Note: We've updated the headline on this post for the sake of clarity. To be clear, it's the apple and pear tree blossoms that get sprayed with antibiotics, not the fruit itself.

Apples and especially pears are vulnerable to a nasty bacterial infection called fire blight that, left unchecked, can spread quickly, killing fruit trees and sometimes devastating whole orchards.

"It's basically like a gangrene of your limbs. It's hard to stop" once it takes hold, says Ken Johnson, a plant pathologist at Oregon State University.

It's such a big threat that for decades, growers have seen two antibiotics, streptomycin and oxytetracycline, as vital weapons in the fight to control the disease — even on organic apples and pears.

But their use has raised questions about transparency in organic labeling, amid concerns about the overuse of antibiotics in food production.

"This isn't what consumers expect out of organics," says Urvashi Rangan, the director of consumer safety and sustainability at Consumer Reports. "Organic is supposed to be consistent in meaning," she tells The Salt.

Here's the back story.

When the U.S. Department of Agriculture's national organic labeling standards went into effect in 2002, the two antibiotics were listed as synthetic materials approved for use in organic apple and pear production. Items on that list are revisited on a periodic basis. The notion behind the exemption for these two fruit crops was that, in between reviews, growers would devise effective non-antibiotic-based methods for controlling fire blight.

But the antibiotic exemption is set to expire in October 2014. This week, the National Organic Standards Board is meeting in Portland, Ore., to decide on a petition from organic growers to extend that exemption. Consumers Union, the policy arm of Consumer Reports, is among the groups who say the answer should be a resounding no.

Antibiotics have been used in American plant and livestock agriculture since the mid-20th century. About 80 percent of all antibiotics used in the U.S. go to livestock — not just to treat disease and prevent infections, but also, primarily, to help animals put on more weight.

That heavy usage has been widely blamed for promoting the spread of antibiotic-resistant bugs. And resistance can jump from bacteria that infect livestock to microbes that sicken people. The problem of drug resistance has led to widespread calls for reining in the use of antibiotics on farms, in order to preserve the medicines' effectiveness in treating human disease.

But antibiotic use in plant agriculture is far more limited — just a little over one-tenth of 1 percent of total agricultural use, according to Virginia Stockwell, a plant pathologist at Oregon State University who studies fire blight management. Put another way, about 30 million pounds of antibiotics were used in livestock in 2011. By comparison, 36,000 pounds of antibiotics were sprayed on fruit trees — mostly on pears and apples, according to data she compiled from the USDA's National Agricultural Statistics Service.

In the U.S., up to 16 percent of all apple acreage and up to 40 percent of all pear acreage get sprayed with antibiotics each year, she says, citing data from NASS. That's including all organic and conventionally grown fruit. Not every orchard gets sprayed every year.

"There have never been any cases where we've been able to link an antibiotic-resistant pathogen in humans to orchards," says Stockwell, who recently conducted a review of the literature on the subject for the National Organic Standards Board.

Research suggests both of the antibiotics used on fruit crops are rendered inactive in soils, she says, minimizing concerns that residues that drift to the ground after spraying would be a problem. Any residue on fruit, she says, is minuscule.

That said, fire blight resistance to streptomycin is a concern for growers — it's now pretty common in orchards in the Pacific Northwest. That's one reason why growers have scaled back their spraying over the past two decades, Stockwell says.

"Everybody is committed to eliminating this use," says David Granatstein, a sustainable agricultural specialist with Washington State University, who works with organic farmers in his state.

But before all organic growers can completely give up antibiotics, he says, they need to have effective alternatives for preventing the devastation of fire blight.

Aggressive pruning has helped reduce reliance on antibiotic spraying. So has the use of biological controls, like bacteria that compete with E. amylovora, the microbe that causes fire blight, for nutrients on blossoms. But it's not enough.

Oregon State's Ken Johnson is one of several researchers overseeing field trials of two promising antibiotic alternatives. "I'd say we're fairly close," Johnson tells The Salt.

He's set to testify about these alternatives before the National Organic Standards Board on Wednesday. One option, called Blossom Protect, is a yeast-like fungus that blocks the fire blight bacteria from colonizing the blossom. It was registered for use with the Environmental Protection Agency late into last year's growing season, so this will be the first year lots of farmers can try it.

The other alternative, a copper sulfate that can be applied during bloom times without harming the fruit, has yet to be registered with the agency. Both are highly promising, according to Johnson — but they need more testing. So 2014, he says, is still a bit too soon to say goodbye to antibiotics.

"Most people," he says, "when their livelihoods depend on it, want to see a few years of positive data before they're convinced that it is the right thing for them."

Note: We've updated the headline on this post to avoid the potential for misinterpretation. To be clear, it's the apple and pear tree blossoms that get sprayed with antibiotics, not the fruit itself.Copyright 2016 NPR. To see more, visit