Genmod Crop
Residues
posted
by Mark Graffis, 18 Mar 2001
An independent science advisory panel told the Environmental Protection Agency more studies are needed to pinpoint how long bioengineered cotton and corn residue lingers in the soil and whether it poses any environmental risk.
The EPA asked for the guidance as it considers whether to renew the registration of Bt corn, cotton and potato varieties that were approved six years ago.
Bt crops are engineered to include the bacillus thuringiensis bacterium, which occurs naturally in soil and acts as a pesticide. The EPA will publish its proposed decision on Bt crop re-registration applications for public comment later this year.
The science panel, led by Stephen Roberts of the University of Florida, said more data was needed to determine how much of the unique Cry proteins from Bt crops remain in the soil after harvest, and whether they are harmful.
“These studies are important to assess long-term environmental effects of Bt-containing crops,” the report said. “It would be prudent to determine under operational field conditions in different geographical regions and soil types, the extent to which Cry proteins accumulate in soil,” it added.
Some laboratory studies have shown Cry proteins can linger in soil microcosms for as long as 234 days. The panel of scientists also said more information was needed to evaluate if Monarch butterflies are adversely affected by Bt corn. The panel said it was “divided” over the EPA’s decision last autumn to disregard an Iowa State University laboratory study that found Monarch caterpillars were seven times more likely to die when they ate milkweed plants dusted with pollen from Bt corn.
The EPA rejected the study findings, saying it did not fairly represent actual field conditions. The panel’s report suggested that the EPA launch studies to assess Monarch butterfly deaths at different times during the growing season and at different life cycle stages, and to identify any other kinds of butterflies that may be at risk from Bt corn pollen. More data is also needed to assess whether farmers using Bt crops are using fewer pesticides, the scientists said.
A copy of the report was posted on the EPA's Internet site at octoberfinal.pdf. REUTERS NEWS SERVICE