>I placed a bottom tray in my hive and after 48 hours there was a mite count of about 60-75.
In 24 hours that averages 30-37 mites.
> I believe that this is high enough for treatment.
Maybe. It's on the border.
> Should I treat these bees?
> and if so what is everyone using?
I would use oxalic acid vapor if it was me. Depending on the dimensions of your TBH you could either drill a hole in the front (or if you have one already use that) and use the pipe evaporator. Or put a box on top with a gap between the bars. Whatever works with what you have.
> Apistan Strips.... does this contaminate any drawn comb?
Absolutely, they will containate the comb.
> Also what is the cut off date for treatment?
It depends on your climate. Ideally you'd use it after brood rearing stops and pull it before the cold sets in too much to be opening the hive. Here that would be middle October and pull it out when the instrutions say. You may have to open when it's cold and just pull the strips without messing too much with the hive. Since it's a top bar hive it should be easy enough to pull the strips from between the bars without exposing the bees to the cold.
>Other questions is on Top Bar Hives. I really would like to move towards these hives - mainly because of ease and affordability. Is it possible next spring to convert my current two hives from Lanstroth to TBH - and if so what is the easiest?
It's much easier to go the other way. It's easy enough to cut combs out and tie them into frames. It's not easy to cut combs and put them onto top bars. Of course you can do a shaken swarm and put them in a top bar hive. You can build a top bar hive that is langstroth dimensions and put the frames in it with some top bars. Most of mine are long medium Langstroth dimensions that will take medium frames or top bars.
It's worth having some "swarm catching frames" that fit your top bar hive. Just adjust the dimensions:http://www.beesource.com/plans/swarmfrm.pdfhttp://www.beesource.com/plans/scf/index.htm
With these, you can just cut the brood combs out of the Langstroth and put them in the top bar. You can also salvage crooked combs and fallen combs and do cutouts from trees and houses and put them in your top bar hive.