The biggest worry weighing on the nation's food industry may not be drought in the West, farmworker shortages or turbulent international trade negotiations, but a change in the regulatory code in Vermont.
Under a law signed this month, the tiny New England state, population 626,000, will soon require that food companies tell consumers which products on grocers' shelves have genetically modified ingredients. In doing so, Vermont could force food growers, processors and retailers to upend how they serve hundreds of millions of customers nationwide.
The law puts Vermont at the forefront of a national movement that major food processors and agricultural companies are doing their utmost to kill.
Agribusiness firms and trade associations have poured tens of millions of dollars into political advertising and consultants to campaign against GMO labeling requirements and have enlisted members of Congress in a bid to outlaw state labeling rules. Industry officials have also vowed to sue Vermont, hoping to block its rule in court.
But although the industry has won several major battles on the issue — including ballot initiative campaigns in California in 2012 and in Washington state last year — the national push for GMO labeling has proved a resilient grass-roots effort, given added push by a broad swath of celebrity chefs, food writers and actors.
Connecticut and Maine already have laws that would impose labeling rules if enough neighboring states do the same, meaning that Vermont's move could help trigger action elsewhere in the Northeast. On the other side of the country, voters in Oregon probably will weigh in on the issue this fall, and a new California measure fell just two votes short in the state Senate on Thursday. About 1.4 million Americans have signed a petition imploring the Food and Drug Administration to implement labeling nationwide.
"Consumers want to know what is in their food," Vermont Gov. Peter Shumlin said. "Elected officials will have to meet the demands of consumers or be rejected at the ballot box. There is no doubt in my mind this will spread across the country."
At a signing ceremony, Shumlin talked up https://www.vtfoodfight.org, a website where sympathizers can give money to help the state fend off the industry's army of lawyers.
Some scientists at the forefront of food safety efforts find the crusade for GMO labeling to be perplexing, saying that consumers would be much better served with labels alerting them to pesticides or various other byproducts that taint food.
"There is this tribal mentality," said Pamela Ronald, a professor of plant pathology at UC Davis and author of the book "Tomorrow's Table: Organic Farming, Genetics, and the Future of Food."
"It has just become this progressive cause, and people are not spending time finding out the facts for themselves," Ronald said, pointing to prestigious scientific reports that have said foods made with genetically modified crops are no riskier than non-GMO foods.
But backers of GMO labeling argue that the issue shouldn't be about safety, but rather about a consumer's right to know. Orange juice from concentrate is safe, they note, yet the FDA requires it to be labeled. The U.S. is one of the few developed nations that does not mandate labels for genetically modified foods, they add.
The sentiment of Vermonters, the governor said in an interview, is reflected in an elderly Republican couple he recently met who cheered the labeling effort despite their distaste for big government.
"They told me, 'It makes us nervous when people don't want us to know what we are buying,'" Shumlin said.
The issue is thorny for President Obama, who expressed support for GMO labels during an Iowa campaign stop in 2007. A YouTube clip of Obama's comments posted by advocates has been viewed 840,000 times. The president does not need Congress to act. The FDA, whose head is appointed by the president, has the authority to mandate the labels.
For more than 2 1/2 years, the agency has delayed acting on the most prominent petition calling for GMO labels, filed by the Center for Food Safety.
"I am not able to offer a timeline," FDA spokeswoman Theresa Eisenman said in an email when asked about when the agency might act. "At this time, the agency has not made a decision, in whole or in part, regarding the petition."
The fight has spilled over to Congress, where Sen. Barbara Boxer (D-Calif.) and Rep. Peter A. DeFazio (D-Ore.) have enlisted dozens of sponsors for the Genetically Engineered Food Right-to-Know Act, which would impose labeling nationwide.
Allies of the big agricultural companies responded recently with a measure of their own that would strip states of authority to mandate the labels. The measure, by Rep. Mike Pompeo (R-Kan.), would also prohibit the FDA from mandating labels absent concrete findings that specific foods are unsafe.
"If there is no safety risk, why on earth would government be mandating anything?" Pompeo said in an interview. Food labels, he said, come with "an imprimatur of government that says, 'There is a reason we stepped in.' A lot of Americans will say, 'Goodness, the government only tells me about unhealthy things.'"
The argument that the FDA required labels on orange juice concentrate doesn't sway Pompeo. That's unnecessary too, he said. Nor is he swayed by the allegation that his bill would undermine states' rights, with which Republicans are typically loath to meddle. Pompeo said he worries a patchwork of different state and local labeling rules would wreak havoc on food suppliers.
"We could be talking about thousands of different jurisdictions making their own decisions about food laws," Pompeo said. "That is not a functional food safety system."
The point is not lost on advocates of labeling. It is, in fact, part of their strategy. Once a few states impose the requirement, they say, major food and agricultural companies and the FDA will be compelled to negotiate an agreement for a national standard.
"We could have as many as five states by the end of this year with mandatory labeling," said Colin O'Neil, director of government affairs at the Center for Food Safety. "Is the FDA going to allow them to dictate national policy, or will they step in with a federal blueprint? I suspect we are not going to see a patchwork go on much longer before the feds step in."
Proponents of labeling, meanwhile, feel less discouraged than they once were about battling adversaries who are so much bigger, richer and more politically connected. O'Neil argues that the zeal with which agriculture companies worked to crush the California initiative helped his organization and other groups enlist countless supporters.
"When people saw just how much money was being spent by Monsanto and the large multinational food corporations to keep consumers in the dark, that woke up the sleeping giant of the food movement," he said. "People began asking, 'What are you hiding and why?'"
The food companies say they have no plans to change their strategy.
"We will be countering them with facts," said Mandy Hagan, vice president of state affairs at the Grocery Manufacturers Assn. "We have the facts and the science on our side, and we will continue to deliver them."