Arizona is one of 20 states considering laws to require labeling of genetically modified foods.
The Arizona law, whose sole sponsor is a Senate Democrat in a Republican Legislature, isn't expected to gain traction this year. But backers of such legislation hope a multistate push eventually leads to federal labeling requirements.
Plant scientists say they don't object to labeling, but insist that genetically modified foods are no different from those produced through regular cross-breeding programs.
What is needed, they say, is better education about the promise and pitfalls of manipulating food genes. They also support stricter oversight.
A panel of scientists studied the issue at the request of the National Research Council. The group determined in 2010 that genetically modified foods are safe and that no accepted study of their health risks had concluded otherwise.
Yves Carrière, professor of insect ecology in the Department of Entomology at the University of Arizona, was a member of that panel, which also concluded that genetically modified foods hold promise for feeding a ballooning world population and meeting the impacts of climate change.
Science academies in Europe and Britain reached basically the same conclusion about safety. There are problems associated with the production of genetically modified crops, the report said, but safety is not one.
Most of us eat genetically modified food.
The much-reported and repeated statistic - that 75 to 80 percent of the processed food in the grocery stores contains genetically altered ingredients - is probably true.
The figure is from a years-old study done for the Grocery Manufacturers Association, said Brian Kennedy, the group's spokesman. It was based on U.S. Department of Agriculture statistics about the acreage of genetically modified crops grown in the United States, which has continued to grow.
Syrups and oils from that handful of crops are ubiquitous in processed foods.
In the produce section, most crops were developed the old-fashioned way. The exceptions are papayas engineered to be resistant to a mold that threatened to destroy the industry in Hawaii and some zucchini, yellow squash and sweet corn.
Other varieties have been developed but not successfully commercialized.
They will be, said entomology professor Carrière, who sees a big future for genetically modified vegetables if consumers can overcome their aversion to improvements made in the lab rather than in the field.
Humans have been genetically altering food crops for more than 10,000 years.
At first it was inadvertent. Those high-yield cereal grains that grew in the latrines of our hunter-gatherer camps were expelled and fertilized by people who had selected them for edibility.
You didn't need to know anything about agronomy or genetic improvement to make that happen. You just had to know the kernels were bigger or tastier.
Cultivation enabled our forebears to feed more people, settle down and specialize, rather than having to forage for their daily bread. It led to art and civilization and science.
That allowed us to speed up the process of agrarian development by more deliberate means - saving seed from our most productive plants, cross-pollinating and grafting.
We tend to think those things are mostly OK. Tangelos and brocciflower are in the grand tradition of scientists like Luther Burbank.
Genetic modification, especially the transgenic process of taking a trait from a different species to produce a tastier tomato or a faster-growing salmon, seems to be where we draw the line. Many of us also object to the notion that these scientific breakthroughs are being employed by industrial agriculture and used to produce crops grown strictly for cattle feed, biofuels or high-fructose syrup.
Only a handful of crops merit the title genetically engineered, but three of them - corn, cotton and soybeans - account for more than half the acreage planted in the United States each year, the U.S. Department of Agriculture says.
Our nation's sugar beet crop is almost exclusively genetically modified. In the case of corn and cotton, a common natural pesticide was appended to their genomes - Bacillus thuringiensis or Bt.
It worked well in places, with Arizona being one of the success stories. The state's cotton growers found that Bt cotton effectively controlled their principal pest, the pink bollworm, larva of a moth called Pectinophora gossypiella.
Cotton growers, working with university extension specialists, launched a full-scale campaign against the bollworm. They released sterile moths and sprayed fields with pheromones at mating times. In 2010, they announced the pest had been essentially eradicated in Arizona and Northern Mexico.
Cotton, corn and soybeans were also genetically modified to be resistant to the herbicide glyphosate, marketed by Monsanto under the name Roundup.
"Roundup is a really important herbicide," said plant pathologist Doug Gurian-Sherman, a senior scientist in the Food & Environment Program at the Union of Concerned Scientists. "It is generally considered less harmful than other herbicides."
More important, it kills a variety of weeds and breaks down relatively quickly, Gurian-Sherman said.
Its continuous overuse in Roundup-ready fields over the past 15 years, however, has led to the growth of resistant weeds, he said.
"It's a once-in-a-century herbicide," he said, "and we've largely squandered it."
Carrière, the UA entomology professor, blames the problems on a lack of careful oversight.
If farmers had rotated tilling with herbicide application, rotated crops or rotated herbicides, resistance would have been slower to develop, he said.
Pesticides are more regulated, but you still need a shifting strategy to thwart the evolutionary might of billions of mating insects.
Bt cotton and corn have had a good run, but resistance is developing, most recently with cotton in India.
Bruce Tabashnik, an entomologist at UA, has warned for years about the developing resistance, urging growers to follow strict protocols for Bt crops. His research helped develop strategies against the pink bollworm in Arizona, but his studies elsewhere turned up evidence of resistance.
Recently, he visited India, on a contract with a seed company, to investigate insect resistance to Bt cotton there. His initial impression is that lack of regulation was the cause. Farmers widely ignored the advice to plant refuges to make sure surviving moths did not pass the recessive resistance gene on to the next generation. Farmers also used black-market varieties of seed with lower levels of toxin, he said.
Tabashnik is now working with UA colleague Xianchun Li and Chinese researchers on similar problems in China, with a grant from China's national science foundation.
Sustainable use of genetically introduced pesticides requires vigilance, he said, but it can pay off.
He said Arizona cotton growers reduced their pesticide use by 75 percent with Bt cotton.
But resistance will develop, say biologists. "Evolution always wins," said Michael Nachman, UA professor of ecology and evolutionary biology.
Nachman made his remarks earlier this month at a wrap-up of the UA College of Science series on genomics, the mapping of the entire structure and function of genomes.
Feeding the world
Panelist Rod Wing, who has sequenced the genomes of a half-dozen food crops, compared the development to the bacterial strains that resist antibiotics.
Wing, director of the Arizona Genomics Institute, said he'd like to deploy the power of genomics to create "super varieties" of rice and other grains that can feed increasing numbers of people using decreasing amounts of arable land.
His is an open-source, public-interest approach, patterned on the work of people such as Norman Bourlag, who won a Nobel Peace Prize for triggering a "green revolution" in the 1960s. His work in Sonora developed a better wheat crop through cutting-edge breeding technology.
Plant pathologist Gurian-Sherman said genetically modified crops have failed to increase yield significantly and he urges caution with new varieties.
"You have to look at each crop and each gene combination separately," he said.
The EPA, where Gurian-Sherman used to work, regulates for pesticides, he said. Producers of genetically modified foods must simply show proof to the U.S Food and Drug Administration that new products are "substantially equivalent" to crops they replace.
"I reviewed a quarter of the data sent to FDA 10 years ago and nothing suggested that anything had slipped through that was dangerous," he said. "But the bottom line is that the FDA process is very weak."
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Contact reporter Tom Beal at email@example.com or 573-4158