Following a link from a post in the top bar section of the bee source forum, I came accross some very insightful information from Michael Bush.  I'm keen to explore all of the information he provides including the powerpoint presentation he shares on the site.  The very interesting and valuable point he makes on the top of his main bee page is this:

Most of us beekeepers are fighting with the Varroa mites. I'm happy to say my biggest problems are things like trying to get nucs through the winter and coming up with hives that won't hurt my back from lifting or better ways to feed the bees.

This change from fighting the mites is mostly because I've gone to natural sized cells. In case you weren't aware, and I wasn't for a long time, the foundation in common usage results in much larger bees than what you would find in a natural hive. I've measured sections of natural worker brood comb that are 4.6mm in diameter. The 4.6mm comb pictured below was drawn by a hive of commercial Carniolans. What most people use for worker brood is foundation that is 5.4mm in diameter. If you translate that into three dimensions, instead of one, that produces a bee that is about half again as large as is natural. By letting the bees build natural sized cells, I have virtually eliminated my Varroa and Tracheal mite problems. One cause of this is shorter capping times by one day and shorter post capping times by one day. This means less Varroa get into the cells and less Varroa reproduce in the cells. I have mostly done this either with wax coated PermaComb (fully drawn plastic comb) or self drawn comb on foundationless frames or frames with blank starter strips. 4.9mm foundation is available from Dadant and Sons and from Brushy Mt. This size(4.9mm) has been found sufficient to resolve the mite problems.

This is certainly in keeping with what we have experienced with the Back Yard Hive.  Let the bees do things as close as possible to the natural order, and they are much more able to protect themselves against infestation and disease. Nice to see such a scientific and carefully monitored approach which explains some of the mechanisms behind why a more organic process holds a promise for dealing with the mite issue.  Thanks Michael!

Visit Michael's site to learn more...