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The Hill Country Gardener  

Science vs. the Monarch Butterfly… all in the name of progress

In 1999, the monarch butterfly went from simply a lovely work of nature to the focus of a firestorm of controversy and varied opinions when results of laboratory testing indicated that butterfly larvae died after eating milkweed dusted with pollen from genetically modified Bt-corn.

The monarch butterfly, while in its larval or caterpillar stage, feeds only on milkweed plants.  Here in the Midwest where corn is a major crop, it is common for milkweed to grow in close proximity to cornfields.  Therefore, it is likely that pollen from corn, which can be blown more than 60 yards by the wind, may settle on milkweed plants.  When large numbers of monarch caterpillars feeding on milkweed growing near a cornfield began dying, it was discovered that the milkweed they had eaten was dusted with pollen from Bt-corn.  Media reports and public outcry fueled one of the most contradictory issues to challenge agricultural scientists in recent memory.

The hybrid crop called Bt-corn is the result of genes of the bacterium Bacillus thuringiensis (Bt) being spliced into normal corn genes.  Bt-corn was developed as a control for the European corn borer corn pest.  It is reported to be safe for human consumption and to have no adverse effects on beneficial predators and non-target organisms such as honeybees and ladybugs.

In the spring of 1999, an independent study was conducted at Cornell University in New York under controlled laboratory conditions.  Corn pollen was collected from both normal corn and Bt-corn and dusted onto dampened milkweed leaves.  Leaves with no pollen at all were also included in the study as a control.  Three-day-old monarch larvae were released in three separate containers with the leaves and allowed to feed for four days.  On the forth day, the caterpillars were removed from the containers.  Caterpillar mortality, caterpillar weight, and milkweed leaf consumption were recorded.

The results of the study showed that 44% of the caterpillars died that ate leaves with Bt pollen, but no caterpillars died that ate leaves with regular pollen coated leaves or leaves without pollen.  The caterpillars ate fewer of the Bt pollen dusted leaves than those dusted with either regular pollen or no pollen at all.  The caterpillars that did not die after eating leaves dusted with Bt pollen were less than half the size of caterpillars that ate leaves from the other two groups.

In 1999, approximately 30% of the corn acres planted in the Corn Belt were planted with Bt-corn.  Bt-corn has proven to be a highly effective pest management option for corn growers since it offers almost 100% control of the European corn borer.  Monetarily, Bt-corn is valuable for reducing pesticide use and guarding the crop against yield loss.  In 1998, the U.S. Department of Agriculture also approved for commercial use genetically transformed potatoes and cotton, and 18 other Bt-engineered crops were authorized for field testing.  Many of those are likely in use now.

For over twenty years, biotech labs have been genetically engineering our fruits and vegetables in the interest of better taste and pest resistance.  With issues like Bt-corn it is no wonder more and more people are becoming concerned about these “Frankenstein foods” and what damage could be being done to the food chain.  Dictionary.com defines “Frankenfood” as  “A genetically modified food, especially a fruit or vegetable.”  Martin Teitel, Ph.D. and Kimberly A. Wilson exclaimed in their article, Are You Eating Frankenfood?, “The genetic engineering of our food is the most radical transformation in our diet since the invention of agriculture 10,000 years ago.”  Jeremy Rifkin of the Foundation on Economic Trends would like to see a moratorium on all genetically engineered crops until further studies can be conducted on their environmental effects. 

On the other hand, Bt-corn is manufactured by Monsanto Co., Pioneer Hi-Bred, DEKALB Genetics Corp. and numerous other seed producers.  When asked about the monarch butterflies and Bt-corn pollen, Monsanto Co. spokesman Randy Krotz said the Cornell University test findings were not very important.  He continued by saying that not many monarch butterflies would be exposed to the toxic Bt pollen since milkweed does not grow near cornfields. 

Research conducted by the U.S. Department of Agriculture (USDA) found that approximately half of the cornfields tested in the Corn Belt contain milkweed.  According to John E. Losey, primary investigator on the study at Cornell University and assistant professor of entomology, “Milkweed grows best in disturbed habitats, like the edges of cornfields.”  In the spring monarch butterflies migrate north out of Mexico into Texas and other Gulf Coast states.  They search for milkweed where they can lay their eggs and feed.  Around the first of June, a new generation of adults begins the flight north to various areas including the Midwest Corn Belt.  “Monarch caterpillars are feeding on milkweed during the period when corn is shedding pollen,” Losey said. “They may be in the right place at the right time to be exposed to Bt-corn pollen.”

Corn producers are continuing to plant Bt-corn as if nothing alarming was discovered.  In 2005, in the United States 28.6 million acres of Bt-corn were planted, which accounts for approximately 35% of the total U.S. corn crop.  In the Midwest, the following states planted the indicated percentages of their state total 2005 corn crop in Bt-corn:  Iowa 46% -- Kansas 33% -- Minnesota 44% -- Missouri 43% -- Nebraska 51% -- Wisconsin 28%