BT Pollen not so Dangerous to Monarchs

Rcjohnsen rcjohnsen at
Mon Feb 14 18:31:35 EST 2000

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NEXT >Source:	 	University Of Guelph (
Contact:	 	Margaret Boyd , Research Communications Officer 
Phone: 519-824-4120, Ext. 2776; Email: margaret at
Date:	 	Posted 2/9/2000

New Research Suggests Bt-Corn Not Harmful To Monarch Butterfly 

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

Note: This story has been adapted from a news release issued by University Of
Guelph for journalists and other members of the public. If you wish to quote
from any part of this story, please credit University Of Guelph as the original
source. You may also wish to include the following link in any citation: 

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