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Killer Corn II
June 06, 2000

"I like being my own boss, I like the challenge of putting seeds in the ground and growing a crop," says Iowa farmer Rod Pierce.

Rod Pierce loading genetically-altered corn seed.

Pierce uses corn which had its DNA changed so that it expresses the gene of Bacillus thuringiensis—commonly known as Bt—which produces a toxin that kills European corn borers, bugs that regularly destroy corn crops in some parts of North America. This year he planted 80 percent biotech corn—the maximum allowed under EPA guidelines—and 100 percent biotech soybeans.

"It provides a better yield and it also reduces the amount of insecticide we have to apply to our crop," says Pierce, citing the two main reasons advocates of genetically engineered crops want to continue the practice.

But others aren’t sure if it’s such a good idea. Even though the Food and Drug Administration says the foods are safe, some consumers worry that these crops produce inadequately tested "frankenfoods." Likewise, scientists have also been grappling with the question of whether genetically altered foods are safe for the environment. In response to public pressure, companies such as Frito-Lay, Gerber, and McDonald’s have stopped using some biotech ingredients.

Now a new study that shows genetically modified corn has no adverse effects on black swallowtail butterflies is sure to fuel the debate, providing ammunition for both sides of the issue and new pressures for America’s farmers.

Conflicting results

A Monarch caterpillar

A controversial lab study last year by researchers at Cornell University showed that Monarch butterfly caterpillars that eat milkweed leaves dusted with Bt corn pollen will die. But the study took place in the laboratory, not the field, so it didn’t take into account factors such as weather and wind conditions that affect how much pollen the Monarchs are actually exposed to.

Now, researchers at the University of Illinois have published the first field study examining the effects of Bt corn on black swallowtail caterpillars. The study appeared in the Proceedings of the National Academy of Sciences.

"There’s no mortality that we observed in black swallowtails that’s attributed to exposure to the pollen from genetically manipulated corn," says nationally renowned entomologist May Berenbaum, one of the authors of the study.

Researchers placed plants with black swallowtail caterpillars at varying distances from a cornfield in Illinois to see how much pollen was carried by the wind and how it affected them. In addition, they exposed black swallowtail caterpillars to higher doses of pollen in the lab. They found that in both cases the caterpillars suffered no adverse effects.

But other questions are raised

The black swallowtail

When choosing GMO (genetically modified organism) seeds, farmers have several possibilities from which to choose; some seeds are modified to produce less toxin than others. Like Pierce, the University of Illinois researchers used Bt corn that contained Monsanto event 810—meaning it is produced by Monsanto and contains a particular gene that expresses Bt toxin. This type of corn, which Monsanto licenses to more than 200 seed companies, is the most widely planted biotech corn in the country.

But other types of corn that produce more toxin are available, and the researchers also tested Novartis variety Max 454, containing event 176. In this case, their results coincided more closely with the Cornell study. They found that this type of corn did kill the black swallowtail caterpillars.

Other research supports this finding. Scientists at Iowa State University studied the effects of pollen containing varying amounts of toxin on Monarch butterflies and found that pollen containing more toxin—in this case event 176—killed more caterpillars than pollen that had less toxin.

The European corn-borer

The study, first presented to the Entomological Society of America late last year but not yet published, tried to pinpoint the effects of Bt corn pollen on Monarch butterfly caterpillars that were placed on milkweed plants at different distances from a cornfield. Not surprisingly, the closer the caterpillars were to the field, the higher the chance they would die. "The big question we answered was what are the densities of pollen landing on milkweed plants in and near cornfields—and also showing that those densities can have a negative effect on the Monarch butterfly," says Laura Hansen, who wrote the study with John Obrycki.

But some scientists urge caution when predicting environmental consequences from biotech crops. "I think the question of possible hazards is a serious question, but preliminary results suggest dire predictions are way out of line," says research entomologist Rich Hellmich of the USDA Agricultural Research Service. Summing up the data that’s available, he says pollen that could affect Monarch butterflies usually goes only three or four meters from the cornfield.

Monsanto spokesperson Bryan Hurley says the University of Illinois study is important because it shows that nature can differ from the laboratory. "It shows there’s a need to not accept research at face value without understanding all its implications," he says.

As for Pierce, he says farmers try to keep their fields free of the milkweed that Monarchs feed on anyway. "We do take steps to keep that weed out of our fields. And we feel the Monarch goes to the non-crop areas where the milkweeds are present and chews on the milkweeds there," he says.

More information is needed

While Berenbaum’s study shows that one type of genetically modified corn had no ill effect on one type of insect, there is still debate as to how toxic Bt corn is to different insects. "We need to be more systematic about what species might be affected," says John Losey, the lead scientist on the Cornell University study last year who is continuing his research on Monarch butterflies this summer. "It might be hundreds, it might be much fewer."

"Genetically engineered crops that are available are not extensively tested, and the test data are not readily available," notes Berenbaum. "So I think if growers were provided with more information—not only about efficacy against pests, but also about non-target effects—they would be better able to make informed choices."

The FDA recently recommended voluntary labeling of genetically modified food products, but some groups think labeling should be mandatory. "Until the consumer feels confident in the safety of genetically modified foods, they will continue to refuse to purchase them," says Gary Goldberg, CEO of the American Corn Growers Association. "Whether for the right or wrong reason, mandatory labels would have, at the very least, instilled consumer confidence."

Consumers may not even be aware that they re purchasing GMO products, however. More than half the soybeans grown in this country are genetically engineered, while 25 percent of the corn is biotech. So, while the French fries at a fast food establishment may not come from GMO potatoes, it’s possible that the soybean oil used to fry them is biotech. In fact, besides being used in oil, GMO corn and soybeans are used to prepare a wide variety of products, including packaged snacks and breakfast cereals, as well as livestock feed.

The controversy continues, but in the meantime, another growing season is here, and Pierce is confident there will be buyers for his corn. "Our local elevators were very upfront this year when they stepped forward and reassured us they would accept all approved biotech crops for export at no discount," he says. Some growers who chose not to plant genetically engineered crops this season are hoping for a premium on their exports this fall.

Meanwhile, Hurley predicts further research will actually show a benefit to insects from Bt corn, because farmers who use it don’t have to use large quantities of pesticides. "We’re hearing anecdotal evidence of beneficial insects in the fields," he says, adding that bioengineered crops can help avoid the wasteland created by insecticides.

Elsewhere on the web:

The Alliance for Better Foods

The FDA’s page on bioengineered foods

The USDA’s page on agricultural biotechnology

Facts and Figures on Food Biotechnology from the Grocery Manufacturers of America

Survey results on consumers’ attitudes about food biotechnology from the International Food Information Council

EPA Lawsuit over Bt crops



produced by Jill Max


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