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Sunday, November 22, 2009 |
Academic Researchers and Industry Agree Reports on Bt Crop Impact on Monarch Butterflies Overblown
Monarch Butterfly Researchers Urge Caution in Over-Interpreting Results
Contact:
Libby Mikesell
(202) 857-0244
WASHINGTON D.C. (June 21, 1999) - Several academic experts have urged caution when interpreting the results of a preliminary laboratory study at Cornell University on the effect of Bt corn pollen on the Monarch butterfly that was published as a letter in the journal Nature (5/20/99). These university researchers stressed that the monarch study did not represent natural conditions and that extensive environmental research has confirmed the safety of Bt corn on non-target insects, such as the ladybird beetle, honeybee and the green lacewing, in the natural environment.
Dr. John Losey, the Cornell University entomology professor who conducted the research said, "Our study was conducted in the laboratory and, while it raises an important issue, it would be inappropriate to draw any conclusions about the risk to monarch populations in the field based solely on these initial results."
In a response letter published in Nature (6/3/99), Dr. John Beringer, professor at the University of Bristol's School of Biological Science in the United Kingdom and chairman of the U.K. Advisory Committee on Releases to the Environment, wrote, "There is a need for scientific rigour in the presentation of the information to ensure that it is not misrepresented. . . . preliminary observations should not be over-interpreted."
"We want to make sure that the monarch is protected, and we want to verify the belief of numerous scientists that Bt pollen is not putting the monarchs at significant risk," said Dr. L. Val Giddings, vice president for food and agriculture, Biotechnology Industry Organization (BIO).
Factors in field reduce likelihood of monarch exposure to corn pollen
By design, the Cornell researchers did not match the conditions that would be present in a natural setting. In the laboratory, the caterpillars were given no choice but to feed on one treatment, in this case leaves dusted with corn pollen. In the field, the caterpillars may move about and may avoid ingesting pollen.
Under natural conditions, monarch larvae feed primarily on milkweed. Most researchers consider it likely that most milkweed does not grow close enough to corn fields to be exposed to significant amounts of corn pollen.
Further, the majority of monarch larvae feed on milkweed when corn pollen is not present. Corn plants produce or "shed" pollen for a short period of time (typically most pollen is produced in a given field over a five to 10 day period.) Based on known migration behavior, even in those regions in which corn and monarchs co-habitate, only a small portion of the monarch population will be present when corn is shedding pollen.
Even if exposed to corn pollen, monarch caterpillars should have no trouble avoiding small amounts of windblown pollen and most likely would do so, as the Nature study suggests. Milkweed has many large leaves, and it tends to grow in clumps. If upper leaves were coated with pollen, the caterpillars would most likely move to lower, protected leaves or to another plant, according to Dr. Warren Stevens, senior curator of the Missouri Botanical Garden.
As Stevens wrote in the Des Moines Register, "Timing is all-important. For any harm to occur, the monarch larvae have to be emerging and feeding at the same time corn is pollinating, a narrow period of seven to 10 days. Pollen has to be on a particular leaf that the caterpillar is feeding on. And the caterpillar has to consume the pollen before rain or dew washes it away. The caterpillar also has to keep eating, not spit it out and move to another leaf, as the Cornell study suggests will happen in nature."
For these reasons, it is likely that the vast majority of monarch larvae throughout their range over a growing season are never exposed to corn pollen in nature at all.
Bt Corn Benefits Non-target Insects
The Bt corn crops that are currently on the market were developed to control the European Corn Borer. Prior to the introduction of Bt corn, farmers controlled European Corn Borer with conventional insecticide sprays that are toxic to monarch butterfly larvae and other desirable, non-target species. By reducing the use of these insecticides, Bt corn reduces the potential to harm non-target species, and reduces impacts of agricultural inputs on the environment in general.
"I still think the proven benefits of Bt corn outweigh the potential risks," stated Dr. Losey. "We can't forget that Bt corn and other transgenic crops have a huge potential for reducing pesticide use and increasing yields."
Dr. Chris DiFonzo, Michigan State University Field Crops Entomologist & Pesticide Education Coordinator, said "Bt corn is a much safer method of pest management, and has less detrimental impact on all aspects of the environment -- monarchs included -- than the use of broad-spectrum insecticides."
"When you consider the monarch butterflies in context with the widely recognized benefits of Bt crops, it's clear that trends in agriculture will only help
the monarchs and the environment overall," said BIO's Val Giddings. "For example, Bt crops preserve beneficial insects that prey on harmful insect pests, thus limiting the need for additional insecticide sprays. Growers planting Bt crops have dramatically reduced the damage done by harmful pests and have reduced handling and exposure of insecticides on the farm."
"As conservation groups have noted, the primary threat to the monarch butterfly is the loss of crucial winter habitat in southern California and central Mexico," Giddings added. "Other threats come from habitat degradation along butterfly migratory routes, pesticides, and other human activities. It's not an exaggeration to say more monarchs succumb to high-velocity collisions with car windshields than ever encounter corn pollen."
In addition to the extensive number of field studies that have been conducted to determine the effect of Bt crops on beneficial insects, BIO and the
American Crop Protection Association are working along with industry partners to address and evaluate these issues further. The available information strongly supports the advantages of Bt crops on beneficial insect population relative to the use of insecticides.
For further information on this subject, contact the following independent experts:
Warren Stevens, Ph.D.
Missouri Botanical Garden
4344 Shaw Blvd, St Louis, MO 63110-2291
(314) 577-5103
Albert Tenuta, Ph.D.
Pest Management Specialist and Plant Pathologist
Ontario Ministry of Agriculture, Food, and Rural Affairs
University of Guelph
Ridgetown, Ontario
(519) 674-1617
John Foster, Ph.D.
Professor of Entomology
University of Nebraska
Lincoln, NE
(402) 472-8686
Marlin Rice, Ph.D.
Professor of Entomology
Iowa State University
Ames, IA
(515) 294-1101
John Wedberg, Ph.D.
Professor of Entomology
Dept of Entomology
University of Wisconsin
Madison, WI
(608) 262-1696
Chris DiFonzo, Ph.D.
Field Crops Entomologist
(517) 353-5328
Pat Bolin, Ph.D.
(517) 353-3274
Vegetable Integrator, IPM Program
Michigan State University, Extension Service
Galen Dively, Ph.D.
Professor of Entomology
University of Maryland
4112 Plant Science Building
College Park, MD 20742
(301) 405-3913
John Losey, Ph.D.
Asst. Professor of Entomology
Cornell University
(607) 255-7376
Riley Foster, Ph.D.
Plant Pesticide Specialist
University of Illinois
(217) 367-5303
Department of Crop Science
University of Illinois
Urbana, IL
(217) 333-6652
Web site: www.ag.uiuc.edu/cespubs/pest/
Sarah Hake, Ph.D.
Director, Plant Gene Expression Center
U.S. Department of Agriculture
Albany California
(510) 559-5907
Nina Fedoroff, Ph.D.
Willaman Professor of Life Sciences
University of Pennsylvania
(814) 863-4576
Terry Franel, Senior Economist
American Farm Bureau Federation
(202) 484-3600
Jeffrey Barach, Ph.D.,
Vice President, Special Projects
National Food Processors Association
(202) 639-5900
Dave Schmidt, Vice President, Food Safety
International Food Information Council
Washington, DC
(202) 296-6540
L. Val Giddings, Ph.D.,
Vice President, Food & Agriculture
Biotechnology Industry Organization
Washington, DC
(202) 857-0244
Allan Noe, Vice President
American Crop Protection Assn.
(202) 296-1585
National Corn Growers Association
St. Louis, MO
(314) 275-9915
URL: www.ipm.iastate.edu/ipm/icm/1999/6-14-1999/monarchbt.html
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