The message <001801c29445$2a21d5f0$2ed3ad8e@HAL> from Donald Aitken <[log in to unmask]> contains these words: > From: "James J. Grefig" > > While not a chemist nor a biologist it seems to me that the mites that > > survive in a hive that is over wintered with Apistan will be the mites > > that are resistant (or most resistant) to fluvalinate. As the survivors > > breed they will pass on their resistant genes. Is this overly simplistic? > This does seem obvious. However, if you treat as per the label, the > survivors will also be the ones that are resistant and will pass on their > resistant genes. I don't see why leaving the strips on over winter would > make any difference whatsoever in the development of resistance. We need to get back to basics on this and ask a few fundamental questions. When fluvalinate was first introduced for the control of varroa, it was only in the region of 96% effective. What of the other 4%? Did they already have a tolerance (I prefer this to `resistance') to fluvalinate or was it quite simply that 4% of the bees in the hive did not come into contact with the Apistan strips? If 4% of the mites already had a tolerance to fluvalinate, then they would survive to breed - no matter how long the Apistan strips were left in the hive. However, if the 4% of mites remaining had survived because they simply had not come into contact with the fluvalinate, then their descendants would remain susceptible and a 96% kill could be expected every year - unless we train them to become tolerant by leaving in the Apistan strips longer than recommended. Apistan strips release fluvalinate in reducing amounts over time as the active ingredient is used up and eventually the amount of fluvalinate released will be insufficient to kill the mites and they will become tolerant to it. I am fortunate to live in a part of the UK which is still free of the mite and we have had 10 years in which to prepare our defences. When the mite arrives (as it inevitably must), I doubt very much that Bayvarol or Apistan will feature in our control measures. I have been adding copper gluconate to syrup for the last two years as a prophylactic and will probably continue to use this together with a package of other more natural control measures when the mite arrives. Phil. (Highlands of Scotland)