Iowa University Professor Links Butterfly Mortality and
Bt Corn
COMTEX Newswire
Sep. 19 (The News-Gazette/KRTBN)--WASHINGTON, D.C.--John Obrycki's monarch
butterfly study started in the summer of 1998, independently of work at Cornell
University, which published the first report linking butterfly mortality and Bt
corn.
Obrycki, an Iowa State University entomologist, and his students focused on two
different genetic "transformations" of Bt corn, one of which expresses more
toxin in pollen than the other.
"The one with the higher concentration of toxin caused higher levels of
mortality, but we did see significant mortality with both," he said.
Obrycki exposed monarch larvae to either type of pollen in the laboratory, then
put them on fresh leaves for five days. He said mortality was 70 percent with
the more toxic pollen and 35 percent to 40 percent with the less toxic pollen.
Mortality for a control group of larvae not exposed to Bt corn pollen was zero,
he said.
"For the other part of the study, we put potted milkweeds in the field to allow
pollen to be naturally deposited, then we brought them into the lab and counted
pollen grains, to expose the larvae to known densities," Obrycki said.
"It was never designed to be a field study," he said. "In that test, we found
after two days, 20 percent of the larvae exposed to Bt pollen died. We also
placed leaves next to non-Bt corn plants, and there was no mortality."
He said the study was published online because that's the policy of the
publication, Oecologia, that accepted it.
"John Losey's paper was in Science," Obrycki said of the Cornell researcher
who's now his collaborator. "We tried to submit to Science and Nature, but
because you're second, you have to show something different, so we submitted to
Oecologia three months ago."
He's doing a true field study this year.
"Our graduate students set out Bt and non-Bt corn next to each other,
counted the milkweed plants and the number of monarchs laying eggs, trying to
compare difference in mortality," Obrycki said.
"In field situations, things get much more complex," he said. "Other things
affect the larvae."
By Anne Cook
-0-
To see more of The News-Gazette, or to subscribe to the newspaper, go
to http://www.news-gazette.com
(c) 2000, The News-Gazette, Champaign-Urbana, Ill. Distributed by
Knight Ridder/Tribune Business News.
Copyright 2000