Great discussion guys!

Dr. Mullin has been investigating the organosilicones for some years, and
Julia Fine did great work in reviewing Calif Pesticide Use Reports.  I
share their concern about the organosilicones.  That said, Charlie makes
good points.

If an almond grower sprays at night (as many do, in order to protect bees),
there would be little expected exposure to the bees, since the bees
typically remove all the pollen from the blossoms during the day.

The arbitrary concentration that Fine used to feed the larvae is just
that--extremely arbitrary.  In the first place, the label for Sylgard 309
only allows for an application rate of 1/4 of the 1% concentration
suggested in Fine's paper (up to 3/8ths the concentration" if maximum
rainfastness is desired."  So although it is desirable to test a product at
an elevated level in order to quantify the NOAEL, the concentration tested
may have well been well above a field-realistic dose.

That said, it still did not appear to have a significant adverse effect
upon the larvae when fed directly to them.  Nor did Reed Johnson find that
it increased the toxicity of an IGR/fungicide mix.

One must of course be cautious about accepting the conclusions of any study
that involves feeding a chemical to larvae, without first testing to see
whether that chemical occurs in the jelly produced by the nurses.

This is certainly not to say that the penetrating properties of
organosilicones don't have adverse effects upon bees.  I'd prefer to see
more semi-field or field trials.


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

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