A couple of other questions. Were there only two controls, or are the hives
that died all controls?
The controls got no treatment, at least that is my guess. Or did they? What
other preventative measures were used, if any? When was the sampling taken?
We know that mite drop occurs with the introduction of FGMO, so you will
get reduced mite count after an application.

If the others that died were not controls, then you have 20% mortality in
the group with the controls- both died- and 24% mortality in the other
apiary with no controls.

It is a little difficult to see just what is going on with the data
presented, other than FGMO works 75% of the time.

Bill T