Nuovo studio: Monarca non minacciata

["AlessandroGimona"<agimona@libero.it>]

Cari tutti,

Un nuovo studio scientifico ha concluso che, in condizioni di campo, il 
rischio posto da polline di mais GM per le larve della farfalla Monarca 
e ' trascurabile.

Saluti,
Alessandro Gimona

archived at:
http://www.plant.uoguelph.ca/safefood/archives/agnet-archives.htm


BUTTERFLIES NOT THREATENED BY MODIFIED CORN, STUDIES SAY
September 10, 2001
Globe and Mail/Broadcast News
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According to these stories, recent studies by U.S. and Canadian 
scientists
contradict earlier suggestions that monarch butterflies could be 
threatened
by genetically modified corn.
The reassuring papers are being rushed into publication this week, 
before
biotechnology companies are required to submit their corn-modifying 
products
for
review by the U.S. Environmental Protection Agency at the end of 
September.
Mark Sears, chairman of the University of Guelph's department of
environmental biology, which has been working in conjunction with some 
U.S.
universities, was quoted as saying that, "After two years of study, 
we've
found it's a negligible risk," adding that
the risk to monarch butterflies is especially low because the insects 
feed
on milkweed plants that are only occasionally dusted with corn pollens,
which carry minute quantities of the toxin.
Sears was further quoted as saying, "The low toxicity in pollen grains 
of
just about all our commercial hybrids and the fact that less than 10 per
cent of butterflies spend time around Bt corn are the two features that
drive the risk down."
In another study, Arthur Zangerl, a senior research scientist at the
University of Illinois, was cited as saying his team's findings were 
similar
to the Canadian results, adding, "It [modified corn] poses very little 
risk.
We were unable to find any kind of effect for most strains."
However, Mr. Zangerl's researchers discovered that black-swallowtail 
larvae
growth can be stunted by pollen from one of the oldest varieties of
genetically modified corn, Bt 176.
"These results suggest that Bt corn incorporating event 176 can have 
adverse
sublethal effects on black swallowtails in the field," stated a draft 
of the
report.
But Mr. Sears was cited as saying that variant Bt 176 is unpopular -- 
it's
used in only about 2 per cent of genetically modified corn fields -- 
and is
unlikely to be submitted this year for reapproval by the EPA.
In general, the toxin produced by modified corn is harmless to animals,
including humans, Mr. Sears said. It dissolves the stomach lining of 
some
insects, including
those that ingest pollen. But about 95 per cent of a corn field's pollen
falls within
five metres of the field's edges, and rarely accumulates in enough
concentration to
threaten insects.
"The most we observed was 170 pollen grains per square inch," he 
said. "But
to have a statistically significant effect on larvae you'd need at least
1,000 grains per square inch."
Farmers choose genetically modified corn because it protects against the
European corn borer, a pest introduced to North America in the late 
1700s.
If left untreated, the parasite burrows into the stalk or ear of the 
corn,
causing fungus infestations. Alternative treatments such as spraying are
more dangerous to the environment, Mr. Sears said.




Alessandro Gimona
agimona@libero.it