This method is not the same as cutting away drone comb a few times in spring and early summer. The basic principle of this drone comb method in a narrower sense is to catch mites with drone brood in a broodless colony. In such a situation, drone brood is even more attractive to Varroa, up to 12 times more than worker brood. Around the turn of the century, this method was experimented with and was also published about with some regularity. However, the method is not yet so easy to implement in practice.
Drone brood is infected on average 8 times more than worker brood, partly because of the longer pupal period. Drone brood is also attractive to mites almost two days before the cell is closed, while worker brood is only attractive 15 hours before closing. It is therefore a frequently used method to use the closed drone brood as a varroa mite trap. The growth of the mite population is considerably reduced in this way.
The principle
The essence of this drone comb method in a narrower sense is placing comb containing drone brood in a broodless colony. This is achieved by splitting a colony into a part containing the queen but nu brood and a queenless part. The drone comb introduced into the broodless part contains drone larvae that are almost ready to pupate. All mites are on the bees and are waiting for the first opportunity to reproduce. They will then also step en masse into the introduced drone brood.
This drone comb method captures many mites. Results varied from 79 to 94%, much higher than the 30-40% achieved with the ‘normal’ cutting of drone comb. The effectiveness depends only slightly on the size of the frame used. It only needs to contain 100 drone cells with open brood.
How does the method work?
Step 0: Preparation of the division
When the colony has become strong enough in the spring, we divide it into two parts: one part without brood with the queen and another part with all the brood but without the queen.
A frame with drone comb is now hung in the colony or an empty frame, preferably in position 2 or 9, in such a way that this empty frame is drawn up with drone comb. If we work with two brood chambers and do not want to look for or cannot find the queen, we can place a second queen excluder (the first is located between the two brood chambers and the honey chamber) between the two brood chambers. We give each brood box in the brood nest a frame with drone comb. After a week, it is clear from the drone comb that has been laid in which box the queen is.
Step 1 – day 1: Making the split
After a week we will make the broodless split. On the bottom board we place a new box, filled with foundation. Then we shake all the bees with the queen out of the brood box with the frame containing drone comb (#1) from the frames into this new box. The drone comb is placed in the middle of the new box. On top of this come a queen excluder and the honey super with the bees in it. The split must be well provioned: two frames completely filled with food on the sides of the bottom box are needed.
The queenless part, containing all the brood, is now placed in a different place in the apiary or on top of the split, provided with a new bottom and a new cover. We remove the frame with the drone comb that was not drawn, which we keep for later use. Any empty space on the side can be filled with a closing block. It is advisable to reduce the flight entrance of the queenless part in the beginning to prevent possible robbery. If we opt for a later reunion of the two parts, we can use a Snelgrovebord instead of a new bottom board. See the page about this.
Step 2 – day 11-14: Finishing the treatment of the split
On day 11-14 after making the split, when the cells on the drone comb are sealed, we remove this comb (#1) from the split. This effectively concludes the treatment of the split. This has to be so, because new brood will soon appear in the split, so that the exclusivity of the drone brood that we are aiming for is over. The split now only serves to obtain drone combs contaning larvae. We then immediately hang a new frame with drone comb in the split: #2. This is at the greatest challenge of the method, because how to persuade the queen to lay drone eggs on this comb, while the split is not actually ready for it yet?
If we now allow the queen cells that have appeared in the broodless part to emerge, the brood-free period until the young queen starts laying is too short for an effective treatment. When giving drone comb #3, there may already be capped brood from the young queen. But we can gain some time by breaking the queen cells on day 10 after the division of the colony. At the same time, queen cups containing one-day old larvae from a selected colony are introduced.
Step 3 – day 18: First treatment of the queenless part
On day 18 after making the queenright split, drone comb #2 moves from the split to the queenless part. The split immediately receives the next drone comb to produce drone larvae: #3. We can repeat this system until the young queen has started laying, after a month or so. As mentioned, we can gain some time by breaking the queen cells once. This allows us to introduce one extra drone comb.
Step 4 – day 25: Second treatment of queenless part
The now capped drone comb #2 is removed from the queenless part and destroyed. In its place is introduced drone comb #3, which has been produced by the queen in the split. At the same time we check whether the young queen in the main colony has already started laying. If this is already the case, we will only find open brood. We remove the latter and replace it with drone comb #3. We have to remove the comb with open brood because otherwise the drone comb is no longer the only brood that the mites can enter. We can give the frame(s) with open brood to the split for strengthening this part. If we have broken away the queen cells in the queenless part on day 11, we will not have this problem.
Step 5 – day 32: Closing the brood layer treatment
The capped drone comb #3 can now be removed from the main colony. This also concludes the treatment of the main colony. We can now decide what we want to do with both parts of the colony: reunite them or set them up separately to expand the number of colonies.
Summary
A fundamental drawcack of the method is that the queenright splits are often too weak to produce drone brood, because they are not yet ready for it in their development. It does help somewhat if you give drone foundation instead of letting the split draw up comb itself. Furthermore, it is of the utmost importance to make the flyer as strong as possible.
Why don’t we hear anything more about this method? Because of the above-mentioned problem, and also because the method is quite labour-intensive, I suspect. Nevertheless, it is an attractive idea that we can reduce the Varroa population enormously with biotechnical measures.
The method is a delicate matter. If we wait too long, the drone brood will hatch, and that is precisely not the intention. Furthermore, a considerable number of actions are required, and that does not fit into everyone’s schedule and priorities.
Drawing out and covering those large areas with drone brood is also very taxing for the spli. These areas are actually a bit on the large side, which is not absolutely necessary. That is why we can advantageously use smaller pieces of drone comb, which we then place in a small wooden frame that is separated from the worker brood by a slat. The downside of this is that this frame with pieces of drone brood then has to be cut out and transferred each time.