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Monarch Butterflies in the News

by Randy Weckman, College of Agriculture

Photo of monarch butterflyThe monarch butterfly made headline news around the world in the fall of 1999, when environmental activists at the World Trade Organization's meeting in Seattle dressed as the colorful, migratory insect as part of their conspicuous protest of the growing of transgenic corn, specifically developed to fend off European corn borers, a moth especially widespread in the eastern United States. The insect's larva is a major pest in the stems and crowns of Indian corn, dahlias and potatoes. Transgenic crops are those developed to contain genetic material from another organism.

The protests were sparked by a laboratory study at Cornell University which suggested that caterpillars feeding on pollen from transgenic corn showed stunted development and a higher incidence of death. The transgenic corn had encoded into its cells a gene that produces a protein identical to that produced by Bacillus thuringiensis, a naturally occurring bacterium. That protein is lethal to European corn borers.

That modest study at Cornell resulted in a flurry of research activity concerning all facets of the monarch butterfly, including its feeding and reproductive habits. UK entomologist Ken Yeargan and undergraduate student Chanda Bartholomew did a study of their own on the colorful insect.

They found that the time when the transgenic corn sheds its pollen does not coincide with the sensitive reproduction time of monarch butterflies in Kentucky. The monarch butterfly lays her eggs on the milkweed plant, which is widespread throughout the United States, sometime after the pollen is shed. Other research has shown that the chemical in the pollen shed by transgenic corn is quickly degraded by sunlight. Thus, the butterflies can lay their eggs safely as long as there is opportunity for degradation of the chemical after pollen shed.

"Our research showed that reproduction of the insect occurs after pollen shed in corn grown in Kentucky. This finding suggests that concern about monarch butterfly reproduction being impeded by growing transgenic corn in Kentucky is exaggerated," Yeargan says. In Kentucky, more than a quarter of a million acres of transgenic corn is grown annually.

Further, he notes, because the transgenic corn supplies its own naturally occurring pesticide against the potentially damaging corn borer, farmers use considerably less pesticide to grow their crop than if they grew conventional varieties of corn.