there may well be a correlation between cell size and varroa breeding
habits.two years ago I quit putting foundation in my brood boxes and the
brood boxes which had foundation had brood comb several years old thus
reducing cell size.when inspecting hives for mites I would select a
section of sealed brood of appr. 4 square inches and removing the
caps,pulled larvae from the cells with tweezers to check for mites and
rarely found any mites at all.however,drone cells occasionally would
contain 3-4 mites in anywhere from 10% to 40% of cells inspected.those
interested may try using smaller celled foumdation in brood boxes and
standard foundation in supers or flatten cell impressions of brood box
foundation and allow the bees to build cells of their own design.I have
found in removing old comb if at least 1" of comb is left at the top of
the frame the bees will build new comb in the proper orientation to the
frames thus cutting foundation expenses for brood chambers.

                                                curtis ,texas coast