Hi Ghislain,

Re the Suchail study that you cited, here are some notes that I wrote:

Suchail fed imidacloprid and some of its metabolites to bees in syrup for
10 days (chronic exposure).  Her conclusions were stunningly surprising
(her term):  her results indicated that with chronic exposure, imidacloprid
and its metabolites were toxic to bees at levels 60-100,000 times lower
than that reported by others in acute intoxication studies!

Those figures proved to be anomalies, though, and have not been replicated
by other researchers (Schmuck 2004).  So we must ask ourselves, how could
Suchail have found a level of toxicity so far out of line compared to the
results of other researchers?

Unfortunately, the paper is not readily available on the web, so despite
being unquestioningly referred to by nearly every anti-neonic paper and
blog, I suspect that many have actually only read the abstract.   I’ve
personally spent some time going over the paper, and completely agree with
the authors that their results were not only surprising, but completely
implausible!

So let’s look at her actual methodology, which brings up a few questions:

1.       To start with, Suchail used older bees rather than younger bees
from the brood combs (these bees would not only be nearer to natural death,
but also lacking in protein reserves).

2.       She also made the questionable decision to take all the bees for
all “replicates” from only one colony, instead replicating the experiments
with bees from multiple colonies, which may differ in health and
susceptibility to the toxin.

3.       She apparently did not check the bees for nosema or other
infections.

4.        She then stressed the bees by both treating them with CO2 (which
can shorten lifespan) and then holding during the trials in an incubator at
a relatively cool temperature (dropping as low as 74°F) which can increase
both bee stress and pesticide toxicity.

5.        Suchail did not show the mortality curves for the control
(untreated) bees, although she says that “mortality of the control did not
exceed 15%” over the 10-day trial (I typically see close to zero mortality
in 10 days).  The control curve should have been shown.

6.       In order to make sure that a toxicological experiment is actually
measuring a “real” effect of the treatment, one often adds a “positive
control” with a known toxin (usu. Dimethoate).  Since Suchail didn’t do
this, it is difficult to draw conclusions from her data whether there was
any actual toxic effect from any of her treatments (see below)!

7.       I’m then not sure about her “replications,” especially since she
states that there were no deviations from the means, inferring that exactly
the same number of bees died each day in all three cages in each treatment
group.  It’s rather incredulous to see zero deviation in trials run in
triplicate!

8.       Suchail also added an inexcusable variable—dimethyl sulfoxide
(DMSO).  DMSO is a nontoxic solvent that is used to penetrate biological
membranes.  It is used as a drug delivery enhancer to carry compounds
through skin or other membranes without damaging them.  It increases the
rate of absorption of pesticides through the skin to the extent that a
toxicolologist that I questioned told me, “In our formulation work, we stay
away from using DMSO due to its high adjuvancy and penetration enhancement
which is a danger to the worker or researcher. If you are not careful to
protect yourself, you would end up bringing the toxicant into your body
through dermal penetration.”  Note that a study by Suchail in 2004, she
found that imidacloprid is not normally well absorbed through the gut
wall.  DMSO is not used in field applications of imidacloprid, so for
Suchail to add it to the test syrup seriously undermines the relevance of
her study in reflecting the normal absorption of the pesticide. This fact
alone is enough to make a case for discounting the results of Suchail’s
experiment.
-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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