On 25-Apr-12, at 4:23 AM, Chris Slade wrote:

>
>  The impression is given that a chemical is safe after the expiry  
> of its half life and this may, in some cases, not be so.
>
Hi Chris and all

I think that the number of 'half-lifes' before the chemical is safe  
is the important statement.  Seven 'half-lifes' are needed to decay  
to below 1%.  With imidicloprid the half life is 3 hours to 444 days  
depending on where it is found, water, clay, sand, etc, and who is  
talking.  I believe, like Stan, that retreating the same area again  
before the chemical has depleted itself complicates the issue further.

Bob Darrell
Caledon Ontario
Canada
44N80W

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