New Iowa State Study on Effects of Bt Corn Pollen on Monarch Larvae

[Anne Kilmer]

At last, some actual facts. 
Seems to me that, whatever they sprayed on that corn, it would make
things unpleasant for the monarchs and their relatives. Malathion?
Diazinon?
I find myself more concerned with the notion that the Bt pollen will
spread its genetic load to all the corn ... the cat, in other words,
would be out of the bag. 
Does corn pollen, I wonder, affect other grasses? After all, you can't
grow squashes and melons together, because the melons take on the flavor
of the squash. 
And I find myself suddenly in favor of the dreaded Terminator Gene, if
only it is possible to limit its effect to the plants modified to
receive it.  
(Background music ... The Sorcerer's Apprentice. Starring Mickey Mouse.)
The speckled wood has staked out the front garden, where there is only
enough sunlight for himself ... none for the green-veined white. 
Woody lays his wings together and turns edge-on as  I approach, thus
vanishing.  Formidable, I am. 
And yet the rain marches down the mountain, disregarding my plans for
the day. 
Enjoy your butterflies
Anne Kilmer
Mayo
Ireland
Paul Cherubini wrote:
> 
> The following abstract of an Iowa State Study was copied from the
> website of the North Central Branch of the Entomological Society of
> America. It appears to be a better study than the Cornell one as it
> measured pollen deposited on milkweed growing within a corn field and up
> to 3 meters away from the edge of the corn field under real world
> conditions. Exactly how the researchers experimentally manipulated the
> larvae and arrived at their 19% mortality figure (including 3% mortality
> in a no pollen control group) is unclear at this point.
> 
> May 25, 1999 - Data from Iowa State University Department of Entomology
> shows a relationship between the mortality of first instars (larvae) of
> the monarch butterfly (Lepidoptera: Danaidae) under field conditions
> with Bt corn.
> 
> Non-target effects of Bt corn pollen on the Monarch butterfly
> (Lepidoptera: Danaidae)
> 
> L. Hansen, Iowa State University, Ames , IA 50011 and J. Obrycki, Iowa
> State University, Ames, IA 50011 Contact e-mail: lrahnsen at iastate.edu
> 
> The expression and dispersal of Bt toxin in the pollen from 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 deposited 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
> 0 m, 1m, and 3m.
> 
> The highest levels of pollen deposition was found on plants within the
> cornfield, 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 mortality of 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.
> 
> MONSANTO May 20 Press Release:
> 
> The exposure of milkweed to corn pollen is very low because only a very
> small portion of milkweed grows in close enough proximity to corn fields
> for exposure to corn pollen. This information supports the conclusion of
> a very low likelihood of effect of Bt pollen on non-target insects like
> the Monarch butterfly in their natural habitats.
> 
> PIONEER HI-BRED Seed CompanyMay 24 Web Site Statement:
> 
> We have no proof that pollen containing Bt has a negative effect on
> monarch populations in a natural environment. A major question is
> whether or not monarch larvae eat pollen on milkweed plants in the
> natural environment.  Contact between Bt pollen and milkweed depends on
> where the milkweed is in relation to the corn field. Wind and rain can
> obviously impact pollen on milkweed.