Bare with me …
I’m not keen on killing off drone brood as it can disrupt bee diversity and gene distribution and basically it is anti-social to your local Drone Congregation Area for your neighbours Queens mating’s - if all our “Neighbours” killed off the majority of their drones we all loose Bee Gene Diversity - not good for the bees
As a method of Varroa control it is not a viable process - in fact a study done in the UK linked to COLOS shows the most effective control of Varroa is actually 2 sublimation’s of oxalic acid at the time of broodlessness - when there is a 99% chance of killing off the varroa - done in a broodless time - unless you have a varroa factory, or you neighbour has, then treating for varroa only needs to carried out at broodless times - newly caught swarms, buying a box of bees and middle of winter.
But if you really felt inclined to cull drones as a part of IPM (Integrated Pest Management) then I have a suggestion…
Eating the surplus culled drones larvae, a very good source of protein, after you do a varroa count you can freeze the larvae for up to 10 months. If you really feel it necessary to cull drone brood - don’t waste it.
Would you kill a fish and not eat it? Would you breed cattle or sheep, kill it and not eat it? Then why waste a good source of protein?
2 articles below:-