A believable side by side study would involve a number of hives, twenty or thirty, where half were treated in some way and the others were not. Simple. Then, the hives could be sampled for mites at the end of the season, or you could simply count how many died. If the treament hives had a better survival rate, then you might be on to something. Did Bush do this?
Trouble is, most people just do whatever it is to all the hives and then they can't know whether it is having the effect they want or the results are due to something else they did, or don't even know about. Like, non-virulent mites. Or maybe the mites have a predator that's taking them down. WIthout adequate controls, your work means nothing, not a darn thing.