Ask a Master Beekeeper - Swarming

Many questions this month asked about how to manage swarming. There isn’t one single method that works best. It requires a changing and flexible approach over the course of several months.

One method that isn’t as well-known as it should be is “Opening the Sides of the Brood Nest” or OSBN.

This is a novel anti-swarming technique that is put in place in the last month before your swarm season. Its purpose is to prompt an early start to significant wax building, as well as provide extra drawn-comb capacity near the brood nest. It can also be used as part of a mite control strategy.

In warmer weather, foundation is sometimes inserted into the brood nest to “open it up” and get the foundation drawn very quickly. Bees don’t like having gaps in the middle of their brood nest, so they will rapidly remedy that.

In late spring, however, dropping frames of foundation into the center of the brood nest might cause the adjacent brood frames to become chilled and it disturbs the integrity of the brood nest at a critical time of year.

On the other hand, opening only the sides of the brood nest places the gaps at the outer edge and leaves the core of the nest intact, while still prompting a similar, early start to wax-making.

It does this because the new frames are not full frames of foundation. The frames contain only a partial sheet in the center, with open voids created on either side. Those open spaces get the bees working quickly to fill them. The bees will draw out the foundation section to worker-sized cells, and the open areas as larger, drone-sized cells. Any combination of foundation sections and open areas works, as long as there is at least 25% of the frame area left open.

The presence of this undrawn foundation with its adjacent empty areas so close to the brood nest provokes the bees to begin drawing comb weeks earlier than they would normally start. Wax making converts a larger share of the early nectar into fuel for the wax makers, reducing some of the brood next congestion. The drone comb sections of the OSBN frames can also be culled as part of a mite control program.

Wax and comb building are activities that appear to slow down or deter the development of swarm preparations.

Here’s how to use this method

Take sheets of plastic foundation and score and then snap off about 1/3 of the sheet at one end. Save the off-cuts to be combined with another 1/3 sheet to make, collectively, another 2/3 sheet panel. Insert a 2/3 sheet piece in the center of the frame (you’ll need grooved/grooved style frames) and fix it in place by smushing a little blob of propolis against both the lower corners, along the bottom edge of the frame. A little dab will do ya! You will need at least two of these frames per active brood box. It’s helpful to also mark the top of the frame distinctively. I use OSBN and the year to help me distinguish these frames from the others when looking at their tops.

About three or four weeks before your swarm season, locate the edges of the brood nest. Remove one drawn frame from each side of the hive, outboard of the brood nest area. Choose one that is not the sole pollen or honey frame on that side.

Slide the frames beyond the edges of the brood area outward and slot in the two OSBN partial-foundation frames, one on each side of active brood frames.

The bees are provoked by the sudden appearance of foundationless areas at the edges of their brood nest to begin wax making to draw drone comb in the voids. They will cover the center section with worker cells for the queen to lay in.

This is a flexible technique. If the weather is chilly, you can do one side at a time, coming back to the second frame a week later. If you have brood in more than one box, you can add additional OSBN frames to the sides of all the brood nest areas.

The frames removed to make room for the OSBN frames may be culled, or used to replace other frames slated for culling, or they can be used to populate an extra brood expansion area in a third brood box.

Getting the bees to initiate extra-early wax building is a moderately strong anti-swarming tactic. To keep them building comb is important, so once these frames are drawn, add another pair of OSBN frames outside of the first ones. Even while the weather is still cool, the voids in the frame are goads to the bees to fill them with new wax. As the weather settles, you can use a full sheet of foundation on one of the sides, instead of two partial sheets. The goal is to initiate and keep comb-building happening at the edges of all the brood areas, at all times, right on through the swarm period.

Since these OSBN partial-foundation frames tend to be slightly fatter at the ends than the orderly worker cell sections in the middle, they are not ideal combs. After the swarm season has passed, work them outward from the edges of the brood nest and either use them for storing winter honey, or pull the frame, scrape the wax off, and prepare them for duty the following spring.

Using the OSBN frames for drone culling

If you wish to use the side sections with the drone-cells as part of a drone culling mite control strategy, mark the top of the frame with a pull-by date that's three weeks out. Remove the frame and slice out the drone sections on each end. Mark a new culling date that’s three weeks out for the next removal.

Varroa destructor mites prefer drone cells for reproduction. Cutting out sections of drone comb that are capped, but not emerged, removes any varroa in the cells from the hives. Your only requirement is to remove the frames on or by the pull-by date. Otherwise you risk increasing the mites in the hive. Drone culling is a useful strategy for harm reduction early in the season. As the rate of drone production falls off after mid-summer, drone culling becomes less effective.

The OSBN technique ought to be more well-known

1. It's easy and inexpensive to manage.
2. It is an effective part of late spring swarm suppression.
3. It helps beekeepers, with little or no extra drawn comb in their first years, manage swarm season more easily.
4. It provides a low-key, non-chemical way to do a little varroa mite suppression.

The method was first described by Australian beekeeper, Matt Davey. To read more about the history of OSBN, click here. The partial sheet modification was suggested by Laurie Miller, a queen breeder in Washington state. Why not see how it works for you?