What good is the green drone comb for mite control...

[paulh]

...when they fill it with honey?

I've intalled one Pierco frame in each colony, upper deep, 2nd of 3rd frame in.  Maybe it needs to be in closer to the center?

[fermentedhiker]

I'd check where they are putting drone cells within in your broodnest, that'll give you an idea of where your girls want it.  If you don't have many drone cells then it's irrelevant where you put it.  Backfilling drone comb with honey isn't unusual as fall approaches though, so it might just be a timing thing.

[Robo]

Backfilling drone comb with honey isn't unusual as fall approaches though, so it might just be a timing thing.

Adam is right.   Any drone frames I still have in my hives are now mostly filled with honey.  They used them to raise drones in the spring and through early summer,  but have since filled them with honey.  Perhaps as a method to reduce the queen from laying drones.