Am I now back on a thread that involves honey bees?  I was surprised and
amused yesterday by one thread in which I was not clear whether I had found
a fairy tale discussion group, or an example of sublethal ethanol
neurotoxicity in the human brain.

Thank you for these references Christina!  The actual death of neurons is
something that I had not previously considered.

The de Almeid Rossi study was expertly conducted--a sterling example of an
excellent bee toxicity investigation.  For those who haven't taken the time
to review it (open access), they determined the acute oral toxicity of
imidacloprid (IMD) for Africanized honey bees to be about 80 nanograms/bee.

They then found neuron death in the mushroom bodies of the brain after 3
day's exposure at 8 ng/bee (no observable effect at lesser doses or shorter
times).  They found neuron death in the optic lobes at chronic exposures of
as low as 0.8 ng/bee in as little as one day, but certainly after 3 or more
days of chronic exposure.

The above sorts of figures help us to put the effects of bee exposure to
neonics into perspective.  The 8ng dose is about the same that Dr. Lu fed
to his colonies for one-day exposures once a week.  We've already
determined that that dosage if far above what bees would likely be exposed
to from seed-treated crops.  Indeed, even the 0.8 ng dose is above what
bees would typically be exposed to.  The take home message to me is that I
wouldn't expect significant neuron death under field conditions unless bees
foraged solely on treated nectar and pollen for an extended period of time.

On the other hand, with foliar applications, tree injections, or ground
drenches, bees could easily be exposed to doses that caused neuron death.

Acute toxicity to neurotoxins typically involves involuntary muscle
contraction, which exhausts the bee.  Chronic effects, such as immune
suppression or neuron death are also of concern.  These findings suggest
that our discussion of "irreversibility" of binding is rather moot.
Neuronal death is, for all intents and purposes, irreversible.  This
clarification of our points of discussion is of great benefit, and I thank
you Christina for bringing it up.

I haven't yet had time to review the other references, but hope to post
again after I have.

--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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