... and no, I haven't got a mesh floor, but a solid wooden one. ...
Quite apart from the year-round function of providing a one-way Varroa exit route, a mesh floor with removable tray beneath provides a means of checking the level of infestation at any time AND monitoring the effect of any treatment(s).
You should be able to fit mesh floors to your existing hives - its only the floor that should need to be changed.
Long term and short term, its the way to go to monitor the level of the problem (certainly below the critical levels where DWV becomes obvious).
A few years ago, chemical (pyrethroid) pesticides (like Apistan) were the preferred means of routine control treatment.
The result of routine use was that the mite developed resistance in those areas where these chemicals were regularly used.
I'd suggest that your priority is to find out what the local situation in your area currently is.
If your local mites ARE showing resistance, such treatments would be a waste of time, money and hope.
But if they are not resistant, you might consider that route as your first attack, but ONLY while/because you have a known major problem. After that, for routine management of a low-level problem, you should try to avoid using these chemical pesticides, and just use "Integrated Pest Management" with Thymol-based products (like Apiguard and Apilife Var) to keep the problem down to a level that the bees can cope with.
The less widely the heavy-duty pesticide chemicals are used, the more potent they are when they are really needed. The resistance dies back in the Varroa population when/where their use is suspended for a few years.
But right now, it sounds like your bees need all the help they can get.
The weaker that the mite makes the colony , the less chance of the colony surviving the winter.
That's the advice that this newb took away from a visit to an obvious DWV colony with a Seasonal Bee Inspector last weekend.
That infestation was sufficiently heavy that some of the 'sealed brood' had actually been
partially opened (I was told) by the bees, because of the mites. Do you have that Graham?
Tom - obviously another person there who has picked up the erroneous info about acarine and DWV as posted on another thread a good while back.
