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Corn+Soybean Digest

Bt Benefits People - And Butterflies

Bt corn is under attack as a result of two university research projects reported in scientific journals this year. But entomologists claim the findings were misinterpreted by environmentalists and consumer groups, and used to build consumer concerns about all genetically modified (GM) crops.

Eventually, say the entomologists, science will win out, the controversy will wane, and farmers, consumers and even butterflies will continue to benefit from Bt technology.

The most publicized Bt study was the Cornell University trial involving monarch butterflies. The Cornell researchers coated milkweed leaves with Bt corn pollen in the laboratory, then allowed butterfly larvae to feed on the leaves. Some larvae died and some survived but developed abnormally. Other larvae survived and developed normally after the four-day study ended.

Anti-GM groups viewed the findings as a threat to monarch butterflies and released the story with fanfare to news media around the world. The resulting tumult, including protests in the U.S. and Europe, convinced some food processors to stop using Bt corn and products made from it.

Many entomologists believe what happened in this lab study could hardly be repeated in the field.

Iowa State University (ISU) researchers also concluded that monarch larvae could be affected by pollen from Bt corn. But some of them doubt that it poses a true threat to butterflies or any other non-target species.

Even if monarch adults lay eggs on milkweeds in or around Bt cornfields, the potential for significant monarch mortality is "infinitely small," points out ISU entomologist Marlin Rice.

So far, there have been no documented cases outside the lab of any ill effects from Bt corn on any non-target species. But Rice says the Cornell and Iowa State studies suggest a need for field research to ensure that there are no unintended consequences of using Bt crops.

The other side of the story, says Rice, is that farmers growing Bt corn use less insecticide, giving all non-target species in and around cornfields a better chance of survival.

Growers don't need to avoid the technology next year "if they have a market for the corn or intend to feed it," says Rice.

"In the long run, we have three choices regarding Bt corn hybrids," he adds. "We can use them. We can plant non-Bt hybrids and use broad-spectrum insecticides to control corn borers. Or, we can plant regular hybrids and do nothing to control borers.

"If you think corn borer is not a serious pest, either of the last two options is fine. But corn borer can cause significant damage, even in years when pressure is low. If we use the technology, we need to choose the management program that is less threatening to the environment and is safer for farmers and consumers. The choice is obvious to me," Rice says.

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