Losey (and colleagues) data??

[Martha Rosett Lutz]

I received the following post to the list:

"When John Losey and colleagues in Cornell University published their findings
that Bt-corn pollen harmed monarch butterflies, the concern raised was not
just over monarch butterflies, but on all other (non-target) species in the
environment."

I acknowledge the broader context, and do not wish to diminish that aspect,
but would like to comment specifically on the Losey et al. paper in Nature.

Please, correct me if I am somehow mistaken, but their actual data (as
published in Nature) did not establish that Bt-corn pollen harms Monarchs.
They failed to distinguish between antibiosis and antixenosis, and the data
which had statistical significance showed that both Bt and non-Bt corn
pollen resulted in significantly decreased feeding by Monarch larvae.
Their study ended at four days, with both the pollen-fed groups (Bt and
non-Bt) showing significant failure to gain weight compared to the control
group fed on pollen-less leaves.

There was no information presented concerning ultimate survival of any of
the larvae, so I do not know whether both Bt and non-Bt pollen treatment
reduced fitness to zero (i.e. no information about whether the individual
larvae were unable to develop to reproductive maturity and successfully
reproduce).  Without seeing data relevant to the survival and reproduction
of all the groups, I cannot accept the published conclusion that Bt pollen
is toxic to Monarch larvae, as it also seems possible that they died of
starvation due to reduced feeding.  All the non-tachinid-infested Monarch
larvae I have raised (since about 1971) have taken ten days from egg to
chrysalis, and it seems likely that significantly reduced feeding for four
of these ten days would have an impact on health and fitness.  Any
conclusions drawn from the data that were actually presented must account
for the significantly reduced feeding (and failure to gain weight at a
normal rate) in both the pollen-fed groups, rather than ignoring the non-Bt
pollen data and assuming that death was due to antibiosis from Bt toxin.

Personally, I can neither accept nor reject the conclusions published by
Losey et al., without seeing more information.  I also cannot accept a
blanket statement that their findings are transferable to field conditions;
I have lived in Iowa since 1987, spend time most summers hunting for
Monarch eggs and larvae to raise, and have never yet seen a milkweed plant
whose leaves were dusted with corn pollen.  For one thing, there is this
funny ritual of de-tasseling that goes on every summer . . . oak pollen we
have in buckets-full, but not a lot of corn pollen wandering around the
landscape.  The ditches near cornfields are, however, often clear-cut, with
nothing much above four to six inches in height growing there.  Otherwise
the ditches mostly contain Pastinaca sativa.  Things may be different in
the Finger Lakes region of NY--I have not lived there since I got my B.S.
in entomology from Cornell in 1978, so I can't say what conditions prevail
in cornfields there these days.  But here in Iowa I just don't see much
milkweed near cornfields and not much corn pollen lying around anywhere.

Just my $0.02 worth, and certainly open to critique from people who have
more information or more up-to-date information!

In Stride,
Martha Rosett Lutz
a.k.a. the old lady sprinter in Iowa



 
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