Anyone who is a beekeeper here is very familiar with 2 common pests: hive beetles and varroa mites. I’m going to focus on varroa mites for this post.
Varroa mites are very tiny external mites on bees – about 1.5 mm in size. They suck the hemolymph (“blood”) of the bees and causes them to become weak and prone to infection and illness.
There are many chemicals available to treat them, but we prefer to keep our hives chemical free, so we resort to natural methods. One way to do that is to use drone comb to capture the mites. Varroa mites prefer drone brood over worker brood. The drone cells are larger and the drone larvae live longer. Place a frame of drone comb into the hive and allow the bees to draw out the drone comb and cap it. Then you remove the frame and freeze it for at least 24 hours to kill off the mites. You also kill the drone brood, but it is a small sacrifice compared to being infested with varroa mites. After the comb is frozen, uncap the brood and place the frame back into the hive. The bees will clean out the dead mites and dead brood and repeat the process.
Here are some close up pictures I took of larvae we pulled out of the drone comb to show you what varroa mites look like.
Beelievable 
We heard a talk at London Beekeepers bee health day about using good husbandry techniques, like this, to help control varroa levels. Drone culling is also a good way to monitor levels of varroa infestation in the colony – although I always feel a bit sorry for the poor old drones.