Does Bt Corn threaten any Rare Prairie Skippers

John Shuey jshuey at
Thu Aug 24 17:52:27 EDT 2000

cherubini at wrote:

> John Shuey wrote:
> > I can give you numerous examples of regionally imperiled skippers and
> > butterflies and moths that are limited to small prairie/savanna remnants that
> > are completely or largely surrounded by corn alternated with beans in
> > Indiana.  All you have to keep  in mind is that 99.9% of mesic tallgrass
> > prairie has been converted to row crop agriculture - the math gives you 0.1%
> > original prairie imbedded in agriculture.  In most cases, rowcrop fields abut
> > prairie remnants.
> > And on and on...  These species are all thought to occur at 10 or fewer sites
> > in the state, and are certainly in danger of local extirpation.  Whether or
> > not Bt corn impacts these species or not - who knows - because no one has ever
> > investigated the issue.  The potential for negative impact to these is
> > certainly present for those populations restricted to particularly small
> > grassland remnants
> John, do the larval food plants of any these "imperiled", "threatened" "rare"
> "endangered" leps in Indiana  grow within corn fields or within
> a few yards of the edge of corn fields?

You bet they they do.  (I don't know how much more clearer I could have said this in the
original post which I'll paraphrase in small words here). In most cases, row crop abuts
directly against remnant prairie and savanna (oops - I hit three syllables with this
word) - especially savanna (oops - sorry again).  Drift from corn pollen is a reality in
the edges of  many of these areas.  Any species using common grasses as hosts (like
Hesperia and Problema) or common violets (like Speyeria) are likely to oviposit on host
plants dusted by pollen along these edges.  To paraphrase myself again in small words,
this dusting by Bt pollen of butterfly hostplants along prairie edges produces the
POTENTIAL for negative impacts to these butterflies. (This is called deductive reasoning)

>  If not, the larvae of these species will not
> be exposed to harmful amounts of Bt corn pollen.  By contrast, when conventional
> broad spectrum insecticides or liquid formulations of Bt are aerially applied
> to corn, the potential for spray drift on adjacent prairie remnants is
> obviously be greater (and even this is apparently not a problem because as you
> pointed out there are some "regionally imperiled" species that exist on prairie
> remnants surrounded by corn)

The term "regionally imperiled" implies that most of the populations in an area have
become locally extinct, leading one to believe that surviving populations are at risk as
well (for example, there are over 40 mesic prairie remnants in Indiana, and only one
population of Speyeria idaila - which persists on a smallish remnant at that). Well over
200 oak savanna remnants persist, yet we feel that most of the Hesperia are limited to a
small fraction of these. Simply because a population of a species persists to the present
day, does not imply that the population is viable for the long-term.  Rather, the only
fact you can glean from a 40 acre habitat supporting a wide-ranging species like S.
idalia, is that this particular population hasn't yet become extinct (while other similar
populations have become extinct in the last few years).

And keep in mind that I never said that Bt corn is worse than other forms of agriculture
(again I'm sorry that I didn't explicitly say this so that argumentative types couldn't
attempt to put words in my mouth).  I have no doubt that aerial drift from traditional
pesticide applications has the potential to negatively impact these species as well.  In
fact, one of the key strategies for prairie conservation is simply removing row crop
agriculture from adjacent fields (both to remove external threats to remnant integrity as
well as to expand available habitat over time).

(sorry about the tone of this post, but I'm tired of compulsive apologists)

John Shuey

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