DAVID HO, Associated Press Writer
WASHINGTON (AP) - Genetically engineered corn designed to kill
an insect pest spreads enough of its pollen on nearby weeds to
kill monarch butterflies, researchers said Monday in the latest
study on the biotech crop's environmental effects.
Iowa State University scientists found that one in five monarch
larvae died after being exposed to the toxic corn pollen for two
days. Three days after the initial two-day exposure more than half
of the larvae died.
"In the field you may have higher mortality rates because
of the cumulative effect of being exposed to the toxin throughout
the larval stage," said researcher John Obrycki, whose study
appears in the Internet edition of the journal Oecologia.
"Coming up with a good ecological assessment of this
technology probably needed to be done before planting it across
The biotech corn, known as Bt corn for a bacterium gene that
makes it toxic to the European corn borer, became controversial
last year after a laboratory study at Cornell University showed it
was toxic to monarch butterflies.
The corn's pollen coats the leaves of nearby milkweed plants
that butterfly caterpillars eat.
The Cornell finding produced a public outcry in Europe and
calls from environmental groups to curb the spread of gene-altered
crops, but biotech supporters have criticized that study and the
one from Iowa State for being unrealistic.
"Much of what (the Iowa State study) reports is based on
analyses taking place in laboratory manipulations rather than
field conditions," said Val Giddings, vice president of food
and agriculture for the Biotechnology Industry Organization.
The Iowa State researchers planted breeds of biotech corn that
produced different levels of the insecticide pollen along with
some corn that hadn't been engineered. They then placed potted
milkweed plants at varying distances from the fields. After two or
three days they took the milkweed plants into the lab and exposed
the butterflies to the plant leaves.
Significant numbers of butterflies died after exposure to
leaves coated with pollen, while those placed with leaves that
were washed or unexposed to the Bt pollen died at a normal rate.
Giddings said butterfly caterpillars are unlikely to encounter
the pollen in nature in any great numbers and that the monarch
butterfly population increased almost as much as the plantings of
Bt corn last year.
An estimated 19 percent of the 80 million acres of corn growing
this year was Bt.
Environmental groups have petitioned the Environmental
Protection Agency to have farmers surround fields of Bt corn with
buffer zones of conventional corn to prevent the pollen from
spreading to milkweed.
"Continued inaction would clearly be lethal to monarch
butterflies," said Rebecca Goldburg, a scientist at
Environmental Defense, a group critical of genetically engineered
The EPA has been reviewing its standard for biotech crops and
plans to release recommendations in September, said Steve Johnson,
deputy assistant administrator of the office of prevention,
pesticides and toxic substances.
Early this year the EPA put new planting restrictions on Bt
corn to prevent insects from developing resistance to the toxin.
The restrictions require farmers to plant at least 20 percent
conventional corn in most regions, and 50 percent in areas where
cotton is grown.
In June, University of Illinois scientists placed black
swallowtail butterflies near a farmer's field and found no
evidence that they were harmed by the biotech corn. The
swallowtail is considered less sensitive to the corn toxin than
the monarch, but is more likely to be exposed to the pollen.
On the Net:
Environmental Protection Agency: http://www.epa.gov
USDA's biotechnology site:
Biotechnology Industry Organization: http://www.bio.org
Environmental Defense: http://www.environmentaldefense.org