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GAVIN RAMSAY <[log in to unmask]>
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Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Sun, 1 Apr 2012 15:53:37 +0100
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Hi Stan, Jerry and All

[this quote from the RFID thread, sorry .... ]

> about 6 ppb is what Cynthia Scott Dupree was finding in the Ontario study
> that was used to register imidacloprid as a seed treatment for canola.

I had said of the levels used in the Whitehorn bumble bee study (6 ppb, also 7 ppb in an earlier study): 'These values may be a little on the high side - but still conceiveable values for real-life field situations.'  You are right to question that Stan.  To add to the Canadian work, Marie-Pierre Chauzat and colleagues reported the levels of imidacloprid in oilseed rape (canola) in pollen collected in traps at bee hives in France.  49% of pollen samples had detectable imidacloprid and the values ranged from 1.1 to 5.7 ppb with a mean of 1.2 ppb.  The averages that they present in table 2 appear to be means of the positive samples (ie excluding zeros).  However they also recorded the metabolite 6-chloronicotinic acid (also toxic to bees) at 0.6 to 9.3 ppb in these samples.  So, 6 ppb is five times higher than the mean but close to some samples, and if you include metabolites then perhaps is a decent guess. 

My reading of the data they present on variation over time is that early on in the flowering season of autumn-sown ('winter') rape pollen has a higher load of imidacloprid that decreases as the the plants move into the later stages of flowering.

The Chauzat study: 

http://www.boerenlandvogels.nl/sites/default/files/Chauzat%20et%20al%202006_0.pdf

All of this is relevant to whether or not these uses are safe for bees or not.  I've been convinced that it was safe for honeybees (and am unmoved by the RFID study the other day that used high levels of neonicotinoids) but as far as I am concerned the jury is still out on the risks to bumble bees.  And it shouldn't be.  There should have been clarity before permission was given.

Jerry expressed the view that Whitehorn and colleagues should have measured the levels in their prepared samples as it is hard to get it right.  OK, but let's give them the benefit of the doubt for now.  Also:

> Please understand, this is a preliminary study,  or short research note;
> while it raises a new question, perhaps an  important one, it is a very 
> small and early study, not  the  mature paper that Science usually requires.
> It deserves publication,  but as a note, acknowleding its limitations, in a
> more appropriate  journal.

Whitehorn et al 2012 (the Science bumble bee paper we have been discussing):

25 colonies each treatment, commercial-type colonies fed experimentally indoors then allowed to forage freely (mostly non-arable land) to complete their life cycle.  Large and statistically significant depression of the production of sexual forms.  The paper is short but I don't think that it should be discounted because the data in this study is *better* than all the previous papers I have seen on the topic.  Whether or not it is a major step forward scientifically and deserving of publication in Science is something I will leave to others to decide.

Morandin and Winston 2003.

The same pattern seen in that there was a small depression in weight gain and a larger depression of the production of queens.  This was using 6 colonies per treatment.  The depression of queen production should have rung alarm bells, but it didn't.  The trend was there.  They saw a *five-fold* reduction in queens produced from imidacloprid (7 ppb) treated colonies but discounted it as important as their error bars in this 6-colony per treatment experiment overlapped.  See the figure here, remarkably similar to the pattern in the Whitehorn paper:

http://tinyurl.com/c7bgzdt

There is something which needs explanation or action.  The quote from the UK Bayer spokesman, replicated on here, that studies have to be conducted only in the open air isn't good enough IMHO.  Feeding artificially raised colonies in the lab then letting them forage openly seems like a good protocol to me.

It is a great pity that the Whitehorn paper is not available on Open Access.  Usually the way to see such papers is to ask the authors (they'll probably not thank me for reminding you of that!).

best wishes

Gavin

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