Bee Culture, February 2011

Original title: Checkerboarding Reliability

Checkerboarding is a relatively new approach to swarm prevention. Although it has only been published for about 15 years, it defies the old adage that “swarming is inevitable.” This submittal is intended to substantiate or quantify the advertised reliability.

Implementation of the checkerboarding (CB) manipulation is disgustingly simple. The manipulation consists of removing alternate frames of honey from the top box and replacing those frames with empty comb suitable for rearing brood. Since there is no brood nest disturbance, it can be done in late winter before the brood nest expands into the top box of capped honey. After the initial manipulation, to sustain swarm prevention reliability, maintain empty comb at the top for the colony to grow into with brood nest expansion. If that sounds too simple to be effective, you are in good company. Almost nobody believes it would get the reliability that is inherent in the approach.

I and my bees live in a very swarm-prone location. Shorter and milder winters lead to better wintering. In late winter, continuous and overlapping field forage sources support build up. Most colonies, including those that winter in the lower 25% of overwintered cluster size are able to meet requirements to generate a reproductive swarm. When the T mite penetrated the area in 1990/91, we lost 8 of 10 hives over the winter. Ten local, feral swarm colonies were added to the two survivors during the ’91 season for a total of an even dozen going into the winter. All were treated with grease patties only. In the spring of ’92, seven swarms were collected. Some of those were over-sized swarms and were considered to be swarms that merged from more than one parent colony. Even if all were from a single parent colony, nearly 60% swarming from colonies in the early T mite period would beat the odds, for survival/swarming during that period.

The first test of CB was accomplished on an outyard of 12 colonies. That outyard was a particularly swarmy location. Fallow fields in the area were overgrown in fall forage sources such as goldenrod, small white aster, and beggar’s lice. Swarming was the norm for that location. Colonies in that outyard were wintered in two deeps and a shallow feed box at the top. Three frames of empty brood comb were substituted for frames of capped honey in both the upper deep and the shallow feed box on an every-other-frame basis above the brood nest in both boxes. The results were astounding. No swarms, and more surplus honey than we were accustomed to seeing from standard management.

Over a hundred hives were sold off in order to study the effects of CB in more detail – keeping 20 hives on 2 trailers of ten each. The internal activities of these 20 colonies were studied over an eight year period (took early retirement to have access in the short days of late winter). Details of the study of these 20 colonies yielded a description of the swarm process and nearly 100% swarm prevention. Two exceptions (colonies that swarmed) in two different years over eight years were the result of my failing to properly implement my own recommendations. The other six years yielded zero swarms on all twenty colonies. We feel that we can safely refer to a norm of zero swarms as “reliable.”

We believe that the improved reliability is based on timing the intervention in the colony reproduction (swarming) process. To discuss the timing, we need a brief description of the normal swarm process, without intervention. The basics:
  1. With the advent of field forage support, brood nest expansion gets underway.
  2. Brood nest expansion continues until the colony reaches their minimum capped honey reserve. The reserve is a hedge against field forage dearth during the early season and is only opened under emergency conditions. This point in the process is sometimes called “honey bound.”
  3. Having reached maximum, safe, brood nest expansion, brood nest reduction starts. As brood emerges in the expansion dome at the top, cells are filled with incoming nectar. The young bees reared at peak brood volume, without brood cell turnover, are available for establishment of the swarm in a new location.
  4. When the brood nest is sufficiently reduced, swarm queen cells are started. They have generated the right age mix of bees to support two viable colonies. The swarm will have plenty of wax makers to generate comb in a hurry.

We arbitrarily refer to the change from brood nest expansion to reduction (steps 2 and 3 above) as the beginning of “swarm preparations.” Any colony that generates a reproductive swarm will normally reduce the brood nest volume prior to committing to swarm by starting “swarm cells.” This change in direction of brood nest size occurs about a month prior to swarm issue. Locally, the colony reaches max brood nest size in early March and the swarm issues in early April.

If you have tried cutting out swarm cells to discourage swarming, you are aware that the colony committed to swarm is not easily deterred. They start over making new swarm cells promptly.

Evidence exists that the colony is also hard-headed once they start the swarm preparation phase of brood nest size reduction. An example is the reversed double deep with brood in both boxes. When the brood to the top bars in the lower is raised to the top by reversal, brood nest reduction starts over at the top. Although reversal added some delay in their process, it didn’t change their course of action.

“Getting ahead, and staying ahead” of the colony is the old adage applied by checkerboarding. The colony that was checkerboarded before they started brood nest reduction delays that action for another brood cycle of expansion.

Locally, knowing swarm preparation/ brood nest reduction normally starts in early March, we CB in the last two weeks of February. Swarm preparations do not start. Without starts, there are no completions.

We rest our case for timing being the major reason for the reliability of swarm prevention when checkerboarding.