of scrubby brown. Pesticides and fertilizers are simply added to the irrigation system, which on Forsyth's farm draws most of its water from the nearby Snake River. Along with their water, Forsyth's potatoes may receive 10 applications of chemical fertilizer during the growing season. Just before the rows close -- when the leaves of one row of plants meet those of the next -- he begins spraying Bravo, a fungicide, to control late blight, one of the biggest threats to the potato crop. (Late blight, which caused the Irish potato famine, is an airborne fungus that turns stored potatoes into rotting mush.) Blight is such a serious problem that the E.P.A. currently allows farmers to spray powerful fungicides that haven't passed the usual approval process. Forsyth's potatoes will receive eight applications of fungicide.

Twice each summer, Forsyth hires a crop duster to spray for aphids. Aphids are harmless in themselves, but they transmit the leafroll virus, which in Russet Burbank potatoes causes net necrosis, a brown spotting that will cause a processor to reject a whole crop. It happened to Forsyth last year. "I lost 80,000 bags" -- they're a hundred pounds each -- "to net necrosis," he said. "Instead of getting $4.95 a bag, I had to take $2 a bag from the dehydrator, and I was lucky to get that." Net necrosis is a purely cosmetic defect; yet because big buyers like McDonald's believe (with good reason) that we don't like to see brown spots in our fries, farmers like Danny Forsyth must spray their fields with some of the most toxic chemicals in use, including an organophosphate called Monitor.

"Monitor is a deadly chemical," Forsyth said. "I won't go into a field for four or five days after it's been sprayed -- even to fix a broken pivot." That is, he would sooner lose a whole circle to drought than expose himself or an employee to Monitor, which has been found to cause neurological damage.

It's not hard to see why a farmer like Forsyth, struggling against tight margins and heartsick over chemicals, would leap at a New Leaf -- or, in his case, a New Leaf Plus, which is protected from leafroll virus as well as beetles. "The New Leaf means I can skip a couple of sprayings, including the Monitor," he said. "I save money, and I sleep better. It also happens to be a nice-looking spud." The New Leafs don't come cheaply, however. They cost between $20 and $30 extra per acre in "technology fees" to Monsanto.

Forsyth and I discussed organic agriculture, about which he had the usual things to say ("That's all fine on a small scale, but they don't have to feed the world"), as well as a few things I'd never heard from a conventional farmer: "I like to eat organic food, and in fact I raise a lot of it at the house. The vegetables we buy at the market we just wash and wash and wash. I'm not sure I should be saying this, but I always plant a small area of potatoes without any chemicals. By the end of the season, my field potatoes are fine to eat, but any potatoes I pulled today are probably still full of systemics. I don't eat them."

Forsyth's words came back to me a few hours later, during lunch at the home of another potato farmer. Steve Young is a progressive and prosperous potato farmer -- he calls himself an agribusinessman. In addition to his 10,000 acres -- the picture window in his family room gazes out on 85 circles, all computer-controlled -- Young owns a share in a successful fertilizer distributorship. His wife prepared a lavish feast for us, and after Dave, their 18-year-old, said grace, adding a special prayer for me (the Youngs are devout Mormons), she passed around a big bowl of homemade potato salad. As I helped myself, my Monsanto escort asked what was in the salad, flashing me a smile that suggested she might already know. "It's a combination of New Leafs and some of our regular Russets," our hostess said proudly. "Dug this very morning."

After talking to farmers like Steve Young and Danny Forsyth, and walking fields made virtually sterile by a drenching season-long rain of chemicals, you could understand how Monsanto's New Leaf potato does indeed look like an environmental boon. Set against current practices, growing New Leafs represents a more sustainable way of potato farming. This advance must be weighed, of course, against everything we don't yet know about New Leafs -- and a few things we do: like the problem of Bt resistance I had heard so much about back East. While I was in Idaho and Washington State, I asked potato farmers to show me their refuges. This proved to be a joke.

"I guess that's a refuge over there," one Washington farmer told me,