Randy wrote:

Re bioaccumulation, contrary to the old organochlorines, which persisted in
> animal fat and were passed up the food chain, imidacloprid is quickly
> metabolized in bees, with a half life of about 4 hours.
>

Bioaccumulation is not the problem with bees, it is persistence in the
environment.  The half life of importance to that, is the half life in the
soil.  Also relevant is the soil adsorbtion coefficent.  The old
organochlorines (DDT is the most famous, half life 2-15 years, chlordane is
another, half life 4 years) were banned largely because of their
persistence in the environment.  They were replaced by the organophosphates
and the carbamates.  The organophosphates have half lives that are
generally measured in days (some of the most toxic are often the least
persistent).  I have previously posted a list of half lives compared with
neonicotinoids.

The manufacturers of neonicotinoids recognize the problem of
bioaccumulation in soil.  The last time that I looked at the label for the
imidacloprid product "Admire" it had a warning on it not to apply to the
same field in successive years.  Juanse should look at the label of the
product they are using on the high bush blueberries to see whether they can
legally spray it again next year.  And with tree crops, the persistence is
also well documented.  I have posted previously a forestry paper on multi
year pest control using soil injection, and among the submissions to the
EPA supporting the use of imidacloprid was a forestry submission from
Virginia, I believe, which stated it got control for six years ( I also
previously posted this, so I will not look up the reference).  This is the
problem with the oranges that Kirk began this thread about.

I also think that it is not necessarily the case that we have to compare
neonicotinoids with organophosphates.  They could also be replaced with
pyrethroids, rotenone, and biological insecticides (like BT).  All of them
have extremely short half lives.

Stan

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