Reduce varroa mites by culling honey bee drones
Drone trapping is a method of reducing the number of Varroa mites in a hive that is based on the mite’s life cycle and preference for drone brood. Mites can sense the presence of drone brood—probably by smell. They prefer to lay eggs in drone brood because they can raise more mites per cell than they can in worker brood.
The mite life cycle
It works like this. A female mite enters a brood cell 1 to 2 days before it is capped. About 60 hours later, she starts to lay her eggs at a rate of one egg every 24 to 30 hours. The mite eggs take somewhere from 3-9 days to mature, depending on their sex. Whereas worker brood remains capped for about 12 days, drone brood remains capped for 15 days. The difference in timing means that an average worker brood cell will yield 1.7 mites, but an average drone brood cell will yield 2.4 mites. According to the Dyce Laboratory for Honey Bee Studies at Cornell University, mites are found 2-30 times more often in drone brood than in worker brood.
If you are keeping bees in a top-bar hive, you can simply cut away portions of the comb that are filled with drone brood. The drones are often found at the perimeter of the comb and, if you’re careful not to apply lateral pressure to the comb, you can just cut away the portion you don’t want.
Drone frames keep the drones together
In Langstroth-style equipment drone frames are used to entice the bees to build the majority of the colony’s drone comb in one place. Once the drone larvae are capped, the beekeeper can remove these cells and destroy them. In so doing he removes a large proportion of the total mite population. By using two drone traps per hive, and cutting out the drone larvae once a month/frame, mite populations can be drastically reduced. I recommend putting one in the #3 position. Two weeks later put a second one in the #8 position. Remove and replace each one every four weeks (You end up cleaning one frame every two weeks.) If you have double or triple brood boxes, use two frames per brood box.
Once the brood is capped it can be cut away, or the entire frame be frozen overnight and returned to the hive the next day. Freezing kills both the brood and the mites. The comb can then be cleaned using the pressure of a garden hose, or the cappings can be scratched and the frame returned to the hive where the bees will remove the dead. Or, if you like, you can let the local birds pick out the brood for a snack.
Timing is everything
There is one extremely important point to remember if you decide to try drone trapping. If you don’t remove drone frames before the brood hatches, you will be raising bumper crops of both drones and mites. If you are going to use this method, you need to keep up with it.
Different types of frames can be used for trapping drones. Plastic frames embossed with drone-sized cells are available for purchase and work almost flawlessly. Alternatively, beekeepers can make simple frames that work equally well.
Randy Oliver’s drone-trapping frame
My favorite drone-trapping frame is the one designed by Randy Oliver http://scientificbeekeeping.com. This frame is easy to build and it is much easier to empty than the plastic frames. I just cut out the bottom portion and feed it to my chickens. I cut out the top portion and use it for comb honey. I don’t have to worry about freezing and cleaning frames—which is both messy and time-consuming—and I don’t have to put a lot of dead stuff back in the hive, which I find unappealing.
I build my frames exactly as Randy describes except I use thin wax foundation in the top portion. Either plastic or wax works fine, but since I have a penchant for comb honey I prefer the wax. I buy extra top bars and shorten them, just as he does, insert the foundation on top, and I even paint the tops green so I can find the frames easily.
For a much more detailed explanation, you can read Randy’s original text at http://bit.ly/97ekd7. The pictures below, and more, can be seen on his site.