On 29-Nov-06, at 11:35 PM, Peter Dillon wrote:

> Resistance (tolerance) to the presence of Oxalic acid by Varroa  
> mites should be an interesting phenomena to study.

Hi Peter and all

While I believe Oxalic as well as Formic acids have been studied(in  
Canada and Europe where they are legal) I don't know the answer.  The  
question of 'how does Oxalic damage the mites?' was asked at our  
recent meeting of the Dufferin Beekeepers Assoc.

The instructions for using Oxalic on varroa mites, as published by  
the Canadian Honey Council, state that it must be done late in the  
fall when there is no brood present, that it should not be used more  
than once per season and it should be used in support of another  
approved treatment(ie formic, apistan) as a final 'cleanup' treatment

Resistance to various chemicals is documented, but I have never seen  
any reports of resistance to Formic acid or Oxalic.

Bob Darrell
Caledon Ontario
Canada
80W44N

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