Pesticide Action Network Updates Service (PANUPS)
May 28, 1999
Entomologists at Cornell University in the U.S. have found significant adverse effects in monarch butterfly caterpillars that were fed pollen from genetically engineered corn. Since about half of the summer monarch population migrates through the U.S. Corn Belt, where millions of acres of genetically engineered insect-resistant Bt corn now grow, the monarch butterfly may be imperiled.
Pesticide Action Network North America is calling on groups and concerned individuals to write the U.S. Environmental Protection Agency and demand that the agency:
-- Deny any further approvals and renewals of Bt corn.
-- Immediately institute a moratorium on further planting of Bt crops until independent and comprehensive studies can be conducted on the short and long-term ecological effects of large scale release of organisms engineered to contain Bt toxins.
-- Convene a panel of respected independent ecologists, soil scientists, butterfly specialists and others to begin developing a program to detect and address ecological risks of engineered crops.
Bt corn produces a specific toxin, originally derived from a soil microorganism, Bacillus thuringiensis. In its natural form, the Bt toxin is activated when consumed by caterpillars of moths and butterflies and kills them. Several agrochemical companies including Monsanto and Novartis have engineered corn varieties to produce Bt toxin to kill insects that feed on corn plants.
In many Bt-corn varieties, the Bt toxin is produced in most of the plant's tissues, including its pollen. Toxic corn pollen is then blown by the wind onto milkweed and other plants in the vicinity of Bt-corn fields. The Cornell laboratory study, published this week in the journal Nature, found that monarch caterpillars eating Bt-corn pollen had significantly higher death rates and stunted growth compared with those eating normal pollen. Nearly half the caterpillars that consumed the toxic pollen died after four days; none of those eating normal pollen died.
In one field study, Iowa State University scientists have confirmed the toxicity of Bt corn pollen to monarch caterpillars. Nearly 20% of the caterpillars fed milkweed leaves taken from Bt corn fields and adjacent areas died, compared to no deaths of those exposed to normal corn pollen. In addition to monarchs, some of the 19 species of butterflies and moths on the U.S. Endangered Species List may also be at risk from the toxic pollen if they eat plants near Bt-corn fields.
Monsanto has stated that an important advantage of the crop is reduction or elimination of spraying of broad-spectrum insecticides to control the European corn borer. However, according to the Union of Concerned Scientists and other experts, based on figures from the National Agricultural Statistics Service, U.S. field corn is not often sprayed for European corn borer or any other insect, especially in the heart of the cornbelt. Therefore, little if any reduction in insecticide use can be expected as a result of planting Bt-corn.
The Cornell study is not the only one to suggest that Bt crops are far from benign. Swiss scientists last year showed detrimental effects on beneficial insects that ate corn pests that had been fed Bt corn. Other scientists have shown that Bt toxins accumulate in the soil and may adversely affect soil ecosystems. And there is near universal scientific consensus that widespread use of Bt corn and other Bt crops will accelerate the evolution of resistance to Bt toxins in insect pests. Once pests are resistant to Bt, organic growers and everyone else who relies on Bt to control pests will lose an effective, natural biocontrol agent.
PANNA urges all those concerned to write Carol Browner, U.S. EPA Administrator, and demand that EPA deny any further approvals and renewals of Bt corn and institute a moratorium on further planting of Bt crops until independent and comprehensive studies can be conducted on the short and long-term ecological effects of large scale release of organisms engineered to contain Bt toxins. Send letters to:
Carol Browner, U.S. EPA Administrator
Sources: Union of Concerned Scientists press release, May 20, 1999; UCS Fact Sheet: Monarch Butterflies, Bt Corn and Toxic Pollen, May 19, 1999; Monsanto Statement on Bt Corn: Environment and a Recent Report on the Monarch Butterfly, May 20, 1999; L. Hansen and J. Obrycki, "Non-target effects of Bt corn pollen on the Monarch butterfly (Lepidoptera: Danaidae)," abstract of a poster presented at the North Central Branch meeting of the Entomological Society of America, March 29, 1999, available at http:// www.ent.iastate.edu/entsoc/ncb99/prog/abs/d81.html