>Reducing the size of the cell (hence the bee size also), makes the cell size less desirable for the mite, and the life cycle of the bee larvae less of a "fit" for the varroa larvae.
>Is this true, as it is understood?
>If so, is there any reason that would couldn't modify the cell size below 4.9mm? Say 4.6mm?
For what purpose? Naturally they run down as low as 4.6mm in the core of the brood nest, but that is more of an exception than a rule. If you let them build what they want it will be a variety of sizes with most of the worker brood in cells between about 5.1mm and 4.9mm. But a whole hive of 4.6mm would not be natural. A whole hive of 4.9mm is a compromise that is still not natural, but sufficient to handle the Varroa and, if you want all the same size cells, seems to be about the right size.
>Has anyone tried this?
You'd have to find a 4.6mm mill. I haven't seen any. 4.8mm is as small as I've seen for sale anywhere and that's for African bees.
>I know there is some controversy surrounding this issue, but it does seem logical that if you modify the bee larvae cycle and make it incompatible with the Varroa larvae cycle, you should be able to better control the mite.
But, in the experience of those who have done it, 4.9mm is quite sufficient to keep the Varroa from being a problem. Getting them down to 4.6mm would be more work, and if all the cells were that size, you'd have unnaturally small bees, instead of unnaturally large bees. :)