Hello Bob & All,

Bob's reply to my post raised one science issue that I didn't cover 
previously.      

>Can you assure beekeepers that Midwest farmers planting imidacloprid-
treated seed year after year in the same field without rotation are not 
raising the risk levels as to the concentrations of the neonicotinoids in 
the plant?

Very good question and one that has been extensively researched.  It is 
discussed in the two review papers I cited in my last post: Schmuck et al. 
2001 (Pest Manag Sci 57:225-238) and  Maus et al. 2003 (Bulletin of 
Insectology 56:51-58).   Some residues can remain in the soil beyond 
harvest and may be present when a succeeding crop is planted.  But here's 
the key thing to keep in mind.  Most of this residue is not bioavailable to 
plants because it becomes tightly bound to soil particles.  A chemist in a 
laboratory can extract it from a soil sample using a hot methanol wash, but 
you can't get much of it out with water which is of course the solvent used 
by plants to "extract" nutrients from the soil.  The bottom line is the 
residues in plants won't be appreciably greater after 7 or even 70 years of 
continuous use than they were the first year. 

I'm not going to engage in an iterative point-counterpoint debate of the 
non-science issues.  My intent in posting here is to provide information 
that otherwise hasn't been brought out.  BEE-L readers can read the 
referenced documents for themselves and make up their own minds.  

Best regards,

Dave Fischer

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