BT Pollen not so Dangerous to Monarchs

Robin Baker robinb at
Thu Feb 17 17:05:41 EST 2000

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<p>Susan Courson wrote:
<blockquote TYPE=CITE>Thank you for this post.&nbsp; I have been searching
for information on this issue.&nbsp; We
<br>are writing a series of lessons to be used in a biotechnology workshop
this summer
<br>for secondary science teachers.
<p>Rcjohnsen wrote:
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Posted 2/9/2000
<br>> New Research Suggests Bt-Corn Not Harmful To Monarch Butterfly
<br>>&nbsp;&nbsp;&nbsp; The Monarch butterfly is alive and well, despite
exaggerated and misleading
<br>> reports that biotechnology is threatening it, says a University of
<br>> researcher.
<br>> Field research conducted by Prof. Mark Sears, chair of the University
<br>> Guelph's Department of Environmental Biology and chair of the Canadian
<br>> Pest Coalition, shows pollen from Bt corn -- Bacillus thuringiensis,
<br>> naturally-occurring soil-borne bacterium which selectively targets
<br>> groups of insects -- is not found in high enough doses on most milkweed
<br>> (the food plant of the caterpillars) to hurt Monarch butterfly larvae.
<br>>&nbsp;&nbsp;&nbsp; Although Bt is harmless to humans and other animals,
a U.S. study claimed
<br>> pollen from Bt-corn damaged Monarch butterfly larvae. The study sparked
a media
<br>> frenzy and public concern about genetically modified foods.
<br>> Sears says the U.S. study didn't demonstrate to what extent its preliminary
<br>> findings applied to field situations. The study was completed in
a lab, and the
<br>> dosage of pollen used wasn't reported.
<br>>&nbsp;&nbsp;&nbsp; "The actual threat to the Monarch butterfly can
only be determined by
<br>> assessing the dosage that affects the larvae and their degree of
exposure to
<br>> Bt-corn pollen in the field," says Sears.
<br>>&nbsp;&nbsp;&nbsp; Sears is leading a two-year project to determine
the ecological impacts of
<br>> Bt-corn pollen on selected non-target butterfly species, including
the Monarch.
<br>> So far, studies indicate that Bt- corn is not as big a threat as
<br>> environmentalists and the news media had anticipated.
<br>>&nbsp;&nbsp;&nbsp; "Outside of corn fields, you probably wouldn't
find concentrated dosages of
<br>> pollen because wind and rain removes it from the surface of the milkweed
<br>> leaves," says Sears. Sears's study focused on Bt pollen and how far
it travels.
<br>> He examined milkweed stands in corn fields, at their edges, then
at distances
<br>> of five, 10 , 25, 50 and 100 metres away. He found that within the
<br>> approximately 150 pollen grains/cm2 were found on milkweed leaves.
At the field
<br>> edges, 80 to 100 grains/cm2 were found, and at five metres, only
one grain/cm2
<br>> was found. He then compared these findings to values obtained from
<br>> "dose-response assay" — from which data of increasing doses are plotted
<br>> increased mortality rates — to determine dosages with negative effects
<br>> Monarch butterfly larvae.
<br>> Results show that 135 grains/cm2 — the lowest dosage he has tested
on milkweed
<br>> leaves so far and similar to that found on milkweed leaves in the
field — had
<br>> no greater effect on Monarch larvae than when they were fed non-Bt
<br>>&nbsp;&nbsp;&nbsp; "Our findings are consistent with other studies
across North America," says
<br>> Sears. "Bt- corn has always shown to be harmless to both humans and
<br>> and we now know it isn't a major threat to the Monarch butterfly."
<br>>&nbsp;&nbsp;&nbsp; Sears is being assisted by research associate Diane
Stanley-Horn and
<br>> research technician Heather Mattila from the University of Guelph,
along with
<br>> seed industry representatives and corn growers. His research is sponsored
<br>> the Canadian Food Inspection Agency and Environment Canada.
<br>> ------------------------------------------------------------------------
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<br>> Guelph for journalists and other members of the public. If you wish
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<p>Robert A. Baker
<br>Oregon City, OR, USA

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