And now:Ish <[EMAIL PROTECTED]> writes:
Bt-Corn Pollen Deadly to Monarch Butterflies
http://ens.lycos.com/ens/may99/1999L-05-19-04.html
ITHACA, New York, May 19, 1999 (ENS) - An increasingly
popular genetically
engineered commercial corn has pollen which kills monarch
butterfly larvae in
laboratory tests, Cornell University researchers report. The
corn produces a
bacterial toxin to protect against corn pests.
Writing in the May 20 of the journal "Nature," the
researchers note that this
hybrid crop, known as Bt-corn, has genes from the bacterium
Bacillus
thuringiensis (Bt) spliced into the plant genes. This new
gene produces a protein
which kills insects after the protein is ingested.
These hybrids are very effective against the ravenous
European corn borer, a
major corn pest that is destroyed by the plant's toxic tissue.
Unlike many pesticides, Bt-corn has been shown to be
generally safe for human
consumption, although some critics of biotechnology
disagree. It has not been
shown to have any harmful effect on many non-target
organisms - such as
pollinating honeybees or beneficial predators such as ladybugs.
But the Bt-modified corn produces pollen containing
crystalline endotoxin from
the bacterium genes. This corn pollen is dispersed by the
wind around cornfields.
It lands on other plants, including milkweed which is the
exclusive food of
monarch caterpillars.
Like all grasses, corn is wind-pollinated, and the pollen
can be blown more than
60 yards from the edge of cornfields. "Pollen is that yellow
dusting your car gets
on spring and summer days; pollen is everywhere," says John
Losey, Cornell
assistant professor of entomology and the primary
investigator on the study.
"That's why we are concerned about this problem."
Monarch caterpillars on a milkweed leaf dusted
with pollen. (Photo by Photo by Kent
Loeffler courtesy
Cornell)
"Monarchs are considered to be a flagship
species for
conservation. This is a warning bell," says
co-researcher Linda Rayor. "Monarchs themselves
are not an endangered species right now, but
as their
habitat is disrupted or destroyed, their
migratory
phenomena is becoming endangered."
In the laboratory tests, monarchs fed milkweed
leaves dusted with so-called transformed
pollen from
a Bt-corn hybrid ate less, grew more slowly and
suffered a higher mortality rate. Nearly
half of these
larvae died, while all of the monarch
caterpillars fed
leaves dusted with the non-transformed corn
pollen
survived.
The toxin in the transformed pollen, the researchers say,
goes into the gut of the
caterpillar, where it binds to specific sites. When the
toxin binds, the gut wall
changes from a protective layer to an open sieve so that
pathogens usually kept
within the gut and excreted are released into the insect's
body. As a result, the
monarch caterpillar quickly sickens and dies.
Before the advent of Bt-corn, the European corn borer was
extremely difficult to
control because it bores into the stalk, where it is
protected from pesticides. It
produces several generations a year. Because it was so
difficult to control
effectively with pesticides, annual losses averaged $1.2
billion. In contrast,
Bt-corn provides essentially total season-long control at a
reasonable cost without
the use of pesticides.
At least 18 different Bt-engineered crops have been approved
for field testing in
the United States. As of last year, transformed corn,
potatoes and cotton had been
approved by the U.S. Department of Agriculture for
commercial use.
Several factors make monarch caterpillars particularly
likely to make contact with
corn pollen, Losey says. Monarch larvae feed exclusively on
milkweed because it
provides protection against predators. The plant contains
cardenolides, which are
toxic, bitter chemicals that the monarch caterpillar
incorporates into its body
tissues, rendering it unpalatable to predators.
Monarch caterpillars are feeding on milkweed during the
period when corn is
shedding pollen, Losey says. "They may be in the right place
at the right time to
be exposed to Bt-corn pollen."
Says Losey, "We need to look at the big picture here. Pollen
from Bt-corn could
represent a serious risk to populations of monarchs and
other butterflies, but we
can't predict how serious the risk is until we have a lot
more data. And we can't
forget that Bt-corn and other transgenic crops have a huge
potential for reducing
pesticide use and increasing yields. This study is just the
first step, we need to do
more research and then objectively weigh the risks versus
the benefits of this new
technology."
With approval from the European Commission, Ciba Seeds has
been marketing its
genetically modified Bt corn to the 15 member countries of
the European Union
since 1997.
The European Union's Scientific Committee on Food, the
Scientific Committee on
Animal Nutrition and the Scientific Committee for Pesticides
concluded, "There is
no reason to believe that the genetic modification of the
Bt-maize will give rise to
adverse effects on human health from its use in human food."
"There is no reason to believe that the genetic modification
of the Bt-maize will
give rise to adverse effects on animal health from its use
in animal feed."
"A potential development of insect resistance to the Bt
toxin cannot be considered
an adverse environmental effect, as existing agricultural
means of controlling such
resistant species of insects will still be available."
Reprinted under the fair use http://www4.law.cornell.edu/uscode/17/107.html
doctrine of international copyright law.
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Tsonkwadiyonrat (We are ONE Spirit)
Unenh onhwa' Awayaton
http://www.tdi.net/ishgooda/
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