Thank you Ernie for the good questions!

>Your comment about the cumulative effect of drinking beer

My comment was not about cumulative effect--I specifically said at one
sitting.  Drinking 135 beers at one sitting would be a toxic effect--of
both the alcohol and the water.

>The Dutch Toxicologist Tennekes has argued that Bayer’s own scientists
have pointed out that the damage done to the central nervous system by
imidacloprid is irreversible.

I've covered this at my website.  It was one scientist in an old obscure
Bayer journal who made that comment.  The word "damage" wasn't used.  The
*binding* was said to be irreversible, but I have been unable to find a
single other reference to the binding being irreversible.    I asked an
independent Univ of Calif expert on the neonics (Dr. John Casida) if it
were true.  He firmly said that it wasn't--the effects are reversible.

> Tennekes says somewhere in his writings that neonic exposure is
cumulative for bees

I've corresponded at length with Dr Tennekes, cc'ing the editors of the
major bee journals and the risk assessors at the EPA.  Tennekes was unable
to substantiate that claim.  TheDruckrey–Küpfmüller equation applies to
mutagenic or carcinogenic toxins that cause diseases like cancer, but is
apparently not applicable to pesticides in general.


> >I haven’t seen any serious attempt to by other scientists to follow up
> and prove or disprove Tennekes claims.


Others have, in a number of studies.  Tenneke's hypothesis doesn't hold
water.



> >Could it be that Lu et al were breeding imidacloprid resistant bees ?


"Breeding" requires propagation of selected stock.  Lu did not do that.
There would be no genetic selection for resistant bees, since the queen was
not replaced.


> >sub lethal doses as low as 0.04 ng per larva will affect the olfactory
>  associative behavior of the maturing adult larva to such an extent that it
> “may affect the survival condition of the entire colony, even though the
> larvae survive to adulthood”
>

I find this to be of concern, and would like to see a better experiment
run, since this one had a few issues.  In the first place, the larvae were
treated directly with IMD.  This does not happen in real life, since the
larvae are fed jelly by the nurses; jelly appears to be typically free of
pesticide residues.

Secondly, the researchers used DMSO to dissolve the IMD.  DMSO is not used
in neonic formulations since it is so dangerous, due to its ability to
increase absorption of the insecticide across membranes.  The authors did
not test to see whether DMSO increased IMD toxicity or absorption.

>A level of 0.04 ng per larva corresponds to 0.25 ppB imidacloprid
contamination of the pollen coming into the hive.

Since larvae are not typically fed pollen, the above calculation is
meaningless.

I'm not discounting that IMD may have a delayed associative learning effect
on bees.  It's just that the cited study had some problems, and would not
pass EPA requirements.  I'd like to see it repeated without the
shortcomings.

Ernie, I'm as interested in sublethal effects of pesticides as anyone.  I
was stunned by the recent finding by Cousins that the common herbicide
diquat affected bee larvae at parts per trillion levels! Size Changes in
Honey Bee Larvae Oenocytes Induced by Exposure to Paraquat at Very Low
Concentrations. PLoS ONE 8(5): e65693. doi:10.1371/journal.pone.0065693

I have no doubt that the effects of neonics, as well as those of other
insecticides, are harmful to bees.  Whether they are associated with CCD is
another matter. Only well-designed studies will answer that question.

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

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