Monday, August 21, 2000

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Public discussion of the impact of Bt corn on monarch butterfly populations was originally spurred by a single, four-day laboratory study conducted by Dr. John Losey of Cornell University and published in the May 20, 1999, issue of Nature. In the study, monarch larvae fed milkweed leaves artificially coated with Bt corn pollen ate less, grew slower and suffered a higher death rate than larvae that consumed milkweed leaves free of corn pollen.

By design, Losey`s research did not mimic natural conditions. In the laboratory, the caterpillars were given no choice but to feed on leaves artificially covered with corn pollen. Under actual field conditions, a complex series of events must fall into place for there to be even a possibility that Bt corn pollen may cause any harm to monarchs.

* The monarchs must be in their larval development stage, a period which last just 12 to 16 days.
* The monarch larva must be feeding at the same time corn is pollinating, a narrow period of seven to 10 days.
* The milkweed plant that the larva feeds on must be located near a Bt cornfield.
* Bt corn pollen must fall on the particular milkweed leaf that the caterpillar is feeding on.
* The caterpillar must consume the pollen before rain or dew washes it away.

To determine what impact, if any, Bt corn pollen has on monarchs in their natural environment, a coalition of leading scientists from government, universities and Extension fielded a series of independent studies in 1999, and continued their work in 2000. The results of their initial studies were presented on Nov. 2, 1999, at the Monarch Butterfly Research Symposium in Chicago. Key findings from this extensive body of field research include:

* Monarch migration and Bt pollen shed may not coincide. Dr. Galen Dively, pest management specialist and professor of entomology at the University of Maryland, monitored Maryland cornfields and monarch development in 1999. He found that corn plants had completed pollen shed before monarch caterpillars were first observed feeding on milkweed. Similarly, Dr. John Foster, professor of entomology at the University of Nebraska, observed that by late July, corn pollination in Nebraska was 95 percent complete before monarch eggs were observed on milkweeds in near corn.
* Monarchs prefer milkweed away from corn. Tests by Dr. John Losey, Cornell University assistant professor of entomology, show that monarchs avoid laying eggs on milkweed surrounded by corn. Further, researchers from USDA-Agricultural Research Service (ARS) and Iowa State University found that when given a choice between feeding on milkweed leaves with no pollen or high levels of Bt pollen, the majority of monarch larvae chose no pollen.
* Corn pollen doesn`t travel far. Researchers at Stanford University, University of Guelph, Iowa State University and University of Maryland conducted independent studies to evaluate the spread of corn pollen. In each case, the scientists found that corn pollen levels decrease rapidly a short distance from the field edge.
* Milkweed density is highest along roadsides, not corn fields. Dr. Doug Buhler, research agronomist for USDA-ARS and Dr. Robert Hartzler, associate professor and Extension weed scientist at Iowa State University, found that Iowa roadsides typically had 48 common milkweed patches per hectare, while corn and soybean fields had only seven patches per hectare.

Additionally, the following scientists could provide more information on the relationship between monarch butterfly larvae and Bt corn pollen:

* Dr. Dennis Calvin, Pennsylvania State University, (814) 863-4640

* Dr. Chris Difonzo, Field Crops Entomologist, Michigan State University (517) 353-5328

* Dr. Galen Dively, University of Maryland, (301) 405-3919

* Dr. John Foster, University of Nebraska, (402) 472-8686

* Dr. Rick Hellmich, Research Entomologist, USDA-ARS, Iowa State University, (515) 294-4509

* Dr. Michael Phillips, Executive Director, Food & Agriculture, Biotechnology Industry Organization (202) 857-2306

* Dr. John Pleasants, Iowa State University, (515) 294-7204

* Dr. Marlin Rice, Iowa State University, (515) 294-1101

* Dr. Mark Sears, University of Guelph, (519) 824-4120

* Dr. Warren Stevens, Missouri Botanical Garden, (314) 577-5103

Dr. Tom Turpin, Professor of Entomology, Purdue University (765) 494-4554