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Monday, 10 September, 2001, 21:39 GMT 22:39 UK
'Negligible' risk to butterflies from GM
Monarch butterfly
Monarch butterfly: A powerful US conservation symbol
By BBC News Online's Helen Briggs

Fears that genetically modified (GM) corn can harm butterflies were furthered on Monday, with the release of six environmental studies in the United States and Canada.

Long-awaited results of field trials indicate that a type of engineered corn is toxic to black swallowtail caterpillars.


I wouldn't say that butterflies are terribly at risk, given that the dangerous form is not being planted

May Berenbaum, University of Illinois
But the corn is being phased out in the United States. Scientists said the risk to butterflies from other types of genetically engineered corn was negligible.

The overall conclusion of the new research is that caterpillars living in cornfields are not likely to be exposed to levels of pollen high enough to be harmful, except for from one type of GM corn.

Risk 'manageable'

"I wouldn't say that butterflies are terribly at risk, given that the dangerous form is not being planted," May Berenbaum, professor of entomology at the University of Illinois at Urbana-Champaign, US, told BBC News Online.

"There is a potential for risk but it seems to be a manageable potential."

Black swallowtail caterpillar
Pollen from one BT corn was toxic to black swallowtail caterpillars
All biotech (BT) corn contains a bacterial gene that causes it to produce a toxin that kills pests that eat the plant.

A particular type of corn, called Knockout corn, appears to have a particularly high level of the toxin in its pollen.

The company which makes the corn, Syngenta, is withdrawing it from the market because of poor sales. The crop accounted for less than 2% of the total corn grown in the US in the year 2000.

"All forms of agriculture have environmental impacts," said Demetra Vlachos, Syngenta's senior manager for regulatory affairs in the US.

She said they were moving towards newer BT crops with less potential for environmental impact.

"BT crops are a new technology that have improved our environmental performance and are safer for the environment in the long-run," she told BBC News Online.

Alarm bells

Environmentalists first raised concerns about the effect of BT corn on butterflies following a lab study published in 1999.

The experiment showed that monarch butterfly caterpillars - which live on milkweed plants often found in or near cornfields - died when they were fed milkweed leaves dusted with pollen from engineered corn.


BT crops are a new technology that have improved our environmental performance and are safer for the environment in the long-run

Demetra Vlachos, Syngenta
A report last year at Iowa State University showed that toxic effects could be seen at pollen levels normally observed on the leaves in and near cornfields.

The new research - conducted by scientists in the United States and Canada and part financed by the US Department of Agriculture and industry - goes some way to addressing these concerns.

The six scientific papers, which were reviewed by Professor Berenbaum, are published online in the journal Proceedings of the National Academy of Sciences.

See also:

06 Jun 00 | Sci/Tech
Butterflies survive next to GM corn
20 May 99 | Sci/Tech
GM pollen 'can kill butterflies'
23 Aug 00 | Sci/Tech
More GM pollen evidence
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