This was forwarded to me by Ericka Dana.
Tom Mathews
Date: Wed, 04 Oct 2000
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P A N U P S <[log in to unmask]>
Pesticide Action Network Updates Service
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Bt-Corn Pollen from Iowa Fields Kills Monarch Caterpillars
October 10, 2000
In August, Iowa State University scientists reported in the journal
Oecologia that one kind of Bt-corn pollen naturally deposited on milkweeds
in and near corn fields kills monarch butterfly caterpillars. This research
confirms a laboratory study published in Nature last summer which showed
that Bt-corn pollen is lethal to monarchs.
The Iowa scientists conducted three kinds of studies using two types of Bt
corn marketed by Novartis Seeds: KnockOut, which contains a Bt gene named
Event 176 and YieldGard with a Bt gene called Bt 11. KnockOut pollen
typically contains more Bt toxin than YieldGard pollen. The three
experiments were:
* To learn how much pollen caterpillars might be exposed to under field
conditions, researchers counted pollen that fell on milkweeds, the favorite
food of monarch caterpillars, within and near KnockOut, YieldGard and
nonBt-corn plots.
* To assess mortality of caterpillars exposed to natural, field-deposited
pollen, researchers placed caterpillars on pieces of leaves taken from
within and at the edges of plots of KnockOut and nonBt-corn and counted the
number of dead larvae after two days' feeding.
* To determine the impacts of a range of Bt-pollen densities likely to be
encountered in the field, the scientists conducted a laboratory study
exposing larvae on pieces of leaves to three levels of KnockOut, YieldGard
and nonBt pollen. They counted dead caterpillars and monitored the survivors
until they emerged into butterflies, looking for side effects like slowed
development time and smaller butterfly bodies.
In the first study, the scientists found that milkweed plants placed in and
near both KnockOut and YieldGard corn fields received amounts of Bt pollen
that could kill monarch caterpillars. The second experiment revealed that
significantly more caterpillars died after feeding for two days on pieces of
leaves taken from KnockOut corn fields compared with leaves taken from nonBt
fields and leaves with no pollen. In the laboratory study of different
pollen densities, caterpillar mortality was significantly greater on the two
highest densities of both KnockOut and YieldGard pollen than on nonBt
pollen. At the lowest density, larvae survived equally well on Bt and nonBt
pollen. Caterpillars that survived exposure to Bt and nonBt pollen appeared
to develop similarly into adult butterflies.
The authors suggest that the effects of Bt-corn pollen on monarchs will be
greatest where most of the pollen falls--inside Bt-corn fields or within
three meters of the edges. Milkweeds are found both within and along the
margins of corn fields.
This report follows on the heels of a University of Illinois study published
in the Proceedings of the National Academy of Sciences this summer which
suggested that another kind of Bt-corn pollen, Monsanto's Bt corn (Mon 810
gene), was not lethal to swallowtail butterflies under field conditions in
Illinois.
What does the Iowa study mean?
This field study does not resolve whether or not Bt corn will be a serious
threat to monarch butterflies in corn-growing areas. Much more research
needs to be done. But it does mean that the U.S. Environmental Protection
Agency (EPA) was remiss in approving Bt corn for commercial use five years
ago before fully assessing environmental risks.
EPA is presently engaged in a comprehensive review of all Bt corn and cotton
with the aim of deciding within the next year whether and under what
conditions Bt crop registrations should be renewed. Current registrations
for Bt corn and cotton expire in 2001.
The Union of Concerned Scientists is urging EPA not to reregister any Bt
corn until it has a program in place to thoroughly assess ecological risks
of Bt crops, including the risk to monarchs and other beneficial insects. In
addition, EPA should require farmers to plant buffers of nonBt-corn around
Bt fields in the coming year to reduce the amount of toxic pollen blowing
beyond transgenic fields.
Sources: Laura C. Hansen Jesse, John J. Obrycki. 2000. Field deposition of
Bt transgenic corn pollen: lethal effects on the monarch butterfly.
Oecologia, DOI 10.1007/s004420000502, published online: 19 August 2000.
C.L. Wraight, A.R. Zangerl, M.J. Carroll, and M.R. Berenbaum. 2000. Absence
of toxicity of Bt pollen to black swallowtails under field conditions.
Proceedings National Academy of Sciences USA, published at PNAS Online June
2000.
Contact: Union of Concerned Scientists. 1707 H Street NW, Suite 600,
Washington DC 20006-3919; phone 202-223-6133; fax 202-223-6162;
http://www.ucsusa.org/agriculture/index.html
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From: PANUPS <[log in to unmask]>
Reply-To: [log in to unmask]
Date: Wed, 04 Oct 2000 16:39:05 -0700
To: PANUPS <[log in to unmask]>
Subject: PANUPS: Bt-Corn Pollen from Iowa Fields Kills Monarch Caterpillars
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