> I am puzzled.  If IMD accumulates in the soil (half life of more than a 
> year) and this is the problem, then why is there not a problem, e.g. in 
> California, now?  Have they stopped using it?  Has it broken down?

This is not "the" problem.  The major problem for most beekeepers is
flowering crops treated with imidacloprid, such as pumpkins.... But the
persistence has been a problem for me, with potatoes, but less so now
that most growers use set treatment rather than soil injection and so the
amount per hectare (and the residual the next year) is much less.  But
it a problem that Bob referred to when he said the orange groves will
continue to contain IMD even after treatment ends.

And similarly, when use on sunflowers in France was suspended, the next
year the sunflowers still contained similar amounts which was a problem
with some experiments and beekeepers said it was a reason that problems
did not immediately cease (in addition to the continued use of fipronil).

It does break down, and how quick depends on soil ph and the amount of
organic matter.  Please note that despite my polite and reasonable request
to David Fischer of Bayer Crop Science last fall on this list, he did NOT
post the study that they conducted on soil persistence on PEI (which cannot 
be accessed through our "access to information" because although it was 
submitted to the regulators it is "proprietary information".   Had the half 
life not been well over a year on PEI, I think he would have released it. 
Nor has he posted a reply to my question as to why they will not analyze the 
samples of bees, comb, pollen, nectar, honey, leaves and soil that were 
taken from canola fields and my hives now five years ago and are stored in a 
freezer.  The study was undertaken because the researchers did find residues 
in canola the year following soil injected potatoes.  They made much of the 
results the previous year which did not find significant residues in clover 
TWO years after potatoes,  but it seems to me they are afraid to look at 
this.

Stan

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