Monarch butterfly Caught in Corn Battle
Josephine Marcotty
Minneapolis Star Tribune
Sunday, August 27, 2000

A monarch feeds on the nectar of a Blazing Star. Despite everything that's known about the monarch, no one has looked much for the critter in cornfields. Until now it just didn't matter. Now it matters a lot. Monarchs have become the poster insect in the heated debate about the potential dangers of genetically modified corn.

Two studies, including one published last week, have shown that in the laboratory, monarch caterpillars die when they eat pollen from corn engineered to poison their cousin, the corn borer. The first of those studies, published in 1999, launched a passionate public and scientific debate on genetically modified food and a spurt of research that will eventually tell us a lot we didn't know about monarchs, including whether there are enough of them in cornfields to worry about. But that's not all. As the first suspected victim of bioengineering, monarchs' response may set a precedent for how science, industry, and the nation will wrestle with the questions posed by biotechnology. "This monarch thing is a triggering incident," said Eric Abbott, a professor of journalism at Iowa State University in Ames who has studied the debate surrounding biotechnology. "This is the first major one we face, and scientists and industry are paying more attention because they know it's not the last one."

The corn in question is called Bt corn. It was modified with a gene from a bacterium that makes a protein known to kill corn borers, the nemesis of farmers across the country, and particularly in the southern portion of the Midwest. Corn borers cause an estimated $1 billion in damage each year nationwide. Bt corn, first introduced in 1996, now comprises about one-third of the corn planted in the United States. Bt corn also has some other important benefits that often get lost in the debate, said Richard Hellmich, a scientist with the Agricultural Research Service, the research arm of the U.S. Department of Agriculture (USDA). Its yields can be up to 30 percent higher than traditional corn, and the quality is often higher because with less insect damage there is less mold. Bt corn contains the poisonous protein in each cell, including the pollen. It's a slam dunk against corn borers. If they eat Bt corn, they die.

For monarchs, and perhaps some of the other thousands of moths and butterflies in the genus lepidoptera, it's a far more complicated question. As many school children know from science class, monarch butterflies lay their eggs on milkweed. There the monarch caterpillars grow, subsisting on the plant as their only source of food. Then they spin their irridescent cocoons and hang from a milkweed leaf, emerging later as the instantly recognizable and beloved orange-and-black butterfly. Monarchs are at risk from Bt corn only if corn pollen happens to fall on the milkweed leaf they are eating, which is what the first study showed.

Cornell University entomologists John Losey and Linda Rayor fed monarch butterflies milkweed leaves coated with high concentrations of pollen from Bt corn, and found that many of them died. Suddenly, Abbott said, in the minds of the public the risks of biotechnology went from abstract, futuristic fears to the potential loss of a cherished butterfly here and now. This, after all, is the Minnesota state butterfly, made so last year by the Legislature at the behest of fourth-graders from Mahtomedi. "People in the United States have not been responsive to appeals that are based on Frankenfood," he said, referring to the term used by critics for genetically modified food. "But we respond to symbols, and it turns out this symbol was potent."

Rayor said this week that she and her research partners didn't intend to choose an icon. They simply were curious to see whether Bt corn affected other members of the lepidoptera family. She happened to have a colony of monarchs in her lab, and Losey had seen the caterpillars on milkweed near cornfields. Still, the study provided ammunition for antibiotechnology advocacy groups, and raised questions about whether the industry had sufficiently researched the widespread effects of Bt corn before putting it on the market.

Both government and industry representatives have tried to assure the public that the Bt corn poses little threat to monarchs because the pollen does not fall far from the field, and that the corn had to meet the same regulatory standards as pesticides before it was approved. When the U.S. Environmental Protection Agency licensed Bt corn, it assumed toxicity to insects related to the corn borer, said Kim Kaplan, public affairs specialist for the Agricultural Research Service. Because pollen is shed for only five to seven days "they assumed that the exposure was limited."

The "hoopla" about the monarch, as Abbott called it, resulted in the formation of a consortium of scientists from across the country who last winter put together a plan on how to determine what the real effects are. "I've been studying monarchs for 16 years, and suddenly they were hot," said Oberhauser. Habitat fit for a monarch Since then, a second report has been published. Released last week by researchers at Iowa State, it found that, again, monarchs were poisoned by Bt corn pollen. This time, however, entomologist John Obrycki and his colleagues took potted milkweed plants to Bt cornfields so that a naturally occurring amount of pollen would fall on them. They then took the plants back to the lab, measured the pollen counts and fed the leaves to monarch caterpillars. After two days of exposure, he said, 20 percent of the caterpillars died. After five days of exposure, 70 percent died. Of course, none of that matters if milkweed doesn't grow in cornfields, or if monarchs avoid the ones that do, or if they are not around when corn pollinates -- which is what Oberhauser is studying in collaboration with researchers around the country.

Her preliminary results have surprised her. Milkweed grows very well between corn rows, as Jolene Lushine and her fellow caterpillar hunters discovered this summer as they thrashed across miles of fields. The butterflies appear to especially like milkweed in that milieu. They lay more eggs per plant in the five cornfields she is studying than in the nonagricultural areas she compares them to, she said. "I thought milkweed [in cornfields] would not be apparent to the female monarch," Oberhauser said. "It's like a closed canopy forest, and they are flying over the top. [But in fact,] they are finding something growing under the canopy." Oberhauser said her students were finding one or two larvae per plant during the peak breeding period. "What this suggests to me is that cornfields are important milkweed habitats," she said. "It's scary."

She also found that corn pollinated at the end of July and early August. That's during the peak feeding time for a critical generation of monarchs -- the ones that migrate to Mexico in August and September. The next step, she said, is to find out how much milkweed grows in cornfields, and to make computer models that estimate what percentage of monarchs start their life under the corn. The risks before Bt Some scientists and industry representatives suggest that such information doesn't matter because even before Bt corn, pesticides to control corn borers killed countless monarchs as well. Bt corn poses less of a risk, they say, because it targets only corn borers. But Obrycki, among others, disagree. Before Bt corn, farmers used pesticides only occasionally because in many parts of the Corn Belt, the insects show up only sporadically. And the poisons were not that effective.

True to their name, corn borers bore deeply into the corn and consequently are shielded from sprays. Bt corn, on the other hand, is like an insurance policy: It's always there even when corn borers are not. Obrycki said that in 1995 only 2 percent of Iowa cornfields were sprayed for corn borers, but now 20 to 30 percent of the corn is Bt corn. As the research continues, the questions become increasingly complicated, Abbott said. Nevertheless, he pointed out, the history of technology tells us the process is crucial to ensure public trust. He likes to compare this latest technology to nuclear power. A lot of time and effort was spent trying to convince the public of the benefits of cheap, clean, nuclear energy, but the public never accepted it, he said. Now, that industry is virtually dead. As for genetically modified organisms such as Bt corn, "the jury is still out," he said.