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Approved-By:  John/Laurel Hopwood <[log in to unmask]>
Message-ID:  <l0313030fb39317a6670c@[198.234.69.171]>
Date:         Sun, 20 Jun 1999 18:13:31 -0400
Reply-To: Biotech Forum <[log in to unmask]>
Sender: Biotech Forum <[log in to unmask]>
From: John/Laurel Hopwood <[log in to unmask]>
Subject:      non-target effects of Bt corn on butterflies
To: [log in to unmask]
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Neil writes the following:

Milkweeds routinely grow right in corn fields; each plant is able to
produce several thousand seeds, each capable of growing in a corn field.
They also commonly populate the highly disturbed
areas right next to the corn field.  Milkweeds are one of the more common
weedy species occurring in the habitats around corn fields.
Milkweed plants do commonly grow within the corn fields since it's an
effective weedy species responding successfully in disturbed habitats like
a corn field, and so it's inaccurate to assume that the bulk of the Bt corn
pollen falling within the corn field will not land on milkweeds as the
study at Iowa State University recently discovered. Once again I think it
reveals that we need to
be cautious about making certain assumptions that are incorrect about the
safety of Bt crops and Bt pollen dispersal patterns.

The following abstract was presented 3/29/99 at the American Biological
Society meetings.

Abstract: Non-target effects of Bt corn pollen on the Monarch butterfly
(Lepidoptera: Danaidae)
* Laura Hansen, Iowa State University, Ames, IA and John Obrycki, Iowa State
University, Ames, IA 50011 Contact: e-mail: [log in to unmask]

Order: Lepidoptera
Family: Danaidae
Species: Danaus plexippus

Order: Asteridae
Family: Asclepiadaceae
Species: Asclepias syriaca
The expression and dispersal of Bt toxin in the pollen of transgenic crop
plants may pose a risk to non-target Lepidopterans. When Bt corn pollen lands
on the leaves of plants in and around corn fields, it exposes non-target
Lepidopteran larvae feeding on these plants to Bt toxins. In Iowa, where the
landscape is dominated by row-crop agriculture, areas effected could include a
significant portion of non-cultivated areas, including remnant prairies,
roadside ditches and wetlands.  The monarch, Danaus plexippus (Lepidoptera:
Danaidae) was chosen as the non-target Lepidopteran species for this study
because it is a common butterfly species that feeds on several species of
milkweed, Asclepias. Asclepias syriaca (Asclepiadaceae) commonly grows in road
ditches, grassy areas between fields, and within corn fields, so it is likely
to have Bt corn pollen desposited upon it. The first step of this study was to
determine the amount of corn pollen deposited on A. syriaca leaves within and
adjacent to a Bt corn field at 0m [meters], 1m [meters], and 3m [meters]. The
highest levels of pollen deposition was found on plants within the corn field,
and lowest levels found at three meters from the edge of the corn field. Leaf
samples taken from within and at the edge of the corn field were used to assess
the mortality of the first instar monarch, D. plexippus exposed Bt and non-Bt
corn pollen. Within 48 hours, there was 19% mortality in the Bt corn pollen
treatment compared to 0% on non-Bt corn pollen exposed plants and 3% in the no
pollen controls.
http://www.ent.iastate.edu/entsoc/ncb99/prog/abs/d81.html

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